Im about to pick up a usdm b18c1 gsr swap. the motor has 95K on it so I'm going to go ahead and put new pistons, rods, and rings in it while its out on a stand. Im planning to go turbo down the road, maybe 6 months. I want to use some forged pistons between 9.5-9.8:1 compression and I was wondering how much power I'm gonna loose from running low compression on a stock gs-r motor. Is it gonna be REALLY slow? The motor also has CTR cams, will they work well with the low compression before i boost it??


thanks
chris

 

It is going to be very, very slow and very unresponsive. The engine will pick up rpms very slowly. I would recommend turbo then build.

 

i lowered the compression on my engine before i went turbo
and i notice not big power loss... drove the same as before... as a matter of fact, a bit more torque on low end

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cnydc2 &raquo;</TD></TR><TR><TD CLASS="quote">It is going to be very, very slow and very unresponsive. The engine will pick up rpms very slowly. I would recommend turbo then build. </TD></TR></TABLE>

Way to not have a god damn clue what you're talking about This is good as a foreign Math prof trying to help you with your english work. God, I get sick and tired of people chirping in when they don't have any first hand experience, and when they're just going by the **** they heard on here.

10:1 - 9.8:1 is .2:1 of a point drop in compression. For a FULL point in compression you're looking at around a 3% drop in power, so that 170 HP GSR will be putting out around 165 horsepower at 9:1 compression. If you think you're going to notice a 1 horsepower drop, you're lying to yourself. For that matter, if you think you're really even going to notice the drop from 10:1 to 9:1, you are also lying to yourself. On the street there is no discernable difference in throttle response between 10:1 and 9:1, and power feels almost exactly the same.

My motor is currently sitting at a little over 10:1 compression, and if I had to do it again for a street motor I would do 9:1, no questions asked. As a matter of fact, I found a set of 9:1 Wiseco's for cheap, and it's really tempting to buy them and swap em out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by USDM 4G VTEC &raquo;</TD></TR><TR><TD CLASS="quote">i lowered the compression on my engine before i went turbo
and i notice not big power loss... drove the same as before... as a matter of fact, a bit more torque on low end</TD></TR></TABLE>

i didn't notice that much of a difference either, i was still smoking civic si's

 

cool thats really good news, thanks.

anything else i should replace while i have it all apart??
It has a clutch masters stage II clutch already.

 

In my GS-R I have 9.0:1 Comp pistons, I blew an intercooler line off and the car became extremely slow. It was very unresponsive, maybe everyones car reacts different, I don't know. I would eat my brothers BMW with boost without I had no chance, so please don't tell me I know what I am talking about. Maybe It was the turbo in the exhaust disrupting flow, or I was running entirely too rich w/o boost,I don't know. I don't need to get flamed b/c my car reacted diff than yours, have you ever ran 9.0:1 n/a?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cnydc2 &raquo;</TD></TR><TR><TD CLASS="quote">In my GS-R I have 9.0:1 Comp pistons, I blew an intercooler line off and the car became extremely slow. It was very unresponsive, maybe everyones car reacts different, I don't know. I would eat my brothers BMW with boost without I had no chance, so please don't tell me I know what I am talking about. Maybe It was the turbo in the exhaust disrupting flow, or I was running entirely too rich w/o boost,I don't know. I don't need to get flamed b/c my car reacted diff than yours, have you ever ran 9.0:1 n/a? </TD></TR></TABLE>

Blowing off an intercooler hose and still driving the car hard is not only
A) Entirely retarded because you can destroy your turbo, but
B) Nothing close to an indication of how it would perform naturally aspirated.

See how small that turbine housing is? Pretty damn restrictive. Yes, I have had actual experience driving a 9:1 car with a header and a normal exhaust system on it. Feels basically exactly the same as my 10:1 car does.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Napoleon Dynamite &raquo;</TD></TR><TR><TD CLASS="quote">Way to not have a god damn clue what you're talking about This is good as a foreign Math prof trying to help you with your english work. God, I get sick and tired of people chirping in when they don't have any first hand experience, and when they're just going by the **** they heard on here.

10:1 - 9.8:1 is .2:1 of a point drop in compression. For a FULL point in compression you're looking at around a 3% drop in power, so that 170 HP GSR will be putting out around 165 horsepower at 9:1 compression. If you think you're going to notice a 1 horsepower drop, you're lying to yourself. For that matter, if you think you're really even going to notice the drop from 10:1 to 9:1, you are also lying to yourself. On the street there is no discernable difference in throttle response between 10:1 and 9:1, and power feels almost exactly the same.

My motor is currently sitting at a little over 10:1 compression, and if I had to do it again for a street motor I would do 9:1, no questions asked. As a matter of fact, I found a set of 9:1 Wiseco's for cheap, and it's really tempting to buy them and swap em out.</TD></TR></TABLE>

This is very accurate. I had my GSR bored to 81.5mm and ran CP 9:1 pistons for 6 months before boosting, and noticed no difference at all in driveability, acceleration, revving, nothing. Car ran just as before, if not better.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cnydc2 &raquo;</TD></TR><TR><TD CLASS="quote">In my GS-R I have 9.0:1 Comp pistons, I blew an intercooler line off and the car became extremely slow. It was very unresponsive, maybe everyones car reacts different, I don't know. I would eat my brothers BMW with boost without I had no chance, so please don't tell me I know what I am talking about. Maybe It was the turbo in the exhaust disrupting flow, or I was running entirely too rich w/o boost,I don't know. I don't need to get flamed b/c my car reacted diff than yours, have you ever ran 9.0:1 n/a? </TD></TR></TABLE>

yeah dude that turbo was restricting the **** out of your engine..