two weeks ago i went and got my car dyno'd and tuned. the car makes 270 at the wheels at 10 psi, but between 4500 and 6000 rpms, the car leans out to 17.5:1, and after 6000 rpms it comes back down to 11.5:1. the guy that did the tuning said its because my fmu is taking a while to catch up wid the motor. my setup is a built 95 gsr, t3/to4b turbo, 255 fuel pump, missing link, fmu, and 450 dsm injectors, and also a vafc. is there any way i fix this problem without goin with a hondata or standalone???

 

How long has it been since you placed your fuel filter?
It could be the fmu or a restriction elsewhere.I don't see why the fmu would work fine up to 4,500 rpm then not work,then all of a sudden work again after 6krpm....there is nothing to them

 

I dont think that it is the FMU... i bet the guy didnt tune around the VTEC point well enough... do you have a VAFC??? if so you should be able to cure most of this whith that..

Brian

 

For one thing, how is it that the FMU can "take a while to catch up" with the motor? I was under the impression that the FMU was a simple rising rate FPR... if that is true, then the fuel pressure will go up as the boost goes up, until you reach full boost, at which point the fuel pressure will remain constant. It seems to me that at 4500 rpm's you would be at full boost already, so the fuel pressure should be where you need it.

Did you take fuel pressure readings? If not, install a FP gauge and see what it says.

Why not just richen the VFAC up in that range?

 

dump the fmu and get an engine management system (haltech, aem, hondata).

 

thanks for your info guys, imma get me a new fuel filter, and see what happens. i plan on gettin a hondata pretty soon.

 

I hope your not in boost when the motor leans out to 17.5:1. If so I wouldn't drive the car until it is fixed or at least no boost. You are waaaayyyyy out of the safe range as far as air/fuel ratio goes.

 

why do you have a vafc, 450 injectors, AND an fmu? Those injectors are to big for an fmu, unless it's like 4:1 or 6:1.

 

that is the VA special. its been made very popular by inline pro.

i cant answer why u leaning out, but I wouldnt take "fmu catching up to the motor" as an answer. might want to get a lower rise rate in that fmu, u r probably out of ur fuel pumps efficiency range. or try adding a high pressure inline. just ideas, i really dont know why u would only lean out from 45-6000 but get rich after that.


[Modified by DIRep973, 11:06 PM 1/6/2003]

 

What are your fuel setting on the v-afc around that rpm range?
Most likely the v-afc is set wrong. I.E leaning the mixture out at that rpm ......

 

I agree, I think that the VAFC is wrong. Or, even if it is not wrong, it must not be "right." I don't see why he can't just richen it up in the rpm ranges where it is running too lean.

 

I think someone didn't know what they were doing. I would tell everyone about the person that tuned it. He shouldn't be allowed to touch anyone's engine just for doing that. IMO.