T3 SYNCRO AND TORQUE : IT'S TORQUE AT THE WHEELS THAT COUNTS !
By Michel Thevissen
If you think you cannot compare a T3 syncro 1600TD engine with the 175HP TDI powered T5 4motion : you’re right, ... only not in the way you thought !!
When talking about top speed the T5 4motion is far superior. But most of us want a syncro because we want to drive it offroad from time to time.
When not thinking of ground clearance, one would think the T5 superior to the T3 when offroading when it comes to the engine. The T5’s 175 HP TDI engine has a maximum torque of 40 KgM at 1900 rpm, the T3 1600Tdwith 70 HP has a maximum torque of 13,8 KgM at 2500 rpm...
Lets make some calculations and see what the gearbox does with this power :-)
To make the comparison honest, we put on the same tires with a diameter of 72 cm and a circomference of 2262 mm.
The cars in this comparison : T3 JX diesel 70HP 16” syncro 1600TD,
T3 DJ petrol 112HP 16” syncro 2100i
T5 TDI diesel 175HP 4motion
For the results in Nm : 1kg 9,81Nm (about 10N), 1 HP = 736W
A Torque at the wheels at maximum torque and in smallest gear (V1 for the T5 and G for the T3)
T(Kg) = (Max torque x 0,85) / wheel radius x (smallest gear x final drive)
T3 1600TD T = ((13,8x0,85)/0,36) x (6,0300 x 6,17) = 1212,266 Kg
T3 Petrol DJ T= ((17,4x0,85)/0,36) x (6,0300 x 5,43) = 1345,187 Kg
T5 4motion175HP T=((40x0,85)/0,36) x ( 3,9200 x 4,60) = 1703,022 Kg
B Speed (S) in km/h in smallest gear (V1 or G) at max engine torque and Rpm (revs a minut)
S = (N/Ix) x U x 0,05753 in km/h
N is Rpm, Ix is total drive, U is circumference wheel
T3 1600 TD S = (2500/37,205520) x 2,262 x 0,05753 = 8,744 km/h
T3 2100i DJ S = (2800/32,74) x 2,262 x 0,05753 = 11,129 km/h
T5 4motion 175HP S = (1900/16,422) x 2,262 x 0,05753 = 13,712 km/h
As the speed of the T3 DJ and the T5 are too long for offroading we’ll have to calculate it at the lower speed of 8,744 km/h (the better speed)
C. Calculation of rpm at “the better speed”
T3 petrol : rpm = 2800/11.129 x 8.744 = 2200 rpm
T5 4 motion 175 HP : RPM = 1900/ 15,056 x 8.744 = 1100 RPM
D. Recalculation of torque at the wheels in function of these new rpm’s
T3 1600TD : T=((13,8x0.85) / 0.36) x (6.03x6.17) = 1212,266kg
T3 2100i DJ: T=((16.8x0,85) /0,36) x (6.03x5.43)= 1298,802 kg
T5 4motion 175 HP T= ((22X0,85)/36) x (3,57x4,6)=853,032 kg
The T5 4motion 175 HP has in it’s lowest gear a lot less torque then a T3 1600TD.
The DJ engine, 112HP waterboxer has the most torque on the wheels