WR 45 racer

[bikenut]

Im a active WR racer, on my bike are custom built dual straight pipes, a "tuner" told me my pipe length was to long, and i would gain power with shorter pipe length, what is the best pipe length for flatrack racing on mostly short tracks???
my pipes were made to fit the bike and are not really long, but i have seen shorter drag pipes on bikes in use.

[rousseau]

This is just one of the many reasons racing is so much fun.
Since you stated that you mostly run short tracks, a 2into1 system would probably benefit you the most.
Short drag pipes are are excatly that. Best for drag racing.

[charlie frey]

Years ago, a buddy had access to a dyno, and we went looking into exhaust/horsepower by starting with 2 long pipes and cutting off an inch at a time.
HP peaked, and then dropped off after optimum length.
We were surprised by the results.
He was a late-model guy interested in Evo HDs. If I remember, we got the best HP at 29".
I'd say that this would be the best way to tune an exhaust.

[rousseau]

Before the days of dyno's (way back) The method used was to paint a stripe along the length of the pipe with some simple enamel. Somthing like testors model paint. Use silver or gold color. Make a few runs to burn the paint stripe. Just past the point where it stops burning is where you would cut the pipes off.
(Hillbilly Dyno)
Short drag pipes will give the most "peak" horsepower but will never give the best torque curve or any good useable power in the midrange. They are only best at W.O.T. This is why I suggested something else for short track racing.

[LouieMCman]

I've always heard the optimum length of drag pipes was 30 inches. That is what I ran on my Troublehead for about 20 years as attested by my lack of hearing in my right ear.

[AdminGuy]

Now this interests me! Thanks for the info all. Real world experience. Great stuff!

So as the sonic wave of exhaust gas travels down the pipe your looking for the sweet spot to release the wave and create the greatest amount of exit flow. Is this correct?

Does the wave double back on itself to create some back pressure? Perhaps too long a pipe and it does? Is this correct?

RPM range would effect this I'd think. So that 2 into 1 seems like great advice.
Good on all you guys! I love talk'in bout this stuff!

Paul Edwards--

[Rub]

Back in the early seventies I was building hot rod engines and came across an article in Cycle World magazine that had a formula for determining pipe length based on desired use and taking into account intake tract length, valve overlap, and ignition advance. My '56 pan lower end engine with a shovel top end, self ported, 88" stroke(4 3/4 inches) with a Leinweber .485 lift cam and S&S GAL carb, Sifton collars, springs , and pushrods, polished rods, etc.made lots of power with 34" pipes. Gordon Jennings was most likely the author of the article. Don't know what year or month though. On factory WRs Harley used two into one with a short turnout pipe section, a long pipe on WRTT models for power higher up. Robbie

[bikenut]

WR racer exhaust

hello all thanks for the replys.
what I am refering to is a modern built 45" racer that is used on modern short tracks.
indoor short track I am racing on now is less than 1/8 mile dirt oval, it is wide open throttle for a moment of time, then turn, repeat etc.
Even my modern bike [rotax, yamaha] are tuned specificly for this short burst of power racing.

I am aware a H-D flathead is not the bike of choice to race if you want to win "vintage class" where any "old" bike can run.
some of the setups and ideas H-D used on the WR's were known to many, but the design was to race on 1/2 mi or mile ovals, the turns were bigger in yardage than most short tracks that exist today.
[try to get a current pro flatracker to ride short track without brakes on his modern bike]
{yes my 45" has disc brakesjavascript:smilie('')

my 45" racer is setup with a final drive of say 12.00 to 1 ratio in hi gear, so you can see the bike is reved high to try and get some power to the ground.

any interesting racer "tips" will be appreciated.

[AdminGuy]

Hummm.... maybe I'll get over to Ron Lacys and measure his WR racers pipes for you. Just for comparision. Ron has raced his up and down the west coast. Broke his leg last year. Wooops!!!!

[bikenut]

WR racer exhaust

hi admin guy, me and ron L have raced since he got his WR together, i have come to canada and he has raced with me alot on my WR and scout at the yearly vintage races in washington state.
his bike is quite stock WR for all the purists out there a great example of what H-D sold to racers.
my bikes are more modernized in a effort to race with other newer bikes us handshift riders are forced to ride with by the promoters if we want to race, as there simply are not very many races where racers can get more than a couple handshift bikes together on the track, i guess some guys are happy with racing once a year at davenport........