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Can't Decide TBI - TPI - MPFI

dave w

dave w

1/2 ton status
Joined
Oct 31, 2008
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I really can't decide which to use (early 70's 1/2 ton 4x4)? I have the budget for any choice. I know how to program the PROM for any of the choices. The TBI is from a 454, but I'll use an Edelbrock 2101 carburetor dual plane intake with a TBI adapter (if I go that route). The TPI and MPFI will use the underhood Vette 7727 ECM. Anybody know how to get a 7727 to run a TBI?

Thanks in advance for the input!
dave w

TBI.jpg

TPI.jpg

Edelbrock MPFI.jpg
 
I wish I had 3 different types of injection just kicking around..... well I've got two of them... :) I vote for the MPFI just for that added touch of efficiency I guess..
 
i guess it depends on truck usage... TBI is the obvious choice for a truck imo, low rpm torque, etc.... it's the route i'm probably taking on my megasquirted 383...

but i haven't ruled out MPFI, mainly cuz i have about a 1/2 dozen marine MPFI intakes kicking around the garage staring me in the face... :doah:
 
I think that TBI can not be beat unless you are out for top Horsepower.
TBI = simple, reliable, cost efficient, easier to tune, and good torque. Additionally, parts are everywhere.
 
Merc has every style of MPI you can imagine... from standard carb looking intakes with rails/injector down each side to exotic style plenum intakes with centered rails...... all depends on the model, Magnum, Horizon, etc.....


can't find many good pics online, but here's an idea....


4.3 standard rail style..

DSCN4626-BIG.jpg





typical Horizon setup....


20113.GIF
 
I dunno which one to go with...but I gotta say your photochop skilz are amazing!! :bow: :haha:

Rene
 
that horizon style looks pretty badass, that standard rail 4.3 looks like the vortec style only with actual injectors instead of that poppet valve spiderweb POS they had on the 90's vortec trucks.
 
yeah, some of the merc mpi plenum setups would be pretty sick in a vehicle.. there's another style that I can't find a pick of.. it's definitely a little more "compact" than the horizon setup.... magnum setup, pretty badarse....

other than rpm range, the other thing that keeps leaning me back to tbi is cost of 8 injector vs 2.... a set of factory merc injectors runs about $1600 list.... we replace em alot with the bosch's tho, $900....
 
thats crazy for the cost, wouldnt they be the same outside dimentions as most automotive type injectors?

generally isnt the RPM range really low too? A friend of mine put a mercruser grind TBI cam in his TBI buggy when he built the new engine a few months back and loves it.

I think he said it quits making power at 3500 RPM too.
 
yeah, it's a standard GM injector size...


ya gotta understand, what i do at work is vastly different than what i personally might do.... :wink1: i HAVE to run that kinda stuff...... warranty issues, coast guard, etc...

i'll try to remember to bring the camera to work tomorrow....
 
doh, missed that other part....


most of the merc FI cams are set up to run at about 3500 rpm's... the mpi's will spin 4600 all day tho, tbi's, 42ish.... you can definitely feel more snot from the mpi's in that last 1000 rpm's than you do in the tbi's....

my understanding of mpi is that it definitely helps out the top end more... wet vs dry manifold, etc...
 
I decided to go sequential fuel injection. Here is a picture of the parts pile I'm going to use to convert the Edlebrock MPFI to a LS computer.

dave w

DSCN3052.JPG
 
Just an update on the '0411 PCM progress. The before wiring harness pic. Then the after wiring harness pics.

dave w

DSCN3090.JPG

DSCN3094.JPG

DSCN3096.JPG

DSCN3095.JPG

DSCN3092.JPG
 
damn Dave, that looks sexy....subscribed!
 
Way too much time and patience for me.
At least your running a good computer, now you need the LS engine to match it.
 
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