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irish07 02-19-2014 07:05 AM


Originally Posted by XWCGT (Post 4051122)
its possible, but not likely. the clutch TOB is not subjected to heat that could even come close to boiling even the worst of fluids. and certainly, the heat wouldn't be transferred at higher RPM at any faster rate to cause this water In the lines to boil and create a falling pedal that comes back at the lower rpm.
How does the high rpm crate heat from what " friction torque"??? what do you mean by this?


what is causing the soft pedal is high rpm, and it has to be related to forces due to the high rpm... its not a heat caused effect.
If you are working on "them" , I suppose you are talking about AMV8s, right? if not, then you might not know what kind of TOB and actuation mechanism we are speaking about. im thinking its due to some issue in the hydraulics of the TOB itself.

Friction torque=Torque transfer..it's the transfer of torque through friction..aka the friction disc in the clutch assembly. A clutch works in the reverse method of a brake system in relation to friction..In brakes friction is used to slow down the vehicle, with a clutch friction is used to move the vehicle forward...obviously you understand, both methods create heat. If you had a ASM car you would get a warming when creeping the car on a hill for "Clutch Overheating"..A clutch can reach 190C which is why on the new ASM3 setup various automatic clutch learns are performed due to the expansion in the aluminum, there is a high amount of aluminum in the ASM3 clutch assembly which would cause slippage if not relearned at given clutch heat temps...

Going off topic with ASM3 before but just trying to state, a clutch setup will get hot enough, surely not as high compared to brakes in temp..Although I've seen more blue spotted flywheels than overheated brake discs, due to teh very slow heat reduction...if the TOB does not see this heat like your mentioning, then why is the TOB contact cap that applies pressure to the diaphragm get blue spotting as well?..LOL that little b*tch is getting pretty hot ;) ..Remember there is no constant air flow in that bellhousing/torque tube assembly to cool down the clutch..yet on brake we have front air dams to help keep things cool and when needed cool down faster..

If there was no air/water in the clutch system and temps were normal(perfect world), then only other way your high rpm would drop the hydraulic clutch pedal is if the diaphragm was weak/faulty and collapsing in, this would result in slippage at high rpm also..and drop the clutch pedal but only slightly, which I doubt this could be felt on a hydraulic setup, mechanical setup though is common, I've had this on one of my cars when the stock clutch was in place running the strip with too much power(a Mustang with T5 OEM clutch)..

Nonetheless..we've turned this into a jacked thread belonging to 007 Vantage..sry bud

007 Vantage 02-19-2014 08:56 AM

It's on the bottle itself, 10% less compressible. Replace the fluid yourself if you don't believe me. Performance brake fluid does improve pedal feedback. Not going to argue sometime that is common knowledge amongst thousand of track guys for over a decade.

With that's said both of you are wrong :), found out my clutch softness had nothing to do with bleeding. It's the slave cylinder going out. Not shockingly this is a very common problem on the Ford mustangs (which many of the parts we share in common). Only Way to replace is wait until the clutch job. And in order to do clutch job headers have to come out, so I will just wait to do headers and slave once stock clutch goes (which may not be for another 10k probably.)

Either way, clutch & brake fluid feels much better, and pedal firmness and feedback has improved significantly over stock (even compared to my previous aston).

Brake pedal never experiences any fade no matter how hard I push it, only the clutch gets soft under extreme driving due to slave cylinder seals slowly giving way.

irish07 02-19-2014 09:04 AM


Originally Posted by 007 Vantage (Post 4051296)
It's on the bottle itself, 10% less compressible. Replace the fluid yourself if you don't believe me. Performance brake fluid does improve pedal feedback. Not going to argue sometime that is common knowledge amongst thousand of track guys.

With that's said found out my clutch softness had nothing to do with bleeding. It's the slave cylinder going out. Not shockingly this is a very common problem on the Ford mustangs (which many of the parts we share in common).

Do realize mustangs don't have slave nor master cyl's for the clutch, there mechanical with cable and self adjusting quadrants..there not hydraulic

Was your slave leaking?.. There's no way it will walk out on it's own unless pressure was given up in the diaphragm(which would mean the diaphragm is faulty)..When the pedal is not touched, the slave is fully compressed..I'm interested in what you found?

XWCGT 02-19-2014 01:38 PM


Originally Posted by irish07 (Post 4051305)
Do realize mustangs don't have slave nor master cyl's for the clutch, there mechanical with cable and self adjusting quadrants..there not hydraulic

Was your slave leaking?.. There's no way it will walk out on it's own unless pressure was given up in the diaphragm(which would mean the diaphragm is faulty)..When the pedal is not touched, the slave is fully compressed..I'm interested in what you found?

When the master goes bad, all sorts of weird things can happen It can engage on its own, because pressure is never netrualized with release of the pedal and of course, the pedal can go to the floor. but, my point was usually, it cant come back just because the RPM is lower on the engine. thas the strange part hear. its vibration related, and maybe that is effecting the master and leaking fluid through the seals internally.

XWCGT 02-19-2014 01:44 PM


Originally Posted by irish07 (Post 4051206)
Friction torque=Torque transfer..it's the transfer of torque through friction..aka the friction disc in the clutch assembly. A clutch works in the reverse method of a brake system in relation to friction..In brakes friction is used to slow down the vehicle, with a clutch friction is used to move the vehicle forward...obviously you understand, both methods create heat. If you had a ASM car you would get a warming when creeping the car on a hill for "Clutch Overheating"..A clutch can reach 190C which is why on the new ASM3 setup various automatic clutch learns are performed due to the expansion in the aluminum, there is a high amount of aluminum in the ASM3 clutch assembly which would cause slippage if not relearned at given clutch heat temps...

Going off topic with ASM3 before but just trying to state, a clutch setup will get hot enough, surely not as high compared to brakes in temp..Although I've seen more blue spotted flywheels than overheated brake discs, due to teh very slow heat reduction...if the TOB does not see this heat like your mentioning, then why is the TOB contact cap that applies pressure to the diaphragm get blue spotting as well?..LOL that little b*tch is getting pretty hot ;) ..Remember there is no constant air flow in that bellhousing/torque tube assembly to cool down the clutch..yet on brake we have front air dams to help keep things cool and when needed cool down faster..

If there was no air/water in the clutch system and temps were normal(perfect world), then only other way your high rpm would drop the hydraulic clutch pedal is if the diaphragm was weak/faulty and collapsing in, this would result in slippage at high rpm also..and drop the clutch pedal but only slightly, which I doubt this could be felt on a hydraulic setup, mechanical setup though is common, I've had this on one of my cars when the stock clutch was in place running the strip with too much power(a Mustang with T5 OEM clutch)..

Nonetheless..we've turned this into a jacked thread belonging to 007 Vantage..sry bud

No, there is no "transfer of torque, through friction". once the clutch is let out, there both the pressure plate and clutch plate and flywheel are spinning at the same speed, through compression of the plates with a huge clamping force, so there is NO friction. acceleration of the driveline is caused by the engine flywheel and everything else is along for the ride. only in the transmission, is there any heat generated via the losses between gear teeth. automatics are an entirely different story and we are not talking about them here.

I dont think the OP was talking about high rpm via slipping the clutch. he was talking about spirited high rpm driving and when the rpm was high, his clutch pedal fell. if you drive the car properly and are not drag racing, you should get very little clutch wear. ive had a stock clutch on the race car for over 10 years and 120 races with no measurable wear on the clutch discs.
however, if you were driving in SF up hills, from many full stops, that might not be the case.

XWCGT 02-19-2014 01:50 PM


Originally Posted by 007 Vantage (Post 4051296)
It's on the bottle itself, 10% less compressible. Replace the fluid yourself if you don't believe me. Performance brake fluid does improve pedal feedback. Not going to argue sometime that is common knowledge amongst thousand of track guys for over a decade.

.

what is on the bottle . I have a hard time believing that, but certainly would if you could show me some proof. 10% compressibility difference is HUGE. remember we are comparing two or more "racing " type fluids here, not the 3 dollar bottle of prestone brake fluid dot 3.
dot 4 to dot 4. show me where there is a 10% compressibility factor.

Again, the main reason for using the better racing fluid is to add to its life before changing due to its hygroscopic characteristics, and its boiling points after the fluid has been in the system for a while. SRF has great wet boiling point numbers, this is true.
pedal feel from super blue ATE, stoptech, or others vs SRF will be undetectable, unless what you say is true about the 10% differnce in compressibility.


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