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Hey guys just wondering if I should be nervous about my IDC.
I have a 2018 STI pro tuned , with a turbo back Cobb exhaust , and a Cobb intake.
I did a WOT today to see what my IDC is.
it was 99.75% I do have an upgraded fuel pump already ! Should I be worried ??
you've likely maxed out your injectors. If you're not leaning out, you're good. log it and email your tuner.
 

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really? Please, do elaborate. I love learning new things.
IDC is calculated on intake valve opening events. I've personally had IDC up to 137% without leaning out... That is about the time I recommend looking at larger injectors, but if you assumed 137% is static, then an indicated 100% is more like 73% INJECTOR duty cycle.


Send a log to your tuner, they'll know.
Not without a WBO2.
 

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IDC is calculated on intake valve opening events. I've personally had IDC up to 137% without leaning out... That is about the time I recommend looking at larger injectors, but if you assumed 137% is static, then an indicated 100% is more like 73% INJECTOR duty cycle.




Not without a WBO2.
I don’t assume to know if he has a wide band or not. Not sure he knows what he has. My understanding, is anything over 100% and the injector stays open through the duration of all four strokes. If he already has a pump, fuel is bottlenecking at the injector and he would need to get something bigger if he doesn’t want IDC’s that high. But if he’s not leaning out, it’s not an issue. Even though the stock o2 sensors aren’t wideband, would the afr reading though the AP not be somewhat accurate in determining wether he is running out of fuel or not?
 

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Without a WBO2, the tuner will not know what the fuel doing in OL. Specifically the location of the O2 sensor makes it inaccurate, once you get into boost.

True static/100% IDC (not calculated from a valve opening event) will have an injector never closing. AFR's will also lean out with RPM and boost (I have a graph I can post when I get home, of just that). Subaru does not treat 100% IDC as static/always open... If they did, you could never go over an indicated "100%".

Subaru's are about the only car you see people recommending much larger injectors for X power goals.
 

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Without a WBO2, the tuner will not know what the fuel doing in OL. Specifically the location of the O2 sensor makes it inaccurate, once you get into boost.

True static/100% IDC (not calculated from a valve opening event) will have an injector never closing. AFR's will also lean out with RPM and boost (I have a graph I can post when I get home, of just that). Subaru does not treat 100% IDC as static/always open... If they did, you could never go over an indicated "100%".

Subaru's are about the only car you see people recommending much larger injectors for X power goals.
Makes sense why the AP afr pins itself at 11.14. I’ve always just gone by the aem wide band, but it makes sense now. Are the stock o2 sensors not designed to read over or under a certain value? Like only narrow band? Last question
 

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Hey guys just wondering if I should be nervous about my IDC.
I have a 2018 STI pro tuned , with a turbo back Cobb exhaust , and a Cobb intake.
I did a WOT today to see what my IDC is.
it was 99.75% I do have an upgraded fuel pump already ! Should I be worried ??
To my understanding i believe fuel pump will only give you a little wiggle room with the mods you have, what you really need is larger injectors so their not maxed out like they are in your case. All i have is an intake and etune by bren tuning and my IDC is at 93% at WOT with that alone. Before even thinking of going past that its good idea to go 1050cc injectors, 340lph pump, and FPR.
 

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To my understanding i believe fuel pump will only give you a little wiggle room with the mods you have, what you really need is larger injectors so their not maxed out like they are in your case. All i have is an intake and etune by bren tuning and my IDC is at 93% at WOT with that alone. Before even thinking of going past that its good idea to go 1050cc injectors, 340lph pump, and FPR.
Please note the rest of the thread. If you have a stock turbo on gas, do not waste money on upgrading your injectors.
 

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Please note the rest of the thread. If you have a stock turbo on gas, do not waste money on upgrading your injectors.
I did not know that, I have been reading in multiple places people saying being nearly maxed out with turboback and a tune. So I guess 2018 sti (cobb Stg2 91 OTS map) going catless downpipe and turboback is not going to be pushing the injectors either? I am staying with the stock air box. If I go the catless dp route I will be watching out for boost creep though.

Thanks,

Frederik
 

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I did not know that, I have been reading in multiple places people saying being nearly maxed out with turboback and a tune. So I guess 2018 sti (cobb Stg2 91 OTS map) going catless downpipe and turboback is not going to be pushing the injectors either? I am staying with the stock air box. If I go the catless dp route I will be watching out for boost creep though.

Thanks,

Frederik
Yamaha sho is a tuner. He knows that the typical turbo back/intake won’t max the injectors because he’s tuned it.
On top of that (he can explain better. And quite possibly has already in this thread). 100% idc is not a true 100% of flow. You can run these up into the higher 120s and possibly even 130s and still be providing enough fuel to not worry.
 

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It makes sense now that I know about it lol! The fact you can still inject more fuel than for the duration of the valve opening up to a point, and it will still make it into the cylinder. Reminds me of how you can run a 12 cylinder jaguar XJS engine from a 6 “channels” engine management if you run in wasted spark (and wasted injection while valves are closed!) Anyways don’t quote me on that that’s what I recall reading but maybe I’m regurgitating it all wrong. Thanks for helping me learn something!

Frederik
 
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