Intake pipe reducer's

P

PikledBeats

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Apr 19, 2010
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So question for the day I guess as it seems more and more lately I have at least one, this one involves air flow into the carb with after-market setup.

So I have drawn up two diagrams to explain what I am asking. But my question is as follows; Does the taper of the intake pipe reducer from an aftermarket airbox matter. I know airflow matters greatly coming out of carb into engine but as far as the airbox side does it?

So does an intake pipe reducer that tapers quickly such as this: see "Setup 1 diagram" act diffrently from a long tapered one such as , see "setup 2 diagram"

2dkwgno.jpg


2zhpiys.jpg
 
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NEONNIGHT34609 said:
i would say setup 2 would be better it would be more of a gradual flow into the carb.
Click to expand...


That is one theory i've already considered, but is it a gradual flow? or does the carb itself control the pull of air regardless of taper in which case the other theory, that if the carb is directly in the airflow, it will pull maximum air in the way it was intended without the airflow being effected/directed/hindered by the taper. This theory came from a discussion I had in the chat. But I don't know, that's why I am asking. I am hoping someone who fully understands airflow through the carb and how it pulls air will chime in. I appreciate the thought though as I am looking for answers.
 
i know most if not all Velocity Stacks are tapered. that is KINDA what you have going on in your second setup. i see this happening with the first setup and maybe even making a swirling vacuum when it hits the hard angle. i might be wayyyyyy off here but its just my input
2dkwgno.jpg
 
NEONNIGHT34609 said:
i know most if not all Velocity Stacks are tapered. that is KINDA what you have going on in your second setup. i see this happening with the first setup and maybe even making a swirling vacuum when it hits the hard angle. i might be wayyyyyy off here but its just my input
2dkwgno.jpg
Click to expand...

I appreciate the input, it atleast starts the discussion and I might end up with a good answer before this thread dies.....lol. And I can see this theory as well, now even more so I'd like to get a definitive answer. I:I
 
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i say number 2, same as a direct bolt on pod filter is hard to tune, versus one with a velocity stack being easier to tune, as the air has time to straighten out

but i would theorize that it's the filter causing the turbulance ?????,
and by the time the air reaches the reducer from a cfm style airbox, it has already straightened out, same as the velocity stack provides to the unboxed pod filter
 
slickerthanyou said:
A more gradual taper Like #2 diagram, would increase velocity more IMO, as it is a smoother transition.

The Number 1 diagram leads me to believe that the air charge would bounce decrease velocity, but Not an expert!

EDIT: I was reading this the other day, not sure if it would relate to our 2-strokes motors but was interesting non the less...

http://http://www.enginebasics.com/Advanced%20Engine%20Tuning/Intake%20Runner%20Length.html
Click to expand...

I actually tried to read, links broke though. Ok, so I actually want to find this out. My initial thought was yes, tapering it smoothly would be best but on the other end as well. If not riding in weather, a pod-filter is the best intake for a blaster. A pod filter justs pull air everywhere. So the issue really stems to how it pulls down the air box tube. Most aftermarket air-box's for blaster have bend around shock. Does air bounce already in these bends? Wouldn't those be worse than the taper. If you are running an aftermarket airbox and you have any carb smaller than a 34mm you will have a taper. CFM and PB are exact opposite. A CFM is a short steep taper maybe even stepped on inside and a PB is not, one long taper. PB usually has quality hands down but is this even a considered issue or just a manufacturing diffrence. Since I am buying a air-boot right now i'm curious. But also because now I really want to know the principle of the airflow as it enters carb on the blaster and if the taper even effects it.
 
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large diameter at the filter like 5" and tapering down to the carb is the ticket. Look at the 250r's and dirt bikes. There's some big time builders that say the same thing.
 
I'm glad you chimed in AWK, I was going to order one from the site you gave me and was concerned that it would taper like the cfm which when I looked at the one I got from them (I thought I chucked it) I was right, it's actually stepped inside.

And Awk, are those measures by actual inside diameter?

Regardless, So we have determined that a taper is what is preferred, Now how much difference will it make with the amount of airflow you are taking in with say stock - 30mm carb, as these will all taper but are not carbs typically used for large motor mods/racing?
 
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Saw your post earlier but had to finish kicker spring, LOL.
Think of it like a lane closeure for construction on the freeway. If everyone merged a mile before the lane ends nobody would have to slow down, but if you wait until your lane ends, you might have to stop or slow considerably, the guy in the other lane has to slow to let you in. Gradual, smooth transitions are always best, even tho the stock airbox tube isn't perfect you'll notice it tapers gadually and doesn't have sharp turns.
The most perfect aerodynamic shape is a rain drop.
 
^^^ man larry i was just about to post the traffic jam scenario... lol also by making the abrupt change in diameter right there you are creating pockets which could do many unforeseen things to the airflow directly before the carb
 
the siliconintakes.com reducers i and a few others use do not step but kinda gradually taper, there are no sharp edges inside them
and the measurements on the website are actual measurements
my cfm box to my 34mm pj requires a 2.5" x 2.25" reducer and it fits great,
i won't run anything else
 
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Ok, sound reasoning. The traffic scenario makes sense and Is what I figured to start, I think I was more curious if it really made a difference. The reason I say this is, is because CFM's tapered reducer actually steps inside. It also doesn't seal but this is possibly because it is an intake pipe reducer made for plumbing...lol. Ok, so PB makes some nice stuff, I will give them that. I talked to them and they were cool, customer service etc., for one of their intake pipe reducers they wanted 25 bux plus shipping. Somehow this ended up being 37 bux in the lower 48. Not knocking PB but really? 37 bux for a rubber boot. Ok, so AWK not that I didn't have faith but I was just checking all options before ordering. I have one that seals great but is a steep taper so I'm going to order one from your suggestion. Thx all for the input...It really makes me wonder why CFM would give such a sh*tty reducer as it seems it would defeat purpose if it really is detrimental to airflow...

Intake Pipe Reducer
 
So the airboots from the site AWK originally posted and I reposted are awesome quality and pefect smooth taper.....they are accurate by I.D. and very high quality. definetly as good or better than PB and 15 with ship rather than 37 from PB. hmmmm......and I wonder why I've never bought anything new from PB what a rip-off.
 
I know this is a little off topic but relevant. air flow is everything resently when i had my kids bike dyno'd the gut who tuned it asked me if i wanted to see something cool? Of course! i run a k&n pod filter with outer wear on it, he removed the outer wear and did another dyno run WOW it picked up .5hp from the last run everything else was same un touched! just the outer wear changed how the engine breathes! i was and still am amazed!
just something else to keep in the back of your mind about air flow!!!!
 
R&S Polishing said:
I know this is a little off topic but relevant. air flow is everything resently when i had my kids bike dyno'd the gut who tuned it asked me if i wanted to see something cool? Of course! i run a k&n pod filter with outer wear on it, he removed the outer wear and did another dyno run WOW it picked up .5hp from the last run everything else was same un touched! just the outer wear changed how the engine breathes! i was and still am amazed!
just something else to keep in the back of your mind about air flow!!!!
Click to expand...

PB uses an outerwear, the CFM has a lid that is open on sides, but many ditch it for outerwear. I'm actually glad you posted this because in theory that would make the lid with it's open sides better than running an outerwear, though i do believe if you run open airbox it is a necessity if riding in wet areas.

I would not think it hindered but that sh*t adds up. If you run an o-ring chain you also rob .5hp so with outerwear that is 1 hp. with stock motor that if I remember correctly is only 13hp ....well you can see how it adds up. The yamaha dealership here has a dyno, as soon as I get as tuned in as I can I am going to run it and see if we can get jetting perfect and get accurate HP. I willl have to test both lid, outerwear, and just open.
 
Pic of intake pipe reducer I went with, I will use some steel straps but did not want them in pics so you could see taper of reducer

Way improved over stock CFM plumbing reducer in Seal/quality/and staying on topic....taper

2rq0i6u.jpg
 
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