Horsepower vs Torque (2.5T/T5)

Well, just looking at the numbers you give, above, the 2.5T shows the torque from 1,500-4,500 rpm but supplies the HP at

Cheers,

-+JLS

The 2.5T obviously starts delivering torque at lower rpm's. Or it is just defined at that rpm. It is never flat over a range of 1500-4500 rpm.

This is only valid at one rpm. This does not explain the bandwidth. Power = torque * conversionfactor (read: gearing).

Look at the motor data.

high torque advantages: A motor that has a high torque at lower rpm makes driving easier and less nervous. You do not have to change gear often, it drives easier in the mountains, and it can pull heavy weights - diesels are like this. The mileage is probably good too.

high power advantages: when you want to drive in a 'sportive' way. At the high revs you have more power.

I personally would go for torque. We drive a Volvo 440 1.8i, and an old Peugeot 1.9 Diesel. The Volvo is much faster, much more acceleration, much better road behaviour, more comfort etc. But when I must pull a caravan, I take the Peugot for its torque.

Regards,

Pieter Hoeben

Because power is the product of speed and torque, you get higher powers when the max torque occurs at a higher speed. For example, diesel engines have very high torque at low speed, but relatively low max power because they do not operate at high engine speeds.

To fully understand the examples you have given, you need to plot the figures on a graph. Tabulate the published torque figures at various engine speeds and calculate the power in each case, using the formula which you have quoted. The torque on the 2.5T falls off after 4500rpm - so the power doesn't go on rising so steeply as it does on the T5 - which holds its torque right up to 5200rpm (if we believe the figures!).

Cheers, SS

Following what has already been said, hp quoted is at a single operating point. So for a 2.5T delivering 208 hp at 5000 rpm, the torque is 218 ft*lbf. For the T5 delivering 247 hp at 5200 rpm, the torque is 249 ft*lbf.

It is useful to compare hp at consistent rpms where torques are provided, for example:

at 2,400 rpm: 2.5T T5 Torque 236 243 hp 108 111

at 3,000 rpm: 2.5T T5 Torque 236 243 hp 135 139

at 3,500 rpm: 2.5T T5 Torque 236 243 hp 157 162

at 4,000 rpm: 2.5T T5 Torque 236 243 hp 180 185

at 4,500 rpm: 2.5T T5 Torque 236 243 hp 202 208

at 5,000 rpm: 2.5T T5 Torque 218 208 hp 243 231

Between 2,400 and 4,500 rpm, the torque characteristics of these engines are very similiar, thus the hp output is also very similar. At 5,000 rpm the torque on the 2.5T starts to fall off while the T5 is still flat. This is where the hp starts to change drastically between the two engines.

From a technical point of view the 2.5T is a longer stroke slower revving unit than the 2.3 T5 which immediately gives it potentially better torque lower down the rev range. Plus the port sizes are smaller, and cam timing such to allow it to breath well at lower rpm.

The main reason however is that the 2.5T uses quite a small low inertia turbo which can deliver boost from very low engine revs where the T5 uses a larger one which doesnt spool up quite so soon, but can flow alot more air.

Throw in some cunning software in the ECU and the result is as you see in the figures. The 2.5T is able to generate maximum boost of ~0.6bar from about 1500rpm, but at higher revs the engine just cannot breath so runs out of puff early. Torque however is strong and linear right through low to medimum revs....

Tim..

Does anyone have specs on the 2.5T turbocharger (only) and a picture or drawing of the unit? I've got a non-Volvo project that I'm trying to find a small turbo for, and so far, I'm not happy with the size and/or exhaust configuration for my project. you can e-mail them to snipped-for-privacy@charter.net

Thanks!

Ron/Champ 6