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Old 11-28-2006, 12:07 PM   #1
Turbo_Mike
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Default Seeing well over 100% IDC.... car is stock

Just like the title says, car is stock minus perrin EBC and a catback and at 14 psi I see 103% IDC and at 18 psi I'm seeing as high as 108% IDC. This is with stock turbo, stock intake, only seeing 4.5V at the MAF.... dont really know why its doing it. Is this normal??

Car made 231 wheel on a dynojet with 11.8-12.1 A/F all the way through 7k.... but now that I'm logging it it looks scary to see over 100% on the injectors without doing any mods yet.... do I need bigger injectors already????
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Old 11-28-2006, 04:02 PM   #2
Master2192
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A couple of questions I've got.
1. How are you logging Injector Duty Cycle? My guess is it is a calculation error because IDC can't really be over 100%
2. The A/F ratios seem off, it should be much richer than that. I am thinking since you've still got your cats that the dyno could not get an accurate reading on AFR.
3. What tune are you running? I know the car is pretty much stock but you didn't mention what reflash you have.
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Old 11-28-2006, 07:37 PM   #3
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IDC CAN be over 100%. Injector duty cycle is just a calculation based on valve opening time and if you turn the injector on before the valve opens and is open for a total time longer than the valve you have > 100% IDC. Sometimes the calculation starts and doesn't take out the injector dead time so you will have artifically inflated IDCs. Rule of thumb is that % calculation has a lot of error since the RPM pickup is also subject to error. For 231 whp on stock injectors I'm not surprised you are running that high so it appears normal to me.

The AFR is not off. You are maxing out the injectors and thats probably as rich as you can keep it. Not too lean but I wouldn't be confident seing any leaner than that. Cats also don't change AFR readings a whole lot, I've personally witnessed this comparing tailpipe AFRs to downpipe AFRs.

BUT yes to the original question do you need bigger injectors. Most definitely.
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Old 11-28-2006, 09:37 PM   #4
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Quote:
Originally Posted by cdvma
IDC CAN be over 100%. Injector duty cycle is just a calculation based on valve opening time and if you turn the injector on before the valve opens and is open for a total time longer than the valve you have > 100% IDC.
I was under the impression that 100% IDC meant the injector was static, meaning it is open and doesn't close at all during the engine cycle.

Edit: Upon further investigation I found out that you are correct. IDC is the injector latency plus intake valve opening time and whatever other offsets the ECU is using.

Last edited by Master2192; 11-28-2006 at 09:58 PM.
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Old 11-29-2006, 10:39 AM   #5
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Yeah.. I was also under the same impression. I thought it was the time the injector is open before neededing to be opened for the next fire at a given RPM. I'm not convinced it's related to your intake valve.

http://toyotaperformance.com/airflow.htm

If this is correct, then > 100% is very easily possible, but not a good idea.

Perhaps the IDC being recorded in EcuExplorer is a different calculation than the standard IDC. That is, assuming your using EcuExplorer.

+1 for calculation error/difference.
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Old 11-29-2006, 11:13 AM   #6
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I've found that the IDC goes over 100% for a stock motor with turboback.

This is logging using the EcuExplorer and using the Street Tuner software.

Cobb Stage2 map seems to use the same fuel curve as the stock map so it tends to run overly rich under boost. So even if you end up running a little leaner than stock because the injectors are static it should be fine.... maybe..

Getting a good tuner to tune your car will bring your IDCs down to around 80-90% at 16psi.
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Old 11-29-2006, 04:47 PM   #7
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How exactly do they pull that off?
Scale the injector numerator up or the MAF table down, you will have less duty cycle. Thats the only way I can think of doing it.

I logged with enginuity, ECU edit, and ECU explorer, all giving me over 100%. I suppose on the dyno I can play with it more to get the IDC down so I dont burn out the injectors and just watch the tailpipe A/F so it stays in check. I would think thats how a "tuner" is going to do it.
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Old 11-30-2006, 02:04 PM   #8
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Quote:
Originally Posted by Revision View Post
I've found that the IDC goes over 100% for a stock motor with turboback.

This is logging using the EcuExplorer and using the Street Tuner software.

Cobb Stage2 map seems to use the same fuel curve as the stock map so it tends to run overly rich under boost. So even if you end up running a little leaner than stock because the injectors are static it should be fine.... maybe..

Getting a good tuner to tune your car will bring your IDCs down to around 80-90% at 16psi.
I ran 21psi and had no problems. You come into some trouble at redline.
This is because the stock turbo cannot hold boost in the upper rpms...I think I was only able to acheive 15psi or so. So at 6500rpm and 15psi = near 100% IDC. It doesn't matter how much boost you run down low at full boil you won't max them out down there typically with the stock turbo.

Like I said, I ran 21psi and was only at 80-some% IDC in the lower-mid rpms.
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Old 11-30-2006, 02:34 PM   #9
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Quote:
Originally Posted by Turbo_Mike View Post
Just like the title says, car is stock minus perrin EBC and a catback and at 14 psi I see 103% IDC and at 18 psi I'm seeing as high as 108% IDC. This is with stock turbo, stock intake, only seeing 4.5V at the MAF.... dont really know why its doing it. Is this normal??

Car made 231 wheel on a dynojet with 11.8-12.1 A/F all the way through 7k.... but now that I'm logging it it looks scary to see over 100% on the injectors without doing any mods yet.... do I need bigger injectors already????
pulling 4.5mafv with a td04?

not bloody likely!

i suspect a boost leak.
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Old 11-30-2006, 02:37 PM   #10
Turbo_Mike
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My turbo will hold 19 psi at 7000. Dont ask me if this is good for it but it will do it. I used to run an aftermarket short ram that only read 4.1 volts at redline but once I went to higher boost it was too much timing and it pinged. So I reset the ECU, went back to stock intake, and now its higher MAF reading and maxing out the injectors. Guess I just gotta get on the dyno and see how rich it is...

Have you modified the MAF scale or the injector flow rate?

hmmm boost leak you think?? I cant hear anything leaking and I had the intercooler off last weekend to take a look how my stock plastic tube was doing and it looks fine....
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