I'm exceeding 100% duty cycle and I guess I need new injectors, right? It peaked at 102% @ 7500RPM. Can the pulse width be changed or do I just have to buy new ones? I would assume it can, but it would lean me out?

 

Over 100% IDC is not uncommon on stock injectors. I've seen 102% at 7000 rpm.

 

extremely high IDC's are often a result of being tuned overly rich. However, If you keep adding fuel to the car to resolve a lean condition and the car doesn't get richer but the IDC's keep rising... that's a good indication that you're out of injector or there is another fuel supply issue (dirty filter, kinked fuel line, botched fuel pump or install)

 

Bringing back an old thread....


I just installed a sc61 with a 44mm tial on a turbo trix manifold.. I started out at 10 psi and logged and monitored the wideband.. I stopped at 21 psi with 10.0 A/F ??? Does that even seem possible on stock evo 8 injectors?? I realize at 7100 rpm according to the formula im at 111% IDC which I need bigger injectors.. But from 10 psi to 21 psi my a/f stayed right at 10.0 flat.. at idle it was between 14.5 - 15.0 .. And fluctuated the whole time I drove and went rich as I floored it to 10.0 .. Is something up with my wideband? Something doesnt seem right .. any input would be app.. Wide band ia an AEM Uego and it was used for a couple months from another evo.. Thanks

 

No, both MJ and I noted that you could run the stock injectors fairly ragged and still keep the car plenty rich. I got up to 19 psi with my 35R on the stockers before I swapped out to my 780s. The car ran 11.0 before and after the injector swap (with tuning, obviously). It was also making great power on the stock injectors, raced a buddy's T67 SC300 that traps 120 and he had a very hard time getting away.

 

but at 6000 rpm I am at 94.5% IDC.. Wouldnt I start to lean out as I brought it up to 7100?? It stayed at 10.0 the whole time.. Ran from 2nd to 3rd and to 100mph in fourth with a count of knock between shifts and one count as my wastegate opened.. Thats it.. 0 knock in 4th to 100mph.. (on a track)

 

Remeber the Injectors are working at 513CC, and the calculation in Evoscan is the same thing. 100% represented there is more lik 90%

 

ahh nice insite pheonix!! I also have a snow meth kit (not installed yet) I know this kind of "adds" fuel to the mix. So why is everyone changing out injectors if im at 90-95%?? Once I spray meth wouldnt it be less work on my injectors? I see alot of guys runnin 880cc for their 35r, but I was told by mulitple people that 745cc and meth would be sufficient..


I also have a 255 walbro .. I would assume thats helpin in feeding this pig.

 

Actually the Injectors are scaled at 513 but are 560's.

edit- read Phenix post and grokked it and realised I said the same thing he did. I lose at life.

 

bump for more answers ....

 

How is everyone determining IDC? Via Evoscan? Or by logging IPW and doing the calculation manually?

Is IPW in mitsulogger/evoscan actual pulsewidth or just an estimation based on injector size and latency?

I ask because I was logging 21.5ms IPW @ 6000rpm, which came out to 107.5% IDC. AFR was 11.8:1 and I could do nothing to richen it up. I dropped those cells 2 full points(from 10 to 8) with no change. I installed some 745cc injectors, adjusted scaling and latencies, and now I have much more control over fuel above 5500rpm. I had to add those 2 points back to get it to 11:1. So I believe I definitely ran out of injector. Now I'm logging around 16ms IPW @ 6k rpm which is about 80% IDC.

 

MixMaster, is your 357whp at The Shop, cause if so, those numbers are scaled to DynoJet levels.

Also, how happy are you with the GSC's ? Did they give you a noticeable gain?

I'm thinking that with such poor cam results on IXs, I may skip them and go straight to a 20G-9LT

 

I log IPW and calc IDC from it and RPM. IPW is read from the ECU. It is interesting that the ECU will report more than 100% duty cycle. There's no reason why it should because anything over that means the injector is open all the time.

Sounds like you maxed out the old injectors (stock?). Not surprising with your power level.

 

Lol I forgot to mention there 560CC. Lets just say you added to the idea.

 

the size of the injector has nothing to do with the injector duty cycle calculation. it is purely a relationship of injector pulse width, and RPM. nothing else.


so if you are at 17ms injector pulse width, and you are at 7000 rpm, you are at 100% injector duty cycle regardless if you have 560cc injectors or 1000cc injectors.


so no, if it really is a duty cycle calculation and it says you are at 100%, you are at 100%.