Quote from: AdamR28 on November 30, 2020, 10:25Two different ways of skinning the same cat, eh Always an interesting comparison.

The previous Munter (115bhp, 800kg) did 2:04s at Oulton so even with the wank tyres I'm hoping M2 will be similar. The chance of getting a clear lap on a dry track on a sold out day at Oulton in winter? Minimal, but we'll give it a go. Hope my cheapo FauxPro camera lasts the day.

Oh dear Adam - don't talk about cats in that way - I've just lost mine.

I honestly think it looks decent! Proper purposeful and non-tryhard track car. Really love the taped up doors and mirror mount holes! 

@Chilli Girl - really sorry to hear about your cat. Feel better soon!

Really sorry to hear about your cat, Jane. Our little furry friends really do become part of the family, don't they? As Lee says, I hope you feel better soon.

Haha. Yeah I went to town with the gaffer tape. Was cruising down the M6 yesterday and got overtaken by a white rep-mobile that clearly does lots of motorway miles between washes. The amount of turbulence displayed around the door handles and shut lines - especially at the rear where the flow is already interrupted - was impressive. Something along the lines of this...



The dirt in front of the shut line indicates the airflow has been sufficiently disturbed by the gap to reverse in direction - pulling dirt with it, but also adding drag to the car.

I have recently started to take notice of these aero nuances, including the front (and rear) wheel deflectors, and flow separators around the area of the rear lights. Saw a great example today on some sort of SUV but can't for the life of me remember what it was!

Anyway, the idea of these is to try and 'break off' the air that would otherwise normally flow around the lights / side of the rear quarter, then separate and cause a low pressure region, generating drag. Using a sharp corner, or in the case I saw this morning a small 'ridge', helps prevent the air from 'sticking' to the car as it swaps around. This means the low pressure region is further away from the rear of the car, thus reducing how much 'pull' it can exert backwards (it's only pulling on air, not the rear panels of the car). Just found a photo of the latest Civic which is a good example - the shape of the lights, the detail in the lights, and the little deflector:



So I plan to add some of these to Mr Poo. Marginal gains, but it's a good talking point!

Quote from: AdamR28 on November 30, 2020, 10:25Two different ways of skinning the same cat, eh Always an interesting comparison.

The previous Munter (115bhp, 800kg) did 2:04s at Oulton so even with the wank tyres I'm hoping M2 will be similar. The chance of getting a clear lap on a dry track on a sold out day at Oulton in winter? Minimal, but we'll give it a go. Hope my cheapo FauxPro camera lasts the day.

2:04 with PTW of 7kg/hp....NICE!!! Well i'm now expecting a sub 2 minute lap Adam with the M2 at 5.4kg/hp, no pressure :-)

Quote from: AdamR28 on November 30, 2020, 11:33So I plan to add some of these to Mr Poo. Marginal gains, but it's a good talking point!

The more marginal deflectors do very little but they nevertheless help add up to notably more stability, not necessarily more speed. The added stability though leads to more feel thus more confidence thus indirectly more speed.
I was expecting an effect of the rear deck lip ofcourse, otherwise I would not have bothered but the perception of stability was greater than expected. It was the motivator for going down the hole of aero info on the web and fitting the SillyBigWing. This time it, incombo with the lip, does exactly what expected.

Good to know Petrus, thanks!

I plan to add a rear lip at some point too, but not sure how it will work on a car without a roof (or windscreen!)...


From what I can tell, there is separation on a standard car as air flows over the roof (image below). Notice how the rear window doesn't clear of water droplets when driving along first thing in the morning? There's no / very little moving air there to blow it off!

The air basically gets punched up by the front of the screen, skims the roof a bit, then off into the ether.

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So, two things, when you have a roof:

1) Any rear wing needs to be up pretty high to be within any significant area of flow, for it to be effective.

2) However (can't find the documentation / reference now), adding a little lip to the boot lit can improve the effectiveness of the rear wing. My sketchy memory of this is that air builds up against the lip, leaving a stagnant region which increases the thickness of the boundary layer all the way along the boot lid to the base of the rear window. This has effectively 'filled in' that region, so the air can stay 'stuck' to the rear window better - making that blue region in the image above thinner, and the yellow area closer to the boot lid, so a wing doesn't have to be as tall to work effectively.

However, the study was on some sort of front engined car, so this may not work at all once you start adding vents. In the MR2's case, using a small lip to attempt to build a thicker boundary layer on the rear lid may end up reducing cooling and have air 'spilling' down into the vents. Either way, this document gave me a clue as to how counter-intuitive aerodynamics can be, and how little I know about it!


Leaving the screen on and removing the roof puts all this to pot again, with the wing having to be REALLY high to get into any sort of useful airflow. Obviously the image below isn't an MR2, but it also handily illustrates just how changing the angle of the roof / rear window can maintain flow separation over it - meaning you don't need a huge wing. Wonder if this is where the term 'fastback' came from?



I've seen data that suggests removing the roof can add up to 25% drag in some cases!


Removing the screen and roof completely? I don't really know what that will do. My initial guess was that removing the windscreen probably turns the whole passenger compartment into a large low pressure region, increasing both drag and lift. However, I then saw this... which is basically an extreme version of what I currently have. It appears a bigger 'lip' - probably in front of, but maybe also behind the cooling duct according to an article I just read - may even be enough to shoot air completely over the cockpit!

Very interesting @AdamR28 and food for thought.

However, I can't help feeling that all the current non-roofers without turbo's will now be fitting a turbo in order to compensate for the drag  

As for @Petrus , I dread to think what the outcome may be

Quote from: AdamR28 on November 30, 2020, 15:05So, two things, when you have a roof:

Most cars, incl. the MR2 roof up, are roughly airfoil shaped with the longer side up.
The airflow is indeed turbulent behind the cabin but also flows downwards. Also, even the turbulent air flows to the rear over the lid. As such the wing indeed sits in more lamina flow the higher it sits relative to the roof but it does not have to be as high as the roof.
Roofless it will still sit in an airflow, just not only laminar, so it will still have negative lift and even direct the airflow.
The lip on the rear of the deck on it´s own primairily provides a tear off ridge.
Under a wing though it also raises the speed under that wing thus increasing the airfoil effect.
As the rear wings can be found at silly low prices I´d say you could simply try.
Now, with a roof, even just a windscreen the so called 3D makes sense but in your case it does not so simple straight will do better.


The jocular observation of turbo needed for drag strongly reminds me of Jeremy Clarkson coming up with the jewel that those with added aero nééd corner faster. I think Kyle Engineers both mentions and explains (refutes) it in a video.
Lest it becomes the next urban myth; on cars negative lift of the airfoil and drag increase are nót necessarily directly related.

I know that running with the hard top on is more than worth the 18kg penalty it gives. The difference in VMax at Knockhill is 101mph vs 106mph, and >1 sec per lap.

Concerning drag: redúced the drag coëfficient and added negative lift

Quote from: AJRFulton on November 30, 2020, 19:36I know that running with the hard top on is more than worth the 18kg penalty it gives. The difference in VMax at Knockhill is 101mph vs 106mph, and >1 sec per lap.

That's a good stat, thank you!

Quote from: AdamR28 on November 30, 2020, 20:16

Quote from: AJRFulton on November 30, 2020, 19:36I know that running with the hard top on is more than worth the 18kg penalty it gives. The difference in VMax at Knockhill is 101mph vs 106mph, and >1 sec per lap.

That's a good stat, thank you!

VMax is off a Garmin GLO and app data, so it's 10Hz refresh so confident it's accurate enough.

Laptime is a bit harder to compare, as it was done morning session vs afternoon session and had heated up a bit - plus the morning session had the bit of new AR1's. However going by the GPS data the majority of time was lost on the straights.

I wish I had the graphs but it was an old phone and old laptop.

Quote from: AJRFulton on November 30, 2020, 19:36I know that running with the hard top on is more than worth the 18kg penalty it gives. The difference in VMax at Knockhill is 101mph vs 106mph, and >1 sec per lap.

Just for accuracy sake where did the 18kg hardtop weight come from?

I though the last person to weigh it said 25kg but perhaps I am mistaken.

I have one I can weigh if necessary, always good to have this info to hand!

Nearly there now... have been putting off doing the door skin as its a bit of a bugger tbh, but hoping to tackle that tomorrow.

Today's work fitted saw the floor for the final time, a FauxPro mount made and fitted, some more correx gaffer taped in place to enclose the rear and keep water off the ECU, and a few stickers added.

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In 'got a bit lucky' news, I'd had half an eye on this but not really calculated anything - the rake of the floor is near perfect. 85mm ride height at the front, 95mm in the middle of the car, 100mm just in front of the rear wheels, then kicks up to about 115mm at the very rear of the floor. I made the very rearmost mounts a different style to the rest, so I could use spacers to adjust the height at the back, creating a mild diffuser effect if I wanted.

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Comin'a getcha! 

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Looking great Adam.

I think sterling moss would race it at Le Mans.
Respect.

Quote from: 1979scotte on December  1, 2020, 06:35

Quote from: AJRFulton on November 30, 2020, 19:36I know that running with the hard top on is more than worth the 18kg penalty it gives. The difference in VMax at Knockhill is 101mph vs 106mph, and >1 sec per lap.

Just for accuracy sake where did the 18kg hardtop weight come from?

I though the last person to weigh it said 25kg but perhaps I am mistaken.

It is completely skinned. Literally just a shell with polycarb window in it - it may even be lighter than 18kg as it wasn't exactly a scientific method of measurement.

Because it's incorporated into the roll cage, it's a pain in the arse to take off (purely for lack of access as much as anything) - but one sunny track day last summer, off it came. Just as an experiment - As I knew I was going to be doing this, it was literally stand on bathroom scales holding it to see what it weighed in the paddock.

Car was a fair bit slower on the straights using Harrys Lap Timer with a Garmin GLO.

Quote from: AJRFulton on December  2, 2020, 00:07

Quote from: 1979scotte on December  1, 2020, 06:35

Quote from: AJRFulton on November 30, 2020, 19:36I know that running with the hard top on is more than worth the 18kg penalty it gives. The difference in VMax at Knockhill is 101mph vs 106mph, and >1 sec per lap.

Just for accuracy sake where did the 18kg hardtop weight come from?

I though the last person to weigh it said 25kg but perhaps I am mistaken.

It is completely skinned. Literally just a shell with polycarb window in it - it may even be lighter than 18kg as it wasn't exactly a scientific method of measurement.

Because it's incorporated into the roll cage, it's a pain in the arse to take off (purely for lack of access as much as anything) - but one sunny track day last summer, off it came. Just as an experiment - As I knew I was going to be doing this, it was literally stand on bathroom scales holding it to see what it weighed in the paddock.

Car was a fair bit slower on the straights using Harrys Lap Timer with a Garmin GLO.

Thats fine you've lightened it.
Was just checking.
You know how people are they'll all go round quoting 18kg for a hardtop when its a fair bit more.

Took a while to catch up on a lot of this Adam, you've been going hard at it! Good skills

Appreciate this was a few pages back, but good effort on opening up about your mental health too... it affects more us than most people realise and it's all too easy for us to keep it under wraps. Best thing I ever did was speak to someone about the dramas going on in my bonce, it literally changed and probably saved my life.

Quote from: 1979scotte on December  1, 2020, 21:50I think sterling moss would race it at Le Mans.

Perhaps not if he had a better option!

Especially with the piece de ridiculousness that is my gaffer tape and correx roll cage aerofoil.

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Absolutely daft, but bearing in mind this image...



If I have got the Cd down from 0.47 to 0.15, just this small appendage has improved the theoretical top speed of the car by around 4mph! (Edit: Cocked up the maths, it's more like 1mph, ha).


More silly testing - this time with the airline. Again, obviously not that close to real world as the flow of air is quite 'defined', but at least gives a visual of the sort of things that will be going on...

Airflow over the passenger side 'windscreen'. This is less than 1" tall.



Drivers side, around 2.5" high:



The lip on the bonnet duct / vent:



The exit from the bonnet duct, with the compressor generally squirting through the hole in the front bumper:



And finally the roll cage - you can see the completely stalled (ie. drag) air behind the 'open' bar, and a nice attached airflow over the aerofoil:

Quote from: AdamR28 on December  2, 2020, 11:50More silly testing -

Very far from, Adam.
It is totally realistic representation of what réally happens.
I think it awesome.

It is also far from negligable.

Thanks for the emperical confirmation/illustration of the science.

p.s. mán all that caffeïne stimulated mental effort to shave of 2 kilo there, a half here, etcetera and you chuch some 150 more like thát, phew.

No caffeine must be the key

The car is now on the trailer ready for Saturday! This is a bit of a unique feeling - I keep thinking it's Friday, because I'm never done in plenty of time.

Sorted alignment last night, kept it 'safe' to start with:

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Found a fibreglass roofing panel on the car park at work a few weeks back following a particularly windy night. That'll come in handy I thought, and it has - as a little lip to the boot lid (well, it's attached to the bumper) in an attempt to reduce some drag / wake.

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Stuck some Tempilaq on the left hand rotors (for anyone who likes this sort of thing, I've just seen a bargain on eBay: https://www.ebay.co.uk/itm/Tempil-Tempilaq-Temperature-Indicating-Liquid-All-Temperatures-12-2oz-Bottles/174054107054?hash=item28866ee7ae:g:PvwAAOSwCXVdmG7x).

Why only the left hand side? On UK circuits, 66% of the turns are right handed, so with trail braking the left hand brakes see more use than the right, and I actually experience faster pad wear on the left hand side of the car.

The two colours 'indicate' at around 500'C and 600'C - if I'm hitting these sort of temps then I'll be running into fast pad wear and may need something more beefy. However, looking at the forecast, I don't think that'll be a problem on Saturday...

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Rolled him / her / it outside for a photoshoot.

The eagle-eyed will spot the 'unte' on the rear bumper - I have the M, the R and the 2 ready to go back on as well but can't find any double sided sticky foam pads! Maybe the ones I've ordered will arrive tomorrow...

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That front end. Not. Pretty.

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I think it looks hilarous with the random bit of wood hanging out the back    On that note I am wondering if the area under the exhaust might see some 'adverse temperatures', specifically after coming in following a session. I'm not concerned while on track due to the NACA duct in the floor, but it may need some help in the form of a polished aluminium sheet, spaced away from the ply by a few mil. I will try to remember to knock one of these up and pre-drill it, so I can screw into place on Saturday if necessary.

Got a garage booked (hopefully the same one as @Maurici ) and really looking forward to some track time!



Upon emptying the trailer I was faced with this. I obviously had 'some' ideas pre-aero-learning, but my brain is looking at things very differently now...

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I'm picturing the sniggers from the snobs in their Caterfields and Porsches when you roll up. For them sniggers to turn into shock when you're pushing them aside out on track.

What tyres and pads are you running Adam?

That was standard with the orignal Munter yep, so hoping it will be the same again!

Apec pads and Falken ZE914 tyres. Only the best. Snigger.

Quote from: AdamR28 on December  3, 2020, 17:24That was standard with the orignal Munter yep, so hoping it will be the same again!

Apec pads and Falken ZE914 tyres. Only the best. Snigger.

Nah you'll be sound with them on such a light car. I've had the 914s on my Celica 190, and just fitted a set of FK510's to my F30 330d. Falken are really underrated tyres.