Soundcheck info request
Posted September 16, 2002 - 07:59 AM
Does anyone know where I can find the RPM value at PEAK horsepower, for a factory stock 01 wr426f, and a 01wr426 with the throttle stop shortened, air box lid removed, and stinger removed.
Posted September 16, 2002 - 03:02 PM
That I know of there are only 2 exhausts in the world that will pass the 94db test.
One is made by CRD and is sold by BAJA Designs. It is rated at 91db.
The other is the made by yamaha and is on your bike with the insert in it.
I have a FMF megamax II on my yz400. Its quiter than stock but I know it wont pass the 94db test. Ive heard that if you take most of the disks out of it it will pass but then the bike wont run. so your screwed eather way.
Ive heard of a meathod of quieting a scilencer. Find a plant buld auger the size of your perforated core. Its like a large corkscrew drill bit. You may have to cut and weld a few of these augers together to make them as long as your core. weld it in place inside your core. In theary this will push the soundwaves into the packing without restrecting the flow.
Posted September 16, 2002 - 06:48 PM
All the bike mods you've listed don't bear on the issue. It's only rpm (which is bike model and year specific) and test method that determine the outcome. They're actually intended to ensure that your bike mods don't make the bike too loud. BTW the harmonics tuner is just a mechanical tachometer to let them see you're holding the engine at the right rpm during the test reading.
So, the 01 and 02 test rpm values are probably still 4500 rpm. In case you're interested, a stock YZ pipe will blow over 100 dB at 4500 rpm. A stock WR pipe (intact!!) will maybe meet 94 dB - I measured 96.
Any Q's just ask. :-)
Posted September 19, 2002 - 05:22 PM
I have the Vortip in my stock exhaust on my 01 WR426. I was measured at one of the CCC events this year and I passed the 94dB limit. I was not told how far under 94 I was but guys all commented on how quiet it was. I think it is quieter than stock at idle and gets progressively louder than stock as the RPMs increase, but passes 94 where they tested it.
Hope this helps.