Renault Power Unit Hardware & Software

[_cerber1]

I wonder if the exhaust manifold fire in the McLaren has something to do with the way the engine is supposed to run. Maybe they burn a little fuel in the exhaust manifold on purpose.

No, this is impossible. Engineers make every effort to burn fuel in cylinders as efficiently as possible, the TJI system is a clear example of this. If you burn fuel in the exhaust manifold, you will burn little fuel in the cylinder, and therefore lose power.

[godlameroso]

I wonder if the exhaust manifold fire in the McLaren has something to do with the way the engine is supposed to run. Maybe they burn a little fuel in the exhaust manifold on purpose.

No, this is impossible. Engineers make every effort to burn fuel in cylinders as efficiently as possible, the TJI system is a clear example of this. If you burn fuel in the exhaust manifold, you will burn little fuel in the cylinder, and therefore lose power.

What's to stop a team from injecting fuel for a normal combustion event, then again after the exhaust valve opens? Then the only thing you're doing is wasting fuel and burning it in the exhaust pipe. Not that it's a good idea to waste fuel, you probably wouldn't be able to extract anything extra from the MGU-H. It's probably better to maximize crank power because crank power can be used to charge the ES by both MGU-H and K.

[_cerber1]

What's to stop a team from injecting fuel for a normal combustion event, then again after the exhaust valve opens? Then the only thing you're doing is wasting fuel and burning it in the exhaust pipe. Not that it's a good idea to waste fuel, you probably wouldn't be able to extract anything extra from the MGU-H. It's probably better to maximize crank power because crank power can be used to charge the ES by both MGU-H and K.

You will not get high-quality combustion, since it is not the fuel itself that burns, but the fuel-air mixture, which in this case will be mixed with the exhaust gases that leave the cylinder and will not have the desired air / fuel ratio.

[etusch]

I wonder if the exhaust manifold fire in the McLaren has something to do with the way the engine is supposed to run. Maybe they burn a little fuel in the exhaust manifold on purpose.

No, this is impossible. Engineers make every effort to burn fuel in cylinders as efficiently as possible, the TJI system is a clear example of this. If you burn fuel in the exhaust manifold, you will burn little fuel in the cylinder, and therefore lose power.

What's to stop a team from injecting fuel for a normal combustion event, then again after the exhaust valve opens? Then the only thing you're doing is wasting fuel and burning it in the exhaust pipe. Not that it's a good idea to waste fuel, you probably wouldn't be able to extract anything extra from the MGU-H. It's probably better to maximize crank power because crank power can be used to charge the ES by both MGU-H and K.

Combustion efficiency drops mgu-h gain because of colder gases right? If so, it has logic to burn a bit of fuel at the exhaust. They can do it everywhere where full power is not needed. During deceleration or maybe in some cases during acceleration. They also don't need to do it with every cylinders but one of six can combust normally and next one in combustion order can combust into exhaust system. If this application keeps exhaust hotter and make mgu-h motor need less power from battery or mgu-k for it own spin to stay at desired spinning level and send more to battery or mgu-k back, a calculated amount of additional fuel is not bad especially at race pace.

[stevesingo]

Why burn fuel on the exhaust stroke in part throttle (in sub optimal conditions - poor AFR control and high surface area) to charge from MGU-H when you can burn fuel in the combustion chamber (precise AFR conditions) to make more power at the crank and charge through MGU-K?

[godlameroso]

Why burn fuel on the exhaust stroke in part throttle (in sub optimal conditions - poor AFR control and high surface area) to charge from MGU-H when you can burn fuel in the combustion chamber (precise AFR conditions) to make more power at the crank and charge through MGU-K?

I think you can control the afr in the exhaust pipe with the hardware available. You have a turbine to control backpressure, and you have an O2 sensor telling you afr ratio in the tailpipe. Plus you have ~4.5 bar of boost in an ICE that can run quite lean.

[Zynerji]

This brings me back to the idea of a pressurized intake runner. If the intake valves stay open for a few degrees after BDC, and there is a valve at the beginning of the intake runner (like a Reed valve), the intake runner itself could be pressurized at a high enough level that it would be very powerful when initially opening (during the overlap phase).

Now, the question that remains with this is it better to inject a certain amount of fuel at BDC, knowing the intake runner will be pressurized with an air/fuel mixture that will burn when opened, or is it just air that is used to "power flush" the cylinder.

[stevesingo]

Why burn fuel on the exhaust stroke in part throttle (in sub optimal conditions - poor AFR control and high surface area) to charge from MGU-H when you can burn fuel in the combustion chamber (precise AFR conditions) to make more power at the crank and charge through MGU-K?

I think you can control the afr in the exhaust pipe with the hardware available. You have a turbine to control backpressure, and you have an O2 sensor telling you afr ratio in the tailpipe. Plus you have ~4.5 bar of boost in an ICE that can run quite lean.

To the same degree as the AFR is controlled in the cylinder?

The fundamental question is, would be exhaust burning with the heat generated being harnessed through MGU-H more or less efficient than generating excess power above the driver torque demand and harnessing that power through MGU-K?

[Zynerji]

Is there an option of a synergy between the 2 GU's? Even a 101% mixed strategy would be beneficial over a 100% extreme case.

[PlatinumZealot]

Already discussed in Honda thread, there is nothing to gain by wasting fuel in the exhaust, but reducing the life of the turbocharger and exhaust piping.

[godlameroso]

Already discussed in Honda thread, there is nothing to gain by wasting fuel in the exhaust, but reducing the life of the turbocharger and exhaust piping.

Not true, it's been demonstrated in a paper I posted but was deleted, that the turbine attenuates even severe detonation without pitting or any bearing damage(experiments trump theory 100% of the time). Only the exhaust pipe suffers, but those get changed out every GP.

Also consider that output of the power unit is time averaged, it does not capture the individual discreet events that happen at all engine speeds. It depends on the speed of the control electronics and the anticipation strategies, perhaps small pressure peaks at the turbine can be harvested similar to Honda's extra harvest strategy. The difference is the anticipation, you have to be able to predict the acceleration pulses of the turbine in order to harvest them. When charging the ES via extra harvest, everything is predicted. The MGU-K harvests crank power, the CE switches the MGU-H to motor and accelerates the turbo, and instantly switches to generator at 40Hz intervals.

Question is what is the switching limit of the CE? Could it capture a 1,000Hz pressure wave accelerating the turbine?

Also consider that detonation events are going to happen whether you want them to or not while the engine is running, you can't avoid them, period, end of story. Might as well try to get something out of it instead of just melted pistons.

I understand that the difference between deflagration and detonation is the difference between a push and a slap, but it's going to happen anyway, no matter what you do. You can minimize detonation, but if you're pushing the engine for power it's going to happen, it happens with any ICE. These engines do still knock.

[PlatinumZealot]

Already discussed in Honda thread, there is nothing to gain by wasting fuel in the exhaust, but reducing the life of the turbocharger and exhaust piping.

Not true, it's been demonstrated in a paper I posted but was deleted, that the turbine attenuates even severe detonation without pitting or any bearing damage(experiments trump theory 100% of the time). Only the exhaust pipe suffers, but those get changed out every GP.

Also consider that output of the power unit is time averaged, it does not capture the individual discreet events that happen at all engine speeds. It depends on the speed of the control electronics and the anticipation strategies, perhaps small pressure peaks at the turbine can be harvested similar to Honda's extra harvest strategy. The difference is the anticipation, you have to be able to predict the acceleration pulses of the turbine in order to harvest them. When charging the ES via extra harvest, everything is predicted. The MGU-K harvests crank power, the CE switches the MGU-H to motor and accelerates the turbo, and instantly switches to generator at 40Hz intervals.

Question is what is the switching limit of the CE? Could it capture a 1,000Hz pressure wave accelerating the turbine?

Also consider that detonation events are going to happen whether you want them to or not while the engine is running, you can't avoid them, period, end of story.

I understand that the difference between deflagration and detonation is the difference between a push and a slap, but it's going to happen anyway, no matter what you do.

It will still get damaged more than normal operation.

Soot and precipitate accumulation is also a big issue.

It is not designed as combustion chamber nor a power turbine either.

You would be lucky to get 10% efficiency from that fuel to turbine shaft.

It is a neat trick in rally cars and drag racing but I don't see the purpose of it in this F1 formula.
"sneaking" energy to the MGUH is not really as it seems. You are actually losing your most precious resource your fuel, when you could simply wait a few seconds to get more efficient use of waste heat after whatever corner you just took.

[godlameroso]

If you have fuel to spare because your combustion process has rendered the fuel limit irrelevant(could easily do the average race with 90kg of fuel), you may as well try to squeeze all the water out of that stone(20kg of fuel to play with and acting as extra weight in the car). Probably even easier to do now because of the "one mode to rule them all" rule.

Even if you're using 105kg that's still 5kg of fuel to play with.

I can't remember the last time I heard a team tell the driver you're low on fuel, or you need to think about saving fuel. Do you?

https://www.sciencedirect.com/science/a ... 6113001519

"Results show that the momentum difference per unit area between the turbine inlet and outlet plays an important role in the power extraction, while the pressure peak of the detonation has little effect. The equivalence ratio of fuel and air mixture and the transition structure between PDC and turbine are also important to the power extraction of the turbine. The present work is promising as it suggests that the performance benefit of a PDC–turbine hybrid engine can be realized by increasing the momentum difference per unit area through the optimal design of transition section between the PDC and turbine."

In other words the kinetic force of the pressure wave increases turbine speed, but not the pressure peak. Not a problem in a mixed flow turbine.

[etusch]

Why burn fuel on the exhaust stroke in part throttle (in sub optimal conditions - poor AFR control and high surface area) to charge from MGU-H when you can burn fuel in the combustion chamber (precise AFR conditions) to make more power at the crank and charge through MGU-K?

If mgu-k regenerates with engine power during braking, I think it is still doable but you maybe right too. I think, if regeneration would come from Engine, we would hear a constant rpm voice (if I am not wrong, constant rpm is better for regeneration) from engine during braking. So it must be coming from reverse torque form rear wheel. If it is coming from real wheel then I don't know what is the relation with crank power produced by fuel.

[stevesingo]

Why burn fuel on the exhaust stroke in part throttle (in sub optimal conditions - poor AFR control and high surface area) to charge from MGU-H when you can burn fuel in the combustion chamber (precise AFR conditions) to make more power at the crank and charge through MGU-K?

If mgu-k regenerates with engine power during braking, I think it is still doable but you maybe right too. I think, if regeneration would come from Engine, we would hear a constant rpm voice (if I am not wrong, constant rpm is better for regeneration) from engine during braking. So it must be coming from reverse torque form rear wheel. If it is coming from real wheel then I don't know what is the relation with crank power produced by fuel.

I can't see how you would see constant rpm (if I understand your meaning) as the engine is geared to the wheels.

MGU-K regen can occur (theoretically) whenever driver torque demand is less than total torque available.