AWK-53

Whats the rule of thumb about exhausts and loosing silencers in the system?

I've got a MK2 Golf GTI 16V with a custom made exhaust system, the downpipe silencer has been removed and I now intend on having the centre silencer replaced with just a straight through pipe leaving the backbox as the only silencer in the system.

However some people are saying it may actually loose me power as some engines like to have a good amount of back pressure and so work better, any truth in this? I always thought it was best to get the gases out as quickly as possible?

Car is used for racing so no problem with noise etc?

Any help with this appreciated before I pay RS Fabrications a visit

AWK-53

Any thoughts guys?

tabetha

The effect is likely to lose torque from what I have seen over the years, but not necessarily gain elsewhere.
tabetha

london_chris

n/a cars do rely on a certain amount of backpressure to help scavenge the exhaust gases,
they usually have a couple of silencers and that is sufficient, i wouldnt remove the boxes just as it wont help to gain any power and if anything i would imagine you'd lose a bit of torque too?

Diablo

iTrader: (1)

Many years ago, we did exactly this to a mate's MK2 16V. It was louder however, we did not feel any loss in torque. It also seemed to rev more freely than before. I would go for it...

Seademon

Its not the same car but I've got just a Sebring backbox on my VR6 and I havent noticed a loss in power, no cat, no middle boxes just the back box. Pulls the same as it did, no difference that I can feel when driving it hard.

AWK-53

Thanks for the opinions guys, not sure what to do now?

I think that any form of silencing will always cause a restriction and so cost power but I'm not sure?

Most of the cars racing only seem to have 1 box on so think I may give it a try.

Barry_GTi

Years ago I discussed this with a knowledgeable(spelling?) chap.

Basically ha said, NO engine likes backpressure, the less you can have the better, it is actually all to do with pressure waves in the system. The location of the first box after the primaries actually dictates the torque curve to a large extent. I believe closer to the primaries is more torque low down and further away is higher up the rev range, assuming all other things stay the same.

They actually had a race car some years ago that was the usualt 2.25" from manifold to the first "box" and then expanded to 3.5" pipe with a straight step, no taper used. This then continued at this size to the rear where the back box was. Idea being the step in the correct place maintained torque but no back pressure. This was back in the early 90's and a year after they had used it a BMW touring car team used the same design.

So basically no, you don't need back pressure, get a Dave Vizard book, it's all about pressure pulses and waves.

JTECH James

iTrader: (13)

be aware, the mot critera has changed very recently,

and any exhaust considered to make more noise than a std system can now be failed.

the wording has been changed.