Exhaust noise ratings on logbook

[sonnenschein3000]

What do they mean exactly?

e.g. if it says 74dB @ 3750rpm, does this mean that I will be commiting an offence if I put an aftermarket backbox on that is louder than this at the specified revs (and declared to insurance of course)?

If so what offence, and whats the likely punishment?

[Red Devil]

The 74dB you mention comes from Council Directive 92/97/EEC of 10 November 1992 - http://eur-lex.europa.eu/legal-content/en/ALL/?uri...

It depends on how much more noise your aftermarket backbox produces as it is that which is likely to be the trigger for police interest,

Found this. The only way is Essex.

Non-endorseable FPN - https://www.essex.police.uk/getmedia/5a4aaf2f-105f...
The 80 dB figure appears to be from the earlier Council Directive 77/212/EEC of 8 March 1977 - http://eur-lex.europa.eu/legal-content/EN/TXT/?uri...
It's considerably more generous than the log book figure (dB is not linear).

I have no idea whether the limits in the above procedure have been changed or whether other constabularies use the same/different ones.

If you're not in the UK all bets are off, as I know nothing about the national legislation of other countries

[ging84]

Are you sure it doesn't say drive by of 74 ?
The rpm should be for the stationary value, the drive by is not done at a specific rpm as the speed increases during the test
74 is incredibly low for a static test

[Red Devil]

The 74dB figure is the drive by test figure in the 1992 Directive. The Method of Measurement in specified in Section 5.2.2.4.

ISO 5130:2007 which Essex police are using is for a static test - http://www.iso.org/iso/catalogue_detail.htm?csnumb...
The question then arises is whether a static test is prescribed anywhere in domestic legislation.
The table in C&U Regs 1986 Section 55 links specifically to the Directives so I'm not convinced that it is.
Am quite willing to be proved wrong though.

I'm struggling to find any mention of a static test in the Directives but it's hard to keep track of them all.
Brussels does love churning out mountains of verbiage.

Once a FPN is issued the the only alternative to accepting it is a challenge in court.
Whether you will be able to convince the Magistrates is something else.
Most are not well versed in the law and rely on the Clerk to advise them.
You'll need to have all your ducks in a row and then some.

See this thread - http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Norfolk Police screwed up the test so the doughty PHer was given a conditional discharge.*

 * Jump to page 12

Edited by Red Devil on Tuesday 20th December 23:19

[sonnenschein3000]

I was using 74 as an example. My logbook is at office, but i'm sure it said 74 or something like that.

I think +3dB is double. 80dB is quite fair then I think.

[ging84]

Red Devil said:

Found this. The only way is Essex.

Non-endorseable FPN - https://www.essex.police.uk/getmedia/5a4aaf2f-105f...

This is complete garbage, seems to mirror what norfolk were doing in that other thread, it demonstrates the police have absolutely no idea what they are doing with regard to noise testing.

They have made out that they are allowing a fairly generous margin, but actually almost all performance cars would be considered illegal and at least meet thier threshold for a verbal warning the day they leave the factory.

ISO 5130:2007 is not really suitable for the purpose of testing, because the EU type approval don't use it, they use the process for measuring the sound level of a stationary vehicle outlined in 5.2.3 in the 1992 Directive (which is largely the same, but the iso much more indepth).
You can't compare difference references at difference rpms and simply assume the higher rpm will always be louder, nor can you assume that 50% of the value on the tacho will be lower than 75% of the rated engine speed.

If they used the procedure from the type approval then it would be a simple case of look up U.2 on the V5, test it at the specified rpm, and compare the value to U.1, if it's higher by more than 1dB(A) then it's a fail (which could get a warning or fine depending on what thresholds they want to offer), unless the owner can produce a type approval certificate for a type approved exhaust with a higher reference value and a description that matches that which installed on the car.

I really don't understand how they can get it so badly wrong, I know one issue is that a lot of v5s particularly on older vehicles don't have a stationary reference value, but in these cases it would seem reasonable to go on the bases that are used to IVA, which is 99dB(A) at 75% of the rated engine speed, or 2/3 of the max engine speed.
Most of the genuinely noisy cars that go around terrorising council estates would still fail that convincingly, and of the ones that don't they still have the power to issue a fine drivers making excessive noise under the other regulation referenced; Avoidance of excessive noise – Reg. 97 The Road Vehicles (Construction & Use) Regulations 1986

Just as an example of why this procedure a crock of st, this is my wife's car, a 2005 mini cooper S, fairly loud, but by no means the loudest car on the road.




88dB(A) at 4500 rpm, so with the silencer unmodified in perfect condition could potentially be expected to test at up to 90-91dB(A) at 4500rpm in any single test on a bad day.
To complicate things more it's had a manufacturer approved and type approved JCW tuning kit, which includes a louder (but not necessarily more noisy) exhaust.

The tacho goes to 8K rpm (the rated engine speed is 6k) Essex police would test it at 4000 rpm. It most certainly would be above 80, so as far as they are concerned an offence is committed and a warning would be issued, if thier testing environment was suitable it aught to not be above 90 so perhaps no fine, but would certainly be close.
But according to that document they seem to believe they are able to deviate from the procedure specified in the ISO (despite it being thier choice to use it) and still produce a valid result because they have lowered the rpm and are rounding down (the type approval procedure not only rounds down it also deducts 1dB(A) from the measured value). So they may not use a suitable testing environment, and without a guarantee of a 3m clear space around the vehicle i'd have no confidence that it would test at less than 90dB(A) even when tested at 4k rpm.