WS Undertray really works!

paulo7 · 27-10-2011, 11:06 PM

Hey guys,
Remember this???:

http://www.fordforums.com.au/showthread.php?t=11331515

It was the long hot debate about whether an undertray on a WS or WT would actually be effective on reducing fuel consumption and increasing power.

Well I put my money where my mouth was and bought one a couple of months ago and the result is....

cha--ching!!

it actually does work in reducing fuel consumption, (...and of course it wouldn't increase power!)

I drive about 600kms a week on 60,80,100kms zones to and from work.

I always keep my fuel receipts and work out my consumption tank to tank.

Without undertray: 7 tanks with a range of 6.22 to 6.78ltrs per 100 average at 6.49ltr per 100kms

With undertray is fitted: 7 tanks with a range of 6.04 to 6.58ltrs per 100 average of 6.25ltr per 100kms

The difference is .24ltr per 100kms, which as was demonstrated in the other thread would save about $58 on the average mileage.
I do about 600kms a week so if i multiply .24 by 6 (6x100kms) = 1.44ltrs saved.
At say $1.35ltr on average you would save 1.44ltr x $1.35= $1.94 per 600kms.
Multiply $1.94 by 42 weeks (to allow for holidays and sickies etc) = $81.48 per year.
Cost of tray in Victoria: $110 plus $16 for the "special" nuts that clip into the chassis = $126
Will pay for itself (for me and my mileage) in about 15months.

And just in case you are wondering, no overcooling or overheating issues, and it doesn't increase or reduce engine noise.

So there you have it!!!

In Focus · 27-10-2011, 11:44 PM

Good research. Well done.

Foobar · 28-10-2011, 08:32 AM

I believe this is an Econetic part - just wondering what it looks like exactly (photo?) cos I don't know if my WT LX TDCi has one or not and if not. You'd think it would but ...

paulo7 · 28-10-2011, 09:47 AM

Hi Foobar,

yes you probably have one, either open the bonnet and look down and you should not see the ground, or kneel down and look under and the car from the front and all you should see is black plastic instead of the bottom of the engine.

cheers

vhcbm · 28-10-2011, 01:03 PM

Yea WT has them. Nice find, but is the saving really worth the $130

Caydus · 28-10-2011, 01:29 PM

Well, it's a 3% drop in fuel consumption, which could be arguably in the margin of error.
It's more effective during the highway miles and less so in the city. Your mileage may vary...

However, it's probably good protection for the bottom of your car (especially if it's lowered) and would probably deflect stuff like big rocks that might catch on the bottom of your car and rip something vital out.
Thanks to the OP, it's shown that it seems to clip right on and generally has a positive effect on the car and doesn't seem to cause any drawbacks other than the price and time of installation.

If $126 + Installation isn't a huge deal to you, then why not?

Also, how does the undertray deal with water? Will stagnant water pool between the bottom of the car and the undertray?

Fiesta_Man69 · 28-10-2011, 01:50 PM

Beforehand you drove the car normally. You then spent $130 on an undertray in pursuit of saving fuel. Afterwards I have no doubt your driving attitude would have changed, whether intentionally or not, because you were consciously thinking about fuel economy far more than before. The fuel saving you experienced was due to a small difference in driving behaviour, not a $130 undertray.

I have recorded fuel figures as low as 5.2L/100km when I drove for fuel economy a few months ago on the way to work, just to see how low I could get it. I tried it for 2 weeks. Then I went back to how I normally drive, same route, same traffic, and the figure went up to 6.0L. No undertray, nothing else, just modulating the right foot.

The biggest fuel saving device is your right foot, and it costs nothing....

If this $130 part made a huge 0.2L fuel saving then Ford would have fitted it to all Fiestas from day one on the WS, as fuel efficiency is huge pulling power in this light car segment. The fact that it wasn't standard equipment speaks volumes.

The undertray was used on the econetic with low resistance tyres (tyres that worked surprisingly well but had half the grip mind you) and other aero aidsand a diesel engine designed for low fuel consumption. It was part of a package, not a stand alone part.

After the previous thread, I went to a Ford service department and they weren't keen on selling me the part if I was after fuel economy alone and not enhancing the 'looks' of the car, as they didn't believe it would do anything: and that's from a dealership. They also wanted a lot more than $130 too.

If people want to buy it to rice up their Fiestas that's fine: it just doesn't work to lower fuel use by any measurable margin. Not at our speed limits. Not in surburbia.

If you want to save fuel, change gear earlier: don't drive like a boofhead. There: $130 saved in a second.

But, if you believe the undertray alone does save 0.2L on a Fiesta in surburbia, I believe HDT are reintroducing the Polariser......

vhcbm · 28-10-2011, 02:02 PM

Quote:

Originally Posted by Fiesta_Man69

I believe HDT are reintroducing the Polariser......

Yes they are in their new update.

Fiesta_Man69 · 28-10-2011, 02:08 PM

I know. And it will work as effectively as the original polariser, or this undertray's fuel saving claims, or investing in those lovely Nigerian business 'opportunities'....

paulo7 · 28-10-2011, 02:31 PM

Yes,
you can say it doesn't make any real difference.
I purposely kept a record before and after with the express purpose of reducing the psychological effect of going lighter on the accelerator because I fitted an undertray.
That's why I've outlined the comparison of 7 tanks before and after. That's 7 weeks of driving to work on the same roads in various conditions of weather so as to even out the variations.
I still have receipts going further back and when you average them out it still comes to around 6.5ltr per 100.
I also think that the Econetic has a combination of fuel saving things that are designed to make that car stand out from the rest of the Fiesta range.
If the petrol version also got close to the same fuel economy because ford fitted the undertray and had the same ride height with the same tyres then there wouldn't be much incentive for a customer to buy an Econetic would there?
I'm going away for a trip to the country over the long weekend so I'm very interested to see what consistent highway speeds will show up in fuel economy with it.
cheers

paulo7 · 28-10-2011, 02:36 PM

P.S.
Caydus, the undertray has little vent holes along the front of it and a few drain holes in various places.
was an easy fit with the right 'nuts' that clip into the subframe. Then you just have to screw it in with phillips-head automotive screws that you can get anywhere.

mik · 04-11-2011, 11:36 PM

good onya Paulo7 for doing a bit of research, it does`nt surprise me that a bit of aerodynamics under the car can make a difference, some of the new models are coming out with shutters on the grille just to get a smooth airflow over the front of the car, every bit helps.

Fiesta_Man69 · 06-11-2011, 08:39 AM

Just curious: as people have noted, the undertray is now being used on the WT range. Now, people have claimed 0.2 fuel saving, yet the official fuel consumption of the 1.6 petrol WT is 6.1, identical to the WS. Now if the tray itself reduced consumption by 0.2, shouldn't the WTs official consumption be 5.9 vs the WSs 6.1?

Since it isn't, and these are Fords official figures, I'd consider it proof enough that the undertray by itself does not reduce fuel use as per some members claims.

In Focus · 06-11-2011, 10:36 AM

You could argue Ford wouldn't put them on if they didn't offer something. It would be a few dollars saved on every car (certainly less than $130 but maybe $20-30 including labour), and Ford wouldn't be the only manufacturer in trying to save money here and there by leaving something out. Spare tyres are a good example.

And we all know the official figures are only a way of directly comparing cars, but only vaguely represent "real world" figures.

My take is the undertray probably helps a little - it certainly wouldn't hurt. It might be that it's actually proven to be a method of avoiding oil filters being removed prematurely by uneven road surfaces etc, which I believe has happened to some WS's.

geelong festy · 18-03-2012, 08:20 PM

G'day paulo7! Your fuel economy figures are not dissimilar to to what I achieved. My fuel consumption figures are a little worse, but the economy improvent was slightly better. Some people I've spoken to have kept the little shin spoiler but I removed mine. The benefit has been best on long, fast drives and zero around town (as you'd expect). Their has been little or no noticeable difference in handling but the induction roar seems a little louder. I run cold air pipes from the fog light holes to the under side of the inlet manifold and ran a surface temp probe to make sure I didn't get too hot under he collar (so to speak).
I'd ignore all these armchair experts if I was you as they are fast to criticize but haven't haven't actually done anything themselves. I have long since taken any notice of their criticisms, and as you can see by my car, I put my money where my mouth is!! I paid $120 for the econetic under tray and a few bucks for the fitting kit. People can be as pedantic as they like, but for 120 bucks, it's only pocket money for the enjoyment and challenges of modifying your pride and joy! One idiot told me that I'm "better off just fitting a CAI". This person obviously misses the point! If you're an enthusiast like me, you fit both! Keep up the good work and if you want any feedback about what I've done, feel free to contact me as I don't make posts about all the things I've done, the racing and money I've spent on my fantastic little car. Keep experimenting mate, cheers, Geelong Festy.

Caydus · 19-03-2012, 03:09 PM

Hey Festy, prob a bit off topic, but could you elaborate on your 'cold air pipes'? possibly some pics?
Possibly more importantly, is it legal in NSW?

paulo7 · 19-03-2012, 10:13 PM

Wow Geelong Festy, I certainly didn't expect to get a reply from you, I thought you dropped a bombshell of an idea and sat back and watched the fun...!!!
Thanks for the compliments, and I agree with you, if you are a bit of an enthusiast, why not try something? I've had the undertray for over 7 months now I think, and yes, on long runs its made a small but significant difference to the fuel economy. Cheers!!