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      03-22-2011, 08:54 AM   #1
BanziBarn
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Remap - high gear, low revs - Clutch?

Just having a conversation with someone at work who is thinking of getting a remap and I said that the main thing to worry about is the clutch, and that if he got one, he should avoid heavy throttle, high gear, low rev combinations.

Someone has queried that this would be a problem so I just wanted to clear it up.

My understanding is that in high gears, and low revs you are putting a lot of torque through the clutch and that over time, this could shorten it's life.

The car in question is a diesel so it can be very tempting to become lazy with gear changes and just plant your foot to make progress.

Am I talking rubbish?
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Last edited by BanziBarn; 03-22-2011 at 10:38 AM.
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      03-22-2011, 10:07 AM   #2
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Quote:
Originally Posted by BanziBarn View Post
Am I talking rubbish?
without the word "avoid" then I'd have to say, yes, you are....


But seriously, I'd say thats a reasonable theory....
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      03-22-2011, 10:38 AM   #3
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Ta! 'Avoid' now added!
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      03-22-2011, 11:14 AM   #4
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You are talking rubbish ......

1. Peak flywheel (thus clutch) torque is at exactly the peak torque rpm of the engine - check your engine spec for that.

2. The clutch is on the gearbox input / primary shaft so its torque loading is not effected by gear selection, it will always be handling the engine output torque.

3. When your foot is OFF the clutch, ie. it is locked solid, then NO wear will occur, regardless of torque etc (within reason), as there is no movement between the flywheel and pressure plate thus no wear can occur.

4. Gearbox output torque is INCREASED in lower gears not higher gears, so the highest torque loading on gearbox output shaft / mountings / transmission / driveshafts etc would be full throttle, peak engine torque in FIRST gear! (thus why the wheels spin in first and not in sixth)

Clutch wear only occurs when changing gear or pulling away, so heavy starts and careless gearshifts, exacerbated by a remap will cause you problems in the longterm.

A quick calc reveals that a 335d in first gear has a WHEEL torque of approx 4750 lbft!!! but the torque converter / flywheel torque is still only 400lbft or so.

If you only give it full beans when the clutch is fully engaged, then you've really got nowt to worry about.

Last edited by doughboy; 03-22-2011 at 11:43 AM.
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      03-22-2011, 12:07 PM   #5
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Cool, very clear!

I'll report back that I was wrong.

Cheers
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