Any ideas why I'm running lean?
 

Prior to the install of my Magnuson supercharger my AF ratio came down to around 12.4 or so after 2K RPMs and stayed there. After installing my supercharger and downloading the provided tune I'm seeing high to mid 13's all the way up to 3K RPMs.

New 42# injectors were installed with the supercharger
Fuel pressure at the manifold is about 52-55#s
I've been all over the motor with starting fluid looking for a vacuum leak..didn't find anything.
Had someone with a scanner log my LTFTs during a street run, they are negative for the most part.
Called Magnuson, they say that they've been sending out the same tune for years. Supposedly no way I could have gotten a bad one.

Here's my dyno chart. We stopped at about 3.5K due to the AF not coming down.
http://www.spinn.net/~muncie21/dyno2.jpg

#1 - tune

#2 - what vehicle is this on? LS1 base fuel psi is 58-60...

#3 - add a rising 1:1 regulator

99 C5
 

Ooops, forgot to say what car this is. It's a 99 C5 Corvette, with a 6-speed.

That graph only goes to 3500 rpms. Where's trhe rest? A tune can fix alot of problems. Generic tunes would be nice if every car was the same. But they're not.

Ok. Just read you stopped the run. I don't see why. I've seen cars do a full dyno run with worse A/F. My a/f is awefull untill i hit around 4k. But i'm N/A. Get her tuned.

What kind of boost are you running?

Jim

..around 5#'s

Just a thought, but could your calibration on the wide band be off. Looks like the entire AFR band is a little lean. Like if it were rescaled it would be right on. It is reading over 15 afr at around 2,250 rpm. At that ratio it should almost be bogging. Have you checked or verified this with another wide band?

Good point nitrorocket. Unfortunately, I took the car to two separate dyno's (two weeks apart) and the results were almost identical. I called Magnuson today to get their opinion. They agreed that it is running lean. John (at Magnuson) said if I send him my computer he'd take a look at my tune :hail: and correct it if there's any issues. Gotta luv that kind of support. Unfortunately, I'll be without my car for about a week while this takes place.

You don't make a full pull on a blown motor when it's that lean or you may be picking up parts after the run. They were smart to stop until they figured out what's going on. My first thought is that the tune may be made for a boost referenced regulator and this one isn't.


Jody

Is 13.5 that bad on a blown motor at 5 psi?

I think eventually it'd wound it, but maybe not in one pull, especially on a dyno that doesn't load as hard as on the road/track. But it is lean. Some guys will go mid to upper 12's on A/F, but on the higher power stuff it's usually high 11's to low 12's.

Jody

I don't know that much about FI engines, but when I talked to the tuner at Magnuson, he said they shoot for 11.8 to 12.2 when they setup thier tunes. Again, I don't know why, but from my understanding 13.5 is OK for a NA carl, but not for a FI car..... :confused: