Renault Power Unit Hardware & Software

[bobobaba]

According to Taffin, no not yet.

I was just reading an interview with Cyril Abiteboullal on a hungarian f1 site and there was hint(ok, not fact) about that.It was made on Hungaroring.
I have made a translation of that part:
"Secondly - although I do not want to go to details, many people guess about that - but there was a concrete, a technical innovation/solution in the combustion chamber which cause a huge effect on the performance (he must have been hinting about prechamber combustion system-reporter notes) and we totally missed that solution. When we learned it we knew we would make a big leap.
But I go further: the missing of this solutions pressed us to compensate on the other parts of PU. Now we also use this solution and I'm sure we'll not just catch Mercedes but outpace them by our further development .
original article:
http://www.gphirek.hu/f1/20160808-2017- ... kevel.html

[ringo]

I think the other changes to be made, were managing more heat produced by the new combustion technology.

[gruntguru]

If power increases, total rejected heat must reduce. Only way the cooling system would see more heat would be a (larger) reduction in exhaust heat (which also reduces turbine power).

[PlatinumZealot]

Hmm. Could be the higher peak pressures.. And now that a prechamber is up in the head they may not have the necessary thermal design around it. Just talking minor details here. Like keeping the new "torch" mechanism in the right temrature range.

I feel merceds is holding back a big stack of their cards waiting for the competition to step up. There is no guarnatee that mercedes will remain the most powerful next year.

[FPV GTHO]

I think the other changes to be made, were managing more heat produced by the new combustion technology.

They were already managing more heat having a hot side compressor compared to Mercedes

[FPV GTHO]

If power increases, total rejected heat must reduce. Only way the cooling system would see more heat would be a (larger) reduction in exhaust heat (which also reduces turbine power).

That only works if they're not taking any more energy from the fuel

[godlameroso]

This is a little related to the discussion.

http://www.innovatemotorsports.com/resources/myths.php

Particularly this:
"Typically all the mixture is burned before about 70 deg ATDC. But because the mixture density and AFR in the engine change all the time, the fire has to be ignited just at the right time to get the peak pressure at the optimal point. As the engine speed increases, you need to ignite the mixture in the combustion chamber earlier because there is less time between spark and optimum peak pressure angle. If the mixture density is changed due to for example boost or higher compression ratio, the spark has to be ignited later to hit the same optimal point."

If the mixture is ignited too early, the piston is still moving up towards TDC as the pressure from the burning mixture builds. This has several effects:

The pressure buildup before TDC tries to turn the engine backward, costing power.
The point where the pressure in the cylinder peaks is much closer to TDC, with the result of less mechanical leverage on the crankshaft (less power) and also causes MUCH higher pressure peaks and temperatures, leading to knock.

[gruntguru]

If power increases, total rejected heat must reduce. Only way the cooling system would see more heat would be a (larger) reduction in exhaust heat (which also reduces turbine power).

That only works if they're not taking any more energy from the fuel

Well if power increases - they are taking more energy from the fuel.

Or did you mean "if they're not releasing more heat from the fuel"? It is safe to assume that all the teams are releasing a similar amount of heat from their 100 kg of fuel. At the super-lean mixtures being used, there is very little dissociation - over 99% of the fuel is completely combusted.

All of that heat must show up in one of three places:
1. Useful power - either to the transmission or to the batteries.
2. Exhaust enthalpy - waste heat in the tailpipe.
3. Waste heat rejected - mostly from the coolers, plus some heat loss directly from hot surfaces of the engine, electrics, hot piping etc.

Hence, if the power is increased, the total of the other two must decrease.

[gruntguru]

The point where the pressure in the cylinder peaks is much closer to TDC, with the result of less mechanical leverage on the crankshaft (less power) and also causes MUCH higher pressure peaks and temperatures, leading to knock.

The ideal is for all combustion to occur at TDC. (Mechanical leverage doesn't come into it.) TJI offers very rapid combustion which allows this ideal to be approached.

[godlameroso]

You mean asymptotically after TDC, producing power exactly at TDC is counter productive, precisely because of mechanical leverage, or rather lack of it. At perfect TDC the rod is balanced perpendicular to the crankshaft, for that split instant any power delivered is inefficient.

I understand your point though, the faster the combustion the later the ignition timing needed, to time it perfectly. I wonder if the faster combustion also means a shorter window for error(ignition mistiming)? Because whereas in a normal engine the combustion process may last nearly 150 degrees at peak rpm, in these engines even with over double the rpm the combustion process must be somewhere in the range of 120 degrees of cylinder rotation max. I still can't figure out for the life of me why you'd need 5 sparks per engine cycle like the rules allow though.

[gruntguru]

You mean asymptotically after TDC, producing power exactly at TDC is counter productive, precisely because of mechanical leverage, or rather lack of it. At perfect TDC the rod is balanced perpendicular to the crankshaft, for that split instant any power delivered is inefficient.

We are not talking about "delivering power" at TDC. The most efficient point for heat-release/pressure-rise is at TDC (as in the ideal Otto cycle. Once the piston starts to descend the gas pressure is expanded, doing work on the piston.

I understand your point though, the faster the combustion the later the ignition timing needed, to time it perfectly. I wonder if the faster combustion also means a shorter window for error(ignition mistiming)? Because whereas in a normal engine the combustion process may last nearly 150 degrees at peak rpm, in these engines even with over double the rpm the combustion process must be somewhere in the range of 120 degrees of cylinder rotation max.

Yes, the faster the combustion, the more sensitive to ignition timing.

The combustion process is much quicker than 120*. The major portion of combustion (10% - 90% Mass Fraction Burned) typically takes less than 20* and I suspect that the current F1 PU's are much faster than that.
https://trackdaytuners.com/tuner-centra ... -and-knock

I still can't figure out for the life of me why you'd need 5 sparks per engine cycle like the rules allow though.

Probably no benefit in TJI equipped engines. With conventional ignition and a lot of chamber swirl or tumble it is possible for the kernel of burning mix to move away from the spark plug, opening the possibility for a fresh flame to be started with a second spark and so on. Result = multiple flame-fronts (a poor man's version of multiple spark plugs or TJI).

[godlameroso]

I apologize, I was under the impression that as engine speed increased the combustion process would inevitably occupy more and more crank angle. Given that combustion speed does not increase at the same rate that engine RPM does. I understand that faster engine speeds promote more scavenging and mixture turbulence aiding combustion rate, but is this really enough to maintain combustion to ~ 30 degrees of crank angle at 12,000 rpm?

[gruntguru]

Not sure - but probably.

You can bet that all the design parameters including combustion rate/pressure rise rate are targeted to the engine's prime operating region ie 10k - 12k.

[r101]

Just read at gpupdate.net that Renault will base 2017 chassis on 2015 one. This (at least I think so) is a hint at Renault using split turbo for 2017. They have first hand data of Mercedes PU layout from that year.

[ME4ME]

Just read at gpupdate.net that Renault will base 2017 chassis on 2015 one. This (at least I think so) is a hint at Renault using split turbo for 2017. They have first hand data of Mercedes PU layout from that year.

I think you're reading too much into it. They just mean that there has been very little development going into 2016, which means the most recent chassi they designed is from 2015.