Author Topic: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.  (Read 5703 times)

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Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #15 on: January 30, 2021, 12:26:41 AM »
Still struggling for a badge and a name. So I suppose I can just fit whatever suits me at the time. So I picked up a Maserati Ghibli boot badge - as cheap as anything else around.

I spent a while in North Africa - Libya being one of my haunts  - Benghazi being one place where I did an HF communications project on the old war time airfield. I sent my old man some pictures as he spent a large chunk of his war time service in Libya and Tobruk. Actually he was with the Northumberland Fusiliers and got caught in the Tobruk siege along with a bunch of Aussies. He asked me to visit the Memorial to them at Mersa Matruh.

Although he rarely spoke of his war time experiences, on occasions when he did, the affection he held for his Aussie comrades was patently obvious. Although the British Government never awarded a medal for either El Alamein or Tobruk, Australia did issue the "T" medal and they awarded it my father who was with them during the siege - one of the few, true Desert Rats.

Throughout the campaign, he must  have endured many a Ghibli. I certainly recall how it would whip up the sand and dust and blow for hours on end. It got everywhere. I drove the coastal route from Tripoli to Benghazi twice and recall how many of the minefields still remain a serious hazard and WWII machinery littered the sands, only parts exposed as the Ghibli would blow the sands against it, and blow it off again.

Robert Menzies wrote to Churchill saying the Aussie guys had "done their bit" and deserved some R&R. Strangely, my father in law, serving on the Devonshire I believe, escorted the Aussie troop ships back to Aus. He was a handy boxer and there was a boxing tournament organized on route. He recalled making it to the final but his opponent was an Aussie Officer. He spoke of his concern at the time, about "Belting" an officer. I suspect a lot of guys would have relished the chance. But my father in law, although tall and physically very strong, was a gentle soul - a polite Welshman from the Rhondda Valley.

My father however, remained, moving on to Sicily and then Rome. Jesus, the things that generation had to endure!

So Ghibli it is!       
« Last Edit: January 30, 2021, 02:36:51 AM by Ascari32 »

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #16 on: February 05, 2021, 10:58:46 PM »
After my "experiments" with the MAF insert, which led me down a few blind alleys, I think I have gone as far as I can. In the process of trying to understand the changes to the engine with the CB's, the Autodeltas and the Supersprint exhaust system, eventually I got the MAF insert I had been searching for - 98660612501, alias - 280 - 218 - 055, alias - 280 - 218 182. 9866062501 is quoted as being the element fitted to a Porsche 911 Turbo up to 4 litre. Elsewhere it is quoted for a Ferrari 599 GT. But it is not produced anymore and one eventually ends up with an equivalent being quoted as 280 - 218 - 182.

However, I have been running with the 2501 for a little while, with the standard Alfa back boxes. Generally speaking they perform well but still break - up on moderate to hard acceleration. They seem to introduce a little hesitancy which I can only assume is due to their restrictive nature. But once the car is fully warm this reduces, yet still seem to be choking the engine a little. Light load cruising is pretty subdued and tick - over is actually quite pedestrian. Although quite responsive, it is really not till above 2500 rpm that they seem to flow better, although a bit raspy. In honesty, I don't think they will ever be quite right despite nice flexibility at low revs in urban areas.

However, I felt to conclude my experiments I needed to retry the Ascari's, if for no other reason than to give them another chance. Particularly since all the coil packs have been changed and the new MAF element fitted. The coil packs have led to a cleaner sounding exhaust with the Alfa boxes fitted, so would the Ascari's equally be cleaner sounding, and perhaps a bit more civilised at low revs?

With this in mind, I had the Ascari's refitted this morning. I checked the exhaust before I left the garage and it sounded pretty subdued at 750 rpm. Returning an hour later and it sounds menacing, quite clean, but non the less menacing and two - three times louder.

Driving away, it is obvious how less restrictive they are but one pays for that with the level of noise. The flexibility is surprising and the willingness to pick - up the revs; very, very cleanly and quickly, is immediately apparent. They suit the engine that much better than the Alfa boxes. 3000 rpm cleaner and less characterful than before but still quite startlingly different from the Alfa's. Obviously less restrictive as they create seamless progression as the rpm climb, with absolutely no hesitancy at all. Torque -er at low revs than the Alfa's - but god the noise!

I shall have to live with them for a while now, for despite thinking they are probably much better suited to the engine now than the Alfa's, I think they are best suited to the track. And the Alfa's, in all honesty, unsuitable for either. The exhaust system is very clean insofar as all the sound emanates from the rear of the car now, with either the Alfa's or the Ascari's. Gone is the 2500 rpm drone/resonance and the engine seems content as it is beautifully smooth and sounds silky.

My concerns about the exhaust system were allayed after communicating with Supersprint and the engineer who dealt with my concerns was damned accurate in his predictions of what to expect from my changes, particularly when the Alfa Twin Secondary Cats came off. So much so, I feel compelled to trust them further and order a pair of their rear sports boxes.

In the mean time, I have a few weeks to live with the Ascari's and although I think I will miss their performance above 3000 rpm, they make the my 3.2 JTS sound incredibly crude below!           

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #17 on: February 21, 2021, 05:10:25 AM »
Having got the car through MOT and dash no longer lit up like a Christmas tree, generally it feels much happier. But I cannot get over the niggling doubt about the air flow at tick - over, not matching the figures published for the MAF output. This is, I believe a function of the revised valve timing. Needless to say the output volts; a function of Kg/Hr air flow in the inlet manifold is above the figure quoted on the data sheets.

I have been down this route before, with varying degrees of success and failure - notably when I introduced a resistive network between the output of the MAF and the input of the ECU. This was during a period when the Alfa boxes were back on the car. Worst case was provoking Hill Start/ASR and fuel gauge failures, which Baz quickly identified as a function of my tinkering's.

However, during that period I was having some success with exhaust noise levels and but for these failure, i would have been happy to leave the resistor network in place.

But the Ascaris are back on and although after MOT the car performs a lot better, it is the bottom end which spoils the whole experience. So I decided to try yet again to achieve a compromise with noise levels. I cannot help but worry, the boxes may not be entirely to blame and genuinely believe, because of the higher kg/hr output at tick over, this results in a noticeably more powerful idle. However, by definition, if this raised MAF output level at tick over is creating a rich mixture at 750 rpm, it must follow that at all other points, where the MAF is involved, the mixture must be rich away from tick over also.

So taking what Gaz suggested was the initial problem, I returned to putting a resistor in series with the output between the MAF and the ECU: my very first attempts were this method, before a chose to use a Potential Divider Network.

I thought what GAZ intimated actually was a very good tool in determining the "Threshold" for MAF output voltage at idle. I also knew, from early experiments, 270 - 330 ohms were good values for performance, although this was during the period of PDN testing. Never the less, those values should be a good starting point for further tinkering.

270 ohms - good, exhaust level came down and no ASR/hill start/fuel gauge failure. Ditto, 330 ohms with exhaust level dropping by probably 3 - ish db. further.

Next, 360 ohms. Fuel Gauge to zero, although it did recover, (just back from filling the car up), ASR and Hill Start fails. So, I thought 360 ohms must be close to the threshold. 3 X 1k ohm in parallel + 30 ohms in series. Fitted a further 30 ohm resistor in parallel with the existing one, value now 345 ohms.

No failures or alarms and on taking her for a drive - sublime acceleration with still elevated noise levels, but no where near as bad as without the resistors. And no "Hiccups", which I attributed to slight misfiring due the over richness.

Came home, bonnet up, A/C and radio off, 750 rpm and a warm engine. DVM reading direct from MAF, 1.345 volts +/- 0.015 volts. DVM reading beyond the 345 ohm resistor value - at the input to the ECU, 1.2 volts, +/- 0.015 volts.

Bosch Sensor Data Sheet - 1.2315 volts.

OK, I will settle for that. Not turning heads as much and it all sounds a bit more civilized inside the car. Well almost, but still not good enough. However, this I believe I can fairly blame on the Ascari Boxes. I shall monitor the performance until a get my new boxes, in the hope that now, the MAF characteristic is more "In - Tune" with the true flow rate through the inlet manifold. 
« Last Edit: February 21, 2021, 05:40:05 AM by Ascari32 »

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #18 on: February 23, 2021, 05:03:20 AM »
I now have four MAF inserts to test after further experiments with the 055 element, which has the 345 ohm SOT in series with it. As I said, it has made the Ascari's at best - liveable at tick - over, if not entirely so when driving. So I continue to try and find a more definitive answer to my exhaust problems.

Somewhere on the Forum I read someone testing their MAF using the OBD II and it was suggested the kg/hr for the Brera should read seven hundred Kg. That is enormous, particularly as I have a chart which states ~ 300 @ 6500 rpm.

However, I wanted to explore the issue of "Over - rich running" during normal driving. So I revisited the Transfer characteristics published by Bosch. The improvement in noise level with the 055 element and the 345 ohms resistor in series corrected the voltage to the ECU to what it would be, but for the increased inlet manifold flow at tick over. It also reduced enrichment beyond tick - over although I think it is still too much. I not using much oil at all after the engine was rebuild, so I can only conclude it is HC's.


However, only 280 - 218 - 019 comes close wrt the shape of the slope, albeit their starting points differ: 019, 1.239 volt @ 8kg/hr and 055, 1.2315 volt @ 15kg/hr.

Needless to say, 019 runs out of puff at 1000 kg/hr, whereas 055 is rated for that flow. But according to my chart, that flow rate is way in excess of what it should be. I know response times are important but from the data I have, there is little to differentiate between any of them. So I reasoned, with such close threshold voltages 1.239volt and 1.2315volt, what significant difference would there be if I fitted 280 - 218 - 019, inclusive of the 345 ohm series resistor, in place of the 055?

Please see attached plot of their comparative responses. It is clear to me, 019, having a lower Kg/hr characteristic beyond tick - over, should result in a less rich burn and if the richness of the burn is in part responsible for rear exhaust box noise levels, the exhaust system should become quieter.

In short, it is! The Ascari's are now; in terms of sports boxes, tolerable. The noise they generate beyond tick - over is not as objectionable as hitherto and the way they scream above 3000 rpm put a smile on my face. All I need to do now, is leave it alone for a few hundred miles to access just how acceptable they are, long term. I will however, still be seeking to fit some good straight through silencers. But for the moment there is no need to refit the Alfa Boxes.


I should make clear, the Porsche 055 Insert response is the Pink Trace. The Blue - the 2.0 GTV. + 345 ohms in series. I feel it is a much better response and that is reflected in the performance of my car.     
« Last Edit: February 23, 2021, 05:10:03 AM by Ascari32 »

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #19 on: February 25, 2021, 03:15:32 AM »
Spoken - All too soon! Christmas Tree ligh(T) appeared again on the dash. Only went for a gentle jaunt to a local farm shop - 36 mile, round trip. Came up on the way there and I wondered if there was some obscure reason it happened when doing only 30 - 40 mph. None the less the car seemed to be running ok. But as we got nearer home, the exhaust became a little more coarse - I think. It is true, there is a huge difference between the kg/hr of the 2.0 GTV insert and the 055.

However, I felt the compensating resistor 345 ohms would have negated this at low revs. I really don't know, other than I would not want to risk running lean at any time. So when we got home 055 was refitted but I left the 345 ohm resistor in circuit. I checked the engine ran ok but was in no mood to do a run in it - I'd had enough for the day.

Today however, after a short run to Tesco's and the bottle bank, I waited by the car for my wife to return from the supermarket, with a triple espresso!!!

After a little while, a youngster drove off in his little Honda, with the "Ubiquitous" large diameter tail pipe. To him it must have sounded great and I could hear him 1/4 mile away as he joined the bypass. Which got me thinking - the Ascaris don't sound that bad - noisy yes, but not that noisy. And inside the cabin, it is a lot different from when I first started this exercise. Is it me? Do new boxes get quieter after a few miles? I have been in this loop for so long, it's almost as if I am losing track of what I am chasing.

So, at the risk of it all changing again, this is where I am at! 345 ohms restores the output voltage to the ECU to  nominally 1.2 volt, dropping about 110 millivolt across it, with 280 - 218 - 055 fitted. That 110 millivolt accounts for considerable volume in exhaust sound and the engine seems to lose a substantial degree of silkiness/smoothness when accelerating - indeed it sounds coarse. without it. Also, I think I can detect an element similar to a misfire - can't really describe it any other way. Not really misfiring but perhaps hesitant is the best way to describe it. A "Timing Error" - slow burn - due to over - richness?

Also, a greater resistive value reduces tick - over volume, but provokes an ASR/VDC/Hill Start/Fuel Gauge Failure. However, it seems there is little point in presenting a voltage to the ECU that is lower than that specified by Bosch in the data sheet for the 055 device.

In this regard I feel I can do no more and it seems clear to me now, I shall have to have a remap, combined with a pair of decent Back - boxes. The rear/boot area no longer resonates in sympathy with the Ascari boxes and it is possible to drive at urban speeds without too much intrusion from the exhaust. Where there is noise, it is appears to be emanating  from the Ascari's and not in the rest of the exhaust system.

For the moment however, I am going to have to live with the situation as it is, until I can get a good pair of rear straight through boxes that are relatively quiet. 74 db seems to be a bench mark for SPL, so I will have to explore my options. But I could try strengthening the Ascari's with some "Ribbing" as Colin suggested.       

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #20 on: March 06, 2021, 03:43:49 AM »
Rear boxes and MAF - issues and conclusions.

With BazzBazz’s input, came the realisation that there exists a voltage from the MAF; which feeds the ECU, below which a failure occurs, evidenced by ASR/VDC/Hand brake/hill start/fuel gauge fails. What I failed to add was; under certain conditions, the engine starts to “Hunt” - fails to tick-over smoothly.

With the valve timing changes, Autodelta manifolds and Supersprint exhaust system - not forgetting the Ascari’s, the output from the MAF is; in the case of every MAF sensor I have tested, well above the ECU threshold.

However, the Bosch MAF data sheets indicate, only one, 280 - 218 - 008, has an intrinsically higher voltage at the bottom of its Transfer Characteristic. From this, I have concluded, the output voltage can be reduced from the MAF when 008 is fitted, by a much greater margin before the onset of “failure” such as that covered above.

It’s starting point is 1.3395 volts @ 15kg/hr flow rate. For 055, which also starts at 15kg/hr, the voltage is 1.2315 volts. It is true, 055 goes to over 1000kg/hr, whereas 008 runs to 850kg/hr, but the characteristic curves are very similar despite this. And 850kg/hr is much more than a 3.2 litre N/A engine would digest. The other devices, with the exception of 280 - 217 - 123 which is wholly unsuitable, have threshold voltages similar to 055, which also limit the amount of correction any attenuation may afford.

So, I have chosen to use 008, to try and optimise the AFR before any software remap.

Making adjustments to the voltage the ECU sees @ 750 rpm, left considerable margin/headroom before the onset of failure, such as above. The Ascaris also became much less strident below 3000 rpm but it still required attention as to how the throttle was exercised, to prevent a horrendous cacophony. In short, I decided, the Alfa boxes were to go back on and the Ascaris - modified.

Today, the Alfa’s were refitted at the same time as the new front discs and pads.

I alluded to the fact that it was very easy to adjust the MAF output voltage and completely miss the optimum point at which exhaust system noise was acceptable. In fitting the 008, it has been possible to attenuate the output voltage from 1.45 volts to 1.3 volts, whilst the response stays pretty sharp. But not sufficiently to make the Ascaris acceptable.

However, when the Alfa boxes went back on, I have to ask myself - what has all the fuss been about, and why didn’t I manage to find the sweet spot before?

Needless to say, the Ascaris will not be modified - eBay or the bin. A second new Alfa box is being sought and some fine tuning around the 530 ohms fitted to the 008 MAF over the next few weeks will start in earnest, before the car goes for Dynamometer testing.

Conclusion - considerable exhaust system noise is generated by incorrect/over rich AFR. But beyond this, it really does depend upon the quality of the rear silencer. In this, the Alfa boxes may well have stripped a little off the out and out performance of the engine - because they are more restrictive. But not to the extent that they are unacceptable - particularly given they are now handling the upper revs in a much more refined manner.

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #21 on: March 07, 2021, 12:44:55 AM »
On a final note, After picking up the car, Adam left a message saying he would ring me later - had to go out on a call. However, between getting that message and him ringing, I had another Code failure.

On speaking to him, he said he had not extended the leads for the Lambdas as there were no recorded failures and suggested it may be related to the MAF, but would not speculate as to what that might be. However, the engine continues to perform flawlessly. So, for the time being, I shall ignore it and hopefully diagnostics will pick it up when it goes for remapping.

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #22 on: March 13, 2021, 08:04:56 PM »
 I continue to be occupied with this damned exhaust system. And the dawning realisation of the differing performance the Ascaris boxes and the Alfa boxes create.

It is fundamentally; I believe, due the differing restrictive properties between them.

I am becoming more and more convinced about the “de Laval Nozzle” phenomenon. The shape of the sports cat seems deliberately intended to assist the already low restrictive properties of the 100 cpi cat element. And the post cat stainless steel section appears to perform as a condenser. Lowering the pressure in this section can only increase the velocity of gas appearing across the canister of the cat. It is analogous to the steam condensers, post steam turbine as used in power generation, where it is desirable to achieve almost vacuum conditions, thus maintaining steam driving force up - stream of the turbine.

Whether or not this is absolutely accurate - wrt the Supersprint cat and centre section - it is true that the free - flow this system creates; in conjunction with the Autodelta manifolds and the PVO of the camshafts - it is sufficiently accurate as to positively state, changing the restrictive element of the rear boxes makes a direct change to the flow rate through the inlet tract and thus the output voltage of the MAF. 

Not having access to ECU software has meant, using Bosch Data Sheets for various new MAF inserts, which detail the kg/hr against MAF output voltage (to the ECU).

I have cross - referenced various voltages in attempt to find a Transfer Characteristic that best suits the new engine characteristics.

The rationale for this is based upon the premise that my original Dynamometer plot is indicative of a good ECU program.

This being the case, the improved engine breathing characteristics will simply change, substantially reflecting itself in increased performance - across the rpm range. It won’t be absolute, but should be pretty damned close.

What I have slowly began to realise; given I have been at pains to give the Ascaris as much opportunity to show their worth, is the difference between the various MAF elements, and hence their changing kg/hr, to the actual air flow through the inlet tract, depending upon whether the Ascaris or the Alfa’s are fitted.

So I never got the same result twice - until this final phase!!!

The Alfa’s being more restrictive, reduce the flow rate substantially, when compared to the Ascaris. Thus, although I kept a record of the idle flow - rates; as I did various tests with all five elements, it only began to dawn on me when I at last decided to abandon the Ascaris.

Aside from the dreadful sub - 3000 rpm cacophony the Ascari's produce, I needed a valid technical reason for their unsuitability. This, I now believe is due to the inability of the MAF elements to reciprocate the flow characteristics the Ascaris generate in conjunction with the camshafts, cat - free manifolds, sports cat and stainless steel centre section. Suggesting the whole system requires an element of restriction and the Alfa boxes, whilst not ideal, are better suited. This tends to be borne out by how much quieter the whole car now is.   

However, it has raised another spectre wrt Dynamometer Tests and the probability of doing some being premature, until rear boxes with characteristics which compliment the system are found.

It is frankly astonishing just how transparent the Autodelta and Supersprint Sports Cat and Stainless centre section; in conjunction with the Colombo Bariani’s massive P.V.O., has made the whole system - engine included.

The term “Transmission Line” springs to mind, whereby Maximum Power Transfer occurs when all components are matched.

From this statement, it follows that if any one component in the transmission line is “Off - Tune/Mismatched”, it is immediately reflected in increased power losses within the transmission system, and thus power to the load falls off. The load being in this case, the road.


So optimising a matching resistive network between the various MAF Elements and the Ascaris, did not yield the same results as with the Alfa boxes.

Consequently, the output voltages differed and it only became obvious, despite the boxes being changed over five times, when I finally cam to  justify my decision to abandon the Ascaris to the scrap heap.

However, with the Alfa boxes now fitted, in conjunction with the Porsche 055 element - 98660612501, and a series resistor value of 733 ohms between the MAF output and the ECU input, the performance is pretty close to spectacular. Relative to the cars weight and it's performance hitherto.

Torque is enormous - courtesy of the VVT system. True, when warm, the engine is ticking over at 950 rpm., but I am unconcerned as I think I need to do some fine trimming of the resistor value +/- a few ohms.

This does mean however, buying a pair of Supersprint rear boxes would create yet another shift in the “Tuned - point”, due to the differing back-pressure/ restrictive properties, between them and the Alfa’s.

So it is my intention now, to find a second new Alfa box and enjoy the car whilst doing a little more to trim the response. And maybe have the car Dynamometer tested with Alfa boxes fitted.

Delays created by Brexit means it is unclear how long delivery of goods from the E.U. will be. So, until timescales improve, I will make do without.

Sent from my iPhone

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #23 on: March 22, 2021, 11:37:37 AM »
Pointing me in the right direction as Bazzbazz did, when I provoked the above failures with my MAF tinkering has turned out to be a really useful tip/tool.

Now the Alfa boxes are re installed on the car, a similar exercise has been undertaken, to try to determine the right “threshold” for the 055 MAF element.

The combination of the Ascaris and an unknown/unsuitable Transfer Characteristic made it incredibly difficult to pin down exactly what the problem was. Although the true AFR remains unknown, and will until the car is re - dynamometer tested, it is reassuring to know where exactly the threshold of the MAF Transfer Characteristic begins. Clearly there is loop sensing of the MAF circuit which provides a tell-back to the ECU, in the event of it failing.

But the question remained - “what is the preprogrammed threshold of the ECU for fuel metering?” I cannot know that without having access to the ECU Program proper. So, until such time, the best I can do is guess-timate.

But a healthy  low end - torque is a good indicator. So that is the first clue.

Secondly, trying to marry - up the actual voltage, as seen by the ECU, cannot be determined precisely, whilst the increased air - flow through the MAF at tick-over, is generating an output voltage some way above the ECU map threshold, resulting in a over rich AFR.

Unless the MAF signal/output voltage is reduced. in an attempt to make them match, this too will result in a fuel metering error which will have consequences right across the Rev range of the engine.

So, by attenuating (reducing) the output voltage, at tick - over, with a fixed value resistor in series between the MAF output and the ECU input, the knee/threshold of the MAF Transfer Characteristic can be brought into alignment with the MAF input.

The beauty is, this fixed attenuation/reduction will have a pro-rata effect upon the AFR right across the Rev range.

This can only be an approximation at best. But reducing the rich fuel/air ratio, will manifest itself in, a) improved economy; within reason, and b) improved power and throttle response.

But it is subject to finding the right degree of attenuation/right value of resistor.

In introducing attenuation between the MAF and the ECU, progressively, power and volume of exhaust noise is reduced. An initial resistor of 733 ohms resulted in substantial refinement in both acoustics and engine performance.

Changing the value to 900 ohms provoked ASR/Hill Start/Fuel Gauge Failure. However, they did recover and the performance of the engine seemed to step up a notch or two. But it did result in tick - over climbing to 1000 rpm. I wouldn’t be unhappy with this and it probably deserves more investigation. However, on a positive note, it seems at least the threshold for the loop sense was discovered.

Until I can research this further, I made a general assumption that the best that can be hoped for is a value between 733 ohms and 900 ohms. Thus, I increased the value to 793 ohms. This value brought the tick - over back to 750 rpm.

A half hour trip around my test track gave really good acceleration, with superb progression- no holes/flat spots up to 5000+ rpm and wonderful low end torque, with super -quiet noise levels.

It would be nice to think I am getting close to optimum, albeit without a re - map, but non the less it is very satisfying. I shall leave any further testing for a couple of weeks, just to allow me time to digest exactly where I am in the whole process.

Ascari32

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Re: 3.2 Q4 JTS ASR/Hill Start/Fuel gauge Failure.
« Reply #24 on: March 24, 2021, 08:31:55 PM »
Hope you folks don’t mind, but all this is pretty much a diary, for a project which seems to be taking forever. I find myself wading through previous posts, just to re - check if I have “been there before”, with symptoms.

Such as, for instance - when trying various resistive values and deciding on a series resistor or a Potential Divider Network”. Above a certain value; excessive attenuation, on pulling away the engine became very easy to stall.

This problem had been a characteristic of my 159 before the engine was replaced, but at no time after.

So, why has the car started to do this now?

Well I can only hazard a guess and say, by reducing the MAF output voltage with the series resistor, it appears the voltage falls below the MAF default level. Meaning, the base - line figure at which point the ECU alone is deciding upon what fuel to inject, to keep the engine running when the car is stationary and the throttle is closed.

Thus, when the throttle moves from the closed position and the ECU is now reading MAF Air Flow, it is a lower figure than when the car is “at - rest”; thus, I stall the engine. Which makes it necessary to apply throttle to quickly get past that initial stall point.

This became a issue with 900 ohms fitted although I did not make the connection at the time - particularly as exhaust noise became much sweeter, if that is the right way to describe it. Also, it seemed the car was quicker - a gut feeling!

And so, I returned to 793 ohms: 733+30+30 in series. Again, it seemed there wasn’t the same “sparkle” and the exhaust noise increased a db or two. And, although less obvious, stalling the engine was still a possibility, if one wasn’t getting pulling away quite right!

This issue does not exist with 733 ohms, but the exhaust is louder, but still pretty damned good when compared with the Ascaris. Bottom-end torque is very “beefy” as well.

So, it seems; by default, I am pretty close to where the inherent ECU tick-over fuel setting, transits over to where the MAF derived setting should be!

From this, I concede it now looks increasingly obvious I can no longer avoid the issue of “Re - mapping”. The two conflicting issues being, sufficient richness at low revs to give good “Urban - drivability”; and it is great with 733 ohms. True also with no resistor but massively over - rich and louder, and a leaner AFR at higher revs for apparently more torque and quieter exhaust.

I love problems like these. The easy solution being to acknowledge one is at the limit of what can be done without software changes. However, this apparent “Nonlinearity” I detect - rightly, or wrongly, is somewhat different from what the Ascaris introduce.

This nonlinearity is solely down to the inherent mis-match introduced by the C.B. Camshafts, the Exhaust System, the less than ideal MAF Transfer Characteristic and the ECU Maps.

However, these factors are “Defined”. But, one element can, if modified, have a considerable positive effect upon all others - “The MAF”.

How? By attempting to create a nonlinear characteristic in the MAF output  to counter the ECU - essentially to “Tilt” the MAF Transfer Characteristic.

Maintaining the degree of richness at tick -over, which 733 ohms; or there about’s, provides, whilst modifying this value at higher rpm - lowering the dy/dt slope of the MAF.

On a further “Positive” note, I came across a company by the name of “Cybox”, who do flexi-sections to create equal length headers. And they are software specialists. They are based close to where my son lives. So, he will go check them out for me. He himself being a software specialist - in a different area, should be able to discover how good they are. They also do similar sections for the Busso V6’s, so they are starting with a few positives in their favour.

Now, I have to figure out the right degree of nonlinearity for my attenuation network. Or, at the very least, remove any notion from the equation and just get the ECU re-mapped.