FCA duty cycle questions.

[DODGE74]

Guys I'm trying to figure out why I'm only logging 62% of the FCA duty cycle when I have it at 71% on the table. I havent changed anything in the other fuel pressure tables besides the fuel pressure map so everything is like it was stock.

With it only going to 61% of its max duty cycle my pump is struggling to keep up with my nozzles. I've talked to the pump builder and he thinks that if I could reach the max the pump would be able to support the size of my nozzles.

Here is a couple of screen shots of my tune file and log.

http://i288.photobucket.com/albums/ll172/gwlapw/FCAdutycycle.png

http://i288.photobucket.com/albums/ll172/gwlapw/DynoTuneTestrun.png

Any help would be appreciated.

Thanks, Gordon

[2007 5.9]

What is your mA current at that DC??

You can adjust the mA current down at that DC to get more fuel out of it.

[DODGE74]

Thanks Les,

here is the screen shot of the FCAmA It goes as low as 718

http://i288.photobucket.com/albums/ll172/gwlapw/DynoTuneTestrun01.png

[dansdieselp]

Who's the pump builder?

[Dmaxink]

The pump doesn't look capable of producing it IMHO... We can see the ECM requesting the larger value and the pump just physically not meeting it. You can try to manipulate the sensor with the milliamps, however, it doesn't look as though the pump is wanting to put out! We have driven Dmax pumps past their limited mm3 per sec and gone out of range on the fuel flow base trying to achieve what you are, but only deemed to aggravate the problem worse. But hey, it doesn't hurt to test right? Lol

[DODGE74]

Who's the pump builder?

It's Shane's from Motorsport Diesel 10mm stroker pump.


Thanks Kory, in talking to Shane he felt that since the pump only went to ~62% of the fca duty cycle it still had about 14% of its flow being held back and if I was able to get the fca to go to 71% the pump "should" meet demand. But, I'm not sure and I can't figure out why it won't go to its maximum duty cycle. It should be showing 71% in the log right?

[2007 5.9]

I have adjust the mA table to get 71%...it takes some testing to get it there, but you can

[DODGE74]

I have adjust the mA table to get 71%...it takes some testing to get it there, but you can

Thanks Les, ok, I just looked at the mA chart and at 70% its showing "0" and at 60% its showing 770. So I guess at about 62% where I logged its about 718 mA like it showed.

Where would I start stepping down?

Should I start a about 50% and start stepping down the mA in 20mA increments till I reach my desired duty cycle?

[Dmaxink]

Drop 718@60% to 400 and step it from there

[DODGE74]

Thanks kory, I'll give that a shot and see how it does.

[FUBAR]

Drop 718@60% to 400 and step it from there

What happened to withholding your 'little golden treasure chest'?? That's okay, I won't divulge what for....hehe

[DODGE74]

Drop 718@60% to 400 and step it from there

I tried this out this morning and it seemed to work, thanks again Kory.


I made the change in my street tune to try it out and although it takes some rpm it does make max rail pressure. Here is a screen shot of it. Why doesnt it show 71% on the duty cycle since I maxed it out?


http://i288.photobucket.com/albums/ll172/gwlapw/HotStreetTestrunmAadj.png

[Dmaxink]

Looks like she's holding FRP extremely well, I also noticed you are down 200uS from this screenshot and the last one... I'm assuming it's still holding rail at your commanded 2996uS?

Also, sorry for mis-informing you on the mA table vs desired.. I was obviously in la la land as we use this table to great help control surge off of big dual pumps.... You can override/underride your desired with the mA table...also a fuel flow base and mm3 per sec limit tables (which some are not available on the cummins). I hate saying something and having to go back, but human and make mistakes! Knew better, but glad to see she is coming along!

[2007 5.9]

I understand your concern with peak DC%...but as someone who looks/tunes from logs all the time...I'm more concerned with the large deviation in FPA/FPD at the hit of the throttle.

There is quite a difference when you mash it....I'd be focusing my efforts on getting that out, doing that will ease the pain on the pump on top, as it's not trying AS hard to recover from a big hit.

[DODGE74]

Looks like she's holding FRP extremely well, I also noticed you are down 200uS from this screenshot and the last one... I'm assuming it's still holding rail at your commanded 2996uS?

Also, sorry for mis-informing you on the mA table vs desired.. I was obviously in la la land as we use this table to great help control surge off of big dual pumps.... You can override/underride your desired with the mA table...also a fuel flow base and mm3 per sec limit tables (which some are not available on the cummins). I hate saying something and having to go back, but human and make mistakes! Knew better, but glad to see she is coming along!


Thanks for your help Kory.

Yes it was. I actually lowered the commanded rail pressure down to 160mpa just to see if it could manage stock pressure and I moved my rpm limiter back down from what I had it set for the dyno and I think that is why it may have been down.


I understand your concern with peak DC%...but as someone who looks/tunes from logs all the time...I'm more concerned with the large deviation in FPA/FPD at the hit of the throttle.

There is quite a difference when you mash it....I'd be focusing my efforts on getting that out, doing that will ease the pain on the pump on top, as it's not trying AS hard to recover from a big hit.

Thanks again for your help Les.


I agree, its easier to keep up when you dont fall so far behind. I'll get working on that and see what I can come up with.

OK, if your not concerned with the DC% then it wont bother me. I was just curious why it didnt show what I was commanding but obviously it was working tweaking the mA table.

[comnrailpwr]

Bringing this back up. I finally got my truck done and made pull down the track. My desired vs actual rail pressure is off and it takes a very hard hit once I'm out of the clutch and never really recovers. Unfortunately the Truck is competition only and I cannot test on the road and would like to wrap my head around this pump tuning. The truck went down the track very clean so I could use more PW to get more power but am wondering whats going on with my pumps before so. Their not keeping up but is there anything I can do in my tune? I read this thread and am kind of confused. Why is 71 the magic number for max duty cycle. What relationship does mA have With Pump flow or recovery? I'm having a stupid attack right now. So far the only FP tables I have touched are the Base and air densities. Not sure which way to go when tuning the injection pumps. The more I try to make since of desired and actual duty cycle the dumber I think I get. I shouldn't be running out of pump I wouldn't think. Any help is appreciated. The attached log is in EDA format, Tune was in CSP operating system #5 so you might need the latest unreleased version to view the log.
Edit* Also cant figure out why mm3 dropped. Possibly because I fell under the charger but it drops before I let up. I have triple checked tune and nothing there is limiting me that I can tell.

900-1000RWHP
Dual Pumps - stock/Floor It 3.5
200% Extrude Honed NOZZLES
Aeromotive A1000 Fuel System @ 35psi
3.5 pump os basically new. Stocker is a few years old

[Dmaxink]

Ever take a dual pump setup and unplug the ground? It goes wide open... If you take the top of the duty cycle table (70%) and see where that is in conjunction with the mA table, you will see that 70% is wide open on the mA table. When the pump is unplugged, it does to 0mA and goes wide open. If you set up your tune to go to 70% and 0mA at WOT, then that is everything the pumps have in them. Sometimes if folks try to over pressure the pumps when not necessary they will surge.

Just a couple tips,
Kory

[comnrailpwr]

Thanks Kory. Well I have sinced made my max duty cycle 96% and above 50% on the mA table scales down to 0 rather quick. After the log thats posted I have made more pulls with these new settings. The tune is commanding max fuel so nothing is tune related. I have eliminated prv and still no change. At idle if I unplug either fca rp only goes to 20k so that tells me I have a leak somewhere in the system or each pump is weak(unlikely). Pulled crossover tubes and found two with light nicks on the ends. Hoping their my issue. Also found a cracked injector nozzle:eek:. Waiting on parts now. Hopefully all will be well. Hate to send pumps out mid season.