Power Core IV-2 Observations

This weekend I ran a new Power Core IV-2 tail section using my stock head pipe. The pipe finish is outstanding lools like it is creamic coated. This was the toughest pipe installation of all the pipes I'v tried. Things were ever so slighly off but eventually I got it on.

Unfortunatly for FMF I was comparing it to my current set up which is a WB CF Pro-meg e-series with a tapered Ti headpipe, running 15 disks. The WB set up in my opinon was hands down better in all performance aspects. The Power core IV-2 did have exceletnt low end to mid range power and if I had the Power bomb header to go with the tail section it probably would have greatly improved things. The WB system just seems to flash through the power band better and definately is better on top. On the bottom end they are similar. However, without FMF's header installed this is probably not a fair comparison.

As to noise its still loud--not as loud as the WB with 15 disks but it was loud and you can here it from a lon way off. None of my fellow cmapers thought is was any quieter. Again with the Power Bomb header things would have been better in the noise department. I personally thought it was quieter and not as harsh as the WB when riding the bike. But maybe all the noise was just going straight back and not out the side disks so to me it seemed quieter. It was less stressing to ride with than the WB set up. However, if I went down to 8 disks probably would have been closer. Without a DB meter its really hard to judge, but while riding it was quieter to the rider.

As soon as I can get my hands on a Power Bomb header I will be back at it for further comparison testing. As of today the WB set up is on the bike.

There is a small voice in my head saying--tapered head pipe, Stroker tail section and a stroker quiet turn down tip--Anybody tried this combination??



Thanks for sharing your observations. It sounds like there is no magic answer to provide max performance without a lot of noise.

I assume that yours was NOT the SA version. Is that correct?

Eric in WA


’99 WR400, YZ timing, IMS Tank, YZ Seat, Acerbis Handguards, Scotts Steering Damper, Renthal Bars, Yamaha Full Skidplate, Devol Rad Guards, Dunlop 755F & 756R Tires

’99 Polaris 400 Scrambler –“Trail Couch and Lunchwagon”, ’99 Honda Z50R, ’97 Honda XR70R, Kubota L275DT and an assortment of farm equipment.

It is possible to add power and lower noise. The problem is that they have to keep the pipe light.

Some promising technology involves the generation of sound waves to cancel out noise.

There are two approaches to this.

1) Passive. A sound reflector in the pipe bounces sound waves back against the sound waves coming out to cancel them out. It may require a larger/heavier pipe and may reduce power slightly for only a few decibles reduction.

2) Active. A sound sensor detects noise and generates sound waves to cancel them out. I've seen some industrial applications where the noise reduction was drastic! The drawback is that it may be complicated to add this to an exhaust pipe. It has more parts to break (wires, sensors, sound generator, etc.) but should be fairly light. I'm sure they could knock off 10db or more without a loss in power.

The question is, is anybody actually going to try this when it's cheaper to put a removable plug in the pipe just to pass government approval.

I remember a GM project with a Corvette like that. I can't remember the exact specifics but it used sound waves that canceled out the exhaust noise. I seem to remember that it was only for inside the car and the noise came through the speakers along with the radio music. You couldn't hear this other noise but it cancelled out the exhaust sound waves.


'99 WR400

'92 GSXR 7/11

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Thanks a ton, Clark!

I had an engineering buddy over this weekend and asked him his opinions. He felt that the lower sound waves, being so much longer than those of the 2-smokes, need a different technology. The downside was the pipe would have to be the size of 55 gallon drum to catch a significant amount of the waves. Hopefully there is something to the PowerBomb technology besides marketing???

Those of us at altitude, can't live with the stock insert. Everything we ride in Colorado is the national forests, so I'm worried some law Uncle Bill or Al will pass will make my bike a heavy, wheezing, gutless 4-stroke.


It's the same technology the vet uses. There are headphones that also use this (Sony makes them). The industrial application I saw was to reduce noise that a huge power transformer gave off. The transformer gave off a deafening (literally) buzz and the addition of one of these with a small sound generator plate made the thing tolerable without hearing protection. It cut the sound by 50db or something like that. The demonstration was very impressive.

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