So... I'm in the process of rebuilding a cast 225 (I was hoping for a forged, but oh well) and i have been looking into a hei upgrade. I have a parts suburban (93?) Sitting around that would be a great donor, and the more I think about it, I think about the tbi setup it has... I'm not sure how hard this is, but its all free to me! I don't have a clue about megasquirt though, and from the little bit I of info I have found, I have to have it (which would make it about the only big expense, right?) Being 17, I suppose I could pick up on it pretty quick tho.

Which brings me to my next pondering... how would running tbi with boost be that much different than with a carb? I mean, eventually my thoughts of boost my actually formulate into something, and it would be pretty rad if I could use the same setup.

Just tossin some thoughts out there for the masses to ponder and chime in on

Brandon

The part that I find a plus is that you don't have floats to collapse, passages to drill, other stuff to index or goof with...but I know that you may need to get a 2-3 bar MAP sensor for it as I think the standard NA EFI TBI is set for 0-1, and you may need to change out the injectors.

Hopefully someone else can chime in on this, I know the above from references in the Holley EFI literature, since they had provided a number of throttle bodies to the big three in the late-80's-early 90s (for better or worse).

-D.Idiot

Never once did the floats ordeal cross my mind...

Or the MAP sensor, for that matter

The throttle body is off a 350, and I believe I read somewhere that the throttle body stayed the same until the 454, and that all they changed were the injecter sizes for the different engines, if that means they will be big enough, I don't know...

Brandon

Extreme penny pinching and EFI don't mix. Even with a complete donor car ts all the little things that come to bite you - fittings, plumbing, wiring, etc. All the incidentals will end up costing plenty more then the main bits.

My understanding from Matt is that at some point,all the Mega squirt ecu's were shipped with a 3 bar map sensor. if you buy used,then this is an issue. If you buy new,then not.
Sam

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The tbi for the chevy / gmc were the same size for 4.3L, 5.0L ,5.7L,
The injectors were different in the amount of flow. I think the fuel pressure regulator spring is different also. I have rebuilt about 30-40 of these.

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Fast is fine but accuracy is final. You have to learn to take your time ... in a hurry
- Wyatt Earp

2.5 bar, actually - MegaSquirts with 1 bar sensors are pretty rare. 3 and 4 bar versions exist as well as options. DIYAutoTune.com never sold one with an internal 3 bar, but a couple other vendors did.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Thanks Matt. I knew it was more than 1.
Sam

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The MS can be had/made for <$100, just get a schematic and start buying parts. Used are out there but for what they are made of, over $100 is BS. There is a new player in town if you are really DIY, check out diyefi.org Jaguar 0.6. If you were not on the mailing list you missed out on this batch but 0.7 is on the way. Lots of support (not as much as MS) but its a superior product across the board for peanuts as you build it, no kit. ECU plus board was $35! itll take another $70 in parts to complete but you get a USB interface, superior layout, built in safeguards from shorts or other installation errors, and a smart ass board administrator that know his stuff as he designed it. Not MS3 sophisticated, but its not $700 either. They are going to offer a DIY wideband controller too as soon as the article is published. I think TBI is a decent alternative, still have long runners and fuel puddling to contend with but its simple, almost bolt on and can do boost with MS or other custom controller. I believe you can even flash the GM ECU for boost from a service. Go for it. use injector selector to find your injector size. Get one for the most HP you think youll ever run I say about 250hp. Thats 2.5X a stock slant. about 42lb/hr if you have 4 injectors or 84lb/hr for 2.

What all would I really need to pull? The throttle body unit, the injectors, a stand alone ecu and chip... I'd probably need some of the factory wiring, but does anyone know how much? Anything else I should know?

I think TBI has most of the sensors built into the TB itself. maybe an intake temp sensor and a coolant sensor. I got a Edelbrock Pro-flo and the only external sensors it has is coolant and air intake temp. everything else is in the TB itself. At minimum youll also need High pressure fuel pump off a ford truck (external, EZ to get off frame..maybe too high as TBI only needs like 24 psi? regulator is built into TBI too) TBI, those 2 sensors, ECU and a return line to the tank. Get as much harness as you can from the sensors, if you got a doner, you can probably get the entire harness and just tie up the excess. That would be very cheap. look at a GM TBI site for necessary stuff.

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I didn' t buy it, I built it.....