POWER, TORQUE, FUEL CONSUMPTION

[SkyPup]

Here are the data for the Brake Specific Fuel Consumption (g/Kwhr), Torque (Nm), and Horsepower (Kw) for the 98-99 North American TDI engine rated at 66Kw (90 HP)at 3,750 rpm and 210Nm (155 lbs)at 1,900 rpm. A3 TDI are similar except they put out 66Kw (90 HP)at 4,000 rpm and 205Nm (149 lbs)at 1,900 rpm.

RPM (G/Kwhr) POWER TORQUE
brake specific cons (Kw) (Nm)

1,000 210 15 150
1,500 200 30 190
2,000 190 44 210
2,500 210 54 205
3,000 225 60 190
3,500 240 65 175
4,000 250 65 160
4,500 265 35 80

What this info shows for the VW TDI is that torque is strongest from 1,500-2,500 and signs off rapidly after 3,000 rpm. Horsepower doubles from 1,000 to 1,500, and then doubles again from 1,500 to 3,000, signing off at 4,000 rapidly.
Best Fuel Specific Fuel Consumption is from 1,500 rpm to 2,500 rpm where is a big dip in consumption above idle engine at 2,500 with the low at about 2,000. For best fuel mileage, keep the engine between 1,500 and 2,500 at all times!

Hmmm, it is kinda hard to keep things inline when attempting to create columns. The data is to be read from left to right across, and then it matches the headings with RPM first, BRAKE SPECIFIC FUEL CONSUMPTION 2nd (G/Kwhr), POWER 3rd (Kw), TORQUE(Nm) 4th.

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99 JETTA TDI HERR WETTERAUER TORQUEMEISTER
98 KAFER WETT SPEKTAKULARE TURBOKOMPRESSOR
97 KTM 620 ADVENTURE RALLY PARIS-DAKAR SUPER THUMPER
ICH LEBE MEIN TECHORAD JETTA TDI MIT DIREKTEINSPRITZER TURBOKOMPRESSOR

[This message has been edited by SkyPup (edited August 09, 1999).]

 

[lundgrji]

Skypup, thank you for the info. The BSFC numbers you found are at WOT, or full power, right? It sound like a 6th gear to put the engine back to 2000 rpm at 70mph would be beneficial.
Have you ever stumbled across BSFC numbers for part load conditions. For instance, suppose a road condition allows either 1600 rpm in 4th gear or 2400 rpm in 3rd gear to provide roughly the same speed. Which would be more efficient during this part load condition? Another example would involve accelerating, with the question being should one accelerate at full load between 1500-2500 rpm or part load to extract max efficiency?

 

[Tazzman]

Thanks Sky pup

Now I'll have to go ut and really try to do
some millage miesering.
Got to keep that millage record up here where it belongs,,,,,

so look out for some out standing and unbeleiveable millage guys.

Tazz

JS SMKN

 

[**DONOTDELETE**]

Hi,

One would think that the higher torque down low would result in better acceleration in higher gears. While it's great, I've noticed that my car seems to accelerate from 50-70 a few seconds quicker in fourth than it does in fifth. Could this be because the slightly lower torque is working against an easier gear? For example, 10% less torque in a gear that's 20% easier to push could still equal more torque to the ground. I realize my numbers are way off, but do you think there's fact in my theory? Anyone have the time to crunch torque vs gear ratios to come up with actual car-moving potential?



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Scott, KE4WMF
98 Jetta TDI w/39,000 mi
53 mpg (US) w/AC

http://members.aol.com/ThreeRibs/Volkswagen.html
(Features TDI Articles and Sound Files)

 

[GoFaster]

Skypup: Good stuff! This explains why fuel consumption takes a crap if you drive much over 120 km/h continuously. I'd sure like to see what part-load numbers are like. If it's like many other diesels, I'll bet that best BSFC is near 2000 rpm over a wide range of engine load.

Scott, You're on the right track.

For maximum possible acceleration, whatever gets the most horsepower to the ground is what counts. And horsepower depends on both speed and torque. For example, using the above table, at 2000 rpm the engine has 210 N.m of torque. At 4000 rpm, it has 160 N.m, but the extra gear reduction means it can get more power to the ground.

All you need to do is look at the horsepower numbers to tell where to shift for max acceleration ... i.e. shift at 4000 rpm or so, to keep it producing 60 - 65 kW.

In reality, one doesn't need to do this all that often. The nice thing about the TDI engine is that it produces a useful amount of power at anything above 1500 rpm. Not many 4-cylinder car engines produce 2/3 of their maximum power output at just 2000 rpm!

Brian
'96 Passat TDI

 

[mickey]

Radhaz: That's exactly it. The higher gearing costs you more than you'd gain from being in the "optimum" powerband.

-mickey