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Tuesday, July 29, 2014

Embracing the Clutch: Tips and Hints

Have you, do you currently, or do you want in the future to drive a standard, manual, stick shift transmission? If so, this one is for you.  

There are some distinct advantages to a manual transmissions, and a few minor drawbacks too.  Its no secret among my friends and clients that I really don't like automatic transmissions, but I do recognize they have their place in some applications.  I get great clutch life from my vehicles, and great performance on the street or off road.  I prefer my vehicle with a third pedal, thanks, and here are my basic rules to getting the most value from that third pedal.  

There are many benefits to owning and driving a manual transmission vehicle.  Being able to more quickly adapt to changing driving conditions with forethought instead of only reacting after things change as an automatic transmission does, more accurate and fine control of acceleration and deceleration, and a more fun and visceral connection to the road and machine are the primary reasons people choose to own a manual transmission equipped vehicle.  Not to mention the interaction of human and machine helps to relieve road weariness and prevent driver fatigue as quickly. 

Manual transmissions are simpler in many ways and have nowhere near the number of moving parts as an automatic.  Manual transmissions are generally tougher, longer lasting, easier to repair and change fluids, and also lighter weight. An automatic transmission wastes fuel through slippage unless it locks the torque converter between shifts whereas a manual transmission is locked to the engine when the clutch pedal is released, assuring that all the power from the engine goes to the wheels not wasted as heat from fluid shear.

The purpose of the clutch is to allow a smooth transition from stopped to moving by slipping slightly between the engine, spinning  many hundreds of RPM even at idle and the transmission shaft connected to the wheels on the ground, which are all completely stopped.  The clutch absorbs the difference in speed between the engine and transmission by slipping and wasting energy as heat.   Any time the clutch pedal is in the middle of its throw, neither fully in and released, free to spin; or out and completely locked together as one unit spinning together, the clutch is wearing out and being damaged by heat.

So, the first rule of a clutch pedal is get your foot off of it. Period.  No exceptions.  Either the clutch pedal is on its way in and held there, or on its way out, but it is not a foot rest. Keeping any additional, even slight and gentle, pressure on the clutch pedal results in faster release bearing wear, slippage of the clutch, and increased heat in the clutch housing.  

Next rule:  Keep the engine revved only the minimum needed to obtain smooth operation and no higher during initial engagement and startup in first gear.  Most automotive engines produce smooth power around 1000 RPM and this is generally an excellent engine speed to start off at.  A little more throttle may be necessary on a hill or accelerating hard into traffic, but overall, the lower the speed of the engine during startup, the better for clutch longevity and eliminating heat build up. 

The higher the engines speed during clutch release, the more energy is wasted as heat in the clutch housing due to slippage and friction.  This heat buildup can ruin engine and transmission seals from long term overheating and can drastically shorten the life of the clutch from glazing and polishing of the surfaces involved. 

The way I explain starting from a stop to rookie drivers of manual transmission is like this: I recommend getting your left foot off the clutch as quicky and smoothly as possible without over-revving the engine while eliminating bucking or lurching.  Thats it...

I teach newcomers to manual transmissions to start the vehicle nice and smooth on flat pavement with no accelerator pedal use at all.  Get the car up and rolling with the clutch pedal all the way out as quick as possible with no accelerator use whatsoever.  None, No go pedal.  Just pull your right foot up to the seat and use only your left foot to engage and release the clutch.  Get as smooth and fast as you can, and when you can do that fast and easy, then you can add a bit of throttle to make the transition faster yet.

When shifting gears, the rule is the same as starting out, smooth and fast.  Shifting should be a much faster transition of clutch pedal position than starting from a stop.  Clutch in; shift gears; clutch out- done.   That fast, that smooth.  No bucking or lurching or whiplash.  Smooth like velvet.  

The shock to the system from too rapid a release of the clutch can break parts in the drive systems, can ruin rubber or plastic mounts, tear tires or destroy shocks, struts, bearings or driveshafts.  Not to mention giving your passengers a lifetime of neck pain.  Again, the keyword is smooth.  

Over revving and under revving of the engine are another point worthy of touching on briefly.  Every engine has a powerband, a range of engine speeds that produce maximum peak horsepower.  The 'wider' the powerband, the greater the range of RPM that the engine can produce power most efficiently and thus the greatest acceleration.  Generally speaking, for engine longevity, most situations dictate keeping engine RPM in the bottom 1/3 of the powerband when not accelerating.  Each engine is different, but having 2/3 or more of the overall power the engine is capable of at the touch of the skinny pedal is wise in most conditions. 

Over-revving causes unnecessary and rapid engine wear and wastes fuel.  If an engine will produce the power to accelerate in a higher gear, upshift.  If you shift into a higher gear and lose speed immediately, downshift and accelerate rapidly to a higher speed to prevent speed loss again when you aupshift.  If need be, slow down and stay in a lower gear if the engine cannot make enough power in the higher gear.  Its a 'feel' thing.  Let the engine work where it is happiest.

If you need to accelerate, don't be afraid to use the higher RPM range of the engine, but if you are just cruising along, use the highest gear possible that allows the engine to run smoothly without chugging.  If you push the accelerator down and the engine speed does not increase immediately, you are in too high a gear for the speed and you need to downshift to a lower gear.  This is referred to as 'lugging' the engine and causes overheating of valves and pistons and rapid wear on the piston sides and skirts as well as added bearing damage.

Downshifting early before climbing or descending a hill is a wise tactic as opposed to letting the speed change significantly and then expending additional energy as fuel or wasted in the brakes to bring the vehicle back to desired speed.  If you upshift out of 3rd gear into 4th at 80kph (55mph)then you can downshift onto third gear at roughly that same speed.  Never downshift into a lower gear at a speed significantly higher than you would upshift out of that gear when accelerating.  This action can over-rev an engine and potentially cause severe damage.  

This article turned out longer than I thought it would be, but I think I covered all the important points.  I hope it clears up some misconceptions and increases the life and reliability of your clutch and other related parts.  Also, hopefully I converted a few drivers away from wasteful automatics back to simpler, cheaper, longer lasting manuals.  After operating a manual transmission for a few hours, most people are comfortable and capable and no longer need to think about the process.  So don't be afraid of that third pedal, make use of it and enjoy it.  Relish the ability to interact as a driver instead of being chained to a computer that tries to think for you, keeps you passively bored, and takes away your control and enjoyment of the driving experience.

Happy driving happy drivers...




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