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Discussion Starter #1
They ran my computer printout again for some reason, and something jumped out at me big time: Maximum Engine Speeds.

My top five are as follows:

Max RPM 1 = 8802
Max RPM 2 = 8745
Max RPM 3 = 8737
Max RPM 4 = 8729
Max RPM 5 = 8716

Now, isn't redline and the rev limiter set at 8600? If so, I either have a malfunction in my telemetry, or my rev limiter was set much higher. Any ideas?

I can post that section of the tape if anyone is interested. Oh, yeah-still no standing starts. :D
 

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The rev limiter does not come into play if you downshift and thereby force the engine rpms higher.
 

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Discussion Starter #3
I guarantee I never downshifted and sent the RPMs over 8600. That would be insane.
 

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shay2nak
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doesn't the fuel cut-off come in if you pass a certain RPM? If the cutoff is 8700, then how would he be able to register those numbers?
 

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Come on Surferjer, we know you've been downshifting to 2nd at 70+ miles an hour. Those speed shifted 40mph down shifts to 1st at the auto-x's (locking the rears for affect) don't help either! I've hit the rev limiter a few times in 2nd and 3rd gear but it didn't seem like the rpm's were at 8700+ rpms. Perhaps the cut off still allows a little more due to the inertia of moving parts? I'm no engineer but doesn't this seem possible?
 

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Seems like those numbers are all much too close together to all have happened from downshifting. Maybe the source of the discprepency with the fuel cuttoff limit will be more clear after more people start getting this type of "later in life" ECU printouts
 

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Discussion Starter #8
I hope you're joking, Dan! I have downshifted to make a pass on a highway, but only to get RPMs close to 6200 for the VV kick, never over. As for autoXs, I don't think I've ever come out of a turn feeling a need to downshift at over 25 MPH, so that's not it. I'm perplexed, which is why I posted. :confused:
 

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shay2nak said:
doesn't the fuel cut-off come in if you pass a certain RPM? If the cutoff is 8700, then how would he be able to register those numbers?
How do you know that?
 

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As I understand it, the Elise has two triggers for the rev limiter. One is after N seconds at X RPM. The other is instant at Y RPM.

I think maybe Jerry has found the value of Y (note that the numbers won't necessarily be consistent because the tach reading is sampled every so often and won't catch the RPM exactly when it hits the threshold).

Does anyone know what X, Y, and N are supposed to be? Don't trust your tachometer; I don't know of any car where the tach is exactly right.
 

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If you are accelarating hard and the rev limiteer comes in at 8600, isn't it possible to "overrun" the 8600 rpm limit? The tires and engine are connected at that point and the car is accelarating, couldn't it pull the engine higher by 150 - 200 rpm?
 

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James A said:
The tires and engine are connected at that point and the car is accelarating, couldn't it pull the engine higher by 150 - 200 rpm?
Acceleration stops immedatately once you stop applying power. A body in motion maintains its speed (not acceleration) if no external forces are applied to it.
 

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ConeFusion said:
Acceleration stops immedatately once you stop applying power. A body in motion maintains its speed (not acceleration) if no external forces are applied to it.
Very true, but I suspect there is a lag between the engine hitting 8700rpm (probably the instantaneous rev limit), the computer figureing out how fast the engine is spinning, then cutting off the pulses to the injectors, and finally, the fuel in the intake runners being sucked up.

Notice how each gear is a little lower than the one before it. Since the acceleration is more rapid in lower gears, the car can get a little further ahead of the computer.

I would hope that lotus doesn't have a problem with this, or they should have put the rev limit lower.

Edit: If anyone at lotus gives you a hard time, I can tell you that the test drivers they have running the driver experience at hethel didn't bat an eye when I was running up against it. Of course they didn't bat an eye when another student lost the rear view mirror on a tire wall either. :D
 

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I think it is crank/engine momentum upon releasing the load...assume you are indeed running the rpms up to rev limit territory.. the moment you push the clutch it and the loading is released and at the same time you release the accelerator the engine momentum is causing the engine to gain a 100 rpm or so...not much thus not noticeable. This happens a lot when AutoXing....my thoughts anyway
Michael
 

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I agree, you can get recordings around the 8800 rpm range. After all my car had this within the first half hour of the engines life :( (Before it left the factory I think) Doesn't seem to have hurt anything though.
 

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so whatis the accuracy of the data? 2% range?
 

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LotusLust said:
so whatis the accuracy of the data? 2% range?
I don't see a reason why it wouldn't be highly accurate. The ECU needs a reliable crank sensor signal, otherwise it wouldn't be able to control the ignition precisely. So unless it doesn't have a reasonably precise clock, it should be able to measure the rpm's without much error.

The tach needle is a different story, the analog display might not be very precise.
 

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shay2nak
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babak said:
How do you know that?
Know what? The existence of the cutoff or the 8700 limit?
 

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Shay,
If you mechanically force the engine revs higher than what is prudent (e.g. downshift), a limiter cannot react quick enough to stop it from happening in most cases. Another example is the SMG M3s that were registering revs above the redline. One would think that this situation would not be possible, given the electronic user interface. Recall that in S6 transmission mode (quickest shifts), DSC must be turned off. Several drivers approached redline, were about to pull the right paddle and hit a rough bump, sending the rear wheels into a sudden unloaded state which caused revs to spike before the computer could react. In fact, several M3 owners have crashed this way, after foolishly turning DSC off. Not all M owners are M drivers, as goes thet saying on Roadfly.
 
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