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Every vehicle noise standard I have found (except FSAE) is noted in dBA and not dBC, as hearing damage is usually the concern.Quote:
Originally Posted by Bemo
In any case, the new 100 dBC idle is completely out of the blue from the RC, with no justification (and I think the RC *needs* to address this).
What was the justification of the old limit? What is the justification of the noise limit for street cars? If you limit it to 110 or 115 or 120 dBC or dBB or dBA it is also out of the blue. The whole procedure of the noise test is out of the blue. So what? The limit of 610cc displacement is out of the blue. Why do you think the RC has to justify that they want the cars to be quieter?
If the addressed problem is to quiet down the track to make it easier for track marshals and others to communicate the switch to dBC makes perfect sense (I am not part of the RC, so I don't know what really led to the change, I'm just guessing as anybody is).
No offense, but this discussion is kind of stupid. You are supposed to put a bigger muffler to your car and your major argument is "but I don't want to"...
It's not 'I don't want to' it's more like 'I have to drop 20 dBC and triple the size of my muffler and reduce idle misfire and ... and ... and .. because of a drastic change in the noise limit well after the design of the 2015 powertrain has begun because the rules came out so late. We are supposed to be building racing cars 'for a weekend autocrosser', yet we're well under the noise standards of major racing series, and even under street car or off-road vehicle standards.Quote:
Originally Posted by Bemo
I think it's reasonable to ask the RC why they felt an idle noise limit is required, how they determined 100 dBC was adequate, and how they determined 110 dBC was adequate as well. Unfortunately, there's really no way to question a rule or email the RC directly.
Since they obviously studied the noise of cars in 2014 and 2013 in both dBA and dBC, they thought through the issue, they warned us about switching from dBA to dBC, we thought they would adequately study the change based on the data they took, and they ended up with seemingly random numbers and an idle noise limit out of the blue.
Usually street noise limits are set by hearing damage to nearby property, and the noise limits are evaluated for their hearing damage potential at the distance from the vehicles that people are.
At both US FSAE event venues, the Formula SAE vehicles are the quietest vehicles that the track will see. Lincoln is an active airport, with planes taking off just past the competition boundary, so the FSAE noise is almost a drop in the bucket at some times to aircraft noise.
Hi guys,
you may want to look at this old post from Tobias Michaels Blog:
http://tobiasmic.blogspot.ch/2013/09...anges-for.html
it's from 2013
Cheers,
Yannick
Yannick,
Thanks for the link, it clearly explains the justification behind the move. It would be great to see this communication made officially where possible.
The part about sustained exposure to noise levels from the track workers was interesting. A distance of 5m away is quite close. I wonder if it becomes sensible to provide ear protection to all marshals under these conditions. It isn't likely a problem for the small competitions, with cars passing quite infrequently past marshaling points. Ear protection can be combined with radio gear to keep communication lines clear. The cost could be considerable, but would be amortised over many teams and competitions.
Kev
Bemo,Quote:
Originally Posted by Bemo
Were all single cylinder cars that you were near too loud? Or was it only a few of them? What I noticed in 2013 (I was also in the dynamic areas when cars were warming up/running), is that only a few cars were actually loud. The rules clearly state that if an official believes a team to be in violation of the noise rules, they can be re-tested. Why not enforce the rules that are currently in existence? Why continue to add more rules? If a team is loud (because they are cheating, and have pulled the plug from their exhaust), then go re-test them. It's a simple procedure that doesn't seem to be followed. Instead, all teams will be punished for the actions of a few.
This, especially the bolded portion. The noise levels generated by most SCCA autocross cars is also far in excess of what most FSAE cars make (except those cheating the noise test). Yet people stand similar distances from their tracks, and nobody complains about hearing damage.Quote:
Originally Posted by apalrd
I have a feeling there will still be very loud single cylinder cars, while they are on track. Yet, these same cars will likely get through the noise test without any troubles the first time. If they get re-tested after the dynamics, I have a feeling they will fail miserably. Not because of packing burning up, but because they were not given the chance to re-plug their exhaust...
-Matt
It explains the move to dBc well (which in my opinion is totally reasonable), but not the new idle limits. I feel like it is the idle limits which make little sense as many stock street cars and bikes (shown here and in our own testing) do not meet these rules.Quote:
Originally Posted by Kevin Hayward
Let me chime in with a little history (and stir things up).
Someone has asked why we don't have trackside noise measurement "like SCCA Solo" or (SCCA road racing). In both cases these measurements are taken at a distance of 50 feet from the edge of the "racing surface". Any transgressors are given a warning and told to fix it. FSAE used to have a measurement system like this up until about 2001 or 2002. We had a dynamic (pass-by) test to get the tech sticker and then cars were monitored during actual events, and many times were DQ'd for being over the limit. They had passed the official test and then got DQ's during an event. This resulted in many very unhappy teams! .
At the second FS event at the NES in Birmingham in 1999, John Hoole, the MSA scrutineer assigned to the event, who was also an MSA noise scrutineer, pointed out that the MSA used a static, ½ metre test at 4000 rpm, which seemed to do a good job for their road racers. He agreed to do a comparison of the then current FSAE test versus the MSA test. We picked a piston speed of ⅔ of the red-line (equivalent to 4000 rpm for a typical road car that has red-line of 6000 rpm). The correlation was reasonable, and the test procedure was simple, repeatable and possible for any team to carry out. So the test procedure was changed. No problems for about 7-8 years. Then we started getting singles, and singles are the problem!! The workers have been complaining of the noise of the singles at idle and low speeds, not at high speeds. The first complaints I heard of were from the skid-pad workers, and then from those working the start of Endurance as the singles sat at the starting line. The problem is the massive attenuation that the A scale gives at the low frequency of a single at idle. Tobias explains it very well in his blog.
I know that the Rules Committee has done some significant survey work on this, although I have not seen the results. But the numbers have not come out of the blue.
I have just measured my D Stock 2005 Cooper S, which is fitted with a SuperTrapp, it is comes out at 99 dBC and 84 dBA at 1100 rpm (warming up), and 94 dBC and 78 dBA at 8-900 rpm (warmed up). It is plenty noisy on a solo course.
What does this all mean?
A). You need to get your engine calibration so you have no miss-fires!!
B). You run the noise test with a warmed up engine.
A) and B) mean that your calibration person needs to do a good job.
And it might well mean that simple absorption/glasspack mufflers will not be good enough for singles. Teams are going to have to do a little muffler work and maybe start using mufflers with resonance chambers rather than pure absorptive ones, i.e. some real engineering work!
Michael Royce.
PS. The ½ meter test is simple. I know, because I do it on the Moto GP bikes at IMS and COTA!
As Kev suggested, why not give marshals some earplugs/phones? I'm sure that anyone standing near a PA speaker whilst someone is calling the race would be exposed to more SPL than is provided by the singles. What about drivers? Do all drivers now need earplugs as part of scrutineering, or just those driving singles?
To me the main problem here is that a team now cannot use an off-the-shelf muffler (for which there can be perfectly reasonable justification), so they must build one themselves. Cue the melting/falling off mufflers, and inherent (real) dangers that implies.
Warning, this is somewhat off-topic.
I was neck-deep in the google machine looking at motocross mufflers and I ran across this image. The guy in the middle in focus looks so bored for being in the middle of a supercross race!
Attachment 335
'I'm just standing here as dozens of motorcycles literally fly past me.'
Hehe. Made my night.