Sports exhaust on a Griff
Discussion
DECIBELS
A tenth of a Bel?
The decibel (abbreviated dB) must be the most misunderstood measurement since the cubit. Although the term decibel always means the same thing, decibels may be calculated in several ways, and there are many confusing explanations of what they are.
The decibel is not a unit in the sense that a foot or a dyne is. Dynes and feet are defined quantities of force and distance. (You can go to the National Bureau of Standards and look at a foot or a dyne if you want to. They never change.) A decibel is a RELATIONSHIP between two values of POWER.
Decibels are designed for talking about numbers of greatly different magnitude, such as 23 vs. 4,700,000,000,000. With such vast differences between the numbers, the most difficult problem is getting the number of zeros right. We could use scientific notation, but a comparison between 2.3 X 10 and 4.7 X 10 to the 12th is still awkward. For convenience, we find the RATIO between the two numbers and convert that into a logarithm. This gives a number like 11.3. As long as we are going for simplicity, we might as well get rid of the decimal, so we multiply the number times ten. If we measured one value as 23 hp and another as 4.7 trillon hp, we say that one is 113dB greater than the other.
The usefulness of all this becomes becomes apparent when we think about how the ear perceives loudness. First of all, the ear is very sensitive. The softest audible sound has a power of about 0.000000000001 watt/sq. meter and the threshold of pain is around 1 watt/sq. meter, giving a total range of 120dB. In the second place, our judgment of relative levels of loudness is somewhat logarithmic. If a sound has 10 times the power of a reference (10dB) we hear it as twice as loud. If we merely double the power (3dB), the difference will be just noticeable
Like to say I wrote this.....but found it on the web.
So 10db is twice as loud?
A tenth of a Bel?
The decibel (abbreviated dB) must be the most misunderstood measurement since the cubit. Although the term decibel always means the same thing, decibels may be calculated in several ways, and there are many confusing explanations of what they are.
The decibel is not a unit in the sense that a foot or a dyne is. Dynes and feet are defined quantities of force and distance. (You can go to the National Bureau of Standards and look at a foot or a dyne if you want to. They never change.) A decibel is a RELATIONSHIP between two values of POWER.
Decibels are designed for talking about numbers of greatly different magnitude, such as 23 vs. 4,700,000,000,000. With such vast differences between the numbers, the most difficult problem is getting the number of zeros right. We could use scientific notation, but a comparison between 2.3 X 10 and 4.7 X 10 to the 12th is still awkward. For convenience, we find the RATIO between the two numbers and convert that into a logarithm. This gives a number like 11.3. As long as we are going for simplicity, we might as well get rid of the decimal, so we multiply the number times ten. If we measured one value as 23 hp and another as 4.7 trillon hp, we say that one is 113dB greater than the other.
The usefulness of all this becomes becomes apparent when we think about how the ear perceives loudness. First of all, the ear is very sensitive. The softest audible sound has a power of about 0.000000000001 watt/sq. meter and the threshold of pain is around 1 watt/sq. meter, giving a total range of 120dB. In the second place, our judgment of relative levels of loudness is somewhat logarithmic. If a sound has 10 times the power of a reference (10dB) we hear it as twice as loud. If we merely double the power (3dB), the difference will be just noticeable
Like to say I wrote this.....but found it on the web.
So 10db is twice as loud?
] 
So after all this talk, whats the best option/combo for a Griff sports exhaust. I have a std exhaust at the moment, but do not know wether to get one made from scratch/Have the std one canabilised/remove the cat?/What power gains for each scenario if any?
Would appreciate any advice/knowledge as like to have this done to enjoy the summer months even more.....
Would appreciate any advice/knowledge as like to have this done to enjoy the summer months even more.....
quote:
Heh Dude - you and me the same! Are we to gadge from this that there is NO power advantage with a sports exhaust??
With a normal sports exhaust you won;t get anymore power, however if you decat it and change the chip it might give you a couple more bhp and low rpm running will be a bit smoother
I bought a new exhaust from Zertec a couple of years back -- the Chimaera on Zertec's Web site is mine as it was the first Chimaera they did. Not the cheapest but worth every penny involving replacement almost of the entire system downstream of the cat. Sounds fruity, burbly, I even get muffled pops and bangs...you know it makes sense!
My Griff 500 (still had all std Cats) has had all the packing removed from the silencers (i.e. 'sports' exhuast).
Did a sprint this w/e and the noise test registered 103 dB. I have a bolt-on siliencer (from Tim Lamont at ACP Products) which drops this to around 97 dB - and though regulations for spirnts (rather than track days) will not allow it's fitment, it's good for most noise sensitive track days.
An inmportant point to remember about exhuasts & noise levels is that standard, silenced exhausts will gradually get louder over time as the packing deteriorates.
Did a sprint this w/e and the noise test registered 103 dB. I have a bolt-on siliencer (from Tim Lamont at ACP Products) which drops this to around 97 dB - and though regulations for spirnts (rather than track days) will not allow it's fitment, it's good for most noise sensitive track days.
An inmportant point to remember about exhuasts & noise levels is that standard, silenced exhausts will gradually get louder over time as the packing deteriorates.
quote:
Heh Dude - you and me the same! Are we to gadge from this that there is NO power advantage with a sports exhaust??
....and still the great masses are reluctant in coming forward to tell us the answer!!!!!
Must be like when I owned a K1200RS BMW ("sports"-bike brick). The local dealer was doing a "good" deal on some Austrian made exhaust (Remus, I think) that sounded good. On trying their demo I concluded that there was a definite performance gain.
Unfortunately it was that because it sounded so good you wanted to twist the throttle more - ergo you went faster, accelerated at every available opportunity (and plenty of non-opportunities!!), and increased your petrol consumption........
Didn't stop me from wanting one though
I couldn't tell you if there are perfomance gains - I've only had the Griff a week and its always had the sports exhaust.
I would think there would be performance gains but these may be so minimal that you probably would not notice.
Except for the noise difference of course, which makes you think you're going faster!!
I would think there would be performance gains but these may be so minimal that you probably would not notice.
Except for the noise difference of course, which makes you think you're going faster!!
I'll be back in a minute - I'm just popping off to paint some stripes down the side and bolt a tea tray to the boot lid to get that "go faster feeling" 
So in actual fact there is nothing "sporty" about my pipes at all - just "noisey"
Anyone got some silencers for sale then? I remember seeing an ad' in Sprint from Gloucester for about £140 but not sure they were for a 500. If you are here I will be interested. PLEASE REMEMBER THAT THIS IS JUST FOR THE TRACK, I DON'T CARE ANY OTHER TIME ABOUT THE FANTASTIC SOUNDS EMANATING FROM MY REAR!
>> Edited by 500 GRF on Wednesday 10th April 14:27
So in actual fact there is nothing "sporty" about my pipes at all - just "noisey"
Anyone got some silencers for sale then? I remember seeing an ad' in Sprint from Gloucester for about £140 but not sure they were for a 500. If you are here I will be interested. PLEASE REMEMBER THAT THIS IS JUST FOR THE TRACK, I DON'T CARE ANY OTHER TIME ABOUT THE FANTASTIC SOUNDS EMANATING FROM MY REAR!
>> Edited by 500 GRF on Wednesday 10th April 14:27
quote:Martin, take a look at Merlin Motorsports www.merlinmotorsport.co.uk/catalogue/exhausts.htm they sell add-on mufflers for £44.50 each plus VAT. I haven't been noise tested yet with them on but they reckon they reduce the level by 5db or more. Rich...
Anyone got some silencers for sale then? I remember seeing an ad' in Sprint from Gloucester for about £140 but not sure they were for a 500. ...PLEASE REMEMBER THAT THIS IS JUST FOR THE TRACK, I DON'T CARE ANY OTHER TIME ABOUT THE FANTASTIC SOUNDS EMANATING FROM MY REAR!
quote:
I remember seeing an ad' in Sprint from Gloucester for about £140 but not sure they were for a 500.
So happens I have my copy here. Having wiped it down I see the ad you mean on page 42 - definitely says can be used on 500. Will e-mail number off list in case you haven't got it to hand.......
quote:
I'll be back in a minute - I'm just popping off to paint some stripes down the side and bolt a tea tray to the boot lid to get that "go faster feeling"
You'll be wanting a couple of cans of red, some white for a nice angled stripe, a new perm and some squeally-tyre sound affects............you playing Starsky? or Crotch?
Nothing wrong with big stripes and tea-trays - after all, TVR has been doing it for years!
I mean - The Taimar and SEAC must be some of the most OTT examples in their respective fields
I mean - The Taimar and SEAC must be some of the most OTT examples in their respective fields
quote:
I'll be back in a minute - I'm just popping off to paint some stripes down the side and bolt a tea tray to the boot lid to get that "go faster feeling"
Thames Valley Racetech are opening up my exhaust today and replacing some of the silencer packing which will have been removed to make it a 'sports exhaust'.
Hopefully this will bring the car closer to being acceptable for track days, remove some of the more obtrusive popping and banging and restore the V8 burble rather than the exhaust's 'WAAAAHH'.
They fired up Wayne Phelan's race Tuscan whilst I was there. Mine is noisier than the race car at the moment!!
Hopefully this will bring the car closer to being acceptable for track days, remove some of the more obtrusive popping and banging and restore the V8 burble rather than the exhaust's 'WAAAAHH'.
They fired up Wayne Phelan's race Tuscan whilst I was there. Mine is noisier than the race car at the moment!!
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