cgh1

I got a great email from someone today who, since he's part of the crew for many events rarely, if ever gets to sit in on my classrooms when we're working the same event. His question revolves around a topic that is surprising for some, so I thought I'd share the conversation here. Of course it's been edited for privacy and brevity but here goes:

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Chuck,

Technical discussion for you - if you want to charge me, put it on Morris' bill!

Some time over the past couple of years, I remember someone telling us in a classroom environment (ala THSCC) that we should never be "coasting" while on track at speed. We should always strive to either be on the gas, on the brake or maintenance throttling. The reasoning was to always be in control of the car. If I remember correctly, the topic came up in conjunction with downshifting and that you should be never be "out of gear" any longer than necessary. I do not recall if the lesson came from you, Peter or Ron but I am thinking it was Peter.

I was watching the Australian V8 Supercar race tonight (recorded) and they were showing the view from a footwork camera of Greg Murphy (I think that was his name). At the same time, they were showing an inset camera shot of the car going around the track. This was at the 35 minute mark if you recorded it.

What caught my eye is the amount of coasting he was allowing the car to do from turn-in to apex and maybe even later. He was trail braking some, but there were definite times in which his feet appeared to be fully off the brake and not on the accelerator while the car was going from the end of braking until mid-corner.

Besides "letting the car settle" or something of that nature, what are your thoughts on this? I have no idea if he was having handling issues, saving the tires, saving fuel or saving the brakes, but the AV8SS runs sprints, so there isn't a lot of "saving" the car that I have seen.

I know from my recent Chump Car racing and from lapping in HPDEs, there have been times when I was running less than 100% and probably coasted the car at times just because there was no reason to go all out, but in a race would you not want to constantly maximize braking and acceleration?

-Kevin
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Great question, Kevin!
If you’d ever get time to come sit in my classrooms, you’d be familiar with my stance on this topic. But thankfully for the participants, you’re busy getting it done for them.

At any rate, to make this as short as possible:
1. There’s a misnomer / misunderstanding on what ‘coasting’ is. In racing/perf driving, the definition is not necessarily equal to foot completely off the throttle (that’s engine braking.) Maintenance throttle may actually be closer – BUT, that doesn’t mean that certain situations mean “maintenance throttle” really means no throttle at all – foot not touching the pedal.

2. In order for us to allocate 100% of traction to steering, which we need to at some point in almost every turn taken at the limit of traction (and intentionally living there for the duration of the turn), we cannot allocate ANY to braking or acceleration – thus we MUST coast. Again, coasting usually does not mean decelerate by coming totally off throttle – it means leave the throttle where it is; don’t add or subtract. This leaves the car in a balanced state.

3. In the video (which I have not seen… yet if at all), my guess is Murph is either hustling the car into turns where he actually needs the slight bias to front weight of engine braking OR he’s just not adjusting his driving style even though he ‘feels’ as though he’s taking the turn too fast – thus a full lift. In either case, that may be exactly what the car needs to get through the turn optimally. There are several times per lap just about anywhere where I’ll be lazy on the throttle to allow that foot-off coasting to either compensate for a mistake I’ve made or simply comply to what the car needs in that particular section.

4. Those who state confidently that we should always be applying brake or throttle, never to coast either by 'maintenance throttle' or do a full lift & roll either have not thought about or understand or consider the 100% rule (100% of traction is all we get and WE have to divide that between steering, throttle, and braking); OR, as in many cases – they actually do coast and don’t know it or think it unwise to admit it. Data analysis usually quells their denial of such – often to their surprise. LOL Also as stated, the misnomer of coasting not being maintenance throttle - semantics in play here.

The short of it is, in order to be the fastest we can be and get to the absolute limit of traction and then live there for entire laps on a course with turns, we MUST coast – even if only for a millisecond – at some, if not many points on said lap. I love this because one of the questions I ask the class in many of my classrooms is “Do race drivers ever coast?” And of course the majority of the heads in the room are shaking a “no." Once I explain what coasting really is and why we need it, light bulbs come on everywhere.

Chuck
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Love to hear others' thoughts on this (If you have direct questions/comments specifically for me, please note I'm on the road through July and may not be able to check in all that often but will when I can.)

Floor's open...

SouthernSon

Excellent post! Never say never. Everything is equivocable to some extent.

mashinter

At the recent Long Beach race, they showed a driver "coasting" at the end of the front straight to save fuel.

mgarfias

Might do it to save the tires too.

davidfarmer

let me add a further not. I'm pretty strict about NOT coasting specifically in street cars, as our Corvettes are nose heavy and not only don't create downforce, but create lift at speed. Bottom line, this makes are cars MOST STABLE at light throttle, and MOST INSTABLE under deceleration while turning. While coasting certainly is appropriate at times, just like trail braking, both practices get novices in trouble all the time.

So in addition to "braking in a straight line" for instance, one of my rigorous sermons is about coasting. It's not about the coasting itself, but the simple fact that the car is more stable under maintenance throttle. I drive, and ask my students to, immediately get their foot back on the throttle (even 1%) as soon as they complete their braking.

btw, watching TV can get you into trouble! F1 cars trail-brake every turn, Rolex cars were driving all sorts of crazy lines at 5a and 7 (VIR) this weekend, etc. Balanced cars, aero cars, and experienced drivers' don't follow the same rules that we teach folks learning out.

It is much safer for an advanced driver to learn where they can break the rules and go faster than to allow a novice to get away with bad habits and get hurt.

brkntrxn

Good discussion, especially since it was my question. David had probably already figured this out.

Since Chuck is hitting the road, I will post my email reply back to him to further the discussion here.


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Chuck, thanks for the response.

Your explanation makes perfect sense to me. He (the AV8SS driver) may have been in effect engine braking and that had not occurred to me. For all I know, he may have been saving his brakes and was using engine braking to do so.

I truly enjoy the 100% topic because it is technical and makes you think about what you are doing. And to your point, maintenance throttle is probably much closer to "coasting" than foot off the throttle. Especially if you have a large engine or high compression or low gearing that provides some measure of engine braking.

Thanks again for the enlightenment. Alwasy appreciated!!!

Have fun on your trip(s),


-Kevin

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davidfarmer

Yes Kevin, I should have posted something like "what kind of idiot would post such a stupid question"

anyway, engine braking can be trouble also, since you are basically braking with just the rear tires, which in the case of the street vette is a bad idea, unloading the light end and coasting is asking for a spin. Rules are meant to have exceptions though. Sorry for the run on sentence but I'm on my phone eating at mcdonalds

63Corvette

Good response Chuck. In that same vein...................what do you think (professionaly) about "blipping the throttle" (in gear) to alter the stance of the car. I see professional drivers (say Ronnie Peterson was the poster boy for this) using strong throttle on/off input for some reason (induced under/oversteer???)? I know some "dab: the brake to "settle" the nose, but I would like a pro to discuss the merits of "stabbing" the throttle.

Thanks,

davidfarmer

I can't speak for Chuck, but while we preach smooth steady throttle application throughout a corner into the straight, reality doesn't always allow it. If you have a car that tends to understeer, you want to apply throttle, but it simply wont turn.

I don't like my cars set up that way, but I specifically remember racing at Rd America where the car just wouldn't turn, and I used (tried to anywa) the throttle at the carousel to to try and rotate the car. The front tires were out of grip, and the rear tires simply wouldn't break free, and the car just plowed. In that case, a little man-handling was needed to rotate the car.

I don't consider this the appropriate way to drive in most circumstances, but you do what you must....

brkntrxn

I agree in not using engine braking (not intentionally anyway, at least not on a "hot" lap) as brake pads are cheaper than an engine. I rarely do this unless for some specific reason.

To Garrett's question, I used to "blip/stab" the throttle of my 99 Cobra to get it to rotate. A Mustang is inherently set up from the factory with a great amount of understeer and it takes a lot to remove it. Although I ran a square 275 setup on the car and had PLENTY of power, I often had to make it turn. That included using the brake and/or throttle. Since moving to the Z06 platform, I find very little need to do this as the Z06 is much better balanced and does not need the manhandling.

Quick story on that one. Last Fall I was at CMP at my first event with the Z06. The first session out I was driving like crap. The second session out I got a buddy to jump in the car with me and figure out what I was doing. I did about three laps and he says, "Hey dumbass, quit driving this thing like a Cobra! Go back to the basics, learn the characteristics of the car, and then build back up to your speeds." Later that weekend I set a new personal best in Time Trials, LOL.


-Kevin

SouthernSon

David, this sounds like you were exceeding the slip angle of the front tires and applied throttle to correct?? I know this can't be what you meant. I lost you on this one.....

davidfarmer

when you are at full understeer, steering angle doesn't do anything. So "exceeding" isn't really relevant, as it's the same as ideal. What I'm saying is that while applying light throttle would just push you off the track, alternating between lifting and jamming' the throttle would help give a bit of rotation. It was NOT a fun race, and I made some major changes afterward, and I'm not sure it was any more effecting than just plowing around the corner, but sometimes just doing something seems more effective than doing nothing.

I was following Derek Bell in an AWD Audi at the time, and was really pissed that he just drove away from me mid-corner!