high flow header/ loss of torque?

6 replies to this topic
  • timothypg

Posted August 04, 2006 - 07:36 PM


86 xr600r. need a new header. i have heard a higher flowing pipe will reduce low end torque, is this true? fmf has one that say's it will increase low to mid power. any thoughts? tim . i have after market ex. already. wileyco.


Posted August 04, 2006 - 08:12 PM


The higher flowing exhaust will have less restriction, so you will lose the backpressure required for low and mid torque. The top end will be noticeably more powerful though. I have an FMF Q full system, and it has a portion of the midpipe that looks like a small expansion chamber. They call it the PowerBomb. I'm guessing this is the one youre talking about. I am not sure how much torque it gives, because I had my engine rebuilt (overbored) and carbs jetted at the same time I put the exhaust on. Let us know what else you find!


  • rebelventurer

Posted August 04, 2006 - 08:15 PM


I put a high flow fmf header on my 650l and seemed to gain some low end grunt, am told the powerbomb header is a little better on the bottom end.

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  • sl33py

Posted August 10, 2006 - 10:49 AM


I have the powerbomb header and powercore4 (650L)- great low end and gain throughout. It's better across the board now. way more on the bottom - lug down and pulls...

good luck!


  • timothypg

Posted August 10, 2006 - 03:52 PM


i just ordered a stock head pipe from xr's only/ceramic coating. i wanted to stick with oem size. they said a couple weeks, hope it works out.

  • BluezookS

Posted August 10, 2006 - 06:22 PM


Here is another opinion. I don't know I just found it looking for 650 stuffl

fmf power bomb

  • skyriver

Posted August 10, 2006 - 07:17 PM


I have the hi-flow headers with FMF PC IV and thought it was too loud. The bike had tons of torque throughout, but definitely had a lot of top end. I put the FMF quiet insert (baffle basically) in there and noticed a gain in low end. I'm guessing because of the back pressure. Bike is nearly as quiet as stock now and I think it actually runs better. The jetting my have been just a tad lean as every now and then at low elevation I get popping on the decel. Now it seems right on. Who knew a baffle would actually make the bike run better.... I like to take it out every now and then (mostly around town or private property) just to let her scream, and I'll admit it even though I firmly believe in being quiet.... it sounds awesome.

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