Noise regs for turbos

[ambrose]

I've just booked a track day at Donnington in October which has a 9dB maximum. Since the baffles were a bit gone in my exhaust I wanted to check the noise levels for my car. The noise test guy at Donnington was very helpful, but told me that my car, a 1987 Porsche 944 turbo, would be likely to fail the drive by noise limits.

Anyone got any experience of this? Am I limited to 'noisey' track days or ones that only have static noise tests?

It's a tad annoying since one of the reasons I bought this car was to do track days!

cheers,
Chris

[woof]

If it's a static test - just don't over rev it - make sure the car's nice and warm - and build the revs up slowly - should be fine

and keep away from the pit wall and ease off a little for the drive past test

bit of nonsense really coz the have bloody jets landing every 10 mins

ambrose said:

I've just booked a track day at Donnington in October which has a 9dB maximum. Since the baffles were a bit gone in my exhaust I wanted to check the noise levels for my car. The noise test guy at Donnington was very helpful, but told me that my car, a 1987 Porsche 944 turbo, would be likely to fail the drive by noise limits. Anyone got any experience of this? Am I limited to 'noisey' track days or ones that only have static noise tests? It's a tad annoying since one of the reasons I bought this car was to do track days! cheers, Chris

[GarrettMacD]

ambrose said:

I've just booked a track day at Donnington in October which has a 9dB maximum.

Jesus, I know the noise police are getting strict, but NINE dB. We'll all be turning up in milk float's next...

Seriously though, don't gun it at the top of the pit straight, and stay well over to the right hand side, you *should* be OK

[rustybin]

Was he saying you would fail because of the exhaust noise or because of the dump valve/wastegate noise? I was chatting to a guy at Spa recently with a 911 turbo who had had a Hayward and Scott exhaust fitted that had a seperate silencer fitted purely to solve this problem.

[Chris Wilson]

It should be easy to have an exhaust made to pass Doningtons 98 Db drive by limit on a turbo car. It's high compression N/A ones and rotaries that pose a problem.
The turbo itself "uses" a lot of exhaust energy and acts as a silencer. Any of the pro exhaust comapnies should be able to advise.

[ambrose]

Thanks. I understood that the exhaust was the least of the problems. The main point was that in static test the turbo will not be spooled up.

[rustybin]

ambrose said:

Thanks. I understood that the exhaust was the least of the problems. The main point was that in static test the turbo will not be spooled up.

Now I'm confused. Why would the turbo not having spooled up make it louder? Even it did couldn't you just put a few more revs on until it was? I don't know the 944's set up but most noise tests are done at 3,000rpm or more when most turbo's should be spinning pretty happily.

[Chris Wilson]

The turbo spool will have no effect on a static test, as it WON'T be making any noticeable boost. A turbo is doing several thousand RPM with the engine just idling anyway, but won't have the gas volume to make boost. I can't see what your concern is regarding it being a turbo engine.

[ambrose]

Chris Wilson said:

The turbo spool will have no effect on a static test, as it WON'T be making any noticeable boost. A turbo is doing several thousand RPM with the engine just idling anyway, but won't have the gas volume to make boost. I can't see what your concern is regarding it being a turbo engine.

Apologies for an confusion. As you say on static noise test the turbo will not be generating any boost, so no induction noise etc. It is passing the drive by test which concerns me.

[oldtimer]

this is all a bit theoretical - why dont you book on to an evening track day at donington- costs about £100 for a 3 hour session 5.30 to 8.30 and see what happens - bookatrack have some coming up well before october - then you will know if you have to spend on exhaust mods. If you fail it wastes a minimum amount of money and time ...also see previous advice as to position of tests....

[ambrose]

oldtimer said:

this is all a bit theoretical - why dont you book on to an evening track day at donington- costs about £100 for a 3 hour session 5.30 to 8.30 and see what happens - bookatrack have some coming up well before october - then you will know if you have to spend on exhaust mods. If you fail it wastes a minimum amount of money and time ...also see previous advice as to position of tests....

The cost of the saturday full day is only £125. Are the summer evening sessions worth £100 in comparison? The messages above have cast doubt on the value of these cheap donny days, so I could imagine a situtation where you got almost as much track time in the evening as during a full day at the weekend.

[jleroux]

you can't compare track days purely on a cost per hour basis any more than you can compare cars purely on a cost per BHP basis.

as for noise testing - I invite anyone who is unsure as to their noise level to come to any of our donny evening sessions (without paying) and having a run.

all i ask is that you are there for the briefing and if you pass, you pay for the evening.

cheers,

Jonny
BaT

[ambrose]

jleroux said:

you can't compare track days purely on a cost per hour basis any more than you can compare cars purely on a cost per BHP basis. as for noise testing - I invite anyone who is unsure as to their noise level to come to any of our donny evening sessions (without paying) and having a run. all i ask is that you are there for the briefing and if you pass, you pay for the evening. cheers, Jonny BaT

I may well take you up on that. Thanks to all contributors. This is as positive result as I could hope for.

Cheers,
Chris