long ram intake manifolds

[Highside]

Come to think of it, I have yet to see a tracker or cafe XS650 with some kind of racing oriented long ram intake.

In order to get it to have its peak effect at 6500 RPM, it would require that the intake track be 20" long from air cleaner to intake valve.

I was thinking on making my own with some 1 1/2" PVC tubing. Has anyone tried this before??

 

[bobadame]

20", You're kidding, right? I thought long intake tracks worked better for low end torque and high rpm engines use short runners. (?)

 

[Highside]

20", You're kidding, right?

Uuuuuuuuuuuuuuhh, no.

I thought long intake tracks worked better for low end torque and high rpm engines use short runners. (?)

Yes they do.

20" is the correct length to take advantage of the 2nd harmonic pulse @6500rpm.

You can use shorter runners, but they use the 3rd and 4th harmonic pulses, which aren't as strong.

It would be 14.9" for 3rd pulse and 11.38" for 4th pulse.

The advantage to 3rd and 4th pulses is that they aren't as peaky as the second pulse, which gives the engine a bit of a 2-stroke powerband.

I'd like to try it at 20" first, just to see how much power I can get it to make.

It would be pretty cool to get 3-4 HP for $5 worth of PVC tubing.

 

[mrriggs]

My first thought is that the gasoline would dissolve the PVC plastic. I just did a quick experiment by soaking a rag with gasoline and rubbing a PVC pipe. Amazingly, the plastic did not dissolve or even get tacky So it may just work, if only for a few dyno pulls. I'd still be inclined to use copper pipe or some exhaust tubing.

I think the reason you don't see long runners on a bike is simply a matter of packaging. I just measured my bike that has a 3-1/2 inch stretch and a 20" runner would not fit without twisting the tubes around or sticking it out the side. Joe Wiseguy makes a long runner intake that puts the carbs out in front of the engine with the pipes looping over the top of the motor.

If you have the capability then by all means give it a shot and let us know how it turns out.

 

[COOPERB27]

Where does joe wiseguy get those y connectors to join the 2 intake pipes together?

 

[XSLeo]

I think he builds them.
Leo

 

[bobadame]

It would be interesting to try this on a dyno with a trombone slide type of pipe, some kind of thin wall tubing with a good seal between the tubes. I remember that Dodge tried some long tube intake manifolds that crossed over the engine and the 4 barrel carbs were over the wheel wells. This was in the late 60's, 413 wedge engines I think.

 

[bobadame]

Looks like it was in 1960.

 

[gggGary]

Much more recently there have been some variable length automobile intake runners. Can't think of which one but I know I have seen it.

 

[mrriggs]

I bought a cross-ram intake for my Comet. Never got around to building a motor for it so we stuck it on my cousin's Comet since he had a LeMans cammed 289. I don't know if it ran any better but it sure looked cool. and fit under the stock hood.

 

[Highside]

My first thought is that the gasoline would dissolve the PVC plastic. I just did a quick experiment by soaking a rag with gasoline and rubbing a PVC pipe. Amazingly, the plastic did not dissolve or even get tacky So it may just work, if only for a few dyno pulls. I'd still be inclined to use copper pipe or some exhaust tubing.

This would be dry flow anyways, I'd hang the airfilters off of 'em then go to the carbs. I'd prefer to stick with plasic because it insulates against heat well. The cooler the intake charge, the more power, and for $5 worth of PVC tubing.

I think the reason you don't see long runners on a bike is simply a matter of packaging.

DING! DING! DING! We have a winner!!!

I just measured my bike that has a 3-1/2 inch stretch and a 20" runner would not fit without twisting the tubes around or sticking it out the side.

Keep in mind that the 20" starts at the intake valve, you would only need 14" of pipe from there. I think I can fit it by turning up into the tail section of the cafe seat I'm using.

If you have the capability then by all means give it a shot and let us know how it turns out.

My main problem would be finding and paying for the dyno work.

 

[Highside]

It would be interesting to try this on a dyno with a trombone slide type of pipe, some kind of thin wall tubing with a good seal between the tubes. I remember that Dodge tried some long tube intake manifolds that crossed over the engine and the 4 barrel carbs were over the wheel wells. This was in the late 60's, 413 wedge engines I think.

View attachment 11554

This came on a few different big blocks. The 361,383RB, 413 and 426 Max Wedge IIRC.

This design suffered from having to make a 90 deg bend right after the carb.

 

[Highside]

I tried to google search for an image of a Pro Stock Motorcycle enginge (Suzuki GS) with a long ram inkae system. I've seen them at the race track but couldn't find a pic.

Found this instead. This is just too much win!!!

 

[mrriggs]

This would be dry flow anyways, I'd hang the airfilters off of 'em then go to the carbs. I'd prefer to stick with plasic because it insulates against heat well. The cooler the intake charge, the more power, and for $5 worth of PVC tubing.

I personally don't think that added runner length before the carb is going to be as effective as runner length between the carb and valve. I don't have any number to back that up so take it for what it's worth. The mouth of the carb is much larger than the throttle side so you would need a larger diameter pipe which would be less effective. But the biggest problem is that it would only be effective at or near WOT. Alright for drag racing but not very beneficial for a street bike.

Keep in mind that the 20" starts at the intake valve, you would only need 14" of pipe from there. I think I can fit it by turning up into the tail section of the cafe seat I'm using.

I was measuring from the valve but my bike is lowered so it would run into the fender. I hadn't considered a cafe bike with more area above the tire.

 

[Punkskalar]

The longer the runner, the more velocity you are going to lose, so keep the intake runners smaller ID than you might have had planned.... With stock carbs, lost velocity will be a tuning issue, as you need the vaccuum to operate the slide...

 

[angus67]

I tried to google search for an image of a Pro Stock Motorcycle enginge (Suzuki GS) with a long ram inkae system. I've seen them at the race track but couldn't find a pic.

Found this instead. This is just too much win!!!

I remember that bike in a mag quite some time ago, if I remember, those engines are intended for Remote controlled air craft hobby. Rc's are serious business, not just a cheap toy to bother the ex with. Ive got a traxxas jato nitro that ive spent near 1k in hoppups, and replacing a-arms.

 

[jay760]

I always thought the long ram effect worked on the engine side of the carb , not the filter

 

[AussieHard]

any resolution to this?????

 

[Ghetto]

Max Wedge is a pretty serious engine.