Help - clutch pedal pushing back at be at high rev shifts
Discussion
Cheers Paul,
from reading it - it sound like he is aying the restiction is in the master cylinder end, just below the crimped on end. But you were saying you think it is more to do with the basic size of the pipe as well and the size of the restrictions in each end.
DO you think the larger bore pipes and restrictors are needed on both sided ofthe through out bearing?
>> Edited by jellison on Tuesday 25th October 14:36
from reading it - it sound like he is aying the restiction is in the master cylinder end, just below the crimped on end. But you were saying you think it is more to do with the basic size of the pipe as well and the size of the restrictions in each end.
DO you think the larger bore pipes and restrictors are needed on both sided ofthe through out bearing?
>> Edited by jellison on Tuesday 25th October 14:36
Not sure if that problem sounds like yours ??
That issue, would basically cause the clutch to be lazy, or slow under foot.
Picture you trying to force the fluid through a very small hole. It cannot pass as fast as your foot wants to. So you would feel resistance all the time. Then letting your foot off, the clutch would be very slow to release, making it prone to slipping.
BMW's have the same problem. they design this into the cars, to make the clutches operation smoothed for the driver.
After driving mates Monaro, I can say its clutch feels horrible comapred to my own car, and we will be addressing the pipe in the near future. It is a slightly different setup to the US cars, but the design problem is still built in.
I guess, like my other post, it could see a scenario where the clutch ends up fully depressed. I dont see that effecting shifts, as long as your foot is fully down on the pedal, but it could make the clutch prone to slipping.
That issue, would basically cause the clutch to be lazy, or slow under foot.
Picture you trying to force the fluid through a very small hole. It cannot pass as fast as your foot wants to. So you would feel resistance all the time. Then letting your foot off, the clutch would be very slow to release, making it prone to slipping.
BMW's have the same problem. they design this into the cars, to make the clutches operation smoothed for the driver.
After driving mates Monaro, I can say its clutch feels horrible comapred to my own car, and we will be addressing the pipe in the near future. It is a slightly different setup to the US cars, but the design problem is still built in.
I guess, like my other post, it could see a scenario where the clutch ends up fully depressed. I dont see that effecting shifts, as long as your foot is fully down on the pedal, but it could make the clutch prone to slipping.
It is the weird pushing back at you the clutch (like someone pushing harder than your from the other side of the pedal) happened a week or to ago while hooning around Windsor with mate in Tuscan - really nailing it for a few open miles. then on gentle run home loose clutch unless do this granny shifting then it come back - I bleed the release bearing via the master cylinder (can do this without jacking up as no slave), but master was not down on fluid (which I was expecting!
If wearing clutch out does sound like I might need some custom larger bore hoses and end (id) - same connector thread adaptor on od obviously!.
Then as Paul was telling me cut two 4" hole through the belhousing to undo the pipes remove an replace with new before replacing with larger bore, bleed system and cover holes with alloy plates.
Paul - can you get these made up or let me know here you get ours made up?
Think my father had the braided bits custom made, so maye able to go back to same people for larger bore.
Getting my box out with the fitting in TVR will be a bugger easy to take engine and tran out! So as you can see the holes route sound like the one for me, don't want clutch going!
If wearing clutch out does sound like I might need some custom larger bore hoses and end (id) - same connector thread adaptor on od obviously!.
Then as Paul was telling me cut two 4" hole through the belhousing to undo the pipes remove an replace with new before replacing with larger bore, bleed system and cover holes with alloy plates.
Paul - can you get these made up or let me know here you get ours made up?
Think my father had the braided bits custom made, so maye able to go back to same people for larger bore.
Getting my box out with the fitting in TVR will be a bugger easy to take engine and tran out! So as you can see the holes route sound like the one for me, don't want clutch going!
I used -4 on mine, which is more than enough for any clutch setup. On my old Rover engine, they were only -3 brake line size, and even it was fine, although certainly not ideal.
What sort of master cylinder and lines are you using ?
Mines just a Girling 3/4" bore master with remote reservoir, feeding a -4 line to the hyd bearing via the stock quick disconnect. The exit hole in the MC is still quite small, although Ive never measured it.
You say you bleed via the master as there is no slave ????? Dont quite understand that ?
The hydraulic release bearing IS your slave cylinder.
I wouldnt be into cutting 4" holes in my bellhousing !!!!
Can you unbolt the box from the bellhousing to remove it from the car ?? leaving the bellhousing bolted to the engine.
My T56 comes apart that way, and actually makes for very easy box removal. Much easier than its ever been.
Remove box, then bellhousing seperately to get at the clutch.
What sort of master cylinder and lines are you using ?
Mines just a Girling 3/4" bore master with remote reservoir, feeding a -4 line to the hyd bearing via the stock quick disconnect. The exit hole in the MC is still quite small, although Ive never measured it.
You say you bleed via the master as there is no slave ????? Dont quite understand that ?
The hydraulic release bearing IS your slave cylinder.
I wouldnt be into cutting 4" holes in my bellhousing !!!!
Can you unbolt the box from the bellhousing to remove it from the car ?? leaving the bellhousing bolted to the engine.
My T56 comes apart that way, and actually makes for very easy box removal. Much easier than its ever been.
Remove box, then bellhousing seperately to get at the clutch.
stevieturbo said:the master is the std TVR one (almost impossibel to get at (car seems to be made around some of the parts bolted in at earlier time!). -4 / -3 is this a size? Hoses were made special for the release / master to connect end with briaded hose in middle.
I used -4 on mine, which is more than enough for any clutch setup. On my old Rover engine, they were only -3 brake line size, and even it was fine, although certainly not ideal.
What sort of master cylinder and lines are you using ?
Mines just a Girling 3/4" bore master with remote reservoir, feeding a -4 line to the hyd bearing via the stock quick disconnect. The exit hole in the MC is still quite small, although Ive never measured it.
You say you bleed via the master as there is no slave ????? Dont quite understand that ?
The hydraulic release bearing IS your slave cylinder.
I wouldnt be into cutting 4" holes in my bellhousing !!!!
Can you unbolt the box from the bellhousing to remove it from the car ?? leaving the bellhousing bolted to the engine.
My T56 comes apart that way, and actually makes for very easy box removal. Much easier than its ever been.
Remove box, then bellhousing seperately to get at the clutch.
I mean't I bleed mine back at the master cylinder (the bleed line running back to here and just coiled up here under a cover so bleed a bit top master up a bit - sorry for confusion. Box is TKO600 wit t56 bellhousing as per Monaro / Vette.
I just wonder if I could pull the box off the bellhousing enough to get at the unions to undo them and feed back through the holes / grommets in th side of the bell housing and then do reverse with larger bore pipes reconnect and slid box back in that way?
Taking off the bellhousing will be a bugger and inclined more to take the engine and box out - 1 or 2 days!
-4 or -3, typical hose sizes when using JIC or AN fittings, braided hose etc
-4 refers to 4/16" inch, -3 3/16" with -3 commonly found on braided hoses for brakes.
What sort of clutch are you using ?
What sort of actual release bearing ? ( not the hydraulic part )
Is the hydraulic bearing seated properly on the gearbox ?
I know you've bled it, but is there any air in the system ?
Any idea what size bore the TVR master is ? How much travel you have at the rod of the master.
Mine is 3/4" bore, with about 1" of travel, and seems to work good, and should be very close to stock LS1 cars. If anything I might be shifting a bit more fluid than them on full stroke of the pedal.
-4 refers to 4/16" inch, -3 3/16" with -3 commonly found on braided hoses for brakes.
What sort of clutch are you using ?
What sort of actual release bearing ? ( not the hydraulic part )
Is the hydraulic bearing seated properly on the gearbox ?
I know you've bled it, but is there any air in the system ?
Any idea what size bore the TVR master is ? How much travel you have at the rod of the master.
Mine is 3/4" bore, with about 1" of travel, and seems to work good, and should be very close to stock LS1 cars. If anything I might be shifting a bit more fluid than them on full stroke of the pedal.
stevieturbo said:
-4 or -3, typical hose sizes when using JIC or AN fittings, braided hose etc
-4 refers to 4/16" inch, -3 3/16" with -3 commonly found on braided hoses for brakes.
What sort of clutch are you using ?
What sort of actual release bearing ? ( not the hydraulic part )
Is the hydraulic bearing seated properly on the gearbox ?
I know you've bled it, but is there any air in the system ?
Any idea what size bore the TVR master is ? How much travel you have at the rod of the master.
Mine is 3/4" bore, with about 1" of travel, and seems to work good, and should be very close to stock LS1 cars. If anything I might be shifting a bit more fluid than them on full stroke of the pedal.
checking on sizes - but fathers say the one being used are the same spec as used on Porsches with 400+bhp.
The clutch is a LUK std Corvette clutch as would be fitted to std LS6 / Z06 C5 - likely same as Holdens!?
Father has come up with the below:-
I think what’s going on is the LUK clutch has to move 10mm to dis-engage the clutch, on conventional
clutches this would be 3mm to 5mm, therefore the extra 5mm on every stroke of the LUK clutch is that much more fluid moving in the system.
On say 3 rapid changes the amount of fluid moving back and forth is twice that of a conventional clutch and this leads to fluid/pressure stacking up in the system due to the fact it can’t return fluid back into the master cylinder because the BORE of the master cylinder can’t cope with the volume of fluid/pressure trying return back into it.
If you open the Bore size the pressure reduces allowing more fluid to return to the master cylinder, eliminating the problem.
SEE below info taken from AP’s web pages, let’s say your cylinder is 0.625” and you move up to 0.70” the difference in line pressure is reduced by 165.26 p.s.i.
This may well be sufficient to solve the problem. If you look at the line pressures it’s easy to see why the pedal is difficult to over come in this situation.
NEED TO INVERSTERGATE this route, opening up the pipes is only reducing line pressure by another means the most sensible is to go after the Master Cylinder
it’s easier and addresses the problem head on at the route cause.
Our most popular master cylinder ranges now consist of up to 10 different bore sizes from 14.0mm to 25.4mm (1.0"
. The table below shows the range of bore sizes available and shows the % step up from the previous size and line pressure based on 50 lb pedal load and a 5 to 1 pedal ratio
Master Cylinder Size mm/in.
14.00/
0.551"
15.00/
0.591"
15.875/
0.625"
16.80/
0.661"
17.78/
0.70"
19.05/
0.75"
20.638/
0.8125"
22.225/
0.875"
23.813/
0.9375"
25.4/
1.00"
Area sq in.
0.2386
0.2739
0.3068
0.3436
0.3848
0.4418
0.5185
0.6013
0.6903
0.7854
% step up from previous size
N/A
14.8%
12.0%
12.0%
12.0%
14.8%
17.4%
16.0%
14.8%
13.8%
Pedal Load lb.
50
50
50
50
50
50
50
50
50
50
Pedal Ratio
5:1
5:1
5:1
5:1
5:1
5:1
5:1
5:1
5:1
5:1
Line Pressure p.s.i. (single cylinder)
1047.76
912.72
814.87
727.61
649.61
565.88
482.17
415.75
362.17
318.31
We have now been in touch with AP - seem it is a known issue to them and is likely it is nothing to do with the pipes or sizes as the one we have shoul dbe fine - they seem to think it is the HUGE 12" clutch at those revs, the finger somehow staying out more than the should or something. SLower shift should keep it ok for time being - basically anyoone with a monster motor getting these issues needs a smaller diameter twin plate AP or similar clutch - I'll be looking to the US next year.
Pressure in the hydraulic line will be dictated by the force against the relese bearing/slave. Nothing else. If there is no force against it, all you are doing is moving fluid.
Pipe diameter wont effect it.
Different hydraulic leverage and pedal leverage may effect pedal feel, and length of travel, but presure within the hydraulic line will remain the same, as you are pushing against the exact same force every time. The clutch.
My clutch hydraulic setup is virtually identical to what I used on my RV8, with both Rover box, and then Supra.
IMO, I doubt 3-5mm of travel at the cover would release any diaphram style clutch. 10-12mm sounds more realistic, although its something Ive never measured.
Stroke is dictated by pedal travel, and master/slave cylinder bore size. NOT the actual clutch itself.
I revved the std LS6 clutch to at most 6500rpm when I had the std engine+blower. Never had a problem, until it started slipping as it couldnt hold the power.
My current clutch the Textralia, is also full diameter, single plate, and occasionally rev to about 6800rpm. Never had a problem shifting. I happen to go through the gears pretty quickly on mine.... On a good run, I'm into 4th in under 8 secs
Even flat shifting on occasion it works fine.
What bore is the piping you are using for the clutch hydraulics ? 4-5mm ID should be plenty
Pipe diameter wont effect it.
Different hydraulic leverage and pedal leverage may effect pedal feel, and length of travel, but presure within the hydraulic line will remain the same, as you are pushing against the exact same force every time. The clutch.
My clutch hydraulic setup is virtually identical to what I used on my RV8, with both Rover box, and then Supra.
IMO, I doubt 3-5mm of travel at the cover would release any diaphram style clutch. 10-12mm sounds more realistic, although its something Ive never measured.
Stroke is dictated by pedal travel, and master/slave cylinder bore size. NOT the actual clutch itself.
I revved the std LS6 clutch to at most 6500rpm when I had the std engine+blower. Never had a problem, until it started slipping as it couldnt hold the power.
My current clutch the Textralia, is also full diameter, single plate, and occasionally rev to about 6800rpm. Never had a problem shifting. I happen to go through the gears pretty quickly on mine.... On a good run, I'm into 4th in under 8 secs
Even flat shifting on occasion it works fine.
What bore is the piping you are using for the clutch hydraulics ? 4-5mm ID should be plenty
stevieturbo said:I'll ask. AP seem to think it is the finger being thrown out by the huge interia from a very larger clutch pushing the release bearing back some!?
Pressure in the hydraulic line will be dictated by the force against the relese bearing/slave. Nothing else. If there is no force against it, all you are doing is moving fluid.
Pipe diameter wont effect it.
Different hydraulic leverage and pedal leverage may effect pedal feel, and length of travel, but presure within the hydraulic line will remain the same, as you are pushing against the exact same force every time. The clutch.
My clutch hydraulic setup is virtually identical to what I used on my RV8, with both Rover box, and then Supra.
IMO, I doubt 3-5mm of travel at the cover would release any diaphram style clutch. 10-12mm sounds more realistic, although its something Ive never measured.
Stroke is dictated by pedal travel, and master/slave cylinder bore size. NOT the actual clutch itself.
I revved the std LS6 clutch to at most 6500rpm when I had the std engine+blower. Never had a problem, until it started slipping as it couldnt hold the power.
My current clutch the Textralia, is also full diameter, single plate, and occasionally rev to about 6800rpm. Never had a problem shifting. I happen to go through the gears pretty quickly on mine.... On a good run, I'm into 4th in under 8 secs
Even flat shifting on occasion it works fine.
What bore is the piping you are using for the clutch hydraulics ? 4-5mm ID should be plenty
jellison said:
I'll ask. AP seem to think it is the finger being thrown out by the huge interia from a very larger clutch pushing the release bearing back some!?
I find that very hard to believe.
While the clutch cover, and plate may be large diameter, the fingers arent much different to any other clutch, and have a similar diameter at the release bearing.
Your clutch etc is totally standard, as is your LS6 ( near enough )
I would think thats enough reason to look elsewhere for your problem.
Given the Slave and master combo is a little bit of an unknown for use with the LS1, Thats where I'd be looking.
How does the pedal actually feel under foot ?
Does it have a nice quick movement ? Good spring return pressure when you let off ?
Can you feel the fingers go over centre when foot is fully depressed ?
Where is the biting point ?
What bore is your MC now ?
How much stroke to you have at the MC ?
As I said, mine is 3/4" bore, with approx 1" stroke, which as best as I could tell is exactly what a factory LS1 MC has.
Does it feel like there is air in the system ?
Pedal should have a hard spring against it, from very little movement. If it feels soft at all for a bit of travel, and then a hard spring, you could have air in it.
If there is air in it, pedal will probably bite very close to the floor, and make gearchanges difficult.
How much stroke to you have at the MC ?
As I said, mine is 3/4" bore, with approx 1" stroke, which as best as I could tell is exactly what a factory LS1 MC has.
Does it feel like there is air in the system ?
Pedal should have a hard spring against it, from very little movement. If it feels soft at all for a bit of travel, and then a hard spring, you could have air in it.
If there is air in it, pedal will probably bite very close to the floor, and make gearchanges difficult.
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