Injector duty, what do I trust?

[Philv6]

First off I'm running a classic fast system, 63lb inj, TE-63 turbo, double pumper fuel pump & alky. My injectors have always run near 80 percent but over the past couple years with no changes to the motor this has climbed to between 90 & 100. I just figured the pump was getting tired. So I just put in a new pump, filter and new power line to the pump. (pump wires were put in last month) I just went out to test the new pump (45 degrees outside) and my injectors are now running at 110-120 percent. I hoped I might at least still be at 80-90 percent because of the temp. Heres where I'm confused, my target a/f is 10.8 and my O2 numbers are 10.8. (short run but numbers held steady) How can I still be at my target when my injectors are running past 100 percent?
I would like to get out to the track tomorrow with the cool weather (have not been out in 2 years) but I don't know if I will have problems.

 

[norbs]

The seals in the alky pump could be getting old,weaker pressure from the alky. Your alky volume is down so the fast is compensating for it. UNless you flow the fuel system at the rail over a minute period@70 plus psi you won;t know if its fuel related if your alky system checks out ok.

 

[Chuck Leeper]

"The seals in the alky pump could be getting old,weaker pressure from the alky. Your alky volume is down so the fast is compensating for it."
There's another thread about the pump seals...Razor's comments may apply, here??

 

[Philv6]

I should have also mentioned I have one of Razor's first kits and my consumption was down the past couple years. So I replaced the pump with a new one this past spring.
Update.. I made it out to the track Sunday a nice 50 degree day. Since I drove to the track (even left the heavy stock front tires & rims on) I was hoping I could make a few passes and still be conservative on the tune as long as I had fuel. What I did was turn up my fuel pressure even more. (Normal 42, Friday 48, Sunday 54) This seemed to work, my duty cycle maxed out at 96 while I was able to still maintain an a/f of 10.8 and my EGT never got above 1570. They finally said I was done for the day, so after not being out for a couple years the car ran good and drove home. I know I need more injector and thinking back I have bumped my target a/f to the richer side which is why my duty cycle has gotten higher. I know duty cycle as high as mine is bad but I can address that this winter.

Back to my confusion.....I guess I must not understand the real meaning of the injector duty cycle. How is it that I was able to record a duty cycle over 100 percent (110-120) and still be able to maintain my desired target ratio?

 

[Chuck Leeper]

Lucked out!

"I guess I must not understand the real meaning of the injector duty cycle. How is it that I was able to record a duty cycle over 100 percent (110-120) and still be able to maintain my desired target ratio?"
The added Fp makes the injs run at an elevated "value".
@ 54psi, the 63# inj is now operating @ 70.2#/hr.
Sounds like the alky, and the added FP, was "your saving grace"....
DC over 100% is a commanded/calculated value. Once at 100, U R done!
Might you have looked at the plugs? I'd bet they are not "happy".
Time to step up to some 95's!

 

[imaboa]

I would guess, that depending on the Engine Management Software, not having a correct injector dead time entered into the map could give you a mis-calculated injector duty cycle. Not the cause to your problem, but a reason that you may see injector duty cycles over 100%.

 

[Philv6]

"Sounds like the alky, and the added FP, was "your saving grace"....
DC over 100% is a commanded/calculated value. Once at 100, U R done!
Might you have looked at the plugs? I'd bet they are not "happy".
Time to step up to some 95's! "

Thats what I thought...over 100 percent and they were done and anything over 80 was still pushing it. My plugs looked OK (no melted electrodes) just black from the rich mixture I usually run on the street. Once again it has been a couple years since I changed them. The problem with my combination is that everything is old and maxed out. When I change one thing it will be time to a lot. Next thing to ponder is what size injector...........
Thanks all that replied.

 

[northerngn]

1 st thing
colder air will demand more injector, thats a given
ask me i live in minnesnowda

2nd i am agreed with the prev stated above 100 means your done
at 100 d/c the injector never closes
it is physically and mechanically impossible to have over 100%

that a classic fast thing

i have xfi and when my d/c when to 100% it turned on the ses light and set and injector d/c limit code
cool huh?
now i am runnig 83's at 85% d/c on a stock motor

its the e-85...hehehe

-dan