Turbo Busted?

[Mr_G]

Hey guys,

Havent posted here in a while but ive been struck with abit of a query. I have an S15 which has a T28 BB Turbo standard.

Now i went to a dyno day and also went to get the car dyno tuned with a pfc.

The tuner said that it wasnt making enough top end power, being short 10-15rwkw with most s15's hes tuned with the same mods. So he is puzzled as to why and so am i! He said car was running healthy too, so it didnt show signs of cylinders gone etc, however I havent done a compression test. Mind you, he is a popular tuner in sydney, and has tuned my old R33 when I had that and had no dramas.

Here were some of the things he noticed while it was on the dyno:

1) When winding the boost up, it really didnt yield any more power. I have 2 boost controllers to try out and both of them showed no extra response on the dyno

2) The Intercooler piping going to the turbo was coated in oil

So are these signs that the turbo has gone bye bye or is about to go? If not, what can cause lower figures in terms of motor problems?

Im very puzzled and just trying to work this out. Any help or input would be appreciated. I dont have the dyno graph either cause I dont pick up the car till friday. Car has all the supporting mods to at least reach 190 - 200rwkw and the car only pushed 180rwkw

Edited September 8, 2006 by Mr_G

[Mr_G]

Oh it doesnt blow white smoke either.... I was also thinking maybe it could be something in the driveline holding it back?

[paulr33]

more boost doesnt always equal more power. this is only true when you are still in the effeiency zone of the compressor. if its only 10rwkw who cares. its hardly anything significant. if the turbo was shagged i would expect it to be more obvious. lots of lag, squealing coming on boost, smoke etc

[Adriano]

I would do a warm compression test and then a leak down test if nothing came from the comp test, from what i recall, stock sr20's are quite fragile at 190kw, and 6 months of thrashig will usually break pistons.

[R33S2]

My old turbo lost power and it was broken manifold studs and when I went to fix em the manifold was cracked as well. want a pic?

[Busky2k]

Have you checked your turbo for shaft play? Its probably not the turbo thats causing you to be down on power. Your exhaust might be a lil restrictive, tune not agressive enough, boost leaks etc.

[Adriano]

Which pipe exactly is cavered in oil, can you trace where it is coming from

[Mr_G]

Thanks for the replies guys. Ill be going for a comp test next week just to put my mind at ease.

As for the manifold, it was changed to one of those stainless items that you get off ebay cause i got a good deal on it, however I still have the standard one just in case.

Ill be replacing all the vaccum lines, will be taking off all the IC hoses and placing them back on.

The pipe that is covered in oil is the one that goes from the cooler to the turbo. It has nothing else plugged into it, so i assume the oil comes through the turbo somehow?

[Busky2k]

Its probaby residue from when the breather from the rocker cover was there in the past..

[Mr_G]

Got the car back, heres the graph.

Please critique your suspisions regarding the turbo.

From looking at the boost curve, it seems as though the actuator could be faulty?

But from driving it now compared to what it used to be, drives a whole lot better indeed

If the turbo is on its way out, Aarron from Sliding Performance will be getting the hi-flow job

[Adriano]

Thet a nice gain in midrange

[RB30-POWER]

looks alright to me.

the boost is dropping away as you can see, so power is going to drop, get it to hold boost and it might fatten up a bit at the top end, although that may not be too easy if the turbo is starting to drop out of its efficiency range.

could be a gazillion reasons why the power is 10kw different to other cars, i wouldn't worry to much.

[T04GTR]

turn down the gain on your boost controler and turn up the volume. its surging. ie.. the boost isnt stable

[Busky2k]

Yeah your EBC is not doing its job of holding the boost. I wouldnt say the actuator is stuffed beacuse its still holding 14psi at 6500rpm (my old stock turbo'd S14 could only hold 11.5psi by then lol)

I wouldn't worry about another 10rwkw. Thats only what.. a bit more than 5%? Thats nothing, so long as your happy with the car!

[Mr_G]

Thanks for the replies guys. At least ive narrowed my problem to be something to do with the turbo and not the motor.

But the mid range gain is very impressive. This was in combination with an adjustable exhaust cam gear. Now when it comes on, especially in the wet, its lights em up easy!

Im pretty sure from looking at the graph, the actuator is busted. Im running a turbosmart boost t, which holds fine on my friends car, but my car, doesnt seem to hold as fine So thus, i think the problem is the actuator.

What do you guys think of this theory? Although there is the possiblity that the turbo could be abit busted, causing the eratic boost curve

[dead32]

mine fluctuates aswell, rb20

[nfi]

Your wastegates fine. When that screws up, which mine did I had no boost at all in the top end.

I wouldn't worry too much about the power figure. 186rwkw is about right. Mine has made between 187-195 on the same dyno on different days on the same boost setting. Just see if you can get the boost a bit more stable and your set. All good.

Having a bit of oil residue in the pipework is pretty normal. As someone else said it will just be the head breathing.

As for the comment about sr's cracking pistons at 190rwkw- anything is possible but it is the common consensus that a sr20 if tuned properly will last forever with <=200rwkw. 200-250 is leaning on it and beyond that things start to break. That said the GT Autosound drift car (HPI) which is now Christian Pickerings drift car makes 306rwkw with a stock bottom end!