Shifting a manual transmission TOO early

gigabyte2020

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Apr 14, 2016
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Hey guys,
I have a Fiat Siena HL 2001 which is manual 5-gears transmission (like in photo link down) but I want to know something,
when my dad drives it he shifts too early like an early shifts, like when the car starts to move with first gear he instantly shifts to 2nd gear and the car didn't move that much, I already read in google that shifting too early will make the transmission works harder so it will consume more fuel, but am not worried about the fuel, All am worried about is the transmission itself, I mean, will the transmission gonna lose it's power and becomes weak?, like I watched many videos saying that the manual shift should be done before the red-line in the rpm speedometer a little bit. SO the transmission will be able to reach it's red-line or before? or it's gonna be too early? My dad sometimes shifts to 5-gear at 80-90 km/Hr and i know this so bad, but he is like many people in Egypt driving manual cars, most do that and I still know it's bad.. hope I get an answer for my question.
https://imgur.com/W1B8lxs
Thanks <3
 
Solution
Every throttle opening has its own torque curve, and lower throttle openings shift the whole curve to lower RPM. The redline is only appropriate for WOT, as at any throttle opening that is not WOT, the torque curve is moved too far down to lower RPMs.

The object of shifting is to hold the gear until torque starts to drop off, so that upshifting will not put things too low in the RPM curve to produce reasonable torque--if you did it perfectly, the torque produced should match at both RPMs. The point is to maximize the area under the curve, so if you either buzz the engine up to redline well past where it produces good torque, or drop the RPMs too low to produce good torque, you are losing efficiency and wasting fuel.

Your dad...

SoggyTissue

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what your dad is doing is not short shifting. short shifting is done before you reach optimal power band, generally around 2500rpm (varies between cars).

changing too soon results in your engine struggling to provide power and can result in a stall - which is dangerous if youre driving on a road.

using a higher gear to 'pull away' can result in catalytic damage due to improper fuel burn.

depending on how your dad uses the clutch to control the gear change can wear the clutch (clutch slipping)

the gearbox / transmission is an enclosed unit, that as long as its filled with lube, and you dont grind gears (which creates tiny metal shards that will float inside your box) it should be relatively safe because the clutch is the final fail-safe that protects the engine and gearbox (eg it dies to save the engine and gearbox)
 

gigabyte2020

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Apr 14, 2016
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we know about grinding gears, me or him when driving we press the clutch pedal to it's end then shift to higher/lower gears depending on moving or stopping. so again, my transmission won't be weakened? and I won't lose power when shifting properly? I won't do like him of course but was asking how my transmission will do.
 

SoggyTissue

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power at the wheels is determined by your clutch. the way you describe your dad driving, he is going to damage the clutch.

you will lose power at the wheels because your clutch will die, i give it 3-4 years (a normal clutch will last a good 7+) before you start to get slip, and then it will take a month or 2 (with your dad driving) to kill it.

your gearbox and engine will be ok. the clutch is what saves your engine and gearbox.
 

kanewolf

Titan
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IMO, the only way anyone other than you can evaluate his shifting would be to post a video. What I think is short shifting, might be accurate or might be as @SoggyTissue says. We are just guessing. I also said the amount of torque the engine produces is a significant factor. Only hearing the engine and seeing the way he shifts (with a focus on his feet, to see his clutch usage) will tell.
 

gigabyte2020

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before he shifts he press the clutch pedal to it's end, so the gears won't friction with each other. This is the right way as long as i know, all he does is he shifts too early, that's all, but he already knows that he has to press the clutch pedal to it's end before shifting up/down, so no gears-grinding happening here. I was just asking about the transmission, I might go to my mechanic and have my clutch examined to know anything else, Thanks for replying guys, appreciate it :D
 
Is he causing the engine to struggle or shudder? If yes it could wear the engine mounts faster. It won't hurt the transmission. Clutch wear will depend how good you both are at matching engine speed during change, ideally you should not feel the gear change if you get it perfect.
 
Your method of waiting until the RPM's almost red-line to shift to the next gear will consume more fuel. I think the proper time to shift is somewhere in the middle of the RPM scale, not too low, not too close to the red line. As said above, the optimal power band will vary from car to car, but 2,500 RPM seems about right. When I used to drive manual transmission cars, I never explicitly thought about when to shift, it was more intuitive.
 

gigabyte2020

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Engine ain't struggling at all bec. Egypt is one of crowd countires, so he doesn't press gas pedal at max. when early shifting, he goes easy in gas since egypt is crowd as i said. But me I shift before reaching the red-line by a little bit as far as i read and saw in videos on internet (they said it's safer than early or overdraw shifting)
 
Every throttle opening has its own torque curve, and lower throttle openings shift the whole curve to lower RPM. The redline is only appropriate for WOT, as at any throttle opening that is not WOT, the torque curve is moved too far down to lower RPMs.

The object of shifting is to hold the gear until torque starts to drop off, so that upshifting will not put things too low in the RPM curve to produce reasonable torque--if you did it perfectly, the torque produced should match at both RPMs. The point is to maximize the area under the curve, so if you either buzz the engine up to redline well past where it produces good torque, or drop the RPMs too low to produce good torque, you are losing efficiency and wasting fuel.

Your dad may have learned to drive when carburetors didn't control fuel/air ratios as precisely, and relatively large throttle openings at low RPM were best for efficiency. Back then, if you opened the throttle to just before where WOT fuel enrichment occurred (and selected gears to match that), you would get the most efficiency at the expense of highest NOx emissions because it would run leanest. With modern fuel injection maps to precisely control emissions, this is no longer the case, but gasoline engines are still more efficient at larger throttle openings and lower RPM because it doesn't need to waste as much power pumping exhaust against atmospheric pressure, and there is less friction at lower RPM.

With a diesel this goes out the window because technically they run at WOT all of the time, so can operate it at high efficiency even at very low "throttle." But the Fiat Siena does not appear to be available with a diesel engine.

Manual transmission life will not be affected by high or low RPMs. The life is entirely determined by wear on the synchronizers, which is made worse by moving the shift lever too quickly. The only reason that double-clutching (which is also releasing the clutch once when in neutral) improves their lifespan is because it forces you to pause the lever before engaging the synchro.
 
Solution

gigabyte2020

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Apr 14, 2016
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Does wide opened throttle means pressing the gas-pedal to it's end, like to achieve maximum performance?