Stoopid Fuel Injection (SFI) Question.
Thread Starter
Melting Slicks
Joined: Aug 2000
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Stoopid Fuel Injection (SFI) Question.
OK, I'm just getting into the November 2001 issue of Corvette Fever and I'm reading about the "Fourth-Gen Veneration". They talk about the introduction of Sequential Fuel Injection (SFI) for the '94 production year. They state SFI fired the individual injectors in a sequence with the firing order of the engine rather than firing an entire left or right bank of injectors at the same time.
THE ENTIRE LEFT OR RIGHT BANK OF INJECTORS AT THE SAME TIME :eek:
Stupid Question(s): Is that how most fuel injection works? Firing a bank at a time? Did all pre-'94 EFI systems do this? What about the Ram-Jet 350? What about Holley & others aftermarket EFI systems?
Say it ain't so!
THE ENTIRE LEFT OR RIGHT BANK OF INJECTORS AT THE SAME TIME :eek:
Stupid Question(s): Is that how most fuel injection works? Firing a bank at a time? Did all pre-'94 EFI systems do this? What about the Ram-Jet 350? What about Holley & others aftermarket EFI systems?
Say it ain't so!
Drifting
Joined: Aug 2001
Posts: 1,708
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From: North Carolina
Re: Stoopid Fuel Injection (SFI) Question. (jerryp58)
i am stoopid with fuel injection, but I thought they all fired at the same time, and constantly. how can one fire and not the rest, expecally considering some of the aftermarket systems don't have wires running to every injector...at least i don't think they do...hell I don't know...I'll stick with a carburator....and I can't even spell THAT, let alone figure one out(thats why the big man made lars :lol: just kidding)
Daniel
Daniel
Race Director
Joined: Sep 1999
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From: Plano TX
Re: Stoopid Fuel Injection (SFI) Question. (jerryp58)
You are correct. Older GM systems were what is known as "Batch Fire", where one bank fires at a time. In 1994 GM went to Sequential fire (one injector at a time) on the LT1.
Lower priced afternarket EFI system such as the Holley (that I'm running) are batch fire. More expensive systems such as Speed Pro, Motec, etc can be had as either batch or sequential. I think Edelbrocks Pr-Flo is sequential which is unusual in a "budget priced" system.
All this said though, it really isn't a big deal. When the LT1 went to SFI there was NO power increase. Not a single horsie. GM did it for emissions.
Lower priced afternarket EFI system such as the Holley (that I'm running) are batch fire. More expensive systems such as Speed Pro, Motec, etc can be had as either batch or sequential. I think Edelbrocks Pr-Flo is sequential which is unusual in a "budget priced" system.
All this said though, it really isn't a big deal. When the LT1 went to SFI there was NO power increase. Not a single horsie. GM did it for emissions.
Intermediate
Joined: Jun 2001
Posts: 46
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From: Sydney, NSW, Australia
Re: Stoopid Fuel Injection (zwede)
If they wanted to do something they could do a direct injection system.
I think only Mitsubishi has done this.
I doubt youd see direct injection anytime soon in a vette.
I wouldnt get an EFI system that isnt sequential.
If anything id get victor junior manifold and have injector put in and have a computer like motec etc and have it do sequential EFI and controll the ignition.
Chris :cheers:
I think only Mitsubishi has done this.
I doubt youd see direct injection anytime soon in a vette.
I wouldnt get an EFI system that isnt sequential.
If anything id get victor junior manifold and have injector put in and have a computer like motec etc and have it do sequential EFI and controll the ignition.
Chris :cheers:
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
Re: Stoopid Fuel Injection (Gleese79)
Chris,
I a little confused... SFI does not make any more power than batch fire. There is no driveability change. Mileage is theoretically up maybe 1%, but not enough that it can be measured. Only benefit is emissions (and not much there either). Drawbacks of SFI is that you need either a crank sensor or a modified distributor so that the ECM knows what cylinder is firing. You also have a lot more wiring to worry about as every injector has to have individual wires to the ECM.
Not worth it to me...
As for direct injection, it's coming out now from GM. They are prototyping it for release in a few years. All indications point to the next GM V8 having the injectors spraying straight into the chamber. Again, no real power benefit, but it cuts down a little on the emissions.
I a little confused... SFI does not make any more power than batch fire. There is no driveability change. Mileage is theoretically up maybe 1%, but not enough that it can be measured. Only benefit is emissions (and not much there either). Drawbacks of SFI is that you need either a crank sensor or a modified distributor so that the ECM knows what cylinder is firing. You also have a lot more wiring to worry about as every injector has to have individual wires to the ECM.
Not worth it to me...
As for direct injection, it's coming out now from GM. They are prototyping it for release in a few years. All indications point to the next GM V8 having the injectors spraying straight into the chamber. Again, no real power benefit, but it cuts down a little on the emissions.
Intermediate
Joined: Jun 2001
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From: Sydney, NSW, Australia
Re: Stoopid Fuel Injection (SFI) Question. (jerryp58)
the difference is that the fuel is siting in the intake runner while your waiting
for the intake stroke.
for sequential it puts the fuel in when its taking air in so its more efficient.
as for direct injection it lets you inject when the valves are closed.
little differences but they do make an effect however small.
for the intake stroke.
for sequential it puts the fuel in when its taking air in so its more efficient.
as for direct injection it lets you inject when the valves are closed.
little differences but they do make an effect however small.
