William A

Previous '88 S4 5 spd, no remarkable oil consumption, plenty of spirited driving. It is where I got the impression that 928's are bulletproof.

10 years ago, acquired a late year '93 5spd, 33k miles. I couldn't believe the oil consumption, a quart every 500-800 miles depending on driving style.

I have a love/hate relationship with my GTS. This oil consumption issue that is a symptom of other more insidious problems has been a splinter in my mind from the beginning.

Guess what, I will probably keep the car forever. Passion overwhelms reason in my case.

TexasDude74

People need to understand that Greg is a small business owner from the land of fruits and nuts. He rightfully sees things through a lense of liability. It's very easy for someone to say, "Hey, let's take a vacuum pump from the world of drag racing where engines run for seconds at a time and use it as a band aid on a 20 year old super car that will see thousands of street miles." Or to say, "Hey, 944's don't have the oiling problems 928's do so let's put their restrictors in the 928 engine and see what happens."

It's another thing entirely to build, test, make a kit out of and market these kinds of things to customers. I personally plan on experimenting with both a vacuum pump and the restrictors, but I do so at my own risk. Greg is just trying to do you a big favor by pointing out a mere handful of the many possible unintended consequences of such actions and you're trying to bite his head off for it.

Hilton

Is it possible that the US got the remaining old stock in 94 models and RoW got the better stuff (like how the USA got S brakes in MY86)?

ROG100

"like how the USA got S brakes in MY86"

All 86 cars both 16v and 32v have the S4 running gear.

Alan

(duplicate)

Alan

Well I do see that, and nobody so far has suggested that Greg should be required to sell a vacuum pump kit...

I'm certainly not trying to bite his head off - I consider I've been more than civil. I'm interested in his comments and the rationale for his concerns.

What Greg did say ultimately though is that this is about the worst thing you could do to a GTS engine:
(I think he's only jesting because I can think of far worse that's already been done...).

Anyway although Greg makes a forceful point - I don't find the argument very convincing based on my situation with my car, how I understand the configuration based on my research, or the actual available evidence so far.

Since I am amongst those with the most to lose here - I have a very strong reason to pay attention and consider everything carefully. Honestly I believe my car is really no worse off in my vacuum pump configuration than any totally stock GTS running around in Denver (using the giant vacuum pump in the sky) - think about that.

I'm not asking Greg to bless it here. Greg's not only saying he wouldn't do it (not just for liability reasons...) he's saying anybody who does should expect inevitable major engine damage...

I have said several time that I think he's overblowing this issue (for these mild vacuum levels) - I do think thats still true based on everything I have heard so far.

The thread has degenerated as so many do - unfortunate because this topic addresses an issue that is huge for GTS cars.

Love to see more actual evidence, maybe the only real answer will be long term results - for which we will have to wait. Its only been 11 months and about 6K miles since I installed it, but no regrets at this point.

Of course any installation like this is at your own risk - what else could it be...

Alan

Hilton

Didn't USA 86 models before VIN 1000 get 928S suspension/brakes? (I'm guessing you meant to say "All RoW 86".. but not sure what that has to do with my previous post?)

My point about GTS was that its at least possible the discrepancy between Alex and Greg's experience may be due to a US versus RoW anomaly. If Alex has seen factory-drilled oil holes in European GTS pistons that would imply there is a difference between USA and european 94/95 GTS.

siscogts

[QUOTE=GregBBRD;11201852]Like I said, in later 22:

"Oil is cheap, engine damage from lack of research, not nearly as cheap.".[/Quote ]

I understand what you are doing to better the engine... But:
1 understanding some tech stuff made me bleed from the ears. Too much effort for my brain.

2 I bought 2 liters of oil,my car use 1literof oil Every 3-4 k km, last 600kms trip used no oil at all, looking at the dipstick . Drive it like there's notomo rrow and will burn 1 liter every 800kms.i don't Think I am in troubles with my engine. My last BMW z4 used 1,5 liters for the first 7k kms, with gentle driving.then2 days at nurburgring and 2 of German free autobahn and used 3 liters of oil in 2300 kms, plus 0,5 liters of coolant. I was no worried.

3 I cannot understand if it is only a USA problem or also a row problem, nobody in European forums told me about this. Nobody told me about engine problems (excep for oil consumption of some cars), and I am guessing why porsche did not notice that during tests. Lack of research? There are no guys in Europe searching for a solution like you in the US.

Francesco

Alan

It wan't really the oil usage - I could maybe have lived with that (embarassingly bad as it was) - it was the running like crap when it started ingesting gobs of oil that I found unacceptable, car has good even compression & leakdown - so its not that. When the engine/oil was hot (so esp. summer) and taking tight or long sweeping turns that you felt it - sometimes even hard acceleration would provoke it... pretty lame.

This is now all gone - completely gone.

Alan

slate blue

Colin just thinking out loud here, maybe the reason for the performance improvement is that the rings in that engine are likely worn and lost tension and the vacuum you are appyling is helping ring seal and the rings have became like high performance rings. I have pulled apart a few engines with similar kilometers and the rings had very big end gaps and next to no tension. In fact so low that compression at cranking speeds was poor.

The ring tension in those drag race engines is very low if you undid the con rod caps and the motors was upside they would just fall out on the floor. Ring tension is a high source of friction in engines and this is the reason Cup motors are down to 0.6 mm in thickness and still low tension.

As to GTS motors having wrist pin issues, I haven't heard of this myself, that is only minor negative evidence, however if you look at the setup that does offer some clues. The setup is a full floating design, it also has a large gap between the rod and the piston where splash lubrication would play a large part. If the pin started to get tight on the piston side due to lack of lubrication the pin would still be able to move freely on the rod. Of course a non full floating setup has pushed in pins that are interference on the rod and float on the piston. This was pretty common on old trucks that didn't rev very high.

So if there is a problem that should concern you Colin with regard to the GTS engine it would be a customer that uses his engine hard and with lots of revs. Then potentially you get into other problems such as soft rods bearings, pick ups becoming uncovered etc. So field testing would be valuable. These changes are always a balancing of risks, the risk of this problem stopping the engine may well be less than say detonation caused by oil ingestion? It is interesting to say the least.

I just don't know how bad this problem could be

the flyin' scotsman

Perhaps Hilton, as the model was winding out of production they could have engines built with various pistons type?

Its of personal interest if other 92 GTS owners have same experience.

Lizard928

All the leakdown numbers on this engine were excellent to say the least. Most had 2% leakdown with the highest around 5%. This was tested at 100PSI.
A compression test was also done and the compression numbers were level across the board and right in line with every other healthy S4 I've used the gauge on. So I doubt that the rings have lots all their tension. Though they most certainly don't have as much as the day they were installed.

Cheburator

It is super highly unlikely that Porsche would bother to introduce 2R rods on all late MY 94 and all MY 95 engines and not change the pistons for US and ROW cars. That is not how things are done. I would actually say, it is nigh on impossible. All early GTSs don't have the holes drilled and the actual piston is different. The late GTS pistons look a lot more like a 968 piston...

Vilhuer

I've been telling Arnoud for a while already we need to remove his late '94 MY engine and see whats inside. All in name of common good.

Cheburator

I bet he claims he has a build up of ear wax, so he can't hear you...