MPI Conversion Project

MPI Conversion Project

Began: June 6, 2002

Objective: To design and implement a MPI (Multiple Port Injection) system for the 2.2L NA (Naturally Aspired) engine.

Reason: I need more power, and I have come to the conclusion from multiple angles that the limiting factor is the intake manifold and the TB (throttle body).

Project: My initial thoughts after doing a ton of mods, and getting a lot of gains, is that I still need more power. The next step I thought was supercharger, turbocharger, etc. but the more I thought about it, the more it goes away from the roots of the Shadow project (...to show people that you can cheaply modify a 2.2L NA engine into a descent street machine for not very much money). So I began thinking what can I do, and every time a plan was hatched it all came down to two limiting and intertwined problems. One, that the intake manifold (is crappy) is a huge limiting factor with its design and airflow characteristics, and two, the throttle body can not push enough air. Even after doing massive porting jobs on both, they both are limiting everything on the engine. My initial thoughts were of taking the intake manifold off a 2.2L Turbo and modifying the TB plate to hold my TB (the 2.2L NA TB) or use the 46 or 52 mm turbo / V6 TB and modify my ported intake to hold the larger TB. Then it hit me, what is the third limiting factor that I am semi-successfully fixing with the addition of 2 extra injectors....fuel delivery. When I realized I started conceiving a way to make the 2.2L NA TBI into an MPI system.

Status: Ongoing and acquiring parts (update 06/6/2002)

This all came about because we are considering purchasing a Camaro with a V8 305 cid TPI (Tuned Port Injection) engine, so I have been doing a lot of back ground work on the TPI system (I like the Mopars, this is my wife's #1 choice, and I told her if it's American I'll consider it, and unfortunately Mopar hasn't made a V8 Sports car in years, and my wife subscribes to the displacement/cylinders means power theory). The TPI system is really neat, I didn't fully understand that fuel injectors in multiple injector systems don't want to spray fuel right through the open valve into the combustion chamber; but time it just right as to spray the fuel onto the back of a burning hot valve as that the fuel has just long enough to atomize before the valve is opened. I always knew that TPI used the batch firing method (fire all the injectors on one side of the V at a time), but I discovered that batch firing and SEFI (Sequential Electronic Fuel Injection) produce the same amount of power in any given engine. SEFI times each injector to each cylinder, firing the injector at just the right time, this only improves idle quality (low rev quality actually) and emissions.

After thinking this over for a while I started thinking about the intake on the 2.2L Turbo engines. They bolt right onto my 2.2L NA TBI without any modifications, and I could then use the turbo's larger 46 mm TB, or get a 52 mm TB off a 3.0L V6. The more I thought about it, the less SEFI seemed attractive. I honestly don't care about idle quality, and the minute difference in emissions interested me even more, and all the work I would have put in to design a control system for the four fuel injectors wasn't worth the time for idle quality. I figure I can just batch fire all four injectors on the 2.2L Turbo intake with the help of some electronics triggered from the original TBI fuel injector control line.

I should only need a turbo intake manifold (and new gasket), a V6 TB, a turbo intake system (or I may make my own, not sure yet, probably start with the turbo and later modify / make my own), turbo fuel rails, turbo fuel regulator (though I may need to get an aftermarket one) and four turbo fuel injectors. All these parts should be pretty cheap being pulled from a local junk yard, and all inline with the cheap mod mantra that I have followed for all my other Shadow mods. The electronics will be really easy to make, I will only need a simple transistor switch on the old TBI fuel injector control line to drive all four turbo injectors. I doubt the computer would be able to drive all four turbo injectors from the TBI fuel injector control line, so taking the burden off the computer is probably the best route.

My concerns; the possibility that the fuel injectors may be to large for everyday driving of the Shadow. I use two extra fuel injectors currently, but they only trigger at a certain TPS voltage (they are staged and never turn on below about 3000 rpm). This may present a problem, but I think I can use an adjustable fuel regulator to solve this issue (if I still use my two extra fuel injectors in front of the TB). If not, I may have to find some other Bosch injectors to use instead of the stock turbo ones (I'm pretty sure I can find some other ones that will work, all Bosch injectors are pretty much the same, or at least one of three varieties).

I will update you when/if anything changes (ideas, experiments, models, etc.).

Status: Most parts acquired and some modeling done (update 07/1/2002)

I have the intake manifold (1989 one piece), the fuel rail, the turbo intake air box and assorted hoses. I have located four good turbo injectors and a turbo fuel regulator, but still have not been able to find a 52 mm TB (I haven't been looking very hard though). If I can't find one within a few weeks I may just end up using the 46 mm turbo TB. I have done some extensive modeling and I think I may be able to squeeze out 25% more horsepower with this mod. The increase in airflow will really, really help. I am not as worried about the turbo injectors as I use to be, I think I may be able to use them at stock fuel pressure and still be able to drive normally. I am now starting to get real antsy about doing this mod, I can not wait to find the last few parts!

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