Exhaust Length

[b20b]

Does anyone have any information on this topic?

Is there a length for the straight pipe that is just after the collector of your extracters that leads to the first item in your exhaust system eg. cat or first resenator.
I have heard that this length is critical as if this length is to short top end performance is hurt... if this length is right it allows your extractors to perform correctly
I have a theory that this is why some aftermarket extractors have a length of pipe included and the cat needs to be moved further back

Any Comments

[ALLMTR996]

Does anyone have any information on this topic?

Is there a length for the straight pipe that is just after the collector of your extracters that leads to the first item in your exhaust system eg. cat or first resenator.
I have heard that this length is critical as if this length is to short top end performance is hurt... if this length is right it allows your extractors to perform correctly
I have a theory that this is why some aftermarket extractors have a length of pipe included and the cat needs to be moved further back

Any Comments
PM Dyno Dave he will answer that for you if he is in a good mood. :p
ALLMTR996

[b20b]

PM Dyno Dave he will answer that for you if he is in a good mood. :p
ALLMTR996

Thanks for that I've pm Dyno Dave but in case he is busy and cant answer any one else have some thoughts

[locote]

if the cat gets moved further back it wont do its job!!
catalitic convertors need to get hot in order to work.
if they are far away from heat source, you might aswell not have 1

[sivic]

he's only talking about a change in distance of inches so not enough to affect the cat's performance

[DynoDave]

he's only talking about a change in distance of inches so not enough to affect the cat's performance
Incorrect info dude the closer the cat is to the collector/flex joint the better it will work as it rely's on HEAT to function correctly.And if you move it back even a few inches will effect its performance.
Regards Dyno Dave

[iamhappy46]

DynoDave,
If the headers are designed to improve gas flow and heat retention whilst improving power/torque, maybe the Cat could be moved back a few cm's?
Say Brand XYZ headers show a distinct power/torque improvement by lengthening the secondaries past where a factory cat would sit, would it be beneficial?

I think that was what the original question refered to, with regard to aftermarket pipes having longer secondaries...

[b20b]

DynoDave,
If the headers are designed to improve gas flow and heat retention whilst improving power/torque, maybe the Cat could be moved back a few cm's?
Say Brand XYZ headers show a distinct power/torque improvement by lengthening the secondaries past where a factory cat would sit, would it be beneficial?

I think that was what the original question refered to, with regard to aftermarket pipes having longer secondaries...

If you look at some aftermarket extractors the collector moves further away from the exhaust port as compared to type r extractors (Dc2). From what I'm told If this collector point moves you need to move the the first item in your exhaust system.( usually the cat ) The distance I'm told is half the length of the extractor. this length is what helps give the top end benifit from the extractors

[b20b]

Anyone got some imput

[Limbo]

I did some reading once on this and it comes down to the engine frequency so that the lengths are at a certain point to help the exhaust gases flow in a resonating effect. This also helps to keep the pipes the exact length so that they merge at the same time without turbulance. The only thing is it is not easy to measure that is why you have many different types of designs. Also some designs are not physically possible due to the shape of the car, heat factors, speed of gas, ignition, detonation (and maybe the frequency may affect other parts of the car?) etc... Otherwise you would have one ultimate set that everyone would have.

If you wanna maximise the power buy a reputable brand like Toda, Apexi, mugen who have put lots of time getting a good tune length and maximising the extractors.
Also they will be useless if you don't do the rest of the piping also.....

The rest of the piping will also effect the gasflow and frequency. That is why whole exhaust setups cost so much as they research and make them work together in harmony.

But all that said any equal length exhaust with minimal restrictions will give a decent flow and you'll prob never realise the difference. Rem you might make 10-15kw at engine with an exhaust. What's 1kw? spend you money on something that will give more power i.e CAMs or aftermarker computer tuning.

[Limbo]

O and depends on your mods to take effect of the exhaust...

[b20b]

O and depends on your mods to take effect of the exhaust...

Thanks for that .