I just installed an HKS downpipe and K&N air filter on my otherwise stock 93 FD. Perviously the turbos were nearly silent. I am now hearing significant air rushing, wooshing sound when I accelerate rapidly. I used a pineapple racing carbon downpipe gasket, new oem studs and nuts, and I used the oem brace to support the HKS downpipe. I do not think it is an exhaust leak because it sounds totally normal at idle. I checked for loose hoses and did not see anything. Seems to have lots of power so I don't think I have a boost leak.

Can anybody comment on if this is normal. I know describing and diagnosing a sound is a little difficult. My last turbo car, Volvo S60R had very faint turbo noise. I like the sound I just want to make sure this isn't a common problem sign.

Thanks

 

The stock FD downpipe has a precat in it. The HKS downpipe does not. The precat is going to muffle the turbo spool noise a bit. Additionally, removing the stock airbox and installing the air filter is going to do the same. I noticed a significant difference in turbo spool volume when I removed/replaced my stock airbox. It was even more prevelant when on my FC years ago. I would say it is normal and you are perfectly fine.

An exhaust leak is going to be a ticking noise all the time, not just at idle.

 

You should hear it with a stainless steel down pipe. It sounds like a vacuum cleaner. HKS is cast iron so it is thick and it does mute the noise down.

 

Yup if you removed the stock air box in favor of K&N filters you will certainly hear the turbos lol.

 

Still running the stock box, just with a K&N replacement.

I like the sound. I can only imagine it with a stainless pipe without the big cast iron HKS piece.