Mr Poo the MunteR2

[JB21]

I'm defo in the camp of reacting to what the car does, instead of instigating the movement. Saying that I feel I can react pretty well but I know I have a long road ahead to be one with the car.

This is my first ever rear wheel track car, and road car for that matter so jumping straight into a super stiff MR2 2zz conversion with its MR layout, short wheel base and no driver aids apart from ABS was a real baptism of fire.

Would be good for you to come out with me on track to observe my current technique, then come in to the pits to discuss where I can improve. I sat come in to the pits as the car is that loud you can't hear a bloody thing when someone is speaking, lol.

[Petrus]

This is why I am a HUGE advocate of learning to drive on track in a soft car, with low power on cr@p tyres.

Why I left the newly bought MR on cr@p tyres with the winter coming up.

About braking you are só spot on.
When racing motorcycles I was one of the latest brakers yet always smóóthly applied them so the bike could load the front. Just grabbing a handfull is a sure way to dump it on the tarmac. Also less brusque applying gives you feel and the two allow you to brake hárder thus later even though you initiate the proces earlier.
Same thing un-braking; letting go unsettles the bike and same thing the car.

[AdamR28]

Would be good for you to come out with me on track to observe my current technique, then come in to the pits to discuss where I can improve. I sat come in to the pits as the car is that loud you can't hear a bloody thing when someone is speaking, lol.

Yeah man, absolutely happy to - I have two lids with intercoms, which work well enough for open cars, so should do the job in yours too.

And yep, your car is definitely not easy to learn in, you're doing well to keep it on the black stuff! You really need to have a crack in mine to see what I mean.

Weirdly though the wheelbase thing seems to be one of those 'internet myths' - it's actually 100mm longer than a 997 911 for example, giving a wheelbase:track width ratio on the MR2 of 1.64, and the Porsche 1.55 - so technically the Porker is less stable.

For further comparison, the latest mx-engineinwrongplace is 1.54, and the original 1.59, an S1 Elise is also 1.59, and the 'golden ratio' is said to be 1.6:1.

So technically, the MR2 is a very 'stable' car!

[B.RAD]

Really good read and although we've discussed this many times, being able to read and digest at my own pace is really helpful.

Best thing I ever did for my technical skills as a driver was sell the Westfield and buy an MX 5, slowing everything down has brought my driving on in leaps and bounds. I'm nowhere near your skill level (yet 😊) but am so much more confident to jump in any car and thrash it hard having given myself the time to work these things out in a slower car.

I'm actually coming back from what you're describing (in terms of late braking, rather than car rotation), I was always very proud to be the last of the late brakers, gaining maximum 'on throttle' time and minimising the braking zone. However, with a decent data logger during testing and my race at Mallory, found that I could actually be a whole lot faster by braking earlier, lighter and carrying more speed through the corners, letting the brakes lift and turn the rear of the car into the corner and then planting the throttle earlier to 'correct' the car and pull it through. This was wrong wheel drive of course, and I found it almost too easy to drive compared to RWD. It was a massive 'eureka' moment for me though, and I can't wait to try again!

[AdamR28]

Nearly added that to my post actually... the best way to get better at driving? Buy an MX5

[Petrus]

Nearly added that to my post actually... the best way to get better at driving? Buy an mx-engineinwrongplace 

Ok, no MX, but we have 4 rwd cars in the family. No FWD in the last 15.

[Jondoeclsm]

What do you calla car with the windscreen removed like this?  I wonder what other cars could benefit from this sort of help?  Boxster? Has anybody done that?

[Petrus]

What do you calla car with the windscreen removed like this?  I wonder what other cars could benefit from this sort of help?  Boxster? Has anybody done that?

Speedster.
Yes, many a LeMans racer and before that Brooklands specials had mínimal to no windscreens.
It reduces the frontal area and from there it is a trade off between that and ´slipperyness´ for the bestfor the circumstances.

[AdamR28]

What do you calla car with the windscreen removed like this?  I wonder what other cars could benefit from this sort of help?  Boxster? Has anybody done that?

Munter

All cars are better without a windscreen. Its a fact.

[Petrus]

All cars are better without a windscreen. Its a fact.

When living together with the dog yes...



Not so sure about a woman.
Remember the thing TopGear did about no windscreen cars? Now replace the clowns by three random wives dropping off the kids at school.

[1979scotte]

All cars are better without a windscreen. Its a fact.

When living together with the dog yes...



Not so sure about a woman.
Remember the thing TopGear did about no windscreen cars? Now replace the clowns by three random wives dropping off the kids at school.

Great pic

[AdamR28]

All this talk of wind, reminds me...

On the way back from an event on Sunday in The Bucket, I snapped a couple of interesting photos while filling up with fuel.

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What do these show? Well, my limited understanding is this...

The car had been on a wet motorway for maybe an hour at this point, so the lines of dirt must mean there is stagnation of the air where the dirt has been left. Both sides of the car shows exactly the same patterns.

First photo - the panel gap is creating some sort of turbulence. Whether that is due to air from the 'outside' stalling in the gap and creating some sort of mini 'air dam', or there is high pressure air leaking out of the wheel arch between the quarter panel and bumper I don't know, but either way that dirt means stagnant air = drag.

Same deal just behind the small flare on the wheel arch, it must be causing some sort of separation to have the dirt sat there in that position / shape.


Up front, again a stalling behind the flare of the arch.


So what does this mean for Mr Poo? Well, I need to get him out of the trailer and have a nosey at the dirt patterns, but I don't remember there being anything as obvious as this after Oulton Park.

That would indicate - maybe - that the front deflectors are doing their job, keeping air out of the wheel arches and the 'spin cycle' of the front wheels / tyres, and thus no stalled air immediately behind the arch flare.

At the back, my only guess is that everything has been sufficiently disrupted by the time it gets to the panel gaps between arch and bumper that there is no decent flow there at all. With there being no side windows air will try to 'spill' from an area of high pressure (down the sides of the car) to low pressure (inside the cockpit), the flat floor will change things underneath a lot too.


Can I make further improvements to reduce drag? I think so. I've been heavily researching vortices these last few days, and I think I can use them to 'seal' areas of the car, and direct air to places I want it to go, rather than where it wants to go.

The idea behind using vortices is that you can combine low energy air from the boundary layer with high energy air further from the surfaces of the car, blending them together in a spiral.


Those who follow F1 might be familiar with the term Y250 vortex. This is a vortex the teams deliberately develop to improve airflow over the car, and it starts at 250mm from the centreline of the car. Why 250mm? Because the FIA banned aerodynamic devices on the front wing for the centre 500mm.

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So this vortex spins its way down the car, dragging other air with it, bouncing off the bargeboards and then being directed low down the sides of the car. This has a few effects - ensuring clean air reaches the rear wing, and also it attempts to use this highly charged vortex air to 'seal' the underfloor of the car.

Remember the side skirts used in F1 of the late 70s and early 80s, which were banned? Well this is the modern F1 designer's way of trying to emulate that.

https://i.imgur.com/8PyG5vg.gifv



You will also notice the direction in which the vortex is spinning in the (static) image above - clockwise - so if you are looking at the front of the car, down the left hand side, that spin is trying to pull air out from underneath the car (less air = low pressure = more downforce).

Obviously all of this has to be taken into consideration with other aspects of the car, which is why the front wings on these things are so complex!

The front wing effectively has 3 separate functions. Working from the centreline outwards... the first 25% (ish) creates the Y250 vortex, the middle 50% (ish) generates downforce, and the final 25% (ish) creates 'outwash' - moving turbulent air away from the sides of the car. This has the secondary effect of creating lower pressure directly behind it, which helps 'pull' the Y250 vortex outwards towards the edges of the floor.

Photos... This is the approximate path of the Y250 vortex:



And this excellent video shows the other airflow off the front wing (skip to 40s if you wish):

How on earth do we create a vortex then? Well, it's shown in that video just above, at 50s, but in short - we force air to move quickly from a region of high pressure, to an area of low pressure, around the edge of some sort of angled feature.

You may have seen these things on the top of a few models of Mitsubishi EVO, looking a bit like fangs:



These little fins are vortex generators. They have a slightly different function in that location, and are obviously less aggressive than an F1 front wing, but it's the same idea.

There are tons of studies out there to try and determine the best shape, height, angle, etc which I won't bore you with, but in short - imagine a 'blade' shape, set around 20 degrees from the air flow direction. The air will run into the face that is being presented into the airflow, creating a region of high pressure. On the opposing side, where the air is being blocked, is therefore low pressure.

The high pressure air tries to 'escape' to the area of lowest pressure (imagine blowing up a balloon and letting the neck go - same thing), and thus spills over the top edge of the 'blade', creating a spiral. We have generated a vortex!



On the EVO, this is used to mix low energy air from the boundary layer - about an inch thick layer of stagnant air which is completely stationary at the roof line, and moving slowly up to around an inch from it - with the fast moving, high energy air that is a little further from the car. The spinning action of the vortex drags these two layers together and mixes them.

Air with more energy can then flow down the rear window of the car more closely - reducing drag and lift, and putting more useful air into any rear wing / spoiler that may be down there.

This is the same deal in the image below - the vortex generators ensure the air 'sticks' to the side pod as it flows down towards the back of the car (along the top of the RedBull logo).






So, what on earth does this have to do with the MunteR2? I figure I can generate some vortices and use them to my advantage in a couple of areas:

1) Down the sides of the car, creating a 'curtain' preventing air spilling into the cockpit. I can use some small features - a bit like canards in shape and appearance - to spin a vortex along the top edge of the door panel, pulling air out of the cockpit and shoving it down and along the sides of the car.

2) At the rear of the car - giving the air more energy as it separates from the rear quarters, rear bumper, and rear lights, thus producing a smaller low pressure region immediately behind the car (reduced drag).

3) Down the sides of the floor, attempting to 'seal' the floor with an air curtain in the same way as the Y250 vortex does on an F1 car. Obviously this will never be quite as effective, as the air I'll have to use will not be as 'clean', or as fast, but if I can 'suck' a bit of air out from under the floor (considering which direction the vortex spins in) and make it go down the sides of the car instead, that will improve the efficiency of the floor.

I could add side skirts but as I mentioned before, I want to keep the car looking as 'standard' as possible and carry out these tricks out of sight. Side skirts also add weight and can be clattered off stuff.


There we have it. More stupid stuff to mess about with. Can't wait!

[Jondoeclsm]

How much weight was the screen.
How much benefit?

In too gear ages ago was a car with passenger side covered over. A spare sheet of plywood fitting the gap next to you with enormous holes cut out to leave it as a frame. The holes could be filled with estate agents boards corex board. Fixed when upside down by expanding foam which would encroach onto the hole areas and help keep them from flapping around or worse still, selling a house to somebody trying to drive a car.

[Jondoeclsm]

Cars.
Porsche boxster might be a good one, hence asking about weight.
I have broken a few 944 cabriolets and some of the parts you would sell wouldn't be needed. You can not a car removing the lights (in the case of 944 the pop up ones). Fibreglass panels available as well.

How about removing a screen from a car and leaving the rear screen out? I have a 944 s at the moment with a new screen not fixed in it. I could take the heavy rear lid (almost 30kgs). It just sets off loads of ideas.

[Jondoeclsm]

This guy has done the passenger cover.. https://youtu.be/R0Z9uP7DIJE

[Petrus]

Thanks for the ponderings and explanations Adam.  Aero réally is a huge factor. As I wrote several times earlier in several threads; even in cýcling!!! from some 20 km/h....
LOVE it that you are doing your own thing with it.

Here one of the forum favorite with OEM fitted rear wing for rally use thus none too high speed cornering




Meanwhile faffing with the sway bars and the ongoing project of adding lightness; sent some mails out again about lightweight bonnet/rear lid.

[AdamR28]

How much weight was the screen.
How much benefit?

Can't remember exactly now, but it is earlier in the thread. 20kg maybe?

The benefit for me is the open-ness and improved driving experience. That said, reducing overall height does reduce the 'plane wing' effect that all cars naturally have due to their shape.

You really want me to fit a rear wing don't you Petrus? Haha. I'm afraid that won't be happening on this car.


I spent some time looking at the dirt on the car after Oulton. Found some interesting stuff...

Looks like the little 'shelves' under the headlights are an aero feature that works in conjunction with the front wheel arches. Check out the flow lines here...

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I think my front 'deflectors' are doing more harm than good, causing flow separation down the sides of the car. Lots of randomly flung dirt there, not showing any flow, which means drag.

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Having a nosey at the data again, Munter vs MunteR2, the M2 seems to pull bigger gaps on the straights where there are uphills. On the flat, not so much. So I think there is considerable drag here, and also from the dirty air at the back of the car.

I also looked at the front and rear wheels. I'd mentioned before that I thought the fronts were doing all the braking effort - well, looking again, it appears the rears got to at least the same temperature (if not higher). So why is all the brake dust up front? I think it was being 'sucked' out of the wheel area by those front deflectors:



It appears that air curtains are a modern way to ensure good flow attachment down the sides of a car, so I will add something like in the video below - albeit a bit more crude - where he reports 5% reduced drag:

There is also some interesting flow over the frunk lid - it appears to be kind of acting a bit like a diffuser, with the air 'expanding' the further towards the bottom of the screen it goes. This makes sense as the features running back from the headlights are effectively 'boxing in' that air, and guiding it outwards.

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Towards the back, flow is attaching again before the intake ducts behind the doors.

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And the tape is preventing a 'stall' on the panel gap, which is happening on my daily:

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And there is attachment after the intake duct, too:

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Right at the back, the area of low pressure still remains as the CFD model - this will be a good place for a vent to help 'suck' air out of the wheel well.

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Bad news though - this means I have to clean the car before its next outing! I may make up some DIY flow viz type stuff as well.


I've also been looking at borrowing a McLaren feature for the floor, which is some curved deflectors immediately inboard of the front wheels, kicking air out sideways. I have a feeling these are designed to push away the 'squirt' from the front tyres, leaving smoother airflow under the rest of the car to the diffuser.

[SV-3]

How much weight was the screen.
How much benefit?

Can't remember exactly now, but it is earlier in the thread. 20kg maybe?

The benefit for me is the open-ness and improved driving experience. That said, reducing overall height does reduce the 'plane wing' effect that all cars naturally have due to their shape.

You really want me to fit a rear wing don't you Petrus? Haha. I'm afraid that won't be happening on this car.

Perhaps a luggage rack just for use to and from the track

[Petrus]

Perhaps a luggage rack just for use to and from the track

A tray is a tray is a tray. Make it aero shaped, call it a wing, you can still strap luggage to it ;-)

Concerning the windscreen,  removal reduces the frontal area so the overall drag. It also scuppers the airfoil shape  of the car thus effect thus does away with most of the lift causes by that. Win - win -  win,  with he last one being added lightness :-)

[Joesson]

Perhaps a luggage rack just for use to and from the track

A tray is a tray is a tray. Make it aero shaped, call it a wing, you can still strap luggage to it ;-)

Concerning the windscreen,  removal reduces the frontal area so the overall drag. It also scuppers the airfoil shape  of the car thus effect thus does away with most of the lift causes by that. Win - win -  win,  with he last one being added lightness :-)

Always thought a particular Porsche model featured a picnic table at the rear.

[Joesson]

How much weight was the screen.
How much benefit?

Can't remember exactly now, but it is earlier in the thread. 20kg maybe?

The benefit for me is the open-ness and improved driving experience. That said, reducing overall height does reduce the 'plane wing' effect that all cars naturally have due to their shape.

You really want me to fit a rear wing don't you Petrus? Haha. I'm afraid that won't be happening on this car.

Perhaps a luggage rack just for use to and from the track

At least one member on here has a tyre rack on his engine lid for that purpose.

[Jondoeclsm]

Ok, so the McLaren floor looks like by sweeping the air out to the side, this will leave lower pressure underneath, so down force greater. Also would that less pressure mean any rear underbody components be less draggy?
 
In a way like breast stroke pushing air out sideways to make an easier path for the centre, like Moses in a hurry.

[AdamR28]

Ok, so the McLaren floor looks like by sweeping the air out to the side, this will leave lower pressure underneath, so down force greater. Also would that less pressure mean any rear underbody components be less draggy?
 
In a way like breast stroke pushing air out sideways to make an easier path for the centre, like Moses in a hurry.

The Moses underfloor. I like it! I'm going to borrow that one

Regarding the McLaren 'sweepers', I think it is more complicated than we know.

There's going to be vortices spilling off the sweepers, and these will in fact be rotating in the 'wrong' direction, sucking air in under the floor from down the sides of the car, interestingly. However I assume they have tested this and the effect is less than the gain made by keeping the dirty air out, that would otherwise be under the floor if they weren't present. At least a vortex is highly energetic, flowing well over whatever surfaces it hits - compared with turbulent air which isn't, stalling and sticking to said surfaces.

Regarding reduced drag from lower pressure - I'm not sure on this one, but I will take a stab. Remembering that low pressure under the car is usually created by higher speed of air (Bernoulli principle), this means the air has the same amount of energy either way - either faster but with low pressure, or slower with higher pressure. So my best guess is that it makes no difference, and any 'features' under the car against which the air can act are generally bad news for drag.

On a similar note, watching a Kyle.Engineers (YouTube) video about canards the other day was interesting. It stated that they were poor in terms of absolute lift/drag values (which I knew), but going on to explain why made perfect sense.

The top surface of the canard has high pressure acting upon it. The angle of the surface is usually quite high - say 30 degrees. If you split the force down into vectors (and simplify a bit!), there is a vertical downwards force, but also a horizontal force acting backwards on the canard / car = drag.

The same happens on the underside - which is in low pressure. The low pressure amount can be as much as the high pressure above (again simplified). This 'suction' from the low pressure underneath has exactly the same effect as the high pressure on the top side, just reversed - it now 'sucks' the canard downwards (downforce), but also tries to pull it backwards = more drag.

You can apply this to any part of the car - high pressure on the front of something pushes it back, AND the resultant low pressure behind it also sucks it backwards. Double whammy.

[Petrus]

The Moses underfloor.

My previous car was a proper 4x4 ragtop. Looked rather agressive ánd had bullet holes.
We dubbed it Moses´s car because in the city people may way for it :-)
Swith on the indicators, count to 5 and simply go. Ok, I díd look first, but that was courtesy ;-)

The MR2 seems to be invisible. The no-muffler is an essential active safety device.

[AdamR28]

Long time, no update!

Track days now open again, and having shared the original Munter with @Maurici
at Oulton Park this week (thanks mate!) I'm very much looking forward to the 'return leg' at Cadwell Park this coming Thursday.

A few pics from Oulton first...

The Munter in all its glory.

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Forgot a spoon for my lunch, so the lesser spotted 22mm spanner and some tape was employed.

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Wore out some brake pads a bit too much...

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And watched a 458 set on fire.

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Anyway, with Cadwell looming I thought it was about time to start tackling the todo list.

I had a GRP diffuser lined up, but that didn't happen in the end, so set to with some ali sheets to make this monstrosity. Went full Time Attack for shits n giggles.

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Supports courtesy of some brackets removed from an IBC that I'm currently converting into a wood fired hot tub. Fred Dibnah would be proud.

Full pikey mode for the newly adjustable rear ARB.

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And a new deflector for the front duct, hoping it'll make the cockpit a bit less buffety.

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Still a few more bits to do, but the diffuser was the main job after the first outing many months ago.