Simple formular for better economy ****LESS RPM=MORE MPG****

It is very easy to get better fuel milage. The basic idea is to get to the highest gear possible as soon as possible. Do not be afraid to shift up earlier than you would ever think of with a gasser. When power is not required RPMs as low as 1000 are perfectly acceptable. Skip gears if condition allow. The best economy should be around 35-38 mph in fifth gear on level ground, but how often can you drive in that perfect world? Just remember if the power is not needed shift up and enjoy the torqe.

[This message has been edited by jayb79 (edited August 14, 2000).]

That doesn't seem to agree with the numbers we got from the European forum members who have mpg computers. There were a few mpg numbers for below 1500 rpm, and the results showed that below 1500 rpm yields lower mpg. I admit there wasn't extensive samples at below 1500 rpm.

Hey European forum members with mpg computers: Maybe you can give us more mpg numbers for 1000 to 1500 rpms in the various gears.

I won't drive my TDI below 1,500 RPM's in order to avoid the chance of lugging, even with the Upsolute / Tuning Box upgrade which greatly improves low-end torque.

"RPM's as low as 1,000" can cause unnecessary damage to the engine's bearings and etc... when lugging most likely will occur.

I like Mickey's definition of lugging - being, when the engine cannot "moderately accelerate."

Lugging is not worth it while attempting to save a few cents and makes no sense.

Prevention is better than redemption!

Please quantify "moderately" as in moderately accelerate. Just how many feet per second per second is "moderately"?
1500 rpm "can" cause bearing damage at a rate 50% greater than 1000 rpm under the right conditions.
Did you know that my stock TDI produces a dynamometer measured 11 hp at full throttle at 650 rpm in third and fourth? What lugging?
Tirade over.

I'm more concerned about the transmission than the engine. In high gears the torque is being forced through smaller gears, with fewer teeth. My idea of "lugging" is forcing a lot of torque through small gears. If you step on the accelerator and very little happens you should downshift and let the engine spin a little bit. That's all. Stomping the pedal to the floor in 5th gear at idle speed and keeping it there until you reach freeway speed isn't the best thing for the car. It's also inefficient and slow.

I would agree with jayb79 to the extent that you should shift earlier than in a comparably sized gasser, but remember that these are 1.9 liter 4 cylinder engines, not 20 liter Caterpillar engines. They like to spin. And remember also that turbocharging increases the engine's thermal efficiency. If you shift up before the turbo gets spinning you're not helping anything. For everyday "keeping up with traffic" I like to shift at about 2200 rpms. When you shift up the rpms land just below the engine's torque peak. You end up "bracketing" the most efficient rpm range.

-mickey

Jonathan is right - lugging is a non-issue with the TDI, as I have stated so many times before .

You can't lug a TDI unless you are trying to force it below idle speed.

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Ric Woodruff

Everyone should believe in something...
I believe I'll have another beer!

1998 Jetta TDI Sport

[This message has been edited by Ric Woodruff (edited August 15, 2000).]

Ric, Ric, Ric...whether or not lugging is an issue for the engine is it certainly an issure for the transmission.

-mickey

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by mickey:
Ric, Ric, Ric...whether or not lugging is an issue for the engine is it certainly an issure for the transmission.

-mickey<HR></BLOCKQUOTE>

There is no such thing as "lugging a transmission". It has been match to the engine to handle anything the (stock) engine can dish out. It is far from the weakest link. As long as you don't suffer a fluid loss or have a manufacturing defect, they will pretty much outlast everything else.

The most stress occurs on a transmission when the engine torque is highest, which is mid range RPM. At low engine RPMs (no matter what gear you are in), stress to the transmission is low, because engine torque is low.



[This message has been edited by Ric Woodruff (edited August 15, 2000).]

Just apply a little common sence to the formular and there should never be any trouble. Higher gears and lower rpm is only for maintaining speed if you need the power you will need to downshift.

Example: Speed limit is 30-35 mph grade is level or down hill traffic is moderate,load is lite(your car is not full). You come to a stop light then start out in first go to third, traffic ahead looks clear the grade is running downhill, my next gear choice would be fifth with very little or no throtle required.

Ric, you don't know what you're talking about. Putting extra strain on smaller gears will cause them to wear out faster. It stands to reason.

Lugging the engine is also inefficient. The longer the hot combustion gases are in contact with the metal surfaces the more heat is lost into the coolant instead of being used to propel the car. You want the piston to get out of the way quickly. This is the whole reason why Direct Injection engines are more efficient than IDI engines. The prechamber absorbs too much heat in an IDI engine.

Don't believe me? VW will tell you that the TDI's maximum efficiency under a test load occurs at about 2000 rpms. (I forget the exact number.) Why isn't it at idle speed? Because the turbocharger isn't working and the piston is taking to long to move out of the way of the expanding gases.

-mickey

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by mickey:
Putting extra strain on smaller gears will cause them to wear out faster. <HR></BLOCKQUOTE>

Mickey, you underestimate smaller gears. Do you look down upon midgets and dwarfs too???

But seriously, smaller gears turn that much faster to make up for being smaller. This means that the stress on small gears is virtually the same as large gears, for the reason stated. Understand yet??? (i sure hope so).

Heres another one.
If you don't stop, don't use first. Try it.

for "california stops" at stop signs and turns, I use 2nd as long as the wheels haven't locked full stop.

On inclines you get a sense for when it will stall and learn inherently if you need to go to first.

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Blk/Blk Debadged 2000 Golf GL TDI