True rpm @ 180 mph

[R1000]

Anyone know? I'm planning to set the shift light to this rpm and let it drive a switch that connects the 22 kohm no-speed-limiter-resistor at this rpm.

 

[Commuta_Busa]

it's going to change any time you change gearing and change the tires loaded rolling radious.

Why not just do the mod so the ECM is only effected during 6th gear?

 

[R1000]

The ECM only speed limits to 186 mph by rpm on 6th gear, so this is already built in. And since the speed limiting is done by sensing rpm on 6th gear, it will be affected by changed gearings anyway. The thought is to know the speed limiting rpm stock, adjust accordingly, and change the shift light setting as needed if another gearing is used later. The resolution of the shift light setting is 250 rpm at the higher rpm's, so this should be enough to retune the function for any gearing.

 

[Commuta_Busa]

well, here's the formula. rpm = ((mph x (trans gear x primary gear x (rear sprocket / front sprocket)) x 336.135239810083) / tire diameter)

mph = 186
trans gear = 1.043
Primary gear = 1.596
rear sprocket = Gen1 = 40 or Gen2 = 43
front sprocket = Gen1 = 17 or Gen2 = 18
Tire diameter = Loaded dia (in inches)

 

[R1000]

Hmm, wonder what the rolling diameter is at super sonic speed, guess I have to take a RPM reading at high speed that is measured by GPS. The bicycle computer is calibrated within perhaps a percent a low speeds, but the rolling diameter may change quite a bit a 300 km/h.

 

[R1000]

I've looked into the shop manual and there is no easy way to grab the signal to the RPM LED unless playing with the speedo cluster. The information from ECM to the different indicators seems to be a serial bus. This means a separate RPM switch, to control the 20 C resistor connection, is a safer and more simple solution.

 

[jetsetter]

Anyone know? I'm planning to set the shift light to this rpm and let it drive a switch that connects the 22 kohm no-speed-limiter-resistor at this rpm.

This is a fantastic idea! It will be a great way to have a TRE when you need it and have a proper gear indicator the rest of the time.

 

[BIKE DUDE]

That is a clever idea if....you can find a good way to tap into it there??

 

[serendipity]

In reality, it doesn't much matter what RPM corresponds to 180mph, since the limiter isn't based on vehicle speed anyway and won't change based on gearing. All you need to do is set your shift light for 10,200 RPM, which is the limiter in 6th gear.

Great idea, BTW.

 

[R1000]

In reality, it doesn't much matter what RPM corresponds to 180mph, since the limiter isn't based on vehicle speed anyway and won't change based on gearing.  All you need to do is set your shift light for 10,200 RPM, which is the limiter in 6th gear.

Great idea, BTW.

Thanks a lot !

Okay, the basic solution now seems quite clear. I'll use a separate RPM switch and let the instrument cluster and stock RPM-light be left untouched. The RPM switch, e.g. an MSD P/N 8950 or the other type mentioned in the 20 C thread, will be used to connect the 22 kohm resistor at 10 000 rpm or a bit lower. This means the gear indicator will be 1N23456 in all situations except on 6th above 10 000 rpm when the speed limiter is disabled. I'm used to work with the MSD stuff and the P/N 8950 is available here in shops, so this will be the first shot. I will not use the RPM beans as normal for MSD, but solder a resistor instead to get a more rigid solution than using beans or mechanical switches. I have the resistor vs. RPM value listing laying around and it has to be calibrated anyway since we don't want an error of more than about one hundred RPM or so in the switch. The switch can of course also be set to e.g. 9500 RPM to get a good margin for any temperature variations.

Even though the idea using a RPM switch isn't really bad, credit should go to Hy-Gain Busa who developed the genious solution to handle the speed limiter describes in https://www.hayabusa.org/forums/?act=ST;f=77;t=93577

 

[R1000]

A cool feature is that the solution will show that is actually operates, and when the gate to 300 km/h territory is opened, by the gear indicator changing from 6th to 5th at 10 k on 6th .