Renault Power Unit Hardware & Software

[hurril]

I don't think the HCCI is for top end performance. I think a better way to picture it is a raising of the graph of power/rpm. Another way would be that they get the same amount of power from less fuel, also a bit down in the RPM-range. That leaves more fuel for full-on driving.

[R_GoWin]

I don't think the HCCI is for top end performance. I think a better way to picture it is a raising of the graph of power/rpm. Another way would be that they get the same amount of power from less fuel, also a bit down in the RPM-range. That leaves more fuel for full-on driving.

Or - less fuel on board to start the race with. Helps with lap times, especially to get to the first corner quicker and maintain lead.

I'm not entirely convinced about HCCI. But I agree with 'HCCI' not being used for top end performance - cannot see that work without running into massive ringing issues. Its plausible that some sort of compression ignition based engine modes are at the disposal of the drivers to choose from. And may not be HCCI (need more residence time to achieve fuel homogeneity), but maybe stratified charge compression ignition (SCCI).

[ReoPTy]

agree SCCI is rather beleivable !

[NL_Fer]

Part load is maybe 10% of a racing lap, with 70% full throttle and 20% braking/coasting. That 10% is maybe 6% of fuel used. Saving 30% would be like 2kg.

Focussing on the 70% full throttle power/efficiency is much more interesting. Even during part the load is to focus on charging the ES as much as possible.

[hurril]

Part load is maybe 10% of a racing lap, with 70% full throttle and 20% braking/coasting. That 10% is maybe 6% of fuel used. Saving 30% would be like 2kg.

Focussing on the 70% full throttle power/efficiency is much more interesting. Even during part the load is to focus on charging the ES as much as possible.

I didn't mention WOT specifically because I did not imply it. I'm talking about different places along the RPM/torque request-map.

[Craigy]

Part load is maybe 10% of a racing lap, with 70% full throttle and 20% braking/coasting. That 10% is maybe 6% of fuel used. Saving 30% would be like 2kg.

Focussing on the 70% full throttle power/efficiency is much more interesting. Even during part the load is to focus on charging the ES as much as possible.

That 70% number you've stated is one extreme (Montreal/Monza-type figure) of a fairly wide spectrum (in fact, the F1 website quoted 72% full throttle for Montreal in 2015 - the highest number of the year).
At the other extreme (Monaco), the full throttle percentage is much lower - about 42%; consequently a lot of the time is spent at part throttle (37%) and on the brakes (21%).

Shanghai is 56% full throttle in 2016.
The average across all the tracks in 2016 is about 18% of the lap on the brakes. The highest is Monaco at about 21%.

In 2009 Keith Collantine collated all this type of data for all the tracks that year, it'd be lovely to have a similar thing for 2015 or 2016 if anyone can find it.

In looking at this I learned that Monza 2015 had a 5.8g stop into the first chicane, dumping energy into the brakes at just under 2.8MW.
By way of comparison, at Monaco 2015 the biggest stop (after the tunnel) is 1.8MW into the brakes, 4.6g.
Upshot: There's a lot of energy to harvest in braking zones, but not much time to do it in.
Everyone will start with 120kW from the ERS-K sure, but how much could someone get out of the H, using the IC simply as an air pump driven by the transmission under braking to make the H spin?
(As it's an unlimited transfer from the H to the ES, is it possible some team might design their compressor/turbine so that under braking the drivers intentionally blip the IC up to the max revs available, in order to drive the H as hard as possible in this situation?).

[gruntguru]

If the teams are making a fuss about HCCI you can bet it is happening at full load. The overall benefits of part load HCCI would be too trivial to be getting excited about - not saying it wouldn't be worth doing, but not a game breaker.

If HCCI could only be sustained at say 50% load it could still be run on some cylinders at WOTeg 1 bank using 25kg/hr of fuel (50% of its normal allocation) and the other bank at 75 kg/hr.

2.8 MW of braking makes the 120 kW (0.12 MW) maximum harvesting rate sound very puny indeed.

[djos]

If the teams are making a fuss about HCCI you can bet it is happening at full load. The overall benefits of part load HCCI would be too trivial to be getting excited about - not saying it wouldn't be worth doing, but not a game breaker.

If HCCI could only be sustained at say 50% load it could still be run on some cylinders at WOTeg 1 bank using 25kg/hr of fuel (50% of its normal allocation) and the other bank at 75 kg/hr.

2.8 MW of braking makes the 120 kW (0.12 MW) maximum harvesting rate sound very puny indeed.

Top fuel dragster's are effectively using HCCI at full load as they've burnt away the spark plugs after about 200m.

So in theory HCCI should be possible at full throttle.

[Brian Coat]

Burning out plugs in TF is not intentional and in my experience it's not as common as implied. And the linkage to a lean gasoline/air mixture running controlled auto-ignition may be tenuous?

Successful Lean WOT HCCI has been published before, albeit at lower BMEP than F1.

Concerning the pre-chamber and the HCCI, is there any actual new information? I recall prior discussions on here some months ago.

[djos]

Burning out plugs in TF is not intentional and in my experience it's not as common as implied. And the linkage to a lean gasoline/air mixture running controlled auto-ignition may be tenuous?

It's not intentional but it is an unavoidable consequence of putting 44 amp's thru each of the spark plugs.

[wuzak]

2.8 MW of braking makes the 120 kW (0.12 MW) maximum harvesting rate sound very puny indeed.

I think to do much more they would need front wheel energy recovery too.

[Brian Coat]

Burning out plugs in TF is not intentional and in my experience it's not as common as implied. And the linkage to a lean gasoline/air mixture running controlled auto-ignition may be tenuous?

It's not intentional but it is an unavoidable consequence of putting 44 amp's thru each of the spark plugs.

Hi. At the risk of skiing too far off the F1 piste, I'll suggest two reasons it is not an unavoidable consequence.

1. the plugs are very often intact after the run.
2. the limiter which stops the cars going much over 330 mph is an electronically timed retarder built into the magneto which uses spark advance to reduce torque. Without working plugs the limiter would not operate at all and the cars might outrun the capability of the tire/tyre (ca. 340) even at 1000 ft

[wonk123]

I am not convinced by stratified charge either. I had thought it may be used to keep the turbo spooled.
My understanding of it comes from discussions with a Holden engineer about 6 years ago when they were developing it for the SIDI engine.
He explained that at low load when cruising on the highway, the throttle would go to wide open, and power would be modulated by fuel flow (much like a diesel). The fuel would be injected very late in the compression stroke, leading to compression ignition. The figures he gave me were 50:1 AFR and approximately 50mpg at 110km/h (I know bloody Australians always using metric and imperial in the same sentence).

The problem with this method, is, I seem to remember after the blown diffuser saga, it was mandated that the throttle plates had to move the same as the pedal (sorry can't remember exact rule). If this still exists it would mean this method is not feasible

[gruntguru]

5.5.3. At any given engine speed the driver torque demand map must be monotonically increasing for an increase in accelerator pedal position.

[wonk123]

5.5.3. At any given engine speed the driver torque demand map must be monotonically increasing for an increase in accelerator pedal position.

Thanks for that. So nothing in the regs to outlaw stratified charge, It doesn't matter if the torque map is adjusted by fuel or air, just that it needs to be controlled monotonically by the accelerator pedal.

In another forum, a member claims that HCCI is illegal as all combustion must be initiated by a spark plug. I feel that this would be impossible to police, as pre ignition happens all the time. As long as the plug is still fired at sometime in the ignition process.
Thoughts?