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-   -   Airdam - suprise result! (https://ecomodder.com/forum/showthread.php/airdam-suprise-result-20809.html)

kingsway 03-03-2012 07:58 PM

Airdam - suprise result!
 
My little 3 spd automatic Daihatsu clone (Perodua Kelisa) badly needs some help in reducing FC.




http://a2.sphotos.ak.fbcdn.net/hphot...64485181_n.jpg



I've already fitted new Michelin Energy E3B tyres - one size up and inflated to 40psi.
-
I have a grill block - which certainly speeds warm-up (3 minutes!)

But I suspect that it is about as aerodynamic as a brick. I've mentioned elsewhere that on a cost-down test it would slow from 50mph to 40mph in 14 seconds - compared to 34 seconds in the case of my (much heavier) VW Golf Wagon...

Today I tried a simple air-dam using 5inch lawn-edging. It isn't ideal, as it is slightly too low (being below the lowest items under the car) and is also more flexible than I'd like. It is only 1mm thick plastic, and I am pretty sure it must tend to fold back under air pressure at speed. So I wasn't very hopeful as far as results are concerned.

But to my great suprise, when I did the cost-down test again, from 50 to 40 mph, instead of slowing in 14 seconds, it took nearly 20 seconds!!! (I repeated the test several times)

Now, it was just a quick and dirty test - with no account of wind (although the air did seem fairly still) but it does look like a very encouraging result.

http://i278.photobucket.com/albums/k...-front-end.jpg

mcrews 03-03-2012 08:09 PM

Holy Crap Batman!!!!!
tha't great!
THe only thing better would be it it was just layin around the garage and didnt cost any money!!
Actually looks good.
Of course, sight uphill drive ways will take on a new 'look'!!!

kach22i 03-03-2012 09:29 PM

Will the authorities allow you to do some of the crazy stuff (body modifications) we get away with here in the USA?

Something over that rear window would help out the old bread box.

kingsway 03-04-2012 12:02 PM

I see plenty of youngsters who ruin their cars with bizarre body-kits, so I'm guessing my few mods will be acceptable!

I did find a source of body-kit parts in Malaysia, but the cost of shipping etc means it probably would not be worth the expense.

I'm now thinking of finding some better material to make a permanent air-dam, and am looking for some guttering that might be suitable for sode skirts.

I am very keen to try a Kammback of some sort - but making something that doesn't look like a load of ahem... 'manure' is the difficulty. :confused:

gone-ot 03-04-2012 12:09 PM

...curious, but how much "ground clearance" do you have? Can't really tell from your head-on picture. If it's much greater than 5-6 inches, then your airdam results are probably 100% justified.

drmiller100 03-04-2012 12:48 PM

air under a car is BAD for drag.

Congrats!

MetroMPG 03-05-2012 12:55 PM

Quote:

Originally Posted by kingsway (Post 290959)
But to my great suprise, when I did the cost-down test again, from 50 to 40 mph, instead of slowing in 14 seconds, it took nearly 20 seconds!!! (I repeated the test several times)

Now, it was just a quick and dirty test - with no account of wind (although the air did seem fairly still)

Wow. That seems really encouraging!

If I were you, I would want to do the test under identical conditions (excuse me if my reading of your test is wrong - I got the impression you did your coast downs on different days). I'd want to be sure the effect is from the mod, and not something like a tailwind or the wake from vehicles ahead of you, or ???, etc.

Why? Whenever I do a mod, I always say to myself: "there is a remote possibility this mod could in fact be making things worse." The only way to know for sure is to do the best test possible and be careful I don't accidentally deceive myself into leaving a bad mod on the car!

Grant-53 03-06-2012 01:42 AM

If the lawn edging is too thin, try some strips of rubber cut from those large mud flaps on trucks.

kingsway 03-06-2012 10:13 AM

I still need to try some proper tests. But the results do seem to be fairly consistent.

This encouraged me to try a similar airdam on my VW Wagon. I tried some before and after testing this morning, with quite different results. I could find no measurable difference with or without the airdam!!! The VW already has quite a low ride height - maybe of the order of 5 or 6 inches - so the dam kept scraping everytime I cornered, or went over a bump...

The little car, in contast, still has 3 or 4 inches clearance below the airdam. The airdam itself is 5 inches deep - so is about 4 inches below the bottom edge of the front bumper/fender.

The biggest variable I have found, in my limited amount of testing of the VW, is transmission temperature! If I do a coast down test when the engine is just at running temp, the time to slow from 50 - 40 might be 21 seconds. After running the car for an hour and getting everything properly warm, the time is then 34 seconds!

I am seriously considering refilling the VW with fully synthetic MTF... The cost might well be worth-while.

(I may do the same for the little automatic, too)

kingsway 03-06-2012 10:49 AM

Better photos (of the successful airdam).
 
http://i278.photobucket.com/albums/k...ua-airdam2.jpg

http://i278.photobucket.com/albums/k...dua-airdam.jpg

Similar car - no airdam...

http://i278.photobucket.com/albums/k...2-16762-c2.jpg

:thumbup:

The main question remaining is - will the airdam on the little automatic make a noticeable difference to my fuel consumption?

johnunit 03-06-2012 03:59 PM

I'd hazard a guess that it will. However, seeing that you appear to be a driving instructor, it may well not see enough high-speed driving to show a difference.

kingsway 03-07-2012 10:27 AM

I still have to drive between customers - and pupils nearer the the test will certainly be driving at the national limit - 60 or 70 mph, depending on the road!

Just as a matter of interest - I've started making pupils aware of my Ultraguage. I show them the difference in consumption -which can be quite a lot - when using the correct gear. I also find DWB (Driving without brakes) is an excellent way to encourage planning and anticipation. They often drive and change gear much more smoothly....

MetroMPG 03-07-2012 10:33 AM

Out of curiosity: do you actively teach efficient driving techniques? (Meaning: is it specifically part of the curriculum?)

I taught driving part-time for a couple of years while I was a university student. Efficiency techniques were the focus of one of the 12 in-car sessions that made up the course, and it was part of the classroom section as well.

A ScanGauge/Ultragauge for that in-car lesson would have been a fantastic tool.

skyking 03-07-2012 11:35 AM

Quote:

Originally Posted by kingsway (Post 291814)
I still have to drive between customers - and pupils nearer the the test will certainly be driving at the national limit - 60 or 70 mph, depending on the road!

Just as a matter of interest - I've started making pupils aware of my Ultraguage. I show them the difference in consumption -which can be quite a lot - when using the correct gear. I also find DWB (Driving without brakes) is an excellent way to encourage planning and anticipation. They often drive and change gear much more smoothly....

No doubt. That was how I was raised by my dad, look far enough ahead to not need brakes.
For the last 25 years I have made a game out of it with my wife. My family is a 3 hour drive across the mountains, and she can sleep in the car. My big challenge is changing freeways and negotiating interchanges without waking her up. :D

kingsway 03-07-2012 12:23 PM

DWB is certainly a more relaxing way to drive!

'Ecodriving' with the emphasis on producing less CO2, is a small part of the syllabus here in the UK. But only a very small part.

I'm considering the idea of trying to offer some coaching sessions on how to be more fuel-efficient. Having immediate feedback on the dashboard is the key... Driving to a vacuum-gauge is much more boring, and you start to wonder if it's worth the trouble! :turtle:

This would only be viable with my bigger car. With the little automatic, if I hypermile my brains out I can get a maximum of around 39mpg (imp) as against 36mpg (imp) normal driving...

However I did another coast down test from 50-40 today in the little car.
When the engine has just reached running temp, it takes 9 seconds to slow to the lower speed. When the car is thoroughly warmed-up, the time goes up to 15 seconds (today there was a headwind on both tests)

So the temperature of the transmission appears to make more difference than anything else! I looked for some fully synthetic ATF today. but could see only semi-synthetic... Might help a little?

kingsway 03-10-2012 05:34 PM

I've now done some slightly more valid test-runs. I found it very difficult, if the traffic is quiet, theirs too much wind or vice versa...etc etc !

Having discovered what a big difference in drag there is between a warm and a cold transmission, I pretty much convinced myself I was originally mistaken when I thought it was the airdam that seemed to be reducing drag.

I tried some coast-down tests today with the dam both on and off the car. I made sure both engine and transmission were properly warmed-up..

I'm not going to claim any great accuracy, but the airdam undoubtably has a quite noticeable effect!

The time to slow from 50 to 40 is, on average, about 3 to 5 seconds longer with the airdam in place.

The most suprising thing about this is the fact the dam is so flexible, it could only be folding back under the car to at least some extent under the influence of the oncoming airflow - so perhaps if the final version is more rigid the effect may be increased?

On my last tank-full I saw an average consumption of 43mpg (imp) - up from 36mpg previously. (P&G was the major reason for this)

When I get time, I'd like to try a full under-belly pan..

allenh318 03-17-2012 08:25 PM

Does anyone have any test data on a front air dam?

RunningStrong 03-18-2012 06:28 AM

Quote:

Originally Posted by kingsway (Post 291814)
I still have to drive between customers - and pupils nearer the the test will certainly be driving at the national limit - 60 or 70 mph, depending on the road!

Just a quick OT, do you tend to start learner off-street in car parks and such?

My first lesson involved driving on the street 10 minutes in and doing 60 mph on the way home.

kingsway 03-18-2012 06:41 AM

Quote:

Originally Posted by RunningStrong (Post 294197)
Just a quick OT, do you tend to start learner off-street in car parks and such?

My first lesson involved driving on the street 10 minutes in and doing 60 mph on the way home.

Where possible, yes. But it usually isn't possible *, so it's a matter of finding an area that's as quiet as possible - one of the challenges of being a Driving Instructor in this crowded little island! ( I have great sympathy for those ADI's who work in places like London....)

I do have the advantage of also having a little automatic car - so I usually start a novice off in that, and switch them to the 'manual' once they're a bit more confident with the basics of making it stop, start and go in the right direction.


* We are usually banned from most car-parks! The chances of a learner in a dual-controlled car, under the supervision of a qualified ADI, hitting a car in a car park are almost zero - but a customer will complain to the supermarket, who are then worried they might be liable if something did go wrong, so we get kicked out. Not sure where people think novices are supposed to learn... Most of my pupils can park a lot more safely and accurately than the general public! (Like all Instructors, BTW, I carry a couple of million Pounds worth of Public Liability Insurance)

RunningStrong 03-18-2012 07:02 AM

Ah the wonders of living near one of Thatcher's enterprise zones, an empty car park is never far away.

kingsway 03-18-2012 07:11 AM

Quote:

Originally Posted by RunningStrong (Post 294200)
Ah the wonders of living near one of Thatcher's enterprise zones, an empty car park is never far away.

There are none around Cambridge - that's for sure. Most of my clients are foreign licence holders come to work locally. The recession is much less visible around here...

Sven7 03-20-2012 03:12 PM

Have you found someone to confirm whether the dam is folding under? I imagine someone standing on the side of the road, or even looking from another car, could tell you conclusively.


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