Honda Power Unit Hardware & Software

[gruntguru]

Best way to unload a compressor at low flow conditions is to throttle upstream. Volumetric flow remains to the right of the surge line but mass flow (and work) is limited by the low air density in the compressor.

[ian_s]

but isnt that against the rules?

[Vortex37]

The current engine rules are freely downloadable from here. If you can read anywhere in the rules that Waste-Gates, BOVs, recirculation etc are banned, then please post, because I missed it.

Why is surge relevant in this PU? Can anybody seriously suggest that the compressor is over-sized through design error? I get the feeling that people are not thinking of this PU as a complete system (ff), with multiple open and closed control loops. Renault have publicly stated on their web-site, that they specifically use the MGU-H/Turbocharger combination, as a ICE control element.

[gruntguru]

Surge is always a factor, when a downstream throttle is present.

[PlatinumZealot]

They probably try to prevent the situation then?

Engine maps with spark and injector cut out when off throttle? MGU-H activated etc?

As in off-throttle is more like a zero or negative torque demand more than actual closing of throttle.

[Tommy Cookers]

They probably try to prevent the situation then?
Engine maps with spark and injector cut out when off throttle? MGU-H activated etc?
As in off-throttle is more like a zero or negative torque demand more than actual closing of throttle.

off-throttle (really, off-accelerator) there is traditionally available a negative torque equivalent here to about 15% of max ICE torque
so-called (natural) engine braking (ie the engine's frictional and pumping losses)

recovery rate via gu-k action is rule-limited (to a level equivalent to about 25% of of max ICE torque)
making at most circuits total recovery via gu-k action under braking much less than permitted (for stored energy use/lap)
so extending gu-k activity is highly desirable, this may increase the use of trail braking

and gu-k action is permitted even brake-off at zero accelerator provided net PU torque is no more than zero
(the 'zero overrun torque' rule, as used in NA F1 to increase the energy from so-called KERS)

all natural engine braking can be cancelled by this controlled ICE running in this case or in maximal braking or trail braking
yes this costs fuel, but it's a racetime-efficient use of that fuel
(and fuel-off only the pumping part of neb is cancellable by throttle plate opening)

imo we can be sure the throttle plate is not usually being 'fully' closed accelerator-off
the mgu-h ability to spool-up and spool-down has many uses

[irsq4]

Best way to unload a compressor at low flow conditions is to throttle upstream. Volumetric flow remains to the right of the surge line but mass flow (and work) is limited by the low air density in the compressor.

Did you mean you install throttle at suction side on compressor like BMW F1 4cyl. in 1980ies?

[gruntguru]

Yes.

A blowoff valve will avoid running into surge but the compressor will still be consuming a lot of power.

Upstream throttling OTOH avoids surge and minimises the power. It is so effective in fact, that snapping an upstream throttle closed from full power can unload the compressor suddenly and cause the turbo to overspeed. Not likely to be a problem with an MGUK available to capture any surplus energy.

[RicME85]

Alonso was quoted on Sky F1 that the weird sounds the Honda has made since testing is deliberate and not down to things not running properly

[Vortex37]

Recovery rate via gu-k action is rule-limited (to a level equivalent to about 25% of of max ICE torque),
making at most circuits total recovery via gu-k action under braking much less than permitted (for stored energy use/lap).
So extending gu-k activity is highly desirable, this may increase the use of trail braking.

and gu-k action is permitted even brake-off at zero accelerator provided net PU torque is no more than zero
(the 'zero overrun torque' rule, as used in NA F1 to increase the energy from so-called KERS)

all natural engine braking can be cancelled by this controlled ICE running in this case or in maximal braking or trail braking
yes this costs fuel, but it's a racetime-efficient use of that fuel
(and fuel-off only the pumping part of neb is cancellable by throttle plate opening)

imo we can be sure the throttle plate is not usually being 'fully' closed accelerator-off
the mgu-h ability to spool-up and spool-down has many uses

Hi,

Which rule number are you referring to, regarding the bit in red?

Regarding the green highlighted section, This article from AMuS might be of interest. The use of K as a gen whilst accelerating from a corner was mentioned by Renault. Of course you have to accept what they say is correct?

Regarding the blue highlighted section. You might question whether there is even a throttle plate fitted. More like individual butterflys or other types, for greater control when cylinder cutting.

[Vortex37]

Alonso was quoted on Sky F1 that the weird sounds the Honda has made since testing is deliberate and not down to things not running properly

It might be just an acoustic anomaly. But all the various sound clips posted here and other places, sounds to me and others, as if the whole MGU-H combo is running at constant high speed over the whole lap. Anybody have a clip that refutes that observation?

[Tommy Cookers]

@ Vortex37
regarding the limit on gu-k power ....
I don't know the rule number but there was much excitement on this site when it emerged about 2 years ago
in limiting the gu-k to a nominal 120 kW (and via a torque cap such that at low rpm the power is less than 120 kW) ....
there was agreement here that at many races gu-k action during the main braking phases alone would not use all the storage quota
and there was a view that, in principle, gu-k recovery power should be unlimited to encourage energy recovery

thanks for the link to gu-k action 'accelerator-on' .....
mgu-k action giving the PU torque/rpm characteristic better than the ICE's alone will involve ICE briefly driving gu-k action
and when driver demand is less than WOT-equivalent, ICE power driving the gu-k is beneficial by raising thermodynamic efficiency

speaking of throttle plate I'm meaning throttling device(s)/accelerator pedal relationship is always determined by multiple 2d maps

note to self - neb is about 15% of max torque at nominal WOT, but throttling and turbo rpm etc have big effects

re gg 's point - most aircraft engines were substantially throttled (upstream of the supercharger) at max power eg takeoff and climb

[Andres125sx]

http://www.marca.com/2015/07/07/motor/f ... 55911.html

For those who don´t want to translate, they say Honda have planned to use more tokens for Budapest. New combustion chamber, valves managment, and TC modifications.

[maguetox]

http://www.marca.com/2015/07/07/motor/f ... 55911.html

For those who don´t want to translate, they say Honda have planned to use more tokens for Budapest. New combustion chamber, valves managment, and TC modifications.

I hope they don't do it. I prefer they hold the upgrades and introduce them at Spa so Honda can have 4 more weeks of testing and find more of the unexpect failures that are the common declarations of Arai every time that something broke down.

[Andres125sx]

http://www.marca.com/2015/07/07/motor/f ... 55911.html

For those who don´t want to translate, they say Honda have planned to use more tokens for Budapest. New combustion chamber, valves managment, and TC modifications.

I hope they don't do it. I prefer they hold the upgrades and introduce them at Spa so Honda can have 4 more weeks of testing and find more of the unexpect failures that are the common declarations of Arai every time that something broke down.

Maybe it´s the other way around. They´ve done a lot of dyno tests, but we all have seen how useless that can be without real world testing into the car with g-forces, bumps, etc, so maybe they want to test it first on a track where PU is not so important before going to Spa, just in case they need to do some mod.

Some unexpected problem that may force them to detune the new PU will be less critical in Budapest than in Spa, so they can go to Spa with more confidence on the new PU