Lightweighting and aerodynamic optimization of a subcompact car.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 07 2021 3:28pm

The firewall is fairly close to the strut towers on this car, so the upper strut bar didn't produce a world of difference, but it was noticeable. :) I'd certainly like a rear one.. and sway bars if i can get 'em.

Oh yeah there's almost no suspension options for this car, but i do notice the weight loss so far makes the car a *tiny* bit bumpier.

I cannot even find the alignment specifications for this car online no matter how hard i try. The car is so new that it hasn't had an alignment yet. Do you think that a conservative setting would be to set the camber negative a degree or two and the toe closer to zero by 25% for a conservative compromise that increases the car's handling without affecting tire wear too much?

...also would that even bet worth paying for? are we talking about a noticeable change from a few degrees?

I'll see if i can get alignment specs for the car by calling around, if you're able to interpret and suggest something more ideal.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by thundercamel » Apr 07 2021 4:31pm

If you can feel the difference from a strut tower bar and the weight loss, then you'll notice a huge difference from 2 degrees of static negative camber. It would be worth $100 to me, if you can still get a good alignment guy for around that price, but you'll probably need aftermarket camber bolts first for the front. I don't know if your rear torsion beam suspension will allow camber adjustment... Always go to a place that has a laser alignment rack and will give you the printout showing the before and after specs. I've included a terrible scan of mine with the "after" specs on the bottom half. They already have a database of the factory specs for every car, which are those little number ranges in the top corners. If you find someone good, they'll be willing to get the toe very close to 0 and not just "within spec," and they'll be willing to go out of spec if requested such as my front negative camber shows. My goal for that car was -2.0 degrees all around. This might make some cars able to oversteer, so watch out for that. Most cars spec camber around 0 in the front and -1.0 in the rear, to make sure the car has safe understeer when pushed to the limit. My goal was to reduce understeer and increase overall cornering grip, and it was perfect. I had even tire wear, since I would frequently push the corners pretty fast.

Image

Some of that body roll that the camber has to compensate for:
Image
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 09 2021 11:24am

i installed a K&N filter and it was a big mistake. Saw a drop in low end torque.. and a hypermiler spends a majority of their time at lower RPM.. it's causing me to shift later than usual. It's gotta go.

I also found a rubber(?) stick on spoiler kit.. which i plan to use to make an underbody spoiler for the rear of the car and also some extenders for the grill cover. This will make making those tapers VERY easy.

https://www.amazon.com/Universal-Spoile ... BW7L&psc=1

I headed out to the paint place which is 20 miles away. Did 60mph steady on the highway. ~10% of those miles were city miles. Didn't have to use the AC. Pretty good conditions for a test run.
initialtrip1.jpg
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intitaltrip2.jpg
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This works out to 59.65mpg both ways.

Here's the MPG per mph for a 2010 prius... which i'm beating already. :mrgreen:
prius fuel economy.png
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Also, my prior lifetime fuel economy is 46.5mpg. But it recently bumped up to 46.6mpg.
initial lifetime mpg.jpg
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 09 2021 11:45am

Oh yes and thanks to Dauntless, i have purchased what appears to be a pretty good book about optimizing aerodynamics:
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Thanks again :bigthumb:
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 13 2021 2:10pm

The passenger mirror was deleted ( legal in Utah; expect a few arguments with cops as a result, but let's see how bad it is ) and i've got a RTV filled motor mount insert curing as we speak..
img.jpg
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In starting to tear apart the interior, i see that there's hundreds of metal bolts and screws doing things like holding plastic to plastic, whereas other areas of the car use nylon fasteners in the same situation. These metal bolts are most present in the door panels and dropping weight at the edges of the car is top priority.

There's also aluminum self tapping screws out there which are 33% lighter and in areas where fastener strength is important, but not related to crash safety, i plan to use those. otherwise the steel fasteners are kept.

There's also lots of metal brackets in the dash and center console area that could be replaced with aluminum.. i want to tackle those too.

Probably 30lbs of extra weight in this.. why not go for it.. :)

The underbody is where most of the extra metal weight is, so i think in total i have 50 more lbs to shed for a total 150lb weight drop. I expect the additional underbody panels to add 5-10lbs.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by marty » Apr 14 2021 7:45am

neptronix wrote:
Apr 13 2021 2:10pm
passenger mirror
You have gone from ridiculous to dangerous. Could be you are real talented at neck twisting to see what is happening over at the right. What happens when someone else drives your car and kills themself or someone else because they didn't see something? You dealing with a 3000 pound very scary piece of machinery. STOP making it more dangerous!
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by spinningmagnets » Apr 14 2021 9:55am

The most aero high-speed velo's look like a raindrop with flattened sides, and it used cameras feeding a series of internal screens (*old smart-phones?)

If passenger mirror deletion interests you, I'd reccomend a backup camera and right-side camera. They have gotten very cheap, and somebody's obsolete tablet device should be able to be repurposed as a display?

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by spinningmagnets » Apr 14 2021 10:01am

One of the things I learned from the aero-Civic site was that the front grille creates significant drag.

He covered the grille and found that the electric fan drew in enough air from below the engine to keep the engine temps safe. He installed movable louvers where the grill was, so he could manually adjust how much air could be forced by forward movement through the radiator, but after watching the temps closely, he found he could leave them shut almost all the time.

A smooth belly pan might be extreme. But that can provide a small benefit.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 14 2021 10:51am

Yeah, i may end up going with a camera to replace the passenger side mirror. Not sure if i need it or not. It's been 36 hours and the RTV to fill the motor mounts is still drying because we're having a sudden cold spell.

I do spend the majority of my time in the right lane and the car has a huge blind spot, so when merging to the right, i always always crane my neck over. So the passenger side mirror is not as useful as it should be.

The car has partial underbody paneling already. The sections they left un-faired are luckily very easy to cover. It'll be a slam dunk. I'd like to take Julian Edgar's advice and create these panels out of heat molded ABS.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Chalo » Apr 14 2021 11:03am

marty wrote:
Apr 14 2021 7:45am
neptronix wrote:
Apr 13 2021 2:10pm
passenger mirror
You have gone from ridiculous to dangerous. Could be you are real talented at neck twisting to see what is happening over at the right. What happens when someone else drives your car and kills themself or someone else because they didn't see something? You dealing with a 3000 pound very scary piece of machinery. STOP making it more dangerous!
Getting in the car to begin with is the safety transgression; it doesn't really matter how many mirrors it has. The most critical blind spot is moral, not optical.

Note that most trucks lack a center rearview mirror, which is in my opinion a bigger shortcoming than no passenger mirror. You share the roads with them all the time and probably don't think anything of it.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by JackFlorey » Apr 14 2021 11:58am

neptronix wrote:
Apr 13 2021 2:10pm
The passenger mirror was deleted
Delete both and replace with cameras with high brightness screens inside.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 14 2021 1:09pm

JackFlorey wrote:
Apr 14 2021 11:58am
Delete both and replace with cameras with high brightness screens inside.
Pretty much every state legally requires a mirror on the driver side, so i don't want to go that far. I spend a lot of time in the right lane, so being able to rely on what i'm seeing to the left of me is pretty important.

The Utah vehicle code does not define the size or shape of car mirrors though, so in theory i could put a much smaller mirror on the driver side and add a camera, if the mirror offers adequate visibility.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 14 2021 3:18pm

There are some very wide mirrors out there which show a side and rear view very well.

https://www.amazon.com/Rally-Panoramic- ... content-20

I like the idea of not adding more electronics to the car. Worth an experiment to see if visibility is good, which would eliminate the need for a camera on the passenger side.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 17 2021 9:42am

Okay, the stiffened motor mounts are cured after 4 days, and i finally drove the car.

MPG Gains!

With the passenger side mirror removed, i got 68.8mpg on the way to my lady's house, with no wind. This is an all time record for that route. I notice a tiny difference in acceleration at 60mph also.

I'm not sure if the stiffer motor mount is partially responsible. There's now less energy spent compressing rubber. I can feel it when i shift. The route is ~50% city driving, so this has an effect, I think this is just like how on a bicycle, suspension can eat up some of the pedal power. And the stock rear motor mount was very loosey goosey.

There is no difference in motor vibration... likely because i used a medium soft RTV. Or it's not fully cured yet, lol.

Ecomodder people say each mirror removed is worth a 2 - 3.5% fuel economy gain. The mirrors on this car are huge for it's size. Maybe i'm on the high end of this gain. We'll see in time.


What about visibility? IE how retarded is this idea?

I tilted the rear view mirror towards the passenger side and have a great short-range view of what's to the right of me. It's more reliable than the passenger side mirror was. Where it falls short is the long-range view of cars to the right. But again, i spend most of my time in the right lane. I think a wider/curved rear view mirror might be the answer.

If the mirror delete continues to show me gains.. i'd like to replace the driver side mirror with a smaller one while i'm at it.


What next?

All the nylon nuts, washers, and bolts arrived yesterday, so i want to finish the weight losses in the interior since there are so many of them to make, and complete the front grill blocks as well.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Chalo » Apr 17 2021 11:55am

That's remarkable efficiency for a street legal car. I'm a little surprised that you can't buy a car with this kind of simple but effective improvements directly from the manufacturer. Given that you can get "sports", "racing", and "off road" packages for vehicles that are unsuited for those things and unlikely to be used that way, it would be more useful and practical to offer models with features that are relevant to a daily commute.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by Dauntless » Apr 17 2021 9:51pm

Image
Chalo wrote:
Apr 17 2021 11:55am
neptronix wrote:
Apr 17 2021 9:42am
With the passenger side mirror removed, i got 68.8mpg on the way to my lady's house, with no wind.
That's remarkable efficiency for a street legal car. I'm a little surprised that you can't buy a car with this kind of simple but effective improvements directly from the manufacturer.
Here is what they THOUGHT of VW's 99mpg car 20 years ago. Since then we've seen what VW did to gain advantages.

https://www.nytimes.com/2001/09/16/auto ... g-car.html

Meanwhile, it's more fun to delve into pure fantasy. Have you thought of what mileage you could get if you cut off half your roof, most of the floor, removed the drivetrain and went CHAIN DRIVE. . . ?

Shell thought of it. A letter from 1973 that explains a little of it. http://www.opel-p1.nl/custom/testcar/wo5778a.jpg

5 ounces of gas, 14 miles. A new world record for a car that could have driven the continental United States on 10 gallons. Although, not really. It never would have survived. Nothing practical or useful about it. It's a fabulous story anyway.

So amazing that it was in the Talledega Hall of Fame when the economy melted down, so after 35 years the sold some cars nobody cared about any more. And it was bought by someone who did care. http://www.376mpg.com/

The engine sounds like it uses a system much like the one noted Conman Smokey Yunick claimed he was showing off at a press conference but instead it went up in. . . . Everyone said 'Yeah, that Smokey.' Autoracings' most renowned cheater. But I guess this one worked, no thanks to Smokey.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 19 2021 4:10pm

Some progress...

It's been dry as a bone out here in Utah and i believe i touched something with a static charge..my car would not turn off until wires were unplugged.. and the infotainment screen that i hate isn't operating properly anymore either.

However the car is turning off and on normally now.. only one episode of that.. hopefully the last.

Unplugging the battery deleted my lifetime fuel economy figure. Maybe for the best, as the car is not the car it used to be.. it had crawled up from 46.5mpg to 46.7mpg before this event.


A shit ton of metal bolts and nuts have been replaced with nylon ones in areas where crash safety is not a factor and plastic to metal or plastic to plastic interfacings do not require lots of strength. Mazda/Toyota missed a lot of opportunities. Most of these are M6 x 1.0 bolts and nuts made of steel.

There's still scads of nuts ( M6 mostly ) which are way way way too long and i think it would cost less to replace them with shorter ones than continue buying cutting wheels, lol. So i'm out to find some aluminum ones.

Parts of the headliner are rather heavy to a point where i noticed a minor difference in cornering after removing that weight up top. The weight is in the 'map light' area.


I have an ultrawide 11" add on mirror now and the view is superb. I can easily see out the back windows and the view is far superior to the side mirrors. Unfortunately this view includes part of the driver and passenger side's faces too, which is distracting, and i plan to do a strategic cut or blockoff to make this mirror better.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by nicobie » Apr 19 2021 4:35pm

McMaster-Carr is your friend.

https://www.mcmaster.com/aluminum-bolts/

I can order in late PM and get the order in next days mail.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 20 2021 10:50am

That was a good lead. They have metric nylon nuts or nothing. And ship super fast.

Their aluminum bolts are expensive..i found a race car fasteners site that sold them for a bit less, then read that aluminum screws won't work properly in steel. That's a bummer and a half.

I did find shorter metric screws in quantity at the home depot though.

As soon as i can find my caliper or buy one, i'm going to give EJOT's engineering department a call. Apex fasteners sells their aluminum plastic to plastic screws in quantity, but nobody has been able to identify the plastic to plastic screw my car is chock full of.

Here's a nice flyer on the Delta PT screws that EJOT produces:
https://www.ejot.com/medias/sys_master/ ... -Flyer.pdf

The issue with the car not turning off happened again. It seems to happen when i have the new more powerful headlights on. Something probably has a weak ground... or i need to beef up the wiring to the headlights to account for the additional electrical load.

I've adjusted the rear view mirror for excellent visibility, but the second you have a passenger, you lose that passenger side visibility. I think what i would like to do instead of this passenger side mirror delete is go with smaller aerodynamically optimized mirrors. I need to go on the hunt again.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by marty » Apr 20 2021 12:35pm

neptronix wrote:
Apr 20 2021 10:50am
The issue with the car not turning off happened again.
Ignition switch or a relay. Try taping on the suspected bad relay with a screwdriver handle.

If you don't have one? BUY a service manual.
Last edited by marty on Apr 20 2021 2:42pm, edited 1 time in total.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by marty » Apr 20 2021 12:46pm

I know nothing about this. Looks like paper books.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 20 2021 1:57pm

Not going to go down the road of looking through a service manual. I have a modified electrical system to a non-stock state and the best course of action would be to revert it to a stock state before diagnosing it.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by marty » Apr 20 2021 2:42pm

Forgot to say.... More service manuals here:
https://www.alldata.com/diy/en
or
https://eautorepair.net/Marketing/Default.asp
or
Just leave the car running so it will always be nice and warm in case ya want to go for a ride.
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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 21 2021 1:00pm

3 days into a bolt hunt.. :lol:
No company seems to know these screws.. not even EJOT or Stanley fasteners.

I found out that the 100-200 sheet metal screws used in the door panel, dash, grill, etc etc etc are "#10" screws, but in all screws of this size, there's totally random thread distances, thread lengths, thread angles, etc etc etc. So "#10" just refers to diameter.
So you can forget measuring them and calling up a company to beg them to sell you a similar screw.

I went to multiple hardware stores with a caliper in hand and found these:
https://www.amazon.com/Hillman-Group-37 ... B00IAVINB4

They're a ~95% match.

The second you find the 3/4ths inch version, they have a totally different thread.

Ah well, i can get to the excessively long ones and that's as good as it gets. Another 3 days to get an other extra half pound out just isn't worth it.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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Re: Lightweighting and aerodynamic optimization of a subcompact car.

Post by neptronix » Apr 26 2021 3:10pm

Just a quick update.

I've shed a few more pounds with bolt shortening and nylon and am feeling it in the car around corners and really like it. A half pound of extra bracket and bolt length came off each seat which is nice. :)

Did drive the car around a bit without the passenger seat and loved how she handled.. it finally met the definition of what i'd call a sport compact. But the seat had to come back, darn.


The area around the battery tray was attacked and a few brackets were deleted or modified quite easily.
The ECU is now attached in a way that it vibrates less than the OEM design...and the mount is lighter.

Something i never thought about is the weight of the lead acid battery. Mine's the size of something that would be in a V8/V6 car and weighs 35lbs. I have no clue as to why this car has such a large battery. Perhaps an oversized parasitic drain.

Braille makes low internal resistance AGM batteries for cars between 6 to 21lbs. The 15lbs one seems very reasonable and is recommended for use in cars larger than mine. Mine is oversized so i should keep it somewhat oversized.
20lbs off the frontend would be huge and almost be a 1% weight loss of the car's total weight.

My battery has another few years of life left in it, so i'd have to find a donor for my current one before replacing it, otherwise it goes to waste which is the last thing you want to do when trying to improve the impact of your car.


To complete the first round of weight reduction ( fasteners, brackets, things which aren't necessary for safety or aesthetics ), i just need to attack the bottom of the car and also look at the bumper again now that i've got a pile of appropriate aluminum fasteners on hand. Then i can get to doing things like creating replicas of heavy steel pieces which could work just as well as aluminum pieces.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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