I need Engine Builders Help..
Thread Starter
Instructor
Joined: Jun 2001
Posts: 100
Likes: 0
From: St. Petersburg, Florida
I need Engine Builders Help..
I tried to ask this question, but it seem I was talking to only two people and I could not get a vendor to get in on the discussion.. I want to know what is the maximum compression I could run on a LS1 346 cu with a cam 221/221 558/558 lsa 112..? I have heard people going up to 11:5.1, but I was wondering if I could run 11:7.1 and still run 93 octane. I have no problem sending my computer back to Ed Wright for adjusting. I just want to know what kind of benefits if any or what are the negatives of doing this?
Le Mans Master
Joined: Aug 2000
Posts: 5,529
Likes: 1,943
From: Austin Texas
Re: I need Engine Builders Help.. (vmoore)
If you assume that power goes up linearly with compression, you are talking less than 2% change (for the better) in HP.
But HP does not go up linearly with compression. The compression stroke is not an iso-thermal event, it is an adiabatic event (pressure and temperature change simultaneously). Likewise the expansion (power) stroke is an adiabatic event.
Given reasonable numbers for air and vaporized gasoline and compression ratios, you should be able to achieve between 60% and 70% of the gains of the previsously assumed linear relationship. Now we are talking about 1.5% difference in HP between 11.5:1 and 11.7:1.
Is it worth it to step over the line and require "special blended gasoline"?
But HP does not go up linearly with compression. The compression stroke is not an iso-thermal event, it is an adiabatic event (pressure and temperature change simultaneously). Likewise the expansion (power) stroke is an adiabatic event.
Given reasonable numbers for air and vaporized gasoline and compression ratios, you should be able to achieve between 60% and 70% of the gains of the previsously assumed linear relationship. Now we are talking about 1.5% difference in HP between 11.5:1 and 11.7:1.
Is it worth it to step over the line and require "special blended gasoline"?
Le Mans Master
Joined: Aug 2001
Posts: 8,145
Likes: 1
From: Bradenton FLORIDA
Re: I need Engine Builders Help.. (MitchAlsup)
Great reply Mitch, the mods available without crossing the compression ratio barrier seem to be more than enough for those seeking another 10th off their time slips. :chevy
Thread Starter
Instructor
Joined: Jun 2001
Posts: 100
Likes: 0
From: St. Petersburg, Florida
Re: I need Engine Builders Help.. (MitchAlsup)
Then it sounds like I should go no higher than 11.5:1. I might take another persons advice and go 11.3:1 to be safe.. Thanks Mitch
Thread Starter
Instructor
Joined: Jun 2001
Posts: 100
Likes: 0
From: St. Petersburg, Florida
Re: I need Engine Builders Help.. (2FST4U)
Sorry about that... It seemed like you were trying to interest me in a solid roller cam. I asked you about pricing, but I never rec'd a email from you..
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