most compression with boost? (success stories?)
08-07-2012, 08:15 AM
#1
most compression with boost? (success stories?) 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?
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?
08-07-2012, 08:39 AM
#2
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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.
08-07-2012, 09:50 AM
#3
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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.
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.
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08-07-2012, 01:24 PM
#11
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.
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.
08-07-2012, 01:28 PM
#12
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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
I ran my old personal car at 10.5:1 on E85 347 and have pushed upwards of 26psi with no cooler.
Zach
08-07-2012, 01:57 PM
#14
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!
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!
08-07-2012, 02:02 PM
#15
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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!
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!
