Does short shifting affect your lap times? If so, then by how much and how can you spot this in the data?

Here is how you can quantify your gear changes effects on your lap time – and make sure you’re changing gear at the right time on track. This article also includes a link to a done-for-you spreadsheet, and a custom visualisation technique to help you see this easily in your data. Read on…

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When Is The Right Time To Shift Gear?

There’s a tension here.

No one wants to over-rev their engine and cause damage.

Equally, you don’t want to lose out by not using all the accelerative (if that is a word!) power that you have available.

Short shifting is a common practice, especially after standing starts, in the wet, but also to save your engine.

As with everything in motorsports, this is another situation where you are being asked to make a compromise.

So what is for the best?

Paddock Folklore Discussions

If you’ve ever been unsure about whether you are doing the right thing, you may have found yourself in what I call a “paddock folklore” discussion.

One knowledgeable and experienced person is saying one thing, another similar person, saying something quite different.

What should you believe?

The Value of Data in Motorsports

One of the biggest values of data – for me – is being able to try and quantify what those compromises are.

Sometimes compromises are significant in terms of your lap times. Other times they are not.

Often, determining the significance of one approach versus another is not always easy or intuitive.

Therefore, if you know where to look, this is where data can help you.

Motorsports Data Analysis Course

As readers have started to complete my motorsports data analysis fundamentals course, a few clarifying questions naturally get asked.

One, thanks to Hank, has come up regarding my assessment in the Pro v Am Masterclass.

Specifically to do with gear selection and a short shifting affect that was seen in Scotts lap times.

Case Study: Pro v Am Fastest Lap Analysis

Spoiler alert: There is one part of the lap where I’m faster than the pro driver (Scott Mansell of Driver61 fame) who was racing my car.

It is sadly, but not surprisingly, only fleeting, but I’ll take it.

In the part of the lap in question, my analysis shows that I benefit from driving a slow corner onto a long straight in second gear, rather than the third gear Scott uses,

Whilst this is true, only part of my advantage comes from this.

The other (thanks Hank!) is that Scott loses out by short shifting from third to 4th – saving my engine, but costing him lap time.

The Data

This chart show the data. You have the speed traces for the two laps (middle). The time gained and lost relative to one another (bottom). You also have the engine RPM (top) – that Hank hasn’t seen before, but which confirms his observation:

Short Shifting affect on lap time
Short Shifting affect on lap time (You might need to zoom in!)

Scott shifts gear from 3rd to 4th at about 6500 rpm. I shift about 7400 rpm.

Whilst I do gain about 0.22 seconds from running the slow corner in second rather than 3rd, I gain a further 0.44 secs of lap time, simply by changing from 3rd to 4th a few rpm later.

Wow.

If someone simply said to you: “Here, have 0.5 seconds of free lap time gain simply by changing gear there, instead of where you are” I’m sure you would be enthusiastically saying:

“Yes please!”

The Importance of Changing Gear – at Exactly The Right Time

The length of the straight here – the longest I believe in the UK – also contributes to the amount of time I gain in this section.

But for me, it just goes to show the importance of changing gear at exactly the right time.

Should you run every gear to the red line then?

Well no!

You can actually work out an “ideal” gear change rpm – up, and often more critically, down – with a few basic car parameters and a bit of maths.

Read about how you work it out here, and grab the spreadsheet I made to help you if you don’t fancy doing all the maths.

Easy Laptime Win: Be in the Right Gear

The message is that what with all the braking technique, car positioning, throttle application etc. putting in competitive lap times is hard enough.

One of the easiest lap time wins is to make sure you’re always in the right gear.

Running the calc’s will show you that there is always only one ideal gear to be in for maximum acceleration, at any given road speed.

You can even go a step further.

You don’t need to be as eagle-eyed as Hank every time, you can actually get your data system working harder for you.

This is what I call a gear ratio map, and it shows you the ideal gear to be in at every part of the track:

Gear ratio map

Get Your Data Serving You!

In this case, use your data to help you quickly identify short shifting affects and quantifying any lap time compromise.

Got a short quali session? – then make sure you use all the revs at the right time.

Got a long race or test session? – Then know what lap time effect short shifting to protect your engine is having.

Everything here is just to help you more easily compare yourself with the “ideal” all around the lap.

Thanks to Hank, we now have more information from this data.

What else to do see? Be sure to sign up below and let me know.

 

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