GT wing - track use (SMP + WP)

[guss]

the only things i can think of & thanks to you fine gents for pointing out one of them which i totally did not even consider are:
1. use of R spec tyres (current are hankook Rs3's which are road legal - semi slick), i will look into this in near future

Hankook RS3’s are not semi slicks. People seem to confuse them in the same way they do for Kumho KU36’s. They are both road tyres that work well on the track, but they are not R-Specs (aka semi slicks).

2. the car does have slight rake, in that iv'e used tein's recommendations when lowering the car.. the rear is slightly higher than the fronts (literally 1cm or so), would this have bearing with respect to weight shift - am i better off having leveled height front & rear?

the car slips in corner entry predominately.. i find hard braking/weight shift is the contributor of this, which is evident in the below vids:

Considering you had the car corner weighted, a little bit of rake shouldn’t make much difference, if any.

Looking at the videos, it looks like you’re being too aggressive changing gears down, which is probably what is upsetting the balance in corner entries. You can either brake harder before changing down, or heel and toe, or ideally both.

You may also want to try higher gears in some of the corners. As an example, turn one at SMP GP should be taken in fifth gear rather than fourth, with just a lift off or minimal braking before entering it. The car will feel much more settled and you’ll feel more confident to enter the corner at higher speeds.
You also changed into second under brakes coming down corporate hill to turn right, which caused the engine to scream. That corner should be done in third gear with a very wide exit to keep momentum, as there is plenty of escape area at the exit.
Again, at WP aggressive down changing is upsetting balance at turn 2. Turn 3 can be taken in fourth gear as well as turns 6 and 9.

all other advice welcomed. i dont compete in any race series.. just me myself & I against the time.. for now.
cheers,
J.

What sort of lap times are you doing at SMP GP and WP?



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[greenMachine]

I think I regret my first post. Too much too soon, and it has been all downhill since. All great info, and kudos to all who contributed, but ...

get your wing. Try it. Carefully, in light of comments about high speed understeer. Play with wing angles (AoA in tech-speak), make a splitter for the front to improve high-speed front end grip, get balance that you are happy with. Play with alignment, tyre pressures; adjust shock settings front/rear, all in interests of further improving car speeds/lap times/handling.

ALWAYS adjust one thing at a time. Have a notebook, write down what circuit, weather, temperatures, what you are changing to/from, and the lap times before after, and any relevant comment ( eg 'lost top speed', 'increased understeer' etc) That way you know what you changed, what the result was, and if not good, you can put it back and try something else. Weeks or months later you will have the answer to the question 'have I tried ...?'

If you haven't got a probe pyrometer for tyre temps, get an el cheapo infrared one. Take (and write down of course) temps of each tyre asap after the run, inside tread, middle tread, outside tread - that will tell you what parts of the tyre are doing the work, you need to adjust your camber to even out the temperatures and try and get all the tread working hard, not just the outside or the inside.

Motorsport is a data game. It starts with a notebook, and that will get you on the road to having a fast car, one that is well behaved, and one that you can basically forget making faster so that you can concentrate on making the driver faster. When the driver can't go any faster, back to the car ...

Good luck

[Ned Loh]

If you haven't got a probe pyrometer for tyre temps, get an el cheapo infrared one. Take (and write down of course) temps of each tyre asap after the run, inside tread, middle tread, outside tread - that will tell you what parts of the tyre are doing the work, you need to adjust your camber to even out the temperatures and try and get all the tread working hard, not just the outside or the inside.

I agree with most of what you said but for the sake of original poster and others, must disagree with above. In my experience a hand held IR is next to useless for a track car. The surface of the tyre cools quickly, much better to use a probe and get down near the cords. If you are going to the trouble of recording tyre temps to find time, the price difference of a probe pyrometer vs IR is almost irrelevant in the scheme of a track car.

Also, and perhaps most importantly, i’ve NEVER found the car fastest with “even” tyre temps.

[The Green Goblin]

What are you spring rates
Front 10kg rear 8kg - tein monosports.

and sway bar thicknesses?
Whiteline adjustable - 24mm front & 16mm rear
Are the sway bars hollow? no, solid units.

If you don't know this info, what brand is everything. If you don't know the brand... figure it out. This is bread and butter information needed to set up the car.
appreciate trying to be specific here man..

Next, what are you alignment specs?
Front:
toe in L + R = -2
camber L + R = -1.8
caster L= +7.1
caster R = +7.0
height 315mm

Rear
toe in L + R = +2
camber L + R = -1.9
height = 320mm

[The Green Goblin]

the only things i can think of & thanks to you fine gents for pointing out one of them which i totally did not even consider are:
1. use of R spec tyres (current are hankook Rs3's which are road legal - semi slick), i will look into this in near future

Hankook RS3’s are not semi slicks. People seem to confuse them in the same way they do for Kumho KU36’s. They are both road tyres that work well on the track, but they are not R-Specs (aka semi slicks).
not sure about that dude.. i checked the hankook web page & although no mention of 'semi slick' instead 'ultra high performance tyre'- of all the normal road tyres i have used, they have never performed like the RS3 in that, once you get heat into them, they expand & activate more grip..a normal road tyre doesnt do this.. they're loud, sticky/pick up whole bunch of rocks.. dont squeal like your road tyres do when pushed etc..

2. the car does have slight rake, in that iv'e used tein's recommendations when lowering the car.. the rear is slightly higher than the fronts (literally 1cm or so), would this have bearing with respect to weight shift - am i better off having leveled height front & rear?

the car slips in corner entry predominately.. i find hard braking/weight shift is the contributor of this, which is evident in the below vids:

Considering you had the car corner weighted, a little bit of rake shouldn’t make much difference, if any.

Looking at the videos, it looks like you’re being too aggressive changing gears down, which is probably what is upsetting the balance in corner entries. You can either brake harder before changing down, or heel and toe, or ideally both.

You may also want to try higher gears in some of the corners. As an example, turn one at SMP GP should be taken in fifth gear rather than fourth, with just a lift off or minimal braking before entering it. The car will feel much more settled and you’ll feel more confident to enter the corner at higher speeds.
will try that however, fifth gear revs are too low, where as in 4th power band is there to use in corner exit. i use 4th to slow the car down slightly cause i need larger testes..

You also changed into second under brakes coming down corporate hill to turn right, which caused the engine to scream. That corner should be done in third gear with a very wide exit to keep momentum, as there is plenty of escape area at the exit.
i've used 3rd previously find it slower..revs too low.

Again, at WP aggressive down changing is upsetting balance at turn 2. Turn 3 can be taken in fourth gear as well as turns 6 and 9.

all other advice welcomed. i dont compete in any race series.. just me myself & I against the time.. for now.
cheers,
J.

What sort of lap times are you doing at SMP GP and WP?
WP = 115.34
SMP GP = 158.64


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thanks mate..

[The Green Goblin]

I think I regret my first post. Too much too soon, and it has been all downhill since. All great info, and kudos to all who contributed, but ...

get your wing. Try it. Carefully, in light of comments about high speed understeer. Play with wing angles (AoA in tech-speak), make a splitter for the front to improve high-speed front end grip, get balance that you are happy with. Play with alignment, tyre pressures; adjust shock settings front/rear, all in interests of further improving car speeds/lap times/handling.

ALWAYS adjust one thing at a time. Have a notebook, write down what circuit, weather, temperatures, what you are changing to/from, and the lap times before after, and any relevant comment ( eg 'lost top speed', 'increased understeer' etc) That way you know what you changed, what the result was, and if not good, you can put it back and try something else. Weeks or months later you will have the answer to the question 'have I tried ...?'

If you haven't got a probe pyrometer for tyre temps, get an el cheapo infrared one. Take (and write down of course) temps of each tyre asap after the run, inside tread, middle tread, outside tread - that will tell you what parts of the tyre are doing the work, you need to adjust your camber to even out the temperatures and try and get all the tread working hard, not just the outside or the inside.

Motorsport is a data game. It starts with a notebook, and that will get you on the road to having a fast car, one that is well behaved, and one that you can basically forget making faster so that you can concentrate on making the driver faster. When the driver can't go any faster, back to the car ...

Good luck

lol - downhill since aye, perhaps your expectations were set a little too high?

in all seriousness, i really appreciate the time taken to provide such level of detailed responses & have taken notes of all that you have mentioned. it's obvious that you are at a much higher level of understanding & practices..with respect to car set up & making the most out of track days &/or racing.. it sounds like you genuinely have a passion for the trial & error, data collection/logging aspects etc. again, i am no where near this level & i dont dedicate too much time to this currently - that may & will change in time. i personally find that doing so at a comprehensive level will take the fun out of it.. it becomes too serious.. unless it was either my full time job or i was absolutely obsessed with it. so not everyone is on the same level, lets not assume that. i think i still have some driving improvement..though i am getting close to the cars limits (been in it's current form for quite some time, so improvements in my times prove that i'm on the right path)..any changes from here on in will be thoroughly thought out. at this point, i will hold off all aero.

in saying that, i completely agree with your last sentence..add to that mechanical engineering also..

thanks again,
J

[The Green Goblin]

This will not be a short post...

This is from SMSP using data from WTAC, which in Kyle Forster used to design my new wing. This shows the difference (simulated) by changing drag/downforce etc without changing the cars power. The blue line is 8 secs (simulated) faster (1:36.19) with the orange doing a 1:41.15. Decreasing drag by 10% could achieve a lap time of 1:44.61 (brown), if I could drive it as per the simulation...



The orange is using full pro-am type aero and down the main straight you can see the impact that drag will have. However through the corners there is a gain and hence why faster, despite the sacrifice of straight line speed. This is the trade off you need to consider. However, to have high corner speeds requires tyres (and a suspension setup) capable of achieving them. A G Plot is very useful for this.

Hmmm by Eipeip, on Flickr

When considering a wing, not only do you need to consider the type (2D, 3D, twin element) but how this will impact the cars aero balance. A 3D wing works better at lower speeds and can be effective if it is not in clean air because of the 3D shape. Whereas a 2D or twin element needs clean air. The key is to keep the air attached as it comes down the rear window.



If the air does not stay attached to the rear window then it can not be fully utilised by the wing, you want 'clean' air at the wing not disrupted flow.

Another point to consider is how the data is portrayed by makers. For example with my wing the data is published as if the wing is in free air, that is not mounted. real world testing shows that the mounts have an impact on the airflow and hence the wing is not as efficient in real life as the published data.

This then goes to the argument of swan neck vs 'normal' mounts. Again a real life experience with a boot mounted mount was as the car went faster the boot was pushed down further (against the seals) hence the AOA was changing for the worse as downforce was reducing. Further it can deform the boot if you do not keep a close eye on it. The benefit of the swan neck is that air flow under the wing is not impacted, however requires extensive 'body' modifications to install and make effective.



By the way, my current wing (and mounts) could be available in July...

Saving weight will allow the car to accelerate faster where as drag will allow a faster speed. Downforce MUST come at the expense of drag, hence evaluating what you will benefit most from is critical.

With respect to drag, I would suggest you do coast down test to evaluate different setups. Suggestions to decrease drag:

1. Remove rear bumper/difusser and test if drag is reduced. If 'better' then cut bumper down (or remove completely). Then consider if a difusser can be designed to improve aero. With a dual element wing a difusser may not be required.
2. Use vortex generators on hardtop. Evaluation can be done with wool tuft testing.
3. Removing the air from inside the wheel arches. This can be evaluated by differential air pressure tests.
4. Making a front air dam and 'splitter'
5. Brake duct holes to inside the 'mouth'.
6. Mouth size could be reduced. Reducing the mouth size is easy to test (coast down). This should be done with caution as it will decrease air flow into the radiator.
7. Canards to improve from downforce, again this will be a major consideration if a dual element wing is used. Canards are more 'tweaking the balance.
8. Remove rear/front mud flaps

If you have data logging capabilities then you can use this to evaluate drag. A quick way to check how changes have impacted the ca is to compare acceleration, ACCEL = 'Accel G Force'*9.80665. This converts the Accel G Force into acceleration m/sec².

The picture below shows Sydney Motorsport park in 2017 (blue) was accelerating faster than red (2015) at the same speed.

ACCEL by Eipeip, on Flickr

Happy to provide some more feedback/real world tests. As others have said you need to decide what direction you are going and if you want to use your horsepower for straight line speed or to overcome drag and increase corner speed. Also, do not neglect your suspension as downforce will impact available travel on your dampers...
This is a good thread to read through https://www.miataturbo.net/race-prep-75/post-your-diy-aero-pics-63769/

WOW.. this is insane next level stuff mate, thanks so much for the detail.

[The Green Goblin]

I find currently the ass slips out a little too easy when car is being pushed

Is this happening on corner entry, apex or exit?
Does it start out fine and then starts after a few laps?
Alignment?
Tyre pressure/temps?
Rake?

Seems to me that you need to get the handling sorted first, before ctomolicattivng the issue with aero.
Like Magpie says and in addition spring rates, damping, sway bar settings.
Once you have the handling sorted then move up to the best tyres you can afford before spending on aero that may or may not help.
The previous owner of my car recorded his best lap times without aero. I bought the car without the wing, which he sold separately.

thanks man, agreed. in saying that, handling side feels solid as mentioned in prior posts.. i think the next bet is better tyres as you've mentioned, which is something i will def. look into.

side note, i think i saw your car at a recent SMP GP twighlight trackday - 8 feb.. you actually sat behind me & passed me if you recall. also seen your car at deckspeed ages ago, it's on the more serious side of development. my car isnt stripped out, is road registered.. air con, 1099kg's, no engine mods besides exhaust.. so theres plenty of development in it.

[RS2000]

The first thing I suggest to do is ditch the 16mm rear arb.
Most people find the 24/16mm combo causes oversteer, & you are already a bit orientated towards rear stiffness with 10/8 springs.
Try the factory rear arb if you still have it.

[greenMachine]

Yes, it needs to be fun . I think that you have a good idea of where you are going, a lot of advice on where to and how to take it to the next level, which you can take up as and when you feel the need arises.

[Nuddy]

side note, i think i saw your car at a recent SMP GP twighlight trackday - 8 feb.. you actually sat behind me & passed me if you recall. also seen your car at deckspeed ages ago, it's on the more serious side of development. my car isnt stripped out, is road registered.. air con, 1099kg's, no engine mods besides exhaust.. so theres plenty of development in it.

Yes I was there on 8 Feb. I had gearbox trouble towards the end of the night. 3/4 synchro sleeve seized. Fixed at Deckspeed next morning.
Mine is road registered, has aircon, added weight of half cage, soft top removed, replaced with carbon hardtop, probably weighs much the same.
If it was at Deckspeed ages ago it was with the previous owner as I've only had it for a year.