I thought the "Vortec" engine (255 horse 96-98) had a single electronic injector that pushed fuel through 8 lines to each cylinder, at which point there was a "popet" nozzel. If this is true, then the system would be a batchfire system, with all 8 ports recieving fuel at the same time.

The engine is listed as "SFI" (sequential FI) on the window sticker. Can someone explain the operation of this Vortec FI system? Is it really SFI, or is it a batch fire?

Second question, what power level is the intake good to? Anyone know how the runner cross section compairs to a TPI? Do the heads out flow the intake, or are they well matched? If they are matched, then it would seem that the intake is good for 300+ hp. Input appreciated.




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i know your right about the 8 separte lines going in , but i'm not sure if they all fire at the same time. sequential fuel injection sounds like they all fire separtely, not togeher. anyone else got some ideas?

 

Does nobody know how the Vortec "SFI" injection system funtions? SFI off one injector? Anyone?

Runner size?

 

if its sequential, which it should be, then the fireing of each injector is timed to each cyl. I dont think its like the old cpi injector with the popets, which had a tendency to break every 2 years nececitating the purchase of a new unit. and believe me, those cpi units arent cheap!

 

I know the definition of "sequntial injection". What I don't understand is how this engine could have Sequential injection with only one injector??? I really thought this was the Central port injection (CPI), which means it would have only one injector, with the aforementioned hoses and popets going to each port. Again this is a '96 - '98 Vortec engine. Can anyone shed some (more) light?

And runner size? Would this intake reasonably feed a SBC 400?

 

Each fuel line has it's own valve. You can't see them without removing the upper plenum. The newer 4.3's have a similar system. They did away with the problem prone CPI system in 1996.

 

Okay, now I'm confused. How did they "do away" With the system in '96? This engine was made from '96 to mid '99 when the new 5.3l and 6.0L engines came out. The only engine they "did away with" was the TBI at the end of the '95 model year.

Engines up to the end of the '95 model year had TBI. Mine is a '96, the first year in run of engines that, again, were the same to '99.

SOOO, is this engine CPI? I think it is. If so, how in the world does that function sequentially?

 

hes saying thos engine is NOT CPI (central port injecton) injected, it has a valve at the end of each line that injects the fuel in to each cyl. CPI relies on jsut one injector to meter the fuel. It was used along with the tbi as a performace upgrade and the cpi fell inbetween tbi and the mpfi systems on the syclone/typhoon if im not mistaken. its a speed density where as the vortec is sfi. The cpi was discontinued with the introduction of the new vortecs.

 

The 96 up Vortec uses a single modular injector which has the
regulator and 8 injectors in a single housing. Each injector forces
fuel down a tube and through a popet valve at the head.
It takes approx. 53lbs of pressure to open the popet so when
the pump starts to get weak the engine craps out. Fuel pressure
spec is 53 to 55lbs any lower than 50 and it won't start.

The 4.3 Vortech uses the same type of modular injector.

Look right behind the intake horn and it's the thing with the wiring
harness attatched to it. It inserts down into the top of the intake
manifold.

It is a sequntial injection setup.

 

Thank you! Now I get it. I just couldn't see how one injector could make a sequntial system! Now I know it has eight, they're just not packaged in the convetional manor. Thanks for the info.