Accidentally shifted into 3rd instead of 5th

[Intuit]

Can anyone imagine a piston moving up then down, over 133 times, in a single second? A single up then down stroke takes just 0.0075 seconds. Imagine the forces involved? I wonder what kind of oil pressures are required to keep the parts from making contact? Shavings? With those numbers, if anything happens, it's going to happen split-second quick... not going to have any time... any chance to save it. People who do this, should keep in mind that race engines are frequently rebuilt. Depending on the level, it may be once a season (if it makes it a season) or even once a race.

 

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Can anyone imagine a piston moving up then down, over 133 times, in a single second? A single up then down stroke takes just 0.0075 seconds. Imagine the forces involved? I wonder what kind of oil pressures are required to keep the parts from making contact? Shavings? With those numbers, if anything happens, it's going to happen split-second quick... not going to have any time... any chance to save it. People who do this, should keep in mind that race engines are frequently rebuilt. Depending on the level, it may be once a season (if it makes it a season) or even once a race.

32,000 rpm? Redo your math.

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[RAAMaudio]

Anyway, they move damn fast and the "money shift" has happened even with very experienced racers. It was real easy to kill and engine in some of the BMWs and they cost a bundle to build, knew of far to many popped ones, why I sent to an LS for my M3 race car build.

Also I run a 3 way shift light, 200 RPM below redline, brighter and faster blinking at redline and super bright at 200 over redline. That way I can watch the track or road instead of the tack and if hit third instead of 5th, etc...as soon as the clutch engages it lights up like mad instantly so I just dump the clutch right back in. $250 shift light has saved me an engine or two, or more, faster lap times and safer at the limit driving, pretty cheap piece of gear to do all that

 

[Intuit]

32,000 rpm? Redo your math.

133.33 Rounds * 60 seconds equals 32,000RPM? Okay, I believe you.

 

[blurred]

133.33 Rounds * 60 seconds equals 32,000RPM? Okay, I believe you.

A piston in a 4 cylinder car hits tdc 133 times in one second at 32,000 rpm. You were trying to calculate for 8000rpm. But you failed to account for the fact that the rpm is based on crank rotation so you need to divide by 4 pistons which hit tdc once per crank rotation....



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[Intuit]

A piston in a 4 cylinder car hits tdc 133 times in one second at 32,000 rpm. You were trying to calculate for 8000rpm. But you failed to account for the fact that the rpm is based on crank rotation so you need to divide by 4 pistons which hit tdc once per crank rotation....

It wasn't a failure to calculate based on crank rotation, it was purely based on that; ignoring cylinder count. By the logic you're describing, an eight cylinder engine's crankshaft is going to spin at half the speed of a four cylinder while displaying the same RPM on the gauge.
https://en.wikipedia.org/wiki/Tachometer#In_automobiles.2C_trucks.2C_tractors_and_aircraft
The Wiki definition doesn't mention piston count or TDC, just crankshaft rotation.

I'll do a little more searching later to verify your definition. If you're right, then I stand corrected and thank you for the information. If your definition is incorrect, I'm glad you brought it up regardless as you're probably not the only person who understands it that way. (interesting)

 

[blurred]

It wasn't a failure to calculate based on crank rotation, it was purely based on that; ignoring cylinder count. By the logic you're describing, an eight cylinder engine's crankshaft is going to spin at half the speed of a four cylinder while displaying the same RPM on the gauge.
https://en.wikipedia.org/wiki/Tachometer#In_automobiles.2C_trucks.2C_tractors_and_aircraft
The Wiki definition doesn't mention piston count or TDC, just crankshaft rotation.

I'll do a little more searching later to verify your definition. If you're right, then I stand corrected and thank you for the information. If your definition is incorrect, I'm glad you brought it up regardless as you're probably not the only person who understands it that way. (interesting)

I didn't check the link, just re did my math now that I'm awake lol.

You are correct, I was way off base.

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[M-Sport fan]

Also I run a 3 way shift light, 200 RPM below redline, brighter and faster blinking at redline and super bright at 200 over redline. That way I can watch the track or road instead of the tack and if hit third instead of 5th, etc...as soon as the clutch engages it lights up like mad instantly so I just dump the clutch right back in. $250 shift light has saved me an engine or two, or more, faster lap times and safer at the limit driving, pretty cheap piece of gear to do all that

^^^Cartek, AiM??

Also, you've stated earlier in this thread that the factory set "hard limit" is 7700 revs.

WHAT is the factory set/tune 'soft limit', or where the limiter effects start to take effect, and how exactly does our factory ECU limiter work (i.e.; fuel cut, spark cut, FULL boost dump, all of the above in a sequence/combination , ?? )??

I ask because sometimes on the street (on ramps, etc.) I hit what feels like a HARD limit which has the sensation of a TOTAL boost dump, at ~6500-6600 revs.

 

[Intuit]

I didn't check the link, just re did my math now that I'm awake lol.

You are correct, I was way off base.

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Yeah when you break it down, it really is unbelievable ain't it? I can understand the doubt. Even 5,000 RPM sounds unbelievable; over 83 strokes in a single second; one stroke taking just 0.012 second. You hadn't expressed any disagreement but, from that standpoint it becomes clear that the engineers set these "limits" for good reasons.

https://en.wikipedia.org/wiki/Engine_displacement
It occurred to me that you were probably thinking about engine displacement calculations, which do at least, take cylinder count into consideration. Many years ago I used to *assume* that the "5.0" on a Mustang for instance, was a per-cylinder displacement reference because, who builds an engine with different displacement, per-cylinder right? So that displacement is actually spread across, (presumably evenly,) all cylinders; whether it had six or eight.

(RAMBLE WARNING)
If you maintained similar rod and piston characteristics while spreading that 5.0 across four cylinders (instead of eight) then your piston bores are going to be much, much larger... which would potentially lower red-line due to the increased reciprocating masses.

From a naturally-aspirated engine longevity standpoint, that's why I'd rather floor it at 1.3k versus unnecessarily running my RPMs way up there. IIRC that engine had, 190/210 compression across all cylinders at ~310,000 miles; 90% of OEM peak spec for a new engine. Hard on the accelerator but shifted low and kept my RPMs low. (for that engine it was useless to do >4.5k RPM anyway) Only internal work performed was a leaky head gasket replacement, and the resultant cracked head repaired. RPM versus wear strategy on a turbo or super-charged engine may differ depending on whether the lubrication system was designed for the increased cylinder pressures. For one thing, the additional RPM may be needed for cooling.

 

[RAAMaudio]

Factory hard limit has been breached according to something I heard recently but I would only do so on a fully built engine as it is correct to assume RPMs are killers of a long life for an engine unless designed for it and built right to begin with or rebuilt to handle it. Extreme example was the insane high RPM and lower output of the prior NA F1 engines.

Stock rev limit might indeed be a hard one at 6500, I do not remember as it as been going on 3 years since I ran the stock rev limit, mine has been at 7300 for a long time and it is not a soft cut there either.

I chose 7000 for the first stage, 7200 for the redline for a bit of cushion then 7400 for the third stage which I only see if miss a gear down shifting, not high enough damage anything, hopefully, and not something I have seen more than once or twice.

I have an Autometer unit that has served me well in quite a few cars in the many years I have owned it, long forgot the model number.

It has a digital tach readout which makes setting it up really easy.