WRC Testing

[jiipee64]

Toyota looks pretty fast live...

[J_n_z]

Huge? What is huge about 400 Hp? The torque is unchanged compared to 2016 cars (still way less than 2009 cars), ...

I can't understand talking about torque and power separately. Torque on crankshaft is pointless as it can be compensated with higher revolution speed to generate certain power (my bike has cca 145 Nm torque at 30rpm). In the end, power is the thing, that moves things around.

With bigger restrictor you can have more air ie. can burn more fuel ie. more power. If it is done with less revs and bigger volume/rev. or more revs and smaller volume/rev. it is not that important.

Engune ability to pull from low revs... is very relative to what low revs are. Much more important is range of useable revs. to achieve required speed with limited number of gaears... But with modern fast shifting gearboxes, shifting while sliding in a corner, it can be compensated ass well.

[dimviii]

Michelin video with c3 tests
https://www.youtube.com/watch?v=PjaF...ure=youtu.be&a

[Mirek]

I can't understand talking about torque and power separately. Torque on crankshaft is pointless as it can be compensated with higher revolution speed to generate certain power (my bike has cca 145 Nm torque at 30rpm). In the end, power is the thing, that moves things around.

With bigger restrictor you can have more air ie. can burn more fuel ie. more power. If it is done with less revs and bigger volume/rev. or more revs and smaller volume/rev. it is not that important.

Engune ability to pull from low revs... is very relative to what low revs are. Much more important is range of useable revs. to achieve required speed with limited number of gaears... But with modern fast shifting gearboxes, shifting while sliding in a corner, it can be compensated ass well.

Torque can't be compenstated by higher revolution speed because of air restrictor, boost limitation, rpm limitation and fixed gear ratios. The general shape of the power curve is basically given by the rules. We are not here in the ideal world where You can do whatever You want.

Also don't forget that higher rpm mean higher friction losses in the engine. The losses (and useless heat) grow exponentially with the rpm therefore it is vital to keep rpm as low as possible to have better efficiency (hence the torque importance again). The amount of air is limited by the restrictor after all and therefore all what You burn for generating friction is simply lost.

The ability to pull from lower rpm is also very important because You have plenty of hairpins where You accelerate from near zero speed. With fixed gear ratios the engine also rarely operates at the ideal peak power rpm therefore the torque is important. This could be very nicely illustrated on S2000 gear ratios which were very different for each car based mainly on the engine torque characteristics and the stages for which they were used. For example Škoda was able to use longer gearbox (higher top speed) than others because it had better torque characteristics and therefore could have larger steps between the gears.

In the end the maximum power of all cars is similar as it is achieved with same restrictor in very similar rpm but the difference comes from the torque. The old 2.0 WRC cars with very high boost had plenty of torque, way more than current WRC cars. They had so much torque that they could theoretically run effectively with only 4-speed gearboxes without loosing top speed. Teams kept using 5-6-speed gearboxes only for the reliability (to have smaller shocks when shifting). 2017 WRC have more power but the torque is relatively low therefore they don't have this luxury of very large power bent.

[dimviii]

Latvala day3
https://youtu.be/xow5rtFEsOE

[Mirek]

You've been saying that since day 1, still the testing (videos+drivers remarks) have proved otherwise.

Has it? I don't see that. I can see big difference in cornering speed but not more sliding. From Monte Carlo testing the by far most sideways-style video was the one of Tidemand with R5...

[Lundefaret]

Torque can't be compenstated by higher revolution speed because of air restrictor, boost limitation, rpm limitation and fixed gear ratios. The general shape of the power curve is basically given by the rules. We are not here in the ideal world where You can do whatever You want.

Also don't forget that higher rpm mean higher friction losses in the engine. The losses (and useless heat) grow exponentially with the rpm therefore it is vital to keep rpm as low as possible to have better efficiency (hence the torque importance again). The amount of air is limited by the restrictor after all and therefore all what You burn for generating friction is simply lost.

The ability to pull from lower rpm is also very important because You have plenty of hairpins where You accelerate from near zero speed. With fixed gear ratios the engine also rarely operates at the ideal peak power rpm therefore the torque is important. This could be very nicely illustrated on S2000 gear ratios which were very different for each car based mainly on the engine torque characteristics and the stages for which they were used. For example Škoda was able to use longer gearbox (higher top speed) than others because it had better torque characteristics and therefore could have larger steps between the gears.

In the end the maximum power of all cars is similar as it is achieved with same restrictor in very similar rpm but the difference comes from the torque. The old 2.0 WRC cars with very high boost had plenty of torque, way more than current WRC cars. They had so much torque that they could theoretically run effectively with only 4-speed gearboxes without loosing top speed. Teams kept using 5-6-speed gearboxes only for the reliability (to have smaller shocks when shifting). 2017 WRC have more power but the torque is relatively low therefore they don't have this luxury of very large power bent.

Very good explanation, but I disagree with you on one thing, and thats regarding the number of ratios.

Theoretically - yes, the "wide" power band of the 2.0 WRC cars would allow for fewer ratios.
The thinking behind this was that they would change gear more seldom (gaining time), and that a lower number of ratios would decrease number of parts, and therefore number of parts that brake.

When Porsche went serious about using turbochargers in racing the 930 turbo was one of the first cars. On this car (even on the road model) they used only four ratios so they could make each gear strong enough to handle the torque and power.

But we know how the story went. The Peugeot-drivers struggled to find the right ratio, and was caught in either a gear to low, or a gear to high. This resulted in them not having a decrese in number of gear changes on a stage/on a rally, but a big increase.
I think it was as bad a 25% increase, or something in that region.
I was lucky enough to test a Citroën Xsara WRC (something I will bring into each discussion when I have the opertunity, hehe) and found the power band to be very much like a turbo diesel. Actually a lot like a VW pumpe duse Yes it had a lot of torque, but it definetly had a peak, which in reality was quite a narrow power band (as all highly tuned engines tend to have in some form or another.)

So your theory in regards to smaller shocks pr shifting isnt totally alligned with turbo/gearbox-history.
This is because a gear box has a certain physical size, and if you cram a lot of gears in there, the gears them selves will be smaller, thus more fragile.
With Porsche at Le Mans it was not that big a deal to have only four gears, because even tough the engine had a very strong ketchup effect/turbo lag, and that you went in and out of boost, the power advantage was so huge that you made up for it anyway. In rallying it was a different story.

But regarding the torque, the teams with a good torque curve (in combination with good top end power) will off cource have an advantage. And sensitive drivers - like Ogier - will know how to take advantage of that.

[Mirek]

Thanks for Your insight. Very interesting but I am not fully convinced I admit I don't know the power curve of Xsara but as far as I know Citroën used 6-speed gearbox for late Xsaras and C4 only becaue it was very realiable.

I have seen dyno charts of other cars and some really had very large power bent. I have in front of me very old chart from Fabia WRC 04 (the initial very bad engine with Bosch electronics) and the peak power is near constant in the range 4200-5700 rpm for one of the worst engines in the WRC history with roughly 200 Nm of torque less than the competitors. If I can pick also R5 engine as an example I know that Fiesta R5 has nearly flat power curve all the way from 4500 rpm to the rpm limiter at 7500 rpm.

I tend to disagree about the gearbox design. I don't think that it's a good idea to have more robust gears to cope with the shocks. It's rotating masses whose inertia shall be kept as small as possible to save power.

Anyway I'm no gearbox designer therefore what I write may be a bullshit after all.

[AMSS]

Latvala day3
https://youtu.be/xow5rtFEsOE

I have been among the criticals regarding this project but I have to admit it's looking better and better all the time. Still something strange in front handling and suspension but at least now they are at a point they're not visibly alot slower than others(in my opinion at least) and this would be a good thing!

[macebig]

Thanks for Your insight. Very interesting but I am not fully convinced I admit I don't know the power curve of Xsara but as far as I know Citroën used 6-speed gearbox for late Xsaras and C4 only becaue it was very realiable.

I have seen dyno charts of other cars and some really had very large power bent. I have in front of me very old chart from Fabia WRC 04 (the initial very bad engine with Bosch electronics) and the peak power is near constant in the range 4200-5700 rpm for one of the worst engines in the WRC history with roughly 200 Nm of torque less than the competitors. If I can pick also R5 engine as an example I know that Fiesta R5 has nearly flat power curve all the way from 4500 rpm to the rpm limiter at 7500 rpm.

I tend to disagree about the gearbox design. I don't think that it's a good idea to have more robust gears to cope with the shocks. It's rotating masses whose inertia shall be kept as small as possible to save power.

Anyway I'm no gearbox designer therefore what I write may be a bullshit after all.

4 speed in a 2.0 liter WRC?Gronholm has some words to say about that...And they are mostly 4 lettered...