EFI > Carb for supercharger

[big_P]

How is this done? I have a 92 Shadow TBI.

[89acclaim]

Ok I assume you want to convert to a carb with supercharger. I have a couple questions is the engine a 2.5 or the 2.2? Do you have one of the old DC kits or are you going to fit together a setup with like a M90 off of a supercoup? I have actually thought about using a M90 on my 2.5 running Megasquirt. Though I just did check some things and the M62 looks like it would be better. The M62 is off of the Xterra.

Daniel Merrill

[big_P]

It's a 2.5. If I were to do it, it'd be a complete kit from DC

[89acclaim]

Since you want to do the complete kit you will probably have to convert to carb. I haven't ever herd of someone using the tbi computer and a supercharger. I don't even think the P body ever was carb. I hope one of our few supercharged guys speaks up. It sounds like a nice project keep us informed.

Daniel Merrill

[fiat22turbo]

The top of the B&M blowers for the 2.2/2.5 can accomodate a 4-bbl carb (with some slight mods). This opens up the ability to use TBI units from all sorts of vehicles, including the Holley 4-bbl piece. Basically you'd need a throttle body and Injector that can accomodate at least 150-170hp. After that you'll need to find some one that can reprogram the TBI computer for you, or go with an aftermarket EFI solution (Megasquirt is the cheapest by far, with SDS, Electromotive, Holley and others also available)

The limiting factor for the TBI electronics is the lack of a knock sensor. Without that you'll get the privelege of replacing headgaskets or worse pistons at least once or twice during the tuning process. Megasquirt II does have an input to monitor knock, but won't actively alter ignition or fuel based on hearing knock (that's the tuner's job, LOL) The stock turbo electronics have knock built in.

In order to get any 2.2/2.5 to survive under a supercharger, it will really need to be built to turbocharged specs. The programming for the turbo computer can be altered to accomodate a supercharger. The difference in fueling style could really throw the computer off (then again, maybe not as they adapt fairly well) So basically, since the 1990 and earlier turbo computers were batch fired, you'll need to have two injectors in your TBI with impedence values that match impedence values for a set of four stock injectors. The fuel pressure will not need to be altered by boost pressure since the boost isn't pushing back agains the injectors and the usual sensors will need to be plumbing into place.

So it can be done, but requires some effort. Going with a carb seems easier, but you'll need to replace the harness with a generic ignition system (a system that retards timing under boost is critical) and then tune on the carb until you're satisfied with the results. Both ways require trips to the local dyno to tune properly. Both require wiring modifications. Since they made turbo Shadows and Sundances up to 1991, you should be able to get those parts easier than finding a way to go back to a seperate system for ignition, fuel, voltage regulation and speedometer signalling.

Hope this helps,
Stefan