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F1: No one is using 8th gear?


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#1 Gurra

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Posted 04 April 2014 - 07:22

In Malaysia it seemed some cars were running on the rpm limiter in 7th gear down the longest traight but I didn't see anyone changing to 8th gear?

It got me puzzled, any insights?



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#2 Ferrari_F1_fan_2001

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Posted 04 April 2014 - 08:04

You'll probably see the need for 8th gear on the long straight circuits like Monza, Spa and maybe in Bahrain this weekend. The other circuits have not had the need to use 8th gear yet.



#3 scolbourne

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Posted 06 April 2014 - 07:26

They were using 8th in Bahrain



#4 gruntguru

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Posted 06 April 2014 - 07:41

Seems odd they would be in 7th on the limiter. Shifting to 8th would offer more HP and better fuel economy.



#5 jimjimjeroo

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Posted 06 April 2014 - 09:04

youd probably find that shifting into 8th to avoid the limiter, would drop revs yes, but increase ERS usage.... which is more valuable..?

#6 Wuzak

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Posted 06 April 2014 - 12:15

youd probably find that shifting into 8th to avoid the limiter, would drop revs yes, but increase ERS usage.... which is more valuable..?

 

Why would shifting up require more ERS usage?

 

In situations where they are using 7th/8th gears they will be using the maximum ERS, or at least the amount the MGU-H can deliver to the MGU-K.

 

In the lower gear the ICE will be revving more, will have lower power, while the MGU-H is generating more power and (to my mind) delivering it to the MGU-K. But total power will be less, above 12-13k revs.



#7 Lee Nicolle

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Posted 08 April 2014 - 09:02

I suspect that the cars will actually slow down when using eighth gear, it is faster to buzz it in seventh, though I doubt that does the engine life any good.



#8 Wuzak

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Posted 08 April 2014 - 10:22

I suspect that the cars will actually slow down when using eighth gear, it is faster to buzz it in seventh, though I doubt that does the engine life any good.

 

They will have more power at 10,500-12,000rpm in 8th than at 15,000rpm in 7th. So why would they be slower?



#9 Otaku

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Posted 10 April 2014 - 09:29

They never hit the limiter yet, ever.



#10 RogerGraham

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Posted 10 April 2014 - 10:05

They will have more power at 10,500-12,000rpm in 8th than at 15,000rpm in 7th. So why would they be slower?

 

Dumb question time...  why will they have more power at lower revs?  I thought that power would be basically constant as soon as they hit the 100kg/hr fuel flow limit.  Are you referring to efficiency losses at higher revs?



#11 Greg Locock

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Posted 10 April 2014 - 12:29

That's a good way of looking at it. Does anybody have the data for a bsfc map they could post, ie actual figures, not just  a plot.Then you could see the likely shape of the drop off with rpm.



#12 Kelpiecross

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Posted 10 April 2014 - 12:35

They will have more power at 10,500-12,000rpm in 8th than at 15,000rpm in 7th. So why would they be slower?


Oh Dear - not torque/horsepower again?

#13 gruntguru

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Posted 10 April 2014 - 22:36

Dumb question time...  why will they have more power at lower revs?  I thought that power would be basically constant as soon as they hit the 100kg/hr fuel flow limit.  Are you referring to efficiency losses at higher revs?

Mechanical losses always increase with rpm. For "normal" engines, peak power occurs when airflow (the limit on "heat energy into the engine") is no longer able to increase more rapidly than the mechanical losses. For a "fixed fuel flow" engine (eg F1 from 10k - 15k) the rate of heat input is relatively fixed whereas the losses are constantly increasing from 10 - 15k.

 

Indicated thermal efficiency (the thermodynamic efficiency before mechanical losses are subtracted) also drops at high revs due to the reduced time available for combustion to occur.



#14 Greg Locock

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Posted 10 April 2014 - 23:04

But that's an argument in favour of using 8th rather than 7th



#15 Wuzak

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Posted 11 April 2014 - 05:09

Oh Dear - not torque/horsepower again?

 

No, not at all.

 

Maximum speed will occur at maximum power. Whether or not that is in 7th or 8th gear depends on the gearing and the aero package.

 

It is quite likely that 8th gear is too tall for the high downforce set-ups used at most tracks and the power is insufficient to overcome the drag. For lower downforce/drag tracks 8th will be usable and give higher top speeds.

 

That said, one or two of the teams were using 8th gear in Bahrain. 



#16 gruntguru

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Posted 11 April 2014 - 05:27

But that's an argument in favour of using 8th rather than 7th

Yep - or whatever gear puts the engine at max power rpm (10k - 12k?)



#17 Kelpiecross

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Posted 11 April 2014 - 06:19

No, not at all.
 
Maximum speed will occur at maximum power. Whether or not that is in 7th or 8th gear depends on the gearing and the aero package.
 
It is quite likely that 8th gear is too tall for the high downforce set-ups used at most tracks and the power is insufficient to overcome the drag. For lower downforce/drag tracks 8th will be usable and give higher top speeds.
 
That said, one or two of the teams were using 8th gear in Bahrain.


Speaking generally (not just F1) I am not sure that maximum speed always occurs at max power. I would imagine that max speed is at a point where available power equals the total power needed (drag/rolling resistance etc.) to travel at that speed.
Whether or not it would be an advantage to arrange an F1 car so that max speed is at max power - I don't know.

#18 MatsNorway

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Posted 11 April 2014 - 09:44

They had no choice in the past. Being so top heavy on power. But when power kicks inn lower down you gear it to get out of the corner or should i say get away from it as fast as possible. It is ofc. depending on how fast the track is and how long the straight is and so on. 

 

If you are at the limiter and gears up and jumps down to 10krpm it is a no brainer unless fuel limitations.



#19 GVera

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Posted 11 April 2014 - 10:37

Mechanical losses always increase with rpm. For "normal" engines, peak power occurs when airflow (the limit on "heat energy into the engine") is no longer able to increase more rapidly than the mechanical losses. For a "fixed fuel flow" engine (eg F1 from 10k - 15k) the rate of heat input is relatively fixed whereas the losses are constantly increasing from 10 - 15k.

 

Indicated thermal efficiency (the thermodynamic efficiency before mechanical losses are subtracted) also drops at high revs due to the reduced time available for combustion to occur.

 

I'll say that it's fixed up from the point in where you reach the limit of flow to obtain optimum mixture, it might be 10, 11 or 12k rpm, only the teams know.


Edited by GVera, 11 April 2014 - 10:38.


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#20 gruntguru

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Posted 13 April 2014 - 12:11

The engines are operated at optimum mixture regardless of the operating point. At WOT this is done by regulating airflow since fuel flow is fixed. So whether the rpm is 10, 11 or 12 k the mixture will be set for max power which also happens to be the same setting for max fuel efficiency.

EDIT. Interesting topic actually. Forget everything you knew about mixture strength and it's effect on power. It is quite probable that maximum power at some operating points is obtained with a lean mixture ie greater than 14.7:1

Edited by gruntguru, 13 April 2014 - 12:18.


#21 gruntguru

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Posted 13 April 2014 - 12:20

Speaking generally (not just F1) I am not sure that maximum speed always occurs at max power. I would imagine that max speed is at a point where available power equals the total power needed (drag/rolling resistance etc.) to travel at that speed.Whether or not it would be an advantage to arrange an F1 car so that max speed is at max power - I don't know.


Maximum speed for any car will only be obtained when the engine is producing maximum power.

Edited by gruntguru, 13 April 2014 - 12:20.


#22 Slumberer

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Posted 14 April 2014 - 14:40

Surely it's dependent upon the gearing?



#23 gruntguru

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Posted 14 April 2014 - 22:25

Yes, the gearing needs to be set so the engine is at max power rpm when the car is at max speed. Fortunately the engines have a wide rpm band where near max power is produced so gearing is not critical. In many cases near top speed may be available in either of two gears so obviously the more fuel efficient gear would be chosen.


Edited by gruntguru, 14 April 2014 - 22:28.


#24 Kelpiecross

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Posted 15 April 2014 - 10:54

Maximum speed for any car will only be obtained when the engine is producing maximum power.


I would have to agree with that statement if we are talking about the maximum ultimate speed a car is capable of. I was thinking more of normal road cars with more limited gearing options - I am not sure if they are generally arranged so that their max speed is at max power?
And presumably at a slow speed circuit like Monaco the gearing is set so that the max speed on that circuit is at max power - but presumably the same car/same gearing on a longer circuit could possibly go faster by revving the engine past its peak power point?

#25 gruntguru

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Posted 15 April 2014 - 23:26

And presumably at a slow speed circuit like Monaco the gearing is set so that the max speed on that circuit is at max power - but presumably the same car/same gearing on a longer circuit could possibly go faster by revving the engine past its peak power point?

The rules do not permit gearing changes. The 8 ratios have to be chosen at the start of the season, so teams will have chosen 7th and 8th on the basis of expected top speeds at various circuits.



#26 murpia

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Posted 16 April 2014 - 09:12

The fuel flow limit turns the engines into constant combustion power devices above 10,000rpm. Engine friction reduces crank power slightly as revs go beyond 10k.

 

So Vmax will be primarily drag dependent and can be achieved in both 7th or 8th most probably.

 

Regards, Ian



#27 gruntguru

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Posted 17 April 2014 - 02:13

Depends on the track and the aero setup (and DRS).