Renault's great starts

[hardingfv32]

1) Is the KERS throttled when in use or is it 100% output when switched on? If it is always 100%, then would it be wise to start the race with it on and control wheel spin with the engine throttle?

2) Could Renault be forgoing off throttle fuel burning and starting with less fuel load/weight?

Brian

[strad]

I don't know but when you can drop the hammer at 13,000 RPM and not get wheel spin, I don't care what ya call it...It's launch control.

[Caito]

Could you have a "launch control" with kers maybe.

They launch with kers, probably not even launch control. I don't know if 80hp will spin those big wheels. And as soon as you get going you release te clutch and kaboom, you started 4th and arrived to the first corner 2nd.

[Fil]

1) KERS output can be adjusted by the driver. The steering wheels have dials specifically for this purpose.

2) Most definitely not. The Renault has the most aggressive off-throttle overrun in the field.

Forget the sanitised sound you hear on TV, have a listen here - Sound comparison (Renault at 0:35).

[greencow]

1) Is the KERS throttled when in use or is it 100% output when switched on? If it is always 100%, then would it be wise to start the race with it on and control wheel spin with the engine throttle?

KERS doesn't kick in until 100kph? Should they be out of wheelspin domain by then?

2) Could Renault be forgoing off throttle fuel burning and starting with less fuel load/weight?

http://www.racecar-engineering.com/news ... more-fuel/

I think this is off-throttle blowing rather than extra losses from the tortuous layout. But it's certainly a no. There's no (very limited) opportunity for rearward weight bias relative to the opposition - all the talk is of "clutch strategies".

[Caito]

KERS kicks in whenever you want. There's no 100kpb limit.

[Sayshina]

1) Is the KERS throttled when in use or is it 100% output when switched on? If it is always 100%, then would it be wise to start the race with it on and control wheel spin with the engine throttle?

2) Could Renault be forgoing off throttle fuel burning and starting with less fuel load/weight?

Brian

The answer to 1 is a flat no. Race engines spend the majority of their time at either 100% or 0% throttle, and because of this are naturally optimised for those states. Launching the car requires part throttle, or transient response, an area of performance that is often neglected and very hard to tune for without hurting your top end.

So the goal is to get out of that part throttle area and into full throttle as soon as possible. Using kers to help launch would only prolong the time you were forced to spend at part throttle. This would not only hurt your launch from the engine standpoint, but since there is a hard limit of 6 seconds use on kers it would hurt you again once you got going and no longer had kers.

Caito, there is no 100 kph limit on kers, but you'd never want to use it before you became traction limited. 100 kph is the generally accepted speed at which F1 aero starts to work. It's a debatable figure, and I've also heard the cars go from traction limited to hp limited 2/3 of the way through 2nd gear.

At any rate, you'd never want to use kers before you became hp limited, and you'd want to use it as soon as you did become traction limited, as extra power helps you far more at the begining of the straight than at the end.

As for part 2: Since the Renault engine is considered to be the most fuel efficient on the grid, it would seem they could run with lighter fuel, but indications are they don't.

[Caito]

The thing is that if you get a way to "traction control" with kers. You can start with kers. Ideally, yes, the combination would be slower.

But, as you say, since you neglect the transient response it could be better.

[hardingfv32]

Steve Matchett stated during the Chinese GP that there is no KERS under 100 km/h. They were showing a in-car replay of the start highlighting the KERS display.

Brian

[Richard]

Steve Matchett stated during the Chinese GP that there is no KERS under 100 km/h. They were showing a in-car replay of the start highlighting the KERS display.

That's due to the limitations of physics (ie grip) and strategy (ie most efficient use of the KERS quota).

[Sayshina]

First post.

Based on what Sayshina has said about racing engines being on/off beasts, would be it be possible to only use 4 cylinders at the start and mash the throttle? In China Q2 Brundle said that the cars in the line-up could be on four or even two cylinders for cooling purposes.

Hmm, would it be possible to set up the ECU to do it? Certainly. But while engine maps are switchable by the driver on the fly, they're not free to switch however and whenever they please.

Would it be reliable? Yeah, probably. That's more or less how traction control worked anyway. You might run into a problem shutting off particular cylinders for longer than you ever did under traction control, but I'd bet that would be fairly easy to solve.

Would it be possible to hide doing this? Not a chance. The ECU tracks this sort of thing, and I'd be very surprised if the FIA didn't rule it cheating. And they check regularly.

Also, I think I've exagerated things a bit. Race engines really do tend to be sortof beast-like, but they're not all THAT bad. Well, not usually. You do care about transients, it's just that it's so incredibly hard to make a nice, docile engine with a wide powerband that also has great top end.

Peak power is critical, transient response is nice if you can get it.

Harding, if you're implying he said that was by rule, I'd ask you to remember that comentators are rarely any sort of expert. As far as I know, there is no such rule concerning kers use. However, there's also no good reason to use it when you're already traction limited, which the cars would certainly be at 100kph.

Caito, how would you go about making kers work as traction control? I mean how would you get away with it? You could theoretically do it with uncontroled dual torque kers, but not with heavily restricted and routinely checked push to pass kers. What we have today is the latter.

[Just_a_fan]

First post.

Based on what Sayshina has said about racing engines being on/off beasts, would be it be possible to only use 4 cylinders at the start and mash the throttle? In China Q2 Brundle said that the cars in the line-up could be on four or even two cylinders for cooling purposes.

There's no reason why you couldn't do that except the rules require that the settings used at the start are used throughout the first lap (I think). So you'd get a good start and then be left behind over the rest of the lap.

As for KERS off the line, no, the rules don't allow it below 100kph off the line, presumably for this very reason - it would be the perfect launch system.

[Richard]

As for KERS off the line, no, the rules don't allow it below 100kph off the line.

Are you sure? Could you show us which rule please?

[strad]

As for KERS off the line, no, the rules don't allow it below 100kph off the line.

Are you sure? Could you show us which rule please?

ya know...I have heard about the 100kph limit many times,,,but I can't find it in the rules....Anybody?

[Giblet]

There is no rule AFAIK, it is just generally known and has been discussed here that the cars are traction limited until ~100km/h.

Since all the teams have worked out the maxiumum places to use KERS while lapping, you won't see people wasting the 80hp to simply have to feather the throttle more to keep the wheels from lighting up.