power diff. btwn 10.3 and 11.3 compression?
Thread Starter
Joined: Nov 2001
Posts: 10,018
Likes: 51
From: Virginia
power diff. btwn 10.3 and 11.3 compression? 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>
I'm dynoing this sat and i'll relay the results.
[ November 14, 2001: Message edited by: MIGHTYMOUSE ]</p>
Re: power diff. btwn 10.3 and 11.3 compression? 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..
Re: power diff. btwn 10.3 and 11.3 compression? [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.
<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.
Re: power diff. btwn 10.3 and 11.3 compression? Sounds right. I have another topic going where Nineball also mentions how the cam effects compression. How is torque affected?
TECH Regular
Joined: Nov 2001
Posts: 450
Likes: 0
From: Tullahoma TN
Re: power diff. btwn 10.3 and 11.3 compression? [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>
<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>
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
I can shift faster than you.
iTrader: (21)
Joined: Nov 2001
Posts: 5,133
Likes: 0
From: Baton Rouge, LA
Re: power diff. btwn 10.3 and 11.3 compression? [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.
<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.
TECH Regular
Joined: Nov 2001
Posts: 450
Likes: 0
From: Tullahoma TN
Re: power diff. btwn 10.3 and 11.3 compression? [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.
<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.
TECH Senior Member
Joined: Nov 2001
Posts: 9,246
Likes: 3
From: Troy, AL
Re: power diff. btwn 10.3 and 11.3 compression? 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.
TECH Regular
Joined: Nov 2001
Posts: 450
Likes: 0
From: Tullahoma TN
Re: power diff. btwn 10.3 and 11.3 compression? [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.
<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.
Re: power diff. btwn 10.3 and 11.3 compression? 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?
TECH Regular
Joined: Nov 2001
Posts: 450
Likes: 0
From: Tullahoma TN
Re: power diff. btwn 10.3 and 11.3 compression? [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.
<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.
