[scblucam]

I wouldlike some input on sequential port injected systems. Also I am not enamored with electric fuel pumps and high pressure fuel all over the car. I have asked about a high pressure mechanical pump I have seen, the brand eludes me as of now. If an electrical pump is required what is the prefered mounting location, and what is the best way to install the return line?

[JimM]

Scott, Sequential systems fire each injector individually, timed with the opening of the intake valve.

Most EFI systems are batch fire, and fire all the injectors on each bank at the same time, alternating between the left and right sides.

Some of the LS motors are sequential, so were the later years of the buick turbo V6. At least theoretically, SFI system have a performance advantage.

I wish you'd remember that high pressure mechanical pump! My TBI system needs 21 psi tops, and I'd love to do it with a mechanical. Would solve a lot of headaches, I'll be trying an external electrical using the stock tanbk and pickup, and see the possibility of trouble with slosh and aeration.

When I replaced my sender years ago, I took the fuel tube from the old one, drilled a second hole in the new on, and brazed it in, bent kinda sideways to minimize aeration. Hope it works! Here's a pic:

Most peole either get a custom tank setup for an internal pump, or sump the stock one and put the pickup in the back.

I'll be mounting my external pump in front of the tank, as low as possible. I'll build a bracket to hang the pump and filters where the transverse muffler used to be.

[Doug F.]

Probably mean the Race piston pump.

[67ragtp]

I run my FAST XFI sequential, cant really tell you if its any better than a batch fire system, but it sure runs smooth.


Dont know if this is the prefered way, but it is another way that will work and has run good in my ride


Rich

[scblucam]

JimM, Doug f is correct. It is a piston pump that mounts where the stock pump mounts.
Check it out at www.racepumps.com It seems to me that it would work with most systems if it will hold the pressure and stay primed. I believe somewhere on their site it says it does not need a return line. Besides notneeding eletric power, not having to run a return line would be nice if you don't have to crank forever to get pressure.
By the way, i did know the difference in SFI and batch. I was more asking opinions in the difference in drivability and power of the aftermarket systems with each. My 85 IROC TPI has batch and runs great but shutters at idle a little.

[scblucam]

67ragtp, Is there a tube that drops to the bottom of the tank or do you not get full usage of the tank. It looks from the pictures that the suction will leave a lot of fuel in the tank.

[Chevy-SS]

67rag, u say it runs smooth????? It doesn't look like it's ever been run, LOL. Not even all hooked up.

[67ragtp]

Scblucam,

The tanks was made by rock valley and the pick up tube does go down, I have on a few occasions run it down below a 1/4 of the tank and have had no hic ups in fuel pressure.

chevy-ss,

Unhooked is the smoothest its ever run, thats why I showed that pic, LOL . Here's a more recent pic, I just replaced all the fuel lines under the hood with Harris speed works AN Teflon lines. Had the russels braided hose but cheaped out on the summit AN fittings and they didnt fit the hose very tight, so every time I took the car out, I had a vision of one of these summit fittings blowing off 44psi of fuel and the whole car torching up(ya - IM a mental case, fuel fittings are not the place to cheap out.)


Rich

[Chevy-SS]

Rich, looks real nice. I kinda hear ya about the hoses. I had good luck with the black braided hoses and Russell fittings though.

Mine's not as purdy as yours, I've been running it for a couple years.





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[67ragtp]

Looks great Dave, EFI BB gotta love it!!

Rich

[novaderrik]

Originally Posted by JimM

Some of the LS motors are sequential, so were the later years of the buick turbo V6. At least theoretically, SFI system have a performance advantage.

i believe every gen3 (LS) engine is sequential. it would be a real step backwards, since every LT1 from 94-96 was sequential, and the Buick 3.8 has been sequential since the late 80's.
but GM's first mass produced sequentially injected engine was the 84 turbocharged Buick 3.8 that got put in GN's and T Types. it worked pretty damn good in those cars, and to put in a batch fire setup is just going backwards.

[JimM]

has anyone ever quantified if there is a difference in performance, economy, driveability, or emissions, and how much?
xfi systems can be changed from batch to SFI with the flip of a (s/w) switch, tright?

[camcojb]

Originally Posted by JimM

has anyone ever quantified if there is a difference in performance, economy, driveability, or emissions, and how much?
xfi systems can be changed from batch to SFI with the flip of a (s/w) switch, tright?

I'm sure there is a difference in the above, but it isn't going to be a lot. I've had several batch-fire cars that ran smooth as silk and got great mileage.

If your system can run sequential and you have the two triggers needed to run it I would. Otherwise, it probably is not worth the expense to swap to.

Jody

[davepl]

I dispute the claim above that SEFI will win for performance. T'aint possible, because by 3000 rpm or so the systems either (a) switch to bank fire or (b) are defacto bank fire anyway.

After all, if you hit 85% duty cycle, your injector is open for 85% of TWO revolutions of the crank. At that point its by no means synchronized in any useful fashion to the intake valve, so the only benefit I can think of is less pressure variation in the fuel logs.

The real goals (and the reason the OEMs switched to it) are driveability and emissions and economy, and those are all part-throttle, low rpm things.

GM swtiched from bank to SEFI in the '94 Corvette LT1. It'd be interesting to compare 93 and 94 Vettes to see if there was any perceptible difference...