Diagnosis Help!

[nisskid]

Ok, im pretty sick of this shit, i've been dealing with this loss of power for a while, the cars a track car, drift specifically.

Engine:

RB20DET

RB25 Turbo

Pnumatic Boost Controller

Pod Filter

Front-Mounted Intercooler

3" Split dump pipe with screamer

Bosch 040

Nistune Remapped ECU

Power when it was first remapped (probably 3 years ago) was 180rwkw, hasn't been dyno'd since, but there is a noticeable loss of power, bogs down a lot easier, it's laggier, and generally slower on the straights. it cuts out around corners when i go in hard some times, i think this is fuel surge from the fuel slushing around, and probably completely unrelated.

Symptoms:

- White smoke, smells like burning oil but not overly blue, could be burning water as well. Has been smoking for a while on start up, but went after some driving, now smokes all the time, although seems to reduce after it's been on the track for a bit

- Low power, no missing or anything, runs smooth, just lacks power

- Laggy

Extra details:

- Still seems to hold boost ok, possibly spools a bit late

- The screamer which is pretty good (split dump on internal wastegate), known for how good they seal, and definitely sealed back when i had it on the street, now has exhaust coming out on idle and under light load, well before the wastegate should be opening. unsure whether the screamer just isnt sealing properly anymore, or whether the wastegate is opening early

- I just replaced the exhaust manifold gasket + faced the manifold + replaced studs (they were f**ked, 2 were missing), also the turbo/manifold gasket was replaced.

- Actuator has been adjusted to make sure the gate arm is as far back as it goes at rest

- Runs smooth, no missing, sounds great

- Quite loud tappets, been loud for a while, haven't bothered with them

- Looks like it's gone through a little bit of coolant (radiator was low when i just checked it), but can't be 100%

- Small amount of bubbles in radiator

Compression test:

120 - 135 - 120 - 130 - 120 - 120 (Cold Dry)

170 - 150 - 150 - 150 - 150 - 170 (Cold Wet)

140 - 140 - 145 - 145 - 140 - 140 (Hot Dry)

170 - 165 - 170 - 170 - 170 - 180 (Hot Wet)

at this stage, im thinking the turbo is going, but i'd just expect to see it struggling to hold the 12psi it's set to.

that's it off the top of my head, but as i remember more i'll add details.

[Simon-S14]

do a leak down test... that will tell you more then anything.

to be honest it sounds like from what you are saying that the motor is just tired..

[dark.sky]

do a leak down test... that will tell you more then anything.

to be honest it sounds like from what you are saying that the motor is just tired..

+1

Sounds alot like my old RB20.

Was tired, just turfed it out.

I had a slight oil slick in the radiator and reserve bottle aswell.

[DVS JEZ]

Time for another motor man.

[MBS206]

Looks like a pretty tired motor from the results.

[Simon-S14]

btw bubbles in the radiator (that are always there) is a sure sign that something is up

[nisskid]

do a leak down test... that will tell you more then anything.

to be honest it sounds like from what you are saying that the motor is just tired..

pretty much my thinking after last night, but the compression test was slightly promising as after a quick search it didnt look like that was a too bad result, maybe im wrong?

and the bubbles in the rad are pretty slight, headgasket could be buggered.

just not sure what to check to confirm it, to give you an idea simon, this is the difference between me making winton or not, so if i just write off the engine as old and f**ked, then im out, but if i can find an issue and fix it, then im there.

leak down is next on the list, unfortunately dont have one myself, only comp tester.

[Simon-S14]

ive seen engines with major internal damage comp test ok... i remember trent saying on here he comp tested a car that had a chunk missing from the crown of the piston comp test ok.. the point is its not the most accurate indication of posblems. leak down test is however.

if its HG. i'd say rip the head off... ddo a quick head shave. check the manifold gaskets while your at it. check the turbo and wastegate. and put another OEM gasket on and put it back together

[nisskid]

yep, do you have a leak down test kit simon?

[Simon-S14]

i do at work yeah. could borrow it if you want. or come round and help you with it? only prob is finding the time lol

[DVS JEZ]

Try re torqueing the head down to help the head gasket. Put in some chemi weld or similar,

Make sure u run enough fuel so it doesnt surge around corners.

Go to winton with a little bit more boost and enjoy the day and get a new motor after u finish.

[nisskid]

ok, thanks to simon, was leak tested yesterday, got between 5-20% across all 6cyls.

pulled off the dump, still burning oil, but i noticed it did take a few minutes before it really started to smoke, which really made me think it was a leak that was burning from touching a hot surface in the exhaust at some stage once it heated up from running for a few minutes.

anyway looked at the exhaust housing, not much shaft play, blades look alright, wastegate seems to be sealing.

took the turbo off the manifold and ran it straight out the manifold for a bit, couldnt see any white smoke anymore.

so i can only conclude the oil is coming from the turbo.

the question is, if it's spooling up and building full boost still, can it still be affecting power? i didnt think so. even if it is leaking oil, does that mean that it's definitely the source of the low power?

im thinking of grabbing another turbo, putting it on, then taking it for a power run on monday, check the tune etc etc.

one thing i did do at the same time was disconnect the rocker cover breathers so that they didnt go back to the intake and just vented to the atmosphere, there was quite a decent amount of pressure built up after blocking the breathers off with my thumb for about 15 seconds. not sure if that's an issue though.

[DVS JEZ]

Thats blow-by. What turbo are u going to put on?

[Trozzle]

yeah blowby on that last note of yours

[nisskid]

lol i know it's blow by, i just wasnt sure how much is considered normal. there is a lot of oil pooling in the in take and i want to get an idea if it's just bad blowby or whether it's oil getting into the compressor housing via f**ked seals.

stock Rb20 turbo going back on, currently running rb25 turbo.

[MrStabby]

I always assumed that fuel surge would probably damage a motor - with lean outs and power cutting in and out... a quick search turned up these threads below that seem to support that idea. Might be worth doing something about it before the next motor goes in. At the very least it will mean you always have power in corners.

http://www.skylinesaustralia.com/forums/topic/188138-fuel-surge/page__p__3394937

http://www.skylinesaustralia.com/forums/topic/316605-help-please-no-1-cylinder-low-compression-and-turbo-failure/page__view__findpost__p__5181420

[nisskid]

yeh it's definitely not a good thing, but it's an RB20 so it's not top priority atm, but it's the kind of thing i should be able to fix by running a full tank of fuel. it's the constant power loss while the engines running smooth that's getting me.

[smithy85]

lol i know it's blow by, i just wasnt sure how much is considered normal. there is a lot of oil pooling in the in take and i want to get an idea if it's just bad blowby or whether it's oil getting into the compressor housing via f**ked seals.

stock Rb20 turbo going back on, currently running rb25 turbo.

Keep in mind: Excessive blow-by can cause a positive pressure in the crankcase which can, in turn, lead to seals leaking due to the excessive pressure felt at the seal. This doesn't necessarily mean perished seals.

[nisskid]

Keep in mind: Excessive blow-by can cause a positive pressure in the crankcase which can, in turn, lead to seals leaking due to the excessive pressure felt at the seal. This doesn't necessarily mean perished seals.

yeh that was my main concern with the amount of blow by i was feeling, i have had the dipstick blow out once or twice, but certainly not a regular occurrence.

as mentioned the leak down test has shown pretty positive results. so at this point im really not sure.

going to chuck a oil cooler on, thinking the oil overheating could be causing some of the results ive been getting, as a minimum it's needed anyway.