and i'm not talking 4-5psi i mean something reasonable, like worth having forged pistons for.

ls platform and any fuel, but please mention the fuel!

I understand the tuning window closes, but is it dramatic?

Is it a matter of chopping more than .5* per psi boost?

or using unreliable plugs? or something far more complicated?

 

i have been looking at the same question . What i have seen is BAKED's car(stock cube ls1) 11:5:1 on E85 ported 241's with a glide at 15 pounds make 800 plus and run 8's at 3400 pounds.

 

You certainly do not need forged pistons with boost, just suitable pistons.

I'm a little under 9.0:1 now and can happily run around 23psi peak on normal 93 pump fuel only
Centrifugal blower so that level is only achieved around 7k. Will be fitting a smaller pulley soon so can see if it makes much more boost. It's only around 15psi at 5000rpm at the minute..
A turbo or PD style blower that can produce more boost at a lower rpm may not be as tolerant of a higher CR.

I only use water/meth when racing.

Different engine, but Ive tuned plenty of Subaru engines that are around 8.5:1 and can easily run 30psi on normal pump fuel with supporting modifications. Any more boost than that and I always run water/meth too.
Multivalve engines are more tolerant though so to run similar on a 2v engine it would like a lower CR for the same fuel.

Of course...how much power will you actually loose going from say 9.5:1 to 8.5:1 ? Very little I suspect, but it will gain a huge safety margin/tuning window if that's what you want.

 

10:1 with 40-42psi on Alky now, last year E98 non intercooled.

11:1 on E85 A2A street car at 19psi. 825rwhp through a t56.

 

I'm at 10.55:1 with a forged setup running ~15psi of boost at 6800 on 93 octane. Timing is around 15 degrees right now. I'm adding water/methanol as well.

 

Did you run the same boost on E98? How quick are you getting to 35+lbs down the track? Is timing full in at that point or still ramping?

 

10:8:1 compression, 16lbs of boost on E85, 15* of timing. Magnafuel 4303 is maxed out. Need to dyno but probably around 900rwhp.

 

Subscribed. My setup isn't quite done yet, but i want to see what others are doing. Mine will be kinda interesting for sure. Running e85 for fuel.

 

a buddys stock never opened ls2 vett 12psi boost 14degs timing, e50 fuel made 658 to the tire dyno jet t56 trans

 

if the 4303 is maxed out, then you should have much more power than that.

 

Yes we ran E98 up to 43 too, although we did run less timing on E98 vs the M1.

We can leave on as much as 25@4400rpm, and have been full in to 40 by .4 of a second. This results in killing the tires though. Our best runs have us at 40psi in .7-.8 with a little bit of timing being pulled. We still have not really 60ft the car very well best so far is a very lame 1.05. I should note the four times we went out on the M1 we have not had a working boost controller.

 

10.8:1 on a few pump 93 cars that we have built. For most of our street stuff, we vary between 10:1 and 10.5:1.

I ran my old personal car at 10.5:1 on E85 347 and have pushed upwards of 26psi with no cooler.

Zach

 

Pretty impressive numbers. Btw what size turbo is everyone running for said X amount of psi...

 

ok so good, its not outrageous to run moderate to high (i call 25 high) boost on high compression and race fuel or alcohol.

considering timing, where would i go with say 12:1 compression and 20# boost on 427ci. probably 13* ish a fair starting point?

and if i could get the boost down to say 10# would there be any chance in hell of it surviving on 93 octane?

frankly im nervous enough about running that high of compression WITHOUT boost!

 

I'm planning to run 12.5 CR with about 16psi.

 

Cam will play a big part on where you end up with timing too. If you are running a small cam with 12:1 it will be tuff to keep it from rattling on pump gas.

 

Maybe so. I guess we will find out this week when I dyno it.

 

naw its a big nasty sloppy sob.

 

Nice, let us know what you get.

 

ive been wanting to see a thread like this. mine is not really noteable but im on a stock shortblock (stock compression ratio), 12lbs tapering to 9lbs, 18-19* timing on E85.