Obviously edelbrock makes a MPFI conversion kit, but has anyone ever considered using 90% of that hardware, ditching the intake and fuel rails, and using it with something like a Holly Stealth Ram instead for a simplier (overall) TPI conversion? The reason for ditching the edelbrock setup would be because of the limits in the Throttle body unit flow, and even if you invested in a Turbocity or Holly unit, you would almost be 1/2 the way to a HSR as it is cost wise.

I read the FAQ on doing TBI -> TPI swaps and that just sounds like a nightmere.

Any thoughts?

 

If you want to do a TPI conversion but are not willing to go through the hassle of a complete rewire, check out Street and performance. They have easy swap harnesses and kits. Makes the job alot easier.
http://www.hotrodlane.cc/

 

I think edelbrock uses an external piggy back system to fire all 8 injectors using the TBI ecm. It's a crutch at best. I suggest just ditching the TBI ecm and swaping over to a 730. I know it looks pretty complicated to swap an entire wring harness or to repin and add extra wires to you exsisting harness, but it will be much better than the eldelbrock setup. Besides the stock edelbrock tune probably wouldn't even begin to run anything other than it was designed for so your back to square one. Might as well bite the bullet and do it right, with DIY prom tuning.

 

eh... it was just a hyperthetical idea - I'll probably just stick with TBI.

 

730 computer and I read a post a while back saying that the TBI ecm harness can be repinned for a 730 really easily. Something like just a few wires needed changes. Do a search on it.

 

I would seriously be suprised if it was that easy (I think everyone would be jumping ship) but if it is, I'm impressed... I'll look around, and if I find it, I'll link it in this thread.

 

Well, even if it is fairly easy that still doesn't warrant jumping ship. Unless you're making serious HP and I mean serious, you don't need to go MPFI. TBI suffices for most buildups. And swapping is very expensive. A lot of people assume swapping to TPI is a good swap but it really isn't worht much in the HP department on a stock or modified engine and costs a lot of money. Don't gett me wrong though, I do like the MPFI route when dealinig with big horsepower. You reach limitations with TBI about as quick as you reach limitations with TPI, but everyone just works with what they have.

 

Well, my primary concern was fuel mileage. Right now I'm at 14.5-15 combined MPG out of my 5.7. Ouch.

I found that post though:
https://www.thirdgen.org/techbb2/sho...i+to+730+repin

TPI units shouldn't be hard to come by for under $200, and after $150 in junkyard parts - maybe it is something to look into in the name of $2/Gallon gas?

Then again, I have no idea how to read his pin comparison chart, and this is all bench talk at this juncture anyway.

 

If you want gas mileage, you can get great gas mileage with TBI it just has to be tuned up right like any other kind of induction. You say its a 5.7, what are the specs and what computer are you running?

 

A 730 won't run TBI but if your wanting to swap to MPI then yes repining the harness isn't that bad, then all you have to do is add the extra injector harness.

If gas milage is what your after, then you need to look into tuning what you have. Or even tuning what your swaping to. If your running a 350 on a 305 chip your gonna be very surprised how much better it will run when tuned properly. It seems all the *******s around here love to swap 350's in place of 305's. I bet I've helped out about a half a dozen people who couldn't make it across town without stoping at a gas station. Surprisingly the guys that swaped from a 4.3 to a 350 didn't have any problems. Guess because each cylinder was the same size as a 350 and since the injectors are fired at each dissy ref pulse the extra fuel was added with the two extra ref pulses.

 

"A 730 won't run TBI but if your wanting to swap to MPI then yes repining the harness isn't that bad, then all you have to do is add the extra injector harness."

Well, I know that, lol. That was the only reason the 730 ecm was brought up. I never had an intention on running a 730 for TBI (common sense) or MPFI until you brought it up. It's a decent idea that I will have to consider though.

Anyway - I'm running a 7747, stock tune, stock motor, correct chip. It runs GREAT, smooth as could be, with new plugs, wires, cap and rotor, etc. Just the mileage stucks - and mind you that's with 2.73 gears.

Where would any "Tuning Germlins" be found besides the ecm?

 

Other than an old or crapy (bosch) O2 sensor most of milage problems were the result of a loose nut behind the wheel.

I did have a tps sensor go on me and not trip a code, it was ocilating real bad and envoking the pump shot all the time. The motor ran like crap and I had the VE curve tuned around it so it wasn't evident through the slow aldl connection that our TBI ecms have.

 

I'll check the TPS... as it is, I'm never above 2400 RPM....