My 2nd gen afc at the dragstrip

[boostdoctor]

My son going on a wild ride on my afc

http://www.youtube.com/watch?v=Rm3MtdxwskI

[Bronson]

Nice trap speed. Changing the gearing for the 1/4 mile, what do you think the top speed of the bike could be?

[boostdoctor]

We have been 104 in the 1/8th on a smooth pass. This run was the worst of the day. The setup only has 4 runs on it, so we are still leaning it down and learning to ride it. I'm thinking we can get over 120 in the quarter. In fact we are going after the fastest cr500 on Youtube. The one that went 10.6@120. I'm thinking our 1/8th numbers are better right now. But I don't know for sure. Does anybody have more info on the Youtube bike?

[Bronson]

Nice. I'm building a CR500AF to run on the shorter sportbike tracks and would want it to run 120 on the front straights (usually 1/3 mile or so). Threads like this give me hope. Just need to figure out the engine build to do it... and one that'll last.

[boostdoctor]

Nice. I'm building a CR500AF to run on the shorter sportbike tracks and would want it to run 120 on the front straights (usually 1/3 mile or so). Threads like this give me hope. Just need to figure out the engine build to do it... and one that'll last.

U shouldn't have a problem hitting that speed in that distance. U r gonna need a big carb(not a 39pwk lol) and a topend pipe to get the motor revving. 15/40 gearing will probably be a good start. We are geared 15/44 right now. I will keep you posted on our progress.

[Roostius_Maximus]

a 38mm with pulse injection makes more power everywhere when compared to a 44 lectron

and I wouldnt worry about the big pipe too much, a fatty will pull more torque than either cpi. I've run the fatty, gnarly,dep, cpi (1st version) and noleen over 10,000, fatty got there fastest.

[boostdoctor]

a 38mm with pulse injection makes more power everywhere when compared to a 44 lectron

and I wouldnt worry about the big pipe too much, a fatty will pull more torque than either cpi. I've run the fatty, gnarly,dep, cpi (1st version) and noleen over 10,000, fatty got there fastest.

With what porting was all this testing done?....and how much power did you make?

[Roostius_Maximus]

I've built motors on those pipes that are 65 at the wheel on gas. Alky bikes need a custom pipe and can soak up bigger carb size. A pulse injected 44 lectron on methanol is running over 93 and 70ftlbs

[boostdoctor]

I've built motors on those pipes that are 65 at the wheel on gas. Alky bikes need a custom pipe and can soak up bigger carb size. A pulse injected 44 lectron on methanol is running over 93 and 70ftlbs

Do you mind explaining the pulse injection or pointing me to place to learn about it. I been out the loop for a while.lol

[Roostius_Maximus]

Pulse Induction, an explanation


Most guys are under the mis conception that everything is inward like the red lines in this drawing show.

https://gske4w.dm1.livefilestore.com/y2 ... se%201.png


In reality the crankcase pressure closing the reeds makes a reversion wave that travels back towards the air filter picking up fuel for a second time as it passes the metering system and almost completely stalling the inward flow. Blue lines represent the reversion.

https://gske4w.dm2302.livefilestore.com ... se%202.png


Now we understand that the actual inbound mixture has a triple metered wave and a single metered wave drawn into the engine. As the wave is drawing fuel on its reversion pass it is also back feeding the fuel circuit and forcing the fuel from the carburetor metering back to the bowl which causes the first 10-20% of the inward bound charge to draw a leaner mixture until the fuel returns.
The strength of the reversion wave is altered not by the crankcase compression of the motor, but by the crankcase volume. It's this reason that a 125cc motor takes a 192 main jet, a 250 is 180, and the 500's a 172 (average jet requirement). Lesser pulse wave strength on smaller motors means less multiplied fuel so an initial larger jet is needed. This lower strength wave makes a pulse unit less effective on small cc motors. It is not uncommon to see the surge of the stock reed boot on a CR500, the appearance of the boot absorbing this pressure does not have any measure able difference when compared to the wave in a rigid inlet like the Boyesen Rad Valve .


https://gske4w.dm1.livefilestore.com/y2 ... se%203.png


A Pulse Induction system replaces the stock boot that mates the reed to carb, its cone shaped chamber traps the majority of the reversion wave (blue) and channels it into the pulse tube where a specific length tube dictates the time for it to be re-introduced as an inbound charge. Metering of the fuel has now been almost perfectly restricted to a single pass of the metering system which no longer is having fuel forced out of it. The single metering pass has now given us an acurate and predictable means of metering the fuel. Commonly the jet sizes need to be increased since they are no longer working on multiplied passes. Throttle response is crisp since you are no longer stalling the inlet stream 1/2 the time
Here you can see the reversion waves time has it half ways back to the plenum while the reeds are still closed.

https://gske4w.dm1.livefilestore.com/y2 ... se%202.png


Timing of the pulse wave set by the length of the tube introduces the wave to the chamber as the reed opens, adding velocity to push the almost stalled inlet stream (red). With the inertia wave more air is introduced than the motor can otherwise draw on its own because it is starting at a velocity equal to what is created 1/3-1/2 of the time into the standard intakes draw, basically its "supercharged". The Pulse system works from idle to high rpm and close to wide open throttle positions since its re-introduction point is post throttle valve. Commonly the engines will not draw fuel consistantly through the rpm range because of the reversion strength, The pulse equipped motors will continue to draw consistantly and evenly to extended rpm ranges not accessable without pulse induction. Intake tempatures are reduced since additional single metered air is aquired and engine tempatures are reduced significantly to where it is reccomended to run a heat range hotter spark plug than normally used.

https://gske4w.dm2302.livefilestore.com ... se%203.png


I've done my best to explain this, I expect questions and have no problem answering them.
Adam Millar

[eskimojoe77]

I know you were thinking about pulsing a smart carb, but had expressed some hesitation. I am waiting on my 38mm cast version to show up and am curious about the pulse system in conjunction with this carb. My riding will mostly be with a timbersled snow conversion kit here in Alaska. Curious if you would recommend pulsing this carb.

[Roostius_Maximus]

I'll be working on pulsing it.
Colum reddy has modified a carb, I haven't had time to run it. Damn near done the season here too.

[boostdoctor]

I appreciate your explanation. Next question. Is this technology available to the public? I'm very interested. I'm using a 44 lectron on meth.

[Roostius_Maximus]

I'll get you the info for how the 44 we did is set up.
It went to the salt flats, but the intake pointed directly in, not angled.

[boostdoctor]

thanks buddy.

[Bronson]

Wow. Thanks for the knowledge Roostius_Maximus. Now I've got plenty of reading to do this week while at work