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awsome write up.

so you are running the 4.3 tb with the 2.8 injectors?

would it work with the entire 2.8 setup? and tune it as you did with the other?

on to reading your other links this is happening to my 20r that wont run right with any carb we put on it
 

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Discussion Starter #44
It would work fine with the 2.8l injectors after you do the BPW calculation to figure out the fueling. I used the 4.3l injectors because i had them, and none of the 2.8's at the junkyards had the injectors for some reason.

Edit: I'm running 4.3 injectors in a 2.8 throttle body.

One more word of wisdom: a truck that doesn't run well with a carb probably won't run well with a TBI conversion. Bill on the Binder forum preaches this pretty regularly.
 

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I'm probably headed this route with my 20R/22R hybrid too. How was the 4.3 throttle body too big, did you just lack fine low speed throttle control? Or was there just too much throttle movement at the top end that wasn't used? The 2.8 TBI only put out 125hp, guestimating my hybrid is doing an honest 140.

That AutoProm costs over $300, ouch. Would you recommend that versus megasquirt?
 

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Discussion Starter #46
I'm probably headed this route with my 20R/22R hybrid too. How was the 4.3 throttle body too big, did you just lack fine low speed throttle control? Or was there just too much throttle movement at the top end that wasn't used? The 2.8 TBI only put out 125hp, guestimating my hybrid is doing an honest 140.

That AutoProm costs over $300, ouch. Would you recommend that versus megasquirt?
You pretty much nailed it. It just moved too much air, and didn't seem to respond very well. It's like running a 850cfm on a stock small block chevy.

Be aware that the 4.3, 5.0, and 5.7 throttle bodies are the same CFM rating and have the same bore sizes, just different injectors. Most internet sources state that they are anywhere from 390 to 490 CFM, which is just too big for these Toyota motors.

I looked into the megasquirt, but honestly I liked the simplicity and tried and true OEM TBI computer. It's been hacked for a while now, and there's plenty of support for it. The wiring harness plugs right in, and all the circuit boards and components are automotive grade and coated in a fancy film that helps dissipate moisture and dampen vibrations. Plus if my ECM dies for some reason, a replacement is cheap (albeit I have to mod it for a 28 pin EEPROM first).

I like the AutoProm a lot. It works great for an all in one package. The price is a little steep, but I've already used it on another person's conversion, so it's not just sitting on the shelf.

Now that I've got the experience, I might try to use a 1bbl 2.5l throttle body next. It uses one injector, and is smaller and easier to adapt to the Toyota manifold with a homemade adapter.
 

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Thanks for the info. For others' benefit, the throttle valve sizes are here . Specifically "The 2.8L has a 1 3/8" bore, 4.3, 305, 350 have a 1 11/16" bore and the 454 has a 2" bore".

Here's some simple calculations, comparing these to the 22R carb (primary barrel is 32mm and secondary is 40mm). Converting from metric to SAE, I get these numbers (in square inches) for the cross section size at WOT:
22R - 3.29
2.8L - 2.96
4.3L - 4.47
 
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