Boost cut/surging etc

[hitnrun]

Hey guys,

I know that a lot of people have asked this question, but I am still not sure on a couple of things.

When accelerating in any gear, if my right foot is flat it surges/misses (whatever you want to call it) at 4500rpm and agin at around 5000rpm. I have an aftermarket Boost guage, at most rpm it reads ~7psi, when the surging happens (or just before) it reads ~9psi. I can't always get it to hit 9psi only under very heavy load. It then drops down to 0psi and back up again.

Now before everyone says my boost is wound up too high, and that it is hitting the boost limiter/cut - the car is 100% stock. Zorst, i/c, ecu, no BOV and I most definitely haven't change the boost. I have check the engine bay and I can't find a bleed valve or anything out of the ordinary, so I am assuming that it shouldn't be hitting a boost cut.

Someone here mention that it could be spark plugs, I haven't checked them yet.

So does anyone have any ideas on what to do about it. I did think that it might be a crack or something like that in the I/C or piping, but I don't really know. If it is, how do I check it? Where should I be taking boost measurements from

As for the boost cut, the car doesn't perform anywhere near what I would expect it to if it was hitting the limiter. A mates Skyline with a turbosmart DSBC has had his wound up to ~12psi with no worries. Goes a frigging hell of a lot harder (admittable he has an exhaust etc, but still).

In summary is anyone able to give me a run down/checklist of things to do.

Off topic, but who in the Sunny Coast/Brissy area would mind giving me a hand/pointers/demo with the fine art of drift. I know sort of what to do, but until you really experience firsthand it is hard (for me) to put it all together.

Anyway thanks in advance.

Cheers,

Tim

[BoOsTeD_RB26]

Tim,

I had a similar problem after my car was modified. Under load, at around 4000rpm-5500rpm she'd surge and carry on....after that band of the rev range....she'd pick up again (slowly) and keep going.

I too thought it was my "brand new" spark plugs aswell but in actual fact it was the air flow meters that were buggered.

Your best bet would be to take it to a workshop and have this checked.

After I had some new air flow meters installed......everything was fine

Hope This Helps

[hitnrun]

If you don't mind me asking, what did you get modified, was that what cause the surging, or was it simply conicidence.

If it is simply the airflow, would it be possible to grab a second hand one from a wrecker. Can anyone confirm this. On a side note I have removed the a/f and cleaned/sprayed it with contact cleaner, but didn't seem to help.

One thing I forgot to mention before was that if it doesn't always happen. On a few occasions it has not surged and has accelerated nicely up to 7000rpm. Sometimes it only surges lightly. I have also noticed that it MIGHT be worse in cold air/at night. Hmmm.

Also when I have whacked in a few hundred bottles of octane boost in the one tank it doesn't seems to happen/be as bad. Not sure though as I have tested this thoroughly yet.

It it timing possibly?

Tim

[GTS-4OrCeD]

I had the exact same problem with mine. It was caused by massive excess fueling. I had my spakeplugs cleaned and regapped (something may have been done to the Air fuel mixture) and just like magic my car made an extra 20 hp.

Greg.

[BoOsTeD_RB26]

At that particular time i had bigger dumps fitted.....K&N pod filters and a boost to 16psi. But before then i had a bigger zorst...and all the other sh!t.

When the problem occured....i took the car back to the workshop and they just replaced the air flow meters....free of charge.

Although they said they were gonna try and fix em......so next time i go back...they should be waiting for me.

Hope this helps

[hitnrun]

Thanks for the replies guys.

At this stage I think I will check/clean/replace my spark plugs first, and then try swappping in a mates a/f metre and see if that does the trick.

With regards to over fuelling, definitely seems to be a possibility, Also makes sense why a stock skyline can only get 200km out of a tank on 98ron and octane boost.

I will investigate a bit further tomorrow and see what happens. If it's no go I think I'll buy a hardcore 180sx and.... nah, not a chance

[DAMQIK GTS-T]

Dosnt matter what boost im running

and it only started after I de-greaesed the motor.

I have so far sprayed all plugs and conectors with contact cleaner

chacked all the ign coils blocked off the factory boost sensor

re timed the motor checked the cam timing reset the ecu

non of these things have fixed the prob BTW my spark plugs are near new.

anybody with any other suggestions for things to check?

is there a test for the AFM?

Tim if you hold your foot flat dose the motor rev past the problem?

[hitnrun]

Yeah if I hold my foot flat it enventually gets to like 5800-6000rpm or so and then it is fine until the limiter.

I have been putting in 2 bottles of nulon octane booster every tank and after about 3 tanks it is now drastically better. It still surges but a lot gentler. Damn expensive, but better.

One thing we could try would be swapping a/f metres and seeing what that does.

Tim

[DAMQIK GTS-T]

yeah we could try

never know it might fix both our cars.

when ever ya ready

DAMQIK

[hitnrun]

I'll pop around tomorrow after work.

prolly about 3pm-ish

[BoOsTeD_RB26]

hope all goes well

lemme know how it goes

[Doctor]

I think it is caused by you putting 2 bottles of octane booster every yank. Excessive octane booster can stuff your plugs. Take them out and if they are white that is the problem.

Doc

[hitnrun]

Hi Doc,

I have only recently started putting octane booster in, and that has helped immensely.

DAMQIK is currently checking all his electric as he feels thats where the problems lies in his car. If it is we will give it a go on mine.

Cheers,

Tim

PS I do realise that I should bite the bullet and buy new plgus anyway, but at the moment they are all AOK, so I'm hoping I can hold off buying them for a few months