I have been using the following calculation for IDC

(InjPulseWidth * RPM) / 1200

My IDC are getting as high as 123% by 7,000 RPM.

Is this calc correct?

I am puzzled. I have basic bolt on's with an Evo IX (including a walbro). My IDC's are over 100% any time over 5,000 RPM yet my AFR is still 11.8 or leaner. My fuel maps is basically as rich as I can go (7.6)

Is my car really using that much fuel or is the IDC Calc and my Wideband off?

Thanks

 

If your fuel tables are set as rich as they can go and you are still at 11.8:1 AFR, then you are likely running out of injector. Are you able to get richer AFR at lower RPM? If so, then you are out of injector and need larger ones, if not your wideband is probably off.

-Paul

 

Its not physically possible to go beyond a true 100% duty cycle. However, many people see more than 100% (I've seen 108% reported for an Evo VIII) which suggests the scaling of the value read by Evoscan/Mitsulogger isn't quite right. 123% is the highest I've ever seen though, and since you can't get the afr to richen up past 11.8, I'd bet that the injectors have reached 100% duty cycle. Is your car really stock?

 

I can get it to go rich, as during spool and low RPM (3-5) It will go as rich as 10.5 at some points. My car is not stock, it has basic bolt ons, im just amazed I could be using that much fuel. Maybe I will try another WideBand to see if it has different readings.

 

Fuel pump?

 

My original post states that I already have a Walbro. What do you mean by "Fuel Pump?"

 

He means that your fuel pump might be going bad.

 

That is weird because I am able to throw a fair amount of fuel -- no knock with a 23 / 24 psi (peak)....A little knock at 25 psi (peak)....but in both cases there was plenty of room for more fuel IDC in the 60 - 80% range....up at 7000 IDC was 88/90....

Now I don't have a wideband yet, so I cannot tell you my AFRs, but I know I am running richer than when I had the car dynod -- so probably in the high 10's / low 11's...

Sorry I could not be of more help, but you may want to try: (1) a base flash from jestrtuning (~$50) or swapping fuel pumps and see if that solves your problem. I personally would recommend a great base tune to start with and then go from there...

 

If car isn't being pushed to unusual levels or isn't at such an extreem modification level with stock fuel supply (- FP) then it's something. Has anyone else hit 130%?

Maybe the vacume line from FP solenoid to FP regulator is leaking so the regulator isn't holding under boost. Is there anything tapped in there. Maybe it's typical who knows

 

The scaling is correct, its just that the scaling is an interpolation of the data, so its in steps of 1/256 at the high point, if you take all of the calculated values, you will end up with a mathematic result that works out to higher than 100%

The other reason you can see duties higher than 100% is there will be occasions where the injection window is longer than what is allocated by the amount of time based on the formula... In theory, it would mean that the injectors are spraying while the valves are closed, however I don't know that to be the case..

 

Sorry to interrupt with somewhat OT from persons thread here, but the value that is given in our scans, IPW, is a ms calculation based on what?

Ignoring essential determining stuff (e.g. 4cyl, rpm, 4 stroke, ... ), is assumed fuel demand a direct reading of voltage duration commanded by ECU/EFI being sent to fuel i njector, or is IPW mearly a interpolate derived calculation (estimation, ballpark, eyball, justkidding, but seriously is this duration a direct recording)?

Sanks

 

Thanks for the info so far guys. Could some one else with a IX with basic bolt on comment on their IDC and AFR.

Thanks

 

I'll make an OT response, and then leave the thread alone..

IPW is one of the more accurate values since the scaling has enough resolution from the byte value to represent for the most part a correct value.. Remember 1000ms is a second, but only a very small portion of it is used to represent the value.. there would be 256ms resolution in this, more than enough if the scale was one to one.. RPM is the likely culprit..

 

Also I was experiencing this problem with the stock pump, and I just installed a walbro less than 500 miles ago, could it have been bad from the start?

 

you very well could have a bad pump or bad pump install.. You should actually check the fuel pressure at the rail and see if its reading correctly.

On the other hand, you may be maxing out your injectors no matter what, if you keep adding fuel, and your not getting any change in AFR, the culprits I would check are injectors, pump, fuel pressure, regulator, etc..