Higher Compression w/E85 on Turbo S54?

[ZooyorQ]

I guess this isn't specific to the S54 so all you S52 experts in here, chime in.

So I'm in the process of having my engine rebuilt.. I'm on E85 now but was on Pump/Meth when it was originally built. I believe I'm at 9:1 right now.. I know E85 is more friendly when it comes to compression on a turbo car but would 10:1 be a safe amount for a T71 on a S54 running E85? How noticeable would that be?

[PEI330Ci]

I don't see any issue with that.

The thing is though....you really need to be focusing on dynamic not static compression. For example Pro-Mod cars run 13-15:1, but with huge cams the dynamic is in the 6:1 area.

When I had 2 sets of custom pistons designed and machined for my race engine, we went pretty high on compression because of the cams. (11.4:1) That was for 1000hp with nitrous and C23.

One of the main things that people aren't aware of with E85 and big HP, is that with larger ring gap you get more contamination of alchohol in the oil. In drag racing engines, they run different engine oils just because of running alchohol content....and change it often. On a low HP street car, this isn't an issue because you don't need to run a lot of ring gap, but on a high HP turbo....I can see this being an issue. I would do some research on oil contamination with E85, and revise your oil change interval.

That's about all I can think of at the moment.

[hobbit382]

I am building a s54, I went with 10.5:1 which is the same setup Jason from proefi has. they are wiseco pistons built to Saad racings specs. Give Saad a call.

[ZooyorQ]

I am building a s54, I went with 10.5:1 which is the same setup Jason from proefi has. they are wiseco pistons built to Saad racings specs. Give Saad a call.

Thanks! I'll likely end up bumping the boost up a year from now and changing turbos so I thought 10:1 would be a good fit for me.

[Sticky]

Thanks! I'll likely end up bumping the boost up a year from now and changing turbos so I thought 10:1 would be a good fit for me.

What is your goal? You can go higher on the compression if you want but I think 10:1 is a good choice.

[ZooyorQ]

What is your goal? You can go higher on the compression if you want but I think 10:1 is a good choice.

I'm thinking 10:1 is a pretty flexible compression... should I decide to up the boost or change the turbo later/etc.

[Twinturbom3]

you can run 10:1 compression on S54 as long as:

the tune is correct, and perfect. your tuning window will be smaller. The higher the CR the "less" room for tuning errors.

strong ignition system.

very good knock control is needed as well.

hardware should be designed to be used for high CR: the higher CR will yield a higher static compression. This means stress on the internals
will be higher. More stress on rings, rods, bearings, studs, head gasket.... You may try a set of "higher" duration turbo spec S54 camshafts in order to lower "dynamics compression".

Is it worth the extra burden? Nope. S54 can live with 9,5:1 CR and boost all day long happily.