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View Full Version : can aerodynamics help me? -can you help me?



ALLstrokedOUT
06-28-2010, 03:00 PM
Hello everyone, I am in the process of dreaming up something else for the duster now.. In the past few months while driving the thing 200 miles a week I can't help but wonder what little things (emphasis on little) can be done to improve its fuel efficiency. I know it's never going to see much over 12mpg city, and I know I could do things like take the cam out and go to a more mild one, but that's not the point, I want to squeeze what I can out from this combo.

Right now I'm getting 10mpg city and a bit over 15mpg hwy, To sum up everything stated above, I'd like to see what I can do to get those numbers higher, and for this thread it'd be achieved through addressing the brick-like aerodynamics of the duster.

My current thought for a weekend project is to design a front air dam/splitter to maybe deflect the air from hitting the k member and headers. I know it wont be much help, but for the effort and costs, i think that any improvement would be worth it. So here are my questions: If i were to do something like the Nascar design wouldnt that vertical portion of the splitter actually hurt my cause? Does anyone know of an approximate angle the vertical and horizontal portions of that splitter would have to be to help? Thanks for any insight you could give

406 Q-ship
06-28-2010, 03:40 PM
Overdrive is where I would look too. Both my Monte Carlo and Chevelle got 13 to 17 Hwy MPG and with putting in an OD both jumped in to 18 and 21 MPG. You would be lucky to gain 1 MPG with aero, it still is going to be a blunt nosed muscle car, unless you make some major changes.

ALLstrokedOUT
06-28-2010, 04:38 PM
That's what I was assuming, but I figured I can put a splitter together for cheap and if done right with a few other little tweaks it should be more than worth the effort (including that added stability). The trans is already an overdrive, 0.76:1 is the OD gear I believe. When that thing finally breaks in two I'll rebuild a t-56 and put that in. I am also in the process of putting together a fuel injection system for multiple reasons besides fuel economy, but that's like 6 months away..

Chris 68
06-29-2010, 04:13 PM
*cough*t-56*cough*6.1 hemi*cough*

novaderrik
06-29-2010, 05:14 PM
block off as much of the grille as you can without causing the car to overheat. maybe even figure out some way to vent the air out via hood or fender vents.
this keeps air out of the engine bay, which reduces drag.

ALLstrokedOUT
06-30-2010, 02:01 PM
Well i did a little more reading on the subject matter, and heres what i found out:

From an article on Edmunds.com: Doug Frasher, strategic design chief at the Volvo Monitoring & Concept Center, said to Edmunds "...we can expect to get 23.8 mpg . Take 10 percent from the drag coefficient, we'll now get 24.3 mpg."

To sum things up from the Hot Rod Magazines article: "Car Aerodynamics - A2 Wind Tunnel - Wind Camp Tech Theory" each 'count' is referring to 0.001 of the Cd rating. The article states: a 50 count reduction would bring the Cd from 0.250 to 0.200. The early 2nd gen camaro's initial Cd in the article was at a Cd of 0.50..so for all intensive purposes that should be a fair estimate for the duster..
The counts of Cd improvement are as follows for what i would be interested in/could feasibly do:

Air Dam- "20 counts less drag, 50 less lift. The taller the car sits, the more important the air dam"

Sealing rear of hood by cowl-"10-20 counts less drag, 50 to 75 in lift"

A rear spoiler "mimicking the one from the HOT ROD Spl" reduced the Cd by ~0.045

Obviously these improvements will be less than what they reported, but I could be looking at something like a 20% improvement in my Cd for those three things. That's a 1mpg improvement not to mention the other handling benefits...

..Maybe i could also make a sort of 'funnel' to better direct the air through the radiator, instead of hitting the core support?..And Chris, a t-56 would be amazing, but for the price and hassle of a new hemi, i might as well port the heads, get a smaller cam and call it even

Sorry for the long post, but before i go look at this picture of the duster with all the suspension components, oil pan, and headers the air has to hit at highway speeds- there's no way an air dam could do any harm, and i safely have 7-8 inches vertical before id even be as low as the oil pan..so here's another excuse to learn/play with Solidworks more and come up with a rough design..
https://static1.pt-content.com/images/pt/2009/03/P1010062-1.jpg

novaderrik
06-30-2010, 02:23 PM
you don't need no fancy computer program- just get some cardboard and masking tape and start mocking things up.

ALLstrokedOUT
06-30-2010, 08:35 PM
..i know i dont need a fancy program to design the thing, and in the end i will be making it out of carboard before the final material anyways, but i have Solidworks at my disposal, and i need to learn how to use it, so why not do something useful on it are my thoughts

MrQuick
06-30-2010, 10:01 PM
just getting your bearings packed with good synthetic grease and a perfect preload can fetch you better MPG's...combine that with a slight rake and a nice new waxing, your golden. Remember that the more weight you add as far as areo equipment can negate the MPG's saved.

Now if you were trying to break the 185 mph barrier than I'd see the benefit.

interested to see what you come up with.
Vince

Chris 68
07-01-2010, 10:53 AM
Alright Tim I have some serious input now lol look into the old trans ams they had a vent on each front fender behind the wheel that were pretty efficient at getting air and pressure out of the engine compartment. A front air dam is a must! I've seen some very cool ideas where you can block off the entire front grille and have a wide opening coming up thru the bottom of the air dam and going thru the radiator, I'll post of some pics if I can find it. Another thing is under body panels, I've always wanted to put them on the camaro.

cheapthrillz
07-01-2010, 11:22 AM
A front air dam is a must! I've seen some very cool ideas where you can block off the entire front grille and have a wide opening coming up thru the bottom of the air dam and going thru the radiator, I'll post of some pics if I can find it.

This would be cool. Think 4th gen f-body. They used this kind of airbox.

Another idea would be the at-home wind tunnel (requires a friend.... got one of those? lol jk). Here, read this thread: https://www.pro-touring.com/forum/showthread.php?t=61936&highlight=yarn

Hope this might give you a few more ideas!

I'm also interested to see what you come up with, because my '65 Galaxie is very similar in shape (aka BRICK). lol

ALLstrokedOUT
07-07-2010, 12:45 PM
Thanks guys for the ideas, im still thinking about front air dam, but i believe i read in another thread somewhere you want the dam to be 2-4 degrees from vertical. Ill be thinking about it for a bit more; maybe ill make a plywood form this weekend to assist in making the fiberglass mock-up.

On my 1000 mile roundtrip to the panhandle last weekend i noticed a few interesting things: for nearly two hours that it was steadily raining when i was going ~75mph there was not a single drop of water on ANY of the rear window (falling on it or flowing back like a 'stream' of water from the body). I couldnt see the trunk to see where it was getting wet, but the windows enough proof to tell me i have a fairly large low pressure pocket that i may want to address. The second point comes about a bit more embarrassingly but..i have an oil leak somewhere. I would assume the little oil molecules and road grime are coming from under the car and hook onto the low pressure bubble at the back of the car because theyre hitting the back bumper, tail lights..all the way up to the trunk lid. This is telling me, who has no experience in aerodynamics, that the low pressure at the back of the car may be almost as detrimental as the issues at the front of the car.

I read the articles from the thread that you provided the link to cheapthrillz, and now i think im also leaning towards making some vortex generators just before the window, maybe even eventually a tasteful rear spoiler-what does everyone think?

EDIT: Heres a pic of my idea so far, following the Nascar COT's design..
https://static1.pt-content.com/images/pt/2010/07/frontnascardam-1.jpg
https://static1.pt-content.com/images/pt/2010/07/frontnascardam2-1.jpg

Jim Nilsen
07-07-2010, 01:56 PM
I have run my car with and without a rear spoiler and can tell you that if you have any blowby it will find its way to the back of your car with a rear spoiler.

I can't define the aero gain for me when I put the closeout in from the radiator to the header panel but I can tell you that my hood doesn't bow up any at all now which means there is less pressure under the hood. I had a few issues with the cooling and the hysterisis of the DCC controller with just the closeout but I put the front spoiler on before I went to Gingerman and the problem has stopped. It will now stay within a few degrees of the thermostat.

I know I gained some mpg from the spoiler and the high speed gain was mostly in the hood staying down now and if it helped other things I can't feel them.

An air dam is definately a must no matter what kind of driving you plan to do.

ALLstrokedOUT
07-22-2010, 08:04 AM
Well, i have one more exam for summer school up here in Tampa before i can go home for a couple weeks and work on this stuff..The first thing im going to do is put yarn on the hood, cowl, and trunk to see what theyre doing. I have already cut some pieces of plywood, put some pie cuts in them, and bent them to make the corners of the front splitter, that thing should take about a week.

In these couple of weeks i will also be repairing some rust spots; my dads gunna repaint the flat black for me. Before he paints anything though im going to lay some wax paper on the roof and try to make a fiberglass vortex generator (like the evo's)..i know it may look strange on a brick of a muscle car, but if im going to make it/mould it now's the time. If it looks too odd or doesnt do much i can always remove it..so in the next week or so there should be some good updates on this long, possibly futile journey

ALLstrokedOUT
07-26-2010, 04:22 PM
Well, im back in town, and i am getting close to fiberglassing the air dam for the duster, here are a couple pictures of the plywood mould i made for it. I should have most of the major fiberglass done in another day or two. While im doing that ill also be 'glassing a section of the roof for the vortex generator..hopefully all will be done (the rust repairs as well) in a week or so. I will do some shots of the yarn test strips before and after the vortex generator.
https://static1.pt-content.com/images/pt/2010/07/DSC01061-1.jpg
https://static1.pt-content.com/images/pt/2010/07/DSC01054-1.jpg

Bjkadron
07-29-2010, 08:36 AM
Wow.. Nice work.. Another option to the yarn (that doesn't require another person) is using a bit of motor oil mixed with powdered paint. Drip it everywhere, then go for a drive. Low pressure spots will have longer trails. I am getting ready to start a serious aero program on my Duster. And actually you want a low pressure zone at the back and bottom of the car.

Also, How are you planning to attatch the spoiler?

P.S. I get 15mpg mixed and 21+ hiway in my Duster without an overdrive. But it does have 2.76 gears.

Mr.VENGEANCE
07-29-2010, 05:39 PM
gonna be good!

im keeping an eye out on this thread..

ALLstrokedOUT
07-30-2010, 07:39 AM
..Its good to know im being watched haha..heres a shot of the fiberglass work, i took it out of the mould today, it turned out decent. Tomorrow ill weld up a steel sub-structure that ill embed in a second layer of 'glass and will be what i use to mount the dam to the car.

There are two mounting points in front of the radiator on the core support, and i will also utilize the two quarter panel support bars, from the subframe to rite in front of the tires, somehow (not too sure how yet, but should be easy). I think i will also tie into the support that goes back to the k member..ill be sure to take pics of it all..
https://static1.pt-content.com/images/pt/2010/07/DSC01072-1.jpg
Now, Bjkadron..are you saying that the vortex generator above the rear window would not be beneficial? I understand the low pressure under the car is desirable, but I have read, and am under the impression, that the low pressure pocket at this position is effectively sucking the car backwards. So filling this pocket in by redirecting high pressure air via the vortex generator would help..what do you think?

Bjkadron
07-30-2010, 01:30 PM
..Its good to know im being watched haha..heres a shot of the fiberglass work, i took it out of the mould today, it turned out decent. Tomorrow ill weld up a steel sub-structure that ill embed in a second layer of 'glass and will be what i use to mount the dam to the car.

There are two mounting points in front of the radiator on the core support, and i will also utilize the two quarter panel support bars, from the subframe to rite in front of the tires, somehow (not too sure how yet, but should be easy). I think i will also tie into the support that goes back to the k member..ill be sure to take pics of it all..

Cool... I was thinking about the same thing. except I have a trans cooler attatched to one of the mounts on the rad-support. Why not just extent it to the two holes in the front of the k-frame?


..
Now, Bjkadron..are you saying that the vortex generator above the rear window would not be beneficial? I understand the low pressure under the car is desirable, but I have read, and am under the impression, that the low pressure pocket at this position is effectively sucking the car backwards. So filling this pocket in by redirecting high pressure air via the vortex generator would help..what do you think?

No.. You want the low pressure pocket on the BOTTOM But not the one on the top(by the back window). Sorry If I wasn't clear. So I would try the vortex generator.

ALLstrokedOUT
08-01-2010, 09:29 PM
Hey everyone..not a whole lot new, but i like pictures so here are some more: the main steel structure mounts at three points on the radiator core support. In the second shot you can see that i will be closing in this space and will be using the hole in the bumper, and some u-bolts around the quarter panel support brace for additional support. the side 'boxes' are getting some steel bracing, its just not as complex as the first picture. Finally another rough idea of what it should look like (it looks more awesome in person..).
https://static1.pt-content.com/images/pt/2010/08/P1010008-1.jpg
https://static1.pt-content.com/images/pt/2010/08/P1010004-1.jpg
https://static1.pt-content.com/images/pt/2010/08/P1010005-1.jpg
Today im going to embed the steel bracing in fiberglass, and close up the space in picture #2.

p.s. Do you think i should add an aluminum spoiler in the middle, it would span between the two fiberglass portions or leave it off?

novaderrik
08-02-2010, 12:57 AM
it's starting to look like you are building a car to go NASCAR racing.

Bjkadron
08-02-2010, 03:44 AM
looking good!

Bryce
08-02-2010, 05:41 AM
Looks good.

ALLstrokedOUT
08-06-2010, 10:43 AM
Well, its been one step forward and two steps back the last couple of days. Ive been having some fitment issues now that all the fiberglassing is done, so ive had to re-adjust some things which set me a day behind. I probably ground about 1/4 of the fiberglass off trying to get everything smooth enough for a skim coat of bondo. So far it probably weighs less then 10lbs, well see how much bondo i need though..
https://static1.pt-content.com/images/pt/2010/08/DSC01077-1.jpg
https://static1.pt-content.com/images/pt/2010/08/DSC01075-1.jpg

Bjkadron
08-06-2010, 07:04 PM
Looking good! What are you doing to reinforce the splitter?

ALLstrokedOUT
08-13-2010, 10:55 PM
..I have 1/4" steel rod embedded in the fiberglass for reinforcement, the whole assembly mounts to the car at four different points..but im afraid im going to have to admit defeat on this project for now..the things in primer waiting to be sanded and have the final touches put on it, but im leaving to move into my new appartment for school noon tomorrow, gunna have to be a weekend job sometime when i come home..

Jasons72
08-14-2010, 05:55 AM
Its looking good, keep it up and keep us updated.

Bjkadron
08-14-2010, 01:11 PM
That is too bad. I just started my aero program... I posted a little about it in my thread but I will let you know this: the separation issue at the back window is not as bad as I was thinking it would be. it was actually quite good for the era.

Wicked
09-29-2010, 05:13 PM
I think the splitter will help with downforce on the front end, but will not reduce your drag. You are using the high pressure that would have acted on your front suspension to now act on the splitter.

Race cars with similar front ends trade top end for higher downforce and corner speeds.

For a car only getting 10mpg...I would suggest fuel injection and overdrive gearing. 20+ mpg in a old classic is nothing new. Those items will give you the biggest gains. After that, smoothing the underbody will help with overall aerodynamics while also increasing downforce.

ALLstrokedOUT
10-03-2010, 12:07 PM
Yea..im looking for a broken t56 to rebuild and put in over next summer..then im planning on putting a megasquirt system in after that.

I was more assuming that the air dam reduced some turbulance under the car..i need to redesign this thing anyways, it hits every speed bump i go over, so im probably taking two inches off of it, getting rid of the fiberglass 'splitters' on either side, and replacing them with aluminum so it can take the bumps a bit better. Theres definatly a learning curve with all of this stuff..

Wicked
10-07-2010, 01:07 PM
Yea..im looking for a broken t56 to rebuild and put in over next summer..then im planning on putting a megasquirt system in after that.

I was more assuming that the air dam reduced some turbulance under the car..i need to redesign this thing anyways, it hits every speed bump i go over, so im probably taking two inches off of it, getting rid of the fiberglass 'splitters' on either side, and replacing them with aluminum so it can take the bumps a bit better. Theres definatly a learning curve with all of this stuff..

Sounds like you're on the right track.:cheers: