Don't remember if I read it somewhere or was in a conversation with someone, but the topic was fuel injection and it was said that GM's TPI was not sequential injection. That is, each time a cylinder requires fuel and a pulse is sent to the injector, all injectors get the same pulse. Sequential injection sends the signal only to the injector that needs it, at the correct time. I'm bringing the subject up here because I'm not sure if this correctly and completely describes SPFI. It would make sense SPFI would be more efficient, but does it offer better performance as well? Are any 3rd Gens equipped with sequential injection from the factory? Thanks.

 

Batch fire is the setup your talking about for TPI's. All four cylinders on one side get their pulse at the same time.

I beleive that GM looked at this as a way to simplify wiring and controls.

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KevinP92Z
92 Z28 383 SLP cam,SLP headers,SLP 2ontheLeft,Trick Flow TW heads & pistons,Edelbrock base,Accel SuperRam,52mmTB,Scat Crank & forged ConnRods,MSD 6AL,SLP convertor,Baer 13/12" Track,Moser axles,Hotchkis,Genuine GM 3.42s,SLP HD Torsen,17x9" chrome SS rims
96T/A w/SLP Ram Air,SLP 2ontheLeft, Bilsteins, Baer, Hotchkis, Genuine GM, Torsen
76 4X4 Blazer 400TPI project

 

Sequential fire wasnt until the 1994 LT1's, so no, no thirdgen has sequential fired injectors. With TPI, all 8 injectors fire at once. Yes, thats the truth.

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87, do a search on "SPFI". This subject has been beaten to death: but it does little, if anything, for performance. Good for emissions and slightly better gas mileage.

Not worth the cost of the investment. Search the old posts with the "search command" and you'll know more about SPFI than you ever cared to know.

 

Well no.. not all 8 injectors fire at once. Only 4 at a time in each bank

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92 Z28 5.7
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No, all 8 injectors fire at once. We went thru this once before with GM Tech. He looked it up in his books, and I looked it up in my Helms manual. There are two injectors banks, with 4 injectors in each bank, but the two banks are tied together inside in the ECM. Why do you think Diacom only shows one injector pulse width instead of two?