T(h)or's GT86 hammer (Europe) - essential track setup

[Tor]

I have a few updates:

Some may have noticed my annoying questions in the tuning forum. Especially thanks to @Wayno , who not only suggested me to get a Tactrix OBD2 adapter and flash a tune myself, but also answered a lot of questions.



For those who doesn't know anything about ECU tuning (which I didn't a 2 weeks ago either), it's not hard to flash the ECU yourself at all. It takes some time to get a grasp on the concepts though. What I flashed is Wayno's Stage 1 (stock car) tune v. 108.2. So far I didn't get to drive it a lot, because my brakes were/are shot, but did get to do a few logs.

To illustrate one of the many differences a tune makes, here are two screenshots of a logfile showing timing vs. rpm. The green lines are 5000 and 7000 rpm reference lines, gray is rpm, purple timing:

Stock tune:



Wayno's 108. tune:



Besides from the obvious difference in the curves, notice the difference at max rpm. Stock tune the rpm are jittery, which is hitting the rev limiter. The sharp rise in timing, is me letting off the throttle.

Stock the ECU will cut the fuel at 7450 rpm, when the rpm drop to 7100 the ECU opens for the fuel again. That leeds to the very annoying and abrupt braking feeling when hitting the rev limiter.

On most customised tunes it will look like the curve in Wayno's 108.2 tune. The actual rev limiter has been risen to 7600 rpm, but as you can see in the timing curve, a lot of timing is being removed from 7450 rpm (the big dip). Because of the timing dropping off, it just feels like you can't push through. If you do so anyway by being persistent, the fuel with be cut at 7600 rpm, but not with the on/off feel of the stock tune, because the power has already tapered off. Already at 7550 rpm the ECU opens for the fuel again. But it throws you back down into the "dead" power band between 7450 and 7600.

All together, the rev limiter is very soft and noticeable without being annoying. And the car is actually drivable in that area if needed for a shot while - like between two curves where an upshift doesn't pay off.

Just a feature like this alone makes it all worth it.


Here another two curves for illustration showing variable intake valve timing (the additional first green line is 4000 rpm):

Stock tune:



Wayno's 108. tune:



This, from my understanding, is to help reduce the torque dip. Funny thing is that you hear it very noticeably. At exactly 4000 rpm the intake/valve noise has a very aggressive grrrr to it.

So for those (like me 2 weeks ago) who think of tuning like black magic, the changes are very real and visible if you look at the logs.

Next up for me is to flash a map with more aggressive timing, as I have no knock.

But first...

New brakes:



My XP10 pads arrived from Carbotech Europe. Look at those beauties!

I probably feel the same as when a woman sees this:





To compliment them I got the 2005 Subaru Impressa WRX Brembo discs. They are 2.8 lbs lighter (when both new) than the stock discs. They cost the same.

Scale shows metric kg.


Looking on the back side you'll find the reason:

Stock disc 2.5 inch (6.4 cm):



WRX disc 2.1 inch (5.4 cm):



Insider info say that the WRX discs has better heat treatment. The lack of 0.4 inch (rusty part) seems to enable more air to flow for cooling too.


I didn't want to remove my dust shields, for more reasons. They are just as much there to protect the discs from road dirt. I think they keep the airflow more controlled and lastly I don't want a 900 degree F piece of metal radiating heat directly onto my damper.

Instead I trimmed off the corners blocking the flow from my Porsche brake guides:






I wanted to do the bedding of the brakes tonight, but once I drove off, my rear brakes were making noises as if the wear indicators were touching the discs! I probably could distinguish the noises with the old brakes up front.

I do have new XP10 pads (as you can see in the pic), but I am waiting for the rear discs to arrive. This brake story is never ending.

[Guillaume]

Congrats We now have a very similar brake set up. It's been bullet proof for me!

[Tor]

I got to do 5 laps on the Nürburgring GP yesterday (3 timed). Lots of visitors and traffic and 2 accidents, 1 bike and later 1 Lotus Elise (no one seriously hurt). So it was cut short at those 5 laps.

I managed to get the brakes hot enough, that I would think the bed in for the fronts is more or less okay. Another session probably won't hurt so now I have a good reason to go next week too.

In the meantime I'll install the rears. As I probably need to be more brutal to get the rears up to temperature next time, it's probably not too bad that the fronts already had one go.

@Guillaume , are your rotors getting the same coloration too?

[Guillaume]

Originally Posted by Tor

@Guillaume , are your rotors getting the same coloration too?

Yep, typical Carbotech blueish dark shade.

[Tor]

Originally Posted by Guillaume

Yep, typical Carbotech blueish dark shade.

I rather meant the golden look where the rotor meet up with the hat?


I got the rears installed too. To make them less flashy (given they don't have ECE90 approval), I gave the backplates a couple of coats heat resistant black paint.





On track, I didn't really get an opinion of them, because of the bedding they felt a bit inconsistent. And/or a combination of me getting used to them.

After I installed the rears I have been driving a bit more. And I have to say (with my limited experience): The bite is amazing! A significant difference to the RC5+ and different universe compared to the stock pads.

You get what you demand without delay. Medium press on the pedal, and there is instant medium braking effect. Even with harder braking, there is not a feeling the brakes have to "ramp up". Harder braking also feels like it doesn't require as much pedal force, but still in between there is a linear feel pedal force vs. braking effect.

A high priority for me is durability. Will be interesting to see how they will hold up. I think I have to go to Zolder in August and check it out.

-------


As I had the rear off the ground I decided to set my rear anti swaybar to hard.

I didn't upload any video from last time on Nürburgring GP because it's boring to watch as I was fighting with massive understeer. A short example in low quality (due to the time it takes me to upload):

[ame="https://www.youtube.com/watch?v=vWZwAgnVRGg"]Understeer!! - YouTube[/ame]


Besides the brakes the only change I made since last time was to lower the tire pressure more than I did before. Not crazy much, actually it's probably still too high. Previously 2.1 bar semi-cold, this time 1.9.

My theory is:
With the lower pressure I think I heat up the front tires faster causing higher pressure in the front. It got worse and worse and I think it became self perpetuating, since I was sliding more and more over the front and probably heating them even more and more.

Afterwards I was more concerned about cooling the brakes, so I didn't check temperatures or pressures.

Anyway, even before, the understeer tendency was there. More noticeable on Nürburgring GP than on Zolder. The understeer is always on corner exits, when putting power down. On entry and mid corner under balanced power it's fine.

Driven on the street the rear now feels noticeably stiffer. I am very curious to see how much of an effect it has on track.

I think I have to go to the GP circuit again next week to test it out, and to bed my rear pads.

[ZionsWrath]

If you worried about paint just drive them hard the paint burns off. My XP10 turn white after tracking them.

[Tor]

Originally Posted by ZionsWrath

If you worried about paint just drive them hard the paint burns off. My XP10 turn white after tracking them.

I was unsure how hot the rears will get. The fronts I gave a very thin layer of ceramic paste, to bake on. They are grey now too, good to know they will change color without help. Thanks.

[Tor]

It was raining the last days, but I decided to go to Nürburgring Grand Prix circuit anyway.

[ame="https://www.youtube.com/watch?v=P8w3JDYh8Bk"]https://www.youtube.com/watch?v=P8w3JDYh8Bk[/ame]

It probably didn't do a whole lot for bedding the rears, since I doubt I got them up to proper temperature.

To be honest I couldn't feel much difference with the rear stabiliser set to hard. It still understeers mid corner. Turn in is fine and there is maybe an improvement on corner exit, but it's difficult to say if it was due to the rain.

I picked out the clips with oversteer, which is induced by aggressive throttle modulation. Otherwise the car wanted to plow.

I still suspect that I am screwing up with tire pressure. Since I had no idea what to do on a wet track, I set the pressure at 2.1 bar (30.5 psi), after driving there and waiting 20 mins before going on track.

So that leads to some noob questions.
- When is the tire considered cold? Would it still be cold after normal driving to the track? 20 mins later?
- Probably the tire pressure should be even lower on a wet track than I would set it in dry?

These 15 mins sessions are annoying because there is no time to get any readings.

[Tor]

It was raining the last days, but I decided to go to Nürburgring Grand Prix circuit anyway.

[ame="https://www.youtube.com/watch?v=P8w3JDYh8Bk"]https://www.youtube.com/watch?v=P8w3JDYh8Bk[/ame]


It probably didn't do a whole lot for bedding the rears, since I doubt I got them up to proper temperature.

To be honest I couldn't feel much difference with the rear stabiliser set to hard. It still understeers mid corner. Turn in is fine and there is maybe an improvement on corner exit, but it's difficult to say if it was due to the rain.

I picked out the clips with oversteer, which is induced by aggressive throttle modulation. Otherwise the car wanted to plow.

I still suspect that I am screwing up with tire pressure. Since I had no idea what to do on a wet track, I set the pressure at 2.1 bar (30.5 psi), after driving there and waiting 20 mins before going on track.

So that leads to some noob questions.
- When is the tire considered cold? Would it still be cold after normal driving to the track? 20 mins later?
- Probably the tire pressure should be even lower on a wet track than I would set it in dry?

These 15 mins sessions are annoying because there is no time to get any readings.

[Wayno]

It's going to be way over sprung with big sway bars. The wet will make it far worse. Pretty much anyone down here who wants to go fast runs stock bars, including all the cars in the racing series.

[Tor]

Originally Posted by Wayno

It's going to be way over sprung with big sway bars. The wet will make it far worse. Pretty much anyone down here who wants to go fast runs stock bars, including all the cars in the racing series.

These swaybars are pretty moderate. 19 mm front, 17.5 mm rear. The main thing for me is the adjustability. Unfortunately I can't say how the hard and soft setting respectively compare to the stock swaybars. The lever arm is significantly shorter in the soft setting.

I got the swaybars to compensate for the coilovers which I from the get-go suspected didn't have optimal spring rates (6 Nm front, 5 Nm rear). My original budget for coilovers was 3-4000$. The reason I ended up with the ST XTA is explained in detail in this post. I would actually have preferred to keep the stock front swaybar, but for road legality reason they had to be installed as a pair. Now that they are in the documents, no one will probably notice if I change the front back. I might do that when I remove the cat in the header (fall/winter project after I moved and get my garage).

I don't regret the decision going with the XTA. I still think it's setup issues and that I am the problem. Because I am not sure what to change to get what effect, so it's a bit fumbling.

Also there is a lack of focus, I have too many task to complete in just 15 min stints. Bedding new brakes, improving my line, running in rain (no experience), seeing how my new tune behaves , changing the swaybars settings and not knowing basic things like what tire pressure to set!

I think the tire pressure is the main issue. If I could check it straight after the 15 min is up, I could adjust it, let the tires cool and note the cold pressure for next time. But bedding the brakes prevented me of doing so the the last two times, as I had to drive afterward to let the brakes cool. Next time I will make sure to come off the track hot and immediately take a reading.

- On not-so-grippy Pirelli tires I had lots of oversteer, with the swaybars set to soft front/rear.
- On Zolder, the car was pretty neutral with the Yokohama AD08R. There I had plenty of time to pit and adjust pressure.
- On Nürburgring GP (faster longer, elevation changes, cambered curves) it's understeers.


Also, the problem might be my lack of adaptability. Maybe NBR GP requires me to make changes to my driving style that I didn't yet figure out.

In any case I have fun trying to figure it all out.

------
Another topic is the tune, I was still on the AU.RICH MAF scale and the fuel trims reverted to what we saw before - around +7 above 45-5000 rpm. So I flashed the tune with modified MAF scale today (didn't want to do it before going on track).

I changed "Desired overrun mass airflow A and B" back to stock. I also allowed myself to add a slight bit of timing in the high rpm and removed a bit in the low rpm. My reasoning is that we lean it out a bit in the low rpm, and that it is not such a priority for me to get low-end power (I rather be knock free). Up high we keep the rich MAF and it didn't seem to knock. So I added half the of the additional values from the 102 octane tune, in the high rpm.

I will drive it tomorrow to let it learn and see if it starts to knock in the high rpm. Hope for a nod of approval (differences to 100 octane):

[Wayno]

I just watched the video and first corner it looks way over sprung. 6/5Kg are a good spring rate for stock bars on street tyres. The fast guys here use a higher rate on the front and push the car around the corners. I don't like that very much, but it's certainly fast when you can plant your foot down mid corner and know it's not going to swap ends.

[nikitopo]

I still suspect that I am screwing up with tire pressure. Since I had no idea what to do on a wet track, I set the pressure at 2.1 bar (30.5 psi), after driving there and waiting 20 mins before going on track.

So that leads to some noob questions.
- When is the tire considered cold? Would it still be cold after normal driving to the track? 20 mins later?
- Probably the tire pressure should be even lower on a wet track than I would set it in dry?

I think you are worrying too much with tire pressures. I was also playing for some time with pressures and then got frustrated. All these little details ruin the fun factor and the driving pleasure of the car. Just relax, get used with a reasonable pressure (personally I use the manufacturer's recommendation) and focus on the driving technique. This is also the reason I am not tempted to buy coilovers. It would give me more parameters to worry. In anyway, you cannot break any track record with this car. So, what's the point?

[Tor]

Originally Posted by Wayno

I just watched the video and first corner it looks way over sprung. 6/5Kg are a good spring rate for stock bars on street tyres. The fast guys here use a higher rate on the front and push the car around the corners. I don't like that very much, but it's certainly fast when you can plant your foot down mid corner and know it's not going to swap ends.

HA, that's actually exactly how I would describe how my car behaves normally.

The video is not really representative because almost all clip all are from the same 2 corners where I was playing around with the throttle. If I had posted a full lap it would be boring to watch.

You are probably right that it is over sprung for wet conditions. I never had that in mind when choosing the coilovers. Also the AD08Rs doesn't help either in the wet (I was overtaken by stock GTI hatchbacks probably on normal street tires).

Also worth noticing is that the first corner in the video was the most slippery corner on the whole track, especially on the dry line.

For comparison, here is a short clip with the same two curves in the dry.

[ame="https://www.youtube.com/watch?v=5TKSvUCmqhw"]Understeer in the dry - YouTube[/ame]


First the 180 deg Dunlop. Adding steering angle has no effect, other that that the front tires squeal more. You can see that I feel it out be adding/removing steering angle.

Thereafter the fast uphill "Schumacher S", and we are at "the first corner" from the wet videos. With quite substantial trail braking, the rear rotates a bit, there after the right hand curve leading to the back straight I can control the understeer by backing off the throttle a bit (at the cost of speed on the straight). These are scenarios where I want less understeer.

On the other hand, maybe I should be pleased that the rear is not trying to overtake me with 120 km/h, with my skill level. It did once on Zolder - I was trail braking, but not that hard, could be the EBD kicking in (no pedal dance):

[ame="https://www.youtube.com/watch?v=zQe5AgxK0zc"]Rear wheel drive explained... :-)) - YouTube[/ame]

Originally Posted by nikitopo

I think you are worrying too much with tire pressures. I was also playing for some time with pressures and then got frustrated. All these little details ruin the fun factor and the driving pleasure of the car. Just relax, get used with a reasonable pressure (personally I use the manufacturer's recommendation) and focus on the driving technique. This is also the reason I am not tempted to buy coilovers. It would give me more parameters to worry. In anyway, you cannot break any track record with this car. So, what's the point?

I agree to a certain extent. Though I think it's a matter of personal preference and goals.

The fun factor may be just as high with a stock car, or at least without worrying about setup and just drive with whatever you get. In this case you are right, that one can focus on driving technique and learn to work around behavioural shortcomings of the car.

But for me part of the fun is optimising the car so that it behaves the way I want it and to make it as fast as possible with what is possible with the setup. In the meantime I work on my technique as well to work with the setup the way it is at the moment. The video I posted are all clips of trying to get the car to stop understeering, which succeed to some extend. In the Dunlop curve (the cambered 180), if I just put my foot down the car would plow. By modulating the throttle I got it to rotate. A mid corner left foot dap on the brakes might have done the same but I was too chicken to try.

The combination of using different techniques and adjusting the car is what I find fascinating. Lap times in itself is not so interesting, but a way to measure if what is done different works or not. This is in part why I have little interest in the Nordschleife, because it's so long and, I think, has so many variable that it's difficult to make back-to-back lap time comparisons.

Although we won't set records with the car, there is a substantial 86/BRZ community here, and there is somewhat respect credits to be gained by setting a good lap time.