what would happen?
04-20-2003, 03:26 AM
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what would happen?
ok, in a piston engine, if u run it in redline for too long, the piston(s) might shoot thru the hood.
what would happen in a rotary engine if u run it in redline too long?
what would happen in a rotary engine if u run it in redline too long?
04-20-2003, 05:26 AM
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On a piston engine, the tension and compression loads on the connecting rods from inertia at redline are greater than the loads from the power the engine produces. Rev too high, and the rods will fail.
On a rotary, the eccentric shaft flexes, which can lead to the rotors being forced against the side plates or even smashing the tips of the rotor (not just the apex seals) against the inside of the rotor housing. You can run into trouble with the rotor gears, too, I think.
That is my understanding of what happens at the limits. I haven't ever over-revved a rotary or piston engine to the point of damaging it myself, so I am just passing on what I have heard.
-Max
On a rotary, the eccentric shaft flexes, which can lead to the rotors being forced against the side plates or even smashing the tips of the rotor (not just the apex seals) against the inside of the rotor housing. You can run into trouble with the rotor gears, too, I think.
That is my understanding of what happens at the limits. I haven't ever over-revved a rotary or piston engine to the point of damaging it myself, so I am just passing on what I have heard.
-Max
04-20-2003, 05:26 PM
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...sounds about right to me Max...
in a naturally aspirated application, the liklihood of a seal failing from pinging is pretty low (unless someone trys to tune the motor up hard, and they suck at it... badly), so really if you overrev the engine (was covered in that thread called Money Shift) the outer gears and e-shaft wouldn't be able to support the rotor at those speeds, and they would fail, the rotor would smoke the perhipheral housing probably seazing the engine, but certainly ruining it.
unless you're truly stupid with how you drive the car, you dont' need to worry about overrevving: the electronic limit at 9500rpm should be WELL within the tolerances of the engine (ie: it's not like if you rev to 9600 your poor rotor-motor will destroy itslef), and the only way you could really overrev the engine like that is if you went from a high rpm and downshifted while accelerating, rather than upshifting... which would be silly, obviously.
in a naturally aspirated application, the liklihood of a seal failing from pinging is pretty low (unless someone trys to tune the motor up hard, and they suck at it... badly), so really if you overrev the engine (was covered in that thread called Money Shift) the outer gears and e-shaft wouldn't be able to support the rotor at those speeds, and they would fail, the rotor would smoke the perhipheral housing probably seazing the engine, but certainly ruining it.
unless you're truly stupid with how you drive the car, you dont' need to worry about overrevving: the electronic limit at 9500rpm should be WELL within the tolerances of the engine (ie: it's not like if you rev to 9600 your poor rotor-motor will destroy itslef), and the only way you could really overrev the engine like that is if you went from a high rpm and downshifted while accelerating, rather than upshifting... which would be silly, obviously.
04-20-2003, 05:33 PM
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Redline on a piston engine almost has nothing to do with the connecting rods, and bearings.
It has to do with the valvetrain. Valve float & bounce
F1 engines run with the limit of mean piston speed of about 25m/s~95mm bore
So does BMW's S54 (M3 engine) 24.266 87mm bore 91mm stoke 8000 redline
Honda S2000 24.9, 87mm bore 84mm stroke 8900 redline
Even lesser engines redline at under 20m/s mean piston speed.
It has to do with the valvetrain. Valve float & bounce
F1 engines run with the limit of mean piston speed of about 25m/s~95mm bore
So does BMW's S54 (M3 engine) 24.266 87mm bore 91mm stoke 8000 redline
Honda S2000 24.9, 87mm bore 84mm stroke 8900 redline
Even lesser engines redline at under 20m/s mean piston speed.
Last edited by MikeW; 04-20-2003 at 06:31 PM.
04-20-2003, 05:44 PM
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Originally posted by MikeW
Redline on a piston engine almost has nothing to do with the connecting rods, and bearings.
It has to do with the valvetrain.
F1 engines run with the limit of mean piston speed of about 25m/s~95mm bore
So does BMW's S54 (M3 engine) 24.266 87mm bore
Honda S2000 25.5 86mm bore
Even lesser engines redline at under 20m/s mean piston speed.
Redline on a piston engine almost has nothing to do with the connecting rods, and bearings.
It has to do with the valvetrain.
F1 engines run with the limit of mean piston speed of about 25m/s~95mm bore
So does BMW's S54 (M3 engine) 24.266 87mm bore
Honda S2000 25.5 86mm bore
Even lesser engines redline at under 20m/s mean piston speed.
but yes, certainly valve-train effectiveness and durability would be the largest factor, which is why most of the development of hush-hush tech goes into valve actuation in F1... BMW has some kind of Nitrogen system, i believe, and many factories have pneumatic systems, as the 16krpm "limits" (you can always continue to step up the limits) of the rotating cam aren't good enough anymore... never mind trying to move a tiny, fragile thing like that and not shatter it... valve-bounce, and whatnot...
but... yeah.
04-20-2003, 07:22 PM
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what am i missing?
it seems unlikely to me that the eccentric shaft would break, as the rotor is in constant contact with all 3 sides of the housing. Thus the housing, not the e shaft would be taking most of the damage. If the e shaft did break, it would only be because the housing broke first. This is just theory, so please mention anything I'm missing ...
As far as damage, there might also cause "chatter marks" on the housing if the engine is revved too high. This was a major problem on earlier rotaries, and its been fixed now. Nonetheless, weird things can happen at high rpms ...
As far as damage, there might also cause "chatter marks" on the housing if the engine is revved too high. This was a major problem on earlier rotaries, and its been fixed now. Nonetheless, weird things can happen at high rpms ...
04-21-2003, 12:33 AM
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Re: what am i missing?
Originally posted by vipeRX7
it seems unlikely to me that the eccentric shaft would break, as the rotor is in constant contact with all 3 sides of the housing.
As far as damage, there might also cause "chatter marks" on the housing if the engine is revved too high.
it seems unlikely to me that the eccentric shaft would break, as the rotor is in constant contact with all 3 sides of the housing.
As far as damage, there might also cause "chatter marks" on the housing if the engine is revved too high.
and i just wanted to point out that the rotor doesn't QUITE touch the housing, it really just floats inside it (albiet very close) with all the (aptly named) seals projecting from every which side and edge of the thing which maintain the (funny enough) seal between the chambers, and the oil moving around in there...
OH!! and i was gonna say that with the very light seals and well-tuned tension springs, chatter marks shouldn't be a worry (as you said)
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