GDBSTi

Anyone experienced on/off throttle transitional detonation after fitting 500cc STi injectors and parallel fuel rail to a 2001 WRX.

Knock Link lights up momentarily at the moment when I apply full throttle or when I lift off throttle. This only happens when there is no load (boost on vacuum), no lights when on boost in all gears right through the rev range.

I think it might have something to do with the resonance in the braided hose fuel rails or something when the fuel pressure builds up or drops. I am using a adjustable fuel pressure regulator set at 3.5 bar. Not sure if this contributes to the problem??


rupert

dowser

Did you remap around the new injectors? There are dedicated maps to change injector parameters from memory (assuming you're still on OE ecu).

Fitting larger injectors and upping fuel pressure will be injecting waaay more fuel than required...dangerously so, I would imagine, if not mapped around.

Have you checked that fuel pressure is being maintained through the boost range? I assume you fitted a better pump too? What does a wide band show at the det points?

Richard

GDBSTi

Richard

Yes ECU has been rescaled to 540cc to take into account higher fuel pressures, lambda never exceeds 0.76 on boost (Motec PLM), running 180L/hr uprated fuel pump (not so happy with this though). The car ran same boost (VF24, 1.4bar midrange tappering to 1.2 bar 6000rpm), timing etc before rails and injector mods , but 115% IDC from 5000rpm and plenty of red lights ment uprated injectors were neccessary. However it never had this full/off throttle transitional detonation before rails and injectors. Also Delta Dash shows ignition correction never below 6 Degrees.

rupert

[Edited by GDBSTi - 12/18/2003 7:34:35 AM]

dowser

There are also injector timing maps to play with (to suit different opening/closing characteristics). Maybe check the difference between these parameters for the stock WRX and STi maps?

What's the resolution of the Motec WB? Could it be missing the event? I'd monitor fuel pressure as well during the throttle transients to see what it's doing (tape the FP gauge to the windshield though, don't feed it into the car ). Tap into the line after the fuel rails (assumes a separate regulator).

Also note that fuel pressure alters spray patterns significantly - upping FP by 1 bar on a classic with 440's saw a significant difference between low and high rev correction requirements. I've not played with injector or pressure changes on the later cars, but EcuTek's scaling feature is linear (with flash99) and will still need further tweaking.

Richard

EMS

I assume your mixture is too lean at medium load. Did you rescale to 540 cc in Delta Flash? If yes, this is WAY too high value. Normally I stick to something between 450 and 500 with those injectors. (you have to change the last columns of the fueling to get it right)

Mark.

AndrewC

Have you read this 22b thread.

Andrew...

GDBSTi

Thanks for the help chaps I will try the suggestions