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Discussion Starter · #1 ·
I don't really need help with a system, but I thought an open discussion on some of it's principles would be helpful for all of us.

I am planning on gettting a system from www.rancefi.com the six pack set up.

So, on direct port injections, what determines the firing of the injectors of each cylinder on a stand alone system that does not time the engine as well?

If there is a bung in the collector on each side, I guess it only "smells" the gas for that bank- so I guess there are still lean and rich cylinders?
 
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Discussion Starter · #2 ·
Man, I didn't want to move this to the technical board, more of a discussion of EFI, it's advantages, more than a specific question on the technical board, oh yell LOL
 

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hmmm

my second most favoritist topic ;D

the firing of injectors is based on a fuel map that says if this than that. uses input from throttle map/maf air temp coolant temp rpm many others.

it has preset fuel amounts based on those variables.

the injectors are fired by left and right banks usually. not timed to valve opening.

there would theortically be lean and rich cylinders but its due to air distriubtion problems
 

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CruisingRam said:
Man, I didn't want to move this to the technical board, more of a discussion of EFI, it's advantages, more than a specific question on the technical board, oh yell LOL
the tech board isnt only for tech questions. it is for anything tech. this is tech, so i moved it here ;).

Duane
 

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It would depend on if it is a "port" (PFI) EFI, or "sequential" (SFI) EFI. Both sytsems have injectors mounted in the intake runner near the valve. "Port" fires two injectors on each bank for cylinders that are near opening the intake valves. "Sequential" fires each injector in time to when that intake valve is begining to open. SFI gives more presice fuel control, but prot works fine as well. Auto manufacturers used PFI for a long time with no problems of cylinders leaning out. Fuel amount is controled by how long the injector stays open (pulse width.)
Pulse width is determined by coolant temp, O2 levels in the exhaust, MAP (Manifold Absolute Presure, vaccuum if you will, this is also used to calculate load), throttle position, intake air temp. The compute uses these variables the adjust the fuel trims (or fuel map if you will.) As far as advantages, let's see...fuel economy, power, lower emissions, throttle response, idle quality, will work on any angle (even when your oiling system won't), do you need more?
-stew-
 

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Donk said:
doesn't Batch Fire shoot a whole bank at once
Just think if this was kept on the open discussion board what this could have been.

"Whose shooting batches?"
"You smell what from my bung?"

In regard to the fuel injection, you are unlikely to run any cylinder lean even if its the port injection since the program compensates for this. The gas may lose some intake velocity, but will not go to waste in some cylinders.
 

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How many injectors operate at once on batch fire depends on how you set it up and how many ECU outputs are driving injectors. Keeping it simple you'd just have a left bank and a right bank, but that would mean you'd have to split your fuel injection time up to four ways which can be detrimental to repeatable injection volumes. A better way to set it up would be to phase-pair two cylinders, allowing only two injection events per cycle (one at beginning of intake, another at the beginning of the power stroke). The best is sequential injection, but with a V8 that requires a lot of available injector drivers from your ECU and requires more sensors.

Going back to CruisingRam's question, you will need to have a crankshaft position sensor at the very least to operate EFI. To run sequential you'll need the crank position and a cam position. Different ECU manufacturers will have different requirements of where the pickups have to be relative to #1 cylinder TDC and how many "teeth" your crank/cam pickup wheels will have to have. Sequential requires both cam/crank sensors because a crank pickup can index the engine so the ECU knows when the #1 cylinder is at TDC, but it requires the cam sensor (turning at 1/2 crank speed of course, for twice the resolution) to tell the ECU whether the cylinder is at TDC on compression or exhaust.

With any setup other than sequential you are likely to have air/fuel ratio variations from cylinder to cylinder. Even with seqeuential, you will have to manually tune injection times to each individiual cylinder's relative airflow. It's not so hard if you can instrument each individual exhaust port for EGT or use spark plug seat thermocouples.
 
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