RSR exhaust box

Bruce M · Post by **Bruce M** » Fri Jul 30, 2010 6:11 pm

Nice quality piece.

I wondered how likely it was to keep all the modifications internal but the extra pipes are pretty well hidden.

Adding remote switching shouldn't be a big issue but time consuming (ie expensive).

Electric control would probably be easier than setting up the cables.

Mike · Post by **Mike** » Sat Jul 31, 2010 10:41 am

Thanks to a very kind and helpful DDK'er we've had the first test run of the new RSR switchable back box, and it works really well!

Being an RSR exhaust box it was only right to try it on the real thing and here's a car that only has original open megaphones and
big bore racing headers, so it sound's fantastic but a little restricted in where it can run.

With the new box fitted, the engine warmed up and using 5000 rpm as the benchmark '3/4' throttle, the first test was with the flaps
open as you would normally have it for road use, sounds great and reads a healthy 112db.

So now you imagine arriving at the track, couple of seconds with the allen key, close the flaps and the decibel meter reads 104.2 db!

A fantastic result, corroborated by using 2 decibel meters against each other and also measuring the T/R which has been tested many
times and they were both spot on.

Oh, and before you ask, of course we tested the RSR in it's natural state with the megaphones, went off the scale on one meter but
the other caught it at.............124db

964RS · Post by **964RS** » Sat Jul 31, 2010 12:22 pm

Result. Should get it just inside the 105db loud days

Mike · Post by **Mike** » Sun Aug 01, 2010 11:33 am

Hi Jason, yes 105db was the limit we wanted to be under. Soon we will be able to test the box on Neil's new engine dyno
to see exactly what effect it has, open and closed, on performance.

964RS · Post by **964RS** » Sun Aug 01, 2010 3:45 pm

Mike wrote:Hi Jason, yes 105db was the limit we wanted to be under. Soon we will be able to test the box on Neil's new engine dyno
to see exactly what effect it has, open and closed, on performance.

That will be interesting. 105db is plenty loud for normal driving anyway...be cool to see what power loss there is?

haasad · Post by **haasad** » Sun Aug 01, 2010 5:22 pm

I like this idea very much.

Wonder if the prototype might be for sale eventually or will it be developed to be the final version and remain a one off ?

brembo · Post by **brembo** » Sun Aug 01, 2010 7:10 pm

Mike,what diameter headers did you go for?
Regards,

Mike · Post by **Mike** » Mon Aug 02, 2010 12:43 pm

haasad wrote:I like this idea very much. Wonder if the prototype might be for sale eventually or will it be developed to be the final version and remain a one off ?

Anyone interested in the same thing can contact Neil at BS Motorsport and he can organise one for you. 01296 658422

Mike · Post by **Mike** » Mon Aug 02, 2010 12:49 pm

brembo wrote:Mike,what diameter headers did you go for?
Regards,

Dougie, I'm using the large diameter RSR headers at 44mm internal diameter.
Another gratuitous picture of the noise test!

Mike · Post by **Mike** » Thu Dec 02, 2010 4:30 pm

964RS wrote:..be cool to see what power loss there is?

Just to finish off this thread, we've now tested the 'flapper' exhaust box on the engine dyno, and very interesting the results too!

Neil was testing a 993 motor he had built, and after running it with a Cargrahic exhaust we put on my headers and the RSR box
for a flaps open flaps closed comparison. Unbelievably there was only one horse power difference between flaps open and flaps
closed, with the extra one hp coming with the flaps closed, at the loss of one ft/lb of torque. The picture below of the screen
shows the max power run with the flaps closed diverting through the baffled box, at 340hp it's not quite a standard 993

These of course were just back to back tests with no adjustments between systems which could optomise things better, but
fascinating to see how little difference open/closed made in terms of power.

We finished off the tests with a run with my original megaphones on, fantastic sound but a power loss of nearly 25hp........
so they've gone in the bin! At the end of the day back pressures a wonderful thing.....

964RS · Post by **964RS** » Thu Dec 02, 2010 5:07 pm

Great result

So when is this car going to be finished then????

squirdan · Post by **squirdan** » Thu Dec 02, 2010 5:09 pm

hi mike. this looks a brilliant solution. I shall definitely be in touch with Neil.

by the way, Tuthills have just test fitted your wings and they fit perfectly.

hope all well. Dan

Mike · Post by **Mike** » Thu Dec 02, 2010 5:38 pm

964RS wrote:Great result
So when is this car going to be finished then????

Hi Jason, thanks for the interest. I'm hoping to update the build thread shortly with the latest developments, but basically the car has gone off to the bodyshop
to have the wings re-shaped from the 930 turbo arches to the profile taken from a real 73 RSR. Unfortunately work at the bodyshop has been held up due to
their work load so a bit behind at the moment, but they should be starting soon and can update then.

964RS · Post by **964RS** » Thu Dec 02, 2010 5:45 pm

cool cant wait to see the finished car

911hillclimber · Post by **911hillclimber** » Thu Dec 02, 2010 6:10 pm

Quality thread.

I have a 2 in 3 out silencer which i cap the middle two outlets for dawn runs to the hillclimbs, and un-cap for the race up- hill for the noise (112 dB).
No performance gain but FAR better sound track.

Oddly, tick-over quickens with the system open.

Silencer is well cream-crackered now so looking for new one with2 in 3 out.(got your pm Mike)
Dansk 2in 2 out is too noisey i think for ther road?

Most interesting.

Graham.