MIGHTYMOUSE

iTrader: (59)

just wondering how far behind I am from the rest of the stage 2 h/c guys because I decided to keep my compression low... so how much hp/tq would you expect i be down.. 10%?

I'm dynoing this sat and i'll relay the results.

[ November 14, 2001: Message edited by: MIGHTYMOUSE ]</p>

VINCE

iTrader: (1)

That is a good question.. I personally do not know.. From what I was told the higher compression is more for torque and throttle response..

Big Mike

iTrader: (4)

From what I remember I think every compression point increase is roughly 30 HP.

99 Black Bird T/A

iTrader: (4)

[quote]Originally posted by Big Mike:
<strong>From what I remember I think every compression point increase is roughly 30 HP.</strong><hr></blockquote>


I think that also depends on what cam is used too...because some cams can increase cylinder pressure by snapping the intake valve closed sooner. Good swirl and quench can make up for some of that too. I think with a good selection of matched parts an increase of 1 pt of compression might be worth as little as 10hp in the 10.5:1 to 11.5:1 range.

I think I've seen others say shaving the heads .030 is ususally worth about 5-7hp and about .5 in compression.

Big Mike

iTrader: (4)

Sounds right. I have another topic going where Nineball also mentions how the cam effects compression. How is torque affected?

2quick4u

[quote]Originally posted by Big Mike:
<strong>From what I remember I think every compression point increase is roughly 30 HP.</strong><hr></blockquote>

It is more like 15 lbs-ft torque increase at the flywheel for 1 full point of compression on a 5.7 liter engine.

[ November 15, 2001: Message edited by: 2quick4u ]</p>

VINCE

iTrader: (1)

So I was right about the torque thing.. Wow!

MIGHTYMOUSE

iTrader: (59)

so when you say one full point.. you mean 10.0 to 11.0 not 10.0 to 10.1 correct?

thanks for the info.

Terry Burger

iTrader: (4)

1 point of CR is probably around 7-8rwhp/10-13rwtq, assuming you have sufficient octane to make the higher CR work.

Jason99T/A

iTrader: (21)

[quote]Originally posted by MIGHTYMOUSE:
<strong>so when you say one full point.. you mean 10.0 to 11.0 not 10.0 to 10.1 correct?

thanks for the info.</strong><hr></blockquote>

One full point is going from 10.0:1 to 11.0:1.

2quick4u

[quote]Originally posted by MIGHTYMOUSE:
<strong>so when you say one full point.. you mean 10.0 to 11.0 not 10.0 to 10.1 correct?

thanks for the info.</strong><hr></blockquote>

Yes, and your welcome.

Colonel

When you raise compression you raise TQ across the entire RPM range. This means more HP too. Just wanted to clarify that you CAN'T raise TQ at a given rpm without raising HP since HP is a function of TQ and RPM.

2quick4u

[quote]Originally posted by Colonel:
<strong>When you raise compression you raise TQ across the entire RPM range. This means more HP too. Just wanted to clarify that you CAN'T raise TQ at a given rpm without raising HP since HP is a function of TQ and RPM.</strong><hr></blockquote>

Very true Stephen.

99 Black Bird T/A

iTrader: (4)

How high (assuming you got the needed octane) can you raise the compression and still pass emissions test? I know some sniffer test look for NO and as compression rises and combustion temp rises the NO emission will go up?

2quick4u

[quote]Originally posted by 99 Black Bird T/A:
<strong>How high (assuming you got the needed octane) can you raise the compression and still pass emissions test? I know some sniffer test look for NO and as compression rises and combustion temp rises the NO emission will go up?</strong><hr></blockquote>

It is true that as CR goes up, cylinder pressure, and exhaust temp go up. And as exhaust temp goes up, NOx or oxides of nitrogen also go up. If you have a working EGR system and 3-way catalyst, that should take care of it. Also if you run a cam with more overlap than stock, it will help lower exhaust temps and NOx production.

VINCE

iTrader: (1)

You answer is?