A1exander

Im am thinking of getting a new back box to put me on until I get the PPP kit fitted to my STI Type UK at the back end of summer. Can anyone suggest which back box would give a good ( but not too loud ) sound that will make the occasional pop and bang. I am leaving the cats in place until the warrenty runs out (which will give me more of the noise I am after once removed) and I have been looking at:

Hayward and Scott
Scooby sport
Scorpion
Magnex
TSL GRP N

Any ideas?

Andy

richiewong

Probably won't get many with the cats in place, removing one will help though

Engineer@Uni

Mate, no fuel will get out the backbox to cause a flame with the cats in place. Simple as that. If it did, the car would never pass emissions as a new car. I'm assuming youre running stock internals/ECU/etc so I'd be amazingly impressed if anything you do to the exhaust makes a pop or a bang. In order to get that, you need overfueling and reduced ignition advance to make it properly bang. The noise you hear is unburnt air/fuel mixture leaving the cylinder at the exhaust stroke and reaching the turbo, which at a 600+ deg. C temperature spontaneously ignites the mixture and causes it to burn in the exhaust. This can be brought about either by the ECU purposely overfueling to avoid detonation (im not sure the stock ECU will do that though) and or as I said earlier having it mapped in. Comonly refered to as "Anti-lag" the purpose of it is to keep the turbo spooling whne you let go of the pedal, so the lag when you're back on it later is less. It will eventualy ruin your turbo and cats.

Sorry to get all carried away there, but honestly, on a stock car bangs are extremely hard to get out of your exhaust note.

Dark Blue Mark

Full decat and Forge VTA dump valve will cause overfuel and gives minor pops and bangs.

I am not for one moment advocating a VTA dump valve though

I get some fairly large cracks from mine on overrun, but have a 3" system, headers, etc etc....

MB

hades

Not quite true to say you need a full decat and VTA dump valve. I get minor popping on mine, with a sports cat and the OEM dump valve - enough that others following have noticed/commented. I believe a standard ECU will allow gentle popping once below over-run fuel-cut-off (2000rpm?), although you'll probably need a full exhaust to hear it.

If you want flames on over-run, then you need a full decat and lots of over-fuelling.

Dark Blue Mark

I Didn't say you "need it," if you read again, I just said it does

Flames are rare on overrun. Anti lag or the sad spark plug in the til pipe are your best bet.

MB

A1exander

Thanks for the reply guys but I am not after flames or anything overly loud as per the original post. I have had all that when I used to own modified Ford RS's years ago. In the past, some back boxes I have fitted to other cars (non scooby) have given out the occasional pop when decelarating on the over run or changing up or down the box. The PPP STI I drove was poppy though I find the back box a tad too tame on the noise front but I dont want to go much further than the PPP exhaust volume or tailpipe size for now.

hades

MB - You didn't say you need it, but adding the three previous posts, it could have been construed that way.

Regarding "only slightly noisier than PPP", there are a few options. Things like the TSL Group N, Scoobysport quiet might suit. I'm quite fond of my APS (full system admittedly), which is about the same measured volume at steady throttle, but slightly more pronounced when you're giving it some.

No offence, but if you're intendiing on going for full PPP soon, seems a little silly to me to spend out on a new exhaust to cover a few months in the meantime. If you've got the money, get the PPP now, if you haven't - don't waste what you do have!

Dark Blue Mark

Yes - but I did word it carefully and always do

MB

A1exander

Thanks for the reply and no offence taken,

I may not use the PPP backbox when I get the package as it does not have enough volume for me and will probably be used only when the car goes in for service or warrenty work. The reason for the delay on the PPP kit is due to the stupid addition to my premuim if I fit it on my existing insurance policy ( it almost doubles )