Accent coasts poorly, but why?
 

My 2008 Hyundai Accent coasts much more poorly in neutral (it's a manual) than any other car I've owned. I was hoping it would improve after being broken in, but it persists. I live in a mountainous area, so I coast in neutral a lot and sometimes for quite extended periods (I live right on a big ridge). I asked my mechanic but he had no real suggestions as to why the coasting performance is so poor. Anyone have any ideas? I doubt it's something I can do much about, but a man can dream... Thanks.

https://www.gassavers.org/gaslog/sig.php?id=2499

How about jacking up each wheel and spinning it- to check if any of the brakes are dragging.

You could try to make a belly pan to improve aero- is that rear bumper cover hollow underneath? If so, it could create a parachute effect if it is scooping up air all of the time.

Excellent practical suggestions! The rear bumper is indeed hollow and partially exposed to form somewhat of a scoop. Maybe some sheet metal to cover that up? But how to attach it. Have to think.

Need to wait on warmer weather to spin each wheel. Still a ton of snow here in VT!

I know my snow tires coast worse than my all-weathers, but even accounting for that it still coasts badly.

the tire pressure is at its max, right?

Yes, they are. My snow tires only have a max of 35, but the all weathers I run in the summer are more than that (the value escapes me at the moment). My previous vehicle (a Honda Accord) coasted significantly better even with winter tires inflated only to 32 psi. And it was a 1990 with 150,000 miles! Rust killed it in the end.

Google tells me the aerodynamic drag coefficient for that car is a respectable .31, so that's probably not the problem. At 2500 pounds it shouldn't be too light to coast reasonably with that drag coefficient.

Check the wheels for free spinning as mentioned above, not only looking for dragging brakes but also a bad wheel bearing.

Maybe there's lots of friction in the drivetrain? Thick fluid in the transmission and differential, or badly designed CV joints? That would seem to be a stretch.

I have been trying to figure out in general why the Accent's mpg is only 32. That's worse than the Aveo and the Yaris. I notice that the automatic transmission Accent is actually rated higher than the manual one for highway driving.

Use the lightest weight gear lube recommended.

regards
gary

Well that's cheap and easy to try. Cool.

Have a look at the handbrake (emergency brake) adjustment as well.
Sometimes they can not release fully and cause a significant amount of drag.
Easiest way is to put your finger on the hub or as close as you can get to it and feel if it is at all hot after a long coast.

Good luck , Pete.

These are the cars I've driven on the same hills I do now that coasted better:

2001 Hyundai Elantra - odd that another Hyundai coasted better
1990 Honda Accord
200? Mistsubishi Eclipse (friend's car I got to drive a few times when he visited)

The Accord was the best, then the Elantra, then the Eclipse. I think the main reason I notice is that I live on a big ridge right off a state highway and if you coast well enough you can go 3.4 miles before needing to use any power. It goes up and down a bit, so if your car doesn't coast well enough you can't make it. The Accord coasted so well that I needed to brake to keep the speed safe in the initial downhill stretch.

Most manuals sold in the US are geared more for performance than economy.

That makes a lot of sense. Thanks for the explanation as the discrepancy was hurting my brain!

Oh yeah, that's for sure. My VW runs 3000rpm at 70mph, but has plenty of torque for half the rpm. I'm in high gear at 25-30mph and grabbing for another gear but there isn't one.

Driving in the highest gear possible was one of the big habit changes I learned when I started looking into fuel efficient driving. Before that I always kept it between 2,000 and 2,500. It was how my mother taught me when I first learned.

i know its a different generation, but my '04 accent manual coasts wonderfully. maybe a dragging brake caliper?

I sure hope so. It's gotten pretty warm the last couple days (40s), so maybe I'll try and take a look. My mechanic's pretty cool, so he'd probably be willing to take a gander as well. I'll get back to you. I need to write down everyone's suggestions so I don't forget any.

Hey,

I too have a 2008 Accent and it coasts like crap over 80 km/h (50 Mph). Once below that it will go quite a long way.
It has to be aero, do they say at what speed the drag was calculated at?

I have a Focus ZXW and it coasts forever and a day.

A belly pan is a great idae, I'll see if I can't find one or get one made.

I am getting 38-40 MPG right now, yourself?

Eyeteaguy

Finally another data point! Is yours a manual? It's gotten cold here again, and I've been too wimpy to jack the car up in the snow to check things out. Take a gander at my gas log. It'll give you a better answer than I can.

i really dont pay much attention to the ratings. i know they're wrong for my accent, i get around 30mpg city and even up to 40 highway. more than enough for me;)

Yes, manual. Its cold here too and I am shocked at how much that affects the mileage. I've started getting into Pulse and Glide so my numbers are getting very good.

I spoke to my mechanic who put me onto his autobody guy. He seems to think any reduced aero will be negated by the added weight. He also says that it will affect the handling. I drive at 80km/hr? Its not an F1 car.

I'll let you know if it works out. There was a big crosswind today and it really killed my numbers so I am thinking that aero must be a big deal.

Eyeteaguy

Do you use winter tires?

We seem to be getting roughly comparable mpg figures. I'm not too willing to modify my car in non-reversible ways as I may wind up selling it. This limits the aero mods I can try out.

Adding a little weight doesn't have much effect on most cars, though an Accent could be sensitive to it. There's a link in my sig about it. Most people fail to improve their fuel economy by removing weight.

The amount of weight for aero mods is usually tiny and nobody would think it a problem. The proof is in the puddy; look at Basjoos car, which has loads of stuff added to the body for aerodynamics, certainly weighing a lot, and done on specifically a model that is known to be very sensitive to weight.

Aerodynamic improvement means more than weight for anyone who is even vaguely trying to drive efficiently. People for whom weight matters more are those who drive exceptionally wastefully, and those who drive 100% in awfully congested hurried city environments.

However, I wouldn't pay the body guy for aero mods. Professional body work is very expensive and aero mods tend to be experimental, taking a few tries to get an improvement and then not generally improving enough to pay off a professional body guy.

I've come down on the side of not removing the spare and jack from my Accent. I did take the drawbar for my hitch out though. Doesn't weigh much, but I never need it unexpectedly.

My mechanic, while skeptical of a lot of hypermiler stuff, thinks a body pan is worth looking into. He's a gruff, skeptical sort, and we enjoy talking.

those are the best kind to talk to sometimes, they can think of things very differently and will often come up with ideas you would never have on your own.

I don't know if this pertains to your issue, but my wife had an accent a few years ago and that thing did horrible with fuel economy compared to my civic. They were both 5 speed 1.5L, but the accent always got mid 30s, where my civic would usually get mid 40s. Maybe it is a hyundai thing that they want to keep your Mpgs low.

The Accent does seem to have worse economy than you'd expect. The 2008 Aveo has a 1.6L engine (same as the Accent), weighs slightly more, yet gets better fuel economy ratings. Gearing ratios? Aerodynamics? Cheap bearings? X factor?

Like the Hyundai Accent, the Aveo is Korean designed and built too, by Daewoo. The Aveo is pretty well known as a loser, at a price only slightly less than a larger and nicer Cobalt while getting worse fuel economy. (Though it has that reputation, I looked it up and the price difference is large.)

Fueleconomy.gov reports EPA ratings 24/34 for the Aveo vs. 27/32 for the Accent; that adds up to 27 combined for the Aveo vs. 29 combined for the Accent. Accent wins there. The only place the Aveo gets a better economy rating is on the highway.

So, let's have a look at some of the differences that might account for its better FE...
cD: .33 vs. Accent's .31 -- Accent wins. This is important for highway ratings.
Curb weight: Google reports various numbers for each, but the Aveo comes in slightly lighter...but not enough to explain a signfiicant FE difference. Doesn't matter for highway ratings anyway.
Gear ratios: I'm not finding definitive information, but they seem very close. The Aveo seems to have a taller 5th gear but the "final gear" (differential ratio) is shorter, and I'd guess it comes out even. I didn't figure in tire size, though.

I was expecting gear ratios to be the advantage. American manufacturers seem to put in taller highway gears than foreign, and I thought maybe GM insisted that Daewoo put in a tall 5th when building the Aveo.

How many RPM does the Accent run at 70mph (or 55mph or whatever)?

Checked my owner's manual and the gear ratios aren't listed. I'll determine what the top gear ratio is next time I'm out. Can't help with the automatic, of course.

Did a search of the garage and the only Aveo with a significant gaslog is averaging below the EPA combined estimate, so it's not much good as a point of comparison.

Did anyone mention alignment? A wheel might have been hit. If nothing else works, I'd take it to a shop and have all four wheels checked for toe-in.

Would an alignment issue I can't really notice effect coasting significantly?

I typed a long explanation about why there is a difference and it didn't post, so here is the gist of it.

The Aveo weighs 8% more so its city suffers. The Aveo 1.6L, however, makes peak torque 1100 rpm lower than the Accent 1.6L so the Aveo is more efficient on the freeway.(Peak efficiency is at the torque peak and on the freeway the engines hang closer to 3400 than they do 4500)

OK, just put on my summer tires and gave the wheels a spin while I was at it. The rear ones spin very freely, but the front ones resist. Of course I'm turning the half shafts when I spin 'em so I imagine it would resist somewhat. Way below a level I could use my torque wrench to measure. If I had to guess I'd say both fronts had about the same resistance. How much resistance is normal?

If you can't measure it with your torque wrench it isn't enough to worry about. I'd expect your front tires to have resistance because of the cv shafts, disc brakes, and differential up front.

Even though you aren't spinning the other tire you are still spinning everything after the planetary assembly within the transmission.

Went out to run some errands and the coasting, while still not as good as my other cars, is still a lot better with my summer tires. So that's something anyway.

While I was at it I got the engine RPMs vs speed. 60 mph @ 2950 RPMs. I took a digital picture of the tachometer rather than trying to stare intently at both gauges at the same time. This is with my summer tires on again, so the tire size is matched to the speedometer.

Hey, the gearing is quite poor. At 55 MPH it revs at 3,000. That is part of it. They geared it for city driving. Quick starts with a small engine.

I also did some testing 2 days ago. We had 40 km/hr winds and they were blowing right down the road I take. (it is normally a crosswind).

I did the same stretch of road at 60, 80, 100 and 120 km/hr(don't tell the cops)
It is aero for sure. The speed dropped very quickly from 120 and 100 down to 80 where it slowed. At 60 it never really dropped off at all even with a headwind.

The next day was calm and I did the same test. 120 and 100 the speed dropped off, but 80 and 60 the speed stayed constant.

If I coast starting at 40, the car seems to want to go forever.

I can only guess the hollow bumper is making a scoop and the faster you go, the smaller the bubble of air from the front is and the air is getting into the rear bumper.

And to clarify. The autobody guy was talking about wanted a sheet metal belly tray, quite heavy. I'm going to see him again next week and ask himif a plexi, or fierglass tray might be feasable.

What gauge metal was he suggesting?

The weight of it only matters when riding around town. I doubt even a 100# pan would cause issue.

maxi,

check out this idea by dracofelis...

https://www.gassavers.org/showthread....wheel+bearings

might help you a bit anyway.

the use of synthetics to decrease rolling resistance is not a novel idea.

Interesting thread, but they didn't seem to reach any particular conclusions. At first I questioned the quality of the bearings, but my mechanic told me that was unlikely it. He also told me that if I was getting greater than 40 mpg in the summer on these hills that I shouldn't waste any more time worrying about coasting!