Calculating K-Value and Latency From a Injector Flow Sheet

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jerdobi
Posts: 5
Joined: Thu Jun 12, 2014 8:50 am
Location: Seattle

Calculating K-Value and Latency From a Injector Flow Sheet

Post by jerdobi » Thu Jun 12, 2014 9:00 am

I've had numerous bad ECU chips made for me from just general guidance on some injectors I had installed in a Nissan 300ZX TT. Basically, each of these were incredibly on the RICH side (by design and of course fails emission testing). Typically, the purchased chips are coming to me at KValue = 195 and Latency = 83 or 77 when I say I have 555cc JECS new-style injectors. (way rich)

Therefore, I've taken more aggressive actions to tune these chips using TunerPro. The flow sheet says the injectors flow at 580cc at 3 bars and 632cc at 3.5 bars. I figure my fuel pressure is in the middle of this and therefore they are flowing at 606cc. The flow sheet says the latency for the injectors is .40 at 12volts and .44 at 13volts. So, I'm going to say the latency is .42 (in the middle).

This said, what's the Kvalue and Latency to set in TunerPro?

K-Value = 370 / 606 * 288 = 175.84
Latency = 42

Does this sound right?

jerdobi
Posts: 5
Joined: Thu Jun 12, 2014 8:50 am
Location: Seattle

Latency too low

Post by jerdobi » Thu Jun 12, 2014 6:01 pm

I tried this today and idle was rough. I put it back to Kvalue = 176 and Latency = 77. Seems a bit lean on idle, but close. I'm getting emission test on Saturday and see how it goes.

jerdobi
Posts: 5
Joined: Thu Jun 12, 2014 8:50 am
Location: Seattle

Yea, passed emissions test

Post by jerdobi » Sat Jun 14, 2014 3:25 pm

Passed test today, so not rich. Will put on wide band O2 soon to see if a bit lean. Pulls strong, idle seems low at about 650 sometimes.

jerdobi
Posts: 5
Joined: Thu Jun 12, 2014 8:50 am
Location: Seattle

A bit lean at K-value 176 & latency 77

Post by jerdobi » Mon Jun 16, 2014 6:53 pm

I realized the idle was leaning out and just was able to sustain 650 RPM with K-value of 176. It sounded lumpy, low idle and the idle varied a bit.

So, I increased the K-Value to 180 and the Latency to 83 knowing it might be too much. Now, I have a strong and stable idle. On reving it while cold it stumbled a bit; but when warmed up; no problems; so I think it's a bit rich when cold.

I'll do some runs on the freeway tomorrow and see if works better or worse. I bet the sweet spot might be in the middle at Kvalue = 178 and Latency of 80. I'll try that next time.

jerdobi
Posts: 5
Joined: Thu Jun 12, 2014 8:50 am
Location: Seattle

Final Settings for JECS 550cc Injectors

Post by jerdobi » Sat Jun 21, 2014 10:58 am

The final settings for my Nissan 1990 300ZX TT with some JESC 550cc Injectors (new style) that were flowing between 580-632cc depending on the fuel pressure. Runs and idles great.

KValue = 179
Latency = .81
RPM Range=400,800,1200,1600,2000,2400,2500,3200,3600,4000...6800
TTP Min = 6,6,6,5,5,5,4...4
TTP Max = 23,23,40,42,48,52,56,66,73,117...117

[ I am not responsible if you use these settings and damage your engine or ECU. You use these at your own risk as these settings have not been verified to AFR and may not work for your engine setup. ]

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