Lets talk Sprockets

[Elganja]

I've been trying to figure out what sprockets to go with to maximize my acceleration. My application is drag racing.

Got-Busa? posted a link a while ago that allows you to plug in your bikes info to get some numbers (i.e. max speed in 4th, 5th, etc...). The link Got-Busa? posted was Gearing Commander. I filled in the info there from Dixon Archive. I've also requested the 08 Hayabusa, with the info I found, be added to Gearing Commander.

Here are the combinations that seem to be popular:

18-43 (Click Here) *STOCK*
<ul>
[*]4th gear @ 11,000 RPM = 263 km/h = 163.42 mph
[*]5th gear @ 11,000 RPM = 298 km/h = 185.17 mph
[/list]
17-43 (Click Here)
<ul>
[*]4th gear @ 11,000 RPM = 249 km/h = 154.72 mph
[*]5th gear @ 11,000 RPM = 281 km/h = 174.60 mph
[/list]
17-44 (Click Here)
<ul>
[*]4th gear @ 11,000 RPM = 243 km/h = 150.99 mph
[*]5th gear @ 11,000 RPM = 275 km/h = 170.88 mph
[/list]
17-45 (Click Here)
<ul>
[*]4th gear @ 11,000 RPM = 237 km/h = 147.26 mph
[*]5th gear @ 11,000 RPM = 269 km/h = 167.14 mph
[/list]

I've been trapping at around 152-153 mph (well 152.85 being my highest so far). I've been struggling with a couple things. One, should I even change my sprockets? But the even better question, is the extra gear worth having to shift into 5th gear? I suppose I could just do 17/43 or 18/46 to max out 4th gear theoretically (I say theoretically because it seems like I am damn close to hitting the limiter already in 4th).

Basically I need some advice! GPW? Professor? Mr. Bogus? Cdi? Got-Busa? FLASHRACER? MoPrac? I know there are a bunch of drag racers out there who can lead me the right way!

 

[Professor]

Based on those numbers, I would try the 17/43. You might find it more violent on the launch however and have to step back.

 

[Elganja]

Based on those numbers, I would try the 17/43. You might find it more violent on the launch however and have to step back.

thanks for your input. I went ahead and ordered a Vortex 17T one. I never realized how cheap they were.

I'm pretty excited to try it out this Friday. I even went home and took the stock one out to get ready for the new one LOL

 

[TruWrecks]

17/43 will give you more torque at the wheel. Get use to the extra power before you take it to the strip. You don't want to find out the hard way that your Busa has just become a serious wheelie machine.

 

[Elganja]

17/43 will give you more torque at the wheel. Get use to the extra power before you take it to the strip. You don't want to find out the hard way that your Busa has just become a serious wheelie machine.

I'm extended ~3.5-4inches which should help a ton for the wheelies.

I did overlook something though in my calculations. I used 11,000 rpm as the determinate, I think that was a mistake. I should of used my shift point of 10,950. Should be interesting at the track on Friday.

I'm going to set my dynojet HUB to 10,990 RPM. What I don't know is:
A. how much time it takes to go from 10,990 to 11,000 rpm (varies by gear of course)
B. How much time it takes the HUB signal to reach the kill box

If B < A then I am golden, otherwise I will hit the rev limiter (if it is truly 11,000rpm)

Hopefully the autoshift can shift faster then it hits the rev limiter (although I don't think it will matter either way).

 

[TruWrecks]

My dyno sheet from last weekend show the rev limiter at 11,300 for the hard cut off. It does show a drop in power at 11k, like a soft limit. You may want to lower the hub RPM a bit more.

 

[Elganja]

My dyno sheet from last weekend show the rev limiter at 11,300 for the hard cut off. It does show a drop in power at 11k, like a soft limit. You may want to lower the hub RPM a bit more.

it's almost like a catch 22 here.

Currently I have run it @ 10,950 with great success... BUT

with the 17T front:
-(10,950rpm) => a little over 153.478684 mph
-(10,975rpm) => a little under 154.100056 mph
-(10,990rpm) => a little over 154.100056 mph

I think I am WAY over analyzing this... I'm gonna flip a coin and set it at either 10,950 or 10,975. My best trap speed to date is 152.85mph. I have no clue if that will go up at all...

 

[Professor]

You can put a TPS switch like they use for N2O on the GPS sensor. Then when it gets in 4th, it deativates the autoshift. This will allow you to shift to 2, 3, and 4 @ 10,700 and rev 4th on out. DynoJet "may" be working on the same solution within the hub right now.

 

[Elganja]

My dyno sheet from last weekend show the rev limiter at 11,300 for the hard cut off. It does show a drop in power at 11k, like a soft limit. You may want to lower the hub RPM a bit more.

I meant to ask you earlier, but when you say soft limit do you just mean power starts to drop off and the actual limiter was 11,300? If that is the case then I should be golden.

I'm not looking to over rev or make power past 11k. My concern was that my HUB is set at 10,975rpm to shift and it will shift then, but if the limiter is 11k then it may hit it and bounce which could hose the shift all together.

 

[Elganja]

You can put a TPS switch like they use for N2O on the GPS sensor. Then when it gets in 4th, it deativates the autoshift. This will allow you to shift to 2, 3, and 4 @ 10,700 and rev 4th on out. DynoJet "may" be working on the same solution within the hub right now.

I wouldn't even know where to begin to do something like that... lol

I hope dynojet does release the capability to set the Analog output by gear. All the pieces are there the software needs to just be updated.

I'm just gonna stick the 17t in there and see how it goes on Friday.

 

[Elganja]

I made it out to the track today, it was interesting. This is the first time I have gone since my mishap (click here to read about it) and I added the 17t front sprocket

This bike is a an animal now. No other way to put it... lol... again Greg @ HPC thanks for making this bike so fast!

Didn't get any new best 1/4 times and my 60ft times were off a lot. I took it very easy. Detailed track times and notes are in my sig, but I'll just give a general overview.

Bike trapped a new best 1/4 mph @ 153.53 mph (ended up going a 9.812 w/ 1.943 60ft).
Bike trapped a new best 1/8 mph @ 124.02 mph (ended up going a 9.666 w/ 1.924 60ft).
Bike slid all over the place in a couple passes and I had the common sense to let out and abort the run this time.

In general on the 2 clean passes I made, the times from 330' to 1/4 were better by a couple hundredths or so (more details in my track times spreadsheet, see sig). Also, on those 2 passes, it shifted into 5th right before the traps. If I had to guess, I would say about 10-15feet before the traps. Go figure... the numbers don't really add up according to the gearing calculator OR my auto shifter (HUB + Air shifter) is shifting earlier then it is suppose to. My "shift point" was set at 10,975RPM. **edit: just remembered that Greg @ boostbysmith told me that devices such as the HUB have filters. It could of very well shifted @ 10,900 even if I set it higher. In that case it would make sense that it shifted into 5th

I have a track rental day coming up soon (June 6th) and I plan on keeping the same setup I currently have (minus adding a drag seat). Eventually I think I am going to go up 2 in the rear so I can finish towards the top of 5th in the 1/4 mile. And after that rental my stock tire should be shot... so that means time for a real tire that will hopefully solve my traction woes.

 

[Spudley]

"Whats the best combo to go with...."

One FRONT, and one REAR......"that is all"

....anything else I can help you with

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