1FooknTiteFD

So i went out on a spirited drive in the mountains last night with my friend upon stopping, I noticed that the peak hold on my power fc for my injector duty was at 100%! I have never ever seen my injector duty so high, I was only running .7kg boost (10psi) during the uphill run. Knock, air temperature, and all other readings were stable.

When I go WOT on the freeway up to redline, the duty is only around 80%. Does anyone know why I am running such high injector duty and what I should check up on? What's usually the "safety limit" as to how high it can go?

Fd3BOOST

iTrader: (7)

I think the general rule of thumb is keep it under 90% I used to hit 100% on my old set up all the time though and I was lucky enough not to break the engine. I would not even try that now with the t04. If you are hitting 100% in the summer at 10psi you are going to be in bad shape when it gets colder and start getting boost spikes.

Snook

iTrader: (12)

you probably went into higher rpms on accident than you do on the highway
On my first 11s run in the 1/4 mile my car nearly cut off it bucked so hard in 1st gear because I had such a good launch and the 1/3 tank of gas sloshed, then later that run in 4th I hit 100% duty cycle. I was very lucky and I didn't ever let that happen again. 1600s, 850s, 2 supra pumps

Kento

During the "spirited drive in the mountains", you were probably spending a lot of time in the lower gears, where the rpm gain is so quick that the ECU (PFC) must dump fuel to keep up.

1FooknTiteFD

Thanks guys, a lot of what you all said makes a lot of sense....

I tried blasting on the freeway with higher boost (around 12psi this time) and the maximum it ever hit was 80% after i revved it up to 8000rpms

potatochobit

iTrader: (1)

u have the apexi single turbo? its true that the injectors max out at 15lbs stock, but with a large single, i could see a load being placed on them when changing gears alot being fully spooled up.

1FooknTiteFD

I am using stock 550 primaries and 1300cc secondaries. The injector only have about 35000 miles on them. The fuel pump is also brand new and my car has been dyno tuned before

technonovice

What AFRs are you running at when you hit 100%? Thats what I'd look at first.

Mr rx-7 tt

iTrader: (5)

What injectors are you running?

technonovice

Look up three posts up...."I am using stock 550 primaries and 1300cc secondaries."

1FooknTiteFD

AFR is at about 10.8

Fd3BOOST

iTrader: (7)

Thats pretty rich. Who tuned it?

technonovice

Exactly. You could dial that up and have higher injector efficiency. That would be safer in the long run. You are needlessly giving up power at 10.8.

1FooknTiteFD

XS-engineering tuned it. It still made 380rwhp on 91 octane even though it's a little rich

technonovice

Well its not just a matter of wasting power, but what duty cycles are you seeing in general at WOT? I would not feel comfortable running over 90% inj duty cycle or an extended period. Besides if you can gain some power dialing back the fuel then you could dial back the boost a tick as well. making it all just a bit less stressed.

fdeeznutz

That explains why I always spike to 100% in first gear then never go above 80% 2nd through 5th.

1FooknTiteFD

I've only seen it hit 100% once. Usually when I'm on WOT it only goes up to 80% when I rev it up to 8000rpms.

1FooknTiteFD

Ok guys, went on another "spirited drive" last night and at WOT it recorded a peak of 94%. Still too high for comfort. Anyone else have any ideas? I am at a total loss here. Everything fuel related on my car (including fuel pulsation damper, pressure regulator, injectors, pump, fuel filter) has under 40,000 miles on them. This is getting frustrating

technonovice

Where was the peak as far as how long you were unto the throttle? What is your afr at that point?

Kento

As I pointed out in a previous post in this thread, were you ever accelerating in 1st or 2nd gear during this "spirited drive"? With your a/f ratios set in the 10s, your ECU will be dumping as much fuel as possible because the engine is revving so quickly, resulting in high peak injector duty.

technonovice

AFRs in the 11s are well enough.