Ohk i just want to know if a 350 with the tbi setup and computer off of a 305, but with no o2 sensor would run rich or lean. The lean would come from the 305 computer, but the missing o2 would bring out the rich. Which would it be lean or rich?

 

Why would missing the O2 sensor make it rich? Without an o2 sensor, the ECU would be stuck in open loop mode, so it would be making no corrections.

This means it would go hard lean whenever you hit the throttle and go rich whenever you dropped off the throttle (I had this experience with a 305 ECU in a 383). A very bad way to run a car.

The effect would be worse if you are running a SD setup, but I'm not sure if TBI's were SD or MAF?

 

TBI is speed density and yes running the motor like this would be a bad idea. Just get the right parts for your application.

 

I ran on limp a few times and it was not pretty. Do not confuse limp mode with open loop. OL is no NB02 feed back with NB02 in place and functional. When I ran open loop the car ran very well somewhat rich(wide band) but gas mileage sufferred significantly. as stated get a 02 sensor in place. Delco is the preferred and heated is a good idea.

 

I say, you are running lean, very lean. The ECU is supplying fuel for 305 cubic inches when there's actually 45 more cubic inches. If you keep running the engine like this you'll fry a piston.

I'm in the middle of an EFI conversion and got these for my phone. It was really helpful to size my injectors and fuel pump. Check it out:

https://play.google.com/store/apps/d...efimathandroid

https://itunes.apple.com/us/app/efi-...5062?ls=1&mt=8

https://itunes.apple.com/us/app/efi-...5726?mt=8&uo=4

 

You can run current injectors and TB just increase the fuel pressure 15-20%. A tune will be required.

 

Don't worry guys I'm not running the car! I just need to know if it is safe and apparently it's not, but can I still start it up and let it idle? I'm in the process of getting a 350 prom, but now I'm hearing that ill need 350 injectors as well? I'm not worried about the gas mileage just yet, just need it to run safely

 

A source for injectors is DCTrumpet here as member or FIC fuel injection connection. May be able to do an exchange?

 

Yep you can let it idle, but again, not for long. TB throttle bores are the same for a 4.3, 5.0 and 5.7 but injectors are not, run the numbers and you'll see how different the fuel requirements are.

Although it's possible to bump up the fuel pressure and make 5.0 injectors flow like 5.7's you are still limited to stock 5.7 specs (no bigger cam, heads, etc) let alone the stress over the fuel regulator's diaphragm. An adjustable fuel pressure reg. was made to fine-tune the system not to convert a plow horse into a race horse (read the apps info and do the math!).

If bigger cam or better heads are in your plans consider 75lb/hr injectors originally installed on 454 TBI big-blocks.

 

Hey a lot of this stuff is kinda confusing, can I run a prom chip from a 5.7 truck? Or does it need to be a car, if so a tbi 350 only in the caprices and stuff? I'm starting to think its less of a hassle to go carbed, despite the gas mileage

 

You said you have a TBI computer from a 305, but that is too vague as there are more than one. I believe trucks, Fbodys, and Caprice all use diffrent ECMs and you cannot simply swap chips between them. The stock TBI ECM for Fbodys is the 8746. If you don't have the 8746 then I'm not sure if its going to be a plug and play deal. You would have to do some research on that. Check out the stickies on the TBI board.

IMO switching to carb because its less of a hassle is like switching to a typewriter instead of using a computer to write an essay because its less of a hassle. Sure both will work, but in the long run which one is really less of a hassle?

 

TBI ECU's are almost the same across platforms from the hardware standpoint. They receive different PNs bacause the application is different. Using a 350(5.7L) chip will make the things even worse. The 5.7L chip is considering 5.7L injectors, in fact there's a value inside that tells the program the injectors are for 5.7L.

ECU pin position is almost always the same for truck and car ECUs with minro differences here and there. Stick with a truck ECU since there's more support for these except maybe for Camaro units.

I would not recommend using a chip in a different ECU (to avoid further confusion on service numbers and calibration). It may seem difficult at first but believe me, what you are going to learn by performing the swap is priceless.

Check your ECU's PN 'cause there where some ECUs used from 4.3L V6s to 5.7L with the only difference being the chip between them (16168625 for example).

 

What is the service number off the ECM? 122****

 

Lol I forgot to mention my car is a 92 rs

 

Could I just take the whole computer from a truck? Would it be hard to install? This question is only because I might be able to get one for free

 

https://www.thirdgen.org/forums/dfi-...tbi-350-a.html

you might want to check into that

 

I believe truck has an entirely different ecm,how would you run everything else on your car? Use your 746 ecm

 

8746 supports IAT sensor. There are better ECU's(faster/newer) however. I would stick with what you have for now. Not sure if this was stated but it would help to have a donor prom of same transmission. If not you can work around that. As stated a cop car eprom is a 350/auto(8746) but again not absolutely necessary if you are going to tune the eprom. There is a setting in the eprom for CID/inj size/fuel pressure called "BPC".