Loosing Power

[StealthX]

Hey guys, long story short, my x-trail is/was making a little over 210awhp on 10ish psi from a VG30 turbo.

The turbo is very much on the way out, its got a fair bit of shaft play, blows oil smoke etc...

Over the last month or so, the situation has been getting progressively worse, on the initial tune, the car made 212whp, now 2 weeks ago it made 187.5whp.

I'd imagine Its a bit less than that now too... I'm quite aware that the turbo is nearing the end of its life, so much so I've already ordered a GT2860rs to go on soon...

I still see the same amount of boost, but it feels a little laggier than before, the response doesn't feel as 'sharp'

The motor has 130k kms and is very healthy, did a big coolant and oil change last week and had no coolant with oil or vice versa, havnt had chance to do a comp. test but im pretty sure the motor is in great order, it starts and drives perfect, doesn't pop or miss on boost, exhaust sounds the same as ever, fuel economy is still good, never overheats, stalls, makes rattling noises, backfires etc...

My question, is the loosing power part of a normal turbo-at-the-end-of-its-life situation?

My obvious thoughts (other than the bad turbo) are either fouled plugs, or blocked cat (even though its only about 8k kms old...)

What do you guys think? Is my loss of power directly due to my turbo on its way out?

Thanks!

[scotty nm35]

Its always fun dropping the exhaust and going for a squirt, the oil could have gummed up the cat I guess. Other than that, a compression test?

[geraus]

did you check your spark plugs? see if all cylinders are firing? coil packs? etc?

[Gareth87]

i would have thought the turbo is a likely cause. If the turbo is worn to the point where the blades are touching the housing, i would surely think this would reduce power. Personally, i would say that if the turbo is stuffed, then replace it like were going to anyway and get it back on the dyno. You will very quickly know if it was the turbo causing your issue.

[hypergear]

Well if the turbo is not sized, rubbing its fins on housings or've lost parts of its wheels then it will make absolute none difference doesn't matter how old it is.

But if its leaking oil then it might shoot some to the engine and cause power issues.

[StealthX]

did you check your spark plugs? see if all cylinders are firing? coil packs? etc?

all cyls are def firing, i'd notice if one wasnt, its only a 4 banger after all! haha

If the turbo is worn to the point where the blades are touching the housing

the compressor blades seem nice and fresh but i cant see the turbine with out dropping the dump, with i cant be fvcked doing since it'll happen with the new turbo anyway... but yeah the shaft play is such that this could be happening!

Well if the turbo is not sized, rubbing its fins on housings or've lost parts of its wheels then it will make absolute none difference doesn't matter how old it is.

huh? are you saying rubbing fins etc WONT have an affect??

[hypergear]

Like if its rubbing fins, with broken wheels and etc it will affect. Unless that it will be pumping exact amount of air as if it was new. I think it should be expressed as:

Well if the turbo is: not sized, rubbing its fins on housings, or've lost parts of its wheels, then it will make absolute none difference doesn't matter how old it is.

Punctuations makes lots of differences

[Walk510]

you need to run twin air filters just like rh9 ?

[StealthX]

you need to run twin air filters just like rh9 ?

bahahaha thanks mate! golden!

[StealthX]

Hey guys, an interesting read...

I dug up two dyno graphs Andrew gave me from the tuning. the 202hp one was from the original tune, and the 187hp one was from about 4 weeks ago.

Both runs were on hot days, with pretty much every other variable under control (engine temp, boost etc...)

the only thing that was changed was the tune (slightly), Andrew said it was cruising a bit lean so he put some extra fuel in, and just did some more fine tuning - nothing too drastic at all - more importantly no ignition timing changes.

Have a close look at the boost curve...

The wastegate actuator is roughly a 6psi item - its the stock VG30ET one - which should make 7psi on a 300zx. The boost rises to 11 at redline because the wasetgate design of this turbo is shithouse, and it cant flow enough gas to keep the boost down, I don't care however cos its still safe and under control and its tuned for said boost level.

What's interesting is I see 'full' boost of 5psi some 200rpm LATER in the most recent graph. I.E. its laggier. And also, look at where i reach 11psi on the first graph, then on the second. There's 500rpm difference, on the first graph I see 11 @ 5000rpm, then the second I see 11 @ 5500rpm!!

bring on the disco potato!

cos this one is farked!

Edited March 22, 2010 by turbo x-trail