Gearing

[cubicincubi]

Hi folks.

I'm pushing 167.8 at the RW with my K6 USDM to UK import. Usual stuff, airbox gutted and flapper ripped out and sealed, pair valve dumped, K&N, Air sensor moved up the intake and a pair of growler racefit cans. All I've left to do is cut out the cat and sleeve the pipe (I thought USDM Busa's didn't have a CAT?) to hopefully push it a smidge over 170hp.

Got a few questions.

I'n this guise I've ran 17/43 - smashed thru the RPM's quickly, nice and fast and ran out of steam early, bouncing off the limiter 11,500rpm at 180mph thru digital trap. Drank the tank very quickly. Then I tried 17/39 - fast in the mid range, didn't seem to want to pull past 10,500 in 6th (need more power) and topped out at 187mph. I'm 168lbs, and I'd really like to see if I could steal 200mph in the class 2 flyer events with just bolt ons... I reckon with enough attempts on the right day I could do it.

If I go for a 16 front, will a 16/40 combo give me my maxxed out top speed? And I was assuming that 16/43 is going to give me the best 1/4 for the bike in it's current guise, but is it very aggressive? more aggressive than 17/43? As I don't want to eat my standard clutch prematurely.... so would a 16/42 be better?



etc etc etc....

Shared experience appreciated.

Thanks

 

[rubber2burn]

From what I understand from allot of the tuners here is that you need 200 hp at the rear in order to do 200mph so you might need some moter work before you break that 200 MPH barrier

 

[Shibumi]

If this is any help- gives you a basis for comparison. Obviously the lower the final drive ratio the higher the terminal velocity, if the HP is there. With stock gearing and tire mine hit the limiter at 194 on the dyno, if that helps any. So NOTHING in a 16 tooth front will get you there...


Gear Ratio Calculator

Front Rear Final
16 39 2.44
16 40 2.50
16 41 2.56
16 42 2.63
16 43 2.69

17 39 2.29
17 40 2.35 Stock
17 41 2.41
17 42 2.47
17 43 2.53

18 39 2.17
18 40 2.22
18 41 2.28
18 42 2.33
18 43 2.39

 

[cubicincubi]

so I need 18/40/39 then for flyers and 16/42/43 for qtrs.

And perhaps a 17/43 is a good compromise for the street.

Does that sound about right?

I've just ordered a 16 & 18 front renthal...

I've got 38/40/43 rear.... I might buy a 39 and 42 rear aswell to have in my kit while at the track if you guys reckon it's worth having the choice.

 

[Shibumi]

I'm betting with a 16/40 even, you'll have a gas tank print in your forehead in first and second and maybe a hard shift to third!!

Seriously, I weigh about what you do and much bigger guys than us get wheelie-happy when they go to a 42 or 43 rear with 17 front. You'll be fighting to keep the front end down on the 1/4 action. Maybe Professor will chime in here, he's the PMRA champ locally...

 

[cubicincubi]

Well on saturday I had 45psi rear and 42 psi front (for flyers) but the airstrip event measured our qtr time, kilo time and finally top speed time thru the flyer speed trap. then our points were calculated based on best times in the 3 sections of each run. I must admit running 17/43 it was hard getting traction runing so high PSI in the rear, but I needed such for the flyer - spining up at 9K rpm in 1st and second but pinned it to 11,500rpm in 2nd all the way to 6th with no real drama except some sideways spinning for a few moments. All my weight forward, chin on the tank.

But I was there to get my top speed up and to crash through the gears at the redline and experience running different gears. Talking about it is one thing, but feeling it for yourself and finding what suits you best is another thing. Dragging the busa on a standard clucth won't do for now - I'll make my points up covering the kilo and flyer where the qtr geared guys will lose points.

The Busa is a pretty addictive machine, it's got so many talents

 

[Shibumi]

Good on yer for getting out there and flogging it!!

Better get ready to spend more money for clutches, tyres, etc...

 

[frisbee]

Doing 200 is a feat with only 170hp . I don't think its been done . And the gearing will have to be changed a 16 in the front drops your top end . thats what we use for drags. You want an 18/38 to do some good top speeds and you will need more HP to get it going with that gearing up at the top end . Alot of people think its easy to do 200 but it aint. Good luck , at least you are light enough to not need all the hp some of us do.

 

[frisbee]

(cubicincubi @ Sep. 03 2007,19:56) so I need 18/40/39 then for flyers and 16/42/43 for qtrs.

And perhaps a 17/43 is a good compromise for the street.

Does that sound about right?

I've just ordered a 16 & 18 front renthal...

I've got 38/40/43 rear.... I might buy a 39 and 42 rear aswell to have in my kit while at the track if you guys reckon it's worth having the choice.

sounds right I had a 17/43 and then when I stretched it I went 16/43 . Fun Fun !

 

[Commuta_Busa]

180hp and a huge tail wind may get you close