Compression Ratio - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


General GM Chat When starting new posts, please specify YEAR, MAKE, MODEL, ENGINE type, and whatever modifications you have made. Chat about all things GM (and related cars). Off-topic stuff should be in the Lounge, and all Model specific mechanical problems should be posted in the proper forum.

Reply
 
 
 
Thread Tools Search this Thread
Old 11-26-2006, 04:44 PM   #1
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Jul 2006
Location: Oshawa, Ontario
Posts: 38
Thanks: 0
Thanked 0 Times in 0 Posts
tgboulianne is on a distinguished road
Default Compression Ratio

Was wondering if anyone knows what the MAX compression ratio is for a '99 SSE (L36 - non supercharged).

I'm putting on a turbo eventually and I need to know the max PSI my engine can handle.
tgboulianne is offline   Reply With Quote
Old 11-26-2006, 09:35 PM   #2
Senior Member
True Car Nut
 
Join Date: May 2003
Location: Holt, MI & Lima, OH
Posts: 3,022
Thanks: 0
Thanked 0 Times in 0 Posts
dbtk2 is on a distinguished road
Default

I guess I don't understand the question your are asking here.

The compression ratio on the stock L36 bottom end is 9.4:1. Without touching the bottom end obviously you can mill the heads/block and/or use thinner head gaskets.

But, if you're going turbo, I think I'd leave the compression alone because 9.4:1 is actually a pretty nice compression ratio for something with boost.
dbtk2 is offline   Reply With Quote
Old 11-26-2006, 10:39 PM   #3
Senior Member
True Car Nut
 
Join Date: Mar 2005
Posts: 2,688
Thanks: 0
Thanked 0 Times in 0 Posts
dillcc is on a distinguished road
Default

I think he'* asking what the max PSI he can run is, which if I understand correctly, is a lot different than the compression ratio...
dillcc is offline   Reply With Quote
Old 11-26-2006, 10:52 PM   #4
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

Until we get clarification, pretty high boost levels have been achieved on stock heads. I've hit 15psi myself, but my compression ratio is only 8.5:1. My effective compression ratio is FAR higher however, when the boost pressure is taken into consideration.
willwren is offline   Reply With Quote
Old 11-26-2006, 10:59 PM   #5
PopaDopaDo
True Car Nut
 
popatim's Avatar
 
Join Date: Jan 2005
Location: NY
Posts: 4,957
Thanks: 0
Thanked 0 Times in 0 Posts
popatim is on a distinguished road
Default

How does that effect stock internals? or have you upgraded those too?
popatim is offline   Reply With Quote
Old 11-26-2006, 11:55 PM   #6
Senior Member
Certified Car Nut
 
Join Date: Oct 2003
Posts: 19,756
Thanks: 0
Thanked 0 Times in 0 Posts
1993 SLE is on a distinguished road
Default

Quote:
Originally Posted by popatim
How does that effect stock internals? or have you upgraded those too?
the bottom end of the L36 will be fine....but an upgraded valvetrain will let him maximize the mods
1993 SLE is offline   Reply With Quote
Old 11-27-2006, 03:31 PM   #7
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Jul 2006
Location: Oshawa, Ontario
Posts: 38
Thanks: 0
Thanked 0 Times in 0 Posts
tgboulianne is on a distinguished road
Default

My bad! I thought that compression and PSI were one and the same. So I guess what I really wanted to know was what the MAX PSI my engine can handle.

Stock L36
tgboulianne is offline   Reply With Quote
Old 11-27-2006, 03:54 PM   #8
Senior Member
True Car Nut
 
Join Date: May 2003
Location: Holt, MI & Lima, OH
Posts: 3,022
Thanks: 0
Thanked 0 Times in 0 Posts
dbtk2 is on a distinguished road
Default

Max PSI as in max boost pressure or max PSI as in max cylinder pressure????

If you're talking about max PSI as in boost level, then it depends completely on what type of power adder, intercooler, and cam profile and whatnot. Just an M90 on a basically stock L36, you'd probably only want to run like 5-6psi. Do some valvetrain mods and exhaust mods and unintercooled you could probably pull off like 9-10psi on pump gas. Throw an intercooler on and 13-14psi shouldn't be that hard to do. My setup is making around 13psi right now with an intercooled M90 setup.

However, for your turbo setup, it all depends on what the turbo is, what you are doing for an intercooler, and your cam profile and the rest of your exhaust and whatnot. The bottom end will not give you any problems until you are making A LOT of power. So that shouldn't be the issue as long as you get everything else done right. Head gaskets will start to give you issues somewhere around 18-22psi. If you go with like MLS gaskets and head studs though, you shouldn't have any problems unless you get VERY serious.

Is this some type of a turbo kit you are getting or are you doing it yourself or what?
dbtk2 is offline   Reply With Quote
Old 11-27-2006, 07:13 PM   #9
Senior Member
Certified GM nut
 
Join Date: Feb 2004
Location: MI
Posts: 2,246
Thanks: 0
Thanked 0 Times in 0 Posts
Logan is on a distinguished road
Default

Yeah, I'm curious as to what size turbo you planned? Any ideas on the BOV yet? Where can you get the exhaust manifolds for this?
Logan is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Intense Pistons - 9.5:1 Compression Sol Performance, Brainstorming & Tuning 1 01-20-2004 05:48 PM
How do Compression Ratios work? macho_mike21 Performance, Brainstorming & Tuning 6 01-11-2004 05:47 PM
Engine Compression egladman 1987-1991 2 01-04-2004 02:13 AM
Compression Testing Dylansdad 1992-1999 1 09-24-2003 07:44 PM
Stock Compression on 95 SSEi? Bassplayincrowe Performance, Brainstorming & Tuning 8 07-18-2003 06:19 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 09:27 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.