Flat Spot

[shmiddy]

i have a r33 with some basic mods pod, fmic, t3/t4 hiflow turbo, 3'' turbo back ex, safc, hks cam gears.. and before i took it in to get the safc and cam gears fited and tuned (also an intercooler pipe leak fixed) the car ran smooth all the way through the rev range, now ocasionly i have noticed towards the top end of the revs when nailing it, i get a flat spot (feels & sounds like when the revlimiter is activated) but its coming on sooner then reline, i was thinking maybe because i have stock fuel pump and injecters that with the tuning the car got it's struggling to suply the fuel at times at the top end when its reall goin hard.. any help would be apresh

[JaFF]

get full engine management- powerfc should fix it.

[R31Nismoid]

as you said, stock fuel pump... i'd begin there

[djr81]

i have a r33 with some basic mods pod, fmic, t3/t4 hiflow turbo, 3'' turbo back ex, safc, hks cam gears.. and before i took it in to get the safc and cam gears fited and tuned (also an intercooler pipe leak fixed) the car ran smooth all the way through the rev range, now ocasionly i have noticed towards the top end of the revs when nailing it, i get a flat spot (feels & sounds like when the revlimiter is activated) but its coming on sooner then reline,  i was thinking maybe because i have stock fuel pump and injecters that with the tuning the car got it's struggling to suply the fuel at times at the top end when its reall goin hard.. any help would be apresh

<{POST_SNAPBACK}>

Be careful bloke. One of the quickest ways of killing an engine is to run it lean at full noise. If you think this is the problem get it to a dyno & check the AFR. Should be in the 11 to 12:1 range. Any more than this & you can easily kill your motor.

[shmiddy]

Be careful bloke.  One of the quickest ways of killing an engine is to run it lean at full noise.  If you think this is the problem get it to a dyno & check the AFR.  Should be in the 11 to 12:1 range.  Any more than this & you can easily kill your motor.

<{POST_SNAPBACK}>

yeah i only just got it tuned on the dyno, im gettin a wolf ecu within the next week or so, but i might up the fuel pump be i put that in to ensure im not starving it of fuel. will the stock injectors need replacing what hp are they good up to..

[djr81]

yeah i only just got it tuned on the dyno, im gettin a wolf ecu within the next week or so, but i might up the fuel pump be i put that in to ensure im not starving it of fuel. will the stock injectors need replacing what hp are they good up to..

<{POST_SNAPBACK}>

IF you have the dyno sheet it should have the AFR graphed. This will tell you if it is a problem or not.

Not sure what the max hp on stock injectors is. Best not to run them at 100% anyway. If needed you can either go to a larger injector (still on standard pump) or run a bigger pump at higher pressure (ie new pump & regulator) or if you want to go the whole hog all three.

[Andi]

You're fuel pump is on its way out mate. Get it replaced asap, shouldn't have to say how bad it is not to have any fuel going into your engine.

Re: Injectors, it depends on how your injectors are. See if you can borrow a consult or find some other way of seeing what duty cycle they're running. Ideally 85-90% is what you'd like to run although 100% is fine too - theres just no chance of adding more fuel if your car needed it.

[shmiddy]

has anyone els had this problem?or does this sound familure to anyone, just wana get to the bottom of it, sure im gettin a new fuel pump (bosch 040) in 2 weeks then the wolf put in and tuned all up again.. but i just wana hear if this sounds familur to anyone

also new injectors can wait a few months so will all i need is a pump or do i need a regulator aswell? can someone explain it all, thanks again guys

[paulr33]

gtr 33 pump and powerfc instead of bosch pump and wolf

[shmiddy]

gtr 33 pump and powerfc instead of bosch pump and wolf

<{POST_SNAPBACK}>

why?

i know people with the wolf who have no trobles and im gona take it to a guy whos renound for tuning them, any spesific reason??

[paulr33]

map sensor or aiflow meter?

[shmiddy]

man i know as much on cars as i do about understanding women so ya will have to explain it a bit better mate

[paulr33]

map sensor replaces the stock air flow meter and uses guesswork to work out how much air is coming into the system. airflow meter measures all the air coming into the system via its hotwire setup.

lots of people believe its a restriction but it wont be. its harder to tune with a map sensor and it wont be anywhere near as accurate or good compared to an airflow meter setup. do you have rb20 or 25?

[shmiddy]

i got a rb25... i am goin with the wolf though as i got a good price and my tuner i take it to told me to go the wolf, and i heard nothin but really good coments about the tuner the ocasional cold start problem but can be sorted out easy enought, really more worries about this flat spot and fixing it