Honda Power Unit Hardware & Software

[ian_s]

any kind of variable valve timing like vtec is against the rules, so no they don't have it.

[Jrchie]

Thanks for the info

[godlameroso]

Does using the MGU-K to harvest energy affect engine vacuum? I ask because vacuum is caused by engine braking and MGU-K harvests energy by engine braking. One would guess that since there's a compressor the engine would never see as much vacuum as an atmospheric engine. To a degree the MGU-H lets you control exactly how much vacuum you want, if MGU-H and K go into harvest mode under braking you would get serious engine vacuum. Watching McLaren onboards I can't help but wonder if they're using this strategy to charge the batteries but then having systems that can't deal with the heat and power that it generates giving them issues with deploying from the MGU-K and the ES. Meaning I don't think the engine is the problem, it's how their ES and MGU-K are dealing with charging and deploying that's the issue.

[PlatinumZealot]

There is no engine vacuum as you know it. There is a slight suction for a small fraction of time when the intake valves open but because of boost pressure you will not see this in the intake manifold. No matter, engine braking will still be there once the cylinders and or crankcase have air in them.

[stevesingo]

Engine vacuum is a function of intake restriction and piston speed (engine rpm). If when I driver lifts off the throttle at any engine speed, that throttle pedal demand drives a closed throttle butterfly, you will have a vacuum.

Whether the driver demanding 0% torque induces a closed throttle situation, I don't know.

I imagine that when the driver lifts and demands 0% torque, the engine will be put in to a state of lowest negative torque and the engine braking effect will be determined by the MGU-K. On top of this, I would guess that different engine map strategies will have different MGU-K harvesting on a closed throttle.

[PlatinumZealot]

Yeah I agree at completely closed throttle there is a vacuum.

[Brian Coat]

Of course the strategy around MGU-H energy transfers during decels will also affect this.

[godlameroso]

Of course the strategy around MGU-H energy transfers during decels will also affect this.

That's what I meant when I said MGU-H can control engine vacuum. If the MGU-H loads the turbine under engine braking to prevent the compressor from providing any boost to the cylinders you could get some serious vacuum.

*edit:
Thinking about it, the turbine would create back-pressure and limit engine vacuum. So never mind.

[mrluke]

Why would you prevent the compressor from making any boost during decel? You are going to want the inlet to be pressurized to get the best response as soon as the throttle is opened. The whole point of ALS is to avoid this situation so why would F1 be trying to encourage it?

[ian_s]

you need to have a flow going through a compressor for it to work correctly, if you have the throttles fully closed then the compressor will stall, resulting in a lot more lag when you get back on the throttle. there are ways round this, you can keep the throttles open a bit and cut fuel, which is probably what they do.

[PlatinumZealot]

Or you can use a blow off valve. Not sure if teams use this though.

[Spoutnik]

They don't use.

[trinidefender]

Or you can use a blow off valve. Not sure if teams use this though.

I don't think the teams can. Isn't there a rule that stipulates that all gasses that flow through the compressor must flow through the exhaust. I'm not sure if it mentions if it has to flow through the ICE and turbine though.

[Abarth]

I think that a bypass, allowing a flow from compressor outlet to inlet, is allowed.
This, correctly dimensioned, would solve our problem, isn't it?

Audi implemented such an overrun bypass a very long time ago with their 1.8T engines, to avoid turbo rpm fall down too quickly when lifting.

[ian_s]

that would be extra weight though, whereas just cutting some cylinders (or all) and leaving the throttles open is purely down to mapping