ok im going to start to get kinda weird i havent sleeped in 2 days and my mind is starting to wonder so please stick with me. i was wondering if any other people on here would see the benifits, of going from Batch fire to sequential fire injection. now i looked on line after i had the idea of changing to sequential fire injection and found this:
"Batch fire will group the injectors and fire all injectors in a group. Sequential fire will trigger each injector seperately! each will have it's own lead back to the ECM and they are fired in the same order as the ignition. Fuel is only sprayed at the intake valve that is open rather than at closed valves like the batch system does." Injector wires firing the correct injectors?? [Archive] - The Unofficial Z28 Forums

and i think by changing to sequential fire injection, the motors MPG, HP, TQ and EFF. would go up because instead of the fuel staying on top of the intake valve in a Batch fire injection set up when it fired injectors 1357 and 2468 waiting to go into the chamber, i would think that a sequential fire injection system would have a greater velocity going into the chamber and would atomize fuel a lot better...

tell me your thoughts on this...

 

Yes, SFI is more efficient but can be more difficult to tune. Just look for a 89-up TPI harness and computer and there ya go, SFI... The benifits from going from MPFI to SFI really aren't as high as you think... There will be a difference, but not something insane by any means. I think there will be something like a 10% increase in power, if that...

 

Well, you have some mis-information there. The sequential setups all inject on a CLOSED valve. They use the heat of the valve to help evaporate the fuel some, and then when the intake just cracks open, there's a strong exhuast blast that breaks up the fuel even more, and then more breaking up happens as it's sucked through the valve.

With large injectors, it helps control idle a LOT. At full throttle, there's almost no difference at all.

If you were to set up the sequential to fire on the open valves, you'd truly have a bad running engine. I've done it, just to prove a point. Emissions go through the roof like that, and there's lots of misfire.

Would I recommend sequential? Depends on the situation. If you're having to use large injectors, yes. If you live in a widely varying climate, yes. If you have lots of money and want it for cool factor, yes. If you think it's going to make a world of difference, no. If it's just a daily driver that already runs fine, no.

 

TPI engines arent sequential, they are all batch fire.

 

Further, they "fire" twice per cycle, and not in alternating banks, but all at once.

Another reason the SFI systems do a better job of fuel metering at lower RPM and idle is because they use a MAF for air metering instead of S/D. They use the MAP in more of a S/D mode for higher loads. It's like having the best of both worlds.

 

I have seen some good posts on the subject. One was by MadBill an engineer from GM. Basically above about 3500rpm there is no real difference between the two. Below that you might see a little more gas milage but not much. It is basically an emission control issue.

I was looking into it myself but after the research it is not worth it to me.

 

now thats the kinda ancer i was looking for

 

89-up TPI is NOT SFI. Still batch fire. LT1s are even batch fire.

 

I have the OBD2 setup on my car like discussed in the stickys. I am sure it is SFI. If you know what your doing, it can be quite nice. I am still learning and not getting the greatest of mileage.

 

On a side note, in order to have SFI, you have to have a cam position sensor, so the ECM can know which intake valve is open. A crank position sensor only gets you halfway there, because at any given crank position, there are 2 different cylinders that could be on the intake stroke, the ECM has no way of knowing which.

 

how do you have an OBD2 setup with a '91?

 

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