How are burnt pistons avoided at lean AFR seen in F1 hybrid engines??

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
Mercenthusiast
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Re: How are burnt pistons avoided at lean AFR seen in F1 hybrid engines??

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My best guess is they don't need those exotic high temp alloys.

Most probably they run rich mixtures in the tji pre chambers which seems to be sized to contain and localise any detonation. Rich mixtures burn readily at the optimum temp and the ultra lean mixtures in the main chamber benefit from the high speed of violent ignition. The Mahle literature suggests that the mixture is ignited as soon as it is injected in the prechamber. It's almost spark assisted diesel. Any soot and co generated will be burned off in the main ignition event. It's only 3% of the injected fuel anyway.

I think this can be done as a retrofit in existing engines. Even an aircooled vw type 1 can work.

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Re: How are burnt pistons avoided at lean AFR seen in F1 hybrid engines??

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J.A.W. wrote:
Fri Apr 28, 2017 11:30 am
gruntguru wrote:
Fri Apr 28, 2017 5:08 am
Judging from reports on boost pressure (anywhere from 3 to 5 bar abs) it would appear that full power lambda ratios are in fact greater than 1.6. Further evidence to suggest this can be found in TJI papers which show peak ITE at around 2.0. (At 2.0 these would be the lowest NOx producing F1 engines of all time with less than 0.05 g/kwh).
What about HC emissions though.. burning through ~20-1 fuel-to-lubricant ratio would never cut it..
That's no better ( likely worse) than 2T G.P. bike lube-oil consumption, & they were banned for it..

Curiously, HC & NOx emissions are often paired in reg's tests,
& current 2T Evinrude DI engines better 4T rivals in NOx & match them in HC..
Interestingly enough one of the things Mercedes talk about with their forthcoming F1 based hypercar is that the AFR has to come back down under a lambda of 1.0 for a streetcar is to meet emissions. I wonder how much they are changing on the oil consumption side... if anything ;-)

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Re: How are burnt pistons avoided at lean AFR seen in F1 hybrid engines??

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Mercenthusiast wrote:
Tue May 30, 2017 9:03 am
The Mahle literature suggests that the mixture is ignited as soon as it is injected in the prechamber. It's almost spark assisted diesel.
I have read most of the Mahle literature and haven't seen that. My impression is that the pre-chamber contents ignite when the spark plug is fired.

Can you provide a reference for auto-ignition in the pre-chamber?
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Mercenthusiast
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Re: How are burnt pistons avoided at lean AFR seen in F1 hybrid engines??

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gruntguru wrote:
Wed May 31, 2017 7:31 am
Mercenthusiast wrote:
Tue May 30, 2017 9:03 am
The Mahle literature suggests that the mixture is ignited as soon as it is injected in the prechamber. It's almost spark assisted diesel.
I have read most of the Mahle literature and haven't seen that. My impression is that the pre-chamber contents ignite when the spark plug is fired.

Can you provide a reference for auto-ignition in the pre-chamber?
Auto ignition was just my speculation. That's why I said it is almost diesel. Imagine you have a hot engine, high boost, and a rich mixture. The main charge is so lean it will not detonate even at high temps. But a rich mixture would.

Maybe that's why they ignite the charge immediately after injection. The evaporating fuel cools down the prechamber so maybe that prevents detonation. But even if it does detonate the prechamber might be strong enough to contain it.

On the other hand this is just a refinement of the Honda Cvcc design. Stratified charge with direct injection is hard. Tji is so much simpler. It's almost elegant in achieving non homogenous mixture combustion.

Cvcc by Honda managed to pass emissions at that time without a catalyst. Maybe this technology can do the same at current emissions standards?