...so people have to make there cars quieter to use test tracks..i noted Porkie said it aint hard to quieten a car...very true BUT after looking at Martin H's masterpiece of an exhaust surely this has a dramatic effect on BHP?.....Isnt it better to just run less boost (i asume its less noisey)..Are we gonna see cars that dyno at 700bhp on the dyno(in which the big playas all harp on about) in reality be 600bhp due to bigger exhaust restrictions?


Or am i wrong as per usual.

 

I was thinking this after the brunters post..

Do silencers restrict power?

 

I don't understand how they can cause more back pressure, arn't they just effectivily a blanket around the exhaust to dampen the sound?

Good post.

 

It's a valid point, especially re: trackdays.

Too many of the very high powered cars can't actually get away with running close to full power on circuit.

I'd imagine a lot of that is down to not spending money on decent quality product, but we'll have to see how Martin's does re: noise etc

 

Thats how I understood it... BUT thinking about isn't that how a Gun silencer works as well, and the bullet leaves the gun at a slower velocity when one is used.... So if Gas speed is slowed down then back pressure is up and power down yes???

To be honest though I don't know! I always thought that with enough silencers you CAN shut up a car WITHOUT loosing power.... maybe I am wrong though???

We clearly need someone who KNOWS for sure though...

Good post Phil, see you can do them!

all I know is my car was alot quieter AND felt alot faster once I got rid of the mongoose!

 

Porkie..maybe phychological..to me the quieter the car the faster it feels

 

I (and I suspect most people) have always found the opposite!

Loud feels fast to me!

130mph in a Lotus Exige feels alot faster than 130mph in a RollsRoyce as an example.

VERY Different cars I realise!

 

Back pressure and gas speeds are both effected by silencers.

The better the design of silencer then the more noise it stops for a given reduction in gas speed.

A decent exhaust will definately not lose as much power as the amount of boost you would have to remove to get to the same level of noise on a crap exhaust.


Exhaust technology just suddenly became a lot more relevant to modified cars in the UK, in places like germany all aftermarket exhausts HAVE to be designed with this in mind to get TUV approval AFAIK

 

Another problem is, how much you love the sound of your car...

I know I do, and it pops and bangs for a Fiesta Piece of shit, but putting in another box will stop this.......... But I suppose it's something you have to live with if you want to use it on a track.

 

Feels quick in an effortless and more powerful way when its quieter IMHO

Drive an XJR for example, its a strange feeling after a stage 3 cossie, roughly the same shove into the seat, but it feels like the car isnt trying.

(im talking about during acceleration here, not sat at speed like in your example)

 

...its realy odd as my motorbike feels faster with ear plugs in!!!

As Chip said exactly that..the XJR just felt effortless compared to a stage 3 cossie

 

i find the nosier it is the quicker it is, certainly thought my bmw was slower after it had a quieter back box put on, but then again it probably was because it was just a shitty powerflow job!!