Ronny

iTrader: (1)

Are we in agreement over 80% inj PW is maxed and engine goes richer?

At 4850 rpms I am 92% DC 02@960mv BLM locked 124 IAT 95dF.

That was with a 75HP shot of N20. WB showed 12.8/1. 2nd gear of 4 pull for 2.0 seconds then shifted and let off gas.

80 lbs(75?) inj at 23 lbs FP.

This was posted by RBob a while back:

" If there isn't enough fuel to feed both the injectors and the N2O system fuel nozzle the fuel pressure will drop. There won't be an increase in injector DC% as hopefully the ECM is in PE mode and there isn't any fuel trim correction."

I cannot monitor my FP as gauge is under hood. I may have to duct tape to windshield temporarily to verify. If I up FP it looks like I may not achieve desired DC under 80% per RBob?

Is there a calc I can do to determine the lbs per hour or grams per sec of TPI pump vs the inj flow and N20 jet flow? I believe TPI is 43 lbs with 8-17 lbs injectors.

Ronny

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ttt

RBob

iTrader: (1)

The normally accepted maximum duty cycle is 85%. Once over that the injectors get erratic and can either add fuel or subtract fuel from what is expected.

To test the pump re-route the return line to a container and run the pump for a set amount of time. Then measure the amount of fuel that was pumped. Note that the voltage to the pump will make a difference in how much fuel is delivered.

Best to use a solid 13.8V supply for the pump so you have repeatable results.

RBob.

The_Punisher454

I have a microcontroller based injector flow bench I built a couple years ago. Its down for some upgrades right now, but when I rebuild it this winter I'm planning to reprogram it for some much more detailed testing. Injector performance at low pulsewidths, low/high voltages, and such. Any suggestions for timing uSec min/max ranges I should target?
Currently I'm set up to vary the RPM from 50 to about 12000 and the duty cycle from 0-100%. This time around I'm going to include voltage control as well as enter exact uSec values to test. My goal is to test some popular injector types here and post the results, since a lot of the data is unpublished or sometimes incorrect. Hopefully some of that testing will help answer some of these questions.

Dominic Sorresso

Ron,

Have you used the Injector Bias to help lower DC%?

Ronny

iTrader: (1)

I am raising FP from 23 to 26 this evening. 75 lbs injectors. EBL.

Injector correction multiplier for voltage. I am 10% higher than stock EBL .bin
Same on Injector correction offset
Inj asynch not changed. I run synch 100%.

Rbob say the fuel pump needs to be adequate. My Delco TPI at 26 lbs FP through 75 lbs injectors flows 104 lbs per hour or 15.9 gal of fuel . Supports 350-390 HP. GM rates pump at 24 gal at 50 psi FP(TPI FP is 43). So I have ability to flow more for N20 use but cannot go over say ??? 30 lbs FP. Or do I have the xtra capacity?? I have yet to determine what a 28 N20 jet size will flow in gal/hour at 23-26 lbs FP.


Food for thought. I set my BPC/VAC caculator to 50 lbs FP and it came to exactly 24 gal as GM has the pump rated. So I have a good # on capacity

Punisher: I idle 1.7 and WOT around 6.0 mS(synch).

Dominic Sorresso

Ronny,

Something tells me this is deja vu all over again, but my IB correction was nearly double that of stock. I seem to recall something like 700+usec. This may not do it completely for you but it could get you closer before making a FP change etc.

Ronny

iTrader: (1)

OK I did change per your suggestion. I will hold off on FP. I am at 443usec for 12.8v currently for offset. So 1.45 x is 642. Seems like a huge change. But larger injectors at higher FP may require it. I will do same 45% change on Correction multiplier. I may add another 10% if I see results. Seems my DC% changed with the N20 but RBob I think was pointing at fuel pump adequacy. I will see how that works out and report back. Not many safe opportunities to test the car let alone a N20 shot.

Dominic Sorresso

Ronny,

Tell me about the safety issue. With the Xfire I could datalog my WB and tune WOT through 3rd gear. With the ZR-1, 3rd gear @ 7000rpm = 118mph+.
Difficult to find an on ramp to deal with that. Taking it to a dyno next week for tuning.

Ronny

iTrader: (1)

I datalogged this morn but not at WOT. BLMs ran rich as a result of doing the bias changes above. Ran rich 5-10% from prior day. My idle went rich by one point. Air temps are warmer this AM vs yesterday and week prior. So it appears the bias added significant fuel. Will report on DC change later.

Dominic Sorresso

Ronny,

That's the point. Now you can drop VE since you need less pulsewidth. You now have actually a larger "effective" pulsewidth since you are giving the injectors more time to open. A bit like spark advance and latency. You're leading the target.