A short while after fitting my Scoobysport downpipe I began to notice a kind of a "dry rattle" at a certain rev band coming from the engine bay.
I assumed that a piece of the newly reshaped heat shield had developed a tendancy to vibrate at a certain frequency, but investigation seems to show that everything is tight and solid.
I'm now very suspicious that the noise is coming from the turbo unit itself and worried that it could be a worn bearing as the sound is very much like you would get from a shot water pump or alternator.
I'm certain that it is nothing to do with the downpipe itself and it's probably more that as there is a general change in the noises that now come from that area, I am just scrutinising it a bit more.

There doesn't appear to be any boost problems (1.2 Bar peak, 1.1 held; no boost mods) although lately I've had the feeling that a the cars general urge may be a little blunted. That could just be down to the "reverse placaebo effect" though.

The car incidentally is an STi4 with a VF24 turbo and it has done around 43,000 miles.

Any suggestions, comments or experiences would be much appreciated.

Neil.

[Edited by Neil F - 2/16/2002 2:33:05 PM]

 

Neil
Whip off the turbo shield and rest your finger on the waste gate actuator arm - do this with a cold car . I have the same problem. At certain revs (mainly tick over – very annoying) it rattles like a loose heat shield. I think I need my turbo over hauled and the arm needs to be re-bushed.
You could have the same problem.

Cheers
Iain

 

Thanks Yee, I'll try that.
My rattle tends to be at around the 3-4000 rpm mark and alls fine at tickover.
You get the rattle with the car both stationary (no boost) and when driving (either on or off boost).

Any more ideas?
Any reccomendations for turbo specialists in Essex/East London?

Neil.

 

Are you sure it's not the brake pipes rattling against the bulkhead? There's a resonance that kicks in around 3-4k rpm.

 

Now that would be good news Carl!
I did spend quite a long time feeling around for anything that was vibrating and I didn't notice the pipes rattling but I'll make a special point of checking it out.
I don't suppose I checked absolutely everything though as I had to give up after while due to the heat build up and the neighbours windows shattering!

Neil.

 

Stick a piece of corrugated cardboard between the pipes and bulkhead. If it makes a difference, get something a bit better like some neoprene.

 

Hi Neil,

Off the subject I know ...but what is you peak boost when say at high speed i.e. 120 when you floor it. I ask because your boost is the same as mine but I get overboost in 5th and high spped when I floor it.

I am fitting a knock link tomorrow ...just to be safe.

l8r....

Julian

 

Julian.

I'm not sure to be honest, I'd have to check. But I do know that I've never had overboost cutout on the occasions that I've done those sorts of speeds (track days and the like... ).
I'll let you know as soon as I can.

Neil.

 

Hi Neil,

There is no overboost cut out on an STi as I understand??? So be careful.

Cheers

Julian

 

No overboost protection?
I must admit I'd never heard that before but be I'll be sure to be careful "in testing"!

Neil.

 

Yeah like me at 120mph....

I recon you should fit a knock link... they are fairly cheap compared to the possible engine damage and you can tell if it really is super unleaded you filled up with ...or if the tanker driver made a mistake!!!

Cheers

Julian

 

BTTT for any more advice

 

Neil

The ecu will try and retard the ignition but you won't get an abrupt cut like on other models. So what you would see is a high peak and then the feeling of a flat spot as the ignition was retarded in response to knock.

Believe me you may have a Christmas tree lit up on a knock sensor without knowing.

I have now set a conservative 1.2 Bar peak and 1.1 Bar held boost characteristic on my car.

l8r

Julian

 

Normally this is a split or cracked heat shield resonating, the turbo heat shield is the probably culprit. It will have been modified to fit the downpipe and this can happen.

There is definately a boost cut on all Subarus.

 

Bob....

I was running 1.35 Bar Peak on a standard ECU..... surely this should have caused a cut ?? When I connected a knock link (supplied by your good selves a week ago) the transitional knock was momentary but worrying. Always high over boost ... in 5th.

When I checked a couple of tuners they said the cut on an STiV was not abrupt ???

I have now modified the restrictor and get a good spool up with only .1 Bar overshoot. (1.2 Peak and 1.1 Held)

Any thoughts would be appreciated...

Julian

 

yep, sounds like a heat shield, usually on the headers and occurrs at circa 3K - 4K rpm. There will be a small crack on one somewhere, easily fixed.

Mike.

 

Thanks guys.

I Modified the turbo heatshield myself when I fitted the SS downpipe and it was in very good condition (well at least until I took a grinder to it!) so maybe it's the one on the headers?
I guess I will just have to look a little closer!

Neil.

 

If you don't have any wiring around the heat shield why fit it back on. I have run for 18 months on 2 cars without a heat shield. This isn't abnormal and I know many friends including most privateers who rally that do the same.

Julian

 

I must admit I have been thinking about this as I did lag the downpipe, but I was a bit concerned about heat from the turbo itself affecting the clutch and brake master cylinders.

There is also a thread on here at the moment where they are discussing whether you should lag the turbo as well as the downpipe, but I'm a bit nervous about keeping the air charge any hotter than it needs to be pre-intercooler?

Neil.

 

Can only speak for myself ...but I had no probs and Stuart at Townend (Good Dealer BTW) agreed with me no probs. They run 2 rally cars too.
Off to work now ...l8r Julian

PS I am hoping Bob will reply to my message re: boost cut.... my old peak of 19psi on standard ecu ???? with no cut ???????????