Boost Stuttering?

[Simmo]

Took the R out the other day for a play and occasionally at 1bar the R started to stutter on hard acceleration as if circulation or something was blocked, turned the boost down to 0.65 and all problems went away. Back up to 1 bar and no probs on that drive after that.

Took the R out again later on and exactly the same problem.

Anyone have any ideas?

 

[Gray]

You sure youre getting enough fuel?
Also check for any boost leaks....any smoke from the exhaust?

 

[stevepudney]

I get that on mid throttle at about 1.4 bar on my way up to 1.7 bar but if you nail it you can drive through it. Very strange and VERY annoying.

I thought mine might be due to cam timing being out and I was getting to much valve overlap which causes a little reversion but I have yet to inspect.

Simmo, I take it you have had your car tuned/maped to 1 bar recently?? and it was fine before the move to one bar, or is the fault a recent thing ??

Whats the rest of your spec, do you have a modded compressor inlet/filter ?? What turbo and cams you running ??

 

[Dooie Pop Pop]

plug gap to wide?

 

[mad max]

boost stuttering

spark being blown out it happend to me when i was running 1 bar +

 

[Simmo]

The car was mapped a while ago but recently had a hardpipe kit fitted for the intercooler. Before that it would occasionally blow pipes on the inlet side off, I originally put this down to cr$p hose clamps but could it be more sinister?

The current spec is:

- New SR20DET block (5k ago now)
- HKS forged 86mm pistons
- HKS vernier pulleys
- HKS 2.0mm head gasket
- HKS valve springs
- Kent 264 cams
- Ported, Gas flowed and polished head
- Ported and flowed exhaust manifold
- Lightened and balanced crank
- Shot peened rods
- MD214 turbo
- Forge fmic
- Bailey Evo dump valve
- Mongoose
- HKS Iridium plugs
- K&N filter
- Walbro fuel pump

- Standard Injectors
- Standard MAF
- Standard ECU

I have been planning to put it sard700 cc injectors, a z32 and an emanage but due to work, haven't got round to it yet.

What do you guys reckon?

 

[stevepudney]

I have the MD214 with the .86 AR turbine housing fitted to my car, I wonder if this is a symptom of this turbo ???

Could you describe the "stuttering" more accurately ??

Is it just a stuttering noise and sounds like wastegate or blow off valve noises or can you actually feel it through the car in some way.

On full boost can you feel the stuttering as "on, off" type surging in the boost.

When making the "stuttering" noise does the boost gauge flicker at all ??

You say a "hard pipe kit" was installed, did it happen before this kit was installed, did you change the compressor inlet pipe at all ??



.

 

[Simmo]

No blow off valve noises. The car physically stutters and you can feel it big time. it feels as if the boost is coming on a off violently. i stupidly didnt check the boost gauges to see what was happening there

It's only started doing it recently, didnt do it before I had the hardpipe kit put on. When the hoses used to come off before it was coming off hard boost rather than on acceleration.

Does this sound serious? :?

 

[stevepudney]

Sounds totally different to my little niggle then.

I would be checking for boost leaks.

I made up a little gadget with a gauge on it that I can use to pressurise my pipework so I can test it for leaks, but if your not in a position to make something up I would check & check again your pipework joints for a leak that only shows itself under 1 bar of pressure. remember it could be a vacuum leak as well so check all the little boost pipe to.

 

[Simmo]

Cheers Steve and Cheers the rest of you, I'll have a play around on Saturday and post back the results!

Thanks again for your help



Cheers, Simmo

 

[niklock1]

Mine is doing the same thing and i'm told that its a week spark being blown out.

 

[Simmo]

What can you do to sort out a weak spark?

 

[nismoboy]

What can you do to sort out a weak spark?

i have this problem also,

best thing to do is change these bits first

coil
ignition amp and also mount this away from the engine away from heat,
new ht leads
dizzy cap
rotor
arm

failing that re earth the maf

ive done all of the above and still have problems but im running 1.5bar+ so i guess im at the stage where i need an uprated ignition system of some sort.

 

[Dooie Pop Pop]

Lou was running 2 bar with no problems and mine peaked at 1.66 bar a few night ago. no problems :?

i still think your plug gap might be too wide, maybe the electrodes have worn?? i found my old ngk 8' s had worn down about .45 in 8000 miles :shock:

or could your dump valve could be leaking?

 

[Simmo]

Sound, cheers for the answers guys.

Gave it a good thrashing last night and had some initial stuttering, checked boost level at it was holding firm throughout the stuttering.

I filled up the tank completely and the stuttering stopped, so could it be fuel surging? I've got a walbro255 in there but I think its got the raised pickup rather than using the standard pickup.

Gonna check the plug gap today and go through the other diags suggested just in case as well.


Cheers, Simmo

 

[JIMMYBACK]

in thats case check the fuel pump hasnt come loose....how did you mount the fuel pump in the tank? why didnt you use the original fuel pick up :shock:

 

[Simmo]

Will do,

I didnt fit the walbro, it was on the car when I got it, was thinking of giving it a check over. If I dont have the std pickup, does anyone have one they would be willing to flog me?

 

[JIMMYBACK]

Will do,

I didnt fit the walbro, it was on the car when I got it, was thinking of giving it a check over. If I dont have the std pickup, does anyone have one they would be willing to flog me?

im jimmy i have everything :lol: :lol: if you need one i have one sitting in my old tank 8)

 

[Simmo]

Will do,

I didnt fit the walbro, it was on the car when I got it, was thinking of giving it a check over. If I dont have the std pickup, does anyone have one they would be willing to flog me?

im jimmy i have everything :lol: :lol: if you need one i have one sitting in my old tank 8)

Heh, I might take u up on that mate, in fact fck it yhpm