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Understanding the limits of Pump Gas

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#1
Hey all, I'm new to forced induction and tuning in general (previous cars were V8s, and carbureted) so I'm trying to understand the limits on making power with 91/93 oct. (I know more power can be made on E30, but that's not the information I'm looking for here).

I'm budgeting for an S280, and after reading the build threads here I know that turbo caps out around ~265 whp on 91 and ~285 whp on 93, but my question is why? Is it a fueling issue (solvable with upgraded injectors and fuel pump)? Lack of boost (solvable with a bigger turbo or increased pressure)? Camshaft (solvable with a more aggressive profile)? Displacement?

Knowledge is power and I'm looking to learn.
 


Jabbit

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#2
Stock fuel system caps out at 300whp, give or take about 5%. You need aux fuel or upgraded pump/injectors to get much past 300whp.
 


M-Sport fan

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#3
Also, lower available octane fuel requires less boost and/or timing in the tune to prevent total grenading of the engine, resulting in less power output.
 


SteveS

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#4
The basic limitation to increased boost, other than fuel/air supply, is cylinder pressure and temperature. You can only boost pressure so far before you get lethal detonation. Octane rating is the measure of resistance to detonation. The higher the octane, the greater resistance to detonation.
 


flbchbm

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#5
The basic limitation to increased boost, other than fuel/air supply, is cylinder pressure and temperature. You can only boost pressure so far before you get lethal detonation. Octane rating is the measure of resistance to detonation. The higher the octane, the greater resistance to detonation.
EXACTLY why you don't waste high-octane in regular cars, cycles and mowers...

Sent from my SM-N960U using Tapatalk
 


OP
Snark_1
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Thread Starter #6
So could I make more power on a lower octane with increased fueling from bigger injectors/ high flow fuel pump?
 


Dpro

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#8
Hey all, I'm new to forced induction and tuning in general (previous cars were V8s, and carbureted) so I'm trying to understand the limits on making power with 91/93 oct. (I know more power can be made on E30, but that's not the information I'm looking for here).

I'm budgeting for an S280, and after reading the build threads here I know that turbo caps out around ~265 whp on 91 and ~285 whp on 93, but my question is why? Is it a fueling issue (solvable with upgraded injectors and fuel pump)? Lack of boost (solvable with a bigger turbo or increased pressure)? Camshaft (solvable with a more aggressive profile)? Displacement?

Knowledge is power and I'm looking to learn.
Ah I actually pulled 284HP on 91 out here in California close to sea level at 25-26 lbs of boost on a S280 tuned by Adam at Tuneplus FWIW.
Of course you are in Denver so you are not going to see those numbers seeing as you‘re 1 mile above sea level. I am guessing you will see somewhere in the 250’s with a S280 there.
 


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