The drag car does have the spare tire well cut out and flat. The diffuser we built for the car is shaped to help take advantage of that but we are still using the EVO8 rear fascia, so there are improvements that can be made there.

I wish I had more detailed pictures of all the stuff we had to do on my 2G DSM tube chassis race car. It's already been about 5 years since I raced it and the stuff we learned on that car was pretty nuts. It's funny as it is just recently coming back to me and we are implementing it on the drag EVO now and it is all working.

 

David, I know of a certain car that could probably break your 10.89 record for the 20G-LT if you'd only get off of your ars and make a rear undertray for the stock bumpered IX. I'm sure the money in your pocket would mean more than the 20G-LT record. I sure would like to get all the help I can get for the shoot out too.

 

I am working on it!! haha This week is tough, shootout coming I have a bunch of tunes scheduled this week etc. Be hard to finish up much more this week than we have already.

Breaking my 10.89 shouldn't be too hard for you guys with the tires and 60' times you are running. Remember, I don't hold the lowest ET record for that turbo. That was Curt, who I think ran 10.5's?

 

i don't know what you're getting at about nascar. nascar like any sanctioning body has limits on downforce or downforce producing items. also when you're going 200+ mph downforce and drag is your enemy. (i don't know if this is what you're already suggesting) i also don't know what you mean by "helping them more" as each design will have its advantages and disadvantages so you'd really have to say something to the effect of: which one is giving them more downforce, which one is allowing them less drag.

for roadracing cars (which is what these undertrays with the vent/wings under the car), you must model the cars producing downforce. for drag cars you would go with nascar... or... drag cars.

 

What I am getting at is that an Evo does not have any of the aerodynamic characteristics of a F1 or any other open wheel car. We should model our designs after cars that are similar in shape/style to our own. I was saying look at what NASCAR does because if it works for them at their speeds, it will probably be something to look at for ours.

 

yeah... if it's cut flat then you can angle the diffuser higher or mount the diffuser higher with the shallower overall angle of attack. there is a pdf earlier in this thread about the theory of idealizing diffuser angle. it would all depend on how much downforce you want to make at what speed.

if you could cut the butt of the car nice and high it would help turn flow and also smooth out the rejoining of top and bottom flow.

if you ever make a tube frame evo i'd suggest making the most "almond" shape possible for the aeroshell. making it look like an almond from the top and from the side will yield the most aerodynamic shape (the most aerodynamic shape is in fact an almond, the reason for this is as you push through the fluid medium the fluid will compress around the "tail" end of the almond and push your through, recouping some aerodynamic losses. this is also why sloped back cars are generally less draggy than box shaped).

 

our cars aren't working at 200mph. do you know what a nascar feels like at 150mph? they don't work UNTIL over 190mph. modeling our cars after theirs (exclussively) would be a mistake. nascars are made for low drag and super hgih speed downforce. most of their downforce producing devices don't have any benefit at low speeds, and might even be detrimental for the cooling of some parts as one of the way nascar (and other racecars) minimize drag is by sealing up seams, this while a novel idea will more than likely destroy a street car.

the fact is there's no one motorsports industry we can just copy with great success. it depends on what you're doing, dragrace or roadrace and then what speed you'd like how much downforce or drag.

you can see earlier in this thread there is a gigantic wing on evolutionary's car that is more or less out of the f1 book, he says it works, i believe him. you see many tube frame drag cars with nascar style spoilers (and almond shapes). one works for the guy that needs downforce, lots at all speeds. one works for the guy that needs to have slippery chassis and top end downforce for the finish line.

 

Well I got my books. Holy crap, the one is, uh, well WAY THE HELL OVER MY HEAD. Not enough pictures and the words are too small. Looks like a math book. Anyone want it? I just glanced at it again, I'd need 4 years of college just to read it.

"Low Speed Aerodynamics" Second Edition by Joseph Katz and Allen Plotkin.

It's like 600 pages long, pertains to low speed air planes it seems. Trinydex, you want it? If you do send me a PM with your address.

The other one is good though. Gonna read some later tonight. I'll let you guys know if I learn anything

 

if you guys are interested, check out mulsannescorner.com

they have diagrams and info on aero designs, on the sort of cars i raced (lmp)

if anyone says aero doesnt come into affect until high speed, dont buy it... you can feel downforce at 50mph on the track... just like how you can feel 10lbs of crossweight if you are in tune.

cheers

cb

 

I checked out that link to mulsannescorner, problem is there is very little information there that pertains to sedan bodies like we are working with and running. Nice site, just not much there that pertains to us.

 

A good starting point would probably be DTM and WTCC. Don't just look at current chassis, either. Look at some of the older designs and then the newer designs and start from there. I can post some pics of DTM cars that I took at the Nurburgring museum a couple of weeks ago.

l8r)

 

i think we can take any number of cues from any number of series in any number of years.

the fact is there's so many ways to cut the aerodynamics pie, you need to find out what you want to do on a certain section of the car and then adapt a "tested" method of addressing that area that will work on your PACKAGING!!! the latter is the most important part.

 

aero, realistically, is aero..

you see lots of DTM cars taking the shape of closed wheel and open wheel cars....

the big aero inefficiency on our cars, is the underside... the car needs a proper flat bottom with a rear undertray.... the pinch point of the undertray is very important.... cars like the f360, f430... they try to create tunnels like the older GTP cars had....

get dive planes on the front... help air to evacuate... and flatten the bottom of the car..

the most important thing is to create a good aero platform... you want to balance the entire car... we would spend lots of time doing steady state speed runs down the straight to measure damper travel to confirm the amount of downforce on a car....


cb

 

Ill add to this with what have gathered from this thread, and my previous knowlege of aero.

It seems that some of you guys are hung up on turning the air flow underneath the car into the wheel wells. Well, technically, this is a great way to get rid of some air underneatht he car, creating a low pressure situation- thus creating downforce. BUT, this would only work well if you have a way to extract the high pressure in the wheel wells. This is what the dams on the front of the wheel wells do. Understanding fluid dynamics/aero dynamics helps, but basically that wall shoves air off to the side with quite a bit of force, and it pulls air from the high pressure zone in front of the wheel with it.

As for canards on the front bumper: they are not actually designed for downforce per-say. Thats not to say they dont aid in downforce. But their main prupose is to create vorticies that travel down the side of the car. this helps a few things:

first, it helps evacuate the wheel wells of high pressure.

second, it creates a boundry layer of air between the high speed air passing a car while its moving at a high rate of speed. This prevents that high speed airflow from adhearing to the car and creating drag. (the high speed airflow stays laminar, "sliding" across/along the swirling air that is the boundary layer between it and the car surface)

Third, the boundary layer of swirling air keeps the high pressure airflow from getting underneath the car. this keeps pressure low underneath the car, aiding in downforce.

While searching for a picture to draw how this works, I came across this illustration of how it works, and theres actually a very easy to read article on basic aero here. link below:



http://www.sportcompactcarweb.com/te...t_2/index.html

 

^ this is what i was saying all along