hesitation at 1bar. vf22, 440cc injectors, denso 300lph.Z4 e

[kunchris]

hello mates!! now i am having abit of an issue.ever since I installed the 440cc injectors and the vf22 4months ago i have been enjoying the sheer power of my BG wagon... but for the past week or so while boosting mostly from 3rd upwards, the car would hit a flat spot, then come back up if i let off abit. sometimes it will fall flat on its face and then boost again. on other times it will boost all the way through the rev range. i am not a guy of flooring the car, i go partial and the boost takes over. but lately it realy is annoying especially joining the highway. i run a version 4 long block with RS: manifold, boost control, coil on plug ignition and green AFM
sometimes i would start up the car, then it refuses to idle. or it will continue cranking over till i press the gas pedal. when it finally starts and i let go it stumbles dead. the only way to make it idle back to normal is to give it a rev till like 5k rpm. which gives a massive stench of fuel, then it will idle perfectly at 1k rpm... this is annoying!!! and embarrassing sometimes. could it be the coils. this problem isnt consistent it comes and goes. the cars boosts today. the day after it misfires in the last two gears. suggestions coils?? plugs are brand new NGK platinum PFR56G gapped at 0.7mm. a month old. i have re-piped and re-piped the intake...there are no exhaust or breather hose leaks

[chuckthefuk]

Thats a long list of symptoms and issues...

Just a few questions to start this diagnosis

- Engine management? Stock ECU? Piggy back? Have you been tuned?
- Gas used? Octane lvl?
- Have you checked your spark plugs?? Are they wet? Do they smell like fuel?
- Do you have a air/fuel guage? Digital like a AEM UEGO or Innovative LC-1? If so what are the readings?
- This may be a long shot but what are the engine codes from the OBDII system if there is one..

-Chuck

[Bookem]

Does your coil on plugs have the built in igniters like 02+ wrx and sti's or older external igniters like "g" & "k" engines?

[kimokalihi]

Check your plug gaps. Sounds like what I was experiencing and then I was told to check spark plug gaps and try making the gaps smaller. Worked like a charm. My plugs were about .040" and now they're .030". The more boost you run the more air molecules packed into the same space and air is an insulator so if you run too much boost the spark can't jump the gap and a smaller gap is required or a higher voltage ignition system I believe.

It's worth a shot. Fixed my hesitation around 15 psi and now I boost to 18 psi with no problems and I had it at 20 psi for a minute. Mine was intermittent to some extent as well. I think it depended on how warm the car was and how cold it was outside and maybe the timing/fueling the ECU was running each time. I think sti plugs are gapped at .028".030". Stock gap on a turbo legacy is .039" but they don't run that high of boost/compression.

[anothernord]

Whoa, I hope you tuned for the larger injectors.

[kunchris]

my 440cc injectors are from a 2001 GTB E-TUNE...with modified rails, and it runs abit rich on closed loop. but not as devastatingly as some of the guys make it be. i get 10lts / 100km...with occasional bursts of power while passing, dunno if that is bad according to you guys. it starts up and idles fine with a hint of water vapour on the tip of my TBE. i made 216WHP at 1.0bar tapering on a dyocomp dyno with no tune. http://www.youtube.com/watch?v=M1qOi...4&feature=plcp. massive power delivery over the poo dirty 380cc injectors. thanks for the response guys. i bought a new fuel filter..will be taking out the coils tomorrow when i am free. thinking of GTB coils too!! would they work? as for the AFM there are no codes and the car dies when its unplugged..so i guess its sound? as for the hesitation.. its annoying. one time it boosts through all gears.. you go around the corner it starts hopping around in 3rd. ARghh!!. as for the ecu it has some chip that took out the 180speed cut, and it once held 20psi on a rally car.. so i dunno about the head through the windscreen...not with my setup anyways.

[kunchris]

Thats a long list of symptoms and issues...

Just a few questions to start this diagnosis

- Engine management? Stock ECU? Piggy back? Have you been tuned?
- Gas used? Octane lvl?
- Have you checked your spark plugs?? Are they wet? Do they smell like fuel?
- Do you have a air/fuel guage? Digital like a AEM UEGO or Innovative LC-1? If so what are the readings?
- This may be a long shot but what are the engine codes from the OBDII system if there is one..

-Chuck
z4 ecu with some kind of chip. ecu was from a group N gc8 rally car. (version 2 STI)
i use v-power which should be 95-98 octane
havent checked the plugs yet. but they are a month old gaped to 0.6
my car is soooo OBD1..95..legacy so is the ecu. but there are no engine check lights.
(Note: that the car, when it works its perfect..powerful.. savagely fast..and not that bad on fuel too....its this annoying thing its stareted lately.

[chuckthefuk]

what about air fuel ratio gauge / stoichiometry readings?

How do you monitor if your boosting lean or rich?

[kunchris]

found the trouble to be shagged coils. the number 3 coil had a piece falling off it as i removed the rubber boot. oh well time for a GTB coil conversion

[chuckthefuk]

glad to hear ur making progress