MGB Aerodynamics. Will this work?

v8bloke · August 11, 2012, 09:38:46 AM

Hello All,
I have been doing more modifications to my 4.8L MGB GT V8, Road and trackday car. I couldnt find any details of someone adding a fully functional rear wing to an MGB in the net so have just jumped in at the deep end with my design.
Here are some photos would appreciate some feedback as to what you guys think.
So far have only driven on the highway upto about 80mph and it seems very stable. I now need to try it on track.
To complement the wing I am also fitting a front splitter that will extend back as far as the front crossmember.

Cheers

Mark

Jim Stabe · August 11, 2012, 10:56:13 AM

Whether it works or not, it looks mean. You should contact Jim Blackwood, he has a wing on the back of his car but his is a roadster. As thorough as Jim is I'm sure he has lots of data on his wing.

Moderator · August 11, 2012, 11:50:19 AM

I always enjoy seeing photos of your car! (We need to get your page of the Photo Gallery updated to show your work properly.)

I'm enthusiastic about your idea of adding a splitter. The benefit should be substantial. Will you use it around town, or just for track days? If it's strictly for track days, maybe you can set it lower and extend it outward to front and sides further.

There are two winged MGBs on this site: Jim Blackwood's MGB and Phil's Leonard's RV8 racecar. I don't recall seeing any measurements of how well those wings work. It would be very interesting to put load cells under the mounts to see how much downforce is created. Of course lap times are the real measure of success.

Please keep us posted as you evaluate these concepts!

Preform Resources · August 11, 2012, 03:51:18 PM

The larger the front splitter, the more wing you will need to balance the car out, the more angle of attack the more drag,
it's a tradeoff.
Dave

Bill Young · August 11, 2012, 11:39:32 PM

The last couple of races we've been running Phil's RV8 without the wing and doing quite well. We may need the additional downforce with a stronger engine, but for now it's pretty well balanced as it is without.

v8bloke · August 12, 2012, 04:55:30 AM

Thanks guys, I am really looking forward to experimenting with the new setup. Anyone who has seen my videos on youtube (v8bloke) will see that I have always been battling with oversteer so I am hoping the wing will help reduce this.
It will also be interesting to see how much straight line speed will be reduced by the extra drag.
To try and see what the airflow is doing I am going to attach some 5ft lengths of thin fabric ribbon to the top of the windscreen so they trail back over/under the wing. Then using my Gopro and suction mount attached to the roof drive at varying speeds to film how the ribbons trail. Dont know if it will work but worth a try!
Next trackday is on the Silverstone GP track on 2nd Sept so will post the findings.

Cheers

Mark

DC Townsend · August 12, 2012, 07:40:33 AM

You might also take a look at Mike Sawatsky's (spelling?) heavily modified BGT track only car. He's running both a splitter and a wing and has been very detailed in his experiments with both. He has several threads on this board and at least one over on BritishV8. Might be worth a look.

Moderator · August 12, 2012, 10:52:26 AM

Mark Sawatsky's MGB-GT Racecar Build Thread: <a href="http://forum.britishv8.org/read.php?13,18284">part 1</a>, <a href="http://forum.britishv8.org/read.php?13,23257">part 2</a>, and <a href="http://forum.britishv8.org/read.php?13,31745">part 3</a>. (I think the aerodynamic stuff is mostly in part 2.)

v8bloke · August 13, 2012, 08:17:19 AM

Thanks
Looking forward to some testing. The good thing is that I can remove the wing easily for comparisons.

Mark

burner1 · August 13, 2012, 11:09:40 AM

I had thought about testing different aerodynamic effects such as this. It would be real easy to hook p a potentiometer to measure suspension deflection at speed. You could run with and without and measure how much the suspension changes with each.

Preform Resources · August 13, 2012, 04:18:47 PM

mark,the tuft testing should be very revealing if you can get adequate pics ,can you move the wing up and down ? then you can
see where it is most effective without running the wing at a severe angle of attack (AOA) minimizing drag, also you can see the effect of downwash off the back of the wing. If you run a front splitter with the flat bottom going back as far as poss. it WILL
create down force, contributing to the already poor weight distrbution and if you run the wing at an exagerated AOA you will get the resultant drag,, maybe just try a few tricks with the rear wing and your existing front air dam, see how that feels,of that and as Gary says with the capability to measure true deflection would be the icing on the cake.
Dave

burner1 · August 13, 2012, 04:30:16 PM

With the Arduino it would be very easy to hook up an LCD and a potentiometer (and a whole lot more).

http://arduino.cc/playground/Learning/SerialLCD

http://www.arduino.cc/en/Tutorial/Potentiometer

Moderator · August 13, 2012, 05:01:54 PM

Quote...contributing to the already poor weight distribution...

Mine measures about 49/51... Mark's can't be too far off that. Is that poor? What's the target then?

v8bloke · August 13, 2012, 05:49:43 PM

wow this is getting interesting.
mine is 52/48 F/R i thought that was quite good.

Preform Resources · August 13, 2012, 09:18:55 PM

Those ARE good numbers, better than I thought,(obviously) the other, generally still applies however.
Dave

Todd McCreary · August 17, 2012, 08:32:13 AM

50 / 50 weight distribution is the optimal split for a front engine - rear drive car. it's not unusual for FWD cars to be over 60% on the front axle ... but then, their rear tires aren't doing a whole heck of a lot.

mine is 52/48 F/R i thought that was quite good.

and it IS pretty good. anything better than 55 / 45 is getting towards purpose built race car territory. it's normally kind of hard to get that much balance out of most cars because there's often a significant portion of the engine which sits forward of the center line of the front suspension.

Here are some photos would appreciate some feedback as to what you guys think.

you remember the Dodge Daytona / Plymouth Roadrunner from 1970?

it became somewhat of an "open secret" ( because the design got outlawed, so the engineer and aero guys didn't mind talking about it ) that the designers considered the UPRIGHTS to be almost more important than the wing itself. they acted as high speed stabilizers, just like you see on an airplane.

you can see some vestiges of this thought process on Cup cars today with the 'shark fin' that runs down the drivers side of the car..

as such, if you spend much time over 100mph you may want to consider full body uprights rather than those weight savers you're running now.

BlownMGB-V8 · August 17, 2012, 11:38:46 AM

Aircraft Spruce and Specialty sells airfoil shaped aluminum struts. That is what I used.

Jim

Preform Resources · August 19, 2012, 08:09:53 PM

The cup cars are using this splitter effect trying which keep the air flow on the sides or deck,, the sharp edges create vortices which aid in that effect.
Dave

v8bloke · September 02, 2012, 05:37:12 PM

The new wing and splitter have had their first test.
Definateley reduced oversteer in fast turns.
http://www.youtube.com/watch?v=HnDjFI_m5i8&feature=plcp

Todd McCreary · September 02, 2012, 07:56:05 PM

Heh. I do believe I see a spinner at 1:10.

That's amazing how you're *murdering* that Evo in the corners. Is he running stock rubber?

It sounded like you're geared just a little short for the front stretch on that one dry pass near the end when you were pursuing. You ditch your passenger and I'm sure that will come into play a lot more often.

v8bloke · September 04, 2012, 05:21:50 PM

Todd
I believe he was using Toyo R888 tyres.
I much prefer not having a passenger.

Very happy with the aero upgrades. Just need to experiment with angles.

Mark

v8bloke · October 14, 2012, 03:20:18 PM

Hello again all.
Well, it would seem that the rear wing is producing quite a lot of downforce. I know this because my exhaust is grounding at high speed (130mph+) over slight undulations which it never did before.
I have had an idea that almost seems too simple, but I think could work to reduce drag at high speed.
Just to recap the car is a road legal MGB GT V8 4.8 which is modified for trackdays not racing.
I have been experimenting and found the best angle for maximum downforce and the best angle for minimum drag. The virtical
distance between the rear wing mounting hole for both these setting is less than 30mm.
I was wondering if I could use a strong spring for the rear wing mount each side that would compress at high speed/downforce (80mph+) so giving maximum effect at lower speeds but less effect and less drag at high speed.
it would take a bit of trial end error to get the spring rate right and I could use my Gopro camera too see what is going on. Also I could factor in adjustable stops to set maximum and minimum angle.
How stupid is this? as it seems just too simple.

Mark

Preform Resources · October 14, 2012, 05:28:54 PM

Mark, the super modifieds like those in the picture do the very thing you're talking about, I've never looked at one up close to see how they manage the up and down movement , but the wings definately flatten out at speed and come back up on deceleration. these cars run big V8 engines and are direct drive ( in/out box),, oh yeah,,,, they ARE roundy round cars.
Dave

v8bloke · October 15, 2012, 06:36:25 AM

Thanks Dave
I like a challenge
Now I have come up with a linkage that will effectiveley soften the spring after the initial 20mm of movement.
It will take a while but I will post up the vid hopefully of the linkage in action.

Mark

BlownMGB-V8 · October 15, 2012, 12:14:31 PM

They use "wing cylinders" and you can see them in the photo. There is a controller for it in the cockpit so the driver can adjust it, I think it is some sort of brake cylinder. I am considering the use of these on my wing but will be tying it to the suspension so it works like the mechanical linkage I had before the IRS. Common sizes are 8", 10" and12" travel. I have not seen anything shorter. Speedway sells a hydraulic cylinder now but it is not available in the 8" size. Diameter is 1-1/4". Cost about $140 each. If I use these I will need suspension cylinders with about a 3/4" bore and 4-1/2" of travel. This system holds the ride height constant by applying more downforce if the body lifts.

Jim