Exhaust size & bhp.

[m1tch]

I had a custom bellmouth on my FC exhaust system, pretty sure mine was the only one that had ever had it done, meant that the wastegate flapper could actually open as well lol don\'t forget that the larger the pipe the slower the gasses will flow due to the volume, so make sure you match the exhaust size to the engine power/gas flow

[davehg]

i have a custom centre box and hks silent power back box on a 3.5 inch pipe and it didnt make any real noticeable difference.

[HaywardRotary]

We run 3 inch systems straight through on 3 race cars and that gets the noise down ok. All cars are running over 500+ hp on full bridgeports.

[davehg]

How much for a centre box and rear silencer with a 5 inch tail Carl

[jetpilot]

don\'t forget that the larger the pipe the slower the gasses will flow due to the volume, so make sure you match the exhaust size to the engine power/gas flow

So what effects will that have? As it seems that comment completely contradicts the article i found?

[Grant Monkhouse]

Does anyone know where to get oval exhaust piping from? As I been looking under my rx4 today whilst making things for the gear box, and I have no room, none at all:-(

[Grant Monkhouse]

From the various books I have read on turbos and stuff, it seems that once the gases have left the turbo it doesn\'t make too much of a difference.

A larger diameter exhaust on the down pipe should increase spool, good for road cars and track cars or drifting, but how much difference is it going to make for the cost of running a 4" system over a 3"?

As for bigger making a car quieter?? Hmm I would have thought that a larger diameter also the sound wave to expand quicker coming out of the turbo and make a louder crack? I\'m just guessing here BTW. On a 2 stroke when you go from a standard factory exhaust to an expansion chamber the difference is huge.

[jetpilot]

Does anyone know where to get oval exhaust piping from? As I been looking under my rx4 today whilst making things for the gear box, and I have no room, none at all:-(

http://www.stainlesssteel.co.uk/view0c98.html?id=50

How you will bend it though i have no idea

[jetpilot]

As for bigger making a car quieter?? Hmm I would have thought that a larger diameter also the sound wave to expand quicker coming out of the turbo and make a louder crack?

There is chat on fduk that 4" systems are quieter, as mentioned i have no idea how or why!

[Grant Monkhouse]

http://www.stainlesssteel.co.uk/view0c98.html?id=50
 
How you will bend it though i have no idea

thanks,the down pipe will be circular but under the car needs to be squashed tubing as i dont want it hitting speed bumps, once i get to the back of the car i can go back to round:)

[Grant Monkhouse]

There is chat on fduk that 4" systems are quieter, as mentioned i have no idea how or why!

yeh ive seen it, but i cant see it being right

[jetpilot]

yeh ive seen it, but i cant see it being right

I think a lot of these things are all hear say rather than legitimately researched, back to back tests are the only real way to find out i guess.

As Carl says with his race cars running 500hp with 3" systems (same with me), but i am now very curious to whether i would get better spool up going to a 4" or even 3.5.

Would love to see some back to back tests on noise and dyno charts, hopefully someone who is buying one of the 4" systems on fduk will provide some evidence.

[Grant Monkhouse]

Yeh but have they got anything from previous? Results to compare?

[Grant Monkhouse]

I think CJR is getting his increased to 4" might be worth getting him to do a before and after??

[jetpilot]

I think CJR is getting his increased to 4" might be worth getting him to do a before and after??

Just put a post up on there asking for some info once they have changed. I presume the car will need a remap too?