Air in Line?
02-02-2006, 07:10 PM
#1
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Air in Line? Hey Guys,
Just curious, what does it feel like when you have air in the clutch hydraulics? I'm trying to figure out why my Spec 3 is so frustrating on the street while everyone else says theirs drive nearly like stock.
Thanks,
Josh
Just curious, what does it feel like when you have air in the clutch hydraulics? I'm trying to figure out why my Spec 3 is so frustrating on the street while everyone else says theirs drive nearly like stock.
Thanks,
Josh
02-02-2006, 07:25 PM
#2
Hard to feel the difference in the way the pedal 'feels' but, air compresses and can act like a spring in what should be a solid hydraulic connection between the master and slave units. These clutches create more clamping force with higher RPMs and subsequently, more pressure at the pedal too( you won't notice if you mash it to the floor).
That said, put her in 1st gear and rev the engine to about 5500. If your car lunges or moves forward, there is air in the line. The extra force of the clutch pushing back on the slave is compressing the air bubble and allowing the pressure plate to grab the clutch disc. Is you car hard to get in gear at high RPM, but normal at low? That's another indicator of Air in the line.
That said, put her in 1st gear and rev the engine to about 5500. If your car lunges or moves forward, there is air in the line. The extra force of the clutch pushing back on the slave is compressing the air bubble and allowing the pressure plate to grab the clutch disc. Is you car hard to get in gear at high RPM, but normal at low? That's another indicator of Air in the line.
02-02-2006, 10:28 PM
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Cool, thanks for the advice. 
Actually, there's no significant difference in pedal pressure between high and low RPM.
Perhaps the fact I'm using the stock master cylinder is to blame, then? The pedal feels like it rises off the floor with no effect, then suddenly grabs about halfway through the pedal travel, then just pops up. So, nothing... grab... more nothing.
Josh
Actually, there's no significant difference in pedal pressure between high and low RPM. Perhaps the fact I'm using the stock master cylinder is to blame, then? The pedal feels like it rises off the floor with no effect, then suddenly grabs about halfway through the pedal travel, then just pops up. So, nothing... grab... more nothing.
Josh
02-03-2006, 09:35 AM
#4
I'm using the stock master with the drill mod done without any trouble.
"The pedal feels like it rises off the floor with no effect,..." That means the pressure plate and clutch disc have plenty of clearance when the pedal is pushed down. It is not possible to get that to happen with air in the line, especially with the stock master.
"...then suddenly grabs about halfway through the pedal travel, then just pops up. So, nothing... grab... more nothing." This sounds like normal clutch clutch engagement.
The pedal movement above the the 'grab' point in pedal throw is the pressure plate's increasing pressure on the clutch disc.
If there is very little, or no pedal movement after the 'grab' piont when releasing the clutch pedal, it is possible the slave cylinder is shimmed too close to the pressure plate and it is bottoming out before the Pres. plate can apply full clamping force. If this is happening, then you clutch will slip when you dump it at high RPM.
About the pedal pressure change with RPM, yes it very minimal. The only way I can feel it is when I push the pedal in 90% (just before it hits the stopping piont), hold it right there and slap the gas to about 5700 RPM. You'll feel the pedal press back on your foot.
"The pedal feels like it rises off the floor with no effect,..." That means the pressure plate and clutch disc have plenty of clearance when the pedal is pushed down. It is not possible to get that to happen with air in the line, especially with the stock master.
"...then suddenly grabs about halfway through the pedal travel, then just pops up. So, nothing... grab... more nothing." This sounds like normal clutch clutch engagement.
The pedal movement above the the 'grab' point in pedal throw is the pressure plate's increasing pressure on the clutch disc.
If there is very little, or no pedal movement after the 'grab' piont when releasing the clutch pedal, it is possible the slave cylinder is shimmed too close to the pressure plate and it is bottoming out before the Pres. plate can apply full clamping force. If this is happening, then you clutch will slip when you dump it at high RPM.
About the pedal pressure change with RPM, yes it very minimal. The only way I can feel it is when I push the pedal in 90% (just before it hits the stopping piont), hold it right there and slap the gas to about 5700 RPM. You'll feel the pedal press back on your foot.
02-03-2006, 06:41 PM
#6
If the grab point is too close to the floor it will show up as dificult shifting, especially at higher RPM. If you don't have that problem don't worry about it being too close to the floor. But, it should start to grab between 1/4 to 1/2 of the full pedal travel from the floor.
