964/RS Too loud for some circuits? I might have the answer..
Discussion
After the experience of being thrown off circuits like Goodwood, Donnington, and Bedford because of excessive noise from my 964 I decided to do something about it.
My modified 964 C2 runs with a cat-bypass pipe and no centre silencer that runs behind the rear bumper. The large rear silencer box is still in place.
The car was measured at Bedford Aerodrome (which is a noise sensitive circuit that has microphones around the circuit) at 106db static test, and over 100db drive by.
I searched the market place for a suitable silencer for the 964 and found nothing suitable. They either looked too restrictive or were physically too large and would foul the bumper.
I applied some motorcycle performance exhaust theory of a straight through non restrictive design. I approached MHP exhausts in Surrey to design a prototype.
The brief was to decrease noise without significantly effecting power, or damaging the engine. And obviously it had to look neat.
The result is a 102mm stainless steel slash cut exhaust tip with a completely serviceable inner silencer. This can be removed as it is held in neatly by one 8mm bolt.
The tip is secured by one knuckle strap and 13mm mm nut and bolt. As long as this is not rusted solid it is a five minute job to remove the standard tip and replace it with the MHP tip.
The silencer tip is made from stainless steel internals, including a s/steel double skin conical perforated core, s/steel wire wool, and exhaust wadding.
The static noise test @ Bedford showed 99.9db, and I have yet to get results on the driveby test. Where I would normally back off past the microphones, I was flat out all day without tripping the noise meter.
The car was run on the Ninemeister dyno. The first run produced 315bhp without the silencer, and 313bhp with it in place.
A total loss of 2bhp, and no negative effect on the torque figure.
The tip can be left in situ, or removed after the trackday. I have been doing normal road driving with the silencer in place for the past two months with no side apparent side effects.
Anyone interested in this product drop me a message to normster@talktalk.net for dyno graphs and full photographs.
If there is enough interest MHP will start producing these.
My modified 964 C2 runs with a cat-bypass pipe and no centre silencer that runs behind the rear bumper. The large rear silencer box is still in place.
The car was measured at Bedford Aerodrome (which is a noise sensitive circuit that has microphones around the circuit) at 106db static test, and over 100db drive by.
I searched the market place for a suitable silencer for the 964 and found nothing suitable. They either looked too restrictive or were physically too large and would foul the bumper.
I applied some motorcycle performance exhaust theory of a straight through non restrictive design. I approached MHP exhausts in Surrey to design a prototype.
The brief was to decrease noise without significantly effecting power, or damaging the engine. And obviously it had to look neat.
The result is a 102mm stainless steel slash cut exhaust tip with a completely serviceable inner silencer. This can be removed as it is held in neatly by one 8mm bolt.
The tip is secured by one knuckle strap and 13mm mm nut and bolt. As long as this is not rusted solid it is a five minute job to remove the standard tip and replace it with the MHP tip.
The silencer tip is made from stainless steel internals, including a s/steel double skin conical perforated core, s/steel wire wool, and exhaust wadding.
The static noise test @ Bedford showed 99.9db, and I have yet to get results on the driveby test. Where I would normally back off past the microphones, I was flat out all day without tripping the noise meter.
The car was run on the Ninemeister dyno. The first run produced 315bhp without the silencer, and 313bhp with it in place.
A total loss of 2bhp, and no negative effect on the torque figure.
The tip can be left in situ, or removed after the trackday. I have been doing normal road driving with the silencer in place for the past two months with no side apparent side effects.
Anyone interested in this product drop me a message to normster@talktalk.net for dyno graphs and full photographs.
If there is enough interest MHP will start producing these.
Thanks for all the interest, if i could work out how to post the pictures on here then I would.. at the moment MHP will concentrate on the 964 for now. keep the e-mails coming by the way as the more orders the better.
i will be at Oulton Park RS day on 16th March with a few silencers. I will be the one whispering by at Cascades!!!
The price for this piece of kit is 199.00 pounds which to me represents good value. The cost of being booted off a circuit for a noisy car after you have paid your monies anyone?
i will be at Oulton Park RS day on 16th March with a few silencers. I will be the one whispering by at Cascades!!!
The price for this piece of kit is 199.00 pounds which to me represents good value. The cost of being booted off a circuit for a noisy car after you have paid your monies anyone?
Melv , would love to know how you can get 320bhp out of the standard injectors; ) if they are indeed standard?
They must be, as the original motronic is not compatable with after market injectors.... and the cams are of limited value if the additional fuel is not being supplied to the combustion chamber, or am i talking out of my silenced exhaust pipe!!!!
They must be, as the original motronic is not compatable with after market injectors.... and the cams are of limited value if the additional fuel is not being supplied to the combustion chamber, or am i talking out of my silenced exhaust pipe!!!!
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