FAO those worrying about sports exhaust & track

[shnozz]

I have got a loaned pair of ACT silencers that I tried out over the weekend.

Oh my god - unbelievable. Make the snarling growl of the exhaust into a tame thudding V8. The db reduction is amazing and I am surprised its considered as low as 5 - 10 dbs that I have read before. I am confident that you would be ok on a track day with these fitted, although thats not official. I did try to get it measured with and without at Goodwood and headed down there only to find it deserted last Sunday.

[Corin Denton]

I have a pair of bolt on silencers if anybody needs to use them for a weekend?

[my 350i]

Thanks Shnozz
I may well get the stuffing knocked out of my box then.
Each time the db has been measured on my 500 it has been around 97 - 98. As I already have a pair of ACT silencers it sounds as if it will be ok. Wont be a problem at Goodwood on monday as its a 105db day. Just have to remember the ear plugs I reckon
Dave

[ian8542]

Just out of interest, has anybody had a rolling road dyno done to show the before and after scenarios in fitting noise cancelling ad-ons?

[chimhunter]

my 350i said:

Thanks Shnozz I may well get the stuffing knocked out of my box then. Each time the db has been measured on my 500 it has been around 97 - 98. As I already have a pair of ACT silencers it sounds as if it will be ok. Wont be a problem at Goodwood on monday as its a 105db day. Just have to remember the ear plugs I reckon Dave

Dave, any change you could get yours measured with and without at Goodwood? I've had the conversion done and I've got the ACT cans. I need to check the noise level with the cans on before I book the next track day, so a pointer to the dB level would be great.

Ta,

Rob

[deeen]

ian8542 said:

Just out of interest, has anybody had a rolling road dyno done to show the before and after scenarios in fitting noise cancelling ad-ons?

No, but I would assume the ACT design does not affect the power much, as it is still Straight-through, although with reduced bore. Good point though - I should be at Austec before Christmas so maybe I can get them to try it.

Shnozz - told you so! Na na na-na na!

[2 sheds]

We measured reduction of 7.5 dba on a 500 Chimaera, with our cans, some get more some less, power loss is minimal assuming that you aren't Griffnonoski

p.s thanks for the comments

Tim

[my 350i]

chimhunter said:

my 350i said: Thanks Shnozz I may well get the stuffing knocked out of my box then. Each time the db has been measured on my 500 it has been around 97 - 98. As I already have a pair of ACT silencers it sounds as if it will be ok. Wont be a problem at Goodwood on monday as its a 105db day. Just have to remember the ear plugs I reckon Dave Dave, any change you could get yours measured with and without at Goodwood? I've had the conversion done and I've got the ACT cans. I need to check the noise level with the cans on before I book the next track day, so a pointer to the dB level would be great. Ta, Rob

Rob
No problem, i`ll take them with me and get it checked, always helpful at Goodwood i`ve found. A mates Cerb was reduced by around 7db so I would guess much the same

[shnozz]

deeen said:

ian8542 said: Just out of interest, has anybody had a rolling road dyno done to show the before and after scenarios in fitting noise cancelling ad-ons? No, but I would assume the ACT design does not affect the power much, as it is still Straight-through, although with reduced bore. Good point though - I should be at Austec before Christmas so maybe I can get them to try it. Shnozz - told you so! Na na na-na na!

I must say, from the db figures I had seen I just couldnt understand how it would be "that" clear cut. Its incredible the difference it made!

[cuzza]

shnozz said:

I must say, from the db figures I had seen I just couldnt understand how it would be "that" clear cut. Its incredible the difference it made!

Bear in mind that decibels are not linear, so the difference between 100 and 105 is much more than the difference between 95 and 100 and so would be more noticeable.

[shnozz]

cuzza said:

shnozz said: I must say, from the db figures I had seen I just couldnt understand how it would be "that" clear cut. Its incredible the difference it made! Bear in mind that decibels are not linear, so the difference between 100 and 105 is much more than the difference between 95 and 100 and so would be more noticeable.

yep, I think thats why I wasnt confident of the difference until I tried it - now I appreciate how the db things work (sort of!)

[chimhunter]

my 350i said:

Rob No problem, i`ll take them with me and get it checked, always helpful at Goodwood i`ve found. A mates Cerb was reduced by around 7db so I would guess much the same

Top stuff mate. Let me know how it goes.

Ta,

Rob

[my 350i]

Top day at Goodwood yesterday despite wet start and remaining damp around St Mary`s all day, led to one or two "moments" for a few. My best effort was to exit the chicane with a lot of opposite lock on the first quick lap
Tested for noise twice, first with standard system - 96db then bolted on ACT extras, started up and thought it had stalled as there was no noise . 85db with them on. I can`t see a problem with sports exhaust then even on a 98db day but i think there may be a fair bit of power loss due to the restricted bore size.

[bassfiend]

shnozz said:

I have got a loaned pair of ACT silencers that I tried out over the weekend. Oh my god - unbelievable. Make the snarling growl of the exhaust into a tame thudding V8. The db reduction is amazing and I am surprised its considered as low as 5 - 10 dbs that I have read before. I am confident that you would be ok on a track day with these fitted, although thats not official. I did try to get it measured with and without at Goodwood and headed down there only to find it deserted last Sunday.

I have an SPL meter if you want to measure the difference...

Phil

[chimhunter]

Cheers for letting us know. I've put the ACT cans on mine when on a long motorway treck (5 hours) and its spooky how quiet the car gets...