Author Topic: Rev matching..  (Read 2345 times)

Online Huzo

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Rev matching..
« on: January 13, 2022, 05:52:10 PM »
Ok, here’s a question regarding “rev matching” with quick shifters.
At the moment the new gear is selected and at the instant it goes through, does the quick shifter throw any form of a clutch and disconnect the crankshaft from the rear drive.
If it does, read no further..
If it does not, strap in.

As an example, at the moment you are about to change down from say, 4th to 3rd taking the rpm from 3,500 to 4,000.

IF the engine is not disconnected from the rear drive at the moment of the downshift, how can the crankshaft adopt the new rpm of 4,000 (which is what it’s going to need), from 3,500 in the time between 4 th gear doing the driving and 3rd gear ?
Please do not tell me some half baked story about constant mesh gears and the like.
My question is, what gear is engaged at the moment that the revs ARE BEING increased, you can only increase rpm at a given speed if the drive train is disconnected and if there is no clutch, that has to occur when the drive is BETWEEN 4th and 3rd.
How long is it in that condition, 0.2 seconds ?
The transition between gears is almost instant (not quite of course), but increasing rpm takes discernable time.
I cannot see how a solid driving mechanism like metal gears, can be matched so perfectly EVERY TIME such that the driven gear is in perfect mech with the driving gear. I reckon the driving dogs are being put through hell.
Remember, at the last instant that you exit 4th and engage 3rd, your road speed had not changed.
Where are you Tusayan ?
« Last Edit: January 13, 2022, 05:57:57 PM by Huzo »

Offline SoCV

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Re: Rev matching..
« Reply #1 on: January 13, 2022, 06:03:27 PM »
 Motorbikes use sequential constant mesh transmissions , no need to match revs or disengage anything .

 Dusty
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Online Huzo

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Re: Rev matching..
« Reply #2 on: January 13, 2022, 06:07:02 PM »
Motorbikes use sequential constant mesh transmissions , no need to match revs or disengage anything .

 Dusty
Too glib Dusty.
So do use the clutch on your bike when shifting ?
So quick shifters are pointless ?
Why not just crash it through clutchless and let the transmission crunch the crankshaft up to the new rpm ?
« Last Edit: January 13, 2022, 06:08:20 PM by Huzo »

Offline SoCV

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Re: Rev matching..
« Reply #3 on: January 13, 2022, 06:14:24 PM »
Too glib Dusty.
So do use the clutch on your bike when shifting ?
So quick shifters are pointless ?
Why not just crash it through and let the transmission crunch the crankshaft up to the new rpm ?

 Do you remember the engineers and mechanics here explaining how a constant mesh transmission works Peter ? Nothing glib about it , in fact back when I raced upshifts were always done clutchless , on the street using the clutch just makes things smoother is all . There were dirt bikes from the 70s designed to shift clutchless .

 Actually I think most modern quick shifters kill the ignition for a microsecond , something we did way back in the day with the kill button .

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Re: Rev matching..
« Reply #3 on: January 13, 2022, 06:14:24 PM »

Online Mike Tashjian

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Re: Rev matching..
« Reply #4 on: January 13, 2022, 06:49:35 PM »
New to me 18 BMWR1200RT has pro shift and up shifts you can hear the exhaust note change for a split second as the ignition is cut to aid shifting.  On the downshift it has an overrunning clutch to help smooth things out.  Overall I like the upshifting and do it pretty well.  The downshifts are OK with a closed throttle and not very good under power, like needing a lower gear for a hill. 

Offline lucky phil

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Re: Rev matching..
« Reply #5 on: January 13, 2022, 07:19:29 PM »
The shifter has an up and down pressure sensor talking to the ecu. The ecu also knows what gear the bike is in the road speed and the target rpm for the lower gear for the road speed. At the sensor lever threshold pressure the ecu via the FBW throttle pops the rpm to the target figure for the next lower gear thereby offloading the gear drive dogs from the overrun load on them and the foot pressure drives the shift lever and the gear selection. Anyone that's ridden a motorcycle knows you need to rev match on the downshift while using the clutch to get a clean and smooth engagement. The other option I've seen used is to just kick it down through the gears and let the slipper clutch do the work which I don't recommend myself. I've seen professional racers do clutchless downshifts before throttle blippers and standing by the side of the track into slower corners was a horrendous to hear experience. Troy Bayliss used to do  it in WSB if the story I heard was correct until Tardozzi got onto him about the amount of transmissions he was wrecking.
My track Ducati 1198 has a Techtronics quick shifter that unlike more popular but basic cheaper units knows gear position and road speed and can be upgraded to downshift blipping with an optional actuator to drive the cable operated throttle bodies. I haven't bothered with it.

Ciao 
« Last Edit: January 13, 2022, 07:24:51 PM by lucky phil »
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Offline rschrum

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Re: Rev matching..
« Reply #6 on: January 13, 2022, 07:35:14 PM »
Original quick shifter.


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Offline lucky phil

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Re: Rev matching..
« Reply #7 on: January 13, 2022, 07:40:45 PM »
New to me 18 BMWR1200RT has pro shift and up shifts you can hear the exhaust note change for a split second as the ignition is cut to aid shifting.  On the downshift it has an overrunning clutch to help smooth things out.  Overall I like the upshifting and do it pretty well.  The downshifts are OK with a closed throttle and not very good under power, like needing a lower gear for a hill.

Yea they're not going to be optimal in that situation, you need to shift manually at those times.

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Offline twowheeladdict

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Re: Rev matching..
« Reply #8 on: January 13, 2022, 07:56:12 PM »
I test drove a Nissan 370Z manual with synchro rev matching.  It was pretty impressive and negated the need for heel/toe downshifting. 

Haven't tried a bike with a quick shifter, but I have preloaded the shifter a few times and closing the throttle before pulling the clutch the transmission slipped quietly into the next gear. 

Not sure I need a bike with a quick shifter for the way I ride these days. 
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Re: Rev matching..
« Reply #9 on: January 13, 2022, 08:21:56 PM »
I recently read an article about quick shifters. Not all work with downshifts only upshifts. Some cut spark and others interrupt fueling. I only read it to understand it, I have no intention of owning one. Normal shifting procedures work just fine for me. I got a lot of practice shifting ancient Airheads smoothly so Guzzis are a piece of cake. Makes shifting my new Triumph seamless.  Of course Triumph gearboxes run at reduced speeds as opposed to Guzzi gearboxes which have to function at crankshaft speeds.
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Offline lucky phil

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Re: Rev matching..
« Reply #10 on: January 13, 2022, 08:26:45 PM »
I test drove a Nissan 370Z manual with synchro rev matching.  It was pretty impressive and negated the need for heel/toe downshifting. 

Haven't tried a bike with a quick shifter, but I have preloaded the shifter a few times and closing the throttle before pulling the clutch the transmission slipped quietly into the next gear. 

Not sure I need a bike with a quick shifter for the way I ride these days.

This is how I shift my V10 Sport all the time. Loading the lever before pulling the clutch has the transmission shifting really nicely although I have the lucky Phil shift extender as well which helps also. You still need to rev match though for a nice clean engagement.

Ciao
« Last Edit: January 13, 2022, 08:27:38 PM by lucky phil »
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Offline Kiwi_Roy

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Re: Rev matching..
« Reply #11 on: January 13, 2022, 08:27:48 PM »
A couple of my riding buddies ride modern Yamahas with slipper clutches, apparently you can just bang them through the gears.
I assume a slipper clutch must disengage the drive for a split second am I correct?
Anyway none of my Guzzi's will ever get a clutches change although I did ride one with a broken clutch lever once, its quite easy to do if you take it slow.
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Offline lucky phil

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Re: Rev matching..
« Reply #12 on: January 13, 2022, 08:33:51 PM »
A couple of my riding buddies ride modern Yamahas with slipper clutches, apparently you can just bang them through the gears.
I assume a slipper clutch must disengage the drive for a split second am I correct?
Anyway none of my Guzzi's will ever get a clutches change although I did ride one with a broken clutch lever once, its quite easy to do if you take it slow.
The slipper works as the name suggests. When the lower gear engages instead of the the engine trying to instantly go to the revs the road speed dictates the clutch slips until an equilibrium is met. Problem is it's hard on shift forks and shifter mechanisms due to needing to overcome the back drive load on the gear dogs when down shifting and no slipper clutch works seamlessly for all gears and road speeds.
My RSVR Aprilia had a vacuum operated one which didn't stop the bike trying to throw me over the high side out of turn 11 at Phillip Island when I short shifted the wrong way a few years ago.

Ciao   
« Last Edit: January 13, 2022, 08:37:31 PM by lucky phil »
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Online Huzo

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Re: Rev matching..
« Reply #13 on: January 13, 2022, 08:35:35 PM »
New to me 18 BMWR1200RT has pro shift and up shifts you can hear the exhaust note change for a split second as the ignition is cut to aid shifting.  On the downshift it has an overrunning clutch to help smooth things out.  Overall I like the upshifting and do it pretty well.  The downshifts are OK with a closed throttle and not very good under power, like needing a lower gear for a hill.
Ok then.
That fills in a few gaps. If it’s harmless, it’s not because there is no issue, it’s because the issue has been overcome.
It is not solely because of the sequential constant mesh feature of it’s design. The overrun clutch is something I did not know existed.
There are a plethora of guys that tell me that...
“My mate used to do it on his Norton back in the day...” etc...Blah blah..
I CAN do it, but am I cognisant of the damage I can be inflicting over 20,000 shift cycles and rendering a 200,000 k gearbox shagged as a result.
I approach the issue from the perspective of what energy is transferred through a fundamentally un cushioned system, by accelerating or decelerating a heavy spinning mass in 0.2 seconds.
See what I takes to accelerate the rotational mass of a Guzzi engine, from zero to 500 rpm in 0.2 seconds.

Talking to Roper about it today, he concedes that some amount of additional wear will be evident as a result of clutchless or quick shift changes. That was my question.

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Re: Rev matching..
« Reply #14 on: January 13, 2022, 08:37:10 PM »
The shifter has an up and down pressure sensor talking to the ecu. The ecu also knows what gear the bike is in the road speed and the target rpm for the lower gear for the road speed. At the sensor lever threshold pressure the ecu via the FBW throttle pops the rpm to the target figure for the next lower gear thereby offloading the gear drive dogs from the overrun load on them and the foot pressure drives the shift lever and the gear selection. Anyone that's ridden a motorcycle knows you need to rev match on the downshift while using the clutch to get a clean and smooth engagement. The other option I've seen used is to just kick it down through the gears and let the slipper clutch do the work which I don't recommend myself. I've seen professional racers do clutchless downshifts before throttle blippers and standing by the side of the track into slower corners was a horrendous to hear experience. Troy Bayliss used to do  it in WSB if the story I heard was correct until Tardozzi got onto him about the amount of transmissions he was wrecking.
My track Ducati 1198 has a Techtronics quick shifter that unlike more popular but basic cheaper units knows gear position and road speed and can be upgraded to downshift blipping with an optional actuator to drive the cable operated throttle bodies. I haven't bothered with it.

Ciao
Nice Phil..
Thank you.

Online Huzo

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Re: Rev matching..
« Reply #15 on: January 13, 2022, 08:39:55 PM »
The slipper works as the name suggests. When the lower gear engages instead of the the engine trying to instantly go to the revs the road speed dictates the clutch slips until an equilibrium is met. Problem is it's hard on shift forks and shifter mechanisms due to needing to overcome the back drive load on the gear dogs when down shifting and no slipper clutch works seamlessly for all gears and road speeds.
My RSVR Aprilia had a vacuum operated one which didn't stop the bike trying to throw me over the high side out of turn 11 at Phillip Island when I short shifted the wrong way a few years ago.

Ciao   
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Offline twowheeladdict

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Re: Rev matching..
« Reply #16 on: January 14, 2022, 07:08:52 AM »
The slipper works as the name suggests. When the lower gear engages instead of the the engine trying to instantly go to the revs the road speed dictates the clutch slips until an equilibrium is met. Problem is it's hard on shift forks and shifter mechanisms due to needing to overcome the back drive load on the gear dogs when down shifting and no slipper clutch works seamlessly for all gears and road speeds.
My RSVR Aprilia had a vacuum operated one which didn't stop the bike trying to throw me over the high side out of turn 11 at Phillip Island when I short shifted the wrong way a few years ago.

Ciao   

And manufacturers are finally realizing that it is not just powerful bikes that benefit from slipper clutches and have started putting them in bikes generally bought by new riders. 

Now if they would just start putting cruise control on lower displacement bikes. 
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Offline Frenchfrog

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Re: Rev matching..
« Reply #17 on: January 14, 2022, 01:22:11 PM »
Oh pleaaase..next it will be ABS on bleeding bicycles :grin:

Offline n3303j

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Re: Rev matching..
« Reply #18 on: January 14, 2022, 01:34:29 PM »
There is a neutral between each and every gear on all my bikes both past and present. Great time to do an RPM shift.
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Offline lucky phil

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Re: Rev matching..
« Reply #19 on: January 14, 2022, 01:53:28 PM »
And manufacturers are finally realizing that it is not just powerful bikes that benefit from slipper clutches and have started putting them in bikes generally bought by new riders. 

Now if they would just start putting cruise control on lower displacement bikes.
True, my Royal Enfield Interceptor 650 has one as well.

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Offline lucian

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Re: Rev matching..
« Reply #20 on: January 14, 2022, 05:04:03 PM »
all i can add Pete is that for us older riders they are very counter intuitive. You are tempted to help things along by trying to match engine rpm's like an old school clutch less up shift. WRONG!   Keep the hammer down and let the ECU take control .  My Tuono  is only quick up shifts, and is remarkably smooth if you have faith and leave the throttle constant and shift.
Wear to engagement dogs is primarily due to rider error and not staying on the throttle when upshifting. Remember when you are hammer down you are accelerating and a split second ignition gap is all it takes to smoothly roll you into the next gear. The problems arise when you let off the throttle and confuse the program. They are a joy on a bike trying to kill you as fast as possible.  You must come to Maine and  take Dan's for a spin.  :grin:

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Re: Rev matching..
« Reply #21 on: January 14, 2022, 11:18:43 PM »
all i can add Pete is that for us older riders they are very counter intuitive. You are tempted to help things along by trying to match engine rpm's like an old school clutch less up shift. WRONG!   Keep the hammer down and let the ECU take control .  My Tuono  is only quick up shifts, and is remarkably smooth if you have faith and leave the throttle constant and shift.
Wear to engagement dogs is primarily due to rider error and not staying on the throttle when upshifting. Remember when you are hammer down you are accelerating and a split second ignition gap is all it takes to smoothly roll you into the next gear. The problems arise when you let off the throttle and confuse the program. They are a joy on a bike trying to kill you as fast as possible.  You must come to Maine and  take Dan's for a spin.  :grin:
It’s never been about the gears Lucian, I have said that 500 times but everybody glosses over it..
It’s the almost instantaneous way that the heavy rotating flywheel has to drop or gain 500 rpm in something like 0.1-0.2 seconds.
Mate...
It’s....not.....about.....the .....gears.
The energy required to accelerate or decelerate that flywheel by 500 or so rpm, has to be dissipated through the solid drivetrain with nothing but the springs in the friction plate to dampen the thump.
If it’s enough then fine.
But I’ll wager that many a good gearbox has had it’s life shortened by this form of mechanical cruelty and when it starts to play up, it’s foisted onto some poor unsuspecting bastard.
« Last Edit: January 15, 2022, 01:40:25 AM by Huzo »

Offline tris

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Re: Rev matching..
« Reply #22 on: January 15, 2022, 12:47:04 AM »
This is an interesting discussion

The best I can come up with going is that
A) The shock load is dissipated to some extent by a slipper clutch if fitted or  the rear wheel losing traction momentarily
B) The engineers sized the components and selected appropriate materials that can accommodate the loads applied

I assume that going clutchless up the box, the instantaneous loads are the same but in the opposite direction?


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Online Huzo

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Re: Rev matching..
« Reply #23 on: January 15, 2022, 01:52:18 AM »
This is an interesting discussion

The best I can come up with going is that
A) The shock load is dissipated to some extent by a slipper clutch if fitted or  the rear wheel losing traction momentarily
B) The engineers sized the components and selected appropriate materials that can accommodate the loads applied

I assume that going clutchless up the box, the instantaneous loads are the same but in the opposite direction?
That’s absolutely right mate.
The drive train ether has to dissipate that energy INTO the rotating mass, or ABSORB that kinetic energy FROM the rotating mass.
A useful comparison is this..
If you hold your index finger under a hammer on an anvil and drop the hammer from 100 mm, you will stop the hammer in 2 mm and shatter your finger.
If you do the same test but have your finger on something like a rubber pad, that allows your finger to move 4 mm, you have halved the deceleration rate, but the load in the second case is the square root of the first.
If the deceleration rate is twice as much, the load is four times.
Now a normal lazy clutch change might allow 2 seconds for the flywheel to change.
If you use a clutchless shift and take 0.2 seconds, it is 10 times the acceleration rate and a hundred times the shock.
That is a rough analogy, but the mathematics applies.
« Last Edit: January 15, 2022, 01:53:06 AM by Huzo »

Offline lucian

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Re: Rev matching..
« Reply #24 on: January 15, 2022, 07:24:38 AM »
The slipper clutch is part of the ability to absorb shock ,  but also the fact that you are accelerating and not static. On top of that, a momentary cut in power/ ignition and a calculated engine rpm adjustment via the ecu . makes the whole thing work provided there are no input errors.   I have yet to hear of a gearbox failure on a Tuono , And that's a bike putting down 90 ft. lbs. of torque and 175 hp.  A few have rounded off the engagement dog due to rider error . Mostly from using QS a slow speeds. It seems the more you are accelerating when clicking up, the more they like it.

Offline Bulldog9

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Re: Rev matching..
« Reply #25 on: January 15, 2022, 02:47:22 PM »
As others have said, rev matching is not a thing for motorcycle transmissions due to design. For track/racing purposes, 'rev matching' is more for a smoother engagement and less driveline lash. By either heel-toe in cages or application of throttle on a motorcycle, proper throttle and engine speed when downshifing and preparing to re-accelerate, it is essential to have engine speeds ideal for accelerating out of the turn following a downshift.  My Bullitt Mustang has revmatching, and it is pretty cool. I can shut off for good old heel toe shifting, but is spot on perfect. The ECU brings revs to the right level for the lower gear and helps with the syncros and less driveline lash and lag. Is pretty cool.

As for clutchless shifting, and quick shifters, that has been discussed as well. I have been riding clutchless for years, even on my old clunky XS bikes. A little preload on the shifter, and blip of the throttle, the V7 snicks through the gears as well as my FJR and FZ1 did.

One thing not discussed is how flywheel weight effects clutchless shifting. I find that the relatively heavy flywheel on the CARC bike I've owned (Griso/Norge/1200 Sport) makes clutchless shifting less than ideal, especially in 2-4 up or down shifts. 4-5-6 up or down can be done easily enough, but I can't go into 2-3-4 clutchless upshifting on those bikes without a jerk. On the V7 and MGX it was fluid smooth.
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Offline Kiwi Dave

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Re: Rev matching..
« Reply #26 on: January 15, 2022, 03:23:38 PM »
Many years ago, I owned a Triumph that disengaged the clutch automatically when changing gear, no need to touch the clutch lever.

It worked quite well, but I never saw the feature on any later Triumphs I purchased.  Was good for (sometimes unintentional) wheel stands, too!

Offline Frenchfrog

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Re: Rev matching..
« Reply #27 on: January 15, 2022, 04:07:09 PM »
I think they called that the "slick shift " Dave....didn't last long.

Offline tris

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Re: Rev matching..
« Reply #28 on: January 15, 2022, 04:27:11 PM »
As for clutchless shifting, and quick shifters, that has been discussed as well. I have been riding clutchless for years, even on my old clunky XS bikes. A little preload on the shifter, and blip of the throttle, the V7 snicks through the gears as well as my FJR and FZ1 did.

I must be missing something :embarrassed:
How do you blip the throttle when the bike is in gear, surely that would cause it to accelerate?

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Offline lucky phil

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Re: Rev matching..
« Reply #29 on: January 15, 2022, 06:58:24 PM »
I must be missing something :embarrassed:
How do you blip the throttle when the bike is in gear, surely that would cause it to accelerate?

PS Bullitt Mustang  :cool: :cool: :cool: :cool: :cool:

Because the ecu knows the gear you're in and the road speed it calculates the rpm needed for the next lower gear. With the engine on the overrun and the backlash dogs on the gears "loaded" due to driving the engine and foot pressure on the gear lever when the foot pressure threshold is reached the ecu simply blips the throttle to the required rpm. As the engine begins to accelerate to the desired rpm the split second the load comes off the gears the foot pressure on the already loaded shifter moves the drum and engages the next gear. On a bike it's not actually "blipping" the engine rpm in the manner a car with an H pattern gate is it's more "rev matching" and it all happens in a fraction of a second. The gear unloads and starts to disengage right at the start of the process of the revs increasing. The revs don't actually need to increase in reality to do this, the drive load just need to come off the gear with foot pressure applied on the gear lever. It's a similar reason a gearbox always shifts cleaner when you load the lever before you pull the clutch. As soon as the clutch has unloaded the drive dog faces the pressure that's already applied via the foot pressure drives the gear.  It's also why the system works better with engines with light cranks and multi cylinders that rev quick and at high rpm. At low rpm/slow revving engines the shift action can be faster in elapsed time than the engine can bring the revs up. When the engine is really revving it catches additional revs a lot quicker.
The lever extender mod I came up with and Chuck manufactured improved the shifting of the v11 gearbox because it reduced some of the leverage advantage your foot had over the shift mechanism so when the load came off the gear dogs and the detent spring released there was extra force already applied to the shift lever due to the reduced leverage which meant the shift action was faster and the shift cleaner. So faster cleaner shift action with reduced lever movement but with slightly heavier action. Gearbox shifting mechanics is an interesting subject and there are so many pieces that combine to make a clean shifting gearbox.

Ciao       
« Last Edit: January 15, 2022, 07:15:39 PM by lucky phil »
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