Renault Power Unit Hardware & Software

[hurril]

Oh that - I get it now. Thank you!

[Blackout]

We can also assume that the Renault PU has simply reached its limits because of its current architecture and the current fuel flow regulations... Hence the increase in reliability problems despite the stagnant performances ... That means the engine hardly accepts the new updates and has already reached it's maximum efficiency.

That's why Renault should/and might be planning to follow the others in order to push the boundaries of the PU: they should rethink the engine's architecture; to lower the charge air temps and decease turbo lag in order to increase the boost pressure without the risk of knocking (which is/was of Renault's problems) and save more electrical energy. That will allow them to increase the ICE output and the ERS output.
More overall PU power and more efficiency.
Not to mention the benefits that a more compact architecture like the Merc or the Ferrari brings on the chassis itself.

To do so, you need more resources and/or a full cooperation with your chassis team ... Two things Renault lacked in 2014 and 2015...

[Abarth]

This short time strategy of driving the compressor electrically while not building up backpressure is very interesting. Thanks for posting this informations.
I heard that Renault last year didn't want to run a Wastegate, but dump MGU-H energy into a resitor if needed (when the ES was already full and charge pressure had to be limited). So that would obviously not be compatible with such a mode of driving the turbo.

What I don't buy for a second are the huge HP deficit numbers which are stated. Or the huge gains some may have achieved. They are even high if halved.
A lot of performamce comes from the control system calibration and strategy, and not fron sheer HP numbers anyway.

[toraabe]

Why dump the electricity from the MGU-H into a resistor instead of powering the MGU-K.

[Abarth]

Why dump the electricity from the MGU-H into a resistor instead of powering the MGU-K.

Transient situations, so has it been explained, unfortunately I do not recall who it was, but this Person had some insight. Maybe I find the link...

[Abarth]

I found that bit, as I had the very same question:

Re the H to K transfer.
There are times when you can't (or wouldn't want to) transfer power from the H to the K but still need to limit turbo speed.

Think along the lines of a short burst of accel then slight decel then accel (such as feathering throttle for traction or in a switch back). The last thing the driver would want is for the K to feed power into driveline.

During those transitional situations Renault wanted to control the speed of the turbo by using the H to maintain shaft speed at or close to max rpm. It turned out (partly because of the driveability issues) that H was dumping to the heatsink far more than had been predicted or modeled. This was causing severe heat related issues in some cars at Jerez and the Renault 'patch' was to disable the H entirely and rely on the mechanical wastegate for the remainder of the test.

Obviously this resulted in dramatically increased lag and reduced performance but allowed some mileage to be put on the ICE.

In the interests of transparency it should be disclsclosed that we have had no first hand experience with the original spec PU used in Jerez.

Our running experience started with a version that had basic H functioning and limited K output.

Here the link:
http://forums.autosport.com/topic/19176 ... ?p=6596463

[gandharva]

No quick fix for Renault piston fault

Cyril Abiteboul is quoted as saying there can be "no solution within the next six weeks".

http://www.auto123.com/en/racing-news/f ... tid=176231

[djos]

Somehow i doubt RedBull can be held responsible for that Renault cock up!

[Wayne DR]

Why dump the electricity from the MGU-H into a resistor instead of powering the MGU-K.

I agree 100%!

The charging capability from the MGUH in the Technical Regulations is unlimited, so unless the battery is full, I don't see why you would be powering a resistor to waste electrical power. Open the waste gate, and dump some pressure, rather than heating up inside the car!

The Technical Regulations limit harvesting from the MGUK to 2MJ/lap, and allow 4MJ/lap discharge to the MGUK. The 2MJ plus shortfall per lap should be made up by the MGUH (EVERY LAP), so the Energy Store is always as full as possible.

Also at 4MJ/lap and 120kW as prescribed in the Technical Regulations, the theoretical duration of the electrical boost is limited to 30 odd seconds. This is in excess of the constant (unlimited) power that can be supplied from the MGUH to the MGUK (60-80kW peak estimated under a Brayton Cycle model at 3.4 Bar - Sustainable operating mode). So Renault are theoretically missing out on as much as 60 and 90 seconds of full MGUK boost (120kW) per lap...

I think they need to ditch the resistor and rethink their MGU Controller and waste gate operating strategies.

[gruntguru]

I think Renault tried to run without a wastegate - using the load bank for the rare ocaision when the turbine was making power that couldn't be sent to the ES (battery full) or the MGUK (Driver throttle demand low). There was no suggestion that they don't have the same self-sustainig mode features as the other PU's. . . or am I missing your point?

[FW17]

That could mean that Renault are not using a 4 MJ battery Pack

The maximum size of the battery back is given by the FIA as 25 KG, which they estimated as 4MJ

Renault probably running a smaller pack or MGU-H undersized to use at all times and unable to keep turbo below the 125,000 rpm limit

[Abarth]

Why dump the electricity from the MGU-H into a resistor instead of powering the MGU-K.

I agree 100%!

The charging capability from the MGUH in the Technical Regulations is unlimited, so unless the battery is full, I don't see why you would be powering a resistor to waste electrical power. Open the waste gate, and dump some pressure, rather than heating up inside the car!

The Technical Regulations limit harvesting from the MGUK to 2MJ/lap, and allow 4MJ/lap discharge to the MGUK. The 2MJ plus shortfall per lap should be made up by the MGUH (EVERY LAP), so the Energy Store is always as full as possible.

Also at 4MJ/lap and 120kW as prescribed in the Technical Regulations, the theoretical duration of the electrical boost is limited to 30 odd seconds. This is in excess of the constant (unlimited) power that can be supplied from the MGUH to the MGUK (60-80kW peak estimated under a Brayton Cycle model at 3.4 Bar - Sustainable operating mode). So Renault are theoretically missing out on as much as 60 and 90 seconds of full MGUK boost (120kW) per lap...

I think they need to ditch the resistor and rethink their MGU Controller and waste gate operating strategies.

Please read my post 3 posts above yours....and in why Renault wanted to use a resistor. And why it didn't work out.

[bonjon1979]

That could mean that Renault are not using a 4 MJ battery Pack

The maximum size of the battery back is given by the FIA as 25 KG, which they estimated as 4MJ

Renault probably running a smaller pack or MGU-H undersized to use at all times and unable to keep turbo below the 125,000 rpm limit

I thought the battery pack had a minimum weight of 25kg to prevent a battery arms race. Could be wrong.

[wuzak]

That could mean that Renault are not using a 4 MJ battery Pack

The maximum size of the battery back is given by the FIA as 25 KG, which they estimated as 4MJ

Renault probably running a smaller pack or MGU-H undersized to use at all times and unable to keep turbo below the 125,000 rpm limit

I thought the battery pack had a minimum weight of 25kg to prevent a battery arms race. Could be wrong.

Minimum 20kg, maximum 25kg.

[Blackout]

IFAIK, only the ES parts that store energy are concerned by that weight limit. The control units, the wires etc are not accounted IMO.