Dedicated Track Car Progress Thread

[trublustu]

As well as my little engine bay play, I`ve also worked on the aerodynamics of the car while it`s been off the road.
Now, creating downforce is no problem. just bolt on a huge wing and away you go.
This has a downside, drag!!

The Puma, for all it`s qualities in the twisty bits, suffers a little along the straights from lack of pure grunt.
So I have been looking into ways of creating extra grip without extra drag, No mean feat.

But I have come up with something of a solution.
At this years Fordfair I got to meet and chat with forum member, Sjoerd (and have a good look at his car) As some of you may know he has done a lot of very clever investigation in this field. And has plumbed for a gurney flap.
These things tick all the boxes, very little drag for significant downforce.
I recon our cars don`t actually need that much extra downforce at the rear as they handle so well already, but a bit more can`t be bad.
So I set out to find one. not easy I assure you.
In the end I found a company selling BMW saloon boot spoilers, which turned out to be exactly what I wanted.
after a few emails I arranged a custom length to be supplied (Beemer ones would have been too short) and have set about fitting it this weekend as well as a bit more smoothing out on the body.
This is what I have ended up with. I`ll let you all know how it performs (whether it makes any difference!) after Cadwell.

Gurney Flap1

• trublustu
• Oct 12, 2014

Gurney Flap2

• trublustu
• Oct 12, 2014

Gurney Flap3

• trublustu
• Oct 12, 2014

 

[grayfox]

"The Gurney flap increases the maximum lift coefficient (CL,max) decreases the angle of attack for zero lift (α0) and increases the nosedown pitching moment (CM) which is consistent with an increase in camber of the airfoil"

.... well durr obviously :-D

 

[trublustu]

Clear as mud... :?

Proof of the pudding will be known Saturday. :thumbs:

 

[Noobrider]

lol, every little helps - I have the samp strut brace and its putting me off fitting my Mondeo V6 servo and master cylinder as it wont go back on if I do.

 

[stephengreen]

Been looking into guerney flaps too. I'd come to the conclusion that they only work when attached to the trailing edge of a wing. And on that assumption bought an evo wing to attach one to at a later date. The problem, as I rightly or wrongly see it, is that the air flow detaches from the car at the rear screen. That's why the evo and f2 wings sit so high for it to reattach to as it flows over the roof. Your thought processes for improving the car are eireely similar to ours. Will be interested in your opinion of the result of your solution after your Cadwell outing. Top work

 

[trublustu]

Hi Stephen.
Have you seen the initial design for the Puma?
Its shown in the "inside story" booklet which covers the Pumas development.
The early design had a really low boot lid, which was redesigned to incorperate a "wing" into the bootlid as the rear end was deemed to not have enough stability.
Ford never offered a spoiler option, which is not like them.
You are quite right that for a wing (not spoiler) to work it needs clean air, on our cars that's either at the top of the window or high above the bootlid. such as the rally car and evo wings.
The airflow does separate from the rear window but is sucked back down to the bootlid which is the theory I'm hoping will work on my little track toy...

 

[Ziggy]

The rally cars also used a deep front diffuser and sump guard which reduced lift on the front as well - keeping everything in balance.

Reduced lift just on the back will in effect increase lift / understeer on the front - hardly ideal when its a FWD car. For track use you want the back end "loose" anyway to lessen the effects of understeer.

 

[stephengreen]

http://www.jerryolsondesigns.com/fordorphans/images-Puma/Puma-Windtunnel-35-w.jpg" onclick="window.open(this.href);return false;
This picture shows why maybe the evo and f2 so high
And I think that I'm right in saying that the rear wing and or guerny flap is in conjunction with a splitter.

 

[trublustu]

Hi ziggy, I will be replacing the splitter which I recently went ploughing with (not before Cadwell though), I also have plans to build some kind of diffuser too, all to help with downforce.
I actually like my car to run quite neutral and the loose back end thing is not really my cup of tea.
Thats a really interesting pic stephen, got any others? I see what you mean about the airflow but it cant be a vacuum there, it must pull air in from around the top of the sides (if that makes sense)
I`m doing all this by guesswork and trial and error... :roll:

 

[stephengreen]

Yes Stu, it is a vacuum. The car creates a hole faster than it can fill back in. This has two effects. A low pressure area created by the vacuum which creates lift. And drag caused by the turbulence of the air trying to fill the space created, back in. In theory the evo and f2 wing harness the airflow seen in the picture as it detaches the roof, but also re attach the airflow to the boot as it flows under the wing thereby reducing drag.

 

[trublustu]

Is this why a diffuser is so effective, sucking air out from under the car to fill the area of low pressure.
In which case, its a definite job for over the winter...

 

[stephengreen]

From my miniscule understanding a diffuser increases the surface area, allowing the air to expand, therefore creating low pressure and therefore downforce. Most manufacturers take advantage of this phenomenon by introducing rake in the ride height of their cars. The puma is no exception. Its normal ride height is some 35mm higher at the rear than the front. Air traveling under the car reaches this larger area at the rear, expands into it causing lower pressure and therefore less lift.

 

[trublustu]

That's about how I see it, airflow underneath the car need managing and a splitter helps enormously.
Side skirts and spats are more than just styling features when used properly.

 

[trublustu]

Great day at Cadwell

cadwell 17.10.14 at lunch 2

• trublustu
• Oct 18, 2014

cadwell 17.10.14 at lunch 1

• trublustu
• Oct 18, 2014

Finally got to put my spannering to test, and can confirm that everything worked as I`d hoped

The removal of pumps from the aux belt run and weight saving really gave me more zip than I`ve had before. Very happy to be faster (for free)
The steering took a little getting used to but was phenomenal!!! The feedback was real old school and I could drive right on the edge and just hold it where I wanted. bloody stiff around the paddock though, but thats a fair tradeoff!
The brakes also had a lot more feel.

Its as if I`ve taken back some of the control of the vehicle that the ecu does for you on modern cars.

I`ll be selling the top strut brace as handling was fine without.
Two things I do need, Coilovers (its sitting real high) and my splitter back (missing some front downforce)
The rear stability seemed better than it was, I couldnt even get the back out when i tried!

 

[ArtfulHussy]

Stuuuuu.. Empty your pm folder!?

 

[Scott134]

I want one of those spoilers ... Just because it looks cool!!

 

[trublustu]

A couple of people have contacted me regarding the gurney flap/spoiler, asking where to get one.
I found mine on fleabay, being advertised as a `universal boot spoiler` for bmw and audi saloons.
There a a couple of traders selling them. Theyre about £20-£25
this is the sort of thing.. http://www.ebay.co.uk/itm/1-5-M-Carbon-Fiber-Spoiler-Rubber-Body-Kit-Trim-Sticker-Pattern-Car-Universal-/401225366521?fits=Model%3ASaloon&epid=2063467761&hash=item5d6ae53bf9:g:FLsAAOSwal5YKSsR
*updated link 06/17.

Now the ones being flogged on ebay are a bit short for our curved bootlid! So anyone wanting one will need to order a custom length (I think the off the shelf ones are 115cm. we need about 126cm)
I emailed a nice lady called Vicky at [email protected] asking for a 130cm length. which was supplied without fuss.

The spoiler in the new link appears to be plenty long enough off the shelf. :grin:

Fitting is a bit fiddly as they are straight and need a little gentle heat to make them pliable. Then they just stick down.

As for car progress...
since Blyton in November its been wrapped up..
I`m off work next week so I will be giving it a once over and making a new `to-do`list for before Oulton in Febuary :grin:

 

[grayfox]

I randomly searched for Gurney flap yesterday on the bay and saw one for an E46 BMW being auctioned for a fiver new so bagged it, was thinking of attaching it along the top of the rear screen as mentioned the cleanest airs here but unsure if it would be any more effective than at the edge of the wing as its position is more towards the rear wheels? And also I'm not sure how the air will effect the wing afterwards, could be interesting.

 

[ArtfulHussy]

Has anyone tried a roof spoiler to "pull" the air down underneath it towards the boot? I've seen them advertised (chuffing ugly things) but wonder if there is any merit there in terms of directing the air towards to boot lip more.

Sorry, don't want to hijack your thread! I can move this somewhere else of you wish? Was just while we were on the subject here.

 

[grayfox]

Has anyone tried a roof spoiler to "pull" the air down underneath it towards the boot? I've seen them advertised (chuffing ugly things) but wonder if there is any merit there in terms of directing the air towards to boot lip more.

Sorry, don't want to hijack your thread! I can move this somewhere else of you wish? Was just while we were on the subject here.

This is what I'm getting at above, would hope this would happen as the airfoil travels passed the guerny (plus recieve the downforce on it itself)

Make sure you let us know what you get up in preperation for Oulton Stu!