Mazda Demio aero ideas and testing

[Furai]

Probably not the most common car here but a great little daily, thought Id start a thread to share ideas and run over areas on this specific vehicle and improvements from you guys.

This is a daily driver and often gets betwen 30-34MPG or the most common number during a tank is 35L to 430-440km.
The main goal with this vehicle is to reduce drag and any increase in downforce is a bonus as it sees the track every so often.

Its certainly not optimised for fuel economy running sticky AD08R Yokohama tyres, has a camshaft and is generally driven more enthusiastically but it seems to fit in here moreso than on the race forums.

So here are the items done so far
Vehicle lowered, increased rake 5mm for handling purposes - average of 5km less per tank(Negligible difference)
Front tyre deflectors - average of 10-15km more per tank (Ill take that as a win to balance the rake)
Rear spoiler, Tried adjusting angle up or down but have seen no difference in economy or any other areas

Blocked half of front upper and lower grill(Only has half size radiator and air con rad is gone so nothing there) - Untested

Things Id like to do
Full undertray(Have to wait until new exhaust setup is complete)
Front air curtains(Wondering if these can be angled upwards to aid in downforce and tyre wake reduction?)
Possibly rear wheel deflectors? Not sure if worth the effort.

Im trying to get the most from the little 1300cc motor without resorting to power mods, mainly for fun.
Any ideas would be much appreciated and feedback.

Attached some photo's of the car and some of the mods

[Autobahnschleicher]

Interesting projecect.
My car is also a built for fun+economy, however I'm surprised you get a significantly worse fuel economy than I do with a significantly smaller engine.
I would suggest looking at your driving style and running higher pressures for normal driving than on the track.
I'm running Toyo Proxxes T1R tires on my car at the moment.
For road use I go with 3,0 bar front and 3,5 bar rear to reduce rolling resistance.
For fun use, I'll drop pressures to 1,8 and 2,0 bar.

[alexshock]

Nice wheels!

[Furai]

Originally Posted by Autobahnschleicher

Interesting projecect.
My car is also a built for fun+economy, however I'm surprised you get a significantly worse fuel economy than I do with a significantly smaller engine.
I would suggest looking at your driving style and running higher pressures for normal driving than on the track.
I'm running Toyo Proxxes T1R tires on my car at the moment.
For road use I go with 3,0 bar front and 3,5 bar rear to reduce rolling resistance.
For fun use, I'll drop pressures to 1,8 and 2,0 bar.

I suspect its due mostly to driving as its a fair amount of city, gearing means it does 3000rpm at 60MPH/100Kmh and the Cam is running with the factory ECU so doesnt fuel correctly(Would benefit from extra compression too)

I have tried some different pressures and normally run 38psi but it didnt make any noticeable difference, I used T1Rs a long time ago but if you tried the AD08R youd never go back!

Originally Posted by alexshock

Nice wheels!

Cheers man! TE37s one side and Watanabes the other

[oldtamiyaphile]

Originally Posted by Furai

Vehicle lowered, increased rake 5mm for handling purposes - average of 5km less per tank(Negligible difference)

Rake and lowering both should improve economy, you're probably driving harder now.

My 2.0 VTS gets the same economy and I mostly drive the wheels off it so you must be giving that rev limiter a proper work out

[maanma]

I think rear window wind guide should be bent smoothly downwards. Perhaps more diffuser guides could give improvement too.

[freebeard]

Cheers man! TE37s one side and Watanabes the other

Which are on the port side? Watanabe? I've ID'ed those as Minilite mags but they have thicker spokes.

maanma -- It looks to me like the line is continuous through the black endplates and then has a ~3" wickerbill.

[Furai]

Originally Posted by maanma

I think rear window wind guide should be bent smoothly downwards. Perhaps more diffuser guides could give improvement too.

I does touch onto the roof and I tried it bending slightly down, flat or up with no real difference. I could modify it for more angle up or down but I think it would start hurting at that point.

Originally Posted by oldtamiyaphile

Rake and lowering both should improve economy, you're probably driving harder now.

My 2.0 VTS gets the same economy and I mostly drive the wheels off it so you must be giving that rev limiter a proper work out

I swapped wheels and tyres when I lowered so no gains there(Went from skinny eco tyres to fat little chonky ones). Its about 70-80% round town so small gains to be had from aero with greater effect on the track but I should put my ECU in as the camshaft means it runs super rich at idle and I probably do drive too enthusiastically haha

[Furai]

Originally Posted by freebeard

Which are on the port side? Watanabe? I've ID'ed those as Minilite mags but they have thicker spokes.

maanma -- It looks to me like the line is continuous through the black endplates and then has a ~3" wickerbill.

Poor quality photo but this is drivers side, yeah it extends outwards but I think just having a small sharp separation edge might have been better. Factory spoiler has gap to channel air onto rear window hence why i cut it up to make this one.

[Autobahnschleicher]

Originally Posted by Furai

I suspect its due mostly to driving as its a fair amount of city, gearing means it does 3000rpm at 60MPH/100Kmh and the Cam is running with the factory ECU so doesnt fuel correctly(Would benefit from extra compression too)

I have tried some different pressures and normally run 38psi but it didnt make any noticeable difference, I used T1Rs a long time ago but if you tried the AD08R youd never go back!

Yea, my car is geared about the same, just with a larger engine.
My engine is also still running only 10:1 compression ratio, wich is kind of low.
Will probably try different tires at some point, but let's say my tires have quite a lot of life left in them still.
Also not sure if I can get them in the sizes I need, wich is either 185/55R15 and 205/50R15 and the alternative size was 195/50R15 and 215/45R15 if I remember correctly.