Flatshifter experiance
Discussion
fergus said:
How does it achieve clutchless downshifts smoothly? Even with an autoblipper surely the clutch must be disengaged to allow this to 'blip'?
I will ask.. I assume that it blips between the gears.. although I wouldn't have thought it would have time.. I know a guy with one fitted and apparently it works very well.. he has a video on U-Tube its a gulf colours radical doing a track day at Lydden Search on Lydden track day and you will find it. It sounds like it works quite well but I do note that the guys is not exactly trashing the car..!
check this one out
http://www.youtube.com/watch?v=U-s3f6P7YaM&fea...
a rather impressive lap of snetterton, I'm blown away by the grip/handling/downforce i must say !!
http://www.youtube.com/watch?v=U-s3f6P7YaM&fea...
a rather impressive lap of snetterton, I'm blown away by the grip/handling/downforce i must say !!
The function of the throttle blip is primarily to release the reverse torque loading on the dogs so that the current gear can be disengaged. When the dog ring is then in between gears the blip helps to increase the engine revs to match the next gear. If the blip and shift strategy are carefully controlled by a closed-loop electronic system then the blip is hardly noticeable. However, the last thing you want to do is exactly match the dog ring and gear speed as it can then take a long time for a window to open up to engage the next gear. Clutchless downshifting is an extremely difficult thing to get right if you want reliable shifts with no dog damage. The magnitude of the blip needs to be tuned to specific engines at a particular speed. When set correctly for high speed downshifts, it will be poor at low speed and vise-versa. For the most reliable and non damaging shifts, ideally the duration of the blip will be determined dynamically, which means continually monitoring the barrel position using a sensor and sophisticated electronics/software.
ScottHughes said:
Ahhh, missed the "er". As Neil says the mechanism to get a good clutchless downshift is quite tricky! I'm not saying that their claims are wrong, but I wouldn't be betting my gearbox on it! Ask them if they will fix the box if the downshift brakes it!Bert
BertBert said:
ScottHughes said:
Ahhh, missed the "er". As Neil says the mechanism to get a good clutchless downshift is quite tricky! I'm not saying that their claims are wrong, but I wouldn't be betting my gearbox on it! Ask them if they will fix the box if the downshift brakes it!Bert
still don't see how a blip is effective w/o disengaging the clutch?Fergus,
As I stated previously, the blip is primarily there to unload the dogs so that you can disengage the current gear without using the clutch. If you don't do the blip, the dogs won't release unless the clutch is pressed because the reverse torque loading keeps them locked together. Once the dog ring has left the current gear, but not yet engaged in the next gear, the blip can then increases the speed of the gear to match the road speed. This makes the engagement smoother and less likely to unsettle the car. Pressing the clutch means that the blip is actually less effective at engaging the next gear, because without drive from the engine, the gear train slows down too much when the dog ring is disengaged. That's why on old 'crash' boxes you double clutch to shift smoothly - the mid shift clutch engagement when the box is in neutral spins the gears to the correct speed to match the prevailing road speed. All you are acheiving by blipping with the clutch pressed is reducing the chance of the engine inertia locking the driven wheels, it has no effect on the actual mechanism of the gear shift. In actual fact, clutching a dog box is more damaging than not using the clutch. See this artical by William Hewland - http://www.hewland.com/svga/help.htm Auto-blipping using a sequential box only works well on 'proper' race engines that have very low inertia and hence instant response. The window for increasing rpm between gears is very small (in the order of a few milliseconds) so you need extremely responsive engines to see any rpm increase at all. That's why it's very tricky to perfect clutchless shifts with auto-blip using road-car based engines. The lack of response often means that you can't even get the box out of gear, but when it does come out, the speed mismatch between the dog ring and the next gear is too large to get a clean engagement. Increased dog wear is the likely outcome unless the blip and shift are very carefully co-ordinated, preferably under closed-loop control.
I've spent over 2 years non-stop developing my paddleshift system on various cars (including most of the F3000 grid). The strategy for successful and non-damaging downshifts is very complex and it's not just a case of cracking open the throttle and hoping for the best.
As I stated previously, the blip is primarily there to unload the dogs so that you can disengage the current gear without using the clutch. If you don't do the blip, the dogs won't release unless the clutch is pressed because the reverse torque loading keeps them locked together. Once the dog ring has left the current gear, but not yet engaged in the next gear, the blip can then increases the speed of the gear to match the road speed. This makes the engagement smoother and less likely to unsettle the car. Pressing the clutch means that the blip is actually less effective at engaging the next gear, because without drive from the engine, the gear train slows down too much when the dog ring is disengaged. That's why on old 'crash' boxes you double clutch to shift smoothly - the mid shift clutch engagement when the box is in neutral spins the gears to the correct speed to match the prevailing road speed. All you are acheiving by blipping with the clutch pressed is reducing the chance of the engine inertia locking the driven wheels, it has no effect on the actual mechanism of the gear shift. In actual fact, clutching a dog box is more damaging than not using the clutch. See this artical by William Hewland - http://www.hewland.com/svga/help.htm Auto-blipping using a sequential box only works well on 'proper' race engines that have very low inertia and hence instant response. The window for increasing rpm between gears is very small (in the order of a few milliseconds) so you need extremely responsive engines to see any rpm increase at all. That's why it's very tricky to perfect clutchless shifts with auto-blip using road-car based engines. The lack of response often means that you can't even get the box out of gear, but when it does come out, the speed mismatch between the dog ring and the next gear is too large to get a clean engagement. Increased dog wear is the likely outcome unless the blip and shift are very carefully co-ordinated, preferably under closed-loop control.
I've spent over 2 years non-stop developing my paddleshift system on various cars (including most of the F3000 grid). The strategy for successful and non-damaging downshifts is very complex and it's not just a case of cracking open the throttle and hoping for the best.
Thanks for the coments on the youtube video Scott I assume you meant to say thrashing it, as opposed to trashing it.
It's a trackday, no need to be too hard on the car......... there are no trophies in the gravel traps .............. I know i've looked before
Regarding other comments posted on flatshifters, why do people not believe what they don't understand even after it's explained to them ? It works get over it
It's a trackday, no need to be too hard on the car......... there are no trophies in the gravel traps .............. I know i've looked before
Regarding other comments posted on flatshifters, why do people not believe what they don't understand even after it's explained to them ? It works get over it
chapiness said:
Regarding other comments posted on flatshifters, why do people not believe what they don't understand even after it's explained to them ? It works get over it
Er, it looks to me from the explanation here (and from my understanding generally), is that it does work, but needs some sophisticated technology (ideally closed loop) and needs to be set up specifically for the installation. So we'd rather work on something approaching a mechanical explanation than "it works, get over it"! Also the consequences of not working could be expensive.Bert
chapiness said:
Thanks for the coments on the youtube video Scott I assume you meant to say thrashing it, as opposed to trashing it.
It's a trackday, no need to be too hard on the car......... there are no trophies in the gravel traps .............. I know i've looked before
Regarding other comments posted on flatshifters, why do people not believe what they don't understand even after it's explained to them ? It works get over it
I already use a flat shift system in a Sadev box in my race car, but I've never seen any system able to autoblip w/o disengaging the clutch. It's a trackday, no need to be too hard on the car......... there are no trophies in the gravel traps .............. I know i've looked before
Regarding other comments posted on flatshifters, why do people not believe what they don't understand even after it's explained to them ? It works get over it
Not sure why I should 'Get over it' when I was merely stating that I still didn't understand how it worked (due, until now, to no one actually attempting to provide an adequate explanation). I'd still like to see the system in action prior to fitting it to my box though.
Fergus,
Ask the manufacturer for a demonstration, or better still, ask them to put you in touch with others that are using the system. User recommendations speak far louder than sales literature!
To see a throttle blipper in action with a paddleshift system, have a look here http://uk.youtube.com/watch?v=HYwk2ndYkiE I can assure you that the drivers foot never touches the clutch pedal except for standing starts!! The engine in the video is a Zytek KV, which responds a tad quicker than most production based engines you care to mention, so clutchless downshifts are super smooth and in most cases just as quick as upshifts (30-40ms).
Ask the manufacturer for a demonstration, or better still, ask them to put you in touch with others that are using the system. User recommendations speak far louder than sales literature!
To see a throttle blipper in action with a paddleshift system, have a look here http://uk.youtube.com/watch?v=HYwk2ndYkiE I can assure you that the drivers foot never touches the clutch pedal except for standing starts!! The engine in the video is a Zytek KV, which responds a tad quicker than most production based engines you care to mention, so clutchless downshifts are super smooth and in most cases just as quick as upshifts (30-40ms).
Gassing Station | Radical | Top of Page | What's New | My Stuff