Turbocharged Hybrids

[Isaac Zachary]

My ol NA diesel also had "instant torque." since there was no throttle lag nor any need to wait for the turbo to spool up either. I had all 37hp right there at my foot.

[redpoint5]

My buddy had something like 2 NA Jetta diesels and 3 engines. Don't know if he was blowing them up, or if they just blow up. Wouldn't be surprised if they like to blow up since you have to run them WOT everywhere just to almost keep up with normal driving...

I suppose adding a turbo doesn't alleviate the wear of otherwise having to run WOT all the time.

Still, those old Jettas were the worst vehicles he's owned.

[Isaac Zachary]

My ol Golf NA diesel still runs. I'm actually tempted to go pick it up since the person I sold it too never put it in his name.

The torque curve is kind of weird. It is pretty high at low RPMs and drops off considerably as it spins up. A lot of times I would downshift to find I still had the exact same of acceleration (or lack there of). The car also pours out more smoke at higher RPMs. So I tended to just floor it at low RPMs.

That car is immortal. After some 300,000 miles the odometer stopped working. I drove it for 7 years some time after that happened. So who knows how many miles it has, and it still runs great. The main killer of these engines is not changing the timing belt regularly. WOT doesn't affect much of anything except the air quality. (Wait! Diesels don't have a throttle to open.)

[redpoint5]

What do you call it? It's not a gas pedal because it burns oil. Oil pedal?

... and what people think is a gas pedal is the throttle which determines how much air the engine ingests, and in response, how much fuel to add.

... and what people think is the throttle these days is a pedal position sensor where the driver can suggest to the computer what power level they intend, and the computer decides both throttle opening and quantity of fuel to add.

I was giving quite a few moments of "full throttle" yesterday driving in the snow with my daughter, and the traction control overrode my suggestion and inserted its own.

[rmay635703]

Originally Posted by Isaac Zachary

My ol NA diesel also had "instant torque." since there was no throttle lag nor any need to wait for the turbo to spool up either. I had all 37hp right there at my foot.

I miss my ol rusted out 1982 diesel suburban 5mt with 438,000 miles

Could flirt with 30mpg at low highway speeds.

And 37-65hp is all you need for a PHEV so long as you can engage the 400+ HP Hybrid, so long as you can turn the engine on in hold mode with a full battery at the start of a trip you won’t even notice the 37hp

Worth noting a 37hp diesel generator is VERY diffierent than a 37hp gas generator , you can actually achieve the rated output continuously without lag.

[Should be biking]

This keeps coming up that a series hybrid will get amazing mileage.
If you're going to use an engine to keep a battery topped up then it just ends up being an inefficient electric car and get the same or worse mileage than a parallel hybrid or even a small engined conventional drivetrain because of the additional conversion losses of converting fuel energy to electricity, storing it in a battery and then using that to drive an electric motor instead of having the engine drive the wheels directly. And unless you have a large battery and start every trip with a fully charged battery you could end up with an empty battery (for example spirited driving around town and then start heading into the mountains). Then you'd only have a fraction of that 37hp engine's output available at the wheels because of the conversion efficiencies in that complex drivetrain.

Take the 2017 eGolf, an engine with an optimistic 50% efficiency and a 90% efficient generator.
City energy usage is 126mpge or 26.75kWh/100 mile.

City energy usage. 267.5 Wh/mile
Generator to battery efficiency 0.9 none
Engine output power required 297.2 Wh/mile
Engine thermal efficiency 0.5 none
Engine input power 594.4 Wh/mile
Fuel energy 33560 Wh/gallon
Mileage 56.46 mile/gallon

[redpoint5]

50 MPG is pretty darned good.

I feel like a 50 hp diesel series hybrid vehicle might be pretty efficient. Have some battery voltage threshold where the generator kicks on and brings state of charge up to the point where there will always be enough juice to get up a mountain pass.

[Isaac Zachary]

Hey! My 37hp car was not a hybrid! I also got good fuel mileage. I once drove an at-least 588 mile trip (according to Google Maps) and then barely could squeeze 10 gallons into the tank!

(Or whatever the horsepower it was if you take the 54hp rated horsepower and subtract whatever power you'd lose from both 8,000 - 12,000ft operation and after 30 years or several hundred miles of engine wear.)

[Should be biking]

50mpg from a 50% efficient engine is disappointing.
I don't know exactly what the conversion losses add up to when going from engine to generator to battery to electric motor, but that's got to be at least 10% more than a manual or automatic transmission connected directly to an engine.
If you always want to have enough power to drive up a long hill, the battery charging threshold would have to be pretty high, so you'd spend most of your time with the engine running and keeping the battery topped up. And at that point your mileage would be worse than a conventional drivetrain because of the conversion losses.

[redpoint5]

Originally Posted by Should be biking

50mpg from a 50% efficient engine is disappointing.
I don't know exactly what the conversion losses add up to when going from engine to generator to battery to electric motor, but that's got to be at least 10% more than a manual or automatic transmission connected directly to an engine.
If you always want to have enough power to drive up a long hill, the battery charging threshold would have to be pretty high, so you'd spend most of your time with the engine running and keeping the battery topped up. And at that point your mileage would be worse than a conventional drivetrain because of the conversion losses.

50 MPG is never disappointing.

Of course it's more efficient to use the engine directly to propel the car, but 50 HP isn't enough for acceleration and ascending hills, which is why for the sake of simplicity and reliability you'd have a series hybrid.

Lets say the generator is contributing 50 HP towards ascending a hill, the battery might only need to supply another 50 HP. You could do that for 20 minutes and only consume about 12 kWh of capacity. If the car had a 60 kWh battery, you could set the lower threshold for 35% when the generator kicks on.

You'd normally get about 165 miles of EV range before the generator kicked on.

It would be simple to allow an override to allow the battery to discharge deeper before running the generator if you knew you'd reach the destination before running out of juice.

Just as simple to allow one to manually start the generator if you know you'll need the extra juice for something.

There's just about no practical situation where 50 HP and a 60 kWh battery wouldn't be more than sufficient, and quite easy to program in limits that reduce speed for the extremely rare times it isn't.

I used WAG figures for the generator and battery, but I bet that is very conservative. One could probably get away with a 40 kWh battery and 40 HP generator and make a fantastic car.