HELP: Audi TT Cup understeer

RasmusP · Jun 30, 2017

Hi,
as you all can see we had some good discussions going on in the last days and the consensus was something like "Let's have a place to talk about the driving".

So here I am, creating the first of that threads:
I need some advice on fighting the understeer in the Audi TT cup

When I watch the replays I see that "the fast guys" are having a better line and when I compare it to me in detail I see they are faster while cornering, turning in point + braking is almost the same and I see no clear difference.
It's like some "magic" that pushes them tighter around.

But then sometimes I get that too... Just don't know how to do it consistently

My thoughts: when you brake you will gain grip on the front wheels. So touching the brakes slightly while cornering will give you a tighter turning radius but will also slow you down. If you brake too hard you will transfer too much weight to the front and you will get understeer.
If you accelerate you will get understeer because the front wheels lose weight and therefore grip.
If you accelerate too much you will get HEAVY understeer, because FWD...

So somewhere in between there seems to be a "trick" that lets you do the "tighter turning radius" you get when touching the brakes, but without braking and without slowing down.

Can you help out? Do I have to turn the wheel more aggressively or trail brake deeper into the corner? I don't know and before I'm spending a few hours on doing a splitscreen slow motion video, studying the details etc. (maybe I will do that either way) I just thought about asking you all and start a nice discussion about the handling of our beloved (and sometimes hated) friendly event car

Brandon Wright · Jul 5, 2017

Neilski said:
That looks like an interesting video - I must watch some more of it.
I think though that you misunderstood me - I was talking about the speed gap, not the time gap. The latter will indeed increase, but the former will decrease because the car's acceleration decreases as speed increases. (That section of the Skip Barber video says nothing about how the speed changes between start and end of the straight.) NB: I'm talking about the apples-vs-apples comparison of looking at the speeds of both cars at fixed marker points on the track.
The pic below is from a test-track run of a TT Cup, and you can immediately see how the slope of the speed curve is steadily reducing as the speed builds.
View attachment 199945

Yes, but if Car A gets on the throttle 20 meters sooner than Car B he is going to be at a different point on that curve by the time they get to the braking point. I get what you're saying, there is a point where the gap will start to decrease and on very long straights where the cars get close to topping out that may be a factor but on most straights it won't be much of an issue and most of the time checking top speeds at or near the end of a straight is a valid way to determine if the other car got a better exit. On most tracks there's a whole lot of time to be found by optimizing your exits.

Kek700 · Jul 5, 2017

I do understand what you are saying Brandon, i realise i can in this circumstance only deal with a certain amount of information.
Most of the time i have a 3 or 4 kmh advantage, as a minimum speed, the other driver will need to gain
that and while he is gaining this i am adding to it, my exit speed is usually higher too.
It may seem that i am disagreeing, but i am not, i need to find the exact reason so that i know what to address.
You need to address the correct reason.

Brandon Wright · Jul 5, 2017

Kek700 said:
I do understand what you are saying Brandon, i realise i can in this circumstance only deal with a certain amount of information.
Most of the time i have a 3 or 4 kmh advantage, as a minimum speed, the other driver will need to gain
that and while he is gaining this i am adding to it, my exit speed is usually higher too.
It may seem that i am disagreeing, but i am not, i need to find the exact reason so that i know what to address.
You need to address the correct reason.

No worries, we're splitting hairs anyway and the fact remains that he who gets on the throttle sooner and has a better exit will have a higher speed/lower time down the straight.

RasmusP · Jul 5, 2017

For the Video I wanted to do:
I deleted most of my replays, missclicked and it's gone... If someone could send it to me I would still do it!

"back to topic": I tried to do everything that was said in this thread and I got 3rd today! Switched TC off (vallelunga has serious hairpins and TC slows down in them!), modulated the brakes and throttle like my life would've been dependin on it etc.
I was actually a lot faster!

Thank you guys!

Neilski · Jul 5, 2017

Kek700 said:
SF 162..........154
SHS. 204..... 195
MES. 213.... 210
MCS. 71...... 58
MES. 116......109
MCS. 105.......104

This really baffled me so I had a look at my own replay (the race was 28/06/17 btw, not 30th

).
I get very different numbers when I compare your final lap with that of the leader.
For SF I get 155 for both of you (vs. your 162/154)
For MCS on the first turn, I get 61/59 (vs. your 71/58)
For MCS on the second turn, I get 99/104 (vs. your 105/104).
Not sure what could cause this. Doesn't really seem like lag could do it. I'm taking the speeds from the built-in apps (both the Essentials app and the Gears app show the same speeds). Maybe you used an app which doesn't play nicely with replays?
I stopped comparing after the first few corners, as the figures were so different.

BhZ · Jul 5, 2017

Guys, i haven't followed every single comment here, but the impression is that you went a bit the wrong way. Yes, speed is important and the difference in speed can tell you something, but it's not always the case. When you are on track there are 2 kind of situations: the one where you need to carry as much speed as possible and the one where you can sacrifice speed and take the shortest way. It's the combination of speed and meters crossed that define a laptime.

Neilski · Jul 5, 2017

Brandon Wright said:
Yes, but

Oh my goodness, are you still disagreeing with me?

if Car A gets on the throttle 20 meters sooner than Car B he is going to be at a different point on that curve by the time they get to the braking point. I get what you're saying, there is a point where the gap will start to decrease and on very long straights where the cars get close to topping out that may be a factor but on most straights it won't be much of an issue and most of the time checking top speeds at or near the end of a straight is a valid way to determine if the other car got a better exit. On most tracks there's a whole lot of time to be found by optimizing your exits.

Yup, I'd go so far as to say there is always a lot of time to be found by optimising the exits - we aren't disagreeing about that. But when you say "there's a point where the gap will start to decrease" I have to differ - the speed gap is always decreasing, from the moment they both get their pedals to the floor.
Maybe a better way to think of it is like this: if you compare speeds at the end of the straight, and then work backwards say 400 metres, you will always find that the quicker car gained less speed over that 400 metres than the slower car, and thus that the speed differential shrank.
To help visualise what I'm saying, here's a graph of the speed of the TT Cup plotted against distance travelled. As can be seen, it flattens off even more aggressively than the speed vs. time curve.
I've added green and cyan markers to denote the faster and slower driver - the green guy finishes the straight faster than the cyan guy. If you work back a few hundred metres (in fact I think I went back around 800 metres in this example, but the key point is that it's the same distance for both drivers) you can see that the speed differential between the two drivers is much bigger at the earlier position (i.e. distance between the skinny black lines). The reason this matters (cos yeah it's somewhat splitting hairs

)? Well I'd say it's mostly that after a long straight the speed differential can be reduced by so much that it's hard to measure it, but shortly after exit it's at its maximum value and much more obvious.

BhZ said:
It's the combination of speed and meters crossed that define a laptime.

Indeed. I suspect this partly explains Ernie's conundrum.

BhZ · Jul 6, 2017

Neilski said:
Indeed. I suspect this partly explains Ernie's conundrum.

Yeah, you either use the full telemetry or simply ignore that kind of data.

Kek700 · Jul 6, 2017

Neil

Your absolutly correct, must have got date wrong, probably looking at mazda date.

It refered to lorcan ,if I remember his name correctly, you were right behind him, and it
was definatly the last lap.

I looked at the cars speedo's and obviously could not account fo P2P, but that is really
Irreverent to the point. ( maybe )

I think that "BhZ" has a very good point.

When i get back to my rig next week i will check again but i am pretty sure the data i presented was
Correct.

Nice talking to a another baffled person

RasmusP · Jul 6, 2017

@Kek700 that was 100% the Audi TT, checked the entry list

So last lap of the Audi TT event and I deleted my replay.. wow...
Can somebody upload it?

Kek700 · Jul 6, 2017

Neil, i used the speedo in the car , this was, i thought the most direct from the software point
of view; no third party app.

Kek700 · Jul 6, 2017

BhZ said:
one where you can sacrifice speed and take the shortest way. It's the combination of speed and meters crossed that define a laptime.

A bit off topic, as with the data i put in this discussion , i also spent quite a few hours last week slow motioning ( not sure such a word exists ) the mazda from last friday with the same type of results
with respect to speed.

But i did find 3 distinct differences between my lap and the fast guy.

I have not really put the same effort in with the audi TT Cup

That being exactly what BhZ said above a complete loss of speed to get the shortest route
between both corners.

Unfortunately as much as i would like to, at my age i have to surrender to the difficulty of
of me actually achieving this and my persuit is one of knowledge not really aplication.

Neilski · Jul 6, 2017

RasmusP said:
@Kek700 that was 100% the Audi TT, checked the entry list
So last lap of the Audi TT event and I deleted my replay.. wow...
Can somebody upload it?

I only have partial replays of each event cos my size limit is not very high (not certain I really want to fix that but sometimes I wish I had

). So I can share a partial file with you if that's of any help? Which event did you want?

Brandon Wright · Jul 6, 2017

Neilski said:
I only have partial replays of each event cos my size limit is not very high (not certain I really want to fix that but sometimes I wish I had ). So I can share a partial file with you if that's of any help? Which event did you want?

Turn your replay quality down. The quality doesn't really take a big hit by turning it down but it reduces the file size quite a bit.

Neilski · Jul 6, 2017

Yeah I think I turned it down already - IIRC I'm using "medium" now but I can't recall what the default was. My partial replays are around 180MB for something like 20-25 minutes, so I lose the start and first couple of laps of our 30 minutes races :-S

Brandon Wright · Jul 6, 2017

Neilski said:
Yeah I think I turned it down already - IIRC I'm using "medium" now but I can't recall what the default was. My partial replays are around 180MB for something like 20-25 minutes, so I lose the start and first couple of laps of our 30 minutes races :-S

Strange. When I ran it on full quality I would get 20-25 minutes but by turning the quality down a notch or two I was able to capture the entire 30 minute race.