What is double-clutching?

Doing a quick Google search reveals that this question has been covered quite a bit, but I found that the explanations not to be very clear or completely wrong. I thought I would try to answer this question as if I were giving it to someone with only limited automotive knowledge…

Although the concept of double clutching is easy to understand, the reason ‘why’ its needed might not be. Here’s the definition in a nutshell – Double-clutching is a manual technique used to match the rotational speed of the gears in a non-synchromesh transmission to the rotational speed of the engine.

Here’s what actually happens: The first push of the clutch is to take the transmission out of gear and then to move the shifter so that the transmission is in neutral. The clutch pedal is then released while the transmission is in neutral so that the engine is only turning the transmissions input shaft (layshaft). Now, the driver will rev the engine so that the layshaft speed is matching the output shaft speed. The output shaft speed will be determined by how fast the car is going, so the driver will have to select a gear that will keep the engine revs in a acceptable range – this process is called “Rev Matching”. The second push of the clutch is used to enter the next gear. If the driver does not have the revs matched correctly, a grinding sound will occur because of the difference in speed between the shafts which determines the rotational speed of the gears that are on them. If the shifter does move into gear, usually accompanied with a ‘clunk’ because its very hard to get the revs match perfectly, the clutch is finally released connecting the engine to the rest of the drive line.

And there you have it.

It should be noted that no modern car needs to be double-clutched. All modern manual transmissions have a device called a synchromesh which does the job double-clutching was intended to do. So, this technique is pretty much reserved for the history books except for a very few special cases.

 

Frustrating issues with the race car

For some time now, I have been troubleshooting my old 3rd generation F-body trying to tie up loose ends and problems that have existed for a long time. Right now, I am stuck and cannot seem to find whats wrong with the engine. Cylinders 1 and 7 are quite a bit colder than all the others, cylinder 7 is the worst and is running 400 degrees down.

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What you should know about wheel spacers

I have been working hard lately on my old 1989 Pontiac Firebird to get it back on the road. We (my brother and I) recently got it running with a Megasquirt II and I have been tying up loose ends so it can go to the dyno without incident.  There has been one issue that has plagued the car for as long as we can remember, and its something that we really wanted to get sorted out before taking the car to be dynoed.

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Setting initial timing on a small block Chevy (SBC)

This is a little how-to for setting the initial ignition timing on a small block Chevy before its ever been run.

Note* this post assumes that you already know how to time a running engine, just not one that never been run before or has had its distributor removed and its timing settings lost.

**Updated to be more clear**

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Ever been ripped off by a mechanic?

If you use one, chances are you have. Strangely enough, since I always have done my own work, I have never known how bad it was. It wasn’t until a friend contacted me and wanted my opinion on what he thought was an unusually high bill that I learned that the business model of these shops were specifically designed to rip people off.

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Absurd – 54.5 mpg mandate by 2025.

I couldn’t believe it when I read it. It was announced today (8/28/12) that the Obama administration has mandated a 54.5 mpg CAFE (corporate average fuel economy) standard by 2025. The funny thing is, I was just thinking how the 35.5 mpg CAFE standard, which will be enforced by 2016, was already going to change the auto industry, the types of cars we drive, and what its going to do to enthusiasts like us. But, this 2025 standard is far more draconian.

You can read the official release about the 54.5 mpg standard on the EPA website here: http://yosemite.epa.gov/opa/admpress.nsf/79c090e81f0578738525781f0043619b/13f44fb4e2c2d39d85257a68005d0154!OpenDocument


The new government approved car…

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Stoptech Street Performance Pads review

Just got back from a test and tune at Gingerman Raceway in South Haven Michigan. Its been about 10 years since I have been to the track and they have since revised the course layout with a new turn creating a faster straight. If you have followed my posts in the past, you would know that I have had issues finding pads that are a good balance for both street and an occasional track day. Anyhow, I went out this time with Stop Tech Street Performance pads and am quite happy with the results.

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The Corvette and the future C7

A friend of mine who has owned many Porsche’s and exotic cars over the years is, to the shock of his exotic car friends, looking to get an older Corvette Z06. This has made me think a lot about the Corvette and some of the BS that the big magazines publish about every new Corvette on the horizon.

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