I've got a 93 LT1 with a lighting supercharger on it.

Its a speed density setup W/FMU.

I thought i would just share my experences with it, due to the snappy onslaught of boost anytime you press more than 25% throttle its been hell to get the AE right.

The VE tables have been kinda screwy too, its amazing how much that blower boost effeciency before you even really touch on boost.

Oh and the PE tables are doing some crazy things too, It looks honestly like i've got to dump a good amount of fuel at lower RPM then fan it out at higher to acheve a good total AFR. Almost like you have to lead the FMU

I've only got a few tunes threw it, the VE is perfect now.. AE is real close and i just started on PE which is really far off It is perfect until about 4K where it dumps rich

 

You may want to forego the FMU. One nice thing about a roots is that it is a positive displacement device. If not running a lot of boost the standard 1 bar SD tables often work well. This is because the blower always moves the same amount of air at a given RPM & TPS.

Going to a '7749 w/a 2bar MAP would be a better way to go. Then the actual level of boost may be accommodated. I just don't like FMU's. . .

RBob.

 

I've never had a problem with a FMU. and speed density LT1 theres almost no other way to do it.

Its roots, but not as consistant as you think. Maybe in Alpha N mode

7749 isn't a option because its a opti spark car.

 

If you like the FMU, and it works for you, all is well.

But, depending on what ratio it's running, your really asking alot of it.

While a standard FPR just tracks the manifold vac., a FMU might be asking for 4-6-8 times the change in FP. And when you into AE/PE the DC of the injectors can be fairly high. So you asking the pump to drastically raise the pressure, with injectors at a 50% DC, and to increase the pressure in about 10' of fuel time.
Takes a healthy pump to do that. And all the while if your seriously in it, the situation gets worse much quicker. And any decrease in FP capacity, just kills everything.

I'd lean toward larger injectors.

BTW, one of the next things I'm going to be doing on my car is using a fixed FPR, ie no vac referencing. For the above reasons.

 

i've already got 30lbs injectors in the car. along with high psi inline pump.

It should have good capability for fuel right now