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QuickShifter Circuit...

12679 Views 11 Replies 6 Participants Last post by  Slipry, 
Eclipze
[align=center]QuickShifter Circuit...[/align]

If you'd like to make a poor mans quickshifter, read on.

A quickshifter facilitates changing up gears without using the clutch. It's not good for the transmission, particularly if not done correctly, but many racers use them. Usually you have a sensor on the gear lever to detect when the gear is being changed up, and a circuit will automatically cut the ignition for a defined period. This brief engine cutout unloads the pressure on the gears for the gear change.

The poors mans version is to use a switch, without a defined automatic cutout timing circuit.

The circuit below shows where the switch must be wired in. NOTE: The switch MUST BE a normally closed momentary push switch... aka, normally (with the button not touched) it connects the two terminals, but when pressed the circuit is opened.


[align=center]
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The left hand switchgear on the CBR250 has two convenient buttons, the passing highbeam and horn switch, however both are the wrong type of switch and connect to ignition. If you try to hook up to these, your likely to just blow fuses and risk damaging the stand switch. They would need to be heavily modified to suit. Your better off getting a different buttons and creating a mounting bracket for it.

:cool:
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C
so this eliminates the need to the back off the throttle for that split second and just hold it flat?
also would having weight on the shift lever and banging it off the limiter give it that momentary unload on the gears to change up? this is what i have heard before thats all.
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Eclipze
crazylegs said:
so this eliminates the need to the back off the throttle for that split second and just hold it flat?
also would having weight on the shift lever and banging it off the limiter give it that momentary unload on the gears to change up? this is what i have heard before thats all.
Click to expand...
Yep... it does eliminate the need to back off on the throttle.

Banging off the limiter would also give the same pause needed. But for a CBR250, I'd suspect at that stage you've already lost time from dropping off the torque ~1500rpm ago.

The other problem with bouncing off a limiter is it's less controllable. ie... it happens when it happens, not when you want it to happen. Not very flexible for track use.

Funny side... more so with a more powerful bike, is hitting the limiter and not being ready for the quick shift can result in head banging the windscreen :lol:
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C
lol ok thanks.
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B
crazylegs said:
so this eliminates the need to the back off the throttle for that split second and just hold it flat?
also would having weight on the shift lever and banging it off the limiter give it that momentary unload on the gears to change up? this is what i have heard before thats all.
Click to expand...
I installed one of these switches and found it still seems to work best if you back off the throttle a little when changing.
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R
Similar deal on a SS ecu or a ECUnleashed hack.

Great write up Eclipze.
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J
nice!
not a bad idea
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R
Oh btw Eclipze:

you should probably add that not only does it unload the geartrain for a smoother shift, by not closing the butterflies you don't interrupt airflow, and increase lag in the next gear by needing to wait for the air to "speed up" again through the carbs, the net result is an appreciable difference in lap times. I think Knackers dropped 3/4 of a second or something similarly huge when he fitted the dynojet shift rod to the R1.

For supersport you can't have a quickshifter that's physically linked to the gearbox, most people use the horn button.
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Eclipze
richo said:
Oh btw Eclipze:

you should probably add that not only does it unload the geartrain for a smoother shift, by not closing the butterflies you don't interrupt airflow, and increase lag in the next gear by needing to wait for the air to "speed up" again through the carbs, the net result is an appreciable difference in lap times.
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Oooo... very good point! Wasn't actually aware of that :dance:
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S
Ok so im digging up an old post. I just cant let this go. Im so sorry but it is literally stopping me from sleeping and I have been like this for weeks.
I have observed that as the gear leaver is depressed whilst in reverse shift the gear selector results in some movement resulting in fore and aft movement. Because the base of the leaver when depressing the gear leaver moves toward the rear wheel I cant see why this circuit cant be applied to rather than hand operation, be as a natural movement of the foot in changing gears.

Im certain with a simple switch, bracket off the heel guard mountings, and some minor adjustments it is possible to add what is effectively an ignition cut whilst gear selection is taking place. I also believe it more than possible to mount a bypass circuit and have a switch mounted near the usual location of the fan overide so during normal commuting you dont have the ignition cut.

This is the bit where I get stuck...

I note that quick shifters have a variable on off period to enable the ignition cut. In the circuit I envisage this cut time is limited to your foot speed to depress and release. Will this be sufficient for a clean and quick shift? If a delay switch activated by the leaver depression was to be made, how the fuck do you wire this in and where could you find an adjustable time delay off switch that is activateduby the lever hitting another switch?

Im kee to try it but these questions are preventing me from starting.
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Eclipze
If you want a professional quickshifter, you get one that has a pressure sensor and/or push rod with pressure sensor and associated single shot cut out time. If you want to DIY, then you need to find someone with some electronic skills to make a 555 timer circuit in monostable one-shot configuration, with adjustable trimming resistor.
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Not putting your hand up eclipze?
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