Aerodynamics

Dr.Jeff

True Classic
Aerodynamic related topics seem to come up in various discussions; obviously when talking about things like spoilers, but also in conversations like the flow of air through the engine bay, radiator, etc. The subject has been raised many times, including some very recent threads.

Unfortunately the science of aerodynamics is extremely complex and beyond the ability of most hobbyists (myself included). Without sophisticated modeling technology and wind tunnel testing we are really only guessing. Particularly with older obscure vehicles like the X1/9 where the path has not been paved very well.

The following article was posted in today's newsletter form Grassroots Motorsports Magazine. It was printed in last December's issue. Unfortunately it does not offer much real help, but it does address a couple of common misconceptions. So I thought it might be worth a look for those (like myself) who like to modify our X's:
https://grassrootsmotorsports.com/a...ampaign=GRM+Daily+Newsletter+Automation+Email

I'm sure there are many other resources that are much better and offer greater assistance on the subject. The ones that I have reviewed in the past were written by and for aerodynamic engineers, and therefore much too complex. Especially when I am not really trying to improve the aerodynamics of my street cars, but I like to add body modifications to give a "track" look to the car (i.e. purely for style). It would be nice however to know just how much good or harm I am doing when making such changes. Anyone have good articles written for the masses that might be useful?

In my opinion this is what not to do:
62eb41f4059c50bc5fbcde27ab8571d4.jpg
 
That would be exactly what you would want to do for a Amod hillclimb car, or even an amod autocross car. But, for the rest of us in everyday land, I agree with you.
 
Years ago I did a series of coastdown tests on one of my vehicles as a school project out at a closed airport. The basic idea is to record the time interval required for the car to slow down from say 80 to 60 mph with transmission in neutral. Then do it again from 30 to 10 mph. Over a series of runs you will get a fair estimate of both rolling/drivetrain friction and aerodynamic drag coefficient using some simple formulas. While not NASA accurate the data are good enough to tell you a ballpark number and fun to see the effects of various changes. With so many cool apps now available you may be able to get speed and elapsed time in graphical form right on your phone in real time. That's something we could only dream about 35 years ago.
 
I wonder if they ever stuck that car pictured above in a wind tunnel...it looks more like a styling exercise than something serious...
 
Bob Nelson has a pretty sweet ride, some interesting aero - he has some great vids on Facebook & Instagram.

I borrowed this picture of his car off Facebook - really nicely built, K20 - and he keeps making it faster and faster every year!

upload_2020-2-7_17-0-22.png
 
Aerodynamic related topics seem to come up in various discussions; obviously when talking about things like spoilers, but also in conversations like the flow of air through the engine bay, radiator, etc. The subject has been raised many times, including some very recent threads.

Unfortunately the science of aerodynamics is extremely complex and beyond the ability of most hobbyists (myself included). Without sophisticated modeling technology and wind tunnel testing we are really only guessing. Particularly with older obscure vehicles like the X1/9 where the path has not been paved very well.

The following article was posted in today's newsletter form Grassroots Motorsports Magazine. It was printed in last December's issue. Unfortunately it does not offer much real help, but it does address a couple of common misconceptions. So I thought it might be worth a look for those (like myself) who like to modify our X's:
https://grassrootsmotorsports.com/articles/aero-mythbusting-tackling-bad-questions-bad-info/?utm_source=ActiveCampaign&utm_medium=email&utm_content=Project+Fox:+Low-Buck+DIY+Paintjob&utm_campaign=GRM+Daily+Newsletter+Automation+Email

I'm sure there are many other resources that are much better and offer greater assistance on the subject. The ones that I have reviewed in the past were written by and for aerodynamic engineers, and therefore much too complex. Especially when I am not really trying to improve the aerodynamics of my street cars, but I like to add body modifications to give a "track" look to the car (i.e. purely for style). It would be nice however to know just how much good or harm I am doing when making such changes. Anyone have good articles written for the masses that might be useful?

In my opinion this is what not to do:
View attachment 29065

At least it looks as though it has sufficient horsepower to overcome the aerodynamic drag ;)

If you are serious about aerodynamics, then nothing beats the BT46 "fan car":

2001_Goodwood_Festival_of_Speed_Brabham_BT46B_Fan_car.jpg


Interestingly, I noticed that there is a new design being proposed based on this idea (with even more extreme aerodynamics):

Alfa-Romeo-2018-Brabham-EVO-F1-Concept-18.jpg


Ciao,
Dom.
 
Doc, if you are going for the look without concern for function, you can do whatever you want whether it makes aero sense or not. I don't know what the streets are like in Sin City but out here they tend to be in bad shape so low front splitters and fancy undertrays will just be ripped off. Big wings will get you all manner of comments as my snorkel seems to confound "normal" folks and I constantly get asked what that thing is.

I like the early stock front spoiler and want a rear ducktail as the aero for my car.

Kind of depends what you want, period correct look for a race X or a modern time attack look which might be out of place on an X.
 
@carl is right, around the DC metro area even a Corsa kit is constantly in danger of getting ripped off by uneven road surfaces...

I WANT A SNORKEL!
 
Be careful what you yell for, I can send my wife to the dollar store and get you a kids swimming snorkel.
 
Be careful what you yell for, I can send my wife to the dollar store and get you a kids swimming snorkel.

Some how that wouldn't surprise me... :)

I want a snorkel that goes on the back of my X1/9 and looks similar to the one FAZA produced!!
 
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