Engine Cuts Out For A Slit Sec/boost Issue

[pork hunt drifting]

since ive had the nisetune done ive had an issue a few times now.

very occasionaly when i give it a gut full my motor has just cut out quickly then goes on fine a split seond later. its just like the whack you get when u hit the speed limiter which im lead to believe is a fuel cut.

im thinkn its the fuel pump strugling or on its way.

the guy who done the tune said it done it to him once so loged it done a few more runs and couldnt get it to do it again. he also said that there wasnt a weird spike of air/fuel or sumthn like that so he wasnt thinkn fuel pump but wouldnt hurt to upgrade anyway.

also my boost is droping from 14 psi to 9 and we came to the conclusion its to do with the stock BOV. has anyone one else had a boost issue with em.

[kidafa]

Also interested in this as my car has done this.

[lilcrash]

It's over boost. Just disconnect your boost sensor if you intend on running that much boost all the time, it will do it more frequently in colder weather.

[wolverine]

The stock ecu mapping may cause this if the factory map/boost sensor (neo engines) reads 14psi unless it is modified within the Nistune software as far as I am aware. It may be worth asking the tuner about this.

Obviously coil packs are common causes of misfirign under load but your issue doesn't sound like this at all.

Alternatively it might be worth checking the AFM/wiring/plug for faults.

(edit: disconnect the boost sensor per lilcrash and block off the vaccum line)

[pork hunt drifting]

cheers for the info il drop into the tuners on way home tomoz and have a chat to him bout it and sort it out.

yeah definetly not a misfire and ive gone over the afm.

i might try blocking the stock BOV and see if that sorts the boost problem. if so ill probably just run 12 psi and see if it still makes 200kw

disconnect the boost sensor per lilcrash and block off the vaccum line ???????

[wolverine]

the boost sensor is at the back of the engine bay in the middle (above the cam covers) with a vacuum hose feeding it.

It won't be the BOV.

[lilcrash]

I don't know if anyone else had noticed but for future reference the boost curve is alot sharper when disconnecting the boost sensor, so much that it causes my exedy heavy duty clutch to slip. Exsessively, so also for future reference exedy heavy duty is only good for stock boost( the exedy rep told me it would be good for about 360kw )

Good luck at the tuners

[chef_stagea]

pork hunt...

how r ya mate

towards the back of the coil pack cover there is an orange and black round thing (just under the strut brace... its inline with a boost line going from the front sumwhere to the back of the engine bay

cut this hose... block it up with bolt and hose clamp

it will tell the ecu its not hitting any boost... therefor not letting it hit boost cut (15psi).... id guess its only at night/when its f**kn cold that its happening??

chef

all the info you need here http://www.skylinesaustralia.com/forums/By...mp;hl=boost+mod

Edited July 19, 2010 by chef_stagea

[pork hunt drifting]

sweet as cheers m8. il do it as soon as i can get it on the rollers and invest in a boost guage i think. i dont wana be pushn 14 15 psi on stock turbo for long. and yeah it makes sense that its been hapening more when its been fkn cold

[-Jimmy-]

I'm inclined to say it's the AFM playing up. There's a few methods of repair. Either simply spray carby cleaner (or similer) into the mesh, to clean the sensor. If this doesn't work some people say opening it up and re-soldering the joints works.

I did both of these to my AFM, neither worked. I replaced the AFM with another second hand one and then no more cutting out. My car's NA but it still sounds like the same problem.

Edited July 19, 2010 by -Jimmy-

[pork hunt drifting]

ok just cut and blocked the pipe runing to the boost cut thing and took the car for a quick drive. it has got rid of the problem but now the car comes on boost a bit later i think. its hard to tell i need to go for a decent drive were i can open it up propelly.

i really want to get a proper boost guage aswell the stock one is f**kn stupid!!

oah and so doesnt anyone think my stock bov is the problem for me loosing 5 psi of boost through the run?

i wonder if the wastegate needs lookt at the cars got 170k on it now?

2 months and i should be able to get my3076

i just want this bloody car to run right for once, but im not goin back to stock now!

[chef_stagea]

Stock bov will hold up to 13 14 psi... Look at a turbosmart kompact, looks good! Some have said it should hit boost quicker with the blocked hose, what are you using to control ur boost? This is most likely ur problem...

ok just cut and blocked the pipe runing to the boost cut thing and took the car for a quick drive. it has got rid of the problem but now the car comes on boost a bit later i think. its hard to tell i need to go for a decent drive were i can open it up propelly.

i really want to get a proper boost guage aswell the stock one is f**kn stupid!!

oah and so doesnt anyone think my stock bov is the problem for me loosing 5 psi of boost through the run?

i wonder if the wastegate needs lookt at the cars got 170k on it now?

2 months and i should be able to get my3076

i just want this bloody car to run right for once, but im not goin back to stock now!

[pork hunt drifting]

juat a cheap manual t valve that the guy who sold it to me swears by are good. but im gona have to try anotherone and see how it goes.

i dont think the boost came on as hard but hard to tell i dont wana thrash it without seeing how much psi im runnin

anyone got a cheap boost guage for sale?

[wolverine]

18psi on the stock BOV on my car.

[pixel8r]

when the AFM reads too high or the boost sensor reads too high (more likely the afm), the ecu will cut fuel for a split second. Basically it needs a better tune - if you have a piggyback ecu that bends the afm signal, then it is not bending it enough and still hitting the upper limit set by the ecu. it cuts fuel to protect the engine in case the engine is getting more air than the afm can reliably read.

shouldn't be necessary to disconnect the boost sensor - just tune the afm signal better (on a dyno).

[Tangles]

18psi on the stock BOV on my car.

yup... same. compressed the tophat a little to make the spring slightly 'stronger'

I wired in a FCD (fuel cut defender) to fix this exact issue on my stag.

Comes down to more tuning required.

The FCD allows you to 'cheat' a little with the tune, although if it pings with the FCD there arnt any safeguards left to hold her back a little, so be warned!

[kidafa]

ehhh shit tune... boost works FTL. Did it the first time the day I picked it up from them when they tuned it called them about it and said it behaved fine for them.

Turbo tune it is from now on..

[chef_stagea]

It's hitting boost cut tho!! If you block the pipe off ull b right, now u need to c what psi ur running, stock turbo = 12psi safe, bov isn't super legit over 14... If it fails ull do a turbo no questions!! Afm can't read over 14 or so psi... See what your running and go from there. But I think it's time to go manual boost control!!!

when the AFM reads too high or the boost sensor reads too high (more likely the afm), the ecu will cut fuel for a split second. Basically it needs a better tune - if you have a piggyback ecu that bends the afm signal, then it is not bending it enough and still hitting the upper limit set by the ecu. it cuts fuel to protect the engine in case the engine is getting more air than the afm can reliably read.

shouldn't be necessary to disconnect the boost sensor - just tune the afm signal better (on a dyno).

[wolverine]

the factory BOV will not lead to turbo failure

[QWK32]

if you have nistune you can disable the stock boost sensors limits in the tune. while others have said the stock BOV will be up to the job, in my case it started failing at 14psi, it was clear that it was the BOV opening as i could here the whoosh as it released and watched my boost drop rapidly.