• Sign Up! To view all forums and unlock additional cool features

    Welcome to the #1 Fiesta ST Forum and Fiesta ST community dedicated to Fiesta ST owners and enthusiasts. Register for an account, it's free and it's easy, so don't hesitate to join the Fiesta ST Forum today!


Understanding the limits of Pump Gas

Messages
17
Likes
10
Location
Denver, CO, USA
#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

2000 Post Club
Messages
2,237
Likes
2,895
Location
New England
#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

9000 Post Club
Messages
14,000
Likes
6,699
Location
Princeton, N.J.
#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

1000 Post Club
Messages
1,291
Likes
1,567
Location
Osage Beach, MO, USA
#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

1000 Post Club
Messages
1,567
Likes
1,314
Location
Sterling, VA, USA
#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
Messages
17
Likes
10
Location
Denver, CO, USA
Thread Starter #6
So could I make more power on a lower octane with increased fueling from bigger injectors/ high flow fuel pump?
 


Dpro

6000 Post Club
Messages
6,157
Likes
5,780
Location
Los Feliz (In the City of Angels)
#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.
 


Similar threads



Top