PVC pipe as velocity stacks? - Ducati Monster Forums: Ducati Monster Motorcycle Forum
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post #1 of 13 (permalink) Old 03-26-2007, 05:53 PM Thread Starter
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PVC pipe as velocity stacks?

So I got the idea to use 90 degree PVC elbows as a velocity stack between the carbs and K&N cone filters. I liked the look of the K&N air filters, but didn't like how they were tucked up under the tank. Using the elbows, I can have the filters angle down and are much more visible thru the frame. My question is will using the elbows cause any problems? They are smooth inside, but do make a sharp bend. Do I have to worry about this effecting the performance Thanks in advance!

Brett
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post #2 of 13 (permalink) Old 03-26-2007, 06:12 PM
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Re: PVC pipe as velocity stacks?

i say go for it... worst case you just take 'em off again :-D
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post #3 of 13 (permalink) Old 03-26-2007, 07:41 PM Thread Starter
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Re: PVC pipe as velocity stacks?

Yea, I will if no one tells me it wont work. The thing is the K&N filters I will be using are different then the normal ones people use. So if it doesn't work, I will have to get new ones and be out $70. But I guess thats the price you pay to be different.
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post #4 of 13 (permalink) Old 03-26-2007, 08:00 PM
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Re: PVC pipe as velocity stacks?

It's my understanding (just based on what I've read elsewhere) that PVC gives off toxic fumes when heated. Not saying that's for sure, but something you might want to investigate before risking your life.

regards
P
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post #5 of 13 (permalink) Old 03-26-2007, 08:33 PM
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Re: PVC pipe as velocity stacks?

Quote:
Originally Posted by Privateer
It's my understanding (just based on what I've read elsewhere) that PVC gives off toxic fumes when heated. Not saying that's for sure, but something you might want to investigate before risking your life.

regards
P
+1

It is plastic.

However, are you really sticking your nose on the velocity stacks or on the exhaust?

I would be more concerned about what those fumes might do to your engine and pipes
post #6 of 13 (permalink) Old 03-26-2007, 10:41 PM
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Re: PVC pipe as velocity stacks?

ain't gonna be too many fumes.

the high pressure air going in will be pretty cold.

not hot enough to make a difference.

try it. take off your airbox and put your finger in front of the carb intake and rev it. gets nice and cool. i would be more concerned about icing, which is what carbs do -- ice.
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post #7 of 13 (permalink) Old 03-27-2007, 01:01 AM
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Re: PVC pipe as velocity stacks?

+1 on not worrying about fumes on the intake side of the carbs - it doesn't get hot until, well... after the spark

And before I go further... stop... you're putting PVC pipe on your Ducati to make it look better??!!

It's just a precautionary step, because I really can't imagine what you're going for... if you still want to continue - here's my only comment of... pseudo advice...

Only downside I've heard about pods - are sensitivity to crosswinds. I guess the upwind side's carb would be getting more air than the other - an issue not encountered when sharing the airsupply of the airbox. If the pods are "more visible" I presume this would increase the opportunity for a performance issue given the right circumstances.

... you don't live in or need to cross Wyoming often do you?

Post pics when your done - try both ways and then take a poll.

Good luck,
-M


"This motorcycle is simply too goddamn fast to ride at speed in any kind of normal road traffic unless you're ready to go straight down the centerline with your nuts on fire and a silent scream in your throat."  ... oh you know who... R.I.P.
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post #8 of 13 (permalink) Old 03-27-2007, 08:14 AM
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Re: PVC pipe as velocity stacks?

my 2 cents....and i think this sounds like a great idea (i built an LED taillight out of PVC)
I would use the electrical conduit PVC...the grey stuff. Not for looks, but because it is fire resistant and shouldn't (notice i said shouldn't not won't) become brittle from the sun's uv-rays. The standard plumbing PVC gets fragile if out in the sun too long.
If you have the regular PVC sitting around, make a prototype to see if it works, then i would switch to the electrical grade stuff.
Then i would be concerned with the smoothness of the interior of the pipe. Little grooves, and pores will create drag and turbulence inside the stack reducing its effectiveness, notice how the velocity stacks are polished on the inside.

good luck and post pics,

RB
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post #9 of 13 (permalink) Old 03-27-2007, 09:44 AM
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Re: PVC pipe as velocity stacks?

I think it has some potential. I've been wanting to build some ram air stacks that sit outside the frame & use a different kind of filter so the air is literally forced in, but, well, I guess I've been too lazy. Maybe this will inspire me to get it done. I wouldn't worry about the xwind thing, I use individual pods on every bike I own and make & have never experienced this problem. Another idea is to put the carbs at the end of a long manifold. I know the short intakes seem to make more power on the 2 valve motors, but during the hot rod days, it was mostly the opposite. Long runners meant more top end & short xovers gave more bottom end. I'm a little confused by all this. I guess the only way to know will be to try it. Make sure you do lots of plug checks to be sure you're not leaning either cyclinder out too much.

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post #10 of 13 (permalink) Old 03-27-2007, 10:25 AM
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Re: PVC pipe as velocity stacks?

Brett,
If you are worried about the sharp turn of the 90 degree fitting, maybe consider a 45 or 22-1/2 degree.

Have fun and post pics.

Moto_Bella
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