Cost. Considering the premium over the conventional golf to add hybrid AND tdi, it's not to hard to see why they'd nix the idea.

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Simple economics. A diesel engine that meets Tier 2 Bin 5 costs $2000 - $4000 more than a gas engine of similar power. And meeting the Tier 2 Bin 5 emissions reduces the fuel efficiency. Strong hybrids add another $4000 in cost.

You'll never make up enough in reduced fuel consumption to pay for the added cost of the drivetrain.

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Gas prices here are still lower than gas prices in Europe.

Europeans are doing just fine with the regular Golf.

Besides, the cost of a diesel hybrid would more than negate the fuel economy advantage.

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Considering that diesel prices are also along for the price hikes, it honestly doesn't make sense to pay the extra money for both the hybrid powertrain and diesel powertrain when it's not going to be any cheaper to drive than a 50mpg gas-electric hybrid. Getting 69mpg is pointless if each gallon costs an extra dollar.

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I'm sorry, that was way too logical and thought out. You shouldn't be on the internet in fact.

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If you're running at a steady-state, you can design the gas engine to run at WOT, and thus have no pumping losses. Thus it becomes as efficient as a Diesel.

This is basically what Toyota did, and it works great.

As to the torque, understand this: torque is phantom.

If you want a lot of torque, you can use gear reduction. Or if you want as much torque from a gas engine, you can give it a longer stroke, like a Diesel. This is done with big-block motors (like the 454). It does reduce HP, which means you suffer overall on performance, but if that's what you want, you can get it from a gas engine, you don't need to go to Diesel to get it.

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@LS7...

What the heck are you talking about?

running a gasoline at WOT may have no pumping losses, but it has it's drawback in energy losses as the pistons change direction twice every stroke, running at high piston speeds. Not to mention the heat, and lubrication requirements. Hardly efficient or feasible for very long.

I highly doubt the toyota hybrids run at WOT with a gasoline engine. They probably run above idle speed, but a diesel would run slower with more torque output than the gasoline engine.

A diesel makes a LOT of torque at slow engine rotation speeds. heat is more manageable and even, and lubrication is easier to manage, and burns less fuel than WOT, and timing optimization is easier to maintain.

Torque is phantom??????? This from a SBC fan?

Torque is a physical force over a distance. There is a scientific definition and measurement for it, as work in a rotational motion. Horsepower is a FUNCTION of it. Without torque over time, there IS no horsepower.

Lengthening the stroke length makes more torque in a gasoline engine, at the expense of power, and RPM range. But a gasoline engine has a much lower static compression ratio, and that can't be made up by stroke length, practically.

A gasoline engine's stroke length can only get so long, in ratio to it's bore. Otherwise the power stroke is longer than the duration of the mixture burn, and the power is spent before the piston reaches the bottom of the stroke, and the engine saps it's own energy from inertia to finish the revolution.

Gear reductions do not ADD energy, they modify energy input. Lots of force, or lots of speed, one or the other in a trade-off. Energy comes from the engine, not the gears. Changing the ratio does not magically add energy to the system.

I wasn't suggesting this to be a performance engine. CONTRARY, I am suggesting that a more rev-flexible gasoline engine is better performing, and better left alone.

I am suggesting that if there is a case for a hybrid, a diesel engine makes a better electrical generator power source. I have cited examples of other diesel electric machines.

I thought I was only somewhat familiar with diesel engines, but I think you really need to read more about the topic.

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Pistons reverse in every engine. You're thinking of WOT as if it means a screaming engine. It isn't. It's just a matter of designing the engine to produce the right amount of power at WOT. Basically, you just downsize the motor and parts of the system until WOT is the amount of power you want. You do this instead of choking the intake.

Torque is phantom. HP is real. HP is the ability to do work. I can make as much torque as I want with gears (an equivalent to a lever). Give me a lever and a place to stand and I shall move the Earth. I can multiply the force of my bicep enough to move something as massive as the Earth, just very, very slowly.

You can have all the torque you want and if you have no rotational speed, you can't accomplish much very quickly. In the real world, the speed at which you can accomplish something does matter.

So what you need is torque at speed. And torque times speed is HP. This why HP that matters. HP and proper gearing (the lever again) are ALL that matter.

More HP means more power. More HP means you can go faster. It means you can charge batteries faster, or more batteries at the same speed. And given that the electric motor is going to using energy at a particular rate, it matters that the motor driving it can produce energy at a particular rate. So torque alone is a useless measure. What you need is HP.

Yes, stroke length is limited. But if you can't make the stroke long enough, just put a reduction gear on the output shaft.

There are other Diesel electric machines that is true. A locomotive is a great example. But in a locomotive, weight isn't an issue. In a car it is.

You think the Prius isn't designed to run at WOT?

'The Prius minimizes pumping loss by using a high torque range as much as possible with the throttle fully open.' Yeah, it's from Wikipedia, not much I can do about that. Note that the torque range mentioned is in reference to the gearbox (again what I said about proper gearing). The motor runs at WOT to minimize losses and to maximize power output. Then the gearing takes care of producing the right amount of torque at the wheels to propel the car.

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where i live its only around a 50 cent gap (because the regular is over 3.60), but when a diesel gets 20 mpg more mileage i'd say thats pretty competitive, but the initial fill would be quite painful in the pocketbook

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It doesn't get 20 more mpg.

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The thing is, a diesel can run at idle, and get good gas mileage, and keep the engine warm. A diesel can remain running, and not have to continuously shut down and re-start.

AND with a high-current, high-voltage DC system on board, why not have electric cylinder heaters built into the block, to maintain temperature.

I do agree, though that this will be a heavy, expensive vehicle, so equipped, and not for a little econo-box at a low price. But hybrids don't make sense at that level, anyway. If any vehicle would benefit from being a diesel-electric hybrid, it is a big people-mover, or cargo hauler, where weight isn't as big of an issue, and price is less sensitive due to demand not being very elastic.

I am just saying... if a vehicle has a business case to be hybrid drive, diesel combustion can be made to suit it better than gasoline combustion. Other venues do it already, like trains and busses, and even WWII-era submarines. Nuclear fission powered trucks are a ways off yet, though. :D

Maybe restaurants should recycle their old fry oil, and use that to dilute the price of petro-diesel, or something. When something gets expensive, necessity kicks in, and bears some invention.

Mostly, I want them to leave gasoline engines alone, let gasoline cars remain lightweight and less complex. I'll still be buying gasoline burners, unless a diesel hybrid makes REAL sense, and is cheaper to buy, cheaper to feed, and cheaper to maintain, and I need something efficient more than I need to 'enjoy' my drive time.

And that will not really be happening for my personal vehicle anytime soon. But light or heavy trucks, vans, and SUVs might be decent candidates, and lower prices of commercial goods that I buy.

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im sure the same maileage can be achieved by making the polo lighter, more aerodynamic; it already gets better mpg than a prius, why ruin it with more weight?

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