Ignition rev 6 and Kaboom?
#31
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Actually not even close. I checked mine for fun all the time after a good run up the hills. My badge of honor: 44677 range 1, 3337 range 2, and 60 range 30. Never a missed shift.
#32
Rennlist Member
#34
#35
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I am not so sure about this....... It counts "ignitions" and not revolutions in some band .... what if you let the clutch out but don't apply gas... and shoot the RPMs up into band 6? Most computers are smart to cut gas for mileage if nothing else. When you car coasts down a hill, you are in gear and you let off the gas and coast, the computer cuts gas..... so no ignitions????
I have tracked live values from my Durametric and the car accuratly tracks RPM, digitally. Why doesn't the computer track RPMs in these higher bands and only "ignitions"? If the engine is spinning in an upper range in a danger zone, why doesn't it just track RPMs and time? The data is certainly there.
This may be more complex than we think... the computer may be exactly correct and functioning properly. The problem may be in our understanding.
Peace
Bruce in Philly
I have tracked live values from my Durametric and the car accuratly tracks RPM, digitally. Why doesn't the computer track RPMs in these higher bands and only "ignitions"? If the engine is spinning in an upper range in a danger zone, why doesn't it just track RPMs and time? The data is certainly there.
This may be more complex than we think... the computer may be exactly correct and functioning properly. The problem may be in our understanding.
Peace
Bruce in Philly
Bruce,
My understanding is that it tracks ignitions because very small amounts of time in these higher RPM bands can be damaging to the engine. To your first point the engine will still have an ignition event even though you are off the gas - you're off the gas when you idle and the engine is still going. (Interestingly Porsche use a variation on this in the new turbo Boxster/911 engines to stop turbo lag - take your foot off the gas and it cuts fuel but keeps the throttle bodies open to keep the turbo spinning.)
Also the DME is measuring time between ignitions, and translating this to an RPM number. The engine also typically measures the ignition events relative to Cylinder 1 Top dead center - the engine management typically counts the teeth on the flywheel to time the ignitions. Hence the RPM you see on Durametric is possibly gained from this data - the ignition timing data is a much more fine grained dataset than RPM. You have to have one revolution to measure RPM but there are three ignitions per revolution so by measuring timing between ignitions you can tell if the engine spent one third of a revolution at a certain speed or RPM.
Hence to Quadcammers point I think that you can happily have a report as the first example - a very sudden spike ('money shift') in RPM does not necessarily have to read larger ignition counts in the lower ranges, at least to my understanding as the engine does not have to turn a whole revolution for the DME to log ignitions in a particular range. It's just going to depend on how sudden the spike in RPM is.
Hope this helps!!
#36
Three Wheelin'
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My understanding is that selecting Sport mode (when you have SC option) changes the rev limiter characteristic so that ignition is not cut and you can "ride" the limiter. This could be advantageous for track days or autocross where a shift change would not be practical. I don't have sport chrono so I am only going by what I recall reading on RL.
#37
RL Community Team
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Bruce,
My understanding is that it tracks ignitions because very small amounts of time in these higher RPM bands can be damaging to the engine. To your first point the engine will still have an ignition event even though you are off the gas - you're off the gas when you idle and the engine is still going. (Interestingly Porsche use a variation on this in the new turbo Boxster/911 engines to stop turbo lag - take your foot off the gas and it cuts fuel but keeps the throttle bodies open to keep the turbo spinning.)
Also the DME is measuring time between ignitions, and translating this to an RPM number. The engine also typically measures the ignition events relative to Cylinder 1 Top dead center - the engine management typically counts the teeth on the flywheel to time the ignitions. Hence the RPM you see on Durametric is possibly gained from this data - the ignition timing data is a much more fine grained dataset than RPM. You have to have one revolution to measure RPM but there are three ignitions per revolution so by measuring timing between ignitions you can tell if the engine spent one third of a revolution at a certain speed or RPM.
Hence to Quadcammers point I think that you can happily have a report as the first example - a very sudden spike ('money shift') in RPM does not necessarily have to read larger ignition counts in the lower ranges, at least to my understanding as the engine does not have to turn a whole revolution for the DME to log ignitions in a particular range. It's just going to depend on how sudden the spike in RPM is.
Hope this helps!!
My understanding is that it tracks ignitions because very small amounts of time in these higher RPM bands can be damaging to the engine. To your first point the engine will still have an ignition event even though you are off the gas - you're off the gas when you idle and the engine is still going. (Interestingly Porsche use a variation on this in the new turbo Boxster/911 engines to stop turbo lag - take your foot off the gas and it cuts fuel but keeps the throttle bodies open to keep the turbo spinning.)
Also the DME is measuring time between ignitions, and translating this to an RPM number. The engine also typically measures the ignition events relative to Cylinder 1 Top dead center - the engine management typically counts the teeth on the flywheel to time the ignitions. Hence the RPM you see on Durametric is possibly gained from this data - the ignition timing data is a much more fine grained dataset than RPM. You have to have one revolution to measure RPM but there are three ignitions per revolution so by measuring timing between ignitions you can tell if the engine spent one third of a revolution at a certain speed or RPM.
Hence to Quadcammers point I think that you can happily have a report as the first example - a very sudden spike ('money shift') in RPM does not necessarily have to read larger ignition counts in the lower ranges, at least to my understanding as the engine does not have to turn a whole revolution for the DME to log ignitions in a particular range. It's just going to depend on how sudden the spike in RPM is.
Hope this helps!!
So..... do you ever see erroneous readouts? Are these oddball numbers actually accurate?
Peace
Bruce in Philly
#38
Rennlist Member
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Hence to Quadcammers point I think that you can happily have a report as the first example - a very sudden spike ('money shift') in RPM does not necessarily have to read larger ignition counts in the lower ranges, at least to my understanding as the engine does not have to turn a whole revolution for the DME to log ignitions in a particular range. It's just going to depend on how sudden the spike in RPM is.
Hope this helps!!
Hope this helps!!
#39
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Yes to my understanding this is correct. Now how many that get logged in the lower ranges will depend on how sharp the 'spike' in engine RPM is.
#41
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Bruce - I have no data on erroneous readouts and so would not want to pass an opinion. There are lots of factors and you'd have to get down into the weeds on the electronic architecture of the system, of instance did they implement Error Checking on the memory? If not there is a statistical probability of random 'bit flips' inducing errors in the data.
A random error would be truly random though - you are as likely to get 10,000 ignitions in a range by random error as you are 1.
Are small numbers truly accurate? You'd have to understand the sensors in the system and see if there was electrical 'noise' induced that would cause these and where in the system the noise is generated.
So likely they are accurate? I don't know and there are likely other factors I've not considered.
I would run away from a used car with range 4- 6 events though!
Hope this helps...
#42
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Whilst I understand that there is a possibility that an engine could be rapidly accelerated through an rpm range, surely it would not decelerate at the same rate?
For example, the aforementioned shift from 5th to 2nd could spike the RPMs quickly as the clutch engaged. If you then pushed in the clutch, the engine will take time to slow down (inertia effects) and the I would anticipte that over revs would register through the ranges as the engine slows down.
Applying some simple maths to the data listed in post #1, and assuming that the raise through the over rev ranges was instantaneous (probably not possible), this would indicate that the engine slowed from 9500 rpm (range 6) to 7700 rpm (range 2) in around 30 milliseconds (and 4 1/3 revolutions of the crankshaft). I'm no expert, but this seems implausible and supports the idea of a software glitch.
For example, the aforementioned shift from 5th to 2nd could spike the RPMs quickly as the clutch engaged. If you then pushed in the clutch, the engine will take time to slow down (inertia effects) and the I would anticipte that over revs would register through the ranges as the engine slows down.
Applying some simple maths to the data listed in post #1, and assuming that the raise through the over rev ranges was instantaneous (probably not possible), this would indicate that the engine slowed from 9500 rpm (range 6) to 7700 rpm (range 2) in around 30 milliseconds (and 4 1/3 revolutions of the crankshaft). I'm no expert, but this seems implausible and supports the idea of a software glitch.
#43
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Not necessarily - if you 'money shift' the mass and inertia of the car push the rpm up - if you hit range 6 and stay there for 1/10 second you'll log 2700 ignitions in range 6.
Disengage the clutch and there is no gas being fed to the engine as long as the rpm drops through the lower ranges faster than it was held above 6 you would see fewer events in these ranges than in range 6.
Now caveat emptor and see Glyndellis post above I don't know how quickly the pistons decelerate from ~9000 rpm down with clutch disengaged and I suspect that unless someone wants to log the ignition events at or near redline under these circumstances we probably never will!
It is worth noting though that an 'event' even down in range 2 is an extremely small slice of time. 3 ignitions per revolution at 7700 rpm means that a revolution is taking ~12 milliseconds and ignition events are every 4 milliseconds - this is range 2 - below the redline so it kinda makes the mind boggle a bit if you think we are looking at time slices that are below your perception..vs a persons reaction time on a money shift event to push the clutch back in after realizing a mistake..
#44
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Whilst I understand that there is a possibility that an engine could be rapidly accelerated through an rpm range, surely it would not decelerate at the same rate?
For example, the aforementioned shift from 5th to 2nd could spike the RPMs quickly as the clutch engaged. If you then pushed in the clutch, the engine will take time to slow down (inertia effects) and the I would anticipte that over revs would register through the ranges as the engine slows down.
Applying some simple maths to the data listed in post #1, and assuming that the raise through the over rev ranges was instantaneous (probably not possible), this would indicate that the engine slowed from 9500 rpm (range 6) to 7700 rpm (range 2) in around 30 milliseconds (and 4 1/3 revolutions of the crankshaft). I'm no expert, but this seems implausible and supports the idea of a software glitch.
For example, the aforementioned shift from 5th to 2nd could spike the RPMs quickly as the clutch engaged. If you then pushed in the clutch, the engine will take time to slow down (inertia effects) and the I would anticipte that over revs would register through the ranges as the engine slows down.
Applying some simple maths to the data listed in post #1, and assuming that the raise through the over rev ranges was instantaneous (probably not possible), this would indicate that the engine slowed from 9500 rpm (range 6) to 7700 rpm (range 2) in around 30 milliseconds (and 4 1/3 revolutions of the crankshaft). I'm no expert, but this seems implausible and supports the idea of a software glitch.