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Discussion Starter · #1 ·
OK.. I got some Air Intake thoughts. Lookin for input.

The factory specs for bore and stroke (101mm x 112mm)

I get a volume of 54.7583 in³/cylinder.

.7854 * (101^2) * 112 * (.1^3) * (.393700787^3) = 54.75837050105755872 in³/Cyl.

Converted to ft³ per cylinder:
54.75837050105755872
/ 1728(amount of in³ to 1 ft³) = 0.031688 ft³/Cyl.

So if one cylinder completes an intake stroke on each revolution, then just multiplying by the rpm will get us CFM at the rpm in question right?

RPM * 0.031688 ft³ = CFM

2k RPM = 63 CFM
3k RPM = 95 CFM
4k RPM = 126 CFM
5k RPM = 158 CFM
6k RPM = 190 CFM
7k RPM = 221 CFM

(I went up to 7k because I have read some member(s) run em that high using computer/power commander based ignition control...)

Did I do the math right?
Assuming an generous 85% efficiency, because we all know 100% is impossible. That leaves us with 188 PEAK CFM.... @ 7krpm!!!! So we're pretty much getting 134+ CFM on a stock bike at rev limiter.
Seems like we could get that kinda flow with quite a few different air boxes, even the stocker? My only concern was for the ram air effect, but I figure that would be negligible without boost right?
Anyway, does anyone know the CFMs for the different intakes available and even for a K&N in the stock box w/ the pair mod done? I have money to put into other things for the bike right now(pegs/bars/risers etc.) and am trying to see what my best options were. Thanks in advance.
 

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I feel dumber after reading that. Way over my head. It may as well have been in Latin. Apparently I need to just stick to things that are shiney!
 

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The guitar, not the fish!
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I feel dumber after reading that. Way over my head. It may as well have been in Latin. Apparently I need to just stick to things that are shiney!
Yeah me too!!...He lost me after the bore and stroke......Now I know why I drive a truck instead of work for NASA.....
 

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OK.. I got some Air Intake thoughts. Lookin for input.

The factory specs for bore and stroke (101mm x 112mm)

I get a volume of 54.7583 in³/cylinder.

.7854 * (101^2) * 112 * (.1^3) * (.393700787^3) = 54.75837050105755872 in³/Cyl.

Converted to ft³ per cylinder:
54.75837050105755872 / 1728(amount of in³ to 1 ft³) = 0.031688 ft³/Cyl.

So if one cylinder completes an intake stroke on each revolution, then just multiplying by the rpm will get us CFM at the rpm in question right?

RPM * 0.031688 ft³ = CFM

2k RPM = 63 CFM
3k RPM = 95 CFM
4k RPM = 126 CFM
5k RPM = 158 CFM
6k RPM = 190 CFM
7k RPM = 221 CFM
(I went up to 7k because I have read some member(s) run em that high using computer/power commander based ignition control...)

Did I do the math right?
Assuming an generous 85% efficiency, because we all know 100% is impossible. That leaves us with 188 PEAK CFM.... @ 7krpm!!!! So we're pretty much getting 134+ CFM on a stock bike at rev limiter.
Seems like we could get that kinda flow with quite a few different air boxes, even the stocker? My only concern was for the ram air effect, but I figure that would be negligible without boost right?
Anyway, does anyone know the CFMs for the different intakes available and even for a K&N in the stock box w/ the pair mod done? I have money to put into other things for the bike right now(pegs/bars/risers etc.) and am trying to see what my best options were. Thanks in advance.
Are you shittin me?
 

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Discussion Starter · #6 ·
Yeah me too!!...He lost me after the bore and stroke......Now I know why I drive a truck instead of work for NASA.....
ROFL! I am a metal worker.. I use a lot of math when I have to figure out how to make custom orders, and finding the formula for cubic cylinders was easy. I was just looking to see if anyone had airflow rates for the different intakes such as the BAK,Hurricane, the cone thingy, stock, etc, etc. :icon_writ
 

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Ahhh, I see the 'majic of the math',

(used to use it on car engines to determine max carb cfm needed, "Yeah Luke, those dual 750 double pumpers on your 327 really help it breathe!!!" LOL!!!!)

It IS kinda strange that no manufacturer posts any CFM data on their product.

Info like that would probably put some of those $300 intakes in the 'not so good' catagory!!!
 

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Discussion Starter · #8 ·
Ahhh, I see the 'majic of the math',

(used to use it on car engines to determine max carb cfm needed, "Yeah Luke, those dual 750 double pumpers on your 327 really help it breathe!!!" LOL!!!!)

It IS kinda strange that no manufacturer posts any CFM data on their product.

Info like that would probably put some of those $300 intakes in the 'not so good' catagory!!!
Thats what I'm saying! Thunder used to display CFM for one of their products, but that was a couple years ago...
 

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"So if one cylinder completes an intake stroke on each revolution, then just multiplying by the rpm will get us CFM at the rpm in question right?"

It is a 4 stroke engine; Intake (down), Compression (up), Detonation (down), Exhaust (up). Basically, RPM divided by 2 in your volume calculation will calculate for each individual cylinder. Because each cylinder is alternating the Intake stroke, I am assuming you are multiplying the RPM to get the total for the engine.
 

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Discussion Starter · #10 ·
"So if one cylinder completes an intake stroke on each revolution, then just multiplying by the rpm will get us CFM at the rpm in question right?"

It is a 4 stroke engine; Intake (down), Compression (up), Detonation (down), Exhaust (up). Basically, RPM divided by 2 in your volume calculation will calculate for each individual cylinder. Because each cylinder is alternating the Intake stroke, I am assuming you are multiplying the RPM to get the total for the engine.
thats what I was trying to say.. That one of the cylinders is on the intake stroke every revolution. glad someone else gets it. thanks.
 

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Discussion Starter · #12 ·
With intake and exhaust efficency (or lack of) being the limiting factors....
Precisely why I was padding it @ 85% efficiency to be optimistic. The only reason why I did the math was to see the theoretical/mathematical CFM of engine, so I could choose an intake that wasnt an overkill and possibly in my price range. I dont think people realize how really little air this bike theoretically needs. Kinda why the dual intake doesnt do anything without some engine re-working. I figure any open style K&N filter airbox will do the job. Now I just have to find the cheapest. :cheers:
 

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Lost again...what was the question? Which color is faster? Based on the wavelength of the colors, I would say BLACK...
 

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Discussion Starter · #15 ·
Lost again...what was the question? Which color is faster? Based on the wavelength of the colors, I would say BLACK...
rofl.. I already knew black was the fastest color.... :patriot:
 

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I've heard that the use of a Biddy Baffle helps (with a 1300 carb system) with the turbulence/lean 'spot' some say is created by the Spyker mod.

I believe the Spyker mod combined with a Biddy Baffle is both good looking, functional, and inexpensive! The baffle is just 'icing on the cake'!
 

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Discussion Starter · #19 ·
Anyone have CFM numbers for intakes?
 

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Sorry shiv, math is not my strong point. I wish I could help.

(Check your spelling of Honda on your handlebar info.)
 
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