Roadster Sport Duals - 3,000 rpm Booom

Rattus · Post by **Rattus** » Tue Oct 10, 2006 3:44 am

Being based in the UK I've been waiting for the Roadster Sport for the last five months and it finally arrived last week. I fitted it and really liked the sound. Mellow, burbley with a nice rasp.

However last night I had to remove it and go back to stock, at least for the winter.

With the top up there is a booming resonance at about 3,000 rpm (my math says 100Hz) particularly on engine braking at about 65-70 mph (UK 6th gear). My daily commute is all about this range of speeds on the A14 (freeway if you will).

I'm hoping that in the new year I'll get the opportunity to tune this resonance out somehow. I guess I could try the glass packed baffles, though not sure how these would affect this boom, being installed in the tail pipes, rather than anywhere near the antinodes of this rather long standing wave.

Another tack might be putting a pillow baffle into the centre cavity of the muffler.

Any other suggestions would be gratefully accepted. I really like this product, but I just can't live with it over the winter.

Martyn

sloopercat · Post by **sloopercat** » Tue Oct 10, 2006 6:47 am

I experimented with different baffle configurations. Putting in one baffle cured the decel boominess at 3K. You might want to try that.

Interestingly enough, 5K miles later I removed that baffle for a little fun run our local Miata group was having. The boominess is no longer there, maybe due to carbon build up?

Rattus · Post by **Rattus** » Tue Oct 10, 2006 7:30 am

I should have checked here first. Thanks sloopercat, when I get decent weather for crawling under the car I'll give it a try. It's hissing it down today.

Martyn

Post by **Brian** » Tue Oct 10, 2006 9:01 am

It is hard to make ONE muffler that fits everyone's tastes which is why we made it tuneable. The bulk of customers find it just right, some find it not loud enough, and some find it too loud. Sloopercat is right, having just one baffle in will change the wave characteristics...and the side you put it on will also make some difference. Note we also have packed baffles for sale now for more control over the reduction amount.

Sloopercat is also correct about deposits. Over time deposits will increase the damping on this unit, though the deposit rate depends a good deal on the gas, driving habits, etc.

Rattus · Post by **Rattus** » Tue Oct 10, 2006 9:34 am

Brian,

I completely understand your point. It's all about horses for courses as they say. I love the sound of the RS. I just happen to have a commute that sets off the 3k boom. Darn it.

I will try the tuning tips and I may well order one or two of the packed baffles. I really just want to tune out the boom, without making the overall sound noticably quieter. As ever, advice is very much appreciated.

Martyn

sloopercat · Post by **sloopercat** » Tue Oct 10, 2006 1:38 pm

Driver's side baffle in is what did it for me.

Rattus · Post by **Rattus** » Thu Oct 12, 2006 4:06 am

Thanks sloopercat. Hopefully I'll get the chance to try it out this weekend.

Martyn

yellowcoupe · Post by **yellowcoupe** » Fri Oct 13, 2006 4:25 am

I tried removing the 2nd cat and puttin in a 16inch resonator just in front of the stock muffler. It has no boominess at all but has surprisingly made the sound throatier (like a 1980s Alfa)... interesting.

I imagine there is a bit more grunt but without a dyno... it bejust guessing

Post by **Brian** » Fri Oct 13, 2006 6:57 am

Our midpipe does very similar...an 18 inch resonator and the result there too was a very Alfa sounding note and further reduction of the resonation around 3000.

yellowcoupe · Post by **yellowcoupe** » Fri Oct 13, 2006 10:46 am

Brian wrote:Our midpipe does very similar...an 18 inch resonator and the result there too was a very Alfa sounding note and further reduction of the resonation around 3000.

yup brian... I've got 2 guys here who'd be interested in the midpipe and RS duals. But what i'd like to buy is the header.... any idea if that is gonna become available soon? (and btw, there's really no CEL with the header and your midpipe?)