need advice on a/f ratio
11-03-2009, 01:32 PM
#11
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
Posts: 13,090
The best way is to take them off the car and put them into a flow tester that not only checks the pattern of the spray (blocked or broken pintels), but the volume and resistance of the injectors (clogged injector or shot injector).
Since it's only happning at higher RPMs it will be difficult to diagnose clogged injectors without the proper equipment. If it were at idle or low throttle it would be easier. Yes there is a way to test under those conditions but it's dangerous and not entirely conclusive. You'd be working with electricity and pressurized fuel in an uncontrolled environment.
You could run a tank of 89 or higher fuel with Techron fuel injector cleaner through it before your next dyno.
Other than that I would wait until you see the actual readings before jumping to conclusions. I'm still thinking pressure is the issue here. Get the WOT fuel pressure and a snapshot of the STFT and LTFT at the same time. Most equipment that reads that data can take the snapshot for you. Those three bits of info will speak volumes.
Since it's only happning at higher RPMs it will be difficult to diagnose clogged injectors without the proper equipment. If it were at idle or low throttle it would be easier. Yes there is a way to test under those conditions but it's dangerous and not entirely conclusive. You'd be working with electricity and pressurized fuel in an uncontrolled environment.
You could run a tank of 89 or higher fuel with Techron fuel injector cleaner through it before your next dyno.
Other than that I would wait until you see the actual readings before jumping to conclusions. I'm still thinking pressure is the issue here. Get the WOT fuel pressure and a snapshot of the STFT and LTFT at the same time. Most equipment that reads that data can take the snapshot for you. Those three bits of info will speak volumes.
11-03-2009, 01:39 PM
#12
6th Gear Member
Join Date: Apr 2007
Location: California
Posts: 10,468
Are you sure his a/f gauge is correct? 17:1 is EXTREMELY lean and most engines won't even run at that at part throttle. I'd be extremely skeptical of that being the actual a/f ratio without it stumbling and cutting out all over the place.
11-03-2009, 03:16 PM
#13
5th Gear Member
Join Date: Jul 2003
Location: United States
Posts: 3,451
What is your fuel psi when it goes lean? Probably just need tuned.
I've ran one up to 16.9:1. Tuning them to run very lean at cruise is fine. One of mine is set at 16.7:1 at cruising load. What I do is start at 16:1 & keep working my way up 1 point until it starts to surge, then back off 2 or 3 points. You want it to run as lean as possible at cruise load for the best fuel economy. For forced induction i always aim for 11.7-12.3:1 & n/a 12.7-13:1
I've ran one up to 16.9:1. Tuning them to run very lean at cruise is fine. One of mine is set at 16.7:1 at cruising load. What I do is start at 16:1 & keep working my way up 1 point until it starts to surge, then back off 2 or 3 points. You want it to run as lean as possible at cruise load for the best fuel economy. For forced induction i always aim for 11.7-12.3:1 & n/a 12.7-13:1
Last edited by FoxGT; 11-03-2009 at 03:18 PM.
11-03-2009, 05:06 PM
#19
The Rogue Mod
Join Date: Feb 2006
Location: Maryland Sucka's!!
Posts: 21,918
11-03-2009, 06:27 PM
#20
Thread Starter
Join Date: Sep 2008
Location: texas
Posts: 32
they connected a wideband where the oxeygen sensors where, havent noticed any ehaust leaks. my car was an automatic then i put a manual in it but left the auto computer in the car. do you think that might have something to do with it?