The torque & power of WRC cars, part 1

[OldF]

It all begun last fall when a friend of mine asked me how much power does the WRC cars have but I couldn’t give him any exact figures. I had heard / read about 330 hp but I wasn’t satisfied with that so I started to search for some answers. I found this web site http://www.kosunenracing.com/turbo.html and http://www.kosunenracing.com/ga.html (unfortunately only in Finnish) where they tell that 330–360 hp (with a 34 mm restrictor) have been measured from Group A Mitsubishis in Finland and the WRC cars are estimated to have 350-380 hp and torque between 650-750 Nm.

When I visited SWRT’s web site I got really curious because they say that the Subaru has a torque of 700 Nm @ 4000 rpm. That would mean that the power @ 4000 rpm would be 399 hp (P (hp) = T (Nm) * revs (rpm) * 0,0001424 -> 700 Nm * 4000 rpm * 0,0001424 = 398,7) and the power peak is on higher revs than the torque peak, so peak power for Subaru must be over 400 hp.
http://www.swrt.com/the_team/the_team.html (The car / Technical specification)

On Jussi Välimäki’s web site I found more information. The car (Mitsubishi Evo 8) he’s driving in the Finnish championship is the same car with which he won the Asian-Pacific championship in 2005. It has been modified to a Grp A car and the figures for the car are: Peak power (Maksimi teho): 350 hp @ 4800 rpm and peak torque (Maksimi vääntö): 650 Nm @ 3500 rpm. I don’t think these figures are any estimates because AMW Dyno Service is the other one of the two companies who takes care of the maintenance of the car. Putting the car in a dyno is probably the only way to find out what have been achieved with the tuning of an engine and the effect of the adjustments.
http://www.jussivalimaki.com/ (Mitsubishi Lancer)

I decided to put the figures in Excel and make some power calculations and finally graphs of the results. The torque figures (540–600 Nm) I found for other cars weren’t even close the one of Subaru so I used for Subaru also a lower torque I found in a magazine. As a base (or model) for the torque curves I used an estimate curve for WRC cars from a magazine (VM 1/2007).

http://i267.photobucket.com/albums/i...rque_graph.jpg

And the same as an Excel graph:

http://i267.photobucket.com/albums/i...2000_graph.jpg

The figures I used to begin with are:

Ford: 550 Nm @ 4000 rpm & 300 hp @ 6000 rpm
Citroen: 570 Nm @ 2750 rpm & 320 hp @ 5500 rpm (I put the torque peak @ 2800 rpm)
Subaru: 590 Nm @ 3500 rpm & 300 hp @ 5000 rpm
Skoda: 600 Nm @ 3500 rpm & 300 hp @ 5500 rpm
Peugeot: 580 Nm @ 3500 rpm & 300 hp @ 5250 rpm (I put the ”power peak” @ 5300 rpm)
Mitsubishi: 540 Nm @ 3500 rpm & 300 hp @ 5500 rpm
Suzuki: 590 Nm @ 3500 rpm & 320 hp @ 4500 rpm

After copying the estimate graph for every car, I put two points in the graph, the peak torque and the calculated torque at the revs where the power is 300 hp (320 hp for Citroen). For example for Ford the two points are 550 Nm @ 4000 and 351 Nm @ 6000 rpm (T = P / (revs * 0,0001424) -> 300 / (6000 * 0,0001424) = 351 Nm). After that I adjusted the curves to rise and decline smoothly.

And here are the results for “torque low” and “power low”:

Torque: http://i267.photobucket.com/albums/i...torque_low.jpg

As you can see the Citroen’s curve start to increase at low revs and the Ford’s at higher revs. In this graph Jussi Välimäki’s grp A Mitsubishi has the highest torque except for the WRC graph that is an estimate.

Power: http://i267.photobucket.com/albums/i..._power_low.jpg

Because of the early increase of the torque curve, Citroen has the highest power between revs 1800-2900 rpm. In the middle revs (3000-5200 rpm) the power is little lower than for the other ones but is again second best of the WRC cars beyond 5200 rpm. In the same magazine (TM 14/2005), from where I picked some of the figures, Juuso Pykälistö told: “The engine of the Citroen is a rev engine. It has a broad rev band, the gear shifts takes place far beyond 6000 rpm and at lower revs it’s not so powerful compared to the Peugeot. On the other hand the Peugeot’s rev band ends just after 5000 rpm”. Ford has the highest power beyond 4500 rpm. Still Mikko Hirvonen tells in the same magazine that: “The Ford can be safely driven with high gears and low revs”. These two comments are a little bit of mystery for me but I’m neither an engineer nor a rally driver. Subaru’s power starts to decline quite rapidly after 4700 rpm. Mitsubishi doesn’t have so high power but the curve is quite flat (easy to drive?) and is third best beyond 5600 rpm.

The next task was to put some more torque so I just added 110 Nm the whole way. I picked the 110 Nm from Subaru’s two different torque values 700 Nm and 590 Nm, which I used in the beginning.

Torque: http://i267.photobucket.com/albums/i...orque_high.jpg

Power: http://i267.photobucket.com/albums/i...power_high.jpg

Ford has the highest power, 431 hp @ 5000 rpm and Mitsubishi has the lowest power, 387 hp @ 5300 rpm.

The following ones I made by keeping the same torque as in the “high” graph but lowering the torque so as the curve goes true the point where the power is 300 hp (again 320 hp for Citroen). So these are a mixture of the two previous ones.

Torque: http://i267.photobucket.com/albums/i...que_medium.jpg

Here the curve of the Mitsubishi and Citroen are side by side after the torque peak. For the other ones it seems that the curve is declining a little bit to fast.

Power: http://i267.photobucket.com/albums/i...wer_medium.jpg

Suzuki’s power is declining fast with this option and Citroen would have only 337 hp.

And here are graphs by make.

Ford: http://i267.photobucket.com/albums/i...rque_power.jpg

Citroen: http://i267.photobucket.com/albums/i...rque_power.jpg

Subaru: http://i267.photobucket.com/albums/i...rque_power.jpg

Subaru SWRT: http://i267.photobucket.com/albums/i...rque_power.jpg

In the SWRT graph I put the “medium” and “high” from the previous and the figures from the web site. As you can see, the result for 700 Nm @ 4000 rpm will generate a peak power of 413 hp @ 4300 rpm which is higher than for the “high” option, 404 hp @ 4500 rpm.

Skoda: http://i267.photobucket.com/albums/i...rque_power.jpg

Peugeot: http://i267.photobucket.com/albums/i...rque_power.jpg

Mitsubishi: http://i267.photobucket.com/albums/i...rque_power.jpg

Mitsubishi Grp A: http://i267.photobucket.com/albums/i...rque_power.jpg

Suzuki: http://i267.photobucket.com/albums/i...rque_power.jpg

I found also some different figures for the Suzuki at Sebastian Lindholm’s web site http://www.sebateam.fi/

Suzuki SL: http://i267.photobucket.com/albums/i...rque_power.jpg

[Mirek]

I don't have enough energy for Your whole article tonight because it is very late but here is what I was told (please don't ask who are those numbers from but it is from people inside )

Octavia WRC evo 3 was 320 (maximum 330) Hp and I'm sure about it.
Fabia WRC 05 has some 330, maybe up to 340 Hp at about 4500 Hp and about 640 Nm at about 3000 rpm.
Corolla WRC Lexus is 610 Nm and 325 Hp.
Focus 04 was 680 Nm and 350 Hp at about 5000 rpm.
Focus 06 was 750 Nm and 350 Hp at about 4500 rpm.

And for Your second part. I know that one particular Punto S2000 is 262 Hp and second 272 Hp. Both are client cars but one is aproximately half year older. From other cars I know Suzuki Swift S1600 is 238 Hp. I was told some others but I can't confirm them, Clio S1600 240 Hp, Punto S1600 232 Hp. C2 S1600 was told to be slightly less powerfull but with much more torque against Swift.

I also saw two dyno charts of Evo 9 and one was 533 Nm at 3250 rpm and 283 Hp at 4000 rpm and the second was 560 Nm at 3400 rpm and 278 Hp at 4200 rpm.

[Micke_VOC]

Interesting to read.
Have heard from a friend when he mapped his Mitsu 6.5 that the result was
380 hp with wrc restrictor. Dont know the Torque.

[Finni]

I had some difficulties to understand those deductions but anyway I have always had difficulties to believe that wrc-cars would have only 350hp because even group N cars has 280-290. There is definitely more than 60hp between group N engine and modern wrc.

[Nenukknak]

Very interesting, but how do you know how these curves go? i.e. how fast or slow they decline/incline

[leno]

interesting article

[N.O.T]

very insightful thank you....

[playmo]

... P=T*revs*0,0001424

Isn't this formula used only on linear systems? and since the behaviour of Power & torque versus revs isn't linear, this might be wrong. I think.
But anyways it is very interesting, and makes sence as it is noticed by everyone here that the citroens "pull" better out of corners etc...

[Mirek]

playmo:No, it works fo any engine anytime. It is simliffing of the original formula which says that power equals torque multiplied by angular velocity of the crankshaft.

So the original is P (W) = T (Nm) * omega (1/s) = T * 2 * pí * rpm / 60

And for recomputing Watts to Hp it needs to be further devided by 1000 and multiplied by 1,36. The result is the same.

[OldF]

First, I had to split the post in two parts because it exceeded the maximum length of a post.

Mirek,

Focus 04 was 680 Nm and 350 Hp at about 5000 rpm.
Focus 06 was 750 Nm and 350 Hp at about 4500 rpm.

Do you know the revs where torque is 680 Nm and 750 Nm.

The 0,0001424 comes from when converting the units for angular velocity 2 * pi * n (1/s) to rpm and W to hp. It’s easier to calculate with torque in Nm and revs in rpm.

1,36 * 2 * pi / 60 * 1000 = 0,0001424 => 1 / 0,0001424 = 7024

P (hp) = T (Nm) * Revs (rpm) * 0,0001424 or P (hp) = T (Nm) * Revs (rpm) / 7024

More about that here: http://en.wikipedia.org/wiki/Torque

Next some options for another units:

Power in kW:

P (kW) = T (Nm) * Revs (rpm) * 0,0001074 or P (kW) = T (Nm) * Revs (rpm) / 9549

Power in bhp and torque in lb-ft:

P (bhp) = T (lb-ft) * Revs (rpm) * 0,0001904 or P (bhp) = T (lb-ft) * Revs (rpm) / 5252

Power in kW and torque in lb-ft:

P (kW) = T (lb-ft) * Revs (rpm) * 0,0001420 or P (kW) = T (lb-ft) * Revs (rpm) / 7043

Here is a good unit converter: http://www.statman.info/conversions/power.html

Ok, now I try to explain how the graphs where made.

Here are the links to the graphs needed:

http://i267.photobucket.com/albums/i...rque_graph.jpg

http://i267.photobucket.com/albums/i...mple_table.jpg

http://i267.photobucket.com/albums/i...mple_graph.jpg

Step 1: As a base (or model) for the torque curve was the WRC (arvio) = estimate. The figures are in the table (Example_table.jpg) in columns at step 1.

Step 2: The peak torque for the WRC estimate was at 670 Nm and at 3400 rpm. For Ford the values are 550 Nm at 4000 rpm so I subtracted 120 Nm from the WRC estimate and moved the peak to 4000 rpm.

Step 3: Next I adjusted the values of the torque between revs 4300 rpm and 6500 rpm so as the value of the torque at 6000 rpm is in balance with 300 hp (T = 300 hp / 6000 rpm * 0,0001424).

Step 4: I just added 110 Nm the whole way. The peak torque is now 650 Nm.

Step 5: For the final step I adjusted the values of the torque between revs 4200 rpm and 6500 rpm so as the value of the torque at 6000 rpm is in balance with 300 hp (T = 300 hp / 6000 rpm * 0,0001424). This last one is a mixture of step 2 and 4.

I hope this will clarify how the curves are done and how the curve declines. The values before the torque peak follows from the WRC (arvio) and the values between revs 0 rpm – 1700 rpm I adjusted so as the power curve would go smoothly toward zero.