Author Topic: Cause and Effect!  (Read 696 times)

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Ascari32

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Cause and Effect!
« on: September 08, 2021, 07:46:24 PM »
The pictures included are from a forty thousand mile - ish Brera engine. Clearly service shedules have not been maintained - oil levels allowed to drop, and or abuse of the throttle, low gears/high revs on fast bends - no sump baffles to prevent starvation. Plus Oil pick - up "Snout" is high above the sump pan floor.

First bearings to suffer are the front ones which I am informed is also common with the Busso. Reading a little more into this, it would appear when the Crankshaft is balanced it must include the front pulley/Harmonic Damper. However, it is borne out on two engines I have inspected - other bearings, although worn, were considerable less damaged than the front.

The three mesh screens across the VVT ports cause a pressure drop, slowing the VVT response. However, the oil feed to the inlet camshaft VVT is via the central screened port. Unfortunately the oil also feeds the front bearing caps of the
 inlet camshaft. So oil travels up to the screen from the NRV below and circumvents the screen to proceed up to feed the bearing cap. In doing so, it also permits oil to bridge the three ports via the flats.

So not only can any contaminants - metal shards - get into the VVT advance/retard voids, it can also travel to the front bearing caps, scoring the camshaft and wrecking the front bearings and caps - blocking the oil feed to lubricate the cap which is a micro - channel that snakes acros the surface area of the camshaft.

The consequenses of all this, in the worst case is wrecked cylinder heads. My 112,000 mile 159 heads are worth only scrap value - whereas the Block is pristine, as if it came straight from production.
« Last Edit: September 08, 2021, 07:59:50 PM by Ascari32 »

Alfatango

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Re: Cause and Effect!
« Reply #1 on: September 09, 2021, 08:21:07 PM »
It would be interesting to see how many commodore v6 engines didn't make it past 120,000km. Most commodores can do 350,000km quite comfortably. The busso v6 tends to get to 250,000km without much dramas. Not sure why the v6 in the 159 occasionally need rebuilds or new engines around the 120k to 150k km mark.

From wiki
The JTS direct injection system was first used in a V6 engine in 2005 with the introduction of the Alfa 159 and Brera. This is not related to the Alfa Romeo V6 engine, but is instead a derivation of the GM High Feature engine; built in Australia by GM Holden. While it retains the High Feature engine's 89 mm × 85.6 mm (3.50 in × 3.37 in) bore x stroke and chain driven camshafts, it is modified by Alfa for their performance, fuel economy and sound characteristics. These modifications include: "TwinPhaser" variable valve timing (cam-phasing on both inlet and exhaust cams, thus the name), gasoline direct injection and a higher compression ratio of 11.25:1. It also operates with a lean burn system up to about 1500 rpm,[4] as on many other engines from the company and is capable of generating 191 kW (260 PS; 256 hp),[5] a number matching the larger LY7 3.6 L variant used by GM. Alfa Romeo stopped using the V6 JTS engine in 2010.
159 3.2 JTS TI

Previous 2x GTs

Ascari32

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Re: Cause and Effect!
« Reply #2 on: September 10, 2021, 01:55:58 AM »
AT - the 3.2 JTS  uses only the Holden Block. The design and re-engineering of the heads was entirely Alfa’s.

However, it appears the Holden head cast was simply modified to accommodate Alfa’s VVT/Phasor system. I say this as the mistakes made by Alfa surrounding the rear bank can be seen on the Holden. In the case of the Holden, it was no mistake as there was no VVT on the exhaust camshafts - neither has the Vauxhall or the SAAB.

This being the case, there was more than adequate oil supply to the exhaust cam and hydraulic lifters.

With the increased oil demand of the Rear bank VVT however, mis-alignment of the feed - through causes a massive restriction.

Sadly, when this engine was further developed in the States, they mimicked Alfa and introduced the same problem to the latest version of this engine.

That’s what happens when there is no oversight of projects. So much of what goes wrong is because of plagiarism - it is a lot easier to look up someone else’s design than do your own. Unfortunately, if one does not understand the weaknesses of a design, they just get replicated.

It sometimes appears to me that engineering has been relegated to multi - choice answers at Colleges and Universities around the world. There are excellent institutions, but there is also a lot of dross!

Craig_m67

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Re: Cause and Effect!
« Reply #3 on: September 10, 2021, 07:47:16 AM »
It sometimes appears to me that engineering has been relegated to multi - choice answers at Colleges and Universities around the world. There are excellent institutions, but there is also a lot of dross!

In much the same way as computer programmers and developers has changed, now it’s about looking up libraries of code and cutting and pasting it together, mostly without any understanding of how/why it was originally purposed (or refinement)

It’s a race to the bottom.
And we’re trying to make it faster (worse) with statistical comparators (Ai from marketing)
'66 Duetto (lacework of doom)
'73 1600 GT Junior (ensconced)
'03 156 1.9JTD Sportwagon (daily driver)

Ascari32

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Re: Cause and Effect!
« Reply #4 on: September 10, 2021, 08:45:00 PM »
I agree!