Exhaust vs Carb setup

[Philippe Giroulle]

I just had my xflow sprint engine upgraded to supersprint+ configurations and am now running it in. In my opinion the engine sounds quite louder and I'm afraid it will be too loud for trackdays. So, I will probably need to upgrade the exhaust as well (actually standard rear exit exhaust).

Do I need to replace the exhaust before heading for rolling road session to adjust the Webers or does this not influence the carbs setup?

Also, what type of exhaust do you recommend? Techcraft, or others?

 

Thanks,

 

Philippe

[bstark]

Can't help a great deal, other than to say my car went through the same engine upgrade when I bought it 3 years ago - again, with the standard rear exit exhaust.

 

I don't have any problems on trackdays at Brands Hatch (105dB) but I wouldn't even attempt a 'quiet' day with this setup. Sounds good, though, doesn't it! 😬

 

BTW, the carb setup does make quite a difference to the level of (and tunefulness) of the noise made, if mine is anything to go by...

 

Bob Stark

Supersprinter

 

Edited by - bstark on 6 Feb 2004 13:09:00

[mikes]

Philippe,

I had this conversation with Roger King just the other day - and I also have one of his supersprint plus xflows and rear exit exhaust - not many of us left!

Anyway, he said that if you change the exhaust you will definitely have to change the carb settings etc - so I would have thought it should be a new exhaust first.

I thought I would keep my rear exit exhaust until it starts to fall apart (again) but then it will have to be one of the big ones I think

Mike

[Graham Sewell]

I have a rear exit exhaust as well - so more of us left. Time to start another register along with xflow and clamshells.

 

Low tech luddite - xflow and proud!

[puremalt]

you can't see the flames as well as a side exhaust set up 😬

 

Excellent!

[Ferrino]

I think it would definitely be recommended to go to the RR after changing exhaust.

[Allan Haighton]

Philippe... be careful with changing your exhaust from 4-2-1 rear exit to 4-1 side exit.

I went down the same road and put a Techcraft system on. Big reduction in measured exhaust noise outside the car

BUT - big increase in noise in the cockpit at around 3000 rpm or so - so much so that I got ringing in my ears after every long drive. Result - no long drives. ☹️. Even ear defenders (top spec Peltors) didn't get rid of the problem.

After much fiddling about, I'm pretty sure that the cause is resonance of the 4-1 exhaust. I put the original 4-2-1 system back on and immediately the 3000 rpm peak noise disappeared. The resonance has dropped in frequency (to about 2000 rpm - as expected for a longer total exhaust length) but since I don't drive around much at this engine speed it's un-noticeable - which is why it was never a problem before. (Also the rear exit is further away from the driver).

Caterham 'think' they can provide a 4-1 rear exit exhaust using bits that were once used on specialist applications, but I haven't taken them up on this yet.

 

 

Question for RK

I haven' t noticed much change in driving perforamce on the road on changing back to 4-2-1, so I haven't yet thought about going back on a rolling road. Should I expect to use bigger or smaller jets that with a 4-1?

[Philippe Giroulle]

Thanks Allan for your comments.

 

Can anybody tell me what dB results are to be obtained with a Supersprint Plus and a standard rear exit exhaust.

I haven't checked through the local authorities, but it wouldn't surprise me that a side exit exhaust would NOT be allowed in Belgium.

[mikes]

I always remember what the result is when I have been tested - but nearly always forget!

Mine is a 1989 exhaust so it may be a little knacked by now, but I do know I always fail at Goodwood - 98dB limit I think, and I seem to recall that it was about 104 or similar at one of the sprints. I have not failed anywhere else anyway so it presumably is reproducibly below 105dB (if that is the normal upper track noise limit).

Graham - I too have clamshells *smile*

Mike