Hi, I am new to this forum thing.. i wish i had known about it 6 years ago when I did the first build..
wondering if there is any information on putting the TS pistons under the NORD head to get the comp ratios down to accept 8-10psi supercharge..?
i hear that the TS rods are shorter, so I guess I have 2 options..
1, I use the short rods with the NORD pistons to get lower comp ratio or,
2, I use TS pistons and NORD rods.. Will the deck height of the piston with the NORD rod be inside the top of the sleeve at TDC?
Does anyone know off hand what the resulting comp ratios will be with either(or both)
Also, reading over Mike(Buzzed)'s twincharge install, he talks about 10548inlet cam with a 10520exh cam to reduce overlap and improve economy/fuel delivery and ultimately HP.. does anyone have any experience with this and is it as simple as putting the cam in, setting the clearances and away you go(i guess it should be the same as any cam install.. perhaps forget this question.. ) Has anyone done this with a forced induction application who can comment? a second opinion goes a long way.
I am currently running wasted spark ignition, custom plenum, wolf 3Dv4 and it is tuned for the last supercharger install (intercooled SC14).. i found the tune very difficult with lots of fuel and crazy timing to reduce detonation.. I was running 5.5psi.. tired engine but you would think this would help, not hinder.
Any help at all will be appreciated.
Check out this thread on the alfaBB, it has some discussion about using TS rods or pistons.
http://www.alfabb.com/bb/forums/engine-rebuilding/149621-alfa-75-twinspark-pistons-1984-116-2-0l-giulietta.html
Alan.
That thread looks familiar. ;)
My brother started that thread and has done some research on the compression ratio. You may have to pm him on the alfabb if you have further questions. He is running EFI on his Giulietta with multi throttles and sequential ignition, aswell as other custom parts.
Thanks Alan,
looks like the shorter rod is the way to go.. now to source them.. I might hit the calculator and see if i can confirm the compression ratio reduction before i part with my $$ though.
Any idea where i might find the info on the cam question?
Cheers, Dan
I have TS pistOns in my nord, haven't started the engine yet .
Sorry I would write more but I'm on my I phone at work. Ask me what you want to know I've researched this over the past 3 years.
Thanks StormX,
how was the deck height on the pistons? any protrusion? are you using the Nord rods or TS rods? have you calculated the expected comp ratio?
do the TS pistons and Nord pistons use the same size gudgeon pin(wrist pin)?
Cheers, Dan
Quote from: Blown116 on May 16, 2012, 02:59:13 PM
Hi, I am new to this forum thing.. i wish i had known about it 6 years ago when I did the first build..
wondering if there is any information on putting the TS pistons under the NORD head to get the comp ratios down to accept 8-10psi supercharge..?
i hear that the TS rods are shorter, so I guess I have 2 options..
1, I use the short rods with the NORD pistons to get lower comp ratio or,
2, I use TS pistons and NORD rods.. Will the deck height of the piston with the NORD rod be inside the top of the sleeve at TDC?
Does anyone know off hand what the resulting comp ratios will be with either(or both)
Also, reading over Mike(Buzzed)'s twincharge install, he talks about 10548inlet cam with a 10520exh cam to reduce overlap and improve economy/fuel delivery and ultimately HP.. does anyone have any experience with this and is it as simple as putting the cam in, setting the clearances and away you go(i guess it should be the same as any cam install.. perhaps forget this question.. ) Has anyone done this with a forced induction application who can comment? a second opinion goes a long way.
I am currently running wasted spark ignition, custom plenum, wolf 3Dv4 and it is tuned for the last supercharger install (intercooled SC14).. i found the tune very difficult with lots of fuel and crazy timing to reduce detonation.. I was running 5.5psi.. tired engine but you would think this would help, not hinder.
Any help at all will be appreciated.
2 suggestions.
Buy Greg Gordon's book on supercharging and learn as much as you can about water injection!
Greg's book has massive amounts of information about water injection but there is still plenty more you can learn about the subject.
Unfortunately there is also plenty of marketing driven crap out there on the 'net.
Rather than simply dumping compression with questionable modifications like shorter rods, which will leave you with some pretty piss poor squish area, take control of the detonation problem(s).
Obviously a fresh engine will be on the top of your list of 'wants'. And obviously building an engine to suit your forced induction desires is a very good idea and that is always offset with real world funding. But a stupid low compression ratio engine with a cr@p supercharger will be neither powerful, decently drivable or fuel efficient.
A fresh engine that is properly run in, will have very little blow by. This will help keep the knock point as high as possible because blow by gasses heat the inlet charge and any oil mist that travels with it has an octane reducing effect.
IE: It promotes detonation and also causes carbon build up which can get hot enough to cause pre ignition.
For me, if I was building a positive displacement supercharged engine and had to keep using the Toyota supercharger, I would keep compression no lower than 9:1, with a decent intercooler (they are an old, inefficient supercharger that heat the air a lot for the pressure they develop) and water injection to give a tuning advantage at higher boost pressures.
Rather than worrying about camshaft profiles, take advantage of the Alfa's adjustable cam gears to help reduce combustion chamber temperatures. By advancing the exhaust cam a few degrees (have it open a few degrees earlier), the supercharger will help to expel the hot exhaust gasses and help cool the combustion chambers and reduce exhaust gas contamination.
Even if a good rebuild isn't at the top of priorities, a good oil/air separator or a simple externally venting catch can, good water injection and advancing the exhaust cam timing should help a lot with detonation problems. Also make sure that the intercooler's internal surfaces are clean and free from oil deposits.
Thanks Duk,
I am using an Eaton charger this time around, and won't be using water injection.. I figure factory supercharged engines don't use it, there should be no reason I need to at the modest boost pressures I am building for.. I am not interested in big numbers, I had 92kW on the bitumen with the last setup at 5.5psi, and it transformed the car.. my target is about 110-120kW for a strong everyday Alfa.
I am not sure i would refer to a low comp ratio as "stupid", but I take your point on the cr@p charger. For info, the intercooler that is in Buzzed twincharge project was built for my first supercharger project.. so, I had a cr@p charger, and a pretty large tube and fin cooler that was custom built and new, 10548 cams and detonation that had me throwing bucket loads of fuel at it of which it didn't utilise and passed through what I suspect to be the overlap.
I am not sure the shorter rods to reduce compression is a questionable mod either.. If the calc's work out, then infact it will prove to be a very cost effective method for reducing compression in a Nord engine. The calc's will tell.
My understanding of "blow by" in a forced induction system is the charged air and fuel is entering the crankcase past the rings rather than the crankcase venting to the combustion chamber(unless under decell or vacuum/closed throttle). Biggest issue with this is the contamination of the oil with the unburnt fuel reducing it's ability to be oil. I currently have an oil/air separator and am not returning the crankcase vented air to the inlet tract..
I was hoping for a more constructive view on the 10548 v 10520 exhaust cam and will continue on my quest.. What Buzzed had to say about it made pretty good sense to me.. and considering the difficulty I had with the amount of hydrocarbons in the waste gas, is worth a try. I have a set of 10520's so will give it a go.. it's only time afterall.. What you say about the 10548 and advancing the exhaust cam to further add to the overlap I am not sure will help, but again, is worth trying.. Thanks for the advice..
cheers, Dan
Quote from: Blown116 on May 18, 2012, 07:57:59 PM
I am not sure i would refer to a low comp ratio as "stupid", but I take your point on the cr@p charger. For info, the intercooler that is in Buzzed twincharge project was built for my first supercharger project.. so, I had a cr@p charger, and a pretty large tube and fin cooler that was custom built and new, 10548 cams and detonation that had me throwing bucket loads of fuel at it of which it didn't utilise and passed through what I suspect to be the overlap.
'Stupid low' compression would be less than 8.5:1 when you have all of the tuning potential of a programmable computer and decent forced induction.
I wasn't aware that you were using an Eaton SC and they are definitely a MUCH better supercharger than the olde Toyota unit. They are still flat out around a 1.9-2.0:1 pressure ratio, though. I hope you are using an M62 rather than an M90.
Quote from: Blown116 on May 18, 2012, 07:57:59 PMI am not sure the shorter rods to reduce compression is a questionable mod either.. If the calc's work out, then infact it will prove to be a very cost effective method for reducing compression in a Nord engine. The calc's will tell.
Compression numbers are like quoting something like a weight distribution percentage, it tells some information but leaves out a lot of crucial stuff in the process. It's potentially very misleading information about what's going on/what the potential is.
The squish characteristics will effect how much stagnant air and fuel mixture exists around the periphery of the combustion chamber. Stagnant air/fuel mixture can cause detonation and incomplete combustion.
Quote from: Blown116 on May 18, 2012, 07:57:59 PMMy understanding of "blow by" in a forced induction system is the charged air and fuel is entering the crankcase past the rings rather than the crankcase venting to the combustion chamber(unless under decell or vacuum/closed throttle). Biggest issue with this is the contamination of the oil with the unburnt fuel reducing it's ability to be oil. I currently have an oil/air separator and am not returning the crankcase vented air to the inlet tract..
Don't worry to much about gasses getting past the rings during the compression stroke, that pressure differential has nothing on combustion pressure. 130-180 ish psi vs 1000+psi. Blow by is therefor combustion gasses that get past the rings.
Quote from: Blown116 on May 18, 2012, 07:57:59 PMI was hoping for a more constructive view on the 10548 v 10520 exhaust cam and will continue on my quest.. What Buzzed had to say about it made pretty good sense to me.. and considering the difficulty I had with the amount of hydrocarbons in the waste gas, is worth a try. I have a set of 10520's so will give it a go.. it's only time afterall.. What you say about the 10548 and advancing the exhaust cam to further add to the overlap I am not sure will help, but again, is worth trying.. Thanks for the advice..
Buzzed is certainly a clever bloke and his advice should definitely be taken on board.
Greg mentions in his book about the advantages of the
correct amount of valve overlap in supercharged engines. Those advantages are not available to turbocharged engines because of the pressure build up caused by the turbine housing.
Twincharged engines (like Buzzed's engine) can be thought of as a supercharged engine in this instance as the compound pressure ratio caused by the 2 compressors will give a higher boost pressure than exhaust manifold/pre turbine housing pressure.
If you have the cams to play with, that's great and maybe worth a play. I wouldn't chase after them for the sake of a force fed engine myself.
Gregs Book on supercharging is full of everything you needed to know but forgot to ask :-)
Quote from: Blown116 on May 17, 2012, 11:59:24 AM
Thanks StormX,
how was the deck height on the pistons? any protrusion? are you using the Nord rods or TS rods? have you calculated the expected comp ratio?
do the TS pistons and Nord pistons use the same size gudgeon pin(wrist pin)?
Cheers, Dan
There is a slight protrusion that i was worried about, but it will be fine.
Im using the TS pistons with nord rods.
Dont know the comp ration at all.
I was going to rebuild the motor with the TS rods and nord pistons,but i bought some dellorto carbs,turbo manifold and a dizzy to retard on boost. While speeking to the guy he said it was on his Alfetta in a 2.0 nord , standard rebuilt motor with 10548 cams and TS pistons running 150rwkw at 15PSI so then i decided to just use the Pistons and not the rods.
He was running a standard vlturbo turbo or similar and claimed it was on boost around 3k.
So i have rebuilt my motor exactly the same but now i am going to run fuel injection, e85 fuel and water to air intercooler.
From what I have read the comp ratio with Nord rods and TS pistons is down in the low 7's.. pretty low.. I expect you will be pushing large quantities of air into it for such a low compression..? I guess the protrusion will be covered by the head gasket thickness?
I have calculated around 8.4:1 for the nord pistons on TS rods and bought a set last week based on this... on the hunt now for an engine to put them in..
I have stalled with my install due to the auto tensioner that I am using on the supercharger belt run.. I had adapted a BA falcon plastic wheel spring tensioner to the aircon bracket, but the load on the belt is ridiculous.. I am chatting with the tensioner manufacturer to find an alternative.. I might have had a breakthrough today with a lower spring rated Jeep 4.0L belt tensioner.. Will source one and get the mounting block milled down to accept it's different offset.
My dream is to have a setup that is shelf stock for all used items.. I am planning a Jaguar XJR airbox and air filter modified to fit the small gap between the top of the splash guard and underside of the bonnet in the space between the brake booster and the edge of the engine bay.. I will feed cold air to it via ducting and maybe turbodelta style bonnet vents to try to keep the car looking it's age. Belt tensioner looks to be a Dayco branded Jeep unit now and the rest is not expected to wear out.. Charger is C230 Mercedes (Eaton M45) and belt is a 5PK1295.. I will have a 12inch push fan and 10 inch pull fan with the 550x145x65mm intercooler mounted forward of the push fan. The supercharger bracket will have inlet and outlet incorporated into it and the pipe runs to the intercooler will be minimal and 2.5 inch. I have to up to 3inch at the throttle body as I am using the Ford Explorer unit.. Custom alum plenum, supercharged commodore v6 injectors and Wolf 3d v4 computer with wasted spark coilpacks.
Apart from the TS rods, the engine will be stock with cams as discussed being the 10548 inlet and 10520 exh. I'm looking for 10psi and 120kW at the wheels.. Last build was 5.5psi and 92kW ATW on a stock smokey motor with 10548's.. I'm remaining hopeful.. The only thing I haven't calc'd is the drive ratio and until I run it, I won't be changing anything.. The charger pulley is about 68mm and the drive pulley is 125mm.. So I have a little room to move. The charger is efficient up to about 14000rpm, so I can increase the drive pulley a fair bit since the engine max revs will remain around 5200-5500rpm and realistically rarely see it since it will be a street car and I am too old to show off...
Anyway, thanks for the interest.. if anyone can think of tips or advce, let me know.. I'll post some pics when I get the belt issue sorted and soon after that it will be running on the old engine.
Has anyone adapted a smaller alternator onto the Alfetta GTv that they can give me some advice on? I have a close proximity with the tension side of the belt with the standard 65A Bosch unit and would like a smaller diametre alternator to be able to rock the whole system further away from the engine and down toward the oil flter on the standard mount.. Buzzed has said that some people use Barina?? alternators.. from what I have read they are about 80-100A and the pics show them to be pretty small.. if anyone has done it, does the pulley swap over and align on the standard mounting?
Cheers
The Barina alternator I am using is rated at 40 amps which is too small for a street car.
OK, so finished article.. don't mind the aircleaner, it's very temporary.. as is the engine.. i haven't built the low comp engine yet.
First run has a net boost of 2.5psi with the charger stock pulley at somewhere around 70mm and the custom drive pulley at 125mm.. Drive ratio is 1.78:1 or thereabouts. Admittedly i was calc'ing expected boost of 6-7psi based on incorrect charger displacement data.. I thought I was turning 0.96L/rev but my latest data says it's 0.74L/rev.. vastly different.. never mind, i was always going to be increasing the drive ratio to get my numbers. to be honest, i am surprised the difference even 2.5psi makes to the pulling power of the alfetta.
Struggling to post a photo though.. I am a novice at this.. anyone have any ideas? All the "insert image" button gets me is below..
(http://)
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not sure anyone is interested but my wife is sick of hearing about it..
have the new pulley now.. 170mm.. pic attached.. will push the drive up to about 2.4:1 and hopefully the boost above 8psi.. we'll see this weekend.. belt is coming friday. I can't fit a larger pulley than this as it will contact the chassis near the jack point at the front of the engine bay. The drive ratio will see the charger running at the limit of it's efficiency at max engine rpm anyway..
Airbox is almost finished with cold air intake to radiator facia as per pic. I still need to make a duct from beside the highbeam to the mouth of the cold air to make sure it gets air.. new fans are mounted on the alum radiator, wired up and controlled by the computer..
Low comp engine not started yet.. wanted to sort the boost levels before i started another project.. will start stripping the old engine next week.. balancing of the rotating stock will happen soon after that and then just rings and bearings rebuild with TS rods under Nord pistons.. all else will stay standard.
Boost!!! Must have boost!!!
Mmmmm....I spy carbon.
What type of radiator is that ?
Ok.. finally got the pulley on and a belt that fits.. it seems the design is in between belt sizes.. I am running a 5pk1370, but really need a 5pk1360.. no one makes this one..
Had some electrical gremlins that has delayed my test drive, issues with idle and idle air stepper aswell.. With those resolved I got it started last weekend to find that increasing the drive from 1.8:1 up to 2.4:1 increased it's decibel output from "pretty reasonable" to "downright offensive".. infact, it was so loud I decided I couldn't even test run it to find out what boost levels my new pulley was getting me... So, with disappointment, I almost conceded that a streetable supercharged Alfetta was infact a dream that I couldn't make come true.. But hey, the German giant Mercedes can make a streetable car, surely I can too on my meagre budget.
I visited a Merc wreckers on friday, and grabbed the intake resonator from the M271 supercharged 1.8L engine. It's a little plastic box that fits inline between the aircleaner and the charger(item 100 in the attached pic).. It has a series of internal chambers and perforations that assists to make the Mercedes a streetable car(they have 2 output resonators aswell).. I figured it was worth a shot. So, fitted yesterday, and still using the megaphone style pod filter as seen in previous photo's, has unbelievably brought the charger noise to an acceptable level.. Test drove it tonight. It still has some noise about it, but I am suspect as to the condition of the charger(to be confirmed on inspection by a pro) and will further reduce noise with an airbox and cold air intake which still fits with the resonator in place... Dream is back on track.
The thing is pinging it's little head off now though.. I have a theory that the pulley guys disassembled my crank pulley and striker plate for the crank position sensor (when they were cutting the new charger drive pulley..) and have reassembled it out of phase and thrown my timing off. This to be proven with a timing light (however not at 9pm at night since my sleeping kids might have a problem with an idling supercharged Alfetta in the garage).. It might explain my almost hydraulic lock when starting too.. almost like an engine with a blown head gasket that has water in the cylinder.. But it doesn't. The car ran fine before the pulley guys did their thing.. it's the only thing that has changed. The engine is tuned for 5psi, so it should be fine.
But, all said and done, I have boost.. it's hard to gauge just how much, but it's more than 7psi which is reassuring.. the pinging is so bad that I dare not risk a WOT to check total boost.. The car is running super hot as well even with the feathered throttle that I drove it with(so not a boost thing).. ambient air is prob around 12-13deg, so poorly set timing would add to this also..
Quote from: Storm_X on August 10, 2012, 06:24:23 AM
What type of radiator is that ?
StormX, I had it built by a rad place in dandenong.. it was cheaper to have the original one copied in alum than it was to have the alfa one refurbished at the time as I lumped it in with an intercooler build(the one that Mike has just decommissioned on the twincharge).. So, to answer you, it is a copy of the original.. In hindsight, I should have spent the extra and got the original one rebuilt as it is better for heat transfer, but that said, it is very easy to make changes to things like fan location and orientation of the inlet and outlet spouts on the alum one..(i just pay someone to do it.. haha) .. my last build ran an elec water pump, so the outlet spout of the rad pointed up toward the battery mount where I had the pump located. I had a gutted waterpump housing welded up to get the water into the block.
And Mike, you might have hit the nail on the head with your guesstimate of around 7psi on my setup.. damnyou.. haha.. I hate it when other people are right.. although, I have my hopes in a WOT and cracking the 8psi minimum i set myself to leave the setup alone.. if I don't get it, I am back to the drawing board with a bigger charger.. i might lie to you to avoid this.. haha
Oh, and I have a pretty Autometer boost/vac gauge mounted in the dash cutout where the choke and throttle lever usually go.. the 2 1/16" gauge jams straight in there.. from where I sit I get a clear view between the hoop and the top right spoke of the steering wheel.. much easier to read than the Wolf screen when driving. Just need the Tacho modified to accept the Wolf output and I will have all the info I need..
long post.. sorry.. today is a good day.. the car works. back on track.
Oh, and Mike, the carbon you spy is just 200gsm woven fibreglass fabric.. not too bad to work with.. a little tough to make it turn corners, but looks ok.. It was my first attempt at fibreglassing anything, so can't complain.. the black dye covers any air bubbles that got trapped at the sharp turns.
The airbox is moulded on an X300 jaguar XJR airbox with the top cut off it.. It's a pretty tight spot where I am trying to fit it.. The filter element is the main reason I chose it (high flow for the supercharged 4.0L jag) and also the angle spout on the base that runs down the splash guard to where the A-pillar and the shocker tower meet. I can fit the inlet resonator behind the exhaust mani against the firewall and still get plumbing to the airbox.. Still arranging the fibreglass patching for the base of the box before I can use it..
Here's a pic of the boost/vac gauge.. the only mod was to drill 2 holes in the mounting plate for the throttle and choke lever to receive the gauge threads.. the gauge comes with knurled nuts.. lighting came straight off the spare spade terminal on fuse9? i think.. which ever fuse the dash lights work off.
and a pic of the resonator with the pod filter set up for the test drive. (don't mind the hair pin holding the hazard button in - actually, does anyone know if there is an aftermarket replacement hazard switch that can be used inplace of my hair pin or are new switches available anywhere?)
OK, sorted the pinging issue.. The crank angle sensor striker plate had been reassembled 36 degrees advanced.. so at idle I was running 48degrees advanced and at higher rpm, pushing out to some 65+degrees.. thanks for that pulley guys.. To be honest, I am surprised it ran at all.. I won't bag them too much, I should have marked the pulley to striker relationship before I gave it to them.. I asked them not to disassemble, but knew they would. Rookie mistake.
So, surprisngly it only took me 3hrs to get the front pulley off and sorted and back on again... I can fit a rattle gun between the bottom of the radiator facia and the underside of the intercooler from the under bumper vents.. I had to undo the drvers side engine mount and jack the engine to remove the pulley, so radiator out, belts off, intercooler piping off.. then all back on.. 3hrs will do..
Drove it today.. will disappointingly admit that max boost pressure was only 6.8psi(don't tell Mike, I can already hear him laughing).. the car really steams, but my target was a minimum 8psi to keep the setup and I originally wanted 10psi, so it's a far cry from the original plans.. Since I am running the charger pretty much flat out and the chassis won't allow a larger pulley anyway, then I suppose I have to admit defeat on this one and up the charger size.. ouch.. I chalk this one up to a practise run..
I won't be building any engines until I actually require one.. 6.8psi certainly doesn't require a lower comp ratio.. It's fun though, so will sort the exhaust and complete the build with airbox and cold air, and either drive it until I break it or until I find the next charger... I have tried breaking this engine before and failed.. I expect the charger will come first.
This isn't over.
Quote from: Midda Samid on August 18, 2012, 10:56:58 PM
Drove it today.. will disappointingly admit that max boost pressure was only 6.8psi(don't tell Mike, I can already hear him laughing).. the car really steams, but my target was a minimum 8psi to keep the setup and I originally wanted 10psi, so it's a far cry from the original plans.. Since I am running the charger pretty much flat out and the chassis won't allow a larger pulley anyway, then I suppose I have to admit defeat on this one and up the charger size.. ouch.. I chalk this one up to a practise run..
I won't be building any engines until I actually require one.. 6.8psi certainly doesn't require a lower comp ratio.. It's fun though, so will sort the exhaust and complete the build with airbox and cold air, and either drive it until I break it or until I find the next charger... I have tried breaking this engine before and failed.. I expect the charger will come first.
This isn't over.
Have you checked for flow restrictions before the supercharger's inlet? Attach a water manometer to the SC's inlet and go for a full throttle squirt, that will show up any pre-supercharger air flow restrictions that will hurt power.
Similar for boost pressure testing. Have you tested the boost pressure at the SC's discharge port?
Thanks Duk, I haven't check charger discharge pressure yet.. it's on my list of checks to make sure the cooler isn't too small or restrictive.. It is a cheap cooler, so I expect some restriction.. it does well with the charge temperature(max 30deg in about 17 ambient), so it has to be failing somewhere for the cost.
Can you explain the inlet restriction test for me.. I don't understand.. Is it a calculation of expected airflow versus actual.. manometer tests pressure, so I suspect I will be testing vacuum? how does vacuum indicate restrictions? At best I could calculate an estimated airflow using the inlet area and estimated fluid properties(doesn't sound very decisive).. I am new to problem solving though, so will take any advice I can get.
If I was seeing inlet restrictions I would think boost pressure would drop as requirement for air increased(high rpm).. I would expect the same if I was seeing discharge restrictions also.. as air flow increases, system inefficiencies will show themselves almost exponentially..
I have since found a larger charger that I am close to buying.. just waiting on a freight cost and I should be the proud owner of an m62 in a postpack.. I am hoping I can use most of my fabricated steelwork for the mounting as there has been considerable hours thrown at it.. it will all depend on it's height and setback from the pulley..
Quote from: Midda Samid on August 19, 2012, 09:50:06 PM
Can you explain the inlet restriction test for me.. I don't understand.. Is it a calculation of expected airflow versus actual.. manometer tests pressure, so I suspect I will be testing vacuum? how does vacuum indicate restrictions? At best I could calculate an estimated airflow using the inlet area and estimated fluid properties(doesn't sound very decisive).. I am new to problem solving though, so will take any advice I can get.
Yeah, you're reading lots too much into it :P. The water manometer at the SC's inlet is just a sensitive pressure gauge. If the SC can move more air than what atmospheric pressure can fill up, the will be a pressure drop below atmospheric pressure (a 'vacuum').
As an example, the my factory supercharged Toyota MR2 had a pre SC throttle body so small, that at full throttle at about 5500rpm (from memory) it would pull 4"Hg (mercury) vacuum between the TB and the SC. That's 2 psi! That meant the SC wasn't getting filled with 14.7psi of atmospheric pressure, but only 12.7psi.
But anyway:
Quote from: Midda Samid on August 19, 2012, 09:50:06 PMIf I was seeing inlet restrictions I would think boost pressure would drop as requirement for air increased(high rpm).. I would expect the same if I was seeing discharge restrictions also.. as air flow increases, system inefficiencies will show themselves almost exponentially.
Good point.
nice.. found an article on autospeed relating to inlet restrictions today.. used the same method.
I am watching a supercharged 2.5v6 thread on alfabb where both Greg Gordon and the car's owner think the boost levels should be increasing with a positive displacement charger with engine RPM due to volumetric efficiency improving with rpm???
Would be interested in hearing some ideas or thoughts on this..
I guess i would agree if the supercharger rpm starts very low when the rotor clearances are allowing air to 'slip' by, but in a typical supercharger install where the charger is sized for the engine to minimise parasitic loss and maximise adiabatic efficiency, i'd expect a pretty flat volumetric efficiency curve.. ie, a small charger working flat out will have a better (and more linear) volumetric curve than an oversized charger running very low rpm for same volumetric output per engine rpm??
can anyone confirm or argue this?? Duk, Mike, i am looking to you..
I suppose I am wondering, (if this is the case), then what sort of boost shift would you expect to see? it'd be marginal at best, surely?..
Quote from: Midda Samid on September 11, 2012, 03:36:07 PM
I am watching a supercharged 2.5v6 thread on alfabb where both Greg Gordon and the car's owner think the boost levels should be increasing with a positive displacement charger with engine RPM due to volumetric efficiency improving with rpm???
Would be interested in hearing some ideas or thoughts on this..
I guess i would agree if the supercharger rpm starts very low when the rotor clearances are allowing air to 'slip' by, but in a typical supercharger install where the charger is sized for the engine to minimise parasitic loss and maximise adiabatic efficiency, i'd expect a pretty flat volumetric efficiency curve.. ie, a small charger working flat out will have a better (and more linear) volumetric curve than an oversized charger running very low rpm for same volumetric output per engine rpm??
can anyone confirm or argue this?? Duk, Mike, i am looking to you..
I suppose I am wondering, (if this is the case), then what sort of boost shift would you expect to see? it'd be marginal at best, surely?..
I can only comment on what I read in Greg's book, which is the same information. It makes sense, too.
If you look at the Toyota 4AGZE (1.6 litre, twin cam, 16 valve supercharged) engine, they used an old straight 2 lobe per rotor supercharger that displaced 1.2 litres/revolution. The best factory effort was 120KW.
If you then look at the supercharged Mini's, same (basic) set up, capacity, head design and number of valves with nothing special about the motor (no variable as far as I know), but having to meet tighter emissions, 120KW. The Mini used the Eaton M45, which moves 0.738 litres/revolution.
I can't comment on the shape of each engines torque curve compared to each other, but I'd bet the Mini has better fuel economy.
Supercharger compressor maps really do tell most of the story.
Not sure I understand the argument? if infact there is one??
I would imagine the Mini 3 lobe design is more efficient in a number of ways.. The fact that they can drive it at twice the speed to get the same volumetric flow rate is a good indicator of this.. the MR2 and mini setups are not comparable for this discussion. does the MR2 see an increase in boost pressures through the rev range? or the mini for that matter?
My question was more related to a positive displacement charger and the boost figures observed and whether they might increase wth engine RPM due to volumetric efficiency improving.
Surely, if a charger is seeing poor VE, it could only be due to basic design flaws like clearances between rotors and "blow by" of the fluid as it is drawn into the charger. If infact the clearances allow blow by, it will be an amount that I would expect would not change with each revoltuion regardless of how hard it is turning. 750cc's per rev and maybe lose 20cc's through clearances.. at 5000rpm, it will lose the same 20cc's each rev through the same clearances as it would at 13000rpm.. wouldn't it? so volumetric efficiency unless I understand the term wrong, is not changing.
Adiabatic efficiency is another story.. and generally shown on efficiency maps.. VE is not indicated on efficiency maps.. boost pressure, airflow, charger rpm and efficiency shading which I understood to be adiabatic.. infact, the relationship between airflow and charger rpm is amlost linear with outlet boost pressure
With an increase in inlet temps due to high boost pressures, you might see an increase in boost pressure as the pumped air increases in temp after the inlet of the charger. the charger draws the same 750cc's of ambient air and then heats it and shoves it into the inlet tract.. it expands, pressures increase.. this has nothing to do with volumetric efficiencies however... prob has more to do with heat soak of the inlet tract and charger body if t even happens...
I guess Greg G can't be wrong? I would be interested to learn more about it though.. obviously.
Found an interesting read in Pat Ganahl, a complete guide to street supercharging..
page 37 has some info on the different thoughts and opinions around blower VE. It's on googlebooks..
I was given an equation to calculate boost pressure on a given engine with a known charger capacity and drive ratio. With my setup it, the calc's came to 12.2psi.. I am seeing 6.8psi.. vastly dfferent.. would be interested if anyone has supercharged anything if they could plug in their figures and see if they are close to the calculated answer..
(charger displacement/(engine displacement x 0.5))x(ratio x 14.7)-14.7 = boost
for me,
(750/(1962x0.5))x(2.4x14.7)-14.7=12.27psi
if I fudge the numbers a bit and shift the VE of the engine to 80%, it increases the boost pressure(obviously).. if I shift the VE of the charger to around 80%, I can get the numbers down near the boost levels I am seeing.. realistically, my charger would have to be shot to be seeing such low VE at the rpm I am running it.. clearances would have to be huge which would either mean that my rotors have shrunk(unlikely) or bearings are shot which would show contact marks on the rotors from either the housing or the other rotor.. my rotors look fine..
for my previous setup with the smaller drive ratio,
(750/(1962x0.5))x(1.8x14.7)-14.7=5.53psi, again, a far cry from the 2.3ish I was seeing..
anyway.. food for thought.
I haven't found the required M62 charger yet.. The model I am after seems a rarity in Aus, so I am looking OS.. and haven't had a chance to do anything else car related either. The M45 system is all still installed, so i will play with that in the meantime.. I am still perplexed by the boost figure differences from the calc's and the actual measured PSI, so will play with the setup and see if i can't find some boost bleeding off somewhere.. The charger is remarkably noisy, so maybe I have got a boost leak at the charger outlet.. worth playing around with.. 7psi is plenty fun..
I have other misfire issues i need to sort too, so just need to get refocussed and leave my conscience at the shed door.. It's been difficult starting the thing without thinkng I am drowning out my neighbourhood's ability to think.. it's loud.. and my direct neighbour is one of our trusted protectors.. last thing I need is to upset him.
not sure anyone is interested, but hell, i have to tell someone(or something)..
Found some boost leaks with the ole "soapy water test" on the charger outlet manifold and the throttle body to plenum. There is a pinhole in my masterful welding in the charger outlet aswell..
while it is apart for repairs and improved gasket sealing, I used the opportunity to take the plenum and the inlet manifold off the engine to repair a weeping water leak.. what I found was that the injector angle in the inlet runners is focussing it's spray at the gasket join between the alfa inlet manifold and the plenum flange and over the 6 years it's been installed it's pushed fuel almost to the outside of the silicon formagasket that I was using... works out to be about 48 degrees from horizontal, so I have decided to redesign the inlet runners on the plenum to try to improve the injector angle and keep the fuel off the opposite wall of the inlet tract especially at low rpm(low flow).. I figure the airflow losses of curved inlet runners is a better option than poorly atomised fuel.. with a curve of about 34 degrees at a 75mm radius in the runner I can aim the injector at the valve head..
any opinions on curved inlet runners are welcome..
I think you're reading way too much into this 'curved runner = flow loss' thing. There would be more compromise in your plenum chamber design than that.
As you've mentioned, poor injector angle will probably be more of an issue.
Depending on how much room you have would determine which way you would curve the runners.
If you have the room to add a slight curve to each runner and that directs the plenum down towards the sump, then you could (as I mentioned on AlfaBB) put the injector at the outside of the bend radius and get a better spray angle.
If you have to add bends to the runners so that the plenum chamber is raised towards the bonnet, I'd then mount the injectors underneath each runner, again at the outside bend radius.
Thanks Duk, i have the space to curve down toward the sump.. It only requires a slight curve to get the injector 9 degrees above horizontal and shooting straight at the valve.. I am using 44mm runner inside diametre with 45mm of straight runner out of the plenum into 57mm of curved runner(outside radius measure) giving me a 34degree turn at a 75mm radius. The injector boss will be welded on the outside radius next to the join between the straight and the curved runner.. Total runner length including the head and Alfa manifold will be about 180mm average(with the current design). Runner to Alfa manifold is port matched, but apart from that, porting is standard as are valves.
I am planning on increasing the volume of the plenum by half to assist with piping from the intercooler, but have no idea what it will do to performance.. same for runner length, it is more designed for space constraints rather than function..
Plenum is currently about 1 litre and the runners currently add up to 0.56 litres. New design will reduce runner volume, but increase plenum volume.
And I always read too much into everything. :)
ok, I am back..
Curved runner modification completed and all of the original plan with custom airbox, cold air intake and supercharger resonator installed.
So, airbox is a jaguar X300 with the top cut off and fibreglassed to fit under the contour of the alfetta bonnet. Resonator is from a '99 C230 mercedes, and is fitted behind the exhaust manifold against the firewall.. it's tight. I have heat wrapped the number 4 exhaust primary, and before anyone says it will crack, well, that's too bad. if it does, when it does I will replace it.. the clearances to the resonator are about 5mm, so i figure a cracked manifold is better than an engine compartment fire.
Curved runner mod was simply that.. weld curved runners in between the flange and the plenum. I had the flange face machined and o-rings machined aswell an o-ring for the throttle body face.
I have reinstalled the heater and therefore had to find a new hole for my computer temp sender(as I was using the manifold to heater core outlet) .. i had a boss welded into the thermostat housing. Thermostat is reinstalled and have twin thermo's. 1 x 12inch push fan and 1 x 10inch pull fan. I managed to get the original overflow bottle in there too.. happy about that.. it's old and yellow, but it's meant to be there. Took some shuffling of the IAC and fuel pressure reg and oil catch can, but worth the pain.
Intercooler remains the same 550x145x65 and so far has proven capable.
Oil cooler hasn't been installed yet.. the one I have won't fit infront of the passenger wheel where I want it, so might have to source another.
And with such a full engine compartment now, I haven't space for a windscreen washer bottle, so need a solution there. maybe a soft bag type like the fiats used.. or mount one in the nose behind headlights.?? more thought on that.
Other than that, apart from some clean up of welding and fixing some pinholes(I can't weld) and giving everything a much needed coat of paint to beat the brown rust look, nothing else has changed.. pic's attached.
I am waiting for some silicon to go off before I can test run it. I am hoping for quieter operation and better control of cooling..
Inlet mod's might see transition from closed to open throttle seem smoother.. I won't be tuning it for a while, so realistically won't be bleating about power gains or tuning control anytime soon.. and besides, I am still well below my target of 10psi(hitting around 7psi), so need a new charger before I waste money on tuning..
Oh, car got new carpet and underlay while I was waiting for parts... charcoal.. nice. A tip if you are thinking of using a moulded carpet supplier - when they form the carpet, while it is being pressed they trim the edges.. I requested they not trim so I could fit the carpet at home and trim myself.. much better outcome.. usually the carpets come up a bit short at the kick panels, firewall, rear seat and door trim plates..
Yeehah! Good work 'ol chap. nothing more pleasing that doing thngs yourself...you may not be able to weld, but at least you have a crack, you will only get better!
Hi Mike, yeah, not always pretty, but I can boast it was all done in an under tooled shed in middle suburbia with the kids in bed.. haha. man, when you start adding extras to an alfetta engine bay, the space quickly disappears.. and the cuts and scratches start appearing on the backs of hands and forearms.. tight
I am ready to turn the key but am afraid to for the looming disappointment of a supercharger that can be heard 3 suburbs away.. if after all this it is stll noisy, i shan't yet admit defeat(**NEVER**).. I'll blame the second hand charger and source a refurbed replacement.. larger of course(when I get another job to pay for it).. that's all that talk of the m62 from the earlier c230.. new brackets required for that though, so won't be immediately.. Brisbane calls me.. actually, reminds me.. i need to email you.
On fitting the final resonator to charger piping I have found I run awfully close to No.3 primary also, so need to wrap that too.. that should delay my turn key enough for me to come to grips with the pain of 100's of hours spent and no result.. booo.. haha ;)
I don't want to say it, but that intake? is going to hit the exhaust on engine rock. Maybe drop the dia of piping and mount a stainless sheet heat sheild to the extractors to get the air gap, then wrap the pipe....could wrap the manifold as well in the fibreglass wrapping you can get from raceshops....it makes a decent difference and is cheaper than ceramic coating.
The insulated cast manifolds are not likely to crack. They will definitely, positively and without question crack. You need a solution NOW for that eventuallity which may take from weeks to months but it will be there.
Once that happens, you will have the added potential problem of dangerous carbon monoxides getting past the usual holes in the firewall and entering your cabin. Don't forget that carbon monoxide is an odourless and toxic gas. Not something you want to play Russian Roullete with.
Either make some headers to do the job or install an insulation barrier in sheet form available from Repco that will shield your heat sensitive parts but allow the majority of the heat in the manifold to be released. Forget about the convection heat and concentrate on the radiant heat which is the most efficient form of heat transfer and that is what you need to block.
This is the type of material you need : http://www.aclperformance.com.au/prod_heatshield.htm (http://www.aclperformance.com.au/prod_heatshield.htm)
thanks for the heatsield link.. looks good.. I expect the manifold to complain about beng wrapped, but i also expect an audible change to the engine bay before the levels of CO get to "life threatening".. new manifold is not an option.. $$$.. my solution for a cracked manifold at this stage is the spare one I have sitting in the shed.. and on a lighter note, any carbon monoxide coming out of my alfa has an odour.. trust me.. it's a smokey bbq of cheap oil and too much fuel with a hint of ...sniiiifff... sausages? no, must be some of my torn flesh and blood burning off all the sharp bits..
Mike, yep, it's close.. majority of the piping is fixed with the engine, so engine rock won't alter the clearances(much). at this stage I am only wrapping sections of the manifold rather than the entire tube flange to flange(see pic, it shows no4 wrapped in that fibreglass tape).. heat shield like MD has sent through looks the bizness.. next step is pricing it.. i bet it isn't cheap.. at this stage i am running a budget build, so cost adders are just opportunities for the wife to remind me how little money we have..
I still haven't started it.. what a wimp :(
You can buy the stuff Mike is talking about from ACL, pretty sure it is made in Qlnd. I have it on my car and bought 2 sheets. The sheets are about 250*700 from memory. 70 dollars per sheet is what I recal, and it is very good stuff. Just be very carefull when cutting it, it has ceramic fibre or something in side it (and from memory). What ever it was,m I recall thinking it was mask and carefull cleanuff stuff not to be triffled with.
I also have spare factory manfidolds kicking around which you will be welcome to. MD makes a good point with them, better not to wrap them.
started it today.. it's noisy.. made no difference adding the resonator and the airbox and cold air intake.. the noise is coming directly from the front end of the charger.. I have to assume the charger is stuffed and will have to consider a replacement.. I had an elec miss or ignition breakdown or something too, so have to find that..
I wrapped 100mm of the no.3 primary where it passes the inlet hoses and the no.4 primary is maybe 200mm wrapped..
how disappointing.!
I wouldn't give up on the supercharger. There's a chance it's the bearings and it just needs a rebuild.
I've sent you a PM
Cheers, Scott
Assume you have checked the oil level in the charger! I am sure you have.
Elec miss - make sure all leads are pushed down inside their sheaths. Try a nice clean set of plugs. Check earths.
Chin up.
Thanks for the positivity lads.. new task is to find a rebuild kit.. well done.
Mike, your signature thing doesn't mention the alfetta sedan..? do you still have it?
i've given up on the charger.. it's off the car.. I will be sourcing the M62 replacement instead of throwing money at the m45..
On a positive note, I drove it today.. elec gremlins sorted.. loose terminal on the coil pack and intermittent short on the TPS.. my curved inlet runners with better aimed injectors have all but eliminated the transition issues between closed and open throttle.. very happy about that.. the car was a pleasure to drive.. side pipe exhaust was even acceptable without the bigger bangs from the charger.. Was out in it for maybe 20 minutes.. Geez, Alfa engines sound f'n awesome.. and my new carpet looks the bizness.
And without the charger screaming away at 150dB, the pedestrians just went about enjoying their day with a quick glance at the Alfa going past and a smile rather than ducking for cover and frowning at it.. a nice change from the last year of my life.
I have left all of the intake system on the car to keep an eye on it's ability to deal with the proximity to the exhaust headers.. so far so good. I have basically replaced the intercooler to throttle body pipe with a pod filter and blocked off the intercooler to avoid any ingress of grit/water/snot etc.. Car is getting a 45minute freeway run tomorrow.. better check it still has RACV cover.. haha.. I see my future.. it involves a flatbed.. ;)
Had some cooling issues however.. ran well until temps got up around the 92degC where my fansare programmed to kick in and it couldn't reduce temps.. even driving at 65-70kph it couldn't reduce temps.. got it home, opened the bonnet with it running and still couldn't reduce temps.. alas, my 12inch push fan was wired backwards and was sucking air from the engine bay to the nose cone.. derr.. all sorted and we have temperature control.. what a fool..
And inlet air temps with the pod straight off the throttle body were up around 40-55degC.. bit high.. not much I can do about that though.