Exhaust Tuning Suggestion

[AutoBlackie]

Acoustic,
If I am not wrong, exhaust lengths are tune as resonators. Their length matches exhaust timing and using reflected negative sound waves helps draws exhaust gases out. Since the length is constant therefore it can only be optimised for a relatively fixed rpm range. Of course, the pipe size and gas temperature will also determine the velocity of evacuation.
If you agree with me, from your calculation, can we half the primary length since by doing that we are making the primary to resonate at an octave higher using its harmonics instead of the root frequency to do the work? Wonder if it is effective. By making the primary half could actually safe manufacturing time and costs.
Just a thot. Hope that this does not sound stupid.

 

[Acoustic]

errrrr - I'm not sure at all ...... I don't know as much as you .....

 

[artnet]

eh.. just to share my experience. not regarding ur calculation above.

i'm using 2.5" for everything after the catalytic convertor. other than tat is stock.
feel like no torque... but very smooth pick up. a bit regret getting such a big pipe.
then changed a middle bullet... it got a pipe inside it from 2.5" inlet to 1"outlet. can feel the torque now...

the sound is loud... dislike it. but money already spent... sayang if change again.

 

[Acoustic]

aiyah, I mentioned in my website to use 1.5" only mah, why use so big?

when using bigger pipes the RPM optimization frequency is different liao.

If originially for 5k rpm, using 1.5"

It will become something like 8k rpm when using 2.5" - cannot simply use big big ones :(

 

[AutoBlackie]

One friend says, if you can't get the exhaust right, just use stock.
Improve on cold air induction instead.

I really agree with him. I've tried those K&N mushroom looking filters fitted right beside my blacktop engine. Feels very sluggish during hot days, especially during traffic jams sucking hot air only. Travelling at night, with cool dry air, surprisingly, from Ipoh to KL actually gained me an extra 30km worth of petrol! Even going @130km/h average. Didn't know that cold air makes such a lot of difference! Heard theory about this but this is impressive experience for a change.

Finally, fitted my stock plastic air filter box back(helps insulate heat from engine better), the difference between hot & cold driving becomes less significant but can't compare to cool night drive with K&N. However during high humidity, cold air induction also fail la.

So conclusion, find the least restrictive filter and go for cold air induction. I dunno, my engine bay seems too cramped for me to improve on this :blink:
Of course, if can find good exhaust better still la!

 

[Master D]

CAI does make a difference!! Not just on the consumption bit but also on the general "smoothness" of the engine. I am however very sceptical abt heat shields and thermo wraps...although the general idea is to minimise the heat in the engine bay, I am not convinced that they work as well as advertised.

Exhaust piping size as well as the degree of the bends will dictate the how much torque, drag, how light the throttle feels and also max speed....I had a straight flow setup that gave me good pickup but bad max speed and then a s-flow setup that somehow, sucked from all aspects. Trial and error costs too much so I'm presently stuck with the latter and will soon opt for a "quiet" setup for a change.

One thing that I notice is that people tend to want a big @ss exhaust pipes visible from the back that basically does nuts for the actual performance of the car. Add a big oversized muffler and all you get is a screaming hunk of metal that has no go and generates hatred by bike riders and bystanders...not to mention neighbours.

I'm running 2.5" piping front to back....not a good idea...will go for 2.2" soon.