Pipe power band questions?

[renes]

I've read that an aftermarket pipe simply moves power around in the rpm range, but FMF says they are actually adding power with their pipes. Which is true?

Also I'm looking at a Gnarly and Fatty. I ride mostly in the woods with hill climbing. I also do some motorcross riding. FMF's dyno chart area kind of contradicts what band their pipes are meant to do so I wanted to get some info from real people who have used them.

O, and will the pipe make the bike run richer or leaner?

Thanks. I have a 1994 YZ250.

 

[elf]

I've read that an aftermarket pipe simply moves power around in the rpm range, but FMF says they are actually adding power with their pipes. Which is true?

Both are true. yes they move power around mostly stealing a little bottom to add power on top. Meaning peak hp will be higher than stock but low end power might be less. The reverse will happen with a pipe like the gnarly. I have never needed to change jetting when using a different pipe, but I am sure there are exceptions. Looking at a dyno it is hard to tell whats going to happen when the pipe is on your bike. A small dip or bump in the line may look insignificant but may be felt when riding.

 

[WWR]

Most guys feel a power increase, but not really because of the pipe design. Often, you will get a similar power increase just by cleaning the carbon from your dirty stock pipe.

The stock designs these days are hard to beat.

 

[pobit]

Of the FMF pipes I have tried, the Fatty works the best for all around riding and MX. The Gnarly does give you more bottom but goes flat on top. The SST is by far the worst pipe I have ever tried. You lose bottom end to the point the bike falls off the pipe when torquing out of turns. The Fatty feels like the stocker with a good hit in the middle. It also goes a little flat on top. For MX, my favorite is the stock pipe. It's got the best balance of bottom with just the right amount of over rev for my taste. Dave