Jump to content
SAU Community

Recommended Posts

Got my car on the dyno finally.. Made 227hp at 6000rpm.. but the problem is that after 6000 my power drops off quite steeply.. and by just over 7000rpm i'm only making 180hp.

Apparently i have a hefty flow restriction.. But my set up should be quite free flowing.. apexi pod, fmic, JJR split dump, Xforce cat, greddy cat-back ..

i think it might be my turbo itself.. bought a rb25 turbo off ebay and it's always been quite whirry.. Do you guys agree that this could be the issue?

Anyone selling a good condition, low km's rb25 turbo? (preferably a neo if possible) ... would this fix the issue?

Link to comment
https://www.sau.com.au/forums/topic/237215-flow-restriction/
Share on other sites

I'll put money on it being that Xforce cat.. the 3" "hiflow" xforce cat I got is sh~t.

I still have a similar flow restriction but that's because the turbo is too small for the motor.. goes from 245rwhp @ 5800rpm to 90rwhp by the time it hits the 6800rpm limiter :thumbsup:

i thought the X-Force cats were pretty good & free flowing! I hadn't heard any bad feedback about them until now.

From Wogans setup description, it is very similar to what i have (induction & flow wise).

Yeah well basically I got a sticker, grabbed one of those cats to go over the pits. It made a huge difference to response and topend that I took it out before the car went to the tuners.

Might not be an issue on stock motors at stock boost but on my 30, no good :thumbsup:

Edited by bubba

yeah car is tuned.. was a dyno tune yesterday..

it's not missing or anything.. definitely not coilpacks .. (why does that answer come up for every skyline related problem? haha)

only running 13.5 psi at the moment, but it's not losing any boost at the high end.. it's dead flat on 13.5 from 4000 to 7500

It doesn't sound like an intake or exhaust restriction to me. To me it sounds like something electronic related. Could be some sort of igntion issue, airflow meter (running outside of its resolution), faulty injector(s), faulty fuel pump or an ecu. I've got my money on it being a fuel pump, pretty common, replaced a few fuel pumps in my time. If the turbo is holding boost, then i doubt its a turbo problem.

definately a 25 turbo. replaced it myself.

well it's definately not a rb20 turbo .. could possibly by one from an rb30 or something i suppose... never throught about it that much.. but it's not really out of puff.. like i said it's maintaining boost all the way..

From what the guy at Hyperdrive was telling me, it's not so much the lack of boost, but it's the restriction on the exhaust flow. .. but i do agree that it's hard to understand how it could have restricted flow and also maintain boost.

I might try taking the zorst off and putting it back on the dyno before going out and buying a new turbo.

I have a restriction, 245rwhp down to 90rwhp over a 1000rpm span (5.8k to 6.8k) and boost climbs from 12psi to 14psi (in the higher gears) so I wouldn't exactly call yours a massive restriction :D

I was insinuating that it could be the turbo out of it's efficiency range, yes it's holding boost but airflow and temperature of air probably isn't optimal..

Edited by bubba
I have a restriction, 245rwhp down to 90rwhp over a 1000rpm span (5.8k to 6.8k) and boost climbs from 12psi to 14psi (in the higher gears) so I wouldn't exactly call yours a massive restriction :D

I was insinuating that it could be the turbo out of it's efficiency range, yes it's holding boost but airflow and temperature of air probably isn't optimal..

wow.. yeah i guess mine isn't too bad. It definitely is possible that the turbo simply can't hack 14psi at 7000rpm.

  • 3 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Just be warned that that turbo will not be a direct re-fit to the car. The exhaust housing is, of course, in the same place. It has to be - it's bolted to the exhaust manifold. So the dump will fit up. But the centre housing is not as long, so the comp housing will move backwards. This will affect both the turbo inlet and the outlet. There is fab work that needs to be done. Yes. it has one, it should have one. Paper gasket.
    • I only recently purchased the vehicle, it came with the flex setup but the current tune is e85 only, which is why im wanting to get the tune redone to enable a mixture.  First i need to get the exhaust redone tho. I was thinking of getting a varex muffler but it sems they dont fit well in the 33 (hang low because of the valve mechanism which sticks out on top) and generally dont sound good. So that leaves me with redoing the entire exhaust (more resonators and mufflers) so its not a menace when i come and go from home, and then have the aes dump valve somewhere along the line to really open it up. I was thinking of having it before the cat but after seeing how insanely loud it will be (on a vl turbo) im thinking of putting it more towards the rear of the car, after one of the resonators. 
    • At this point I'm just 'hoping' it's the turbo seals. I did speak to someone who said it's normal for these turbos to have a bit of axial play? Not gonna lie I've never checked a turbo for axial play before but you could hear it tapping a bit as I moved it back and forth. Surely that's too much? My theory is (could be completely wrong), bad axial play, worn bearings, bad seals, oil into dump/compressor side, burns in exhaust = blue smoke. On a timing belt related note, my crank pulley was missing that front plate that sits in front of the timing belt. It's that metal round plate. It did have the rear one, and the woodruff keys are in the crank which was nice. Can anyone confirm if the NEO det engine has a front plate, im sure it would to protect the front of the timing belt or something. Water pumps...the pump I got was an NPW (yes grill me if I should've got a genuine one lol). It has a smooth mating surface, kit came with a pretty pathetic looking paper gasket. Do I need to use any RTV or just trust the gasket will work because its a smooth mating surface? Cheers legends have a good Easter break!
    • Cheers man, I thought the same.   Bit of an update on it all. It was definitely blue smoke, not grey after all. It didn't really smell oily but it was blue after all. Also puffing just the smallest amount on idle with no throttle.   I ended up pulling the intake and exhaust off and there was around 3mm of axial play on the turbo shaft. So I figured we'll that's buggered and sent it off to get hi-flowed at hypergear. Haven't got it back yet.   I haven't compression tested it yet. Had a look in the cylinder and cylinder 1 spark plug, looked a bit sooty but not oily. Then I've just started doing my timing belt because it's age is unknown.
    • In that case it is probably stock. It lives in the navigator side footwell behind the plastic trim just in front of the a pillar.
×
×
  • Create New...