Fuel distribution in a v8, 2 squirts vs 4 squirts.

[5.0Thunder]

Just wondering if anybody has done any experimentation on a v8 using 2 squirts vs 4 to determine if fuel distribution is altered or worsened in a 2 squirt scenario.

I tried to do some experimenting on my car but without EGT probes or individual widebands (heck, i don't even have a temp gun), I can't really do a lot of analysis. My thought was that 4 squirts would help even out AFR's across cylinders over 2 squirts, though at higher RPM it may not make a difference? I've got SD 80's on e85 and make about 1.6ms at idle in 4 squirts and around 2.7ish on 2sq. VEAL seemed to smooth my table out on 2squirts where 4squirts makes a slightly peaky-er table while targeting the same AFR's.

That's about the only data I can come up with but don't know if it is really quality data. Anybody else have anything to share?

[Yves]

Based on my experience, the uneven AFR's in a V8 are not caused by fuel distribution, but by unequal airflow.

More squirts mean potentially better fuel atomization, but at the cost of shorter pw at idle, which could give you other problems.
I have technical documentation that shows the you need to allow some time between the injection pulse end and the opening of the intake valve. On my engine this was confirmed by the facts.

[5.0Thunder]

So if low pw isn't an issue, it should be theoretically better to use more squirts. I wonder why this makes my VE map peak more than 2 squirts though, since i have way more injector than I need in those areas.

[Yves]

Can't answer that. It may depend on a lot of things.

[Blown88GT]

MS3 or MS2?

[5.0Thunder]

MS2 in a port injection setup. MS3 (sequential?) would always use one squirt wouldn't it?

[billr]

No, MS3 can handle all kinds of squirt combos.

[5.0Thunder]

oh, i see. Why use more than one on a sequential system?

for reference, mine is batch fired MS2. This is why I figured 4 squirts was more likely to produce more even distribution into cylinders.

[Blown88GT]

MS2 in a port injection setup. MS3 (sequential?) would always use one squirt wouldn't it?

Not always.

For MS2 or MS3
If you inject simultaneous and one injection, and have the same number of injectors as cylinders [i.e. port injection], then REQ_FUEL on the bottom is the same as REQ_FUEL on top. Same with alternate and two squirts. If you put in simultaneous and two squirts, then REQ_FUEL is divided in half - because you squirt twice, you need to inject 1/2 the fuel on each shot.

Note: if you choose alternating for port injection, make sure your number of squirts is an even number (2,4,...) and evenly divisible into the number of cylinders. For example, with an eight cylinder engine, you could use alternating and 2, 4, or 8 squirts/cycle.

Cannot alternate 8 cyl with 1 squirt
Either set to simultaneous or adjust squirts so that:
cyl/squirt produces a whole number with no remainder,
squirts is an even number & evenly divisible into the number of cylinders.
http://www.msextra.com/forums/viewtopic ... 97#p502097

Injector Staging
Sets injector staging in non-sequential modes. For Sequential set 2 Squirts/Alternating or 1 Squirt/Simultaneous.

[billr]

Yes, if you set MS3 for sequential you will get only one squirt, no matter how many you have set. But, MS3 is not limited to just sequential, it can handle all of what MS2 does, and more.

[5.0Thunder]

Thanks bill, I was getting confused about the ms3 sequential stuff. I, for the most part, understand how the batch firing is working either with MS2 or MS3.

Good info Blown88GT. Looks like a description of the injection sequence for every cycle. I was more wondering if somehow the 4 squirts would provide more of an opportunity to hit the hot valve at the optimum time than 2 squirts to provide better atomization.

[Blown88GT]

I've been using 4/alternating for over 3 years. The Base Map from DIY uses this, too.

[5.0Thunder]

Same here. I'm at the minimum comfortable idle pulsewidth with SD 80lb injectors using 4 squirts. I had tried 2 squirts for a while and the PW jumped back up to about 2.7 and VEAL started lowering the peaks in my VE table. the car drove fine in either case. The atomization/distribution question was always lingering when i was using 2 squirts though and I was wondering why the VE table was smoothing out. Not sure why the shape of the 3d surface should change.

[95ponymobile]

I use the alternating 2 squirt method to keep my pulsewidths up a little to keep the injectors out of any poor flow curves.

[5.0Thunder]

I use the alternating 2 squirt method to keep my pulsewidths up a little to keep the injectors out of any poor flow curves.

I'm guessing this runs fine? Does it idle very smoothly? whats the idle RPM? Manual or Auto?

[95ponymobile]

I use the alternating 2 squirt method to keep my pulsewidths up a little to keep the injectors out of any poor flow curves.

I'm guessing this runs fine? Does it idle very smoothly? whats the idle RPM? Manual or Auto?

Sorry i didn't know you responded to my post. Yes it runs great. Idles as smooth as it can with the cam it has (E303) and at 850RPM. T5 manual

[Digger]

So if low pw isn't an issue, it should be theoretically better to use more squirts. I wonder why this makes my VE map peak more than 2 squirts though, since i have way more injector than I need in those areas.

4 would be better all things being equal. I had issues with WOT mis-firing due to uneven fueling. Switching from 2 to 4 squirts really cleared it up.

Switching between 2 and 4 should not affect VE or AFR. If it is, you may not have correct injector deadtime. I can switch 2/4, alternating/simultaneous without needing to correct VE. Another reason might be how the engine digests 2 vs 4 squirts and may not fully burn the fuel, which would throw off perceived VE.

[martroy]

With 80's injectors, you get idle down (900 rpm) the engine right with 4 squirts?

[5.0Thunder]

With 80's injectors, you get idle down (900 rpm) the engine right with 4 squirts?

Yes, on e85.

[martroy]

Sorry, I was talking about gasoline.