| Author |
Message |
    
Interex2050
| | Posted on Tuesday, March 18, 2008 - 04:16 pm: | 
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Test subject:
1997 EX250R
Idle (1600rpm steady) ~140mmHg
Revving ~>20mmHg
4000rpm (steady) ~160mmHg
Drop to idle (peak) ~350mmHg
Revving ~>20mmHg
6000rpm (steady) ~180mmHg
Drop to idle (peak) ~440mmHg
Revving ~>20mmHg
8000rpm (steady) ~140mmHg
Drop to idle (peak) ~480mmHg |
Interex2050
| | Posted on Tuesday, March 18, 2008 - 04:18 pm: |
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And well done I must say...
This is the most fun I have had on here in a while.
And in the end we may have a better answer |
Ratbuell
| | Posted on Tuesday, March 18, 2008 - 04:29 pm: |
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Hm, good data. I guess my ol' in/Hg gauge isn't nearly as accurate as mm/Hg 
Curious, how long does it hold the peak vacuum readings? Momentarily, then level out? Or is it a peak right at the onset of decel, and it ramps steadily down as revs drop?
Maybe I should run the car with my MT2500 hooked into it..although I'd have to have a co-pilot crazy enough to hop in an 11 second Dodge Shadow with me to do the readings, lol. |
Interex2050
| | Posted on Tuesday, March 18, 2008 - 04:56 pm: |
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As mentioned before naturally aspirated vs forced intake engines will probably behave very differently
as will turbo vs super
Not to mention it depends on where those readings are coming from
The peak vacuum occurred right after I closed the throttle, and went down with the rpms.
Some more interesting calculations:
Assuming:
-the diaphragm on the 1125R has an outer diameter of 150mm and inner diameter of 40mm (hole for the slave cylinder)
-the pressure readings are somewhat similar
-the reference pressure is atmospheric
A=.0164_m^2
Pressures below atmospheric:
idle 18665_Pa
drop from 4000rpm 46663_Pa
drop from 6000rpm 58661_pa
drop from 8000rpm 63995_Pa
The "assisting/slipper" forces are:
idle 69_lbf
4000rpm drop 170_lbf
6000rpm drop 220_lbf
8000rpm drop 240_lbf
Although the values above have little to do with the values on the 1125R
They do give a good indication on how much assisting the system is capable of supplying. |
Diablo1
| | Posted on Tuesday, March 18, 2008 - 08:22 pm: |
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The slipper clutch is designed to slip when the rider doesn't downshift smoothly with a throttle blip. That doesn't mean you should try to downshift without pulling in the clutch or matching rpms. Also, you need to keep in mind that banging a downshift or two from high rpm is a great way to bend your valves. Just because the engine has a revlimiter doesn't mean it stops the engine from over-revving on a downshift. |
Ccryder
| | Posted on Wednesday, March 19, 2008 - 09:58 am: |
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Heck when I was growing up if you had a slipper clutch, you weren't going too far or too fast ;+}.
I'll be nice, I do like my slipper clutch even though I still match rpm's when down shifting. It is nice to know that when you need the slipper feature it is there.
Time2Work
Neil S. |
Bearly
| | Posted on Thursday, March 20, 2008 - 03:23 am: |
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Sea Level Standard atmosphere is 29.92 inches of mercury (14.7 psi absolute). Depending on the efficiency of the pumping action of a particular piston engine, the engine will have about 9 to 12 map (manifold pressure) or inches with the throttle closed. Less inches, more difference from, more vacuum from standard atmospheric. The more vacuum the more the pull from the pressure difference from one side of the diaphragm to the other. Simple
Full throttle at sea level a piston engine can pull about 28.5 as the throttle valve is open but the engine is still pulling on a non boosted piston engine. |
Xl1200r
| | Posted on Thursday, March 20, 2008 - 09:55 am: |
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Ok, I did some experimenting in the car.
Idle is about 18". Cruise is about 10-12". Decel with the throttle closed is 22-23". It doesn't trail off to the idle level until it's actually at idle.
ANYTIME you touch the throttle, vacuum goes down.
If the throttle is closed on decel, and you leave is closed through the downshift, the vacuum stays the same (bottomed out).
If you blip the throttle on the downshift, the vacuum will decrease, and then has to get back to max vacuum once the throttle closes again.
Basically, blipping the throttle just means it takes more time to get to full vacuum than not blipping.
So, NOT BLIPPING will allow the slipper to work more effectively.
HOWEVER - by blipping, less slipping is needed in the first place, correct? The revs are closer, so it's a closer match. If you blip, the clutch can't slip as much, but then again, it doesn't need to.
What I'm trying to say is it doesn't matter, lol. |
Trojan
| | Posted on Thursday, March 20, 2008 - 10:23 am: |
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HOWEVER - by blipping, less slipping is needed in the first place, correct? The revs are closer, so it's a closer match. If you blip, the clutch can't slip as much, but then again, it doesn't need to.
That just defeats the point of having a slipper clutch in the first place, and no amount of throtle blipping will be enough if you want to go from 6th to 2nd at the end of a fast straight and you are already hard on the brakes and starting to peel into the corner. Then the slipper clutch makes perfect sense, and you will wonder why it has taken so long for devices such as this to appear on the market.
I don't think the vacuum operated Buell/Aprilia clutch will as good as the ball/ramp type under race use (otherwise why do Aprilia RSV racers buy aftermarket slippers?), but I remain to be convinced |
Baggermike
| | Posted on Thursday, March 20, 2008 - 11:01 am: |
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Question.
I have not had any training of any kind so I want to know if this makes thence.
I feel when racing I would not use the rear brake but would downshift fast to match my speed so I can be in the right gear when exiting a turn?
if I brake on the street like if someone where to pull out in front of me I would use the rear brake lightly but down shift hard along with the front break so I feel in racing the rear brake would not be used?
is this true or false?
Mike |
Xl1200r
| | Posted on Thursday, March 20, 2008 - 11:25 am: |
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Trojan - agreed, in that situation it's needed. All I was getting at was blipping the throttle would lessen the effect of the slipper action, but because the revs would be higher then it woudln't really have an effect one way or the other.
But even in your scenario - no amount of blipping would really help - so the bike would be indifferent to it, no? |
Baggermike
| | Posted on Thursday, March 20, 2008 - 11:42 am: |
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If gas was 100 dollars a gallon would you blip the throttle?
I guess I was right and no blipping of throttle on downshifting,
I also wonder it it could hurt performance a little to by adding useless fuel which could fowl up the spark plugs.
I think I am thinking to much.
LOL.
Mike |
Diablo1
| | Posted on Thursday, March 20, 2008 - 06:12 pm: |
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Let me try again. Proper use of the slipper clutch is to not use it at all. Just like proper use of the rev limiter is to not use it at all. Said another way: Are you not using the rev limiter properly if you don't don't bounce off the rev limiter on every shift? |
Zac4mac
| | Posted on Thursday, March 20, 2008 - 08:10 pm: |
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Bingo Diablo1 |
Baggermike
| | Posted on Thursday, March 20, 2008 - 11:52 pm: |
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One is to prevent engine damage,
and the other is to gain control,
am I missing something here.
Mike |
Pariah
| | Posted on Friday, March 21, 2008 - 09:53 am: |
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I think Diablo1 is trying to say that both the rev limiter and slipper clutch should be considered as "backups" that compensate for our human error rather than "primary" features that we rely on (like the brakes or throttle)... |
Slaughter
| | Posted on Friday, March 21, 2008 - 10:10 am: |
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The vacuum-assist/"slipper" functions differently than the back-torque-limiting slipper clutches which use ramp-and-ball type mechanisms.
I'd say the 1125R system functions well within certain limitations but does function based on engine RPM (see above discussions) - whereas the mechanical slipper type clutches can be used more as a racing "tool" when adjusted properly. In those cases, you can drop to the gear you will use on the exit of the turn and the clutch will slip until the "back torque" comes within the limits that were set into the clutch.
In my VERY limited experience on the 1125R at Willow Springs, it is NOT going to make the tranny "idiot proof" (I was the "IDIOT" who accidentally tested the slipper on the bikes more than a few times) - you CAN'T just drop down 2 or 3 gears, pop the clutch and not expect the bike to hop around (I got to try it a couple times) - but it CAN function well as a limited slipper if you're kinda/sorta close on RPMs.
I think it's a usable tool - within limits. Mechanically actuated slippers are quite different and usable in a different way.
(just my own opinion, based on 5 short track sessions - YMMV) |
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