Goodwood

[Nick M]

Induction noise when the engine is under load and at full throttle is a lot louder.

HTH.

[Blatman]

Yup. In my sprint car (48 Webers), at anything above about 3500, all you can hear from the passenger seat is induction roar. At much above 5000rpm, induction roar almost drowns out the exhaust, which, like yours Conibear, is right by my right ear.........

[conibear]

Were you standing to the back or front of the car when doing the test?  I have been done both ways at Goodwood  

If they stand at the back of the car, the noise meter is pointing almost straight at the carbs so I would expect the induction noise to make a greater contribution.

I did both it made no difference

Yes Nick, any engine at full throttle or under load would produce more induction noise, but it would also produce more exhaust noise as well, it's all relative.

Induction noise is pre-compression, but yes it maybe a big deal if you have a super douper exhaust system.

At the end of the day, surely crap exhaust systems are our main causes of noise failures on trackdays.

Ian

[Nick M]

No, it's both exhaust (which is more easily dealt with by way of a bigger / better silencer) *AND* induction noise (which is less easy to stifle without resorting to air-boxes, etc.).

The more powerful the car, the more air it has to suck in to mix with the fuel and hence the louder the induction noise gets.  I'm sure there's also some physics which relate it to the size and / or length of the induction tracts and the size of the engine but the fact remains that cars *do* get thrown off trackdays for both exhaust *AND* induction noise.

A subjective assessment maybe, but listen to a car on a rolling road - a lot of what you are hearing is induction noise.  Certainly the case with my car with it's relatively small engine but decent silencer.

[conibear]

Personally I have not witnessed drive by noise sensors so have no knowledge and I was only really commenting on static tests.

I agree with what your stating Nick, but my experience of my engine seems to be different from that of yours. I think it's fair to say all engines are different, especially in their different guises, thus there is no rule of thumb.

Ian

[Jay m A]

Just to add, I *just* passed the static 98dB test at Goodwood the other day, with a VX engine and SBD 208 kit with SBD 7" carbon exhaust, freshly repacked.

However I had to lift whilst going past the meters on track, the marshalls are strict but fair play, they want you to pass the static.... and give you enough warning when on track.