Need super quiet 911 exhaust for SWB

Any technical issue relating to Motorsport Porsches

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rhd racer
DDK 1st, 2nd and 3rd for me!
Posts: 2030
Joined: Wed Jun 23, 2004 9:47 pm
Location: Nottinghamshire

Post by rhd racer »

Hi Andrew

Some of the 911 guys have had similar issues in our Championship. I assume you do the noise test with your foot on the clutch, to cut any chatter from the gearbox? That is said to help a bit...It is also frustrating that every test seems to deliver a different result, I am not sure how well calibrated the equipment is. Mine has been tested anywhere between 98 and 105MB with a standard stainless silencer! It doesn't help when you are tested in a queue either... Incidentally, the quieter ones are normally when tested on the grass.

Other than that;
- Have someone take the silencer apart and carefully apply some exhaust wadding (clearly someone that knows what they are doing so there is no power loss). There is a fair bit of room in there (they are very basic, simple chambers). I am sure this would get you down a bit.
- Have an SC style system made, with a pre silencer at the back of the engine and a standard rear silencer (I think this would require a 'one in one out', rather than a 'two in one out' that you have now.

I have some other ideas if this isn't what you want to do - give me a bell and catch up if you have time.

Cheers
Wayne
93 964 C2
99 Boxster 2.5 > 2.7 hill climber

71 914/6 3.0 - gone

'You see Paul, hill climbing is like making love to a beautiful woman. You get your motor running, check your fluids, hang on tight and WHOA..30 seconds later it's all over!' Swiss Tony
amallagh
I need to get out more!
Posts: 3081
Joined: Wed Dec 06, 2006 11:27 pm
Location: Cheshire, England

Post by amallagh »

Thanks Jerry,
I'll give BTB a call next week to see what they can offer.
Regards
Andrew
Histrally wrote:Hi Andrew,
Just seen your post having been away.
I suggest you try BTB Exhaust in Daventry.
http://www.btbexhausts.co.uk/exhausts/porsche.asp
I have used them for one off for my previous rally car. They may make the Prefab exhaust? They are certainly capable of modifying an existing design to fit.
My 2.7 is marginal through a noise test and uses a standard silencer. I do know that stainless steel tends to resonate more as it uses thinner material and will be noisier. I wondered about going to a twin outlet as they can only measure one pipe at a time. Pay attention to your inlet filtration as induction noise on the Porsche is in the wrong place. I guess you are on carbs compared to my fuel injection.
All else fails run the engine at reduced revs through scruitineering!!!
Let me know how you get on.
Jerry
'72 914/6GT (first love!)
'66 SWB 911 (now sold but still prostituting itself as a rally car rental for HERO)
'73 911 2.7RS
'73 911 2.8RSR (some time in the near future)
'67 911R 2.0 twin plug (sometime, maybe, never?)
996TT (sold)
997TT (sold)
amallagh
I need to get out more!
Posts: 3081
Joined: Wed Dec 06, 2006 11:27 pm
Location: Cheshire, England

Post by amallagh »

Hi Wayne,
hope you are well and the sprint season is going to plan ?
I do all the normal things. Clutch in, lie about the revs, etc.
A modified 911 box with some replaceable packing sounds like a good idea. Sounds like BTB might be an option if they used to make the Prepfab ones.
Regards
Andrew
rhd racer wrote:Hi Andrew

Some of the 911 guys have had similar issues in our Championship. I assume you do the noise test with your foot on the clutch, to cut any chatter from the gearbox? That is said to help a bit...It is also frustrating that every test seems to deliver a different result, I am not sure how well calibrated the equipment is. Mine has been tested anywhere between 98 and 105MB with a standard stainless silencer! It doesn't help when you are tested in a queue either... Incidentally, the quieter ones are normally when tested on the grass.

Other than that;
- Have someone take the silencer apart and carefully apply some exhaust wadding (clearly someone that knows what they are doing so there is no power loss). There is a fair bit of room in there (they are very basic, simple chambers). I am sure this would get you down a bit.
- Have an SC style system made, with a pre silencer at the back of the engine and a standard rear silencer (I think this would require a 'one in one out', rather than a 'two in one out' that you have now.

I have some other ideas if this isn't what you want to do - give me a bell and catch up if you have time.

Cheers
Wayne
'72 914/6GT (first love!)
'66 SWB 911 (now sold but still prostituting itself as a rally car rental for HERO)
'73 911 2.7RS
'73 911 2.8RSR (some time in the near future)
'67 911R 2.0 twin plug (sometime, maybe, never?)
996TT (sold)
997TT (sold)
rhd racer
DDK 1st, 2nd and 3rd for me!
Posts: 2030
Joined: Wed Jun 23, 2004 9:47 pm
Location: Nottinghamshire

Post by rhd racer »

Hi Andrew

Yes - have a 100% reliability record....by non-participation! For good reasons though, have just finished an extension over the garage so the car was in storage for 6 months, and only got back last month.
We have also just had another little girl, 3 weeks ago in fact, so it has curbed activities for a bit!

I hope to do 3 or 4 rounds at the end of the season, so I don't get too rusty. You have a pm,

Cheers
Wayne
93 964 C2
99 Boxster 2.5 > 2.7 hill climber

71 914/6 3.0 - gone

'You see Paul, hill climbing is like making love to a beautiful woman. You get your motor running, check your fluids, hang on tight and WHOA..30 seconds later it's all over!' Swiss Tony
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