Easy Aerodynamic Wins? - Time Trial

[mcerbm]

I have a DVA tweaked Superlight R which I will be competing in a time attack style championship run at knockhill. Its based on power to weight (wheel horsepower vs weight with me in the car). I did a few rounds last year and I was up against quite a variety of cars. As you would imagine the caterhams strengths were in cornering and braking. 

Peak speeds unfortunately were lacking! I was peaking at 118mph GPS, some of the competitors (tuned impreza's / evo's, porsche 911 (997) turbo S, VXR race car, VW corrado race car, Ultima GTR) were adding 15-18mph over me.

I am running in the road class sub section of the class with the 911 / ultima GTR) road car hill climb MSA blue book rules apply.

The events I did I ran the car with a caterham wind deflector, half tunneau on passenger side, everything else standard.

So far over the winter I have:

• Added a half door on drivers side
• Reduced headlight size to 5-3/4"
• Added lower headlight bracket (the type on sale on blatchat which are lower than caterhams)
• Added a race undertray for front section of engine bay

I'm thinking of adding race wingstays and trying csr front wings.

Does anyone have info on any other aero options I have available? Also does anyone have experience of before and after improvements using anything listed above?

I know its not easy making a caterham more aerodynamic, but even a couple of mph extra more lets me use my advantages elsewhere on the lap.

[Julian H]

I'd say the sort of differences you are talking about are fairly minor so unless you are doing it for "self-satisfaction" rather than performance, you are probably better considering spending the money on training the nut behind the wheel?

[OliverSedlacek]

I would actually say that starting from a low baseline like the Seven, quite a lot of gains can be made. The trouble is that aerodynamics is a pretty tricky subject, and I've yet to see any beginner's guide to modifying a Seven.

From what you say about the nature of the competition, drag reduction is your priority as you don't really need any downforce. One of the biggest contributions comes from the open front wheels, which is why the F1 boys spend countless hours in the windtunnel studying front wings, noses and turning vanes. These are all targeted at persuading the air to flow between, around or over the front wheels. As much as the rules allow, I would look at enclosing the front wheels as IMO this would give substantial gains.

Flow through the radiator and engine compartment could also be improved. If you look at the Lotus Elite (the original 1950's one) or the Lotus 11 you can see how small an air intake you actually need. A lower engine cover will certainly be a useful item to control the airflow in this area, and I'm guessing you wont have any overheating problems during a sprint duration competition.

[mcerbm]

I probably should of mentioned that due to being in the road going class I dont think I can use anything other than parts caterham offer as standard from the factory.

Julian, I have been studying the vbox data from the previous events with all the practice session laps / qualifying etc and I record gopro footage and overlay the data to try and see why certain sectors are better than others. I will be using the vbox sport app with the delta showing this season. I take your point on improving the driver, I have had tuition in the past and it does help.

In last years event there was 3 of us that finished within 0.17 secs of each other at the top of the group over a 57 second lap. Its really tight so i'm looking to improve in all areas, but the aero was an obvious one. I touch circa 118mph twice in a lap (varies 1-2mph depending on exit speed) so the mods I made over the winter plus possible planned ones my have moved me from 3rd to 1st in that one instance.

Unfortunately I wont be able to do a pre / post improvement comparison as my Avon ZZR (soft) is no longer viable which will lower exit speeds onto straights and my car's cam timing was out, so now that its sorted I have more whp.

Ideally I would of used vbox data to feed some info back onto blat chat as the archives have a lot of suggested improvements, links to the MIRA wind tunnel article / black brick etc, but not much in the way of  I did X mph on X circuit pre mod, now I do Xmph more.

[mcerbm]

/sites/default/files/images/users/1260/IMG_6104.jpg

an example of the larger headlight from last year, to the smaller 5-3/4" with lowered bracket for this season. Thats hopefully a reasonable reduction in frontal area.

[Julian H]

In my [very limited] experience of track driving I think the biggest wins are to be gained from knowing how to and where to brake to maximum effect and cornering and exit speed. My mate had a K Elise 126? bhp stock against my 140K Seven. He is a lot more experienced driver than me but I was still all over him in the under braking, through the corners and exit speed but even with his paltry 126 bhp he was pulling away at the end of the straights at Goodwood. The Seven is a brick, like it or not, use its strengths in the twisty stuff 

[Mavic82]

I would certainly fit race wing stays but forget the csr wings. They reduce lift. You should try some very long front wings that fit closely to the wheel. As close to the ground as you can front and rear of the wheel. Can you lose the screen and go aero?

the under tray is a good idea, inboard suspension would help, tape over all body gaps, use alloy tonneau, reduce ground clearance potentially but essentially you want to reduce frontal area and remove air flow restrictions. Hence why early race cars had single roll hoops rather than full roll bars or cages.

if lift is an issue fit a front nose cone chin spoiler, or just fit your number plate as low as possible.

i would say read some theory and have a crack, if does not add weight it's worth a go.

keep us posted, any mods will make you feel quicker which will probably make you quicker

[7 wonders of the world]

If you decide to go for Freestyle inboard drop me a mail as i'm looking to have a batch of the bellcrank rockers made for a few of use.

 

[mcerbm]

Unfortunately a chin spoiler wouldn't be allowed as part of running in the road going class. Mavic yes I'm using aero instead of a screen. Just looking at pictures of cars in lowflying it seems like the csr style wing wraps round more of the tyre circumference both front and back? Can anyone confirm? I also read that the flat top with the trailing edge was designed to disrupt the airflow so it didn't follow the entire wing and therefore decreased drag. Sounds like it's worth a shot. 

[gileshudson]

[MADMALC]

I have seen head lamps rotated 180 for less drag.

[Rattie]

Can't help thinking, with my limited knowledge of aerodynamics, that the headlamps would be less efficient reversed.

[Superwhite R283]

Interesting read, haven't seen that before, thanks for sharing. Following this with interest   

[Julian H]

Thankyou Giles, very interesting article.

[mcerbm]

Excellent MIRA article, I had seen a text transcript before but not the full article with pictures. Also lowflying dropped through the letterbox this morning and a decent chunk of the magazine is dedicated to freestyle and their handling / aero engineering improvements. Also quite interesting. I'm not sure if louvred front wings would get past scrutineering though. 

[sjmmarsh]

The chin spoiler is allowed on road going cars - this is what you are looking for, not an F1 style front wing!

steve

[mcerbm]

interesting I didnt even know that existed, if its a csr item has any one tried fitting it to a s3 chassis, i presume the nose cone is different?

[magister]

I have often thought, from a sprinting point of view, I would be better replacing the passenger tillet seat with a smaller bucket type seat without a built in head rest. It might give a cleaner airflow over the passenger side tonneau (particularly as I only run with an aeroscreen on the drivers side)

just a thought ......

PaulB

[Simon.Rogers]

I have new pre preg carbon CSR wings just about to be launched. They are slightly longer at the front and back to others. These may help.

My CSR wings fit like gives and must reduce drag compared to the standard ones.

I would also take a look at the regs again as we all run road going and as long as it meets MOT then we can pretty much use anything.  So you may be restricting yourself on the options.  Obviously I don't know the details of your rules.

[LesG]

I have louvred front wings on my car, and have sprinted with them for the last 5 years in Roadgoing, no scrutineer has ever commented about them. They definitely work to allow the air through, as is blatantly obvious in the wet! 

[mcerbm]

LesG thats good to know that you can use louvred wings. zaandvoort and Spa both have corners where my entry speed is in the 130mph + range and you can really feel the lighter steering and the car isnt happy turning in.
 

Rattie, I have seen a few sprinters in scotland turn their headlamps round to get the pointy-ish cone part parting the air rather than the large flat face. Its marginal if it makes a difference in the sprints I compete in, but at knockhill the speeds are a bit higher and it may play its small part in the overall picture.

Simon, that is good to know, do you have a rough date when they would be available? I was probably going to go fibreglass for cost reasons but its good to have the choice and the extra length front and back may be persuasive! 

[Golf Juliet Tango]

 

I probably should of mentioned that due to being in the road going class I dont think I can use anything other than parts caterham offer as standard from the factory.

Therein lies your problem. It's something which Caterham have significant problems:- the car is non-aerodynamic but they can change nothing (or little). They design something aero-dynamic and everyone throws their hands up in horror. (no it wasn't pretty to look at).

Without the restriction you have stated, I would add Cord-like teardrop wings (enclosed sides as far as possible) instead of the standard items.

Within their rules, I would have the ali half-tonneau but add a vertical curtain between it and the transmission tunnel to keep air out. You use some vinyl and could fix it with one inch velcro.

 

 

[OliverSedlacek]

Just because you've seen people turn their headlights around doesn't mean it's beneficial. After all, a low drag shape is pointier at the back than at the front.

[Simon.Rogers]

Carbon CSR wings are now available.

My own pair are on their way.  As I said I had seen the preproduction set and I was more than happy.

Super light also.

£320.00 for the pair.

I will photograph them when they get here and add them to the website.

[Drumster]

ISTR that Andy Couchman wrote an article in LF some time back about various lengths he went to to make his car more streamlined for Brighton Speed Trials (I think?). This included among other things encasing the rear wheels by 'filling in' the rear arches and adding tapered fins to the FIA bar. 

We really need Andy to point us in the right direction for a fuller description but I think all his hard work made very little difference.