Thread: dyno'd the 300tdi yesterday

Problem is that with DYNO DYNAMICS rolling roads , the option for monitoring/logging RPM is a $10.000 extra when you buy the Dyno , Hence why most (Not all) produce only a ludicrous Road speed graphable axis . As for that silly torque figure , its not even Torque, is actually "Tractive Effort" which is determined by a algorithym for each dyno manufacturer , Hence the big diffrence in readout final figures from Dynodynamics and Mainline . One must understand the "ramp rate" or applied load offen descibed as RPM per second rise rate . Using "rolling road Dyno's for anything other than comparitive analysis and tuning is a total waste of time . TDI 200 and 300 produce on average 105HP (84 KW) . Due to 300's higher boost it will have more torque (up to 20% more) but only 1 or 2 more Horsepower . The important bit is what RPM was this delivered at .Power at 4000 rpm / torque at 1800 .
Only Dyno on Dyno's that have the three plot lines on them . Torque . Horsepower and AFR , with RPM as the x axis .
KW/HP NMs/ Ft/lbs
LR 200 tdi (1990 - 1994 model years) 83KW/111HP @ 4000 198NM/146 ftlbs@ 1800
LR 300 tdi (1995 -1997 models) 84KW/113HP @ 4000 265NM/195ftlbs @ 1800

Found these numbers in old and new terminolgy for those that need it ,

that NM at the wheels sounds right, seen a few turboed 80s/gu get dynoed and see 280kw and well over 1600f/bl at the wheels,

allso you will get more NM in 3rd then you would in 4th, why was 3rd used and not 4th as that is 1.0:1 in the gbox,

1600ftlbs ? absolute utter garbage !!! did it have Tracks instead of tyres ? First gear low range perhaps ? Again , chassis dynos use "Tractive effort" which is calculated from roller speed, roller load and ramp rate . Those numbers are purely Bench racing BS . !

im no expert at dynos,, but have a basic idear how they work, and only sayen what iv seen and how wev tuned cars with it,

spent more time on a rolling rd tuning then actuly geting KW readings tho,

its a great tool for driving fualts finding, wish my work would get one,( i got more chance of a pay rise then getting one of them)

The reason why you get a higher tractive effort/torque at the wheels in 3rd than 4th is simply due the the multiplying effect of the gear ratio.

In a lossless geabox (hypothetical) the power put into the box would equal the power taken out of the box. Given that power can be calculated from the product of RPM and Torque then if the gearbox output shaft spins at a lower RMP then the torque figure must go up to keep the product of RPM and Torque the same. There is a constant involved in order to get the power value in the correct units however I have not looked it up and I don't know that anyone is going to be too worried about it, as an equation we could write;

K X RPM(1) X Torque(1) = K X RPM(2) X Torque(2)

K is the constant, so if we keep RPM(1) and Torque(1) at a fixed value and change RPM(2) by selecting different gears then as RPM (2) goes down Torque(2) must go up to make both sides of the equation equal.

The same thing happens with your wheel speed as the RPM go down as the rotations go down as the drive line goes through a diff or tcase then the torque must go up to satisfy the basic principle of conservation of power.

Once you go away from a lossless drive train all the power lossess result in the generation of heat however the conservation of power law tells us that the amount of power used to generate the heat is a measure of the loss in the drive train, i.e.,

Power from source = Power at the wheels + Power lossess to heat etc.

Power at the wheels = Power from source - Power lossess to heat etc.

I therefore think it is possible to have a much larger torque figure at the wheels than what is at the flywheel, this is simply due to the rmp drop as the driveline goes through the tcase and diff.

What fudge factors are used by Dyno manufacturers that go into tuning garages I cannot vouch for and cannot say that the dyno readouts are Nm, ft/lbs or some other unit used for tractive effort.

Hope that helps

There is always more torque at the wheels than at the crank. But dyno's can't measure wheel torque, they can only measure driving force at the rollers and the speed the rollers turn.

If you get a power curve and you can relate that to engine rpm then you can derive a torque curve from it. It's simple maths.
But if you don't know the rpm, it's guesswork.

The other problem, it's very hard to tell from a dyno plot whether the operator has tried to correct power readings to flywheel or whether they're truely at the wheels numbers.
A tweaked engine at the ground can look similar to a corrected engine at the flywheel.

Any NM figure you get from the dyno wont be right and will not be able to relate it to what the engine is producing.

KW 'can' be accurate but it will depend on what dyno and what mode (shootout etc).

The 300tdi is likely producing sub 300 NM.

LANDY DYNO DAY FTW!!!!!