This question has always bothered me. Usually you want to lower your compression to boost more, but i've seen many posts and articles on the web, and arguments about building your motor for stock compression, or lower compression to gain more hp per psi. I've even heard people say, hell raise your compression, lowering compression is for people who are afraid to blow their motor.

There was an article, i think it was on honda vision showing a test between two motors both built, one with stock compression and the other with lower compression. The power output by both cars came out the same cause even though the lower compression motor got more hp per pound of boost, it lost power itselfs from the block do to the lower compression.

So this is the question I want to know, what are the pro's and cons? Since i'm loooking to turbo my b16 in the future and fully building the motor, i'd like to hear some arguments.

Also does lowering compression have to do anything with gas milage? Like which would get better gas milage on the same block? A fully built turbo with lower compression, or a fully build turbo with stock compression?

 

lower compression= more boost baby more boost

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BallHawk3 &raquo;</TD></TR><TR><TD CLASS="quote"> arguments about building your motor for stock compression, or lower compression to gain more hp per psi. </TD></TR></TABLE>

Not really the way it works. If you raise the CR it should add HP . If everything else was standard a 10.5:1 CR motor would yeild more HP then 8.5:1 running the same amount of boost. . Lowering the CR can help avoid detonation but also lowers the efficency of the motor it self

 

lower compression = less power per stroke, but less pressure(heat) as well, which means you can run more boost, with substantially less pressure at a lower CR

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDMlifestyle &raquo;</TD></TR><TR><TD CLASS="quote">lower compression= more boost baby more boost </TD></TR></TABLE>


with lower compresion, you can run higher boost and itll leave more room for error, such as a bad tank of gas.
with higher CR, you will get more hp per psi, more linear powerband, and more streetable.

 

wut about gas milage? How does a lower compression effect gas milage? Like would a stock compressin turbo get the same as a lower compression turbo?

Also how about u guyz with a lower compression. Did you notice you gotta push ur car a little harder to get it into the higher rpms or boost? I mean its bad enough we got no power download with our B series, i'm pretty sure going from 10.2 to like 9.0 or something is a big difference.

btw i found that article. Here it is.
http://www.hondalife.com/modul...id=11




Modified by BallHawk3 at 2:48 PM 1/24/2004

 

The limiting factor between high and low compression is usually how much the owner can spend on tuning for safe boost conditions. I mean, we've all seen the Type-R turbos putting down rediculous numbers on like 10psi due to their tuning and high compression pistons.

All things considered, high compression is better for performance but worse on your wallet .

 

I always associated lower compression with worse gas mileage, but I could be mistaken. It depends how much you're boosting afterwards I would imagine.

 

Well wut would u guyz do? Say you were planning on tuning anyway. Why route would u go in rebuilding the motor.

 

Do a search on 'lower compression'

You will find all of the info you will ever need.

 

lower compresssion car relies less on octane unleaded gas to prevent pinging/detonation. high compression make more power but is limited to high octance fuel to prevent engine from blowing up

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BallHawk3 &raquo;</TD></TR><TR><TD CLASS="quote">Well wut would u guyz do? Say you were planning on tuning anyway. Why route would u go in rebuilding the motor.</TD></TR></TABLE>


what are your hp goals?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MaxSterling &raquo;</TD></TR><TR><TD CLASS="quote">lower compresssion car relies less on octane unleaded gas to prevent pinging/detonation. high compression make more power but is limited to high octance fuel to prevent engine from blowing up</TD></TR></TABLE>

Actually, I never really thought about that too. I should cause I do live in california and we are limited to only 91octane. Good point.

As for power, maybe the most i'd be aiming for would be 300-330whp. but thats turning up the boost once in a while like for the track or something.

I'm still wondering about gas milage though.

 

lower compression to a certain extent has a higher HP potential because you put more stress on intercooling etc. To remove the heat. Instead of having static compression in which you cannot remove heat (from the combustion chamber) You have a wider range of compression variation in which you can remove more potential cylinder heat.

Thus you can create more horsepower, but of course there are downfalls, and with modern technology (and nice race fuels) you can get plenty of horsepower with 9-10:1 compression!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BallHawk3 &raquo;</TD></TR><TR><TD CLASS="quote">

Actually, I never really thought about that too. I should cause I do live in california and we are limited to only 91octane. Good point.

As for power, maybe the most i'd be aiming for would be 300-330whp. but thats turning up the boost once in a while like for the track or something.

I'm still wondering about gas milage though.</TD></TR></TABLE>

personally im getting lower gas mileage turboed than before, maybe 4 mpg less.
others on here have stated that they get 30+ mpg.
personally, gas consumption is the least of my worries up to a certain extent.
as long as i got power, im happy


if i were you, since you already have the b16, i would leave it at that for the time being. boost the motor as it is. then, if you ever blow it or something like that, then i would do the rebuild. that way you can see how you like 'higher' compression motor with boost.