The bad part of Super Charging

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05 Mar 2011 12:03 #3808 by 928mac
I have been following some threads on other forums and have found some detrimental effects of Super Charging your 928 Engine.

PLEASE add your Ideas to this thread

It comes down to the blow by past the rings causes pressure in the crankcase.

This pressure and "windage" impedes the oil flow from the heads back to the pan.

The end result is;

The cam covers fill with oil and the oil pump runs dry.

Before you freak

This only happens during long extended high rpm runs around 6000 + rpm, and
normally while racing or tracking your 928 in corners.

only a few on the street (LA hills and corners for example) have experienced a lose of oil pressure due to this issue.
as far as I have heard

There are many Ideas and the 928 wizards are working on a fix.
So don't worry.

Some of the fixes are;

Full length windage tray, crank scraper and deflectors.

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This is a picture of the bottom of Sterling"s engine and the way he is going.
His page and really good read and pictures can be found here.
www.928sg.com/

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05 Mar 2011 16:38 #3826 by pcar928fan
Of course Sterling is NOT S/C-ing his car... It is a bore/stroke and ITB car... NO FORCED INDUCTION on that system, but the oiling is still important and that is a good idea that he is doing there...

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

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07 Mar 2011 23:02 #3864 by Kiln_Red
The debate over the 928s oiling issues will probably be never ending. Experts dispute both the cause and the solution all of the time. For anyone wishing to learn more on the matter, search the Rennlist forums. There is an infinite number of forums concerning oiling issues. It would take a week or two to read every last post. Perhaps those of you desiring a forced induction system and/or racing your 928 on the track would find the dialogue most beneficial.

It seems clear that the stock oiling system WILL NOT keep up with the demands that a race track puts on a 928. Don't be tempted to switch to Amsoil without making any other modifications like one Rennlist member has had success with and proudly advertises . Lightning doesn't strike twice in the same place. :)

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08 Mar 2011 00:31 #3865 by pcar928fan
Well, I disagree to a point... The folks who rev their cars above 6500 and in particular when G loaded are going to have an engine failure. Simple as that. Then they will do various things like dry sumps or whatever when they rebuild the car and then it will last better, but not indefinitely.

The auto cars will run good for MUCH longer as it is more unusual to rev them as high as the 5spd guys do, but if you don't change the tranny fluid REGULARLY and I am talking every 10ish DE/race weekends then you will have a tranny failure (thankfully that is about 1/10th the cost of an engine failure though...ask me how I know!)

Having tracked 928's for more than 14 years now I can tell you that I have also seen more 928 GT failures than any other type of 928. Think about it this way, there were damn few 90/91 GT's built (way more 5spd S4's from '87-'89) and I can think of THREE GT failures and not ONE S4 5spd failure. I am not saying they are not out there, I am just saying that I have not seen any while I HAVE seen several GT's fail... one more than once!

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

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08 Mar 2011 19:39 #3866 by the flying scotsman
James..............do you believe the GTs fail because they're solely being revved higher? what about street driven cars?

As far as Amsoil goes I've no opinion other than when I use Mobil 1 it stays clean for much longer than dino oil.

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08 Mar 2011 20:01 #3867 by 928mac
Oh God this is getting interesting and I have to get in here.

I agree with Austin that a moderately driven car, even sometimes hard, should have no worries.

I need clarification on the Amsoil please Austin because I was going to use it to reduce cam ware.
Its ZD factor

I am also curies James as to the GT failures that you are talking about.
Is it main bearing, rod, wrist pin or piston failure and why you heard they fail.

Guys I drive this car like I stoled it and so I am trying to head some of these issues off because I don't want to blow it up.

hmm I asked more then I told :)

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08 Mar 2011 20:14 #3869 by the flying scotsman
I also drive the 928.....quite quick :)

I've had every cover off the engine and alls fine; crank, cams, rods, etc etc...........its not superchargerd but it has seen 260 kph a few times.

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08 Mar 2011 20:45 #3870 by srshaw3
I am not an expert.
I have blown a few up.
Always rod bearing issues.
Always a track driven car, on track (sticky) tires.
Always on tracks with long corners.
I may have pushed to 6300+, probably not too much more.
I had an accusump configured as a pre-oiler and also to provide a surge of oil in the case of a lapse of oil pressure.
The motors I blew were all 5L bottom ends with Euro S 16v top ends.
I always spun a rod bearing.
I was using Amsoil.

I think it would be difficult to do so on the street and not lose your license :D

I suspect much of the blame can be laid at my feet as I assembled my motors with the oversight of one who had done so before me (and perhaps lacked the desired level of expertise and/or caution).

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08 Mar 2011 21:03 #3872 by the flying scotsman

I think it would be difficult to do so on the street and not lose your license :D

.


Cant go any faster.........believe me I tried (closed roads of course etc etc) :p

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08 Mar 2011 21:21 #3874 by srshaw3
It isn't a question of fast, but sustaining the speeds and rpms, through sweeping corners, over and over again for about 20 minutes, perhaps four times per day.

I am not disputing whether you have done it, but rather just clarifying my experience.

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08 Mar 2011 22:59 #3876 by pcar928fan
I agree with Stan for the most part...save the one person I know who blew his up Auto-X'ing. Now it is possible that they had a unique Auto-X course with some long corners, but that would be unusual since runs are rarely more than 1 minute in Auto-X.

On track, high revs, long corners with no breaks and you do it lap after lap after lap... that is what kills them. You just can't do that kind of stuff on the street and not be carted off to jail!

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

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13 Mar 2011 19:24 #3949 by Kiln_Red

Oh God this is getting interesting and I have to get in here.

I agree with Austin that a moderately driven car, even sometimes hard, should have no worries.

I need clarification on the Amsoil please Austin because I was going to use it to reduce cam ware.
Its ZD factor

I am also curies James as to the GT failures that you are talking about.
Is it main bearing, rod, wrist pin or piston failure and why you heard they fail.

Guys I drive this car like I stoled it and so I am trying to head some of these issues off because I don't want to blow it up.

hmm I asked more then I told :)


Brad, I was only meaning to tease Mark K from Rennlist who never misses a chance to boast that his track car has successfully used the stock oiling system for some time now. He credits the Amsoil 20W-50 for his longevity. I wasn't knocking Amsoil at all. Amsoil is an exceptional oil. Perhaps the best available. I just don't necessarily endorse the idea that Amsoil alone will make your 928 oiling system track prepped.

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13 Mar 2011 20:26 #3951 by 928mac
Ok, got ya Austin.

There was an article that I read and a tread that I followed about the ZDDP rating in oils.

Here is the Article
www.macysgarage.com/myweb6/ZDDP.htm

I feel that Is important to use a oil that will reduce the ware on the cams (due to their high pressure) and after researching them I feel that Amsoil is slightly above the rest

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14 Mar 2011 00:29 #3956 by Kiln_Red
I've never had any issues with Mobil 1 so I will stick to that. My 928s get Mobil 1 15W-50 only. There's no doubt that Amsoil is a great product though. You know how oil talk goes, Brad. It can be like religion sometimes. And Mobil 1 has my faith. :)

To each their own.

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