hello all
i am new to this site and also new to the world of scooby ownership.
i have a n reg turbo impreza and have just fitted a new exhaust system and i was wondering do i need to put that weird turbo cooling duct thing that seems to get cold air from the bonnet scoop back on ? have any of you guys took it off and does it cause any problems leaving it off ?
many thanks for any replies you send me

 

If you managed to get it off in one piece then fair play to you,as the bolts normally just shear off.It is suppose to vent air to the turbo ,but in reality its not going to cool a turbo thats spinning up boost an awful lot.I have never bothered trying to refit them on the 5 wrx 's that i have changed the turbo on,and had no problems with any of them.

 

thanks very much for the reply midnight, im leavin it well n truely off looks loads better wiv out it. thanks

 

I didn't think it was there to cool the turbo, so much as to stop the turbo from heating up the rest of the engine bay, the intercooler especially, which is right next to it. If your new exhaust system is heat-wrapped, as it should be, you should either find a way to put the turbo heat-chimney back on, or get a heat-blanket or wrapping kit for it instead.

Hot intercooler = bad performance, lower MPG, and more risk of engine-damage when pushing the car hard

 

Sorry but the chimney function on the heatshield is there to cool the turbo,if you look at the way that it is shaped and it has it's own ducting in the bonnet
scoop which is suppose to direct air on to the turbo.
If you were to run a poll on here asking how many people have replaced the
heatshield after fitting a turbo , is my guess is it would be less than 5%. Heatsoak to the intercooler is not necessarily caused by a
red hot turbo, but more from the heat of the engine when
stuck in traffic & the turbo is not actually being used.
The next time you take your car for a blast when you pull up afterwards put your hand on the intercooler.
Chances are it will be cold or slightly warm.
Lock your car up and go inside, make a cup of tea and go back out to your
car 20 mins later and touch the intercooler - notice any difference.
The intercooler is hotter dispite your engine/turbo being switched off for 20 mins. You can also try this when you go out for a normal drive and drive your car off boost for 20 mins - you still get the same results.

 

The shape of the heat-shield is dictated by the shape of the turbo itself and the size and shape of the aperture below the bonnet scoop, so that doesn't really prove much. In any case, if the turbo's being cooled down by the duct, then isn't that just another way of saying that it's not spreading so much heat all over the rest of the engine bay?

I'd also bet there are quite a lot more than 5% of people who've put in new turbos that fitted a heat-blanket on them after, rather than just leaving them uncovered.

One last thing, even without the issue of heat-soak to the intercooler (or to anything else), wouldn't it make spool-up slightly quicker if the turbo's wrapped, because it'll be that much warmer? That makes it win-win, IMO.

 

Maybe we should make that the next poll on scoobynet ,lol.
Since fitting/ changing your turbo have you refitted the heatshield ?
A. Yes
B. No
Fitting a turbo blanket is a far easier option than trying to fit the oe turbo heatshield, and out of all the modded Subaru's I have seen at west mids impreza meets & other places including 555 dannys 653 bhp beast none have had a heatshield fitted.
As for slow spool up, if it does make any difference it is marginal imho ,as my mates P1 with a vf28 starts to spool up at about 2800 rpm which is what my UK car with the same turbo starts to spool up without a heat shield.

 

I think ive opened a major can of worms here lol