Matt1783

EDIT - I opted for sound deadening rather than a test pipe. Go to the last page of the thread for pictures, cost analysis and results.

Hi chaps,

I purchased an unknown exhaust from another forum member which I'm totally happy with - apart from between 3-4K rpm particularly when lifting off the throttle, the drone is insane!

After a lot of research ive decided my first port of call is a test pipe, so I began looking at them. My car is a 2001 so shouldn't throw a CEL with a Berk pipe... Although I'm open to a different brand, Berk seem to be well regarded.

I guess my most pertinent question is this: what diameter do I need for the greatest amount of drone reduction? I've done a lot of reading about resonance and I'm trying to understand the science behind it... but there's a lot of conflicting information with regards to matching the pipe to the cat back, or to the header. My gut feel would be to match to the header, moving the change in diameter as far back as possible... but either way there's a change in diameter which is going to interrupt airflow.

In addition im going to throw some insulation into the boot and around the passenger area for good measure and maybe even heat wrap the exhaust because apparently that can help, although I'd imagine that's more hearsay than anything.

Any input greatly appreciated!

Cheers

har-vey

Honestly the amount it reduces the drone is questionable considering it will also make it louder. Almost all aftermarket exhausts drone on the s2000 between 3-4 unless they have some sort of additional resonator built in.

Nottm_S2

I agree with Harvey, i have an HKS which includes a big resonator and still drones

bigger bore is better flow is louder generally

flanders

A test pipe can make a massive difference, I know from personal experience.
T1R 70mm exhaust with 70mm HFC had big drone on certain rpm's but with test pipe almost nothing.
I would match the test pipe to the diameter of the exhaust.

Nottm_S2

that's interesting, on my Skunk2 SC car it was louder with the test pipe (and more boom)

CHIPPO

That little pipe , dead end on the OEM is the kiddy, it's a Hemsoltz resonator and it's one of the main reasons for a lack of drone between 3 and 4 k , which of course is the rpm at which we sit most of the time , result headache.

i forget all the science behind it , when I had a HKS I looked at adding a Hemsoltz but in the end couldn't be asked to do all the mods and fabrication to achieve the end result I even came up with a way of an adjustable one so you could tune the drone out , can't even remember exactly where the OEM is located under the car. The volume diameter and location influence the Hemsoltz

i dare say Honda spent ages and lots of money on the OEM so it doesn't drone , I doubt many of the aftermarket jobbies have much spent on research full stop , it just needs to look pretty and make noise. In similar fashion to a 1litre Corsa ! Oh really how old do I sound.

another reason,I dare say the OEM doesn't drone is it pure weight and density ,


i just just did the UK mod , does the trick , bit of noise and no drone , keep wondering about replacing the back boxes with some cheaper tubular boxes or none at all just pipes , I wonder what that would sound like and what the drone factor would be ? Any one got an OEM pipe they want to throw away for experiments !

Matt1783

I appreciate everyones feedback; but "Honda designed the exhaust that way so take the rice cannon off" isn't quite what I was hoping for

There absolutely must be some science in the diameters of the pipe, gas flow and noise ... I'll even take "bro science" at this point!

Seeing as there is so much conflicted info out there on the exhaust side, i'm going to try insulating up the boot, rear deck and passenger side first. Cheaper and if absolutely nothing else will improve my sound system!

har-vey

From a performance point of view if you go for a decat, I'ts best to match the size to the catback. Having two small changes in diameter had more of a negative effect than having one large increase. Saying that mine are different as i couldn't find a 3" decat

Matt1783

Cheers Harvey, makes sense. Was talking to one of my work colleagues about this... Interestingly he said the smaller the diameter of a pipe the faster air gets forced through it - the faster air gets forced through something the bigger the noise it makes. He likened it to shouting in a cave, versus shouting in a cave with your hand up to your mouth to make the echo louder. Makes sense I think!?

har-vey

I like the thought behind that but i don't think in practice it works like that. 70mm systems tend to be louder than 60mm systems.

Think of it that the 60mm system is restricting the flow, imagine trying to shout through a straw. Increasing the diameter allows more gas flow thus increasing the sound.

Saying all that you also need to consider the number, shape and size of the silencers that are in the system.