Older cars coasts down hills noticeably faster?
 

Hey everyone . . I wasn't too sure where to post this so I apologize if this post is misplaced.

Anyway, I drive a 1994 Toyota Camry V6. After driving some newer cars, I noticed that when coasting, my Camry gains more speed going downhill.

For example, on a 1/8th mile downhill, My Camry would coast to about 40 mph whereas the newer cars I drove would only coast up to around 35 mph.

All of these cars are automatics, and by coast, I mean leaving the feet off all pedals with the car in D.

Does anyone know why my older car seems to gain more speed coasting downhill than newer ones? Thanks!

It could be that the Camry has longer gearing.
Or the engine gives less braking than the others.

For fuel efficiency, coasting down faster is good ;)

The older cars weigh more?

Longer gearing. And perhaps more freewheeling. Newer cars have the torque converter lock up in higher gears.

Hey, thanks for the replies everyone!

So I don't really understand engine breaking so I googled it. . first result said that engine breaking is mostly due to the vacuum, which is caused by the "butterfly valves" being partially closed when your foot is off the gas. So are my "butterfly valves" open too much or something?

Longer gearing may be possible, but considering that all of the newer cars I tried don't coast as fast, has a lower likelihood (but still possible). One of the new cars is an Accord, which appears to cruise at around the same, if not slightly lower, RPM as my 94 Camry at 50 MPH. Not sure how that relates to gearing.

Also, as far as weight is concerned, both heavier cars and a lighter car I tried both don't coast as fast downhill.

After driving it a lot, I noticed that my 94 Camry locks up the torque converted at around 45 MPH. I've got no idea where these newer cars lock up the torque converter. Perhaps the Camry doesn't provide engine breaking until 45 MPH and the newer cars are locking up and providing engine breaking at lower speeds?

Friction from newer tires is greater than tires with, experience. Also, I notice most dealers barely manage 90% max sidewall, while a car you own (I imagine) has at least max sidewall.

I would assume its due to differences in engine breaking. If you put both cars in neutral on the same hill assuming similar conditions, weight, drag coefficient and tire pressure they should coast about the same.

For Example: My Elantra when I lift off the pedal will cut fuel to the engine and starts to engine break in gear to keep the motor spinning. This I assume is to save fuel when slowing down. My truck on the other hand will drop its rpm and the engine keeps running normally, burning fuel. The drag on the Elantra is very much bigger than in the truck. Going down a hill the truck will coast much faster than the Elantra in gear. If I put them both in neutral the Elantra coasts forever and the truck will slow down slightly less quick.

All this tells me is that the older cars ECU is telling it to do something different than the newer car which is causing it to coast down hill better.

Newer cars lock up at lower speeds, in more gears. I've felt some lock up in first gear at just 2k rpm, and then hold that lock in top gear until you decelerate to 1.5k rpm.

It's not universal, though.

I second the notion of testing freewheeling in neutral.

@UltArc: I assume you mean sidewall pressure? Yes, I'm actually a little bit overinflated. . I've heard that reduces rolling resistance. But certainly not enough to have a 5 mph differential at the bottom of a short hill? btw: great FE on that Mustang. Seriously, fast AND fuel efficient!

@night9: This seems to me that when our older cars (my Cam and your truck) coast in drive, it is very similar to coasting in neutral. . the torque converter is so disconnected from the transmission that the engine is practically idling downhill?

Whereas a newer car coasting in drive will stay in gear, maybe lock the torque converter, cut fuel off, and use the momentum of the vehicle to keep the engine moving? When coasting downhill in the Elantra does the RPM creep up with the speed?

I would venture to say deceleration fuel cut off is more aggressive in the newer cars compared to 1994. My Corolla almost feels like a manual transmission because of its DFCO at certain speeds and when going downhill.