Inliners International Forums General Discussion Hi Performance Fuel Injection for a 250???

Ive been thinking about adapting a Holley Commander 950 TBI unit onto my 250, probably the 400CFM unit. Has anyone ever used the holley projection on their engines? any other fuel injection ideas? i know clifford just came out with a MPI unit for a 250 but its still kinda pricy...

I'm building a fuel injection system for my 250 right now. Check out this site for some back ground:

http://www.bgsoflex.com/megasquirt.html

I've already assembled and built the controller. I ordered the testing and simulation setup so I can experiment with tuning this thing long before it gets onto the engine. I really don't have a whole lot of money right now and I haven't had time to do the custom work yet in my college machine shop. Eventually I intend to either redrill a stock manifold for injector bungs or create a new manifold out of a select number of machined pieces and sheet metal. This is another great site:

http://www.sdsefi.com/tech.html

The piece on building a surge tank is especially nice considering we're going to EFI from nothing at all. You have to consider more than controls, sensors and actuators- there's the rest of the system.

wow thats a lot of info, but way too involved for me at this point in my life, but definitely looks good for a future project. i was looking for a more immediate option like the projection or clifford units. anyone have experience with these?

I've heard great things about the Holley Projection. I haven't personally used it but there seems to be some pretty good potential in it.

I ran a Holley projection unit on a Chevy 400 SB in my '64 Ford 4WD for several years. It was a pretty crude system -- only a TPS , vaccuum, and temp sensors, but I liked it. Now you can get a full feedback system to go with them. The only drawback to them that I see is if you travel much, and something breaks, parts are not readily available. Also parts are high. A while after I sold my pickup, the computer went bad. It was running full rich. The replacement computer would have cost 4/5 of what the whole system cost me. Needless the guy that owned it decided to go with a carburetor.
If you can get a system from something that has a 4.3 with TBI you can adapt it to your 250. That way parts are available and relatively cheap. That is what I have done on my 302. Joe

I've heard some real positive kudos on Megasquirt. It's been used with great success on some of the new Wayne customer engines, and on rod projects using the 4.2 Vortech L6. Uses many OEM GM parts, very tunable and cost-effective. There also seems to be a growing user base who are online and willing to share and help. Definitely worth looking into.

heres another question about the holley projection unit. the commander 950 series is fully programable via laptop and comes with 4 injectors mounted of course above the throttle bores. now im not very knowledgeable about the electronics but doesnt it stand to reason that you could disconnect the injectors, make a fuel log, by bypassing the fuel intake on the tbi unit and then actually mount different injectors with of same size right into the manifold for an mpi system? it would still recieve the same info from the computer wouldnt it and therefore work?
http://holley.com/HiOctn/ProdLine/Products/C950/C950TB/950-23S.html
heres a link to the 650 cfm unit.

On port injection, the injectors are timed to the intake stroke on most systems. The TBI systems are not and they spray all at the same time. Does this make sense?? I think you would need to program them differently. Joe

On the other hand there were a number of good port injection continous flow systems. It would seem the idea is workable anyways.

joe,
even if all the injectors on a tbi spray at the same time, would it matter if it was just on top of the throttle bosy or in the ports? i mean, it does make sense as to why it wouldnt but thats how a tbi unit or even a carb works anyway, basically by supplying constant fuel based on engine load, right? so why would it matter if the injectors were above the throttle body or in the ports? i mean i realize that if fuel is sprayed into the valve pocket while the valve is closed its useless but the valve opens and closes so fast wouldnt the effect of fuel collecting in the pocket be pretty limited?

Both systems work OK, however, the TBI systems are cheaper, simpler, make less horsepower, and don't get as good fuel mileage. The timed vs. untimed(drooler) systems don't seem to make a whole lot of difference in the long run, and if you have a siamese port engine, i. e. stock head Chevy or GMC, the timing doesn't make any difference like you said.

It will be useful to see how the new system that Wayne is using works out, especially on a stock head engine. I think there are enough people out there that some volume savings might occur.

Ed Pruss
Longmont, CO

I have one of the earlier Holly Pro-Jection systems mounted on a 261 in my (my wife's) 40 Chev convertible. It is the 2 barrel version and seems to be working quite well so far. Good mileage and excellent response. The current versions are a great deal more involved with Oxygen sensors and computer programming. I talked with a fellow at a recent car show who had a 261 powered coupe with the latest Holly setup and he was still working on the calibration. He was an engineer and from looking at the calibration curves, computer hookups, etc...it might help to have a degree in engineering! Could be a lot of fun however.

Yeah, fuel injection is a mixed blessing in that sense. The fuel systems are more powerful but on the other hand they get so much more complex. Personally I find fuel injection to be a good thing cause I understand it and I'm good with that kinda electronic stuff. But I know quite a few people are kinda alienated but it. Thankfully there are still enough people making insane power with carbs that they're respected

P.S. I'm in first year engineering