Maxing Injector Duty Cycle

[gslender]

No, IDC is only a calculated number which uses IPW and RPM as inputs and that is why it can go over 100%.

Maybe in your world, but I've never seen IDC only involve PW and RPM. It has always been (for me) a calculation that includes deadtime. After all, the injector has to wait X ms to open before fuel is sprayed out. That can sometimes be a fair amount of the total time, and as you'd expect, will impact IDC if set wrong.

If you think available open time is 20ms but deadtime is actually 2ms then you've got 10% less than you really do, and so your IDC calcs will be wrong or invalid in that case. A correct or valid IDC must include deadtime to be of any value.

G

[Dan]

I understand deadtime factors in too, I was simplifying things.

I was addressing you saying that IDC can only go over 100% if deadtime is wrong.

[NitroDann]

Lol at correcting Grant re: how ecu's work.

[Dan]

Honestly I'm all for learning if I'm wrong, I think I'm correct in saying that though.

[gslender]

I was addressing you saying that IDC can only go over 100% if deadtime is wrong.

Sorry, was trying to suggest that if AFRs are correct and duty is above 100% then the reason is due to deadtime being wrong.

Obviously if the AFRs are wrong, then you might just have the wrong sized injectors and yes trying to command a duty at 110% which is clearly not possible. Another option is that the chosen ECU is wrong and telling you the wrong information (that's possible as ECU developers are not always perfect!)

G

[NitroDann]

You are right in a way, the ACTUAL duty cycle cant be over 100% however due to dead times the ecu calculated DC may be.

Im just stirring you because Grant is the absolute man when it comes to understanding how the ECU is thinking and behaving.

Dann

[Dan]

All good, I understand you can't go past static on the injector

[Magpie]

900 meters

105% on the reactor is possible... but not recommended.

Go to 105 on the reactor.

[madjak]

Hi guys,

Still haven't had a chance to get to look at the car due to sick kids. I'll hopefully get into the workshop tonight and I'll pull an injector and get the part number. Just to answer a question above, the fuel is 98 octane not e85.

From the above discussion, I figure it must be one of the following:
a) Haltech is reporting a duty cycle that is greater than actual (probably due to incorrect settings somewhere, ie injector sizing)
b) Injector is actually a smaller size than 430cc
c) Engine is using lots of fuel (unlikely)

In terms of air fuel ratio, the tuner mentioned when running fuel at 45 PSI that the engine was leaning out a little at high revs on the dyno and upping the fuel load table wasn't correcting it. He checked the reported duty cycle and said it was high. So we upped the PSI to keep a/f in range which helped somewhat. He commented in surprise that the fuel load table ramped up very quickly from the 4000-5000 mark due to the aggressive cams. He also commented at the end that there were still some fluctuations in the a/f ratios between runs. (btw I'm paraphrasing and my memory and use of the terminology may not be 100%) I have since sent the data log from my weekend run to him and he's tweaked the tune slightly. Given that raising the PSI on the fuel rail helped stop the engine lean out I suspect it is actually a miss-sized injector.

I am planning on getting ITBs for the engine sometime soon. That will involve new injectors anyway. If the injectors are smaller and therefore at their limit I might have to fast-track the purchase! What a shame.

[madjak]

Turns out injectors are part number 195500 4060 which are 265cc nb8b injectors. That would explain pretty much everything i'm seeing!

Looks like some larger injectors are required.

Any issue running at 60 psi for now?

[NitroDann]

Nope, thats fine

[rascal]

Madjak,

Did you end up getting new injectors?

If so what did you go with?

[madjak]

I'm still running the same injectors atm. They are at their limit but running ok. I have some plans that will require larger injectors again so I'll probably hold of until I decide what I do with the engine.

My research was into the EV14 injectors. I'd probably get either the 550cc or even 750cc given that the spray is so good they can still work at idle and at very low duty cycles. I'm sure someone here can advise what is best for any given HP target.

[Magpie]

Are you thinking of using E85, if so base your injector size on the expected HP. For me E85 and 220 hp equates to 725cc injectors.

[Ice88]

If your after a temporary injector.

FS-DEs used 285cc injectors Use them on my 175whp engine just fine. (with duty left over)

Also if injectors are old they may need a clean and service. Which may bring them back up to spec.