Duty cycle increases as car warms up, why?

[Poik]

When I start my car cold it idles around 13-14:1 with about 1.15mS injector time, duty cycle shows 3.2% or so. When it warms up, I can't really get it to idle any leaner than 11:1, and the duty cycle goes to about 3.6% and injector time around 1.2mS. This doesn't make sense to me, seems like it should be injecting less fuel as the air and engine gets hotter?

[Matt Cramer]

Usually it is. But if the RPM is rising and the pulse width stays the same, the duty cycle will go up. A bigger question is why it needs to be so rich to idle, although if you're with an MS1 that is close to the limit of its resolution at idle.

[Morten VJ]

A screen shot of the WUE entritchement would help.
Or an Msq.
What code do you run??
With thise low numbers even the Hires ekstra code have problems.
I would not reccomend anything below 1,5 ms at idle.

[Poik]

I am running high res 10g, I am running 65lb/hr injectors. RPM at idle stays the same when warm or cold. I just think it's weird that I can't get it to idle at a good AFR when warmed up, I didn't think these injectors were monsters or anything. Not a huge problem, just kind of annoying.

[gsellstr]

I can't get my 140 to idle worth anything over about 11:1 either, hot or cold. Granted it's got 42#-ish injectors, but it just plain ain't happy and it'll sit there surging like nothing else. I also don't have idle control though.

It is slightly odd that the AFR's drop though. Sounds like WUE may be wacky or something though.

[fryea]

how much advance are you running at idle, cold and hot?

[Poik]

Like 19. I just got it to idle 12.5-13.5 now, I changed the battery voltage correction from 0.2mS/V to 0.1mS/V and that helped it a lot I think. The car still goes rich by about 0.5 AFR when I turn my e-fan on. It's good enough for government work so I don't think I'm going to mess with that aspect of it anymore.

[Poik]

I am stupid, or a noob. I don't know why the duty cycle thing changes, but I did find out why I couldn't get it to idle at a reasonable AFR! I had MS set to 4 injections per cycle, so I set that to 2 per cycle and then it was easy to get it to idle at 14-15:1. I took it for a little drive and it was running real lean all over, so I scaled the VE table up a little bit and it is decent. Wish I would have found this out earlier, my VE table was just getting perfect, grr..

[500dollar744ti]

4 injections per cycle- a good way to make your gas gauge move like the second hand on a clock.

[linuxman51]

if you change injections per cycle and the car goes rich/lean, your injector opening time is not correct.

[500dollar744ti]

also can be a product of worn out injectors.

[Poik]

if you change injections per cycle and the car goes rich/lean, your injector opening time is not correct.
Yes I realized this. I'm going to see if Racetronix has the specs on these injectors.

[Kuikka]

For me as using old pintle type injectors it's impossible to get the car running under 1.9 ms opening times, but hey I don't need to pass emissions... But I'll bet you are running to the same thing that injectors just don't have reasonable time to operate when on 4 cycles.