I did some searching on the topic and received two general thesises (is that a word?)

a) Less boost and more compression will yeild better preformance out of the same WHP

b) FI engines want less compression, NA engines want more compression

Can anyone support either of these logically? Thanks guys

 

well most people will say that if your going to do a high boost motor that you need a lower compression, which is very true. it is totally possible to boost with high compression but it gets a little more prone to detonation and such. you can make more power on say 10.0:1 compression at 14.7psi over 9.0:1 on 14.7 psi but over time the 9.0:1 compression is going to last longer and be able to push more boost later on. So higher compression will yeild more power but be more prone to detonation and such. while a good tune will make the difference in all of these things, if you plan to build a motor for high boost i'd say keep the compression well below 10.0:1.

 

9:1 is a great choice. I wasn't happy with my 10:1 street motor.

 

im goin 9:1 for my turbo 99 si...yea u will make more whp at a higher compression but it will always be harder on the motor but its all about the tuning

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ochsy03 &raquo;</TD></TR><TR><TD CLASS="quote">im goin 9:1 for my turbo 99 si...yea u will make more whp at a higher compression but it will always be harder on the motor but its all about the tuning</TD></TR></TABLE>

Not on pump gas you won't.

 

So If I want a "DD on steroids", whats a good compression to shoot for if i wanna use 89-91 pump gas? I will be going with 7psi on my turbo

 

if you are only using 89-91 octane I would say 8:8-9:1 would be the area I would shoot for.

 

i'm at 11.5 to 1 cr @ 7 PSI

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93turbo16 &raquo;</TD></TR><TR><TD CLASS="quote">if you are only using 89-91 octane I would say 8:8-9:1 would be the area I would shoot for.</TD></TR></TABLE>

I assume you mean 8.8-9.1 right?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Napoleon Dynamite &raquo;</TD></TR><TR><TD CLASS="quote">9:1 is a great choice. I wasn't happy with my 10:1 street motor.</TD></TR></TABLE>

what was wrong with the 10:1 boosted?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91BlueCRX &raquo;</TD></TR><TR><TD CLASS="quote">

I assume you mean 8.8-9.1 right?</TD></TR></TABLE>

you assume right

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hondaeg8 &raquo;</TD></TR><TR><TD CLASS="quote">

what was wrong with the 10:1 boosted?
</TD></TR></TABLE>

Couldn't run as much boost on pump gas as I wanted, didn't make enough power for me in the heavier car. Even on 104 octane sunoco at HPDE's there would be some knock when it's coming out of the corners at higher (18-20 psi) boost levels on warm days. Plus I was always scared filling up at the pump if I was going to get a bad tank of gas and deonate my motor into oblivion. I went from Wiseco flat tops (10.00:1) to Wiseco dished (8.77:1) and I'm just a lot more comfortable with it on a day-to-day basis. I can't say I've noticed a difference in low end so I'm kinda bummed I went high compression in the first place. I guess if I had an endless supply of C16 I might do a high comp setup to see if there really is any difference, but for a pump gas car I like my low comp better.