TBI with Bosch TPI injectors ECM?
 

Which GM ECM would you use to fire this link?

http://cgi.ebay.com/ebaymotors/ws/eB...category=33558

Since it's only 4 injectors, what size injectors for 475hp?

If it all worked out, you could do one of these for about the same price as a Holley 950 TBI.
But it would be all custom. Especially the tuning. ;)

Wow, that's a pretty trick lookin setup! FOr that price though, I can buy a used TPI complete, and start building that.

As for injector size, I would thiunk around 50lb or so. There's a formula out there somewhere to calculate it.

If you were to use high impedance injectors, you could use a 730, but the low impedance injectors, I think you would need a different injector driver for.

Here's a little bit on a driver board for the app.

https://www.thirdgen.org/techbb2/sho...hreadid=168041

Re: TBI with Bosch TPI injectors ECM?
 

You'd have to use a 1227749 ecm, setup as used in the Turbo Sunbird application to get the injector drivers correct. You'd have a choice of 55 or 72 PPH injectors to make your HP. The 55s would get you about 400.

The 55s and 72 are peak and holds.

And it looks like it might be from Australia, so figure on a long wait to get it. BTW, the prices on the injectors on the page they link too are about 2x normal.

Grumpy,
Could one use a TBI ECM and an external injector driver for p/h's?

I suppose a 749 would be easier though, and just setup the code for a V8. What memcal would someone use in a situation such as this? Would you use a 730 memcal and knock sensor?

This is sounding like a more do-able idea the more I think about it! I don't think I'm gonna be trying it right now, but I'm gonna keep the guy's link on the TB's. They look to be of pretty high quality (although I'd have to see one up close to really be sure!)

I have Vortec heads. A TBI style will fit any 4bl intake obviously. So TBI style or Holley/Edelbrock are the options. Unless I find a used LT4 intake. :cool: There are cheaper options I've been told. The best bang for the buck after reading Grumpys' posts would be a Holley SR. (Thanks Grumpy) Which I would prefer. But I don't want to get heads, EFI, and an intake at the same time. The best I can do is new 200cc Toplines at about $700 and my valve train. I also have a BBC I want to EFI after my SB. If I do two engines with my own chip, the cost and time involved becomes very attractive compared to buying two new Holley systems. Not to mention the satisfaction of DIY.:D

Anyway, I'm a little confused on the injectors. A few links will suffice or:

Is a Sunbird TBI or TPI?

I read another post about using the 749 for a boosted app. Can the Sunbird version support this or even be converted to 8 injectors? Which Memcal? Bird?, Syclone?
I might go with a blower on a future engine.

With my combo, does the Memcal really matter?

What style injectors are stock TPI? P&H?
Is the pressure for the flow rating normally 38psi? Exceptions?

What style injectors are stock TBI?
What is normal pressure rating, 12 or 21 psi?

I thought if I ran 50lb TPI style injectors at a higher pressure it would work out even if I'm optimistic on the HP.

How much difference is there between a true Bosch injector and a Bosch copy? I was looking at the Enlightning post by ski_dwn_it and noticed the price difference between TPIS and Accel. Summit has 4 Holley 50lb universal hi imp injectors for about $300. #522-5004. http://www.holley.com/HiOctn/ProdLin...A/InjKits.html

Sunbird is TPI 4 Cyl. Turbo that is being discussed.

There are people using the 749 on V8 boosted apps. I'm not sure on the Memcal, that was a question I had!

I would think the Memcal would be important, it has the limp-in stuff in it, and has part of the stuff for the ESC.

TPI stock apps. use saturated injectors (Not P&H). and approx 38 PSI is the STOCK pressure. I think they are flow rated there also (not sure though.)

Stock TBI is a P&H. Don't recall the pressure, but I think it's like 12-15.

The rest of the stuff will have to be answered by a search, or someone else chiming in..... Along with verifying what I have written. Chech out the DIY Prom board and most, if not all of this stuff has been discussed. I just wish I could retain all of it in my feeble little mind!

Thanks. I'm planning as I learn. The searches slow things way down. And I lack patience. ESC??? Off to the archives. :)
Here is a smidge more on the 749 if you didn't know.
https://www.thirdgen.org/techbb2/sho...hreadid=199705 :)

Could you?
Yes,
Is it the best answer,
No.
The P4 series of ecms are a generation newer and a bit more advanced. There is a thread on the DIY PROM list about changing injector drivers in a 749 to run 4-6-8 P+H's

730 for 8D code would work.

BTW, don't forget the Port injector is 2.4 ohms for the P+H and the TBI P+H's are 1.2 ohms.