Denis.V

TPI v/s MPFI: What is better?

Is interchange possible between both systems?

The same questions for TPI/MPFI & SFI....


Thanks in advance.


Denis V.

TomP

Woah; it's been a while since I remember (accurately) the differences, but...

TPI and MPFI are both batch fire. As in, the right bank of injectors fires, then the left bank, then back again. (SFI is when the injectors fire as they're needed per cylinder, but I think even those go into batch mode at WOT.)

The TPI runners ("tuned port") are tuned for a specific air flow... I think lower RPM power. They can run out of steam at higher rpm's, and that's why some guys ditch the factory TPI for an aftermarket carb, or aftermarket injection.

Both can use MAF or speed density, depending on the year. MAF systems got the cold start injector, SD's didn't. All TPI v8's got a knock sensor, only the SD 3.1's got one. All used HEI, the MPFI systems got remote coil HEI in '85, TPI waited until '87.

I can't think of other differences... and I don't know anything else about sequential systems...

DreamState21x

I thought TPI's fired all injectors at once.. Im not sure about that just remember reading it somewhere on here..

Soft Taco2

do you know if it would be possible to get a chip or something that will convert TPI to SFI? Should be pretty easy IMO, since most of the SFI critical parts are there already.

Denis.V

A good question, but note the following:

SFI is better than TPI?

ECM software would need modifications, O. K.?

ECM send the electrical signal by two terminals (connectors): One for the 3 right injectors and other for the 3 left injectors. Modification to SFI needs 6 (V6) different wires for 6 signals at different time.

Soft Taco2

i know, but its not very hard to put 2 wires on each connector and run them to a new ECM. (if they make one)

1991tealRSt-topGuy

the crankshaft position sensor is a key player in SFI, which your guys' motors dont have

i'm sure one can be adapted, but i see no real point in the funding such a "guinea pig" would require

1991tealRSt-topGuy

i guess i should also add that a newer PCM would be required since each injector would obviously need its own spot on the PCM

plus a custom chip, plus..............might as well swap in a newer FWD motor, they have the CKP sensor and PCMs that support SFI and DIS and..............

i cant rationalize spending $1000+ on a 25HP upgrade, but hey, all i do is throw money into the trash myself, so who am i to talk

Denis.V

Good,

I've the FWD MPFI motor with CKP sensor + DIS + 3 coils (2 terminals/each) + Diag. Scan. software (under construction) + PROM progr. sofware.

What I need? What PCM could be?

Could I get additional 25 HP moving from MPFI to SFI?.



Thanks,

Denis V.

TomP

The crankshafts in 87-up 2.8's, including Gen I and Gen II (fwd), have the center counterweight which the DIS crank sensor ran off of. I'm not sure if the Gen I cranks are notched for the DIS sensor, though. If not, I'd imagine that either (A) it could be done, or (B) a Gen II crank could be dropped in without any modification.

Doward

Pretty much. Just pop in and go.

As for all that trouble to swap in an engine... I don't know, I'd go either 3.4 myself, or straight to an LS1 or something like that, for all that trouble!

Doward

oh yeah...

TPI and MPFI's fuel delivery system is exactly the same. Batch fire fuel injection.

The TPI (Tuned Port Injection) has long runners, tuned for low end torque.

The MPFI is more of a straight shot, if you've ever looked at the runner flow across the intake.

SFI vs Batch Fire.

Only difference is slightly better fuel economy, and better emissions until around 3k rpm, when almost ALL SFI switches to batch fire mode.

There is no performance difference in the fuel system - the intake, perhaps, but not the fuel delivery.

BackInBlackGP

So, which one is this? MPFI or SFI?

Doward

mpfi