Guys, got a few questions, I'm new to this stuff so I could be wrong in the way I explain it ...


1. I want to get 6 psi out of my M112 Eaton blower, if I use a 12:1 FMU will that work or do I need like a 8:1 ??

2. Do i have to reprog the ecm ? if so, is it just better to convert to 749 and work without the FMU ? can 749 work with lt1 ??

3. Do I must use a boost retard box or it's not neccesary ?

4. are 21# injectors too small to supply my LT1 with 6psi of boost ?

 

The 93 ECM MAP input wont see boost, be better off with the 747 setup, you'd have to get the intake drilled for a distrib, but other than that it'd work.

th 21# intjectors, way too small, try some 30 lb svo's, maybe 24 svo, how are you planning to mount the thing to your LT1 ?

 

I'd like to keep the optispark on the my car since I got rid of all my tpi stuff including the ecm, wiring and distributor.

is there anyway to keep the 93 ecm without a FMU or aftermarket Fuel injection system that supports 2 BAR???


I'm planning on running the Eaton supercharger on top of the passenger side valve cover and have the pulley straight where the alternator is, then, relocate the alternator where the ac-delete pulley is.

 

is the 747 the later MAF LT1 ECM anyways?

 

2 options that "I" can think of:

1. Get a 94+ ecm. Convert to MAF. Then get a calibrated MAF to the injectors of your choice. I'dd say 36# and more. $$$$$

2. Get an FMU, 10:1 or 12:1. that will be more than enough to provide for 6 pounds of boost with your stock injectors.

For your timming problems build a water/alky injection sys that comes on at 3 pounds. That will prevent detonation.

Nik

 

there is that other system that allows use of injectors on the TB that sprays extra fuel for the boost, but we are just talking about a 6 pound boost right, lets not build the space shuttle. If an FMU is good enough for the blower manufacturers up to 9 lbs (and MORE!) then why not use an FMU?

 

ok well FMU might be the way to go but will it give me horrible gas milleage ???? since the fmu will be always adding fuel to the system ...

or does the blower will only create significant boost over 1800 rpm ?

 

FMU only adds fuel when there is boost just like any other type of system

 

Yeah, knew that but my question is, does a SC or blower creates boost on an engine that is at idle or when it's reving under 1800 rpm ?

 

It never makes any boost if the throttle is closed regardless of the engine RPM.

 

well put

 

1) I know several dozen people now that have eventually tossed FMUs and gone with the **proper** ecm to get the fuel and timing corrections right.

2) 749 won't work with an LT1. At least not with out getting creative.

3) Doing things properly will get you proper results, ie forget the retard box.

4) yes they are too small.

One of the real problems with the Optispark is the air gap between the cap and rotor. That eats up alot of ignition nergy and wears out parts unnecessarily fast.

Going with a Distributor and 749, would be my best suggestion.

Or
Get the old check book out and invest in a GOOD aftermarket ecm.

 

will the commander 950 work with his application?

its the cheapest one i know of, and the easiest to tune boost with. just a thought.

 

I dont see why not, I might be doing it myself...

 

Yes holley does offer one ready for the LT1.

 

you can use the syclone/typhoon ecm's

they also used a 3 bar map sensor also

they were a speed density setup also

 

What does FMU stand for?

From reading I know it bumps up fuel pressure in relation to boost at a ratio of about 6 PSI of fuel pressure per PSI of boost and is a mechanical/analog device that adds this needed extra fuel by increasing fuel pressure.

 

Fuel Management Unit.

Yes it is boost referenced, and adds additional pressure to the injectors during boost. (basicaly shuts off the return line to the tank)

Bob

 

FMU raise the fuel pressure at different factors.
A normal F?P regulator increases fuel pressure 1:1 for every one pound of boost the fuel pressure goes up one PSI.
An 8:1 FMU means for every pound of boost you get 8 pounds of fuel pressure.

There is a sometimes huge problem.

A fuel pump will generate only so much work so as you demand it to work at a high pressure, the less volume you may develope. Which means you lean out just when it is the worst time for it to.

Much better to use larger injectors and 2 bar ecm.

Saturn 5 has posted in Power Adder about just getting his car running with the twin M90s and a 749 ecm,

 

Thanks Bob and Grumpy,

Just educating myself - and planning more ways of spending money!

Gordon