No Pwer Past 6000rpm Rb20det

[black sky]

Hi peoples

Now this is really f&*$^*n pissing me off. I’ve got an rb20det in a 180sx. I can drive the car fine makes boost well and then bam at 6000rpm I loose all boost as in it’s running 0 psi. At first I thought it was my wastegate cause I bought a cheap imitation off the net, but then I changed that to a genuine Tial wastegate and still the same. For the love of god guys I got spanked by an xr6 he handed me my own arse and all I could do was hang my head in shame!!!! What could possibly causing this huge lose in power. Well the cars got all the normal GFB like fuel pump, injectors, AVCR, ECU, fmin, zorst, but where it might be getting let down is the turbo, ive got one of those cheap ebay copy xs-power turbos, I got it balanced when I baught It and all, could that be the problem?? Please help, please. I don’t care how stupid it may sound tell me what you think it could be.

Waiting in anticipation

Anthony

[chaos]

when does your boost cut out normally? before it started at 6000

[black sky]

when does your boost cut out normally? before it started at 6000

<{POST_SNAPBACK}>

It would go right up to redline no problem. the bastard used to fishtale into second and step out going into third now nothing. The rev limit is set up at 7800rpm and it would hold boost the whole time thats on standard 8psi setting a on 14psi and setting b on 18psi.

now goes up to 8psi then at around 6000rpm (probably colser to 5500rpm) just falls flat on it's face

Cheers

anthony

[blind_elk]

What were you doing when all this happened? Even crap turbos wouldn't just suddenly dump all boost.

[black sky]

What were you doing when all this happened? Even crap turbos wouldn't just suddenly dump all boost.

<{POST_SNAPBACK}>

Dunno one day power next no power.

i thought it's cause it took it drifting but even after takin it driftin it was fine then a couple of weeks later it all fell to shit.

Cheers

anthony

[paulr33]

your going to need to go into more detail if you want us to debug it over the forums. failing that maybe take it a to a real machanic and take them for a drive in it or get them drive, sometimes its much easier.

so you drive along boost is normal rising until it hits target boost and then at 6000rpm it goes from say 12psi to 0psi and you have no boost at all? is that correct? does this happen every time or once every now and then? does it happen over and over on the same drive / test run or is it just when it feels like. when it does work "ok" does it stay at 12psi and keep that until redline ok?

do you have any pops, noises, bangs, kabooms, smoke, whines?

are you seeing any oil around the intake components, bov seal, cooler piping areas, throttlebody join up pipe?

what boost controller and wastegate pressure spring are you using

when did it last work "ok"? whats changed since then?

[paulr33]

nevermind just read avcr, what does it display when the problem happens?

when you MONITOR and choose BOOST and do graph mode does it actually show the manifold pressure taper off to 0psi past 6000rpm or are you just exaggreating it?

have u tried bypassing the avcr and running direct of the actuator (int gate) or the external gate spring only. does the same problem when you do this? if so that would rule out the avcr being stupid

[paulr33]

what clutch and what ecu

[black sky]

nevermind just read avcr, what does it display when the problem happens?

when you MONITOR and choose BOOST and do graph mode does it actually show the manifold pressure taper off to 0psi past 6000rpm or are you just exaggreating it?

have u tried bypassing the avcr and running direct of the actuator (int gate) or the external gate spring only. does the same problem when you do this? if so that would rule out the avcr being stupid

<{POST_SNAPBACK}>

I took it to my tuner he took it for a drive and said it seems to be the waste gate cause it looks like it's just stayin open past 6000rpm (really bout 5500rpm) and that's why it' not makin any boost. so i then baught a new tial wastegate and put it on today and it's the same problem.

And i kid you not it says o psi on my boost gauge and the car seems to be goin backwards.

No strange noises nothin just 0 boost, it has me baffled. i just ran it on standard boost which is .8 bar and it goes up to 9psi and holds that to bout 6000rpm and then back down to 0.

i really really really wanna get this fixed it's just pissin me off now!!!!!!!!!!!

Thanks for the replys guys

Anthony

[black sky]

Sorry

got a brass button clutch and a microtec ltx12

Cheers

anthony

[paulr33]

by new wastegate do you mean new external wastegate or new actuator? sounds like new external wastegate. what size is it (out of curiosity).

[black sky]

by new wastegate do you mean new external wastegate or new actuator? sounds like new external wastegate. what size is it (out of curiosity).

<{POST_SNAPBACK}>

It's a tial 38mm external gate

[paulr33]

odd problem to have. i got no idea. even if the spring was shagged you would still make some boost one would assume? have you checked cooler piping areas for leaks and/or signs of it coming loose? sounds like one of those could be leaking under pressure. is it always poast 6000rpm?

[black sky]

odd problem to have. i got no idea.  even if the spring was shagged you would still make some boost one would assume? have you checked cooler piping areas for leaks and/or signs of it coming loose? sounds like one of those could be leaking under pressure. is it always poast 6000rpm?

<{POST_SNAPBACK}>

Yea always past 6000rpm like i said like a light switch it just goes down to 0 PSI

it doesn't seem to be leaking boost prior to that throughout the rev range.

Cheers

anthony

[BHDave]

Can you hear the turbo spin up? And does it sound like it stops when the boost drops to nothing or is it still spining?

Dyno is your friend, get it on and have a listen/look to see whats happening in a controlled environment. If you have a leak it'll be easy to find if it's big enough to bleed off all boost. If your turbo is suddenly seizing you will hear it.

Edited November 9, 2005 by BHDave

[black sky]

Can you hear the turbo spin up? And does it sound like it stops when the boost drops to nothing or is it still spining?

Dyno is your friend, get it on and have a listen/look to see whats happening in a controlled environment. If you have a leak it'll be easy to find if it's big enough to bleed off all boost. If your turbo is suddenly seizing you will hear it.

<{POST_SNAPBACK}>

It does'nt sound like the turbos seizing, and i cant really see any leaks

Cheers

anthony

[xRHETTx]

Im going to have a stab..

Sounds like your wastegate is opening when the max boost is reached and then staying open?

Have you re tuned the avcr since you changed wastegates? Maybe do that. Or maybe they have plumbed it up wrong?

[black sky]

Im going to have a stab..

Sounds like your wastegate is opening when the max boost is reached and then staying open?

Have you re tuned the avcr since you changed wastegates? Maybe do that. Or maybe they have plumbed it up wrong?

<{POST_SNAPBACK}>

Thats an idea but it was workin fine before with the exact same setup and now it's not.

do you think i should still check it??

Cheers

anthony

[xRHETTx]

But you havent tuned the AVCR with the Tial wastegate?

I am pretty sure it will have to be retuned to suit the differences between the wastegates.

[black sky]

Well guys

I took the car to hitman and he didn't even put it on the dyno like i wanted him to he just took it for a drive cheked the BOV and he said check the cat it could be blocked, but how the f*^&k could the cat being blocked make 0 psi boost????

The car is not running on 0 psi like i thought ( by the way the boost cutting out is happening at 5200rpm and in higher gears it's less) it's actually running vacume

So much for the Dyno

Cheers

anthony