Flat spot

[Munna]

When accelerating in second gear form 60 to 100 sometimes theres a slight flat spot at the 80Km mark.

I have a 93 R33 manual Exhaust blow off valve.

I thought this may becauce of the exhaust and/or blow off valve

but I noticed this on another skyline I test drove a dead stock 95 r33 man.

I have only owned the car a couple of months and I am new to turbo cars. Is this normal? or do I have a fault?

[predator]

Probably just the way the stock fuel maps are setup in the ECU - if you wish to reduce it you will need a method by which you can adjust the air/fuel mixtures at particular revs... most use a S-AFC, piggy back ECU, or aftermarket ECU to do this. Hope that helps..

[Munna]

Thanks predator,

Heard many good things about SAFC sounds like the go boost controller and cold air intake will be first though

[G0DF4Th3R]

before you go out and buy an SAFC, check your AFM to make sure it isnt faulty or dirty. if possible try to swap AFMs with a friend and go for a drive to see if it makes a difference

[JimX]

If you get a boost controller you will probably need some sort of fuel cut defender or you will get an even bigger flat spot. Do any electronic boost controllers have these? My Profec B doesn't, the car came with a HKS fuel cut defender as well and it works perfectly.

[Guest Robo's]

Mines got a bit of a flat spot too, sort of surges abit, its running way too rich as it backfires sometimes too. But sometimes it will pull all the way, but when it gets warmer (motor, airflow) it gets more consistant. First im going to try a cold air intake, as when i pop the bonnet and put my hand over the pod, it is very hot.

[Jay95R33]

Yepp - this is very typical from the R33's.

You should see my dyno run !! Big dip in power when the ECU pulls timing and dumps fuel at about 4-5000 rpm

The S-AFC will help. It fools the ECU and shows the ECU a reduced air flow rate, therefore the ECU doesn't pull as much timing blah blah blah.

J

[Guest Robo's]

Sounds exactly right, sometimes it pulls then sometimes it surges. I think its loading to much fuel and it can't burn it, thats why everyone closes the gap on the spark plugs to try and eliminate it.

[rb20-calais]

happened with my rb20 as well

Evan

[OVL-747]

has happened with my rb30 as well hehehe

what it sounds like is mainly ur afm

im not too sure about the right setting for a rb25 , but with a rb30 , the air flow meter , needs to read a set ohmage of 382ohms , this measurement is taken from the 2 outer most pins on the afm , where the loom plug connects to it.

if its out it dummys info to the computer which is not correct and makes it run rich/lean etc , causes flatspots and hesitation etc etc etc.

also things like malpassi rising rate regulators can do it too , as boost hits , the fuel pressure rate rises at whatever rate the reg is (1.5:1) etc and that sudden fuel dump doesnt immediately get burnt , bit of a dull spot.

[Munna]

Robo's Yours sounds exactly the same as mine.

Have you tried a smaller gap on your plugs yet?

Unfortunatly I live out in the country and I am the only one in town with a r33 gtst so I cant swap the air flow meter with someone.

Anyone else had this problem and solved it (cant afford SAFC).

[adam 32]

how big is this flat spot?

i had a flat spot around 4K on my car and turned out to be a fried coil. dont assume an AFC will magically fix this problem as many cars are rolling around without AFCs and without flatspots!

[Munna]

Adam 32 the flatspot is not very big although it varys slight surge at 80 Ks than starts accelerating normally.

This mainly only happens in 2nd gear though. Power in all other gears is consistant right up to 7000 rpm

[WazR32GTSt]

Originally posted by OVL-747

ohmage of 382ohms

just for reference: ohms are a measure of resistance.

use the right words and ppl will realise you do know what you are talking about...

sorry for the irrelevance to the thread...

[OVL-747]

well i am ever so sorry for my un-educated reply , i will try harder next time....................

[WazR32GTSt]

relax OVL-747, it wasn't meant to be harsh.

btw...

i don't have a flat spot.

the AFM sounds like it could be a source of the problem from what i've read. have you chacked your base timing?

[OVL-747]

wazza

its cool dude

[Munna]

What does a R33 AFM cost is mine is stuffed