PlatinumZealot wrote: ↑
Mon Mar 02, 2020 3:59 am
Ok.. Im gonna ramble on here. Read at your own peril..
This article suggests that on braking when ICE propulsion is not needed, the igntion and fuel is disabled on four (or three?) cylinders and the throttle is opened. The working cylinders sole purpose is to drive the turbocharger.
Then the aticle states the excess compressed air is passed through the non-firing cylinders to drive the turbine (MGUH). I do not agree with this part as is. i think is redundant and not necessary. You can see the "perpetual motor/generator enegry problem here.
I do not believe the non-firing cylinders act as a "relief or pass thru" for "excess" compressed air. it is just coincidence. The throttle is opened to power only three cylinders because this poses less throttling loss, less thermydnamic loss, less fuel losses than firing all six cylinders at low throttle low load out of their designed efficiency range.
So three efficient firing cylinders power the MGUH.
Because the MGUH loads the turbine, I presume the wheel is slightly over-sized (for racing conditions especially) than one without MGUH.It is a compromise for qualifying actually. However, this is compensated for by the variable inlet guide vanes on the compressor. Anyway, in a good design the turbine wheel mass flow is balanced to the compressor wheel mass flow. There is no such thing as excess air. Each cylinder is getting the same amount of air if they are all firing. Except now the non-firing cylinders do not have a strong scavenging effect. To help this, the equal length exhaust manifold is designed to have a sort of eductor effect at the collector. The firing cylinders still consume most of the intake because of this and the non-firing cylinders consume slightly less air.
Erm. So with that ramble... The skip-firing is basically an efficient way to work the MGUH at low torque demand.
I am now going to suggest "COLD SKIP-FIRING"
and "HOT SKIP-FIRING
The burbbling or the farting noise is the "Cold skip firing" done before the " hot-skip" firing is summoned.... Yes.. This could mean its not anti-lag anymore! We dont need anti-lag with MGUH right. The cold skip is done to blow out hot carbon particles out exhaust runners of the non-firing cylinders. To prevent premature back-fire
And....then the popping noises is fuel.. from the non- firing cylinders being injected into the exhaust stream. HOT SKIP FIRING
This fuel is ignited when it meets the hot particles from the firing cylinders downstream of the collector. Combustion, pressure peak, BANG! Cheap power to the MGUH with
less associated cylinder losses.
I agree with your paragraph about skip-fire not not being about compressed air pass through. But I think we are misinterpreting or going a little sideways with skip-fire terminology.
I am pretty convinced now that driver torque demand (accelerator pedal position) is controlled via skip-fire on Honda powered cars, zero throttle/s. Varying cylinder cut-off/fired combinations can provide all sorts of torque values from 0-100%. I honestly think this is the system they've been trying to employ perfected for some time now and they've gotten there. So just for clarity, it's employed solely a torque demand function and would boost ICE efficiency greatly and again, because it would neutralise engine braking, the MGU-K would now be the sole pathway for engine braking and the potential energy available for harvest would be higher.
Your "hot skip firing" terminology is a bit odd, and although I'm understanding you, you then mention "It's not anti-lag anymore, we don't need anti-lag with the MGU-H right?"
Although this WAS probably true early on for these PU's. I think we've gotten to the point where anti-lag has become useful again.
Here's a super basic/simplified example I'm thinking of.
Say at racetrack X they are used to running with 85kg of fuel for the entire race distance and that amount/weight does not hinder the car's dynamics in comparison to the competition. What if with the introduction of an improved ICE, they can run the same distance at the same (or higher) power but only use 80-83kg (note: numbers are abitrary placeholders to prove a point).
So they now have an ICE efficient enough they can spare fuel.So you would think, "ok take that fuel out and save the couple kg's of weight"... but what if there is a second option now. What if Honda has now suggested to you, keep the fuel load as usual, we can use that left over fuel, pass it into the engine, as per regulations, and inject it into a cylinder that is not currently firing and the fuel will enter the exhaust unburnt and then detonate and create an anti-lag effect on the turbine (This would only be available to manufacturers using skip-fire in the manner Honda is)
The gain would be, they do not need to expend electrical energy from the battery on the MGU-H to keep the turbo spinning at that point in time but in fact have the MGU-H in harvest mode while dumping the fuel and it would spin the turbo for desired boost pressure but also drive the MGU-H to generate more electrical energy.
If the amount recovered is great enough to warrant keeping the extra fuel, then definitely, why not use it. Or at least have this as an engine mode that is a higher power sustained race mode where you have more electrical energy to use for a longer period of laps without over-draining the battery.
I'm sure this could use some refining but initial idea seems sound. Open to critique haha