Manute951

Hello!

I´m a new member here, from Spain, so a salute for all of you, and please excuse my english!

My background is,I have an 86' 951 i bought in a less than perfect state 15 year ago...was not expensive but the poor car was beaten up, eating almost 1 liter oil per 160 miles or so. Imagine...
5 year ago I overhauled it, was a lengthy and very expensive overhaul, a few times the price of the car, iti ncluded new pistons with rings, new transaxle, new turbo (k26/6 since I wanted original specs) head work...etc etc. Quite expensive but I got an almost perfect mechanical state, no oil consumption at all and great performance. I also added a lindsey boost enhancer that really did it's job.

More recently I did some maintenace changing part of the steering, new shocks, new clutch pump, etc. This was the last maintenance, 2 months ago. Not cheap also....

So with this background, here is my question related to the topic...

Yesterday was driving through a tunnel, when I noticed the sound ofthe turbo spooling up and down while accelerating. And I thought "how cool the turbo spooling"... But after exiting the tunnel I turned off the stereo and while accelerating, I still heard the turbo spooling up and down...very subtle, a very light " pssttttt.....psssssst". Then i tought "did I heard this before?? Is this normal?" I kept driving and I still heard the very subtle sound of the turbo spooling up and down. When above 3k rpm, I heard nothing, and at the end of the trip when the car was hot, the sound was even more sobtle, almost non noticeable.

So now I dont know if i'm too paranoid about this...I remember when the car was not repaired and i had the original busted turbo that it was quite noisy, but i cant remember hearing it after the overhaul.

So...are you supposed to hear a little bit of turbo spooling on a stock car? Or should you hear nothing? I checked hoses and apparently they are ok, and oil consumption semms normal, almost zero.

I'd like to know if i'm too paranoid or not...what is your opinion??

Thanks!!

rlm328

The up and down maybe the result of your waste gate, is it he original waste gate?. But yes you can hear the turbo spooling a real fun sound.

neunfünfeins

You lost me with the "and down" part.

My 951S with the stock K26/8, I hear it spool up then a constant "wheesh" under boost, with the windows down and some surface to help reflect the sound off of (even a guardrail or jersey wall)

Whether or not you can hear it, if it seems to be boosting properly then it's doing its job

Manute951

Yep I still have the original wastegate...Thanks for the info!

Let´s see if I explain myself better...I hear it mostly when driving not very fast...let´s say cruising 2.800 rpm or so, with little or no boost. Let´s say you press throttle a little bit so you go up from 0.4 to 0.8 bar or so...I can hear turbo spoolin up "weeeEEESSSHHHH", and it seems when it reachs a peak, maybe wastegate opens and reliefs pressure and I can notice turbo spooling down..."WEEEeeeeessh"...It´s not very noticeable, I think if I make a video you would´nt notice.

My grilfriend has a little turbodiesel and has a very similar sound when driving throug tunnels or reflective surface...you press pedal, hear turbo spooling, then maybe boost control reduces pressure and then turbo spools down.

If I drive with a constant acceleration, I can hear almost nothing about the turbo spooling, as above 3k rpm or so other engine sounds appear and mask everything.

The only thing worying me is that when I had the old busted turbo, sound was very noticeable, maybe because was worn out and out of balance. I read some opinions that a good shape turbo should make no noise at all in a 951. But I´ve also read opinions like yours that it´s normal to hear it a bit.
As you said, I hope, as pressure is looking good, I should not worry at all.

Black51

I think it's time to pull the j-boot off the turbo to look at the wheel blades and check for shaft play. If all looks good there, check the turbine outlet/downpipe connection to see if there is a gap. Several years ago, I got a mechanic to do a clutch job for me and he forgot to bolt the downpipe back on the turbo. The turbo noise was quite noticeable.

neunfünfeins

My K26/8 is original with 90K on it, and I notice a bit of oil splatter from the exhaust, so I'm sure it's getting a little sloppy.
Still produces 1.1-1.2 bar (in cool weather), so it'll do until I can address it.

Manute951

I rechecked hose connections and they seemed ok. In order to remove Jboot, i suppose i should remove air filter and MAF first, isn't it? Took another ride and everything seems ok...the sound is more like a Howl, very subtle...probably it was always there but driving with stereo on masked everything.

I have an vdo boost/vaccum gauge and mine's peak at almost 1 bar with this cold weather. Pressure when coasting with no power is about -20 in.hg, so I bet there are no leaks for now.

Humboldtgrin

shortyboy

Check for vacuum leaks on vacuum lines and J-Boot to turbo. Notorious for having leaks when hot, since rubber will get softer when heated up.