un-tuned Rv8 exhaust pipe size?

ratwing · Post by **ratwing** » Fri Jun 22, 2012 5:19 am

Theres a lot on manifold design here but I can't find much on the rest of the system - I've a standard Rover V8 from a P6.
If it makes a difference, I've got one pipe each side about 4 feet long (maybe too short but its as long as I can go) pointing straight up towards the sky and no balance pipe (not much room for one, does it make that much difference?), there's a picture in 'Your Cars' under Newbies V8 trike.
I was thinking of a metre of perforated tube wrapped in Acoustafil inside each of my current pipes which are open straight 3" pipes (quite noisy...) what would be the better choice, 1 3/4" or 2" diameter tube? Or a different size?
If I come across a pair of cheap good SD1 heads I'll get them, meant to be far superior breathing to the P6, would the same size pipe suit these heads too?
Sorry its a lot of questions but I only want to do this once if possible - Thanks in advance guys

ChrisJC · Post by **ChrisJC** » Fri Jun 22, 2012 7:00 am

If you can fit a balance pipe, it will make it much quieter / smoother sounding.

Chris.

kiwicar · Post by **kiwicar** » Sun Jun 24, 2012 9:08 pm

Hi
perforated 1.5" pipe inside a 4 foot of 3" outer as a straight through pointing at the sky would be very quiet at ground level.
Refinements might be to do 6" of unperforated 1.5" pipe into the 3" outer , a foot of 1.5" perforated followed by 6" of unperforated with a baffle between it and the outer with about 18 1/4" holes in it then a foot and a half more perforated and a final 6" on the end, maybe with a 1" stub protruding, all with some sort of packing around, that would be a little less prone to boom.
Best regards
Mike

ratwing · Post by **ratwing** » Sat Jun 30, 2012 9:59 am

Thanks kiwicar, the combination of small & big holes sounds good (sorry, bad pun...) I came across some 1.75" perforated stainless pipe, bigger than planned but going dead cheap so bought it, there should be enough to experiment with - I'll try it as it is, then with some of the holes enlarged/chambered as per your post and see which sounds best. Also got some acoustafil packing, its reasonably cheap on ebay atm.

ratwing · Post by **ratwing** » Tue Jul 03, 2012 3:37 pm

I started with something easy to see how it sounds before going down the route suggested by kiwicar and put a metre of 1.75" perforated pipe down each side and it was still too noisy, couldn't really tell the difference from open 3" pipes.
I wrapped the perforated pipe with 1m x 300mm Acoustafil each side and its sounding good - quite deep and fairly quiet on tickover but still loud enough and without the harsh high-pitched shriek it used to have when revving it.
The odd thing is that its reasonably quiet ticking over on the driveway but when I step into the porch its really deep and throbbing - maybe its acting like an echo chamber?
Am off to the Isle of Wight so the packing will get nice and hot and fully expand so if it ends up too quiet I might end up taking some out but for the moment its job done