Was wondering what you guys were seeing at idle. I was seeing 1.6-1.7 and then ~2.2 with the A/C on. Then my car started running a bit rich today from some reason.... tripped the 0706 code on the ecu. And now it's reading 2.5-2.7 at idle on the duty injector cycle.

Khiem

1.5-1.6 with JWT C series cams idle stability program. 950 rpm idle.

Originally posted by 92SE-R
1.5-1.6 with JWT C series cams idle stability program. 950 rpm idle.

What injectors are you using?

Steve

I'm using 370ccs. Sorry to mention that! I suppose that does make a difference doesn't it? Well, I made sure I cleared all the codes from the ECU, even disconnected the battery overnight and its back to 1.6% at idle.

Khiem

Are these all CMX readings?

I have an MDM-100 and I get 2.3-2.4 ms injector pulse durations at idle.

Originally posted by spdracerUT
I'm using 370ccs. Sorry to mention that! I suppose that does make a difference doesn't it? Well, I made sure I cleared all the codes from the ECU, even disconnected the battery overnight and its back to 1.6% at idle.

Khiem

Is that % or time in milliseconds?

Steve

Just to add some info, I have the MSD 50 lb/hr injectors and with the Techtom MDM 100 I was reading 1.9 ms at idle.

Does anyone know what the maximum duty cycle is for these injectors or where I might find that out? I'd be interested to know how much room is left at WOT.

Steve

I'm reading off of the CMX, and it's in %.

CMX in % and 370cc

Those of you with the MDM-100, what is the correlation between the miliseconds and % injector duty cycle. How do I make sense of the millisecond values ?

Originally posted by art_from_ct
Those of you with the MDM-100, what is the correlation between the miliseconds and % injector duty cycle. How do I make sense of the millisecond values ?

Easy answer: You do not!!!!!

More complicated version:

The Injector Duty Cycle (in %) is defined as To/Tav, where To=time injector is On (what you get in MDM100) and
Tav=time available until next injecion event occurs.

As rpm goes up, the available time decreases (at 2000rpm you have 50% as much time available as in 1000rpm since you have twice as many injection events).

Nice table-like info at:

http://www.ecanfix.com/~mdhamilton/dutycycle1.html

Chris

Thanks Chris, enlightening answer, now I got another one for you, ;) what value would this time injector is open in millisecond have to tuning/troubleshooting ?

Tuning not much I would think.

You can just "watch" so On time in ms does not exceed any value that corresponds to more than 80-85% duty cycle so as to avoid the possibility of going static. But I suppose this was taken care of when deciding on the size of the injectors.

You need to do some calculations though. For example, the available time for injector-ON at 7500rpm is 16ms. So if you see at WOT and close to 7500 anything like 16*0.80=12.8ms then you are close to the limit of the injector.

Chris