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Likes to race old junk.
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Discussion Starter #1
Does anyone know what the Coefficient of Drag and Frontal Area are for a first gen 1100?

Thanks,
Scott
 

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When I was tinkering with DIY dyno software I was looking for drag co-efficient and front area information. Can work out the frontal area easily enough, but drag co-efficient I couldn't find anywhere and afaik you need a tunnel to test for?

However, I did manage to find a similar analogue for my 1st gen 750 with only top fairings on. An article that had wind tunnel testing did a Bandit 600.

"Next in the tunnel was a half-faired Suzuki Bandit 600, which produced a CDA of 3.94 ft2 (0.366 m2 )."

So if the Cd*A = 0.366m2 and I calculated my 750's frontal area from a photo at ~0.427m2 (which for all intents is similar to the 600's size wise)

CD = 0.366m / 0.427m = 0.857 unless I'm hopelessly wrong.

Anyhow, thats going to be super rough since the bandit in question had different shaped front fairing (lights etc) - and I'm guessing you want better accuracy. Using those figures I managed to get a ballpark figure for RWHP for my bike with GSF Dyno.

Seems reasonable when

Busa Cd = 0.561
ZX12R Cd = 0.603

Both of those have a much more aerodynamic shape and design, an 1100 I would imagine would have a bit more frontal area but I wasn't exactly 100% precise when I was doing it ;) .

http://www.sportrider.com/tech/146_0106_aero/index.html


A simple check with the ZX12 full figures in the article seems to make sense:

Drag coefficient CD = 0.603m
Front Area A = 0.566m
Effective Drag Area CDA = 0.341m

So CDA / A = CD

CD = 0.341 / 0.566 = 0.6024m


GSF DYNO using CD of 0.85, Total weight with rider of 280.2kg, Frontal Area of 0.427m, Rolling Friction Coefficent of 0.015, Gear ratio of 8.61 (3rd gear 750), 18" tyre circumference 2.096m, temp 21c, 1007mbar pressure, with three 3rd gear audio recording runs spat out the stock 750 + can + unifilters with stage 3 FP kit a repeatable but rough 82RWHP average which is ballpark I would imagine for my tired bike. :) (what can I say, dynos are few and far between around here and $$ for time haha).
 

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Likes to race old junk.
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Discussion Starter #5
Thanks FrootLoops,

I was just curious if anyone had any old data that had been saved, thinking perhaps that maybe someone knew a team who'd had one in a tunnel back in the day.

I've got lots of info for my Busa including how it sits lowered and with a longer tail.

Airtech has built me a pretty cool body for the twin engine bike and I'll plug in the numbers as fitted to Kent's electric bike.

I do entertain the idea of taking my '86 1100 back to the salt just for shits & giggles.
 

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When I was tinkering with DIY dyno software I was looking for drag co-efficient and front area information. Can work out the frontal area easily enough, but drag co-efficient I couldn't find anywhere and afaik you need a tunnel to test for?

However, I did manage to find a similar analogue for my 1st gen 750 with only top fairings on. An article that had wind tunnel testing did a Bandit 600.

"Next in the tunnel was a half-faired Suzuki Bandit 600, which produced a CDA of 3.94 ft2 (0.366 m2 )."

So if the Cd*A = 0.366m2 and I calculated my 750's frontal area from a photo at ~0.427m2 (which for all intents is similar to the 600's size wise)

CD = 0.366m / 0.427m = 0.857 unless I'm hopelessly wrong.

Anyhow, thats going to be super rough since the bandit in question had different shaped front fairing (lights etc) - and I'm guessing you want better accuracy. Using those figures I managed to get a ballpark figure for RWHP for my bike with GSF Dyno.

Seems reasonable when

Busa Cd = 0.561
ZX12R Cd = 0.603

Both of those have a much more aerodynamic shape and design, an 1100 I would imagine would have a bit more frontal area but I wasn't exactly 100% precise when I was doing it ;) .

http://www.sportrider.com/tech/146_0106_aero/index.html


A simple check with the ZX12 full figures in the article seems to make sense:

Drag coefficient CD = 0.603m
Front Area A = 0.566m
Effective Drag Area CDA = 0.341m

So CDA / A = CD

CD = 0.341 / 0.566 = 0.6024m


GSF DYNO using CD of 0.85, Total weight with rider of 280.2kg, Frontal Area of 0.427m, Rolling Friction Coefficent of 0.015, Gear ratio of 8.61 (3rd gear 750), 18" tyre circumference 2.096m, temp 21c, 1007mbar pressure, with three 3rd gear audio recording runs spat out the stock 750 + can + unifilters with stage 3 FP kit a repeatable but rough 82RWHP average which is ballpark I would imagine for my tired bike. :) (what can I say, dynos are few and far between around here and $$ for time haha).

Just thinking off the top of my head, if you have a dyno run and a top speed run where you top out (stop accelerating) due to horepower you can calculate the overall drag.

Hp loss due to Aero drag is:

Hp = Drag x V = (Q x Cd x A) x V ; Q = 1/2 rho V^2 ; rho is air density

(Q is dynamic pressure in case your wondering)
(V is velocity)
(A is frontal area)

Cd = Hp/(Q x A x V)

Keep your units straight :nono

You should be able to get pretty accurate estimate for Cd assuming 15% total losses for avaliable hp at RW.

Cd = Hp(1-0.15)/(Q x A x V)


BTW Cd is unitless it is the ratio of Drag force to the avaliable force in the fluid. Think of it like the ratio of the drag that your bike really has as compared to the drag it would have if it was a shoe box of same frontal size.
 

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Thanks posplayer, I don't pretend to know what I'm doing with maths and aerodynamics :frantic Thanks for explaining Cd, hopefully Beairsto can come up with something for his awesome racers :cheers

It sounds like you've got it all down pat :)
 

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Thanks posplayer, I don't pretend to know what I'm doing with maths and aerodynamics :frantic Thanks for explaining Cd, hopefully Beairsto can come up with something for his awesome racers :cheers

It sounds like you've got it all down pat :)
I'm an engineer and have done the calcs a few times :twitch
 

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The other OG
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so it's a '57 in Aerodynamics ?
 

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Likes to race old junk.
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Discussion Starter #10
so it's a '57 in Aerodynamics ?
Yeah, like a '57 Buick!:lol

Bikes tend to suck aerodynamically because they are not long enough to clean up the air behind them, the air never gets a chance to re-attach and the subsequent turbulence results in drag.

A stock Hayabusa has a Cd of .561 and 6.01 feet of frontal area. There are modern cars with a Cd as low as .3
Some streamliners have a Cd as low as .103 and only a few feet of frontal area.

From a land speed racer's perspective I liked the direction that Suzuki went with the SRAD models and the first gen Busa...big tails. Slippery in a straight line doesn't always translate to quick handling so there has been a shift in the last few years towards "origami" shaped moto gp bikes which in turn, spawn the replicas.

Initially, I ran the first gen competition fairing on the twin engine bike simply because I thought it looked cool and it showed off the engines. I could have bolted on a Busa fairing but there's enough of those down there already. FYI, there are smart Harley guys running Busa fairings and I know of some Kawasaki's as well.

This year, I will be running a copy of the fairing that Kent Riches designed for the Air Tech / MDR electric bike. There will be alot of fabrication involved and we will have to stretch it because the Double is obviously longer than the e-racer. The SCTA has recently relaxed some of the rules concerning tail height and length, this rule change has resulted in higher speeds, however the bikes are even more unstable in cross winds.

Posplayr & Fruit Loops, thanks for your input! :cheers

-Scott
 

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Yeah, like a '57 Buick!:lol

Bikes tend to suck aerodynamically because they are not long enough to clean up the air behind them, the air never gets a chance to re-attach and the subsequent turbulence results in drag.

A stock Hayabusa has a Cd of .561 and 6.01 feet of frontal area. There are modern cars with a Cd as low as .3
Some streamliners have a Cd as low as .103 and only a few feet of frontal area.

From a land speed racer's perspective I liked the direction that Suzuki went with the SRAD models and the first gen Busa...big tails. Slippery in a straight line doesn't always translate to quick handling so there has been a shift in the last few years towards "origami" shaped moto gp bikes which in turn, spawn the replicas.

Initially, I ran the first gen competition fairing on the twin engine bike simply because I thought it looked cool and it showed off the engines. I could have bolted on a Busa fairing but there's enough of those down there already. FYI, there are smart Harley guys running Busa fairings and I know of some Kawasaki's as well.

This year, I will be running a copy of the fairing that Kent Riches designed for the Air Tech / MDR electric bike. There will be alot of fabrication involved and we will have to stretch it because the Double is obviously longer than the e-racer. The SCTA has recently relaxed some of the rules concerning tail height and length, this rule change has resulted in higher speeds, however the bikes are even more unstable in cross winds.

Posplayr & Fruit Loops, thanks for your input! :cheers

-Scott
I imagine extending that tail section aft to reattach the flow might be a bit tricky with rear tail wobble.

Have you worked on any flow control techniques. Leading edge slats shaped to either side might reduce separation with out adding much side area or weight. Slats help redirect the flow around the blunt bluff body shape of the fairing.

fairing aerodynamics will certainly be critical. Anybody do any wind tunnel testing? Assume they must.
 
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