Rev at p or n gear ..
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Trying to hear the popping of the exhaust ..
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Because without load on the engine (at the wheels) all the internals are more or less floating.
Its not what they are designed for.
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Been revving engines in my cars at traffic lights and in parking lots at meetups for decades without issue. Did that in Dad's cars back in the day too, and they were automatic.
So the idea is that the engine, without stress from the transmission being engaged, will blow up or be damaged because there's no mechanical stress placed on the engine from wheels turning? Never heard this reasoning before.
Edit: I do have to confess - I did break the motor mounts in Mom's LTD and Dad wasn't happy
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You've heard that you cannot overrev a 718 PDK. The reason is that if you reach the red line and keep your foot down, it will give you the next gear (if you are on 7th and approaching the red line you are going down a very steep cliff). If you downshift and the shift in the new gear will lead you over the red line, the PDK will not give you the shift.
If you are on P or N the PDK cannot play with the gears and you could go past the red line. Hence, a rev limiter for P and N.
If you are on P or N the PDK cannot play with the gears and you could go past the red line. Hence, a rev limiter for P and N.
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Spoken like a true software engineer. (FWIW, I are one to.) Actually it makes perfect sense from a control standpoint.
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FWIW, Here's a little related infoBeen revving engines in my cars at traffic lights and in parking lots at meetups for decades without issue. Did that in Dad's cars back in the day too, and they were automatic.
So the idea is that the engine, without stress from the transmission being engaged, will blow up or be damaged because there's no mechanical stress placed on the engine from wheels turning? Never heard this reasoning before.
Edit: I do have to confess - I did break the motor mounts in Mom's LTD and Dad wasn't happy
"When the transmission is in neutral and the engine is “revved” without any load, the spinning engine internals will accelerate, gathering rotational and lateral forces at a faster rate than designed by the manufacturer.
Why will the engine wear? (not an exhaustive list):
Piston compression ring expansion
Rapidly revving an engine will heat up the piston rings much faster. Because they have a much smaller thermal mass than the cylinder liners they expand at different rates. If the compression rings expand too much, they will generate increased friction on the cylinder liners, causing the cylinder liners to wear out (reducing compression).
In the worst case scenario, the compression ring ends touch, pinch the cylinder liner and will most likely cause the piston to crack. Then you’ll have metal fragments flying around destroying the head and cylinder.
On a very cold engine or while lean (not enough fuel), it is easier to get a larger thermal differentiation between the cylinder liner and piston rings.
General, the cooling system is NOT able to help, as piston failure happens within 4-10 milliseconds after a hotspot develops on a piston or compression ring.
Oil system starvation
More common in continued over revving - the cylinder head & block doesn’t drain the oil at the same rate that oil is pumped out of the sump, leaving the sump empty.
This can also be caused if the block uses the same pipes to drain the oil that is also used to ventilate the sump causing oil vaporisation. However the engine would most likely already be overheating for this to occur.
Some poorly designed oil pumps (and water pumps too) can aerate and are unable to pump oil when increased in rpm too rapidly.
Connecting rod (conrod) warping
Some conrods will stretch/bend during excessive rpm acceleration. Worst case scenario is it will put greater unbalanced forces on the crankshaft and bearings (higher compression ratio only needs 10 thou). If the engine has tight tolerances it will also bend valves.
Crankshaft warping
The crankshaft or engine block isn’t designed to withstand such a sudden increase in internal force (similar to harmonic imbalances). It only takes a thou or two (0.0254 - 0.0508 millimetres) for the crankshaft to gouge a main bearing. This is common in performance & motorsport engines so they have increased strength built into the block by adding more ribs and webbing to the cast or billet."
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I found the source for your post. There really is no basis for these conclusions as they are not from any specific manufacturer and specifically Porsche. As a matter of fact there's no citation as to whom they may be accredited to. Additionally there are many responses that dispute the conclusions. Many respondents call them "rumors".
That said, it's reasonable to believe that it's probably not a good idea to sit in the car revving it for hours on end. However I'm sure countless people repeatedly rev their engines to warm them in order to get some heat in the cabin when it's cold outside.
That said, it's reasonable to believe that it's probably not a good idea to sit in the car revving it for hours on end. However I'm sure countless people repeatedly rev their engines to warm them in order to get some heat in the cabin when it's cold outside.
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Funny but the first three days I was unable to rev at idle past 4500 rpm. Today, after driving a whopping 200 miles, I was able to rev a touch past 7000 in neutral (manual transmission). Maybe there's a nanny limiter? I have read (here) that the over-rev counter can be triggered by revving at idle (so that means in those situations there wasn't an electronic limiter). I only did it to see what difference I could hear without the 7.5 amp secret fuse for the soundaktor (and of course I'm hearing things, all sorts of good things...).
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It used to said that mechanical engineers build weapons, civil engineers build targets.I am a REAL engineer (Civil
From the title I thought it was about transistor design.
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