I am knee deep in a discussion with a pro Rice friend

now the 3rd get uses bank fire for the injectors so one side fires then the other

his point is sequential fire destroys gm bank fire


can any one offer me any thing on the pro side of bank fire or am I going to lose this one to the RICE. (first time but only off the road)

help the Domestics win on the road as well as off the road

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1986 IROC 350 5spd
just installed a TPI from a 1988 IROC, 24# lt1 injectors,165 ECM MAF, custom sub frame

[This message has been edited by v8power (edited September 21, 2001).]

 

First Batch fire fires ALL injectors not just one bank. That is why when you calculate the Duty Cylce, it is the time to fire the injectors in one revolution (ie. At 6,000 rpm, your injectors cannot be firing more than 10 msec, as that is the length of time it takes the engine to complete 1 revolution). With Sequential, it is based on operating cycle (2 revolutions).

And this is the next point, Sequential also keep firing both when the intake is open and closed, just like batch fire. How long is the intake valve open at 6,000 rpm? Between 5-6 msec depending on the camshaft. At part throttle, YES, sequential may get all the fuel in time to match the opening of the intake valve. But at WOT, it pulses just like Batch.

Sequential injection does not offer any great power advantages over Batch fire (@ WOT). The advantage to Sequential is emissions because at part throttle it CAN get the fuel in the cylinder in the proper amount of time, but not @ WOT. The biggest advantage I can see with Sequential Injection is that you can "trim" the individual injectors to compensate for an "imbalance" between the cylinders.

As for the firing of the injectors, it occurs in continuous "pulses", with the column of air moving in "waves". In a practical sense, the air is always moving with the injector constantly giving small bursts 8 times in an operating cycle. The fuel doesn't just hit the valve and "puddle up".

If you think about it, a carb constantly has a fuel/air mixture moving in the runners also, and look at how much power they can make. The advantage to fuel injection is in the precision of the fuel metering.

So ultimately, it really doesn't matter, because in all practical sense, the air with the fuel (whether PFI, SPFI, TBI, or Carb) is constantly moving. It doesn't just "go", then "stop". It moves in a "wave" action.

And before ANYONE agrues that SEFI does not constantly fire, I ask you to tell me how big an injector you would need to make a 350 HP LSI engine so all the fuel is delivered in 5-6 msec @ 6,000 rpm. The answer is almost 40#. Unfortunately, the LS1 (or LT-1) use much smaller injectors and cannot move that much fuel in 5-6 msec (the length of time the intake valve would be open during an operating cylce of an engine @ 6,000 rpm).

Again, at lower rpms, sequential does have sufficient time, and is one of the reasons it gets better emissions and slightly better at fuel economy. But at WOT, it behaves much like Batch Fire, except you can "trim" each individual injector to compensate for any "imbalance" you may have between the front, middle and back cylinders. This is a big concern for short runner design manifolds like the Miniram and the LT-1 intake.

[This message has been edited by Glenn91L98GTA (edited September 21, 2001).]

 

PS: The numbers I am using, "10 msec @ 6,000 rpm" represent 100% duty cylce. You should NEVER run your injectors more than 80-85% duty cylce. So you really only have 8-8.5 msec to get the fuel into the cylinder @ 6,000 rpm.

This is why as you need larger injectors as you make more HP. Because you generaly get the extra HP by revving the engine more. The more you rev the engine, the less time you have to fire the injector. You actually have 2 factors working against you: 1) More HP requires more fuel (longer injector pulse width needed) and higher RPMs require less time for the injector to fire.

 

Glenn you are a ***


my hat is off to you

CHEVY POWER 1

RICE 0


sweet

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1986 IROC 350 5spd
just installed a TPI from a 1988 IROC, 24# lt1 injectors,165 ECM MAF, custom sub frame

 

One of the MANY things we can talk about on Oct 3rd. Your wife and mine can go out shopping while we talk cars.

 

why do they *** out the word G@D