Engine Air Supply

DAG

DAG

Yes, my balls tickled from that landing
Location
Charlotte, NC
With more and more aftermarket hulls being made without hood liners, the only source of air is thru the handle pole. Has anyone experimented running 1000cc or larger displacement motors in a Chan, Foot Rocket, Rickter, exc. with only a XMW pole feeding the engine bay.

To give an example a XMW pole has a square opening of .800" x 3.750" giving an area of 3 sq in.
A RRP tube has a diameter of 2.311" giving each tube 4.19 sq in, for a total area of 8.38 sq in. nearly 3 times the volume of a tube pole setup.

Would you benefit switching from XMW to a tube style pole on hulls without other sources of air intakes? Would it effect tuning? Or am I just over complicating things


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Tyrant1919

Tyrant1919

Site Supporter
Location
Washington, DC
lets say you have 48mm carbs. lets make that 1.88976in carbs for sake of units :^).

1.88976in would be the diameter, 0.94488in would be the Radius.

Good old πr²

0.94488 * 0.94488 = 0.8927982144
0.8927982144 * 3.14 = 2.803386393216
2.803386393216 * 2 = 5.606772786432 in²

with that opening of 3in², you can't even cover the area of your carbs.

Would it actually matter? I want to say yes. But I have no hands on experience with this issue.
 
Brian_216

Brian_216

Location
Harveys Lake PA
Ill say my 1105 would not work right with an atp pole on 2 tubes. It needed 4 breather hoses in the hood liner along with the pole tubes.

Sent from my SAMSUNG-SGH-I337 using Tapatalk
 
IS0LD0UT

IS0LD0UT

I hate winter
Location
MN
Wondering the same thing. I asked about it on the chan and the hood can be modified (waiting on pics) was told it was run with a 900 with just the xmetal breathers.
 
TontoM3

TontoM3

Manager of Gnar Shredding activities
Location
Lake of the Ozarks, Missouri
From a math stand point it makes sense to have a more than is provided because the engine won't work as hard to provide the power. However with all the water that you get coming in a stock hood it would negate a lot of that 'extra' air. I don't have an aftermarket to compare but in my head I would think you would design the hull for minimal water in the bay, just enough air for a modified engine to work with.
 
speedysprocket

speedysprocket

Alex
Location
Chesapeake, VA
I ran x metal pole on my Foot Rocket at first with my 950 and 46mm Novis. Anything past idle, and there was so much vacuum in the engine compartment, you had to really pull to get the hood open. Probably 1/3 throttle or more and it was not possible. Also covered the whole engine compartment with a film of 2 stroke oil, probably coming out of the carbs when letting off the throttle.
Switched to RRP and there is less vacuum, though still noticeable, and the oil film has gone done significantly. I also switched to 48s when I put the RRP pole on.
Morale of the story is that big engines need big air. I didn't put the bigger carbs on until the pole was on because I knew it couldn't breath enough as it was- bigger carbs wouldn't help anything.
For free ride, this probably isn't as big a deal as racing though. We're only trying to suck the maximum volume of air for very short durations at a time. I would expect it be much more detrimental to performance when the throttle is wide open for longer periods of time.
 
DAG

DAG

Yes, my balls tickled from that landing
Location
Charlotte, NC
Ok let's not get to far off topic with the wild solution theory's. This thread is to discuss facts. Surly someone has drop a 1000 in a chan and ran a XMW pole that could chime in?
 
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