I made a few logs with EvoScan and plot the IDC. When I go into ECUFlash I do not see a map for IDC. Is the IDC a byproduct of the AFR used on the tables? What I mean is that what you really tune for is for the AFR and then look at the actual ratio at the wideband to make sure you are where you need to be and then use to IDC logs to make sure they are not max out? (i.e. close or more than 100%).

On the same line when you upgrade the fuel pump; Is the reason for the upgrade is to have a little more room to use a little less IDC and still get the same AFR? That is my deduction from looking at the table but I have never tuned before. Is what I am thinking correct or am I missing something here? Thanks in advance.

 

IDC=Injector Duty Cyle. On EvoScan, it let's you know the percentage of usage of the injectors you are using. You can't change the values of it on ECUFlash, as it is totally based on the size of the injectors you are running in your car.

 

IDC=IPW(Injector Pulse Width)*RPM/1200

That being said, IPW is determined by injector scaling, latency and fuel map entries. A 550cc injector with a 10.0 entry in the fuel map @ 6500rpm will have a much higher IDC than a 850cc injector with a 10.0 entry @ 6500rpm.

Ideally, you want to tune for a safe AFR while keeping IDC's at or below 80%. Stock injectors and higher boost, you'll be seeing above 90% IDC. At that point you've reached the physical limitations of the injector and you might want to look at upgrading to a larger size.

 

Testudo is correct, it shows you how often the injector is staying open... one problem with injectors is that they often go static above 90 or 95% duty cycle, because they haven't even fully closed before they are told to open again.

There are three ways to reduce IDC:

1) Turn down the boost... less air will use less fuel to maintain the same AFR. Do this if your AFR is perfect (11.5 - 11.7:1 on 93) but your IDC is over 100%

2) Lean the mix... If you have some room to play with (ie, you are under 11.5:1 AFR) then you can take some fuel out to try and bring IDC's down

3) Install a high pressure fuel pump and re-tune... the stock fuel pump (moreso on Evo 8's than 9's) cannot supply sufficient fuel for boost over stock levels

 

A fuel pump doesn't change IDC's - you can either get a FPR and make the injectors act bigger by bumping up the fuel pressure or get new injectors.

 

If he's maxed out the stock fuel pump, then absolutely it will.

100% IDC on the stock pump with even a small boost increase is very common on Evo 8's. Adding a fuel pump will allow the injector to flow the proper amount of fuel, and will richen AFR's

100% IDC on stock Evo 8 pump is leaner than 100% IDC on a Walbro... so he will be able to take out fuel and lower IDCs

I've run into this every time I've tuned an Evo 8 with the stock pump... IDCs are over 100 and the top end starts leaning out. Add a walbro, see how rich it goes when it's at 100% IDC, then take out some fuel, lower IDCs, and you have a proper AFR and non-static injectors

 

+1
I have witnessed this same thing, and not only on EVO's. Same thing happened with my Cobra.

 

Yes, that is because the pump can't maintain the 1:1 fuel pressure with boost. The VIII pumps drop have a relief valve that open and flow drops dramatically. That's why I have a IX pump sitting on my garage bench for the last year that I haven't put in yet. I'm still on the stock VIII pump, with cams, at 22psi....pretty retarded.

Anyway, here is a great graph from the AMS fuel pump testing that shows this:



In general, though, if the fuel pump can keep up with the demand, they don't affect IDC values. That's what I think a few of the earlier posts were mentioning. It depends on fuel pressure and injector size.


Eric

 

I just made a plot of my EVO 8 with bolt ons (TBE, Resonated TestPipe and drop in filter) and the IDC (calculated using IDC=IPW*RPM/1200) ended up at over 90% when the car was over 7000 RPM, the highest being 95%at 7187 RPM. Note that the car is not tuned so the AFR was logged as 10 starting from 6K RPMs by my AEM UEGO, and 10 is the lowest the AEM will read so most likely I was at 9.XX at high RPMs. Injectors DC is very high but car is also running very rich.

Here is the log of the pull I am talking about. Boost is stock

 

If you lean out your A/F ratio, you should get down in the 80's. Should be fine.

 

What I really want to do is bring up the boost to about 22 psi. And then adjust fuel or timing.

 

Moving the "lean spool" turn off point from 7000 (factory) to 7900 will bring down those IDC's 7k on up.

Also, I would agree with TeStUdo, at least bring the AFR up top into the 10's before you bring the boost up or you will quickly see 110% IDCs.

 

On the log for that same pull I am seeing timing of about 2 deg at top load and advance as high as 20-22 at 7K rpms. Is that OK? The max load seems OK but the WOT at high RPMs seems very high.

I have seen thread talking about 12 deg timing for EVO 9 by redline but on the EVO 8 the stock ECU is using as much as 20-22. Is that OK? That would be an issue if I bring up boost right?

 

When you turn up the boost you will switch to higher load cells so your timing might not be as high - just have to log it and see if it knocks and tune the loa cells you are hitting.

VIII's are def. more timing friendly than IX's from what i have seen and done, just got to find what works for you.

 

Yes, the VIII runs more timing than the IX, like Bryan stated.

And no, you don't have to worry about it when raising the boost, because you will be in higher load cells then, which will have lower timing numbers. You will have to tune those load cells when you turn the boost up.


Eric