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Re: And the ECU is *fast*

nak said:
Back of the envelope time:

Spark timing wants to be accurate to one degree or less. Power gains and losses are on the table at 2 degrees error, possibly lots of gains. In my bike tuning days, 2 degrees of error could cause your two-stroke to melt.

So the ECU needs to be able to know crank position something like 360 times the redline. Converting to time, we get:

8,000 RPM * 360 = 2,880,000 degrees per second

RPM is Revolutions Per Minute, not second. So divide your numbers by 60. Shouldn't be any trouble at all for a ECU.
 

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Miguel said:
3rd, acceleration happens at the rear wheels, but deceleration happens mostly in the front wheels. Just pointing it out.
Depends on whether you are braking or lifting...this is why we like rear-wheel drive. :)

4th there is a downforce coeficient that increases with speed and increases your contact patch making your tires more efficient.
Also the air-drag increases with speed.

6th the forces of the road on the tire are null, (action reaction) pressing harder with your hand on a table causes the table to press harder against your hand until a breaking point if the table or the hand cant take it. In quantum physics they say that mater doesn't like to compress.
He has that in there....the normal force (up arrows at the tires) is cancling out the force of gravity from the mass of the car (down arrow in the middle of the car). As you pointed out, the CM of the car is not in the middle of the car...when the blue arrow is moved toward the rear of the car the green arrows will have to change in order to make sure all the torques cancel...we don't want to have a cartwheeling Elise!
 

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Discussion Starter · #63 ·
Thanks for your post, Ara. I'm trying to forget all my college physics, but these guys keep wanting to refresh my memory! :D

I think it likely comes down to a) my rev limiter being set slightly higher than its supposed to, or b) bouncing off the limiter repeatedly at autoxs tends to spike the limit in between terminations.

I'm not too worried either way about it; I believe it highly unlikely I'd have problems with Lotus/Rothrock if there were mechanical problems, and I doubt I'll have any problems of substance in the first 36,000 miles anyway (as I knock on wood). BTW-stellar service by their bodyshop! My car looks brand new, and they also painted my engine covers with the leftover paint, taping off the logo I'd painted. The covers look amazing with the pearl. WOW! Pete Padley get my kudos once again.

:bow:
 

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One thing that is not being considered is that the stopping of acceleration when the rev limiter kicks in is not instantaneous.

As pointed out Jerk is the rate of change of acceleration. When the engine hits the limiter or the driver lifts off, the acceleration change is not instantaneous (large jerk) - it gradually (relatively) tapers off from what ever acceleration rate the car was experiencing to zero acceleration (and then negative acceleration). Depending on how sudden this occurs, the car will still be accelerating a bit past the point when things are "told to stop" accelerating - the engine could easily gain a few more revs before they stop increasing. Unless, of course, there is a large jerk when you hit the rev limiter and the driver and passenger are thrown forward against their seat belts. But since that doesn't happen, there is a much smaller jerk, and the rate of acceleration is (relatively) gradual...
 

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Discussion Starter · #66 ·
My mechanic and body man spoke about the revs, and they said it would NOT be an issue for warranty. The mechanic mentioned to Pete that not all cars will be exact in where the limiter is set.

I have no concerns.
 

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top speed

whats the top speed you have gotten your elise up to?
 

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Discussion Starter · #68 ·
I don't recall off hand. I think it was 130 MPH per the speedometer, but I'll try to dig up my printout again.
 

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TimMullen said:
One thing that is not being considered is that the stopping of acceleration when the rev limiter kicks in is not instantaneous.

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Correct, imo! Remember that not all the energy put out by the engine prior to rev limiter goes into forward momentum. The front of the car lifts, the tires deform to provide forward acceleration, oil is being pressurized through the engine. The oil will continue to flow and pull the components previously pushing it with it after rev limiter hits. A minor thing, but likely to happen to some degree, imo. The tires will unwind from deformity and release its energy after rev limiter. The front of the car will come down releasing its energy. Etc.
 

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The oil is an interesting theory. Take a look at smokey yunik's "power secrets" for an amusing section on that. I don't think you're going to see much power from that tho, esp. if the engine has any kind of oil scraper for the crank. Does anyone know?

As for the energy in the tire's deformation, that will be pulling the other way, and I don't think there is enough energy in the weight transfer to be measureable.
 

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Evl said:
As for the energy in the tire's deformation, that will be pulling the other way, and I don't think there is enough energy in the weight transfer to be measureable.
I think you are quite correct. My bad! :bow:
 

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The answer is so obvious about the rev limiter and higher RPM's

It is the Bristish electrical system sending the impluses to Japan instructing the Japanese engine to limit the revs. Simply a delay in signal.



















I hope no one really takes this comment seriously, but after having read some real doozies here, I have to be carefull and full disclose! ( ha ha ).
 
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