The AX Eco Project : 100 mpg target !

[HypermilerAX]

It's located on the bottom right behind the light. The air that goes in is around outside temperature.

What is the principle of the economy ? Higher intake temp = higher load ?

[renault_megane_dci]

The principle of any internal combustion engine is to heat air for it to expand and push down the piston.
For the air to heat up you put an amount of fuel wich held a fixed amount of burning power. The hotter the air you want to heat up, the least burning power you need.
Of course you need the oxygen so air needs to be dense so not too hot.

Writing it simpler : hotter air improves the thermodynamic efficiency of the engine to a point (after that you are out of range of the fuel pump metering ability then in engine failure land)

You need your inlet air to be in the 20°C to 40°C at the air filter mouth after that it is out of the tuning range setup by the car maker.

This is much less a failure issue on a diesel engine, gasoline engine are to be tuned with caution in this department.

[Piwoslaw]

A warm air intake is good for FE in a gasser (warmer air -> lower density -> less air in cylinder volume -> less fuel at given A/F ratio), at the cost of reduced performance.

Diesels like to be fed cold air, both for performance and FE.

[renault_megane_dci]

Piwoslaw, I have a lot of respect of your achievements and I assume they are based on technological readings of various reliable sources BUT how come my all time best fuel consumption with my diesel car are all done in summer on tanks where I tend to drive on the fast / non FE side (83 mph on the speedo or city traffic and A/C most of the time) - (more complaining time from the kids or more fuel, not one second hesitation !)

I red (here http://biblio.uqar.qc.ca/archives/24791721.pdf, page 92) that efficiency drops with temperature increase but it is because they wanted a specific RPM and power output.
But we are ecomodding overly powerful engines so anything that drops down power hence fuel is interesting. By using less dense air, my ECU puts less fuel in the given capacity cylinders, I artificially downsize my engine.

Now that I think about it, this trick is not applicable to mechanical pump engines ... sorry HypermillerAX !

[AndrzejM]

Originally Posted by renault_megane_dci

Now that I think about it, this trick is not applicable to mechanical pump engines ... sorry HypermillerAX !

But you can mess a bit with fuel dosing and achieve similar effect.

Anyway this discussion is interesting so I think I'll try to do ABA test with CAI vs WAI in Berta. If WAI will be better I'll think of getting rid of IC I don't ming loosing some power at high rpms anyway

[renault_megane_dci]

I wouldn't remove my IC.
First, I think you can have both side of the coin with a controlled grill.

Second and most important, from some temperature, WAI is detrimental to FE & can ruin your engine (on a diesel throught HG failure).

[HypermilerAX]

Nevermind then…

I have successfully passed the technical inspection. I’ll now be able to concentrate more on my mods.

I have tested the maximum size of tire I could mount. I put on a 155/80 R14 junk tire which is 10,3% bigger. When I steered to the maximum, there were just a few millimeters free between the tire and the inside of the wheel well. But the rims I will mount have a bit more offset, which will put them more outside. On the pics, the car is not on level, that's why it's so high.

I have redone the graph with more realistic figures of consumption gain based on the Lupo 3L official curves. The ratio (FE gain/gear ratio gain) is 0,55 from 3rd to 4th and 0,58 from 4th to 5th. I’ve considered 0,55 vs 0,75 before. This change give less advantage to big tires. In red, the tires that won’t fit. I also added, just to compare, a 185/60 R15 tire rated A which comes out as best. But to mount them, I need new rims and new brake discs for hole spacing, so that’s not worth it.
Conclusion : I’ll give a chance to the Ecocontacts 175/70 R14 (I want the biggest RPM reduction). They are available in extra load which, I think, is good for rolling resistance (max. pressure is 3,5 bar vs 3 for normal version).

Edit: and I have also filled all my fillup data.
http://ecomodder.com/forum/em-fuel-l...vehicleid=6831

[HypermilerAX]

I’ve received the tires and did the mounting myself. It was actually much easier than I expected, I managed to seat the beads with a hand pump. Original rim/tire combo weighed in at 10,6 kg. New setup is at 13,1 kg which makes 5 kg more rotational mass. I’m not too concerned by that since 95% of my commuting is at constant highway speed. I did a quick round trip around the neighborhood to test it. Only problem, the tire is touching the edge of the front bumper when I steer. That’s a matter of millimeters, I’ll see if I can slightly move it forward, if I can’t I’ll remove some matter (it’s plastic). Else, no problem with the suspension and full steering. First impression is much worse accelerations (mainly due to the ratios, not that much because of the weight). Steering feels still OK despite the width.
Each gear will have a 10% higher ratio, 5th gear tops at 39,8 vs 36,2 km/h at 1000 rpm. At 80 km/h, RPM drops from 2208 to 2011 RPM.
My speedo will actually be exact because I had a strange 10% overestimation with the originals tires. The distance will be underestimated by 10%. Not really a problem, as long as I consider it for consumption and maintenance intervals.
It didn't take me long to get other's attention. I passed by a car part shop with 2 people at the entrance and they stared at my front wheels (like "What the hell are these tires on that tiny car ?"). They still looked at the car when I was 200 m away. Their faces were so funny.
No pictures yet, but it's true that the tires seem gigantic compared to the car.

Originally Posted by Arragonis

Do you have more fuel fillups ? I'd be interested to see how winter is affecting you.

need to update mine too...

We have had low temperatures lately (0/8°C) and that’s noticeable on my consumption. I have a hard time getting under 3l despite the grill block.

[renault_megane_dci]

I would believe the wider the tire, the higher the rolling resistance AND drag penalty.

I hope for you the added gear reduction and better eco-rating can make up for those penalties (but I wouldn't bet on it).

I would think the tire eco-rating is within its size, not from best to worth.
Otherwise people with big fancy wheel could want some old school 2cv skinny tires ...

[Jyden]

Impressive mpg with that car.
How about rear squirts for even better mpg?