Variable runner intake

[Traumahawk]

Thank you for posting up all of this info. I'm one of those people that thinks that new things ALWAYS need to be tried.....even if they dont work. You can learn a lot from your failures.

 

[Craigster]

Thank you for posting up all of this info. I'm one of those people that thinks that new things ALWAYS need to be tried.....even if they dont work. You can learn a lot from your failures.

I'm glad you enjoyed reading the results. I've had the good fortune (I'd say pleasure, but sometimes it's torture) to work with some very innovative people / teams. As one owner said, "It's not about buying the same thing as everybody else when you're racing at the top level. It's about solving problems faster than the next guy."

I once worked with a national level Harley Davidson NHRA PSB team. This was back before the Vance and Hines V-Rods attempted to run in the class. There were only two HDs in NHRA Prostock Bike back then, so if you're knowledgeable, you know who I'm talking about. The engine design was completely foreign to all other Racing H-Ds at the time. No one was trying to make 300 hp on gasoline with a 45 degree twin. The team had been through several different fueling and intake set-ups. Originally it had a tunnel ram intake with a 4 bbl Holley Dominator on it. Various CFM carbs were used from 600 to 1050 CFM. Nothing changed the fact that the bike nosed over going down the track and lost power on the big end. Later a new head and intake was employed using 4 individual Lectrons just like the Suzuki's. In this case each intake valve had it's own carb feeding it. The the new heads flowed 100 cfm more than the old design - the bike should have been flying, but still the dreaded nose over. Redesigned fuel systems were employed at great expense. Still no fix for the low mph.

As I stood beside the bike on the starting line one day I saw it. The carbs were shaking. Not weaving and bobbing about like the carb on the typical 5000 to 6500 rpm HD drag motor, but this guy's 10,000 rpm engine was 'buzzing' the carbs. I theorized a concave meniscus was shaping up at high rpm. The floats raised and closed off the needles to the seats as the outside of the bowl had a high fuel level. The middle was a deep dish, starving the main jet for fuel. The Suzukis and automobiles, don't shake like that, so neither carb design we employed had the built in fuel damper for it. Typical HDs have a carb hanging out the side that can damp fuel slosh and work around it, but they too, have never been asked to deal with it at this bike's rpm.

I told the owner my theory and built him his first EFI ECM and we adapted the Lectrons into throttle bodies for the EFI. Problem solved. And 10 extra mph showed up on the time slip.

The point is, you try something new and there's no one to call when you're not buying something out of a catalog. It can also be a big pile of failure after failure, but when you solve the problems, it's amazing and very rewarding.

The guy with the V-Max variable runner system wasn't a racer, just a very talented machinist with a friend who was an electrical engineering manager and hired gun automotive EFI calibrator. They didn't build it to win races. They just built it because they could. I loved the fact that the variable runner plot overlayed so well with the fixed runner plot. It's been saved in my files for years.

Every now and then I come across something that makes me smile and that was one I was hoping would be interesting to others as well.

 

[Craigster]

Long stacks down for low end power

 

[Craigster]

Long stacks up, exposing short stacks for top end.

 

[Craigster]

The mechanism

 

[one2dmax]

Looks like he used the vboost servo motor. I like the entire thing! The stacks look similar in size to the stacks I have on my methanol hilborn mechanical injection setup.

 

[[email protected]]

Very interesting! You have any other shots of the bike?

 

[Traumahawk]

You know....that with something like the ignitech controlling it, you could change the length of the runners, at any RPM that you choose.

 

[adambweird]

Someone send a link to this thread to jedi!

 

[V4ever]

This is cool stuff!
I've been collecting pieces to play with a turbo build. I know this isn't an actual turbo build thread but any idea if variable length runners respond the same under boost or would plenum volume come into play, more?

 

[bazwell]

This is just cool! Nice one Craigster. I learned something today!

 

[jedi-]

Thanks for posting, engineering prowess at it's best.

 

[one2dmax]

This is cool stuff!
I've been collecting pieces to play with a turbo build. I know this isn't an actual turbo build thread but any idea if variable length runners respond the same under boost or would plenum volume come into play, more?

Since the turbo pressurizes the intake the overall effect will be reduced. The stacks really make more help to a standard vacuum based engine.

Sean

 

[Craigster]

My mistake. The machine was actually a 1993 not a 1992.

Here you can see the EFI throttle bodies in place of carbs with injectors peeking out, the elevated "tank" cover to clear the air filter and the horrible Innovate Air Fuel monitor in the pipe and controller on the tank. I tried to convince him to spend the bucks on something better, but he liked the data logging the Innovate supplied. They work, but they are not the best IMHO. He did build a clever air pump to extract the exhaust gas at low rpm/throttle position and pull it by the sensor. I really liked that part. Very ingenious guy.