Max Pump Gas Boost Question- aka- Why is the LS1 boost inferior?
01-08-2008, 10:31 AM
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Max Pump Gas Boost Question- aka- Why is the LS1 boost inferior? Can some explain why many smaller displacement OHC engines (4g63 , S R T4) can run much higher boost levels (20lbs) on pump gas than our larger LS based engines? I know they typically have lower stock CRs (around 9:1) but if you built a forged (even though the stock 4 bangers aren't) 9:1 LS motor could you run 20lbs of boost all day and not worry about detonation and still achieve decent fuel economy and drivability off boost?
I know there are many other factors that play into this question (e.g. lifting heads, etc) but I look forward to everyone's opinion/knowledge.
I know there are many other factors that play into this question (e.g. lifting heads, etc) but I look forward to everyone's opinion/knowledge.
01-08-2008, 10:41 AM
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cyl size, RPM.
smaller bores are less prone to detonation, higher rpm also reduces chance of detonation. Those small motors turn alot more rpm the your usual LSx.
But the real issue is, how much boost required to make XXX HP on certain octane. More displacement will always need less boost to make power on limited octane. Don't worry so much on psi... look at HP
smaller bores are less prone to detonation, higher rpm also reduces chance of detonation. Those small motors turn alot more rpm the your usual LSx.
But the real issue is, how much boost required to make XXX HP on certain octane. More displacement will always need less boost to make power on limited octane. Don't worry so much on psi... look at HP
01-08-2008, 10:47 AM
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The S R T 4 Neon is 8:1 compression stock.
Mitsu Evo is 8.8:1 stock.
LS1 is 10.1:1 stock.
LS2 is 10.?:1 stock.
LS3 is 10.8:1 stock.
Boost is just a value.
My current 348ci is 8:1, I could boost 20 psi easily on pump gas. I went 9.4 at 20psi.
Mitsu Evo is 8.8:1 stock.
LS1 is 10.1:1 stock.
LS2 is 10.?:1 stock.
LS3 is 10.8:1 stock.
Boost is just a value.
My current 348ci is 8:1, I could boost 20 psi easily on pump gas. I went 9.4 at 20psi.
01-08-2008, 11:21 AM
#6
cyl size, RPM.
smaller bores are less prone to detonation, higher rpm also reduces chance of detonation. Those small motors turn alot more rpm the your usual LSx.
But the real issue is, how much boost required to make XXX HP on certain octane. More displacement will always need less boost to make power on limited octane. Don't worry so much on psi... look at HP
smaller bores are less prone to detonation, higher rpm also reduces chance of detonation. Those small motors turn alot more rpm the your usual LSx.
But the real issue is, how much boost required to make XXX HP on certain octane. More displacement will always need less boost to make power on limited octane. Don't worry so much on psi... look at HP
Like Tiago. Said. Your looking at boost when u should be looking at HP.
How many of those ""Other cars"" you posted make 750rwhp on pump 93 @ 15 psi?? How many make 1000 rwhp @20 psi?? I know I do. I know Tiago does.
All boost is , is a restriction to airflow.
Most of those cars were made for boost from the factory.
We do quite well for our selves with a forged bottomend.
I hop u get what were trying to say here.
Kyle
01-08-2008, 11:27 AM
#7
FREAKING NEWBS!
https://ls1tech.com/forums/forced-induction/208864-turbo-faq.html
ok, sorry if i came across harsh, that and similar questions come up about every month, same or similar.
if you did not understand the sticky's reasoning i will try to explain
detonation for boost application comes up as heating the air up with the given octane and its flash point it will pre-ignite the hotter the air. Now talking about CFM and air volume we all know a larger bore engine generally flows better then a smaller bore engine, this in turn will lower the resistances so say for example a 3.0L engine at 15psi will be producing the same amount of CFM of air as a 5.7L producing 5psi. You could almost say (though there are a number of other factors) instead of relating the resistance (psi) before you get knock you should be comparing the CFM before you get knock, it would come across as a more apples to apples comparison.
Also another factor is the amount of power past its stock level for what it was designed for. if you turn a smaller engine up from say its original 10 psi to 15 psi you may have increase the power output an extra 40hp, now a larger engine you turn the boost up from 5psi to 10psi you could have increased its power to an extra 100hp which has the greater potential to induce knock.
https://ls1tech.com/forums/forced-induction/208864-turbo-faq.html
ok, sorry if i came across harsh, that and similar questions come up about every month, same or similar.
if you did not understand the sticky's reasoning i will try to explain
detonation for boost application comes up as heating the air up with the given octane and its flash point it will pre-ignite the hotter the air. Now talking about CFM and air volume we all know a larger bore engine generally flows better then a smaller bore engine, this in turn will lower the resistances so say for example a 3.0L engine at 15psi will be producing the same amount of CFM of air as a 5.7L producing 5psi. You could almost say (though there are a number of other factors) instead of relating the resistance (psi) before you get knock you should be comparing the CFM before you get knock, it would come across as a more apples to apples comparison.
Also another factor is the amount of power past its stock level for what it was designed for. if you turn a smaller engine up from say its original 10 psi to 15 psi you may have increase the power output an extra 40hp, now a larger engine you turn the boost up from 5psi to 10psi you could have increased its power to an extra 100hp which has the greater potential to induce knock.
Last edited by smokinHawk; 01-09-2008 at 07:34 AM. Reason: to harsh
