wuzak wrote: ↑
Fri May 31, 2019 6:42 am
henry wrote: ↑
Mon May 27, 2019 3:35 pm
In total a gain of 14 metres for the lap, which at 50m/s average speed (180kph) is 0.28 seconds. Add to that time gained by running faster for the rest of the straight and it’s likely the gain is more than 0.5 seconds but probably not twice that.
henry wrote: ↑
Mon May 27, 2019 6:44 pm
hollus wrote: ↑
Mon May 27, 2019 4:20 pm
How much was KERS worth?
Using the same calculator methodology I get that with 4 1.6 second KERs events the car is 1.6m further and 6kph faster at the end of each KERs deployment. So 0.2 seconds from the extra distance but much more from the extra speed. Maybe up to a second from the extra speed putting the advantage from KERS at 1 to 1.2 seconds.
KERS, with 80hp and 400kJ, had more effect than the current ERS, with 160hp and 4,000kJ?
Look at it this way.
The current cars use ~2kg per lap in a 50 lap race.
Assuming a calorific value of 45MJ/kg for fuel and an average efficiency of 45% the amount of energy used to make speed is around 40MJ.
The battery storage is 4MJ, so 10% of the useful energy from the fuel.
Assuming a square relationship between lap speed and energy, you would get approximately 5% improvement in lap time. Or about 4s over a 90s lap, compared to not using the ERS at all.
Or about 2s starting the lap with 2MJ instead of 4MJ.
That assumes that you only use the 2MJ in the lap, where the reality is they probably use >4MJ over a lap, regardless of what they start the lap with.
I think both our calculations are flawed.
I did a bit more research and redid my calculations.
For the 2009 KERS cars the main difference was that there was a weight penalty, estimated at 35kg. When I factored that in and repeated the calculations I found that a non KERS car at the weight limit and a KERS car 35kg heavier would traverse a 1km straight in pretty much the same time. It’s possible that a KERS equipped car was potentially slower over a qualifying lap than a non KERS car.
I can recall that some teams resisted using KERS and these figures illustrate one possible reason.
My error was twofold, one I didn’t take the weight into account and two I assumed that the speed advantage gained from initial deployment, even with the weight penalty, would persist for the rest of the straight. That speed difference in my calc is about 3kph.
I also calculated the benefit of KERS if the two cars were the same weight in that case the KERS car would gain about 0.3 seconds for 4 deployments of 60kW for 1.6 seconds each at the beginning of a straight.
When I looked back at the current cars calculation I had made the assumption that all the 4MJ would be deployed in e-boost mode. It is likely some would be deployed at the end of straights allowing full KERS deployment for the whole of every straight if needed. However I still think that most of the 4MJ in the ES at the start of lap would be deployed as e-boost and this would discharge the ES at an additional 110kW for an increase of power at the road of about 20kW.
This is because if they didn’t use e-boost they would be discharging at 60kW with a further 60kW to the MGU-K from the MGU-H. Instead there is 120kW from the ES to the MGU-K and 50kW to the MGU-H to drive the compressor.
I believe the rules about energy paths mean that you can’t just add 4MJ to the energy deployed by the ICE and calculate pro-rata across the lap. It is likely that 2 or 3 MJ would already deployed by the normal ES charge and discharge paths meaning that it is not possible to deploy the whole of the 4MJ SOC to the MGU-K , probably much less than half. The rest would need to be deployed in e-boost which is much less efficient and gives quite a small benefit.
Notwithstanding the inefficiency of e-boost I suggest that the 4MJ is probably worth 0.3 seconds if deployed as four 4.5 second bursts in a qualifying lap.
I’m sorry for the complexity of my post. I blame the complexity of the rules that, IMHO, make it impossible to answer questions such as in the OP without recourse to simulations.
Fortune favours the prepared; she has no favourites and takes no sides.
Truth is confirmed by inspection and delay; falsehood by haste and uncertainty : Tacitus