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?
My 964C2 runs a catbypass and a straight through exhaust system that weighs almost 15kgs less than factory exhaust that gave a read out of 99db today.
It was custom made at Blueflame , Skemersdale for £300.
I don't know whether it gives a performance gain or not but last time the car was dyno'd it peaked at 303hp so I'm guessing it's not too restrictive
It was custom made at Blueflame , Skemersdale for £300.
I don't know whether it gives a performance gain or not but last time the car was dyno'd it peaked at 303hp so I'm guessing it's not too restrictive
will964 said:
Melv, the picture with the noise meter was for demo purposes only you little comedian.
911 Wise, I wish I could get 315bhp with a cat by pass and filter, i would be a vey happy boy. i'm afraid this includes motec, bigger injectors, exhaust and air filter mods.
Sorry old boy..
Will
911 Wise, I wish I could get 315bhp with a cat by pass and filter, i would be a vey happy boy. i'm afraid this includes motec, bigger injectors, exhaust and air filter mods.
Sorry old boy..
Will
I thought it sounded optimistic. Still 315bhp still impressive in whats a fairly light car, I bet there's not a lot around to show it up.
911wise said:
will964 said:
911 Wise, I wish I could get 315bhp with a cat by pass and filter, i would be a vey happy boy. i'm afraid this includes motec, bigger injectors, exhaust and air filter mods.
Sorry old boy..
Will
I thought it sounded optimistic. Still 315bhp still impressive in whats a fairly light car, I bet there's not a lot around to show it up.
Optimistic , and how!! 320ish here with revised ECU, cams, hot film system.....and engine rebuild!!
Thanks to Will I was able to try out the new exhaust tip at Bedford yesterday.
On the initial static test my car measured 108db (exactly what I expected it would) using the factory tip. I then fitted the silencer tip and had the car re-tested, this time it measured 105db. Clearly this wasn't quite as big a reduction as Will experienced on his own car, however it is extremely difficult to hold a steady 4,500rpm in my car and I think that the second reading spiked at closer to 5,000rpm. Nevertheless this is still a significant reduction, and even at 105db will allow the car to get onto pretty much every track, which it would not have done before.
The most significant effect was, however, on the all-important drive-by test. My car has consistantly failed the drive-by test at Bedford to the point where the previous owner stopped even bothering to go there any more. The drive-by limit is 87.5db, and on two runs my car measured 83.1db and 83.8db.
Bedford have instigated a new noise test procedure whereby if your car fails the static test then you have to hand over the keys to one of Bedford's instructors and they conduct the drive-by test i.e. gone are the days when you can just hope to get by by short-shifting at the microphones. If you don't get past the drive-by test with an instructor driving then it's game over before you've even started, you just won't be let on track at all.
Having passed the test my red sticker was swapped for a green one and I was able to drive all day flat-out, not having to worry about tripping the noise meters.
In short the tip does exactly what it is meant to, it reduced the noise to a level that allowed me on circuit and meant I could give it full beans all day. There was no discernable loss of power and the tip took no more than five minutes to fit.
When you consider that these tips cost about the same as a track-day I think it's a bit of a no-brainer......
Jamie
On the initial static test my car measured 108db (exactly what I expected it would) using the factory tip. I then fitted the silencer tip and had the car re-tested, this time it measured 105db. Clearly this wasn't quite as big a reduction as Will experienced on his own car, however it is extremely difficult to hold a steady 4,500rpm in my car and I think that the second reading spiked at closer to 5,000rpm. Nevertheless this is still a significant reduction, and even at 105db will allow the car to get onto pretty much every track, which it would not have done before.
The most significant effect was, however, on the all-important drive-by test. My car has consistantly failed the drive-by test at Bedford to the point where the previous owner stopped even bothering to go there any more. The drive-by limit is 87.5db, and on two runs my car measured 83.1db and 83.8db.
Bedford have instigated a new noise test procedure whereby if your car fails the static test then you have to hand over the keys to one of Bedford's instructors and they conduct the drive-by test i.e. gone are the days when you can just hope to get by by short-shifting at the microphones. If you don't get past the drive-by test with an instructor driving then it's game over before you've even started, you just won't be let on track at all.
Having passed the test my red sticker was swapped for a green one and I was able to drive all day flat-out, not having to worry about tripping the noise meters.
In short the tip does exactly what it is meant to, it reduced the noise to a level that allowed me on circuit and meant I could give it full beans all day. There was no discernable loss of power and the tip took no more than five minutes to fit.
When you consider that these tips cost about the same as a track-day I think it's a bit of a no-brainer......
Jamie
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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