mikstr

AS my bike sits hibernating, I was thinking of pulling the stock exhaust header off (seeing as how I can't seem to find a full system for a reasonable price anywhere) and grinding all the inside welds down so as to improve airflow. I did a partial job at the rear collector but didn't want to remov the system to go any further. With the bike sitting idle, I thought it might be a good time to finish the job (all welds) and then finish off by getting it ceramic coated. Has anyone tried this? Is it worth doing? It seems to me that if it's worth working over the ports to improve flow, it should also be worth doing it to the exhaust (since any weld whose surface rises into the exhaust tract effectively creates a restriction and turbulence, thereby reducing flow and choking the engine). Obviously I am not expecting massive gains but a free hp or two would be nice Your thoughts?

cliby

this or something similar, has come up before, especially about the 'obstruction' in the collector. If I recall 2 very respected tuners, 1 US, 1 UK supposedly had opposite views on this as relayed by people who'd asked them. I do know the moriwaki full system I have has a suspiciously similar 'obstruction' in near the same location that appears very intentional, and the internal welds aren't much different from stock. So I'm guessing its not particularly important or perhaps even optimized as is. I think the dynamics of what is happening inside the pipe are not easily predictable and without a lot of trial and error and dyno in between it would be a very random event to improve it.

mikstr

Hi Bill,

I wasn't looking at the "obstruction" near the collector as I am one of the ones who tackled this issue with Roger Ditchfield at Revolution Racing in the UK (and he counselled to leave it alone). I was looking more at the welds themselves.

cliby

gotcha. still not sure. how much of it could you reach? like I said I didn't notice the inside of the moriwaki to be any differnent than stock. what I've read before seemed to agree that modifying stock is unpredictable and except for assuring the holes are matched at the header/head interface without obstruction there isn't much but guessing after that. I would polish the bike instead! mine has so many bugs on the front that i'm sure it would be good for at least a few mph

mikstr

Did you dyno your bike both pre and post Mori full system? I am curous to see what kind of gains you got from it.

cheers

cliby

I did. I'd already done the other engine work and had slip ons. the full exhaust changed the jetting requirements A LOT (it went very rich by just putting the full exhaust on - I had to drop down 2 sizes on the main jets to get them right). I got gains starting at 4500 rpm all the way to red line. Gained 2 everywhere but gained about 5-6hp from 6000 - 8500 rpm and about 2-4hp near redline. Torque almost same number increase as hp. Plus lost another 14 pounds over the stockheader and staintune slipons combo. The sound with the full moriwaki is amazing.