Realistic max MPG for a 1390cc Volkswagen Polo

[AndrzejM]

Originally Posted by Bataleon

True. That's a pity! What if I removed the serpentine belt completely and replaced the battery with a deep cycle battery?

I jacked up my car during lunch and tried spinning the wheels to see if there was any brake drag. The two front wheels are very stiff and only travel about 1/5 of a turn, even with a good push (the car gear was in neutral).

The back wheels are slightly better, although the back left wheel spins freely and then suddenly slows down, almost as if the brake pad is rubbing at a certain point.

How freely should the front and back wheels spin? Is brake drag easy to adjust?

I was off for few days so I couldn't check how it's with my Polo. I'll do that and post the results soon.

Removing alternator is a good thing for FE, but I'm driving my cars mostly on a long distances - for shorter trips I'm using my bicycle. So that's not for me.

But first your car has to be in a sound condition. That thing what you wrote about your rear wheel can give you an extra 1+l/100km or even more. You should check that. Definitely.

[renault_megane_dci]

Brakes are designed to be pushed back in position after braking through rubbing (against the disk or in the drum.
So it's somehow normal that it rubs a little.
Some cars fare better in this department than others.


Fellow ecomodders incorporate a spring from a bicycle brake to help pushing it back without the rubbing.

It does depend on your brake setup though.

You have probably rear drums.

The least good practice is to dismantle the caliper, clean it up (no reason to open the brake circuit) and make sure the caliper slides easily (assuming it is a single piston setup as is often the case, it has a sliding counterpart)

For drums it's a little trickier.
They do get clogged up so can be cleaned but they also usually have a freeplay suppression setup that does the exact opposite of what you do want (as a non braking ecomodder enthusiast) and I wouldn't tell you they're easy to remove ...

Thing you can do also is clean up the side of the disks with a file because they usually rust where a step is formed from the braking.

[Bataleon]

Originally Posted by AndrzejM

I was off for few days so I couldn't check how it's with my Polo. I'll do that and post the results soon.

Removing alternator is a good thing for FE, but I'm driving my cars mostly on a long distances - for shorter trips I'm using my bicycle. So that's not for me.

But first your car has to be in a sound condition. That thing what you wrote about your rear wheel can give you an extra 1+l/100km or even more. You should check that. Definitely.

My Polo was serviced last week (synthetic oil + filter change, brake fluid change, timing/cam belt changed) so things are running a bit smoother.

I still don't understand how you (and other ecomodders here) manage to get such amazing fuel economy. I drove 3.5km (half downhill) with a warm engine and my consumption was 7.7l per 100km. That was with me coasting in-gear and out of gear where I could, depending on how I needed to control my speed.

Do you think EOC would help? Or am I losing efficiency somewhere else?

Originally Posted by renault_megane_dci

The least good practice is to dismantle the caliper, clean it up (no reason to open the brake circuit) and make sure the caliper slides easily (assuming it is a single piston setup as is often the case, it has a sliding counterpart)

For drums it's a little trickier.
They do get clogged up so can be cleaned but they also usually have a freeplay suppression setup that does the exact opposite of what you do want (as a non braking ecomodder enthusiast) and I wouldn't tell you they're easy to remove ...

Thing you can do also is clean up the side of the disks with a file because they usually rust where a step is formed from the braking.

Awesome, thanks for the tips. I had my brakes checked and cleaned during last week's service so hopefully the drag has been reduced. I'll jack up the car later today and see how freely they spin.

[AndrzejM]

I don't want you to feel bad but on my way to Prague, where I'm at this moment I got FE of 3.39l/100km in my Polo. Lots of EOC though...

I've checked my wheels yesterday. And front wheels spins for around 1 full turn with a push from a hand. Gearbox in neutral of course. Rear wheels made 3-3.5 turns in the same conditions. So definitely you should check your brakes for drag.

[Bataleon]

I don't know how you do it What was your average speed? Do you EOC only downhill or on flat ground too? I need to install a kill/start switch for sure.

I jacked my Polo up yesterday and even though the brakes were cleaned during the service last week, there is still noticeable brake drag.

Do you think it's safe to install grill blocks in the areas pained red in the image? Outside ambient temperature is around 20 degrees Celsius.

[AndrzejM]

My average speed from MPguino was 65km/h on the whole route. Through many cities with speed limit of 50km/h Ususlly I'm speeding up to 95km/h killing the engine and gliding to 80km/h then bump starting the engine and do another pulse.

My upper grill is completely blocked, the lower one has an opening with dimensions of ~10x25cm. Temps were around +30 degrees Celsius and that was fine no need for fan to turn on. You have to test your grill with a pieces of cardborad and you'll find the best ratio between closing and opening the air flow.

But first get rid of that brake drag! That's the reason for your poor FE IMHO.

[Bataleon]

Very impressive! I averaged 6.2l per 100km today so getting better. Do you have a kill switch and a start switch? Or do you just bump start?

Does the grill block need to go in front of the grill or can it go behind? (like this: IMG_1071.jpg Photo by viio | Photobucket) I'll try and fix my back brakes but I don't think adjusting these drum brakes is easy.

Cheers

[AndrzejM]

I have a kill/start switch as described in my Polo thread. But I'm bump starting the engine for most of the time.

Grill block, better flow you can have with the block in front of the grill, but it doesn't make a huge difference. I would say you won't notice a difference.

Drum brakes are quite easy to maintain. You can find many tutorials on the web or youtube videos.

[Bataleon]

I must install a kill switch because turning off my ignition disconnects my OBD2 adaptor. The power steering and brakes also seem to stop working as well.

The grill block inside seems easier so I will do that first. I've watched a few videos about drum brake adjustments but it doesn't look like the Polo brakes are very adjustable. Would you recommend I replace all the springs so they pull the brake shoes in better?

Lastly, how easily do your front wheels spin?

[AndrzejM]

Yes kill switch is the must. You can find "how to" in my Polo's modding thread.

Brakes. First of all you have to check what's the reason for drag. It doesn't have to be adjustment problem. Rust, drum that is old and with extensive wear, brake shoes that are out of specs, too tight setup of the hand brake lines, etc.

Many things to check. So I can't tell what would help in your situation. You just need to check everything, and see on your own the results.