New injectors running lean PFC

[derek240]

I just installed new sard 700 cc injectors and nismo fuel pump, and adjusted the injectors to 63.5% and the car would cut out at idle running extremely lean (18-19.9+), and hunts at idle. I had to increase the injectors to 83% and the car runs well.

I changed the fuel filter to a 300zx filter and bypassed the fuel pump relay, which seemed to help the hunting, but afr's still aren't as low as they should be at 83%. The injectors are light blue, which should be 700cc, but the are operating like 560cc.

I'm running a powerfc, and reset the maps back to factory and did the learning procedure, but the car still runs horribly. The ecu was working very well on the stock injectors and pump.

Has any one else had this issue or have any advice? Thanks in advance

[souljourner]

Hey guys, I just want to add that this is with a powerfc d-jetro for r32 gtr and a/f used to run great before the swap but now must add 20% fuel just to idle. Any thoughts would be much appreciated

John

[Skym]

There should be a setting in PowerFC laptop tuning software and on hand controller (I think under injector on hand controller) to adjust each injectors resize individually in %. It's important to set the correct increase in size from stock injector size for each injector, if you know the flow rates of the new injectors. With GTR engine, I think you put highest flowing injector in 6th cylinder and next highest flowing injector in 5th cylinder, etc.

With stock ECU tuning software, you just input the stock injector size 444cc and the lowest flowing injector in cc of the bigger 700cc injectors (roughly 1-2% difference between them) and then can fine tune at idle, etc. PowerFC asks for it in % of difference between the sizes on each cylinder, which can be confusing.

If injectors don't have flowcharts with them, can get them flow tested here -

http://www.deatschwerks.com/catalog/injector_services.php

Or buy their injectors (As far as I know they are from same manufacturer as SARD injectors) that are flow tested, etc.

[mcfly]

Skym he adjusted his injector percentages as he should have, 63.5% and sard injectors are made by denso.

To the op, you should at least be ballpark when you adjust the percentages. Check what you have for fuel pressure. Did you buy them from a reputable place? And lastly you are getting your map sensor reading fro ma half decent location?

Does the car run fine if you swap factory injectors back in and go back to the base map.

[Skym]

What I'm saying is each injector has different flow in cc hence different % in each cylinder on hand controller or tuning software. Basically don't use the highest flowing injector (700cc) as a gauge for the % difference. Flow testing them helps to find the highest, lowest flowing injector.

One cylinder might be leaner than the rest and adding 20% of fuel should compensate for the lowest flowing injector. PowerFC allows you to adjust each cylinder, where as stock ECU needs to be set to lowest flowing injector.

Also I think the base tune (fuel maps) runs engine leaner which probably adds to the problem.

[mcfly]

trimming one injector 20% is only going to change his overall afr 3% richer

[souljourner]

trimming one injector 20% is only going to change his overall afr 3% richer

Thanks for the feedback guys.

We added 20% fuel so instead of 63% for each injector, we had to put nearly 80%. At 80%, the car idles at 14.7 A/F.

Seems that fuel pressure check must be in order. We shall do that next but we don't have a fuel pressure gauge yet.

[victoriaGTR]

souldnt the injector setting be at 63.4% and the latency be .33
thats is assuming the sard injector latency is 1.1

[Skym]

The Latency (time it takes for injectors to fully open) could affect idle. But wouldn't the opening time be longer at idle vs shorter at higher rpm's???

Also wouldn't you normally play with K constant until idle was smooth???

Or it could be that the stock FPR has failed.

[derek240]

Thanks for the input guys, more suggestions/ideas are welcome.

From what I found, the lag time for the Sard 700 are 0.65ms, stock should be 0.772, so I have it calibrated for -0.12ms. Powerfc only allows you to adjust injectors by 0.5% at a time, so I just rounded up to 63.5%.

Reading paulr33's faq...they actually round 0.772 up to 0.78...which would make the correction -0.13ms...I'll try that tomorrow, but that almost seems too easy a fix for a gtr problem...

I haven't driven the car on the road too much since the swap, but at 83% the car seems to drive well, and boosts fine. The stock pfc map seems quite rich in the lower rpm (I was reading 10.x to 9.9- on light load in 5th doing 2000rpm), and a quick pull to 6000rpm in 2nd had a max knock of 20.

Has anyone had idling issues running the 700's? I know 'large' injectors may have problems idling...but I didn't think 700's were big enough to have this problem. I have my idle set to 950rpm.

Maps are tapped into the balance tube. Injectors and pump I bought new from rhdjapan.

[victoriaGTR]

i have d jetro and my idle is 1200rpm... big injectors = harder to idle

u have datalogit?

[Skym]

Spray patterns can affect idle with bigger injectors. Flow testing can help, as they check spray pattern and can rebuild / correct injectors if necessary.

[victoriaGTR]

my RC's came flow tested....
wouldnt new sards come like that as well

what tune are you using??? djetro doesnt have a base tune....

[Skym]

Sometimes injectors are worse after flow testing, cleaning, etc. Some don't do it properly and screw the injectors up. Not the first time I've heard of those horror story's. Some highflow injectors can cause bad idle problems.

This link shows the difference between good spray pattern and bad spray pattern -

http://www.deatschwerks.com/catalog/injector_services.php

Not sure, never used Sard.

[mcfly]

my RC's came flow tested....
wouldnt new sards come like that as well

what tune are you using??? djetro doesnt have a base tune....

My d jetro had a base map on it?