MR2 rear wing - keep or lose?
 

I have just bought a MR2 mk2 with a dead engine to convert to electric.

It has a big wing on the back which I am sure did something for the styling back in 1991 and may have had an effect at some speeds but for my EV I want good aerodynamics.

So, should I keep or remove the wing?
Does anyone know what sort of difference it makes to the aerodynamic drag?

http://i5.photobucket.com/albums/y17...20EV/MR210.jpg
http://i5.photobucket.com/albums/y17...20EV/MR209.jpg

Thanks.

As far as the wing, it looks as if it is just there to create downforce.
Eventhough it looks awesome, I would remove it.

The side butresses behind the back window would make excellent mounting points for a piece of clear lexan. ( Since you no longer have to vent the heat from the ICE. )

Nice car. This is going to be one interesting EV !

One more thing : you are going to replace the wheels right ? ( They look great, but really stir up the air. )

Looks useless. With the notchback instead of a hatch, I doubt the MR2 creates lift back there that needs to be cancelled.

I don't think it would be worth changing wheels. What is he gonna do, put steelies on a sports car? Then again there may be some more aerodynamic alloys out there.

It's not purely cosmetic, so I'd leave it. Downforce at speed is a good thing, if you're thinking about stability. Your wing's shape actually will produce a bit of lift reduction.

It does add a slight degree of drag, but removing it will probably give you (just a guess) maybe a quarter of a mile per gallon extra, but you'll feel a little looser going down the freeway. Not good if you need to swerve to avoid an accident.

If you're going to electric, definitely keep it, because there's no MPGs to worry about.

I'd LOVE to have a car like that.

It might actually make control worse at high speed, by reducing force on the front tires. Look how far back the wing is. And it's already pretty light in front.

Yeah, actually, there are MPG's to worry about when you're going electric. You're still getting charged for the "fuel" as it were, and there is still pollution that is a part of your vehicle, which comes directly from the use of your vehicle's "fuel".

That wing will do just about nothing, at any speed that the average EV will travel. Chances are, if he's doing a conversion like most of the other ones on this site, and most @home conversions in general, he's not going to even be doing 60 MPH.

While I'm sure you have unlimited knowledge about exactly how a wing-type spoiler will hamper/degrade fuel efficiency, the minimal effect on economy that you claim that spoiler will have, is the same minimal effect on downforce at road speeds that it will have.

Include the fact that as an EV, that car will weigh ~150% of what it weighs now, and the aerodynamic downforce you allude to is of no consequence. If that wing can create 50% of the car's weight in downforce at 60MPH, it's creating a HUGE amount of drag as well.

It's simply not going to be necessary once he converts to EV, and it was never necessary with the gas engine, either, unless the operator were driving illegally.

It's not nearly far back enough to have a lever/fulcrum effect on the front. The MR2 is a mid-engine, rear drive car, so the back end is going to have more weight. Intertia dictates that the greater the mass, the more it resists change. Rear-heavy cars will tend to oversteer, meaning the back end will want to switch with the front when traction is lost (from slippery roads, for example). The same goes with front-engine, front wheel drive cars. They tend to understeer from the weight balance being in the front (except during high-speed corners while braking. The lighter rear plus braking will lead to rear-wheel traction loss, resulting in brake-induced oversteer, but it won't try to spin you around like a top.).

There's no call to be rude.

Not if you've got a solar-powered charger. :)

You don't consider it rude to speak as though you are an authority on a subject, even though you don't have any references or real experience in the field to back you up?


What do you think it took to make that solar powered charger?

Also, how much money would you like to spend on a budget EV conversion? (I realize the OP never said it was a "budget" conversion, but the assumption can be made based on the majority of users here and elsewhere that have done similar projects.) Whole house sets run about 30k installed, one just to charge a car would probably net at least $4k, and would be a waste of resources. It would never pay itself off.

The carbon payoff for solar panels (depending on how long they last, the amount of power they produce, and where they were made) is actually more than their expected usable life span.

At current prices, they'll pay themselves off in electric bill savings in something like 30 years... more than they'll actually last for.

In case you'd like to research before you rebut:
http://www.google.com/url?sa=t&sourc...ZXzgwR9_1ciCeg

http://www.google.com/url?sa=t&sourc...2oEHUTRNYaf7tA

http://www.google.com/url?sa=t&sourc...nNC3nIS_eSevoQ

http://www.google.com/url?sa=t&sourc...SeHrc32cyMRy5A

The MR2 will not necessarily have more weight in the rear, and being a sports car, it's closer to 50/50 front/rear bias. *I actually think it's 42/58 F/R*. In fact, having driven several MR2's, both first and second gens, I can personally say that they're extremely neutral (moreso than most other cars I've driven) while going down the road. They're certainly more stable than V6 Fieros.

Please start a build log! I love reading about EV conversions, since I can't have one for myself.

Hi,

If you look at the wings on race cars, you'll see that they can develop down force -- but this always adds drag. Wings on street cars are superficial -- they cannot develop very much downforce if any; and they still always add drag.

Dump the "wing" thing... Drag is bad.

Hi Mate, great to see someone else in the northwest! I'd ditch the wing as above 'drag is bad' the bog standard 2.0 doesn't run a wing so the car will be safe without. depending where you're going to put them between the cab and rear axle you shoul improve the neutrality of the chassis. I'd suggest putting a couple of cells in the spare tyre well over the front axle as it will help keep the weight there too. and unlike some mid engined cars petrol cars with a front gas tank the front won't go lighter as the tank empties.

OK, a good range of replies there.

I do like the look of the wing, I must admit, and removing it will leave holes in the body work including a big one where the body of the electric aerial sits.
However, I've been told that I could sell it for £100 and that would return 25% of the cost of the car. But then there is the cost of the respray to add to the cost of the conversion if I start doing body work.

OK, what I will do is to leave the wing for the time being and wait until it is running. I will then try my set commute with and without (with the holes taped over) to see who is right about the drag at 60mph.;)

There will be a load of LiFePO4 batteries up front in place of the spare, eventually, so I am hoping that will add weight to the front end. Equally there will be a load of batteries under the boot behind the rear wheels too as well as over the motor.

I have been thinking of changing the wheels, again to recover some of the cost. I could offer them to the owners club in exchange for a set of standard alloys and some cash. Or I could make up a set of 50's style aluminium moon disks to cover them.:D

I have a project thread here on the diyelectriccar.com forum if you want to follow it to see how I got to where I am now.

Robchalmers, where abouts are you? I'm in Eccles.

What kind of holes will it leave? If they're just little circles you can plug them

just north of warrington. where are you getting your liFe's from??

Most of the holes will be screw holes of about 4-5mm diameter but there will be one big one that may be 50+mm that may also be rough cut to allow an aerial to be pushed through to mount on the plastic wing side bit.

You're not far from me!

I don't know yet. I figured that the conversion will take a while so by the time I am ready new sources may spring to attention. It is likely that I will import from China either on my own or as a group purchase. A chap on the Battery Vehicle Society forum recently imported a small 24V pack for his bike as a trial to see how the import process works and to see if the goods were up to spec. So far so good.

I am currently using the Thundersky specs to determine physical size and possible cell capacity to work out range and how many cells I may be able to afford and fit in the car.

No doubt they will be cheaper and easier to get in 12 months time.

The only value in your wing is on eBay, where some idiot will pay you big bucks for it so he can think he's Jimmy Johnson.

Who brain washed Hermie at birth?

If it has worked I have a link in my sig to my conversion project.

Thanks!

i think you'll have to do some a-b-a. mileage or tuft testing

because of the shape of your car, it might react differently than anyone might expect. your rear window is near vertical. might have a recirculating bubble in there that is kinda protected by the spoiler. or maybe the spoiler is nothing but a big sail... either way, an abnormal result good or bad wouldnt surprise me

Christ and Hermie,
I think I have an easy way to aid in solving this disagreement. First, was a spoiler standard equipment or was it an option? Or perhaps this spoiler was an after-market add-on? If every single stock MR2 has a spoiler, it is possible that there was an engineering reason for it. However, if this spoiler was an after-market job, then it is almost certainly to be more fashion statement than safety or handling requirement.

Still, I've come across a relative few situations where a spoiler produced a measurable improvement in safe handling at normal highway speeds.

woodsmith -

How about the following :

http://ecomodder.com/forum/member-cf...-kamm-back.jpg

1 - Take off the horizontal part.
2 - Use the sides as framework for a Kamm-Back.
3 - Spend lots of time and effort making it reversible (this is optional).

Benefits :
- Kamm Back may improve range
- Reversible in case you want to return to the OEM look

Problems :
- Won't make any money selling the spoiler
- Maybe a lot of effort that won't pay off (depends on your POV)

CarloSW2

Has everybody forgotten our spoiler guidelines?

It's pretty safe to say, spoilers increase drag unless they take the form of a surface "extension".

I suppose there could be the exception that proves the rule...

Me, I'd leave it until I see how fast my EV goes and/or decide if I like how it looks.

wing
 

I vote lose it.

This spoiler is an aftermarket one to replace the one that was on the car. I have yet to see an MR2 without a spoiler at all and that could just be down to the usual types of owner prefering a spoiler or wing of any description as well as the factory fit option.

I like that idea but not sure about the amount of body work involved to get it to look and act right not how the insurance company and the IVA will treat it.

I would probably only go as far as blanking off redundent vents and holes and maybe covering over the rear wheel arches.

Is this even a stock spoiler? I don't think I've ever seen an MR2 with one of those.

winkosmosis -

My picture shows the OEM spoiler. I think the sides are OEM, and they just swapped out the horizontal part. If you look at the rear picture, I think you can see that it looks a little "incongruous" in the way it curves.

CarloSW2

A fellow MR2 owner here. The wing is definitely not stock on your car, woodsmith, but the sides are. From what I've experienced, if you don't want to remove the wing because of the holes, but don't want to keep your current spoiler for drag reasons, find a stock one. The wind barely hits it (rain drops and especially snow sit on mine even at 60mph). Just for reference, but there were MR2s without spoilers available, as there are used OEM trunk lids out there without holes in them.

As far as the rest of the car, there are 2 major aerodynamic issues:

1: The rear, especially where the back window and engine lid are. There is very little flow up through the vents in the lid, so the air from above just dips in and slowly swirls around in that area (causing annoying water spots after it rains, since the water just sits there). That's why the air never really reaches the spoiler in the intended fashion. Add a vented lexan panel over that area (add venturi tabs at the end of the roof for bonus points!), and you'll probably see enough airflow at the spoiler to start thinking about removing the spoiler.

2. The front end. Since it's a mid engine car, the air basically flows through the radiator and slams against the front trunk firewall, then gets shoved almost straight downward, instead of flowing through the engine bay to the back. That, coupled with overall poor stock underbody aerodynamics, can actually create lift at high speeds from all the turbulence. Many people have complained about that throughout the years, a feeling of the front feeling floaty and disconnected on the freeway. The car can definitely benefit from a front and rear end underpanel to smooth things out. There are also what are known in the MR2 community as "Speed Flaps". They were available on MR2s in Japan, but never made it over here. They're the deflectors that you see under many cars today in front of the front wheels. They significantly reduce front end lift at high speeds. You can find replicas at Brady Motorsports.

As far as the radiator, if you're looking to sink some cash into this, you can tilt the radiator forward, cut a hole in the hood (or get a vented aftermarket hood), and vent the passing air out over the hood. That's the most aerodynamic way, and will significantly improve the front end's faults. A company called Border even sells a conversion kit.

Beyond those two issues, there really aren't any other unique problems as far as aerodynamics. The usual mods shown on this site will work, though they won't make your car look any prettier. ;) Check out MR2OC.com, the biggest MR2 site out there. You need to register first to view anything, but there's a wealth of information on anything MR2 related you need.

The radiator conversion is pretty awesome. I'm surprised enough people do that aeromod that there's a kit.

Cheers Blue,
The car is a Japanese import so it has all the underbody panels.

I am doing an electric conversion on it so engine and radiator airflow won't be needed, I just need to keep the controller and the motor cool.

I will block off the holes in the nose cone and see what I can do with the area above the engine cover. If I can change teh spoiler for a smaller one then I will do that. I am on the UK MR2 owners club forum so I will see how much of the ICE and parts Ic an sell on and see if I can trade the spoiler too.

Thanks.

Late to the party, but I also would have said "lose that aftermarket spoiler" to reduce drag.

There's a chance the OEM spoiler may have reduced both rear lift and drag compared to the "base" car that had none. It'd be useful to know if Cd figures are available for the two versions (turbo and non-turbo versions, if I'm not mistaken).

As for noticing a difference in driving once the conversion is done, I'm afraid you won't be able to conclusively / reliably say whether it helps or hurts your energy consumption in regular use - likely way too many variables to eke out the effect of a single mod (unless it's utterly massive).

You'll have to do something a little more methodical, such as repeated coast-down testing from high speed, or terminal velocity / average speed testing on a steep, long hill.

I could ask the same of you. :)



Contradictory, don't you think? Especially since even a BMW front-engine, rear drive has a front/rear bias of around 52/48 F/R, and they even put the battery in the trunk to improve wieght bias and design their cars to have zero-lift aerodynamics.

The engine is the heaviest thing in the car. Obviously, unless you're doing a LOT of work to counter it, wherever the engine sits is going to be the heavier side. Common sense, dude.

maybe just "chop" the wing and use it for a mounting bracket....
 

:rolleyes: