setting the FMU

[po-po 5.0]

Originally posted by pablo
Dear PO PO 5.0
Glad to hear that you have a CL calibrated unit for those big injectors...36 injectors are big, and you would need a good flow heads, and some more to handle that kind of fuel.
By the way,...you are using the white restrictor and check valve on the procharger FMU? if not you would have problems when you decelarate the engine, since the fuel pressure would be very high once you lift your foot form the pedal.
Take care
pablo

The motor has some worked iron GT40's, and a 513/529 cam so I think I meet the airflow requirements of those injectors. Yes I am using the check valve in the hose going to the FMU.

[paluka21]

I honestly don't beleive the 36# injectors are too much for what you have, alot of times cars can go lean quite easily especially when being untuned. I would say until you can get the car on a dyno and have it tuned, keep the fmu on.
As for the setting, pretty much what everyone else has said, a fuel pressure guage is a good tuning tool, set the base fuel pressure, then work with the FMU with throttle blasts. I would first of all make a mark on the FMU dial so you can tell how far you have turned it, and it gives a good reference point. Try working in 1/4 turn increments to see how this works for you.
I wouldn't imagine you need a whole lot more than 65psi of fuel pressure under boost, but again its all up to the tune.

good luck
Dan

[po-po 5.0]

I don't plan on EVER removing the FMU. Even when I do get a wideband I'm still leaving the FMU setup for a 1:1. In the meantime, I do have a fuel pressure guage its just the boost gauge I'm lacking which should be here tuesday. Hopefully this will clue me in on what kind of fuel pressure I should be seeing. I kinda wonder if this thing really makes any boost up here in CO.

[klondike93]

I live in Thornton Co, and with the 9# pulley I'm getting 6# @ 5500. Where are you at po-po?

[po-po 5.0]

Originally posted by klondike93
I live in Thornton Co, and with the 9# pulley I'm getting 6# @ 5500. Where are you at po-po?

Boost gauge should be in tomorrow. I'll tell ya what I make when it goes on.

[WA2FAST]

Question... why do you never plan on getting rid of your FMU? You sound like you feel very strongly towards that... is there a reason?

[po-po 5.0]

Originally posted by WA2FAST
Question... why do you never plan on getting rid of your FMU? You sound like you feel very strongly towards that... is there a reason?

From my research it would appear that having a 1:1 boost reference is benefical to tuning. I guess I'm not adamant about it, but it seems silly to buy a boost sensitive regulator when I already have an FMU.

[WA2FAST]

I totaly agree... you don't need a boost sensitive regulator at all with an FMU, that would be like putting 2FMU's on your car. The reason I was asking about the whole FMU thing is because FMU's are just a band-aid for an in-adaquate fuel system... if you have the proper injectors, you don't need a FMU at all and there is no 'blip' in the curve because of a sudden spike in fuel pressure that happens with even a 1:1 setup.

[po-po 5.0]

I have a gss340, and 36# injectors. In reality I don't need the FMU at all at my 6 psi, but from my research, I've seen that having the 1:1 aids tuning? Although, I guess 99% of chipped, blown cars don't even worry about it.

[WA2FAST]

Nah, it doesn't aid anything at all. If you are having your car tuned on a dyno and a custom chip burned, you don't need one at all, you will find that tuners have to tune around FMU's. Generally the FMU is good if A) you don't have the fuel system to support your power level (which you more than likely do), and B) if you are not going to get it dyno tuned. You may want to think about that, I have a feeling you will be better off if you don't need it.

[kobra94]

i just had my 94 D1SC dynoed yesterday, we did not use the FMU, as my tuner described the fmu as "a band aid on a bullet wound". it does the job, but there are better ways to correctly fix the problems. I pulled 470rwhp at 5500rpm and the curve was still climbing when the 42# injectors maxed out. so i need a fuel system upgrade now.

[WA2FAST]

Nice! Good work... sounds like your car is gona' be a beast when it's all said and done. Funny thing, is that is how I describe FMU's to people that don't understand why they are and are not needed... I say it's simply a band-aid on an inadaquate fuel system... if you have injectors/fuel pump/rails/lines that can handle the power load, you don't need anything else.

[kobra94]

BTW---- after my dyno we ended up with 50# base fuel pressure, on 42# injectors, no fmu, PMS assisted fuel curves. we maxed the injectors out at 470hp at 5500 rpms and it was still climbing. we stopped rather than use the fmu because we were nearing the danger point of explodeding the block. ken

[WA2FAST]

Yea, my car needs to get back on the dyno (soon to come), but my tuner drove it and said that it has to be close... he is concerned about that as well.