WOW just WOW!!!!

I just got to drive a Jetta TDI... WOW!!!

I may have just driven my next car. Plenty of spunk, It handles! And the mpg was fantastic! The car was well broke in with 10k miles on the OD. What fun. Mixed driving, and I mean very mixed, ave 50 mpg out of the car. It was comfortable, quite, all most insulating.

The car belongs to one of my customers. They did buy it new at invoice. It is a base model with navi. They have averaged 46 mpg with it since purchase. They drive a lot of hwy. Will see how it holds up over the next year or so. They report no problems with the car at all.

I was very impressed with the car. Falls under OMG. If we just hadn't bought the HCHII I would be trading the MZ3 right now.

I was very impressed!!!!!! I don't think there is any need to look forward to CR-Z or any other hybrid from this point forward.

 

What year was it, Jeff?

I'm still sad we can't get the iCDTi over here...

 

09, Dark silver, gray interior, 6MT that just flicked through gears. We put 100 miles on it and did top of calcs for the mpg. He had just filled it up 2 miles from the house. So I refilled it at the same place/pump. They only have one oiler pump there.

If VW can make it work, it's clear Honda does not want to make it work. I'm about to blow Honda off as the new Asian GM anyway.

If I had been driving it like the wake me when we get there HCHII I'm sure I would have been in the high 50 mpg range with the A/C on.

I was very impressed with the car. Now the question is,,, will it turn into the typical VW nightmare I see so much of here.

 

My understanding is that they have gone with a new electrical supplier -- so those little gremlins should be gone.

As for maintenance, from what I hear you are still best off looking for a support network rather than relying on the dealer. It seems most of them still haven't a clue about proper diesel care.

 

But it still idles at stops, right?
.
_H*

 

Sounds good.
I've read that the base TDI stationwagon is supposed to MSRP at $24000- I wonder what the actual price of a TDI SW is? Is the Passat bigger than the Jetta?

A TDI SW would be a pretty good USA road trip vehicle.
Charlie

 

Did not notice a auto stop, nor did I FAS it.

 

I just requested a quote from the local dealer via e-mail. I don't expect a reply because they known to be A-Holes. I should not go there. But what the hey.....

 

A diesel engine at idle doesn't burn fuel at anything like the rate of a gas engine. A gas engine has to do a fair amount of work to draw air against a closed throttle plate, which is why you see ~0.3gph or more even in an engine as small as our 1.5L powerplants. The diesel doesn't have this problem since the intake path is completely free and load is controlled by the amount of fuel injected. From what I've read you are looking at less than 1/3 the consumption rate for a comparable diesel.

 

My 6.6L diesel only burns .25-.3 gph at idle. So a 1.xL diesel might be more like .1gph or less?

 

I was so impressed with the TDI I called Excel! I was impressed to beat hell with it. When my wife got in from her shopping, bill pay, library, video store, yard sale run in her HCHII. I told her,,, " I have found my next car " It's not a BMW 1 or M3 a CR-Z or a 400+ hp Holden GM import. It's a Jetta that begs to be driven. I showed her the car on the net and she loves it!

 

All dealers are good for is warranty work! As for idle, I'm sure there is not a gasser that can beat it [none hybrid]. No auto stop. But what the hey, It didn't seem to understand the A/C was on full tilt boogy either. It was a German/Mexican plus MZ3 wonder.

 

.25-.3 GPH for 6.6 liters! My 5.7 Chevy burns .6-7 gph at idle-the 3.5 Honda burned .4-5 gph(ac on and off)-the 5.6 titan was the same .6-7gph. The 1.8 liter Prizm(2001 corolla) burned .2 gph.

Charlie

 

In 1982 Mercedes eliminate the throttle butterfly on their diesel engines. The resulting increase in fuel mileage was 7%.

Before they eliminated the throttle butterfly the engine would continue running when there was a vacuum leak in the central locking system. When a door vacuum servo diaphragm failed the air being sucked through a 2 MM hose would be enough to keep the engine running and you had to open the hood and push the fuel shutoff lever at the fuel injection pump to turn the engine off, obviously a real problem for some drivers not completely familiar with the system, especially those who had not read the owners manual!

While pumping losses are a certain portion of the increased efficiency of diesels, the real source of increased efficiency is the much higher compression, and the fact that diesels will run as lean as 50 to 1 air-fuel ratios.

For the sake of comparison and understanding consider a diesel versus gas engine with each having 10 square inches of piston surface area. The diesel has a 22 to 1 compression ratio and the gas engine is 10 to 1.

At 0 manifold vacuum on the gas engine the theoretical highest compression would be 14.7X10X10. Thats 1470 pounds of compression pressure (atmospheric pressureXsurface areaXcompression ratio).
The diesel having no manifold vacuum would produce 14.7X22X10 pounds of compression pressure. Thats 3234 pounds of pressure.

When the fuel is introduced and ignited the heat of the combustible mixture increases from the temperature of the compressed mix to the temperature of the ignited mix.
Remember when you compress air the temperature increases before combustion occurs, so the compressed mix temp is higher in the diesel that in the gas engine before combustion.

In every IC engine the power developed is the difference in the compression pressure and the combustion pressure. This is the "leverage" that provides power on the power stroke. Since diesel fuel has more energy per unit of volume this gives some advantage to the diesel engine.

Compression energy is much more significant than the energy required to pull air past a throttle restriction, which can only be a single atmosphere of 14.7 PSI even if the throttle plate was a perfect seal and the engine sucked every molecule of air out of the manifold.

The reason why the large diesel engine uses so little fuel to idle is the much greater leverage on the heated misture when it ignites in a diesel engine as well as the greater BTU content of the diesel fuel itself. Starting at 22 to 1 the mixture expands to about 7 times its compression pressure in either diesel or gas. Since the diesel starts with 3234 PSI versus the gas engine with 1470 PSI you can see the combustion pressure is much higher in the diesel which means much more pressure to push the piston down and create power.

The other side of the equasion is the considerably more work is required to compress the air in the diesel than in the gas engine, and the mass of the pistons and connecting rods as well as the crankashft and other parts in the diesel need to be much greater than in the gas engine. This creates greater reciprocation losses in the diesel compared to the gas engines.

Comparing all the positives and negatives in gas and diesel engines, especially the much greater compression and higher btu content of the same volume of fuel, it should be fairly easy to understand why the diesel engine is more efficient. Above and beyond those two basic advantages is the fact that the diesel can run at AF mixtures as high as the previously mentioned 50-1, almost twice as high as the Lean burn Honda engines used in the VX, HX, and other models.

With the price of diesel here about the same as regular gas, diesel has become a much more attractive option. I believe this was due to the legislation enacted a few years back that required the refiners to dramatically reduce the sulfer content of diesel fuel, which also helpd reduce emissions quite a bit. Lat year diesel here was $1 per gallon more than premium, as the refiners passed the cost of the sulfer reduction technology on to the consumer.

My favorite hybrid would be a diesel hydraulic configuration. I have a Kubota D600 that produces 16 HP at 1 gallon per hour of fuel. There are diesels that will beat that amount, but the practical limit of current diesels is about 20 HP per gallon per hour. In order to get to 100 MPG with no other hybrid system or hypermiling, you need to build a vehicle that can go 100 MPH on 20 HP, which is a very tall order to fill, and would require extreme aero and rolling resistance improvements.

Slightly OT but it does explain why a large V8 diesel can idle on the same volume of fuel as a much smaller gas engine. Diesels alos tned to idle at lower speeds, and AC use is a much smaller power drain on the diesel becasue of the already discussed compression energy requirements.

regards
gary

 

Nice explanation Gary. I think the new TDI 2.0 has 4 throttle butterflies, but they are used for EGR control and are not directly related to what the driver does with his right foot.

I'm having fun with my Sportwagen TDI. Fine driving car; just learning how to get best fuel economy out of it at 4K miles.

 

Another diesel advantage is they can take 15 psi boost on normal fuel( partly due to the running on 50/1 lean gary mentions). Spark motors start requiring higher octane and start dialing back the advance once boost is over 5 psi. In the USA I can't recall any boosted motor that actually got better mpg than a non boosted-but larger- version in the same vehicle. All the little turbo 4's are in little hot rods, and they get relatively poor mpg.

What is the actual peak combustion pressure of a 20/1 diesel with 15 psi? Gee with 20/1 compression you get to 3000 psi-15 psi boost 6000 psi- ignite it and where does that put peak pressure?? What is peak cc temp-1200 f or so-wow that would put peak pressure in the 15000 psi?? Hard to believe- but..
Charlie

 

I have to be honest. So of the reading at tdiclub is scary.