Prius 75-91mpg
 

Hey folks. This is my work prius, since the photo the aircon, passenger airbags, heater matrix and numerous small parts have been removed. It passed uk MOT test. The main difference in mpg is temperature, for me I put down to transfer efficiency being increased in the summer weather, notably above 25c

https://i.imgur.com/06RiPaC.jpg


With further aerodynamic changes and new lighter parts (seat, windows etc) eventually I expect 80-98mpg

I’ve not seen a gutted Prius before, but I applaud the effort... weight is one of the biggest factors in city mileage, which the HSD is already optimized for...

How much weight was lost?

I'm guessing these are imperial mpgs, so 62-75 mpg US. Still very impressive!

How much did you save weight? I failed MOT on my old porsche when I had door panels removed? They said sharp edges are not allowed but there where no edges on the door frames

That interior wouldn't pass the yearly MOT (technical inspection) here either

You need to talk with Peter Perkins :)

http://www.solarvan.co.uk

You've already made your Prius a 1-seater anyway, may as well go whole hog with the light weight of an Insight...

Hey samwiche, wow thanks. I knew of the newer insight and decided against it but didnt know of the mk1. hmmm

Much appreciated :) :thumbup:.

A couple of breakdown companies cover cars without a spare wheel - RAC and AA are not obliged to help


n/b regarding the initial post and measurement. The highest mpg was steady 49mph, little or no gradients with no extra equipment in the car, no cruise, no drafting. The worst was 80mph average with gradient changes and overtaking. I sometimes draft, in the fast lane x5/4x4's are good and behind lorries in 50 zones, although I've not measured that as results are not consistent. Also when I mentioned temperature the results were mid-summer and winter results will be considerable less, maybe 15mpg less

https://ibb.co/ZM8BrT0

this is after the first stage, before the computers got ripped out

https://ibb.co/ZM8BrT0


..As far as I recall it was'nt quite a full tank, maybe 8/10 but still I was happy. Also see the ambient temps, do make a big difference

Pretty nice numbers. Probably not a comfortable ride but I appreciate a purpose-built machine.

Thanks

..Comfort to me is retaining 96% of gross yield and fuel is the main cost of the business. I only miss the radio and I could get a 150 gram mp3 player if it was a real bugbear

Gen 2 Prius
 

FYI
I am considering your light weighting process of vehicle on my 08 Gen2 Prius


Additionally am considering using Lexan to replace some of the rear window glass and possible rear hatch

Don't expect much increased fuel economy from reducing weight (if any). At highway speeds added weight is a pretty small part of the fuel economy equation, though certainly non-zero and if you're aiming for max, I'd say go for it.

:thumbup:

You'll probably mostly notice better acceleration and probably better handling but at the expense of greatly increased cabin noise and ride harshness.

Never understood modding a car at great expense and time to go faster when you can just buy a faster car. If it's improved fuel economy, decreasing the weight isn't going to help much, especially on a Prius.

I removed the rear windshield wiper on my Prius. That's the extent of the modding I've done. Certainly don't want to ruin the thing.

This weeks change, grill block

http://i65.tinypic.com/16gc4dg.jpg

http://i64.tinypic.com/21r0o1.jpg

Carbon fibre has been ordered for more parts.

n.b I did lose a race with a porsche on sunday which was really annoying, and he looked like a nob

http://i67.tinypic.com/bg8ner.jpg

http://i67.tinypic.com/2rgjjo6.jpg

Theres a few other more difficult mods

Hey ya'll like my new clock?

http://i63.tinypic.compr4o8.jpg

http:// //imgur.com/a/6zZhqh1

image wont upload, 11g clock and vmeter

https://cdn1.imggmi.com/uploads/2019...bee8e-full.jpg

New windows today

New stuff
 

Ive made window pillars from carbon to support the 2mm plastic. Also have purchased 24m of fibre to replace some rear sections, bonnet and wings/fenders. The wheels are pretty lightweight and not much heavier than carbon ones. Im up to just over 100mpg in mild weather but think with smaller profile tyres (45), a 2.5" lowering and the new parts I can get about 110-115 as an absolute maximum. A respray in autumn too, for asthetics, wont affect friction drag to any noticable extent

mirrors
 

I dismantled the mirrors and cannot find an easy way to remove the motors. Currently they are 800g each but will be given attention next year

You might be surprised to learn, but I did some math yesterday and it turns out the inertia of a wheel actually goes down as the aspect ratio (and thus overall diameter) goes up, because it spins more slowly. So, in effect, a 165/80r14 tire is "lighter", inertially speaking, than a 165/40r14.

Going more narrow is always a win, but don't compromise safety.

There's also gearing to consider. I know a Prius has "infinite" ratios, but going up or down in size may have unintended consequences.

You mean angular momentum? Rotational inertia is independent of speed.

All that as a prelude to saying, I don't get that result using representative tire dimensions and weights from Tire Rack--for the 185/55R14 and 185/75R14 I compared just now (they don't list any 165/xxR14), the larger tire still has higher angular momentum....

Maybe I'm confused by the terms, but the math works out that the energy stored in a spinning tire is very slightly less in the tire with a larger diameter, all else being equal, if you want to be traveling at the same speed. It's counter-intuitive but the reduction in RPM is worth more (slightly) than bringing the mass closer to center and spinning it faster.

Angular momentum is likely the term I wanted.

Wheels
 

Thanks, they will be reduced from 65 to 45mm. Only for weight, car height and acceleration. Width will be slightly increased from stock as they are now

Unfortunately I think this may undermine what you're trying to achieve.

By going smaller, you *effectively* make the wheels heavier, because they have to spin at higher RPM for a given road speed. This is normally close to a wash, but by going wider at the same time you're definitely going to cause the wheels to hold more angular momentum, even if they weigh less on a scale.

Most cars would "feel" like they accelerate more quickly with smaller tires, but it would be because they're now geared lower. I don't know if this applies in a Prius.

You would achieve your goal of lowering the car, but you'd also likely hurt both aerodynamics and rolling resistance (all else being equal) with a smaller, wider tire.

I've mulled this over for a few days now (and gone back over my physics notes!). When you say, "all else being equal," are you including mass? The tires I used for my calculations weigh, according to Tire Rack, 13 lbs for the 185/55-R14 and 16 lbs for the 185/75-R14, which is quite a bit different. Considering the energy of a rolling tire/wheel, remember that rotation is not the only component we have to consider; rolling = rotation + translation, and Krolling = (1/2)mv^2 + (1/2)Iw^2. For that taller tire in my example, I is larger because of the larger radii (I is a function of the squares of the inside and outside radius for the "disk" of the tire tread), but its lower angular velocity, w, is not enough to counteract that increase and its overall angular momentum is larger. Plus, the higher mass means the kinetic energy of translation is higher as well, all of which results in a higher kinetic energy of the larger tire.

I might play around with this some more using other tires and their masses; this might be enough to split into a new thread.

Hi yes, the wheels may weigh a very small amount more/equal, yes the gearing is changed and aerodynamics is changed. Lowering the car increases the pressure above and reduces the pressure underneath, helping to hold the car down. Pressure drag is also increased but a small sacrifice for race situations. I dont think over 107mpg is possible with this chassis/engine/surface area

n.b unless the night temps are above 30c and theres no traffic

So this thread was about reducing weight, but we still don't have an answer of how much weight was lost.

The weighstation is closed down but will find one at some point. Quarter lights and boot to be replaced next month

[IMG]https://cdn1.imggmi.com/uploads/2019...d24a6-full.jpg upload[/IMG]

[IMG]https://cdn1.imggmi.com/uploads/2019...872cb-full.png upload[/IMG]

Not everything, posting pictures is difficult. Moulding replaces spoiler too. Also made some carbon pillar supports for the plastic windows. Hovering around 100 mpg (26c ambient). Will crack on with bonnet/wings/bumpers in the autumn when I have more time

Glass/spoiler 8.35kg

Carbon 2.05kg

Quarters and the narrow smoked glass will be done next week. Will make a poly viewing slot

n.b Im getting used to carbon, I made a pillar support for underneath and its more rigid than needed so I recon 300g could have been shaved off with selective reinforce points

More rigid than the glass incidentally!!!

Need a better website with cut paste photo upload

You should be able to attach images directly when posting. Alternatively, I use imgur for hosting and put img brackets around a direct link to the image.

I can't do it and imagegur takes ages. I'll do more in batches next time. Thanks

Well they worked yesterday and I cant see a way to attach pictures

Oh...thanks its in advanced??

Unfortunately none of your images work for me.

Heres some it's still taking ages as the pictures are on my phone

Theres a pillar underneath I made from casting a hoover pipe on the back of the glass, it strenthens but might have been overkill

Also the bits are where the wind blew while I was indoors and leaves and tree bits landed on it and wont come out

All done, its easier to make carbon fiber than post pictures. The tape it just to hold it down while the panel bond goes off. Ive ordered enough stuff to do the front end. Getting it sprayed will be the most expensive part

The lines are where the sheets are folded in the post, you can get it rolled but more expensive...

Are you replacing the back glass with carbon fiber?

Hi, yes it replaces the rear glass and spoiler and light. The boot only needs one lift strut too now. I really want to replace the smoked glass section too at some point

..I plan to do the quarter lights next week, according to calculations they weigh altogether 1.6kg, the carbon fibre will weigh 210g. I can use quite thinner layers as it's narrower support distances. After the glasses it becomes quite difficult to reduce weight