2015/2016 ISR oval rules are posted

[Flatout]

The rule states 15 holes per square inch not per linear inch. A 1" diameter tube 3" long has an inside area of 9.42 sq.in therefore the tube must have 142 holes or more to be legal. Now I'm not gonna be counting holes but if it looks like the holes are spaced more than 1/4" apart I will take a closer look. The new silencers I make use perforated sheet 1/8" holes on 3/16" centres. I roll a 3 1/2" long tube of the perforated material the same ID as the stinger. The silencer has the perforated piece welded between the stinger ends. The whole hing is pressed together with Fiberglas mat inside a 2" aluminum tube
I can make pretty well any of the standard I D sizes.
And FYI I had nothing to do with this rule change either!

[tp176]

A little background first.

Some years ago Mr. Gokey sat thru some meetings that involved the EPA. At the end of it all, we could be proactive and create our own rule or wait for the government to write it for us - we wrote our own. After HOURS of discussion, at times heated and at least one pencil slam by Mr. Gokey, I came up with the wording that the exhaust must be "functonally silenced". This served us well for a very long time - until the (a) DRAG RACER(S) complained about someone with a green sled having the exhaust out the side of the sled and it distracted his driver into redlight submission when the stutter button was activated. Well boo-hoo. What came from that was a set of drag race exhaust and silencer rules that a Philadelphia lawyer wrote. We were all fat dumb and happy with what we had. Now, I do not know who brought about raising the issue again in ovals but I for one was not happy with the outcome. Regardless, here we are. I can assure you that ANY number of holes WILL reduce the db level. The silencers that we have benn using had about a half dozen, 1/4" holes in them. THEY TOOK THE SHARP EDGE OFF! We now have some that use a perforated tube that has about 20, 1/8" holes per square inch. Are they softer on the ears? Yes. To NOT use some discretion as a Tech man and actually disqualify a racer over that is a bit extreme. Please, no one bring up a db test - you can not believe what standards would have to be used to create one of those nightmares. I have done db testing when the ATV race groups tried to have a db rule. We have also done testing on our own products and all parameters must be VERY close
to insure accurate comparisons. 2 db is TWICE (2x's) 1db and 104 db is TWICE (2x's) 103 db. Do 4, 1/4" hole reduce the db - yes. Does 15 per square inch reduce it more - yes. Did we need to throw all the teams that made good faith efforts into this mess - no. Did we need to actually police the problem teams that had NO holes - yes. Just like our government should do - ENFORCE WHAT IS THERE - DON'T MAKE ANOTHER LAW!!!

Tony P

[RacinFan]

am I wrong for thinking that the old silencers were riveted on?

[that 31 car]

To Tony's remarks, I agree with most if not all, but from the ISR position here is what has been found the last few seasons.
1. Less and less holes, even a few with a straight thru pipe inside with no holes. ( Using a video stick to view)
2. More and more complaints about harsh noise, one sled much louder than others, and drivers pointing fingers at other drivers for no or ineffective silencers.
3. Just so all understand I am talking oval only, drag racing has its own special can of worms when it comes to exhaust.
4.Db testing is not the real answer here, but is and was a indicator of the problem coming back, which it was.
5. Common sense application by the tech man is appropriate here, nobody is going to count holes, I assume, but inspections for holes/perforations will be made, and noise output will be monitored. Thus guys who are stretching it a bit will be consulted and asked to comply.
6. Some promoters and some fans even entered complaints on sound the last two seasons, so a "refresher" course on effectively silenced was needed. This method was chosen because some tech officials were challenged on "what does effectively silenced mean? " and "prove mine's illegal", so here is what you end up with.
7. Common sense, by all involved, is in order here.
8. Too bad this wasn't the deal in the 70's, wouldn't be as many 60 year old guys walking around saying "huh!" a lot.

Matt you are correct some are riveted, but some are welded directly on, some are clamped, seen lots of variations.

[tp176]

Right on Jerry.

Tony p

[RacinFan]

Thank you Jerry.

I appreciate the way you broke things down.

When I was thinking tech stuff, I had completely forgotten about camera stick thingys

[Flatout]

So after a lot of discussion it was decided in the CPT that we are going to use discretion and phase the new silencer spec in slowly. We are not going to ask everybody to replace their silencers right away as long as it is determined that they actually do silence the exhaust somewhat. This will be a judgement call by the tech man. Basically the rule is to eliminate the silencers that are not functional. There has to be at least 50 or 60 holes to have any noticable effect. All the silencers I have made have 8 rows of 8 holes that are 5/32 dia. We will be inspecting with a camera and a wire probe. If the holes are blocked or there are 20 or less holes you will not race with those silencers. If there are more than 20 but less than 50 or the holes are too small you will get a warning for that weekend. Also the outside diameter of the silencer needs to be 2" or greater and needs to be 3" long minimum. All the new silencers I am making (and we ask all pipe builders to do the same) will be built to the new spec. Eventually all silencers will be new spec as the old pipes become rusted out or destroyed. Have a look inside your silencers to be sure they have at least 50-60 or so holes

[tp176]

Much better Howard. Safety aside, discretion and education are the best course in a situation such as this.

Attached is what we are producing.

Tony P

[RacinFan]

I'm kinda curious about the silencer rule.

Has anyone tested the new silencers to see how much "quieter" they are?

Does anyone have a decibel measurement of some sort?

[tp176]

I have not checked with a db meter yet but I can tell you it is NOTICABLY softer! I will get some numbers together but they are all relative to angle, background, distance, surface...............