piston rings supercharged 944

[BOONDOCKIT]

well my oil blowing supercharged 944 is coming apart, what should I use for piston rings??

[Porsche-O-Phile]

Duct tape.


Or socks.

[BOONDOCKIT]

I was looking for a more intelligent answer

[Porsche-O-Phile]

How about - go to the dealer and buy some rings, or go to the "Engine Components" part of this page and buy some rings.

SHEESH!

[ae1969]

Originally posted by Porsche-O-Phile
How about - go to the dealer and buy some rings, or go to the "Engine Components" part of this page and buy some rings.

SHEESH!

?

Boondockit.... If you are looking for a ring set that will minimize blow by try... They make rings for our applications.

http://www.totalseal.com/totalseal3.htm

[Porsche-O-Phile]

Were the rings replaced before you supercharged it? Otherwise I'd suspect just putting new stock rings in there would work fine. It works for 951s running the same or greater boost levels!

I fail to see what's so cerebral about this. It's pretty obvious.

[Zlatko]

Would the 944 Turbo ones fit on the n/a?

[Porsche-O-Phile]

Even if they don't, I know a guy that's running 15 lbs boost on an '86 n/a engine right now. No problems whatsoever. No blow-by. You should be fine with whatever ones are appropriate for your pistons.

If you change to 951 pistons, it will change your compression ratio to 8.0:1 from whatever you have (probably 9.5:1 or so), but you can make up for it at higher RPMs by varying boost.

[gearhead290]

rings are for fingers, not pistons HAHAHAHAHAHA


a stupid reply for a stupid thread

[ae1969]

Originally posted by Porsche-O-Phile
Even if they don't, I know a guy that's running 15 lbs boost on an '86 n/a engine right now. No problems whatsoever. No blow-by. You should be fine with whatever ones are appropriate for your pistons.

If you change to 951 pistons, it will change your compression ratio to 8.0:1 from whatever you have (probably 9.5:1 or so), but you can make up for it at higher RPMs by varying boost.

15 psi ? on a stock engine...... uhmmm interesting. Blow by would be the least of my concerns on that setup. Curious to see how long that will last.

Many questions involved when building an engine properly. Understanding why you would change rings in certain applications is just one of many.

Remember there are no stupid questions here, unfortunately that can't be said for all answers.

[Porsche-O-Phile]

Actually the guy doing it is Danno of Guru Racing. I think he knows what he's doing.

[ae1969]

Originally posted by Porsche-O-Phile
Actually the guy doing it is Danno of Guru Racing. I think he knows what he's doing.

I respect Danno...

but I have seen him toast engines as well.

And if he is telling you or anyone that 15 psi is safe to run on in an NA then my view of his opinion has dropped another notch.

....and as I recall he used total seal rings on his last engine.

[BOONDOCKIT]

I talked with total seal last eve, does anybody know if the cylinders are niksiled from the factory?

[Porsche-O-Phile]

Danno blew his engine because Anderson Racing screwed up the assembly - it ended up being a total POS, poorly put together - block cracked from the bore-out. Unfortunately, Danno took JA at his word that the engine was built strong and basically it wasn't. Anderson screwed it up although Danno (I suppose) was partly culpable for not double-checking everything. Send him a mail; I'm sure he'll be able to tell you the whole sordid story of it.

Suffice to say though, the n/a and turbo engines are virtually the same; the only major difference is the pistons & the compression ratio. The bottom ends (even of the n/a engines) are strong enough to withstand 600-700 h.p. AFIK so there's no problem there. The only real issue is the c/r since the n/a engines typically use 9.5:1 or 9.6:1 and the turbos use 8.0:1. The way around this (leaving the n/a pistons and c/r in place) is to run lower boost and/or dialed back timing - this tends to preserve bottom end torque at the expense of a bit of available higher-RPM boosted power (since there's less total boost being used). If you want, just get a 951 short block and either transplant it in or swap the pistons over into the car to give it 8.0:1 c/r and you should be fine boost-wise also. It's basically a personal preference choice.

Danno's current engine is an '86 n/a with a slightly shaved head that I believe puts him in the neighborhood of 10:1 c/r. He's had no problem with 12 psi boost and just recently started running 15 psi boost with 1 degree of retard on the timing. Works fine.

[ae1969]

Uhmmm I wasnt referring to JA's engine. I was actually referring to other cars that he actually tuned and made mistakes...... but we all make mistakes its called trial and error. This is not a danno issue anyway?

You obviously have not opened up one of these engines before. The blocks are virtually the same as you mentioned. The pistons as you mentioned are dished and lower the compression but the turbo bottom ends have a forged rods as well (83' NA's have forged and I have heard of random 84's having them as well.) A stock NA bottom end will not hold 600-700 hp ROFLLLL ..... I havent even seen a stock a 951 bottom end hold that except for a couple of glory runs.... and the Doom cars were FARRRR from stock....

Reducing the compression is the key as you mention. The dilemna is not only 'tuning' adjusting fuel, timing etc. The problem you get on a high compression engines is having to deal with ridiculous egt's as well. As the temps rise ... you guessed it. Detonation.Melt down etc....

The only way to properly run any boost over 8-10 psi reliably is to use a 951 bottom end.

I wouldnt be recommending to anyone to run higher boost on any NA engine. I have seen the aftermath of such endeavours. Cracked pistons, shattered rings, thrown rods...... etc.....

[Taz's Master]

I realise this is taking the thread in a different direction, and I apologize (hopefully the question has been answered).

But, why are egt's so high in a high compression/high boost engine? What is it that raises the temp? Assuming an efficient compressor, and perfect fuel metering, why do the egt's go so high?

[Porsche-O-Phile]

I should clarify a bit - I don't mean to say that a STOCK n/a engine bottom end can handle that power, rather it can be built to. Apologies for the confusion. Anyway, the point is that the engines are identical except for the pistons and rods. I think Danno is running additional fuel (slightly rich mixture) to keep the EGTs in check, but I'll verify that when I next speak with him to satisfy your curiousity.

Anyway, to get this back "on topic", I'll just say that the choice remains to run higher compression with lower boost (better low-end) or lower compression with higher boost (better top-end). The superior forged metallurgy tends to imply the latter as the better choice (I'm personally opting for this method on my own car). With regards to ring blow-by, I would stand by what I said earlier - whichever pistons are chosen (they should be stock to avoid damage to the alusil bore or to the piston BY the alusil bore) using good NEW properly installed stock rings should suffice.

[ae1969]

Originally posted by Taz's Master
I realise this is taking the thread in a different direction, and I apologize (hopefully the question has been answered).

But, why are egt's so high in a high compression/high boost engine? What is it that raises the temp? Assuming an efficient compressor, and perfect fuel metering, why do the egt's go so high?

The easiest way to explain this is where is actual compression occurring?

In a high compression engine most of the heat is generated in the combustion chamber.....

In a boosted low compression engine the charge is created outside of the combustion chamber........hopefully run through an intercooler to cool the charge ......and then into the combustion chamber.

Cooler charge ....less chance of detonation.

Also running a completely riched out mixture will not cure this problem.

In a high compression engine running boost I want to run low boost with a nice tight seal in the combustion chamber.........

IMO stock rings are not the best option anymore although I did use them in my last turbo engine. I can count the NA's and Turbos in my hand that dont have some symptoms of blow by. 99% of the 944's,951's out there when driven hard will have some signs. Take a good look at your intake boots.