air fuel question...
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 2,014
Likes: 80
From: San Antonio Tx
air fuel question...
Just installed 4.5 pulley and took the 5" pulley off the f1c procharger... looking at my wideband air:fuel drops to 10.0 at wot prior to new pulley it was 10.5... the car has 60lb inj and meth inj whats the lowest ''safely'' the AF can drop to... car has stock shortblock and internals still as well as restrictor plate... how far off will my tune be now assuming previous tune was extremely conservative ''safe to drive till I can get it retuned''???
Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,123
From: Dyer, IN
Just installed 4.5 pulley and took the 5" pulley off the f1c procharger... looking at my wideband air:fuel drops to 10.0 at wot prior to new pulley it was 10.5... the car has 60lb inj and meth inj whats the lowest ''safely'' the AF can drop to... car has stock shortblock and internals still as well as restrictor plate... how far off will my tune be now assuming previous tune was extremely conservative ''safe to drive till I can get it retuned''???
Instructor
Joined: Jan 2011
Posts: 176
Likes: 1
From: Buffalo Grove Illinois
10 is a pretty rich A/F ratio on a forced induction motor. I have kept my FI cars tuned between 11.4 -11.7 to make the most power.
Youre not going to hurt the motor, by washing the cylinder walls with excess fuel at 10.0 but you will most certainly be down on power a bit.
Youre not going to hurt the motor, by washing the cylinder walls with excess fuel at 10.0 but you will most certainly be down on power a bit.
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 2,014
Likes: 80
From: San Antonio Tx
This is my first F/I car so I'm new to this af setup I had a 436CI stroker N/A car made 600HP... the reason for the meth is to ''stay on the safe side'' last thing I need is to have to build the 402 sooner than planned ... that's the winter 11' project 
Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,123
From: Dyer, IN
Amazing how many tuners differ on the use of meth. Most tuners around here don't use it, unless someone builds a high boost LS1/LS6. Whatever makes you feel comfortable......I guess.
Tech Contributor
Joined: Jan 2007
Posts: 19,341
Likes: 1,123
From: Dyer, IN
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 2,014
Likes: 80
From: San Antonio Tx
I went from 2-3 lbs to 8-9 lbs boost today, I cant imagine +18lbs.... my supercharged cobra was running 25lbs :-) this at 2-3lbs feels stronger than it.. then again the ms4 cam helps some...
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
Melting Slicks
Joined: Aug 2004
Posts: 2,237
Likes: 9
From: Springhill FL
Thats because boost is not universal across different cars/setups. Its all about flow. A huge turbo/blower at 3psi can flow more than a tiny turbo/blower at 50psi
I used to love it when guys with an SRT-4 @18psi were convinced they would be faster because my Built/D1SC vette only ran at 11psi.
I used to love it when guys with an SRT-4 @18psi were convinced they would be faster because my Built/D1SC vette only ran at 11psi.
Safety Car
Joined: Jun 2004
Posts: 4,353
Likes: 22
From: Bella Vista Ca
Most go with an AFR of about 11.5 for boosted cars. At 10 you are very safe. You are obviuosly leaving a lot of power on the table. You could also burn up your CATS at that AFR, if you are running them. Most widebands don't go lower than 10.0, you could be even richer.
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 2,014
Likes: 80
From: San Antonio Tx
No cats :P kooks LT headers bb bullets... sitting at lights around the city a/f is 15-15.7 but at times it jumps past 18 is this normal for fI cars???? I think to fix all these af issues best bet is to fallow thru with the dyno tune next week and see what comes of it...
Instructor
Joined: Jan 2011
Posts: 176
Likes: 1
From: Buffalo Grove Illinois
The only A/F you need to watch is while at wide open throttle. The A/F will be all over the place while at idle or partial throttle. When you have the pedal down all the way, that is when you watch the A/F ratio.
Remember, before you hit the boost, the engine is running like any naturally aspirated engine and will have a much leaner A/F from say 13.0 - 16.0 which is normal under partial throttle.
Remember, before you hit the boost, the engine is running like any naturally aspirated engine and will have a much leaner A/F from say 13.0 - 16.0 which is normal under partial throttle.
