I suppose if I:

Used 85% instead of 82% IDC
Used 4 bar fuel pressure instead of 3 bar
Used 11.5:1 instead of 11.1:1

... then I would have 24% more power potential out of my present fuel system (not including the slight increase in power from leaning out 0.4 AFR points). As long as I have more than 323 BHP at present then that means this setup with a FPR should be good for 400 BHP. Theoretically of course But a few small changes quickly compound. So maybe 550s would do the job for you Baz?

Never understood >100% IDC, can someone explain? I know some ECUs report it, but are they taking account of the fact that opening an injector takes longer than closing one and measuring it in a different way? Electrically a 100% duty cycle is continually on, you can't have it more on than all the time? What does it mean?

Anyone know up to what point the fuel delivery is fairly linear? 85%? 90%? When do they usually go static?

[Edited by john banks - 11/28/2002 8:19:14 PM]

 

think they go static at around 90% +. But it will depend on the injector, low impedance can be driven faster (lower ramp up/down times) so would go to a higher DC.

I was told there is a risk that at the point the injector goes static, that it will go static at 50% open. However with all the modified scoobs on 380 injectors running with around 300hp, I doubt this is the case with the paticular injectors used on the scoob.

I still think you are going to have to go some to suddenly be at 400hp without warning!

Paul

 

i am not sure why some ecu just display that. however it is most likely because most software calculate the duty cycle from an pulse width X the multiplier of that pulse width ( very difficult to explain in writing oops) so the programme is probably just multiplying few numbers and coming up with the IDC. eventhough the injectors are not open anymore. it is just based on an assumption.

 

probably based on how long it's trying to open them for. Obviously no extra flow once 100% is reached.

Evos do seem to have a higher BSFC, or perhaps the scoob is lower. Could this be a thermal efficiency thing with the alloy block? Who knows.

Paul

 

very true paul. the evos come with 560s as standard! the what size do the sti7 run?

 

850's eh ! If I fitted just 2 of these I'd still be overfuelling

 

Interesting stuff guys, based on the above i think i'll stick to 550's - for the meantime

 

let me know what you need and I will try and sort you out.

Like i said before, if you want to upgrade, selling them shouldn't be a problem.

Paul

 

Paul


YHM

 

Sam,

560 x 4 = 2240 x 93% = 2083 div' 360bhp = 5.78cc per 1 bhp.

680 x 4 = 2720 x 66% = 1795 div' 380bhp = 4.72cc per 1 bhp.

Assuming that your power figures are correct, and we all know accurate the Star RR is then had you have run the same fuelling on the 560's, as the 680's,

360bhp x 4.72cc = 1700cc

1700 = 76%idc on 560cc injectors.

Something doesn't quite add up ?

Mark.

 

Mark

I'm not sure that you can take the Injector duty % 'drive on' time and expect it to relate exactly to the actual injector 'open' time for different makes/designs of injector.
That might explain Sam's results ?

Andy

 

the other thing is the FBR is different. i would assume the the HKS item allows you to hold the pressure better at the top end.


also you are assuming that i am running the same mixtures , the first figures were not mapped by myself and i didnot have a wideband to measure it at the moment.


so there is a lot of variables that we can't really account for.


sam

 

Sam/Andy,

What I found interesting, is that based on Sams figures, it indicates that he is now using 18% less fuel per 1 bhp, to produce 380bhp, than he was to produce 360bhp.

Whilst the FPR was changed, the FP was set to the same 3bar, and Sam said that he was running the same AFR(.78 lambda/11.46:1 AFR)

Injector "on time" will have an effect, but I think this will be minimal between similar injectors. It certainly wouldn't account for an 18% disparity in the fuelling.

Unless the original fuel reg' was faulty, I can't see how this would effect things. Changing the fuel pump to an up rated one, certainly could, but that had already been done.

I'm not questioning the power figures, but I'm just wondering if the 380bhp was purely down to running a leaner AFR, which is what Sams figures indicate ?

Mark.

 

I would, especially if Sam mapped it

 

Meoooww!

 

keep your hand bags ladies


sam

 

C'mon guys, i can't feel any love in the room

 

another thought though,

when i fitted the uprated injectors, i also uprated teh fuel rail, the fuel lines ? surely the standard evo lines and rail are not that restrictive?