mysterious groove in manifold boosts performance?



3 replies to this topic
  • ballistic

Posted January 14, 2002 - 08:29 PM

#1

An intersting article in Jan. DIRT BIKE. They take a CRF450 and with White Bros. help turn the thing into a dirt tracker. Rules state the 40mm Keihin must be restricted to 37mm with a restrictor plate.
They researched and spoke with dirt track and stock car guys for tips on restrictor plates and found that the airflow and turbulence factor is critical . They were told that cutting a small groove on intake mainfold side of restrictor can produce a tiny vortex effect to breathe better. The trick is to make the groove the right width and depth. Then they added a custom W Bros. exhaust. The CRF put out 51 HP... 3 more than the unrestricted CRF.
The bike was said to "hang with a KTM520 in every way." It placed #5 in its debut race.

Anyone with dirttrack experience want to comment? Anyone want to try it out, and report back? :)
Hey... I'll pitch in 5 bucks. If it dont work, fill the groove back in with JB Weld.

  • John_H

Posted January 14, 2002 - 09:05 PM

#2

"Then they added a custom W Bros. exhaust. The CRF put out 51 HP... 3 more than the unrestricted CRF. The bike was said to "hang with a KTM520 in every way." It placed #5 in its debut race."

Rumors are like *******s, everyone has one. May be true, but I really believe that the articles are there to sell articles.

Buyer be ware. If it seems to good to be true, it probably is.

If it works, I'll do it in a heart beat.

Not dogging you, I'm just thinking...

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  • ballistic

Posted January 14, 2002 - 09:20 PM

#3

I'm not siding one way or another. I'm throwing it out here for some scrutiny. The part to zero in on though is swirl groove. They (Dirt Bike) implied/stated that such a thing was well known in the stock car and dirt tracker crowds. Therefore it should not be difficult to confirm the accuracy of the statement. If it IS truly common knowledge, then whats up? I'm saying its interesting and could be worthy of further analysis.

  • Harvey_Mushman

Posted January 14, 2002 - 10:52 PM

#4

Awww the racers secret.. Dont forget that In dirt track 51 HP is only needed in one spot.. All at the top of the rev range.. So peak HP may be 51 but I bet the torque curve sucked...




 
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