pipe and valve influence on a fuel consumption

[live]

Of course, i've heard about a drastic power improvement after installing fmf gnarly pipe and a boyesen reed valve.

But, how does it affect on a fuel consumption? AFAIK these mods are just efficincy improving stuff, so fuel comsumption should become lower.

Am I right?

 

[ridejunky]

Theoretically but it is not a car, if you are using the increased power( thats the point) you may see less range. If a dirtbike doesn't have the range you want, put a bigger gas tank on it, if the cost of fuel these things use is a problem then a F/S mountain bike is the way to go.

 

[live]

fair enough :)
but we have a kid here, who has a suzuki rmx250. it has much more power, but consumes the way less. for example... once we had a little ON road (asphalt) trip for a 90 kilometers, sticking together. He had a consumption about 4.5 litres, but for me it was 7.5 litres!!! more than 150% difference!!! :(
Offroad consumption differency is almost the same.
that pisses me off!! :D

sorry for my french :D

 

[ridejunky]

Are you bigger than the kid? maybe he is more slippery in the wind( just sayin). all kidding aside the state of tune these bikes are in, pipe etc will affect fuel economy. A gnarly desert pipe on a 220 may improve its road mpg but hinder it on a 200, idk i think you have to compare like bikes, apples to apples to gauge mpg.

 

[live]

yes, I'm 10 kg heavier than that kid. but 10 kg's is not 50% :) my weight is about 72 kg.
but maybe the 25% displacement difference while travelling at one speed, ~15% weight difference altogether leads to that difference in consumption...
but 4.5l/100km?! that is outstanding for 2 stroke. i didn't ever heard these numbers... everyone reporting about 7 or so. it's even great for a 250cc 4 stroke enduro! But i saw it by my own eyes :)
but... by the other hand... you are right. mods are leading to something... we have another kid who has a rmx 250, too. but that suzuki is derestricted (australian version)... 51 hp vs 40 for the first kid's rmx(japanese). It's fuel consumption is about 11 l/100km. o_O But i think it mostly because of the bigger compression ratio.
but... pipe and valve... they seem to me as a loss minimising devices.
I think I should try them :)

 

[Rich Rohrich]

KDXs have notoriously bad transfer ports which tend to short circuit the fuel right out the pipe during scavenging. Fuel efficiency goes right along with it. Fix the transfers and you'll improve the scavenging and make a big impact on fuel efficiency, along with making it more fuel tolerant and a TON easier to jet sharp.

A pipe and reeds won't fix the fundemental issues with the production flaws that are built into those cylinders. It can only mask it some.

 

[ridejunky]

Live,
Modify your bike for the best performance that suits your riding style and environment
not fuel efficiency. Unless you are using it as a summer messenger vehicle, transporting vital vaccinations to the native Alaskans in the remote wilderness where gas stations are scarce, the fuel savings is a drop in the bucket. How much road riding do you do? if you are lying awake contemplating the fuel efficiency of your KDX you are on the wrong bike. Most people spend way way more on gas in their truck to get to their riding spot than they ever will in the KDX on a day of hard riding.
Just out of curiosity, it sounds like you are from Canada, is your bike a street legal?

 

[live]

ridejunky I'm from Russia, we can legalize anything here :D And if KDX will be used properly (quite fast, short rides), it's consumption is not a big problem. But we can travel 200 miles before getting to the new offroad traces. Russia's big! :) and 100-150 miles offroading for the one way may be normal. So i have to take at least 10 litres of fuel in my baggage for the trip :D It's not easily tolerable :D
Rich Rohrich, is that theoretical, or that's a real deal? where can i read more about 'fixing the transfers'?

 

[ridejunky]

" But we can travel 200 miles before getting to the new offroad traces."
I see why fuel economy is important now, WOW.

 

[Rich Rohrich]

Rich Rohrich, is that theoretical, or that's a real deal? where can i read more about 'fixing the transfers'?

It's very real. Pick up Eric Gorr's book or Graham Bell's book on Amazon and you can learn all about porting and it's influence on performance and engine efficiency.

http://www.amazon.com/Motocross-Off...UTF8&qid=1380128051&sr=8-2&keywords=eric+gorr

http://www.amazon.com/Two-Stroke-Performance-Tuning-A-Bell/dp/1859606199/ref=pd_sim_b_4


Here's an article Eric wrote and an excerpt from his book that will get you started :

http://justyamahard350.com/articles/eric.htm

http://www.eric-gorr.com/incl/pdfs/do it yourself maching.pdf

 

[live]

thanks, guys!
Rich Rohrich any successful precedents concerning kdx200?