Roojai

Finally bought a scoob. Completely standard my94 WRX wagon.
I want to get as much power through a new exhaust and de-cat but I don't want the thing to be noisy. Any good ideas?? Cheers.

Judge

A decat will make any backbox you choose considerably louder than,say,just taking out the centre cat. I have a full Scorpion System which is not too loud at low to medium revs.At full throttle though it fairly howls. If noise is an issue I would avoid the likes of the Blitz Nur Spec,HKS Drager or the TSL Firestorm as these are loud as ****.

john banks

Keep the standard backbox, you'll only lose a little power.

SlowBoy

iTrader: (1)

I think the Scorpion is a good compromise. Very subtle under normal driving ie around town, but does have a nice howl at around 4,500 rpm.

Cornelius

iTrader: (2)

give hayward and scott a go,, I've got their centre and backbox, they called it "standard noise" which is louder than a stock system, but it's got a nice sporty note without being OTT, plus it's stainless steel too, excellent build quality. The person to talk to with your requirements would be Ian

Ninnybobs

I would certainly recommend the Magnex system.
Mine was recently measured at a trackday at 93 Db and yet is still capable of 350 bhp

Cheers

Martin

hoskib

iTrader: (1)

yeah, i'll 2nd the magnex, nice throaty sound that's not too loud.

trouble is mate you may catch the 'bug', i've been runing a magnex for a couple of years now and got a firestorm for a 'loud' summer, that baby's staying on for good now!

JIM THEO

Keep your standard back box or use a new age STI, old style Prodrive etc and change the rest of the exhaust with full decat and preferably bellmouth downpipe, almost standard noise with much better spool up and overall performance.
Just my opinion as have tried a full Scoobysport exhaust with perfect results but the noise was more than what expected so changed the Scoobysport back box with a STI one (have lost 8-9ps)!
JIM

john banks

8 BHP is nothing to lose when you can then use it because you don't sound like a tit when you are driving anywhere remotely enthusiastically.

T-uk

so you will be putting yours back on then

iirc that was running a tek2.5 with a sti back box and just changing to the blitz back box gave 8bhp. the easier it is for the gas to get out the better so I would try a magnex round tail.

hades

Quiet modified backboxes - Remus, prodrive, MRT, APS, to name but a few. These are all significantly quieter than a Magnex or H&S "normal", let alone the loud exhausts. All will be a bit louder than a standard box, but release most/all the power that louder boxes release.

You'll also find sports-cats and resonators tend to keep noise levels down. If you e.g. fit the MRT sports cat downpipe and resonator, and kept the standard backbox on, then you'll probably not even notice a noise increase.

Cheapest ideal option for you may be a decat downpipe, resonated centre (Magnex do a decent cheapish one), prodrive backbox

Eric Chadwick

Totally recommend the standard backbox option as the way to go. My system now consists of a lagged bpm twin dump downpipe (supposedly about the quietest and much quieter than standard subaru catted pipe), magnex mid section with resonator and standard STi backbox. I've lost the scooby blub blub blub noise that I had with the scoobysport back box I used to have on but I've also lost all the vibration that the SS box used to transmit to the car. The engine now feels super smooth, if anything pokier at low revs and with a much smoother more consistent creamy delivery. Gear changes are nicer as the revs don't drop so quick and the engine noise is more like a quiet V8, a fiat coupe turbo or Volvo T5 (sacrilege I know but the SS was starting to make me feel like a nova boy). Bpm downpipe really quietened down the noise from up front, no more strained huffing and puffing when you boot it and going back to the standard back box gave me back refinement without any noticable power loss - it just made the car feel sorted again. It's quieter than standard as I remember it and more refined with zero vibration. I think of it as a stealth fighter instead of a spitfire Totally agree with John - now I can use the performance without feeling like a plank or attracting disapproving looks driving at 30.

I can hear the stereo now and it doesn't sound so good - new front speakers on order

john banks

It is tempting. Job is trying to source a silencer to weld into the centre section as we speak.

Standard car is a wonderful quiet thrust and far nicer for daily use, funny that, Subaru did something right again

Was the 8BHP loss not with your TD05/FMIC setup?

john banks

Here it is: 30/10/03, think this is with your TD05, FMIC, headers from the figures and date.

Dyno Test: harleynew1stibackbox
===============================

Maximum Wheel Power: 262.3 BHP @ 6187 RPM
Maximum Wheel Torque: 243.3 LbFt @ 4089 RPM
Power to weight ratio: 180.9 BHP per ton

Terminal velocity due to power: 178.5 mph

In Gear Acceleration:
30 - 50mph = 3.5 seconds
40 - 60mph = 2.6 seconds
50 - 70mph = 2.5 seconds
60 - 80mph = 2.6 seconds

Speed per 1000 RPM:
1st: 5.2 mph
2nd: 9.3 mph
3rd: 13.3 mph
4th: 18.7 mph
5th: 24.6 mph

Maximum Speed per Gear:
1st: 37.3 mph
2nd: 66.1 mph
3rd: 94.3 mph
4th: 132.5 mph
5th: 174.5 mph

Total Vehicle Mass: 1450kg
Drag Co-efficient: 0.35
Frontal Area: 2.20 square metres
Wheel/Tyre Setup: 215/40/17
Engine Rev Limit: 7100
Test gear: 3
Max Speed of gear: 94 mph
Atmospheric Pressure: 0.97 bar

Dyno Test: harleynew1blitzbackbox
=================================

Maximum Wheel Power: 271.9 BHP @ 6116 RPM
Maximum Wheel Torque: 251.8 LbFt @ 4250 RPM
Power to weight ratio: 187.5 BHP per ton

Terminal velocity due to power: 180.6 mph

In Gear Acceleration:
30 - 50mph = 3.4 seconds
40 - 60mph = 2.5 seconds
50 - 70mph = 2.3 seconds
60 - 80mph = 2.4 seconds

Speed per 1000 RPM:
1st: 5.2 mph
2nd: 9.3 mph
3rd: 13.3 mph
4th: 18.7 mph
5th: 24.6 mph

Maximum Speed per Gear:
1st: 37.3 mph
2nd: 66.1 mph
3rd: 94.3 mph
4th: 132.5 mph
5th: 174.5 mph

Total Vehicle Mass: 1450kg
Drag Co-efficient: 0.35
Frontal Area: 2.20 square metres
Wheel/Tyre Setup: 215/40/17
Engine Rev Limit: 7100
Test gear: 3
Max Speed of gear: 94 mph
Atmospheric Pressure: 0.97 bar

Probably about 12 BHP difference at the flywheel, I have put the weights the same here, but as I had saved them I'd put the STi backbox with +16kg, maybe we had a different fuel level or stuff in the car, that would make the difference about 8 WHP.

Nice gain, not sure the noise is worth it though! Depends on use/mileage.