Hi all, I just wondered about injector sequence. Do the injectors fire bank to bank or simultaneously on tpi? What about mpfi? I thought if you had a distributor then the injectors were fired simultaneously, meaning all at the same time. Then if you had dis ignition then they fired bank to bank? On tpi and mpfi does all GM rwd engines fire the injectors simultaneously? thanks

 

Feel free to correct me, but as I understand it, TPI is a type of Multi Point Fuel Inj. Early TPIs fire all injectors at the same time. Later models fire banks of injectors (SD??? or later?). SFI or sequential fuel injection can use a crank trigger type ignition and fires each injector separate.

 

Our injectors are batch fired. Cylinders 1, 3, 5 and 7 fire together on one batch then cylinders 2, 4, 6 and 8 on the other batch.

 

TPI is batch fire as stated I believe the first year for sequential fire FI is 1996.

 

All TPI from 85-92 is batch fired. All 8 injectors fire at the same time. Let me say that again. ALL 8 INJECTORS FIRE AT THE SAME TIME Ok? The 92-93 LT1 is also batch fired, 8 injectors at the same time. 94 and up are sequential fired, each injector only fires when it needs to fire.

The computer has two different injector lines, but they are joined internally. The computer sends one signal to fire. The wires split into two banks of injectors. But all 8 still fire at the same time.

 

About time someone got it right.

 

There are alot of tech articles that use the words-group-batch-bank to bank- simultaneous , and they use these words interchangeably, which can cause confusion, at least it can for me. I read in a chevy fuel injection manual that all tpi and pfi, the injectors fired simultaneously, meaning all at the same time not bank to bank. The statement wasn,t model specfic. So if he was talking about all chevy v engines with pfi, then he was wrong. If he was talking about only rwd engines, then that may be correct. Does anybody know of a rwd v engine with pfi that fires the injectors bank to bank? I just wondered, I don,t know of any. thanks

 

Sorry, I assumed since they were grouped in two sets that they were alternatly fired. Having them all firing at the same time doesn't seem to efficient to me.

 

If you look at the none votec heads,
all the injectors just point at the runner's floor. So the fuel lays around, batch fire or SEFI.

What atomizes the fuel is at overlap when the blast of the last bit of exhaust blasts *back* at the fuel at the then opening intake valve.

I just changed from SEFI to batch fire, and actually found better performance with the batch. With really big injectors (55#/hr) it does alot of good to fire them 2x as often to help again with some more atomization.

 

I,m not trying to argue with anyone, I,m just trying to learn. I saw a tech article that said 92-93-5.7L-LTI, that the injectors were fired bank to bank. Injectors 1-3-5-7 fired at one time and injectors 2-4-6-8 were timed differently. I don,t have the vin code for the engine. My old manual just goes to 92, but it lists two 5.7L engines. One is vin8 and has a distributor the other is vinJ and has dis ignition. I figured if one fired bank to bank then it probably is the one with dis ignition. The one with the distributor would probably fire the injectors simultaneously, all at once. I just thought excluding TBI and SFI that any GM v engine whether v6 or v8 or fwd-rwd that if the engine had a distributor, then the injectors fired simultaneously-all at the same time. If the engine had dis ignition then the injectors fired bank to bank. I don,t know of any GM v engine whether it,s a v6 or v8--fwd or rwd--- that has dis ignition that is not bank fired. Again this excluding TBI and SFI. I don,t remember where I saw that article on the LTI. thanks