High Injector Duty

[1FastFWD]

ok guys... i have the maf translator and i am currently running 650's, 14b at 15psi, 190 walbro, FMIC, 3in. turboback with o2dump. right now i have my maft set to 650's and im have a HIGH IDC. at 6250 RPM im at 92.9% for my injector duty. my ftrm is 100.7% and my ftrh is at 97.6%. why is my duty cycle so high on a 14b?by the way the setup is on a 1g FWD.

 

[94Jettameowpsst]

It could just be that you still have the stock fpr. I know i have 450's and at at 16psi at around 5500-6k rpm, my idc is around 90%, i dont understand why your idc is so high considering 650's. Im lead to believe you either need to just swap your fpr or rewire ur pump if you didnt already. Tomorrow ill be putting the fpr from my auto onto my car and see if that helps, hey its only 5-6 more psi, but hopefully it'll help.

 

[1FastFWD]

yeah i still have the stock fpr....im probably going to get an aeromotive fpr. thanks for your help. and also...does the walbro 190's have to be re-wired? or are they good how they are?

 

[94Jettameowpsst]

regardless of the fuel pump you have, it should be rewired because the factory power wire is TOO small.

 

[steve]

I am currently running 650's, 14b at 15psi, 190 walbro, FMIC, 3in. turboback with o2dump. right now i have my maft set to 650's and im have a HIGH IDC. at 6250 RPM im at 92.9% for my injector duty. my ftrm is 100.7% and my ftrh is at 97.6%. why is my duty cycle so high on a 14b?by the way the setup is on a 1g FWD.

Fuel trims only apply during closed loop and your typically not in closed loop while boosting and never under WOT.

IDC is derived from IPW and RPM. The ECU computes IPW from airflow and RPMS. Clearly the ECU thinks you need quite a bit of fuel from the airflow signal it sees. I wonder if it's all getting to the cylinders?

In other words, time to check for boost leaks. Any air leaking out will raise your IPW over what it should be.

Steve

 

[1FastFWD]

i have checked for boost leaks and the only leak i have is from the throttle body but almost every 1st gen has the prob.

 

[steve]

Ok, your right most of these 10 to 15 year old cars have worn out throttle shaft seals, I replaced mine and it doesn't leak there anymore.

What pressure did you test to and how long did it hold that pressure without needing additional air.

Steve

 

[1FastFWD]

UPDATE: bought the aeromotive FPR and i have the pressure set at 43 w/ vac hose off. my injector duty cycle is still in the high 90's.....no boost leaks except for the throttle body and when i do a boost leak test it falls off kinda quick and holds only 5-7 psi. so i still have no clue why my inj. duty cycle is still so high. should i raise my fuel pressure? or set my maft to a smaller or bigger size of injectors?

 

[ltho98]

What are you using to monitor IDC?

650cc is a HUGE injector for a 14b (as I run 650cc on my 50-trim and am still seeing 80% IDC)

In any case, you could be running her pig ass rich too which is why you're IDCs are so high.

 

[1FastFWD]

then should i turn down my fuel pressure??? because if i lean it out on my maft then it knocks like hell.

 

[steve]

no boost leaks except for the throttle body and when i do a boost leak test it falls off kinda quick and holds only 5-7 psi.

You mean no other leaks you can find. Those numbers suggest you have some sigificant leaks still. More than what I would expect from just throttle shaft seals.

You should run the stock 1G base fuel pressure if everything else is correct and not have 90% DC on 650s.

Steve

 

[1FastFWD]

thats the only leak me and my friends could actually find....i checked every clamp on the pipes...ive checked all the injector seals...the throttle body shaft is leaking pretty good...but i wouldnt think it would cause my high duty because my friend did a 6 bolt swap in his 2g and his leaks the same and he has good #'s...i guess i could go get a new seal and replace it.

 

[steve]

If you not able to pressurize the intake up to your boost pressure and have it hold, then when the car is running metered air is going to be leaking out rather than going into the cylinders. Since the ECU doesn't know that it's leaking, it's going to add fuel for all the air that was metered.

Result. Turbo has to work harder to keep the boost pressure up, ECU keeps the injectors open longer to deliver unneeded fuel and the car runs rich, with hotter charge temps more likely to knock, less timing since the ECU thinks your under higher load, and performance isn't what it could be.

Soapy water works wonders helping you see where things are leaking. Remember to check the PCV valve to make sure it's isn't leaking into the valve cover and listen to make sure the engine didn't stop at a point where one of the cylinders is in overlap.

Steve

 

[Reese92tsi]

Did you change the fuel filter?

 

[RoasT BeeF]

Remember to check the PCV valve to make sure it's isn't leaking into the valve cover and listen to make sure the engine didn't stop at a point where one of the cylinders is in overlap.

Why would this matter? It all should stop at the throttle plate anyhow...

 

[steve]

Why would this matter? It all should stop at the throttle plate anyhow...

Does your car idle when the throttle is closed?
How does the air reach the cylinders if it all stopped at the throttle plate?

If air can leak out of worn throttle shaft seals, do you think the various bypass passages pose much of a problem.?

Steve

 

[ltho98]

Idle Air Control Valve

 

[steve]

Idle Air Control Valve

That's one of them (The ISC or IAC), the others are the BISS, the FIAV (when cold) and the little air that goes through the throttle body bore since the plate isn't 100% closed (the IPS on a 1G or the Fixed SAS on a 2G is adjusted to hold the plate slightly open from the factory).

If you want to check this on your own, just look at your boost gauge during the pressure test. Most people have it tapped into a line from the manifold. If it reads any pressure then air must be flowing around/through the throttle plate to reach the manifold and pressurize it.

Brent, does this make sense now?

Steve

 

[RoasT BeeF]

Yeah.

I dont know what I was thinkin...

 

[1FastFWD]

i used soapy water and sprayed EVERYTHING no leaks at all besides that throttle body shaft seal and i honestly think that the seal is causing this problem.....i have my maft set to 650 cc injectors....should i turn it to smaller or bigger injectors and raise or lower my fuel pressure?

 

[93DE-EZ-UM]

i used soapy water and sprayed EVERYTHING no leaks at all besides that throttle body shaft seal and i honestly think that the seal is causing this problem.....i have my maft set to 650 cc injectors....should i turn it to smaller or bigger injectors and raise or lower my fuel pressure?

Did you ever find the solution to your problem? My car have the similar condition youe've describe.

Thanks.

 

[dnhieu]

why dont you just rebuild the throttle body? its not that hard and vfaq has a wright up on it. if you strip the tb plate screws dejontool.com has them to purchase you will just have to email him