I was gonna have a new exhaust fitted but am a little confused. There seems to be a split opinion on whether the Scooby should be free flowing or have some back pressure. On speaking to a well known exhaust maker they have stated you have to have a restrictor to get back pressure and that free flowing will lose power?

Others say you get more power the freeer the system is - Will a cat give that restriction?

I'm a little confused?

Don

 

It depends where in the rev range you want the power and if the engine is otherwise standard . On a standard engine if you have a free flowing system you will gain power (and noise ) at higher revs at the price of power and torque at lower revs . If the engine is modified you will generally need a free flowing system to complement the mods .
The old exhaust on my car was completely rotten . The packing inside the back box was gone completely so basically I had a straight through 2.5" system which was VERY LOUD and I had to rev the car to get it to go . I replaced it with a ss backbox and a straight pipe to the downpipe . The car is a lot faster and torquier and I don't have to rev it as hard , plus a lot quieter .

 

On my B4 which, unlike the WRX, runs a sequential twin-turbo setup (1st goes from 0 to roughly 4,000 rpms and the 2nd kicks in over that), there is a definite difference in the type of muffler and the effect of back pressure has on performance.

I've currently got an HKS 'Hypermuffler' which is relatively free flowing so in the low end, I'm losing initial torque but once the car is moving and the revs are up (over 3,500 or so), it's a screamer! Compare that to my friend's car which has the Fujitsubo Legalis R Evolution which is a bit tighter and gives him better initial response and mid-range. He would probably lose out in total HP at the peak, but since it's rare to hit that (you would be doing upwards of 200 km/h), it's not that big of a deal...

Having said that, I am actually debating whether I should swap out my muffler...

Cheers.
-

 

So it seems that on a slightly modded car then higher up the rev range you get the power - so with say a modded VF22 and Motec/or Link or other after market ECU it will be a screamer.

So the Scoobysport exhaust is not the one to go for as this has a restriction,going from 3 to 2.5 inch (to fit to UK me thinks... not for power gains - commercial)- I'll get a full 3inch straight through.

That said I suspect that the difference between say a Scoobysport and say a HKS is minimal - HKS should havee more top end power but Scoobysport will produce more Torque -Hmmmm... its HKS for the Rolling Road but Scoobysport for bouts about town!

Now I dont really knwo what to do!

 

If I was you I would find somebody with a HKS system fitted and listen to it on the move . It tends to be very loud which can get annoying on a longish journey . It also attracts the wrong sort of attention ie cops . The ss system gives the car a nice burble without being too loud .

 

Just had a Blitz Realize TT exhaust fitted (see today's post under "Subaru Legacy RSK B4 Japan Spec") and I don't reckon it's loud at all, but maybe I'm getting deaf in my old age .... Or it could be that the Legacy RS exhaust system is generally more muted than an Impreza's anyway.

Brian
[edited 'cos my brain/finger co-ordination isn't working too well this morning ]

[This message has been edited by HunterB (edited 06 April 2001).]

 

I'll listen to a few and decide

I think I've heard the HKS before -its got a huge rear silencer -not as loud as Blitz!