Traction control and VLIM

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
Tommy Cookers
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Re: Traction control and VLIM

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J.A.W. wrote:
Mon Jan 10, 2022 12:46 am
(Honda ran a VLIM system on its F1 car, ~55 years ago*,

*~20 years earlier, Mercedes-Benz had introduced a VLIM system on its DI V12 aero-engines.
Mercedes-Benz had the first VLIM - for the 300SLR (3 litre straight 8) in 1955
there's photos of it
it's not clear if it ever raced (reliability being important in 24 hr races)

how would a VLIM work on a V12 aero engine without eg 12 inlet ports ?
the DB605 of course had 2 induction systems (ground and air) due to the extended valve timing

Tommy Cookers
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Re: Traction control and VLIM

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there's 2 ways of filling the cylinders - dynamic (stagnation) pressure and sonic 'wave' pressure effects
dynamic pressure is always present - sonic effects aren't always present

dynamic pressure rises with the square of the port air velocity
so the ports should be 'relatively' small
we might say 'British-style' - culminating in the DFV

the supposedly trend-setting GP Peugeot 1911-14 was ruined by its huge ports (sized to give laminar flow)
with a 4.5 (or 7.6?) litres it needed its 5 speed gearbox
post WW2 (and still NA) 2 litre Fiats and British Fiat copies dominated - with only 3 gears

then Fiat 'invented' supercharging - so sonic stuff became largely confined to motorcycles
Last edited by Tommy Cookers on Mon Jan 10, 2022 12:37 pm, edited 1 time in total.

AngusF1
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Re: Traction control and VLIM

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Greg makes a good point about the intake tuning's limited control amplitude.


In addition from a controllability point of view, to use something for closed loop control you want your control device to:

- Exhibit a monotonic relationship to the output variable. IE make runner longer always = increase in power, and vice-versa (or the other way around). However it's not clear this would be the case as there is some complex pulse dynamics occurring. Perhaps there might be a dip at some point which would make things very unpleasant.

- Be reasonably linear to the output variable. Again, there are complex pulse dynamics here so the linearity would be questionable.

- Have the highest bandwidth possible, or in other words be able to react as quickly as possible. In this case some device would need to actually move the inlet trumpets. The trumpets and the mechanism have some mass, so will take some time to change position - possibly on the order of 1/10th of a second? Or slower.


So with those considerations as a controls engineer I would be much more interested in dropping the spark (instantaneous) or reducing the fuel supply (quick and has fine modulation) to reduce torque for traction control.



VLIM in general though, sure, great idea for maximising torque across the rev range.

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Zynerji
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Re: Traction control and VLIM

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Thank you for all of the responses!

I was more thinking of just a "back off" point where it would see rear wheel spin, and shorten the runner until the wheel spin stopped.

I see that in low power low rpm applications that it could do some work, but there are simply better ways to get the effect.

Thank you!

AngusF1
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Re: Traction control and VLIM

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Oh yes, as a third preference I would prefer to use the throttle itself over this method as well. ;)

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henry
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Re: Traction control and VLIM

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In addition to the ICE benefits I think VLIM on these PUs can reduce the required manifold pressure for the same mass of air in the cylinder, and hence compressor work, increasing the MGU-H output.
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Hoffman900
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Re: Traction control and VLIM

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Tommy Cookers wrote:
Mon Jan 10, 2022 12:27 pm
there's 2 ways of filling the cylinders - dynamic (stagnation) pressure and sonic 'wave' pressure effects
dynamic pressure is always present - sonic effects aren't always present

dynamic pressure rises with the square of the port air velocity
so the ports should be 'relatively' small
we might say 'British-style' - culminating in the DFV

the supposedly trend-setting GP Peugeot 1911-14 was ruined by its huge ports (sized to give laminar flow)
with a 4.5 (or 7.6?) litres it needed its 5 speed gearbox
post WW2 (and still NA) 2 litre Fiats and British Fiat copies dominated - with only 3 gears

then Fiat 'invented' supercharging - so sonic stuff became largely confined to motorcycles
Can you elaborate?

In the intake port, .55-.60 Mach is typically regarded as the controlling number. This is true for forced induction engines as well, they increase density not volume.

Exhaust ports are the only places you may see sonic conditions in a port. Honda found with their Formula 1 V8 program that sonic conditions occurred at the exhaust throat on their single cylinder test engine but not in the multi-cylinder engine. The reason being there is always some pressure in a shared exhaust collector, thus delta P is lower. The response to enlarge the throat in the single cylinder engine (to manage the sonic condition) was not reflected in performance gains in the multi-cylinder engine. Realizing this, they shrunk the exhaust port throat to get velocity near sonic conditions. Considering the exhaust temp, this is pretty fast!
Last edited by Hoffman900 on Mon Jan 10, 2022 5:47 pm, edited 5 times in total.

Tommy Cookers
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Re: Traction control and VLIM

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Hoffman900 wrote:
Mon Jan 10, 2022 3:46 pm
then Fiat 'invented' supercharging - so sonic stuff became largely confined to motorcycles
Can you elaborate?
tuned length inlets (via motorcycles) took over in US cars eg dirt & board track racing during the European WW1 hiatus
eg 8 equal tuned length and trumpeted inlet tracts on straight 8 NA engines - 4 twin-choke carburetors eg Winfield
tuned lengths were eg varied by changing trumpet length

then supercharging emerged and dominated GPs in iirc 1924 (Fiat - positive displacement superchargers)
the top US racing followed European rules so went supercharged - with centrifugal superchargers

the benefits of tuned inlet lengths were discarded in cars until some time after NA engines returned
motorcycles more or less remained NA and these increased their levels of 'sonic' tuning
ex-motorcycle ace Brit 'Mr tuned-length' Freddie Dixon beat s/c dohc GP cars with his NA Riley road-car pushrod hemis
Last edited by Tommy Cookers on Mon Jan 10, 2022 5:21 pm, edited 1 time in total.

Hoffman900
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Re: Traction control and VLIM

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Tommy Cookers wrote:
Mon Jan 10, 2022 5:13 pm
Hoffman900 wrote:
Mon Jan 10, 2022 3:46 pm
then Fiat 'invented' supercharging - so sonic stuff became largely confined to motorcycles
Can you elaborate?
tuned length inlets (via motorcycles) took over in US cars eg dirt & board track racing during the European WW1 hiatus
eg 8 equal tuned length and trumpeted inlet tracts on straight 8 NA engines - 4 twin-choke carburetors eg Winfield
tuned lengths were eg varied by changing trumpet length

then supercharging emerged and dominated GPs in iirc 1924 (Fiat - positive displacement superchargers)
the top US racing followed European rules so went supercharged - with centrifugal superchargers

the benefits of tuned inlet lengths were discarded in cars until some time after NA engines returned
motorcycles more or less remained NA and these increased their levels of 'sonic' tuning
Ah, got it. I'm not super versed in the history of what was going on pre 1960s, other than a few notable exceptions. Thanks!

gruntguru
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Re: Traction control and VLIM

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Hoffman900 wrote:
Sun Jan 09, 2022 3:43 pm
Here is a 2L Cosworth BDG built by Steve Jennings (found online):
http://indycompetition.com/uploads/3/5/ ... t_orig.jpg
That power curve isn't that great to me. I'd even take a little away from peak to boost that whole curve above 6500rpm.
Looks pretty good to me. Torque is flat +/-2% from 6,300 - 8,500 rpm.

Image
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gruntguru
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Re: Traction control and VLIM

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Of course the basic premise of this thread - that VLIM can somehow reduce torque for the purposes of traction control - is shot down by the simple fact that torque can only be controlled by the driver. If torque responds to any variable other than the throttle-pedal-position and engine rpm - it is illegal. (Plus engine mode switches of course.)
je suis charlie

saviour stivala
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Re: Traction control and VLIM

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gruntguru wrote:
Tue Jan 11, 2022 8:35 am
Of course the basic premise of this thread - that VLIM can somehow reduce torque for the purposes of traction control - is shot down by the simple fact that torque can only be controlled by the driver. If torque responds to any variable other than the throttle-pedal-position and engine rpm - it is illegal. (Plus engine mode switches of course.)
Fully agree with all that.