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Jimny aerodynamics (seems redundant i know)
http://auszookers.com/forum/viewtopic.php?f=37&t=46755		 Page 1 of 2
Author:  Jezza86 [ Wed Jun 25, 2014 11:01 am ]
Post subject:  Jimny aerodynamics (seems redundant i know)
has anyone played with something or tested a idea that improved their fuel economy? aerodynamics are the biggest loss factor on any car trying to travel fast so starting there.
The other day i got questioned on my fuel economy history, and it went something like this
I was getting 7l/100, a 40mm ome lift and bullbar made it 10l/100, a 75mm lift made it 12l/100, bodylift and 30's made it 14-15l/100 and the auto transfer geared it back up so got 12-14l/100
a few other people have mentioned that arb and JML bars appear to have caused a noticeable economy drop, as did a bodylift and 30's
this may seam like a redundant, silly idea, but when you only have a 40l tank and fuel is $2.17/L it limits things bit more and becomes a concentration (<spelling> consideration).
Author:  pete_79 [ Wed Jun 25, 2014 11:12 am ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
I remember reading another forum (not AZ) a long time ago where someone had a good comparison of the drag co-efficient on a Jimny to other small road cars. The numbers where surprisingly close.

But I can't remember exactly what they were or what forum it was that I read it on. Doesn't help much I know...
Author:  JayKay [ Wed Jun 25, 2014 11:13 am ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Subscribed to this one :)
Author:  Jezza86 [ Wed Jun 25, 2014 11:24 am ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
pete_79 wrote:
I remember reading another forum (not AZ) a long time ago where someone had a good comparison of the drag co-efficient on a Jimny to other small road cars. The numbers where surprisingly close.

But I can't remember exactly what they were or what forum it was that I read it on. Doesn't help much I know...

cheers pete
that really doesn't surprise me, i mean 7l/100 is doable in stock form, and the rear end is a barn door.
im willing to experiment and even chuck some fuel into it to do it properly (scientifically, in triplicate and stuff)
i know why my car uses so much fuel, but without undoing the bodylift and bullbar it would be interesting to see what could be changed /improved.

at the moment i'm leaning to a removable front skirt for example.
Author:  Red89 [ Wed Jun 25, 2014 11:31 am ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
You could mess with tyre pressures and treads as well.
Author:  atari4x4 [ Wed Jun 25, 2014 11:41 am ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
i think about how much more wind the underbody components are getting after the lift & how much more exposed the front end is as you said with a bar on.

with a background in sailing/windsurfing i've always had aero in the back of my mind & think about how much effort it takes to hold your palm out the window at 110kph, hell even a broom stick UHF antenna would be a bitch to hold at that speed & is one of the reasons why i haven't fitted any racks to the blagon yet,the other is i'm slack. if you have racks, maybe try removing them. i do have the advantage of not having a live axle sitting out in the breeze up front & everything is pretty well tucked & do wonder if the skid plates on mine at all help the situation?

then there is the extra weight from wheels/tyres, barwork & accessories etc.

i think you're going to be fighting a loosing battle without either lowering it, loosing some weight or adding spoilers. :lol:
Author:  Jezza86 [ Wed Jun 25, 2014 11:58 am ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Red89 wrote:
You could mess with tyre pressures and treads as well.

nothing is offlimits, however i have found my km2's are quietest and most efficient at 25psi front and rear pompoms

atari4x4 wrote:
stop the wind hitting the under body and get a spoiler

fixed it lol. i like your point atari. round bar isnot aerodynamic. the axles, wheels, and barwork are mostly round.
if not, typically flat or square. hence i see so much room for improvement.

i used to fly gliders so am also familiar with the basic principals. so hoping this gets interesting :)

Image
Author:  Jezza86 [ Wed Jun 25, 2014 12:08 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
as my largest drops in fuel economy have been when ive changed height, but not much mass ill skip weight changes for now. it can be after aero changes.
example is the rear tyre carrier never changed my fuel economy despite weighing 50 kg with a 30' on it. i do think the old rear bumper was a bit of a air dam without the front bumper stopping air getting under the car but.
Author:  atari4x4 [ Wed Jun 25, 2014 12:14 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
JayKay wrote:
Subscribed for pics of spoilers :)


:lol: fixed

yep, i see round bar & slabs of flat surfaces everywhere.

in all honesty, i'm keen to see what sort of improvements you can make without getting silly... a front skirt might be the answer, the question is how to make it work? even something like a front skid plate that came from the lower edge of the bull bar back down to protect the drag link/panhard like what you can get for the defenders. but i reckon it would be interesting to put yours over a weigh bridge & see where you stand.

eg
Image

Image

:EDIT:

Jezza86 wrote:
i do think the old rear bumper was a bit of a air dam without the front bumper stopping air getting under the car but.


the parachute effect!!! huge problem with go fast cars & it would have been catching a fair bit of air.
Author:  Chop [ Wed Jun 25, 2014 12:15 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Yeah the old exposing of the nether regions trick does it everytime!
Author:  Jezza86 [ Wed Jun 25, 2014 1:39 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
atari4x4 wrote:
in all honesty, i'm keen to see what sort of improvements you can make without getting silly... a front skirt might be the answer, the question is how to make it work?


and not look like you just slapped recycled plane to your car which would attract the plod is part of it too.
obviously everything done has to be road legal, and potentially reversible to go wheeeling and not snag things.
those bash plates also look good.
Author:  jake84 [ Wed Jun 25, 2014 4:37 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
atari4x4 those bash plates look good dude
Author:  zukenutter [ Wed Jun 25, 2014 8:33 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Interesting thread. My Economy dropped from 8L/100 (stock) to a fairly consistent 9.75'ish/100 at all stages of mods, even with the 1.8. I did one return run to Sydney with no spots or rack and got about 9L/100.

Wide tyres add a lot of drag due to the extra rubber hitting the road.

Also I think most added wind drag comes from exposing the front tyres to wind resistance. Tyres are rotating forward, wind is hitting it in an opposing manner, part of my reason for the new bumper with less cut away.
Author:  Jezza86 [ Wed Jun 25, 2014 8:46 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
top of tyre (muddy tread too) doin 200KPH realative to windspeed. was thingking of this earlier but cant do much bout that without increasing unsprung weight, which is probaly a nono
Author:  Jezza86 [ Wed Jun 25, 2014 8:51 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
hubcaps (of all things, on a sunny) would likely help. 4 15" holes have to disrupt some airflow doing 100kph. hubcaps should smooth it off. but that might be borderline silly
atari4x4 wrote:
i'm keen to see what sort of improvements you can make without getting silly...
Author:  zukenutter [ Wed Jun 25, 2014 8:56 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
I was also wondering about what your high flow exhaust may have done to your fuel usage. Different topic though.
Author:  zukenutter [ Wed Jun 25, 2014 8:57 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Moon discs :D
Author:  Santos [ Wed Jun 25, 2014 9:35 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Just yesterday i was reading about diffusers. Maybe something to consider now that you ride height is up and explain problems with bar work.

Wide tyres and higher rotational mass in all my readings consistantly have killed fuel economy
Author:  Jezza86 [ Wed Jun 25, 2014 9:53 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
rotational mass isa factor in acceleration, thus for city driving is realavent. but in city driving your also close to fuel stops so the need for long range capacity isn't there.
me on the other hand... im trying to get to the nearest clark rubber store
Image
so range is more of a factor. at constant speed on dirt the rotational mass is allready accelerated.
friction is also lower on dirt.

ride height however has everything to do with this. i have 5 inches of extra exposed height, and a front skirt/ diffuser may help

i have already sourced some conveyor belt. now to just attach it in a less silly way
Author:  atari4x4 [ Wed Jun 25, 2014 9:55 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
holy shit, you really are in bumbfuck nowhere. :lol: 8O

if you find something on the clark website, i'd be happy to pick what ever up & post it up you way.
Author:  Jezza86 [ Wed Jun 25, 2014 9:58 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
zukenutter wrote:
I was also wondering about what your high flow exhaust may have done to your fuel usage. Different topic though.

itt made me drive at WOT a lot more often for a bit, which upped my usage a tad but in all it appears to have drooped .5l/100 off my usage when im not driving like a spastic.
Author:  Paulw [ Wed Jun 25, 2014 10:16 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Santos wrote:
Just yesterday i was reading about diffusers. Maybe something to consider now that you ride height is up and explain problems with bar work.

Wide tyres and higher rotational mass in all my readings consistantly have killed fuel economy


It's funny I have been thinking about fitting diffusers along the top of the rear door (ala evo 9) to help with highway economy, for a while now.
Author:  Jezza86 [ Wed Jun 25, 2014 10:26 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
paul, you need sonic hair for your car (vortex breaker)
Image
Image
Author:  atari4x4 [ Wed Jun 25, 2014 10:27 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
and yet i copped shit for my roof spoiler from the arseclowns on here. :roll:
Author:  Jezza86 [ Wed Jun 25, 2014 10:32 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
atari4x4 wrote:
and yet i copped shit for my roof spoiler from the arseclowns on here. :roll:

wait till you see what i have in store for my axle housings...
Author:  Paulw [ Wed Jun 25, 2014 10:33 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
I sorta want a roof spoiler :oops: (suzuki wanted $700)
IMO they look good, I don't care if some dudes I don't care about think its gay
Author:  Santos [ Wed Jun 25, 2014 10:34 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
atari4x4 wrote:
and yet i copped shit for my roof spoiler from the arseclowns on here. :roll:


But did you post it in the flame free rainbow filled noob section ??? :peaceout:
Author:  atari4x4 [ Wed Jun 25, 2014 10:37 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
Santos wrote:
atari4x4 wrote:
and yet i copped shit for my roof spoiler from the arseclowns on here. :roll:


But did you post it in the flame free rainbow filled noob section ??? :peaceout:


pm's steve to get my build thread moved to the rainbow & lolly pop section.

back on track...

Jezza86 wrote:
atari4x4 wrote:
and yet i copped shit for my roof spoiler from the arseclowns on here. :roll:

wait till you see what i have in store for my axle housings...


care to share your thoughts & idea's or is it secret squirrel stuff?
Author:  Jezza86 [ Wed Jun 25, 2014 10:55 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
test design, ductape a triagle shaped bit of foam to my axle housing

so ~@~@~@~O <====== becomes ====<O======

@~@~ is obviously voracities coming off the axle housing....the O

who needs MS paint anyway
Author:  Jezza86 [ Wed Jun 25, 2014 10:57 pm ]
Post subject:  Re: Jimny aerodynamics (seams redundant i know)
and the front skirt, of course... i got a lot of conveyor belt.
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