Chalo
100 TW
neptronix said:
165/80R15 tires were made by the squillion brazillion for VW Beetles and others. Surely there are some badass options in that size.
Lightweighting and aerodynamic optimization of a subcompact car.
- Thread starter neptronix
- Start date
165/80R15 tires were made by the squillion brazillion for VW Beetles and others. Surely there are some badass options in that size.
I looked into VW tires and wheels... i like the more bicycle like tire aspect and may actually get away with tires that narrow.
Seems that quality tires are not made in that size.. but the tires still do exist.
Tires that tall may negatively affect the sportiness of the car around turns.. and the rims that fit them were made for a car that's 600lbs lighter... so that may be creating a safety issue.
We're getting closer..
Perhaps an ideal answer is to use a very light 15" rim in the rear with a 185/65/15 eco oriented tire. It would suck to have two tire sizes.. but i could lower the unsprung and rotating mass in the rear.. which would make the suspension more supple. And utilize cheaper and more fuel efficient tires back there.
Even better would be 175/65/15.. but the backend would have a more notable height loss. Don't think i want to go that far... unless i could use some kind of spacer to make up some of the difference.
In terms of wheel aerodynamics.. if i use a rear cover like the 140mpg Daihatsu UFE, then i can hide the ugliness that a different set of wheel sizes and shapes creates.
The UFE also has an acrylic aerodynamic wheel cover which is pretty aesthetically appealing compared to moon discs.
I'd like to imitate that somewhat, even if it's just a matter of filling in gaps in my current rims.
A Tesla owner has done the same thing with good results.. though i'd say the aesthetics could be improved greatly!
Seems that quality tires are not made in that size.. but the tires still do exist.
Tires that tall may negatively affect the sportiness of the car around turns.. and the rims that fit them were made for a car that's 600lbs lighter... so that may be creating a safety issue.
We're getting closer..
Perhaps an ideal answer is to use a very light 15" rim in the rear with a 185/65/15 eco oriented tire. It would suck to have two tire sizes.. but i could lower the unsprung and rotating mass in the rear.. which would make the suspension more supple. And utilize cheaper and more fuel efficient tires back there.
Even better would be 175/65/15.. but the backend would have a more notable height loss. Don't think i want to go that far... unless i could use some kind of spacer to make up some of the difference.
In terms of wheel aerodynamics.. if i use a rear cover like the 140mpg Daihatsu UFE, then i can hide the ugliness that a different set of wheel sizes and shapes creates.
The UFE also has an acrylic aerodynamic wheel cover which is pretty aesthetically appealing compared to moon discs.
I'd like to imitate that somewhat, even if it's just a matter of filling in gaps in my current rims.
A Tesla owner has done the same thing with good results.. though i'd say the aesthetics could be improved greatly!
www.recumbents.com
10 kW
I have been down this road and have done research and some mods. What seemed to do the most for me was the partial belly pan I added. It started just behind the rear axle and filled in all the gaps up to the back bumper. I used coroplast and got about 2-3MPG on the highway which was amazing in a car that always got 27MPG. I also blocked the bigger of the grill inlets. They design those grills for 100F+ weather which doesn't happen often around here anyway,
http://www.recumbents.com/car_aerodynamics/
http://www.recumbents.com/car_aerodynamics/maxima.htm
I still have the car but it doesn't look like this yet.
Warren
http://www.recumbents.com/car_aerodynamics/
http://www.recumbents.com/car_aerodynamics/maxima.htm
I still have the car but it doesn't look like this yet.
Warren
...hell yeah, thanks for chiming in!
I actually owned one of those and lightweighted the hell out of it and had the front and rear suspension all stiffened, in addition to a nasty sounding exhaust and some other minor mods.. loved the car.. but not the cost of premium gas nor it's advanced age.
My MPG record on that car was 40mpg in slow city driving.. 36mpg on the highway.. without aero mods.. per my scanguage.... more likely was low 30's on extended highway trips at 60mph.
Will absolutely be looking at your page when i get a minute.
I see that on the Yaris IA, there are spots in the grill that are more cosmetic than functional..
I'm surprised you were able to block that much off and get away with it and i'm inspired to get close to your insanity on that level.
I'm considering using spray painted lexan RTVed to the front end instead of screws for a very flush fit.
..or countersunk screws.. like so:
I actually owned one of those and lightweighted the hell out of it and had the front and rear suspension all stiffened, in addition to a nasty sounding exhaust and some other minor mods.. loved the car.. but not the cost of premium gas nor it's advanced age.
My MPG record on that car was 40mpg in slow city driving.. 36mpg on the highway.. without aero mods.. per my scanguage.... more likely was low 30's on extended highway trips at 60mph.
Will absolutely be looking at your page when i get a minute.
I see that on the Yaris IA, there are spots in the grill that are more cosmetic than functional..
I'm surprised you were able to block that much off and get away with it and i'm inspired to get close to your insanity on that level.
I'm considering using spray painted lexan RTVed to the front end instead of screws for a very flush fit.
..or countersunk screws.. like so:
markz
100 TW
You know about golf ball dimples and how they help the golf ball fly further.
Well, you can gain 14% fuel mileage with a dimpled car.
https://youtu.be/8wG-gr_IRHQ?t=322 8)
Well, you can gain 14% fuel mileage with a dimpled car.
https://youtu.be/8wG-gr_IRHQ?t=322 8)
Can't stand the aesthetics, sorry 
Went out and bought some bigass lexan sheets to build some grill blockoffs... and found the coolest thing ever when i was there:
The dremel workstation!
It's like a drill press that can also operate at increments of 15 degree angles for precision grinding.
Also bought the biggest dremel they sell.. it actually has a chuck!
..real cool for making precision pieces... and being used as a mini angle grinder.
..this will get extra metal off in places that are hard to reach.
Went out and bought some bigass lexan sheets to build some grill blockoffs... and found the coolest thing ever when i was there:
The dremel workstation!
It's like a drill press that can also operate at increments of 15 degree angles for precision grinding.
Also bought the biggest dremel they sell.. it actually has a chuck!
..real cool for making precision pieces... and being used as a mini angle grinder.
..this will get extra metal off in places that are hard to reach.
Did another round of work on the car..
Spent a lot of time looking at the stock grill and air intake.. it was not immediately evident on how to best optimize the airflow due to the weird design. Finally emerged with an attack plan.
I bought a dreme 4300, which is their largest model.. the cutting power is super impressive and the smaller size versus the angle grinder makes for much cleaner bolt cuts which require a lot less hand filing.
There are a number of weight losses around the dash area.. some initial cuts were made.. but eventually the whole dash is coming out and will be looked over for further front end weight drops.
Some unnecessary turbulence was removed from the bottom of the car for a ~1lb weight drop.
The windshield area panel was removed.. looking for any potential weight savings. 1 stud, an unused bracket, and some bolt length was removed. Probably only removed 0.5 lbs.
The windshield wipers were unbolted and i was able to mount them about an inch lower without them interfering with each other in operation. Cheapest aero gain i've achieved so far.
Before:
After:
Spent a lot of time looking at the stock grill and air intake.. it was not immediately evident on how to best optimize the airflow due to the weird design. Finally emerged with an attack plan.
I bought a dreme 4300, which is their largest model.. the cutting power is super impressive and the smaller size versus the angle grinder makes for much cleaner bolt cuts which require a lot less hand filing.
There are a number of weight losses around the dash area.. some initial cuts were made.. but eventually the whole dash is coming out and will be looked over for further front end weight drops.
Some unnecessary turbulence was removed from the bottom of the car for a ~1lb weight drop.
The windshield area panel was removed.. looking for any potential weight savings. 1 stud, an unused bracket, and some bolt length was removed. Probably only removed 0.5 lbs.
The windshield wipers were unbolted and i was able to mount them about an inch lower without them interfering with each other in operation. Cheapest aero gain i've achieved so far.
Before:
After:
John in CR
100 TW
markz said:You know about golf ball dimples and how they help the golf ball fly further.
Well, you can gain 14% fuel mileage with a dimpled car.
https://youtu.be/8wG-gr_IRHQ?t=322 8)
I've often wondered about dimpled surfaces for planes, cars, and boats to reduce drag, because when I was on the water ski team I bought a new ski once that had a textured bottom as opposed to the very smooth bottoms of all other skis I've ever seen, and the new ski was too slippery to ever use in competition. In the slalom course you need to both accelerate and slow down quickly, and that ski was so slippery that I couldn't slow down enough to make a good turn around the buoys. Online searches don't turn up much research in this regard other than the positive effects with lubricated parts like crankshafts. One bicycle company claims significant advantage with dimpled surfaces on aero wheels, and apparently Ferrari did some wind tunnel tests too, but I was very surprised not to find anything for aircraft surfaces.
I never thought about it, but this made me poke around, so:John in CR said:
https://physics.stackexchange.com/questions/109395/why-arent-airplanes-like-golf-balls
I don't understand much of what's there...but I found this on Reddit :lol: that seems to simplify it down enough for me
:https://www.reddit.com/r/AskEngineers/comments/b3j8ka/why_arent_airplanes_dimpled_like_golf_balls/
Some images that make it easier for me to understand what the dimpling actually does
https://www.google.com/search?q=why+no+golf+ball+dimples+on+airplanes&newwindow=1&tbm=isch&ictx=1&fir=ZqxgTH4A3OylDM%252CzTflV86wLp7JTM%252C_
So i disassembled the bumper piece by piece to figure out how i could fit a grill block, and where would be a good place to fit it..
Also fixed the mentioned ding in the bumper.. that's an aero upgrade in itself :lol:
Air flow is very poor in the middle grill, as you can see.
While i was at it, i relocated the horn and eliminated a 1lbs brackets and bolt combo. As well as shortening many bolts at the edges of the car, which i now had access to. I still kept to my promise of not compromising any metal that would contribute to crash safety.
I noticed that the silver trim was a nylon ring.. if i could cut part of it's edges, i could use this to compress the coroplast on one side, and use the tension of the lower part to make a very tight fitting and stiff mounting
Some coroplast was cut and hit with a heat gun to force it into shape. Then painted. Although one side did get hit with too much heat and ended up dimpled. Oh well. This is my first time working with coroplast and i'll do it better when i revise this.
Finished product!
The lower grill could use some love too.. only half of it's width receives air. It is somewhat blocked off already. Taping on cloroplast will work here. I'll attack that later.
For the upper grill, i'd like to use transparent acrylic to preserve the look.
Now that i'm hip to working with chloroplast, i'd like to start making some panels for the car's underbody.
Also fixed the mentioned ding in the bumper.. that's an aero upgrade in itself :lol:
Air flow is very poor in the middle grill, as you can see.
While i was at it, i relocated the horn and eliminated a 1lbs brackets and bolt combo. As well as shortening many bolts at the edges of the car, which i now had access to. I still kept to my promise of not compromising any metal that would contribute to crash safety.
I noticed that the silver trim was a nylon ring.. if i could cut part of it's edges, i could use this to compress the coroplast on one side, and use the tension of the lower part to make a very tight fitting and stiff mounting
Some coroplast was cut and hit with a heat gun to force it into shape. Then painted. Although one side did get hit with too much heat and ended up dimpled. Oh well. This is my first time working with coroplast and i'll do it better when i revise this.
Finished product!
The lower grill could use some love too.. only half of it's width receives air. It is somewhat blocked off already. Taping on cloroplast will work here. I'll attack that later.
For the upper grill, i'd like to use transparent acrylic to preserve the look.
Now that i'm hip to working with chloroplast, i'd like to start making some panels for the car's underbody.
I'm noticing that between the bumper de-dent and the grill block, the car is rolling in neutral for noticeably longer already.
It has caused me to rethink how i drive it. Because the air does not act as much of a brake on the car, i have to use the brakes to fully stop at a stoplight. This makes me more considerate about how how fast i get going from stoplight to stoplight. On the other hand it's a bit annoying. I now think i understand why they don't make hyper aerodynamic gas cars.
I also have to watch my speedometer on the highway because i can end up going faster than i expect.
I do plan to fit the transmission with some teflon additives to reduce it's drag significantly. Perhaps this will allow longer coasting in gear. Right now, being in gear is too draggy for long coasts to stoplights.
I went out and bought more cloroplast, and tools to work with cloroplast. I'm loving the stuff and can't wait to start building bike fairings with the stuff.
It has caused me to rethink how i drive it. Because the air does not act as much of a brake on the car, i have to use the brakes to fully stop at a stoplight. This makes me more considerate about how how fast i get going from stoplight to stoplight. On the other hand it's a bit annoying. I now think i understand why they don't make hyper aerodynamic gas cars.
I also have to watch my speedometer on the highway because i can end up going faster than i expect.
I do plan to fit the transmission with some teflon additives to reduce it's drag significantly. Perhaps this will allow longer coasting in gear. Right now, being in gear is too draggy for long coasts to stoplights.
I went out and bought more cloroplast, and tools to work with cloroplast. I'm loving the stuff and can't wait to start building bike fairings with the stuff.
nicobie
100 MW
I got a nice pile of cloroplast from old election signs.
markz
100 TW
Your very brave.
Research away......
nicobie
100 MW
markz said:
Yep, be very careful!
I've researched those additives very extensively and they appear to be safe for long-term use.
My prediction for how fast the car decelerates in gear is so off that i had a close call with a driver merging into my lane who was not paying attention and giving enough space. I had to hit the brakes in a situation where i'd normally not. I need to take a pause on aero modding to get used to this effect, since the aero drag at high speeds has dropped A LOT.
.. on the other hand, i achieved 56.3mpg in mixed city/highway driving against a 20-30mph wind, which is astounding. 8)
Looking at the designs of very aerodynamic cars produced recently, especially the Tesla Model 3 and newer Mercedes cars, i see that the body of this car is very well streamlined; but the front bumper/grill is an atrocity compared to the Model 3:
I think there would be massive aerodynamic gains in extending this bumper out by 1 foot and adding a bit of the Model 3's 'duck bill' while i'm at it. This could be designed as an extension of the center grill section, and not look terribly outlandish.
Even in The Tesla Model 3, the front bumper is a huge source of resistance and could be improved notably.
Even though the other grill blocks are easy to design and install, I am going to wait on adding them and focus on lightweighting the car, to reduce the momentum when rolling so that the air resistance and tire friction becomes a larger proportion of what causes the car to slow down. I think lighter wheels is probably the big ticket item here. Finding some is going to be extremely challenging.
My prediction for how fast the car decelerates in gear is so off that i had a close call with a driver merging into my lane who was not paying attention and giving enough space. I had to hit the brakes in a situation where i'd normally not. I need to take a pause on aero modding to get used to this effect, since the aero drag at high speeds has dropped A LOT.
.. on the other hand, i achieved 56.3mpg in mixed city/highway driving against a 20-30mph wind, which is astounding. 8)
Looking at the designs of very aerodynamic cars produced recently, especially the Tesla Model 3 and newer Mercedes cars, i see that the body of this car is very well streamlined; but the front bumper/grill is an atrocity compared to the Model 3:
I think there would be massive aerodynamic gains in extending this bumper out by 1 foot and adding a bit of the Model 3's 'duck bill' while i'm at it. This could be designed as an extension of the center grill section, and not look terribly outlandish.
Even in The Tesla Model 3, the front bumper is a huge source of resistance and could be improved notably.
Even though the other grill blocks are easy to design and install, I am going to wait on adding them and focus on lightweighting the car, to reduce the momentum when rolling so that the air resistance and tire friction becomes a larger proportion of what causes the car to slow down. I think lighter wheels is probably the big ticket item here. Finding some is going to be extremely challenging.
thundercamel
10 kW
I'm glad that you appreciate a car's performance and handling with more than just acceleration in mind. The manual transmission alone is a huge part in making a car enjoyable to drive. Nice work so far! I have some experience with modifying my car for use around road courses.
I'm not sure what you had planned with regards to "adding reinforcement to the suspension so it can take turns quicker," but I'm not a big fan of using stiffer coil springs at each corner, as I like them to still perform smoothly over rough terrain. If I may suggest, focus on the alignment together with stiffer sway bars if the car has a lot of body roll. The torsion beam suspension in the rear probably doesn't have a sway bar, eh?
As for the alignment, my car definitely benefited from increased caster for more dynamic negative camber while steering, and add static negative camber to the front and rear as needed. The former I achieved by using a top hat with an offset hole (similar to a camber plate, but with rubber still) to move the top of the strut back and inboard. I also moved some parts around (or you could use shims) on the lower control arm to move the lower ball joint forward. The latter was achieved partially by that top hat, and the rest with camber where the strut meets the knuckle.
I personally wouldn't feel that messing with the lubrication is worth it. Pay close attention to what additives can erode brass synchros. Also the teflon could eliminate the synchros ability to do their job. When you start pushing the lever into a gear, the synchro has friction on their cone to slow down or speed up the gears rotation so that it's matched by the time it's engaged.
EDIT: Just saw that you've seen it's safe for long term use. If you have an easy link you can post, I'd be interested to read. If not, no biggie.
Skip to 1 minute.
[youtube]0Bqs-oHBBQk[/youtube]
I'm not sure what you had planned with regards to "adding reinforcement to the suspension so it can take turns quicker," but I'm not a big fan of using stiffer coil springs at each corner, as I like them to still perform smoothly over rough terrain. If I may suggest, focus on the alignment together with stiffer sway bars if the car has a lot of body roll. The torsion beam suspension in the rear probably doesn't have a sway bar, eh?
As for the alignment, my car definitely benefited from increased caster for more dynamic negative camber while steering, and add static negative camber to the front and rear as needed. The former I achieved by using a top hat with an offset hole (similar to a camber plate, but with rubber still) to move the top of the strut back and inboard. I also moved some parts around (or you could use shims) on the lower control arm to move the lower ball joint forward. The latter was achieved partially by that top hat, and the rest with camber where the strut meets the knuckle.
I personally wouldn't feel that messing with the lubrication is worth it. Pay close attention to what additives can erode brass synchros. Also the teflon could eliminate the synchros ability to do their job. When you start pushing the lever into a gear, the synchro has friction on their cone to slow down or speed up the gears rotation so that it's matched by the time it's engaged.
EDIT: Just saw that you've seen it's safe for long term use. If you have an easy link you can post, I'd be interested to read. If not, no biggie.
Skip to 1 minute.
[youtube]0Bqs-oHBBQk[/youtube]
Happy to hear you chime in.
Reinforcing the car for better cornering would mostly be done with strut bars, sway bars, etc.. nothing too extreme like full frame braces. Most absolutely not gonna go to lower or stiffer suspension because i want good ride quality still. The car actually rides a bit rougher with the weight off since the shocks/springs are functionally a bit stiffer.
If i go with custom suspension, i'd go with expensive tuneable shocks so that i could actually make the ride a bit smooshier, lol.
I have read that adjusting the alignment would help this car on the track.. probably helps in commuter driving also.. that's something i'd like to look into so i can lose less speed on turns and get away with it.
I watched the video. The point about interfering with how synchros work is absolutely worth considering and making me question that part of the plan.
I don't have the links to teflon in gearbox reliability studies anymore. I think i found them on tufoil's website.
Reinforcing the car for better cornering would mostly be done with strut bars, sway bars, etc.. nothing too extreme like full frame braces. Most absolutely not gonna go to lower or stiffer suspension because i want good ride quality still. The car actually rides a bit rougher with the weight off since the shocks/springs are functionally a bit stiffer.
If i go with custom suspension, i'd go with expensive tuneable shocks so that i could actually make the ride a bit smooshier, lol.
I have read that adjusting the alignment would help this car on the track.. probably helps in commuter driving also.. that's something i'd like to look into so i can lose less speed on turns and get away with it.
I watched the video. The point about interfering with how synchros work is absolutely worth considering and making me question that part of the plan.
I don't have the links to teflon in gearbox reliability studies anymore. I think i found them on tufoil's website.
So i called around a few places to see what painting the spoiler the factory color would be..
Generally speaking, $300-$400 to paint a little 3 inch strip of plastic :lol:
I asked a dealership if they sold the paint and they told me they buy paint from a local supplier.. called them up.. and they said they'd put the appropriate factory mixture into a can for $30-50. So i can DIY the spoiler paint job for under $100 i imagine.
With the remaining paint, i imagine i could build a variety of aerodynamic aids that have a clean look and have a stock-like appearance. I could go balls to the wall with the aerodynamics.. very appealing if i could get used to driving a car that feels as if it has no air resistance.
Dauntless
100 TW
Well, you can get started for free https://www.simscale.com/product/pricing/
If I understand you get to review work others are doing to help you get started on your own. https://www.simscale.com/projects/Ali_Arafat/aerodynamics_analysis_of_a_formula_one_f1_race_car/
If I understand you get to review work others are doing to help you get started on your own. https://www.simscale.com/projects/Ali_Arafat/aerodynamics_analysis_of_a_formula_one_f1_race_car/
Dauntless
100 TW
neptronix said:
Oh, that won't be a problem. Maybe not a perfect model. The free model tends to be low poly, maybe some details missing. If you wanted to do some finish work or something. . . .
https://hum3d.com/toyota-yaris/
https://open3dmodel.com/3d-models/3d-model-toyota-yaris-hatchback-2_115049.html
https://www.cgtrader.com/3d-models/yaris
https://sketchfab.com/tags/yaris
https://done3d.com/toyota-yaris-hatchback/
markz
100 TW
neptronix said:
Wind/aerodynamic model tests at the Nasa facilities on the horizon?
Dauntless
100 TW
markz said:
National Auto Sport Association. https://www.nasaproracing.com/
thundercamel
10 kW
Sounds good. The closer the strut towers are to the firewall (ala most front wheel drive cars), the less a strut tower brace is usually needed. Sway bars are just a spring to resist body roll, so you're on the money there. Wish you had front and rear for tuning understeer/oversteer balance (if you ever even got that extreme, lol), but you'll just have to do that with front vs. rear negative camber and tire pressures.neptronix said:
With less sprung weight, a lower spring rate and associated damping rate wouldn't be out of line. Probably all off-the-shelf aftermarket options are a lower ride height with a higher spring rate and associated damping rate to facilitate faster tire contact after a bump in a track environment though. I had AST single (rebound low rate) adjustable coilovers on my last track/street car, and I had to turn them all the way down to be comfy enough on the street.
Alignment is the best place to start to make a car corner better. Factory specs are for the average driver. However many degrees of body roll the car has should idealy be the same degrees of negative camber on the outside tires (ignoring tire deflection) for maximum cornering traction, but of course it's a compromise for straight line cruising as well. Keep an eye on the inside vs outside wear on the tire tread. For toe angle, I never went as extreme as to anything but zero toe, and of course you won't want to either for rolling efficiency. Speaking of which, I have no idea how much negative camber affects rolling resistance, but I'd guess negligible and it's worth the fun
