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Revs / Power Bands, Etc


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#31 Pete Gaimari

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Posted Sep 01 2015 - 02:39 PM

True. :)

#32 David Wright Lo67

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Posted Sep 01 2015 - 02:41 PM

View PostJohn Woods, on Sep 01 2015 - 11:54 AM, said:


Did all 60s era F1 cars use the synchro'd sequential ZF?


No.  Lotus were the first team to adopt the ZF box with the Lotus 25, keeping it for the 33.  The 43 used a BRM box but the 49 reverted to ZF.  However, in 68 Lotus switched to the Hewland box for the 49B.  Cooper used a ZF box for the T-81, but went to Hewland for the T-86.

#33 Pete Gaimari

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Posted Sep 01 2015 - 02:43 PM

What's your opinion of using the clutch with the ZF tranny David? Was it used?

#34 Wozza_UK

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Posted Sep 01 2015 - 04:26 PM

I thought the idea was to shift up at 'peak bhp' then continue in that gear all the way to 'peak bhp' again, then change up again. The redline comes a little AFTER peak bhp and is to be avoided due to the risk of damaging the engine. It's the theoretical maximum revs the engine will take.

You short shift in order to either eliminate wheel spin in a low gear, or if it makes the next corner more comfortable, or if going downhill.

Where in Setup Manager does it give these bhp/rev limit figures? There are two graphs but I've never been able to make head nor tail of them apart from using one of them to get an idea of gear spread.

#35 Pete Gaimari

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Posted Sep 01 2015 - 04:58 PM

I've run full GP while shifting the Lotus at 9000 rpm. No damage I was aware of.

#36 John Woods

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Posted Sep 02 2015 - 10:47 AM

Posted Image


This is a graph illustrating what is meant by "marginal returns." Often referred to as "diminishing returns" or "maginal utility."
(Its from economicconcepts.com).

A marginal return is apparent in the change in output between any two points along the line topping out at point C.
Easy to notice this coincides very nicely with a torque and horsepower graphs in Set Manager and Race Engineer.
There are lots of ways to apply marginal returns analysis to motorsport.

Validity of the marginal returns graph is proven by direct evidence of the torque and horsepower curves for an engine.

An easy way to think of it is if fuel or throttle is the variable factor, (or input).
Unit of fuel equals horsepower, torque, speed, (whatever).

The chart is divided into three stages.
Stage I yields the most output for a given unit of input.
   So speed is increased the most per unit of fuel input during this stage.
Stage II continues to yield more output than input, but the amount of gain is less for each unit of input added.
   So the car is still accelerating, up to maximum cumulative marginal returns at point C.

However, easy to see the rate of acceleration slows a bunch during Stage II, so maybe best to get back into the next gear's Stage I condition as quickly as possible, maybe somewhere a little past point B? But don't get back too far, maybe just down a bit before point A?

:)

Thus my earlier posts about shifting into the next gear's bottom of 90 percent output lines.

Edited by John Woods, Sep 02 2015 - 11:05 AM.


#37 Pete Gaimari

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Posted Sep 02 2015 - 12:12 PM

Bottom line is in drag racing shifting it done at redline. It gives the fastest acceleration. It's no different in road racing.

#38 John Woods

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Posted Sep 02 2015 - 07:51 PM

Just wondering what is the definition of "redline."
Typical definitive keywords found: "set RPM," "recommended," "safe."
It refers to the maximum appropriate RPM the engine is capable of running continuously under load without blowing up.

It refers to some point well before catastrophic disaster...not an engineering/theoretical maximum ideal output like Point C at the top of a curve.
This isn't economics...its real racing and the car that first finishes wins.

Redline refers to a point before C, as determined by an engineer using mechanics, physics, machine science, and math to lock in the exact safe RPM that if set as the redline, with a given set of gears, would yield an appropriate rate of acceleration and run as close to flat out as necessary for the duration of a single race.

Redline is what an expert says it is. But we have ShiftR!
And we are, of necessity, our own experts.

Not really happy with definitions like "safe" and "recommended" decided to make an interpretation of a racer's redline, (GPL Lotus49 diagram below).

Attached Files


Edited by John Woods, Sep 02 2015 - 08:07 PM.


#39 Pete Gaimari

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Posted Sep 02 2015 - 07:56 PM

You know the Lotus 49 had a rev limiter? Safe to say it's redline.

#40 colepole

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Posted Sep 02 2015 - 08:55 PM

As far as I am aware the limiters in use in those days reacted quite slowly, so, on a smooth track you can redline it ........ what kills the engine is sudden changes in rpm e.g going over jumps/bumps while flat on the gas. Holding a gear longer than you really want to is fine for short periods ....... just have to make sure the overall oil/water engine temps don't rise above safe limits.

#41 Pete Gaimari

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Posted Sep 02 2015 - 10:02 PM

I agree. Another way to kill it is downshifting too early. That will force it way past an rpm you could get under power.

#42 John Woods

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Posted Sep 03 2015 - 07:24 AM

Seems the Lotus limiter trips around 9400rpm?

Been criticised in the past for speedshifting there.

#43 Pete Gaimari

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Posted Sep 03 2015 - 08:04 AM

There is no limiter in GPL. I was talking about the real car John. Papy has set the limit at 9000rpm in GPL. Past that will blow in time. I believe each over-rev causes some damage, and when enough has been built up it blows.

As I said already. At the end of a race if the red needle is on 9000rpm. You did good. Anything past it you screwed up. Watch what papy has in mind by looking at where the AI shift everytime. They never short shift, or go past 9000rpm. They also never ever downshift too early. If anything they downshift very late, and don't use the engine for braking.

As cole said. Holding it at 9000rpm too long will blow it too. Gear the car so it hits 9000rpm at the very end of the longest straight. Gearing too low will hold top rpm too long. You can also hold it too long in the lower gears by hold a gear too long to get to the next turn. Choose your gearing so that doesn't happen.

Another way to blow is to have it geared for the longest straight by yourself to reach 9000rpm at the end of the straight, and then in the race you draft someone, and go past 9000rpm. better to be geared a bit higher in the race, so you can draft.

Proper gearing is critical in the Lotus. Along with common sense in rpm control.

Edited by Pete Gaimari, Sep 03 2015 - 08:10 AM.


#44 John Woods

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Posted Sep 03 2015 - 08:23 AM

"he won by pushing it to the limits of common sense."

:)

Edited by John Woods, Sep 03 2015 - 05:07 PM.


#45 John Woods

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Posted Mar 03 2018 - 10:01 AM

Another little bump...

Mr. Fangio commenting on the proper shift point.
(found in Fangio A Pirelli Album by Sterling Moss, c1991 Pavillion Books).

"Whenever I was given a fresh car I would ask the mechanics, where is the maximum torque in the engine, at what revs? Then I would drive precisely to those revs and change up around that point to have the engine's maximum torque working constantly. There was no point in revving higher towards the red line; the power would only fall away and you would be risking the life of the engine."



:D

Edited by John Woods, Mar 03 2018 - 10:04 AM.





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