Transmission/gearing question

[Frank Lee]

I have never been rear-ended.

[EcoCivic]

Originally Posted by Frank Lee

I have never been rear-ended.

Then I am glad you live in an area where people drive in a civilized manner unlike Memphis. The speed limit on one of the highways around here is 70 MPH, and a lot of people go 90 or more.

Also, the other factor here is that the left lane is often much more nicely paved than the right lanes. The right lanes are generally quite rough with a lot of pot holes, lumps, and harsh transitions that rattle my insides out and frequently scrape my car.

[EcoCivic]

Well I have an update. My transmission went out after 243K, so I installed that JDM SLXA transmission that's been sitting around for the last 3 years. This transmission is geared shorter than the OEM trans was since it's from a Honda Stream (heavy station wagon), which I like. The car feels somewhat quicker since the gearing is shorter, but that also means my cruising RPM has increased.

My RPM going 60 has increased from around 2300 to around 2900, but I need to verify that the torque converter is locking because that seems high to me. I have been getting about 33 MPG average lately with the old trans. I will report back shortly with how my MPG changed.

EDIT: I was concerned that I might not like the way the car feels or sounds cruising at a higher RPM, but at least up to 70 MPH (which is the fastest I have gone so far), it feels fine. If anything, the engine actually sounds quieter oddly enough. It's possible that maybe the actual decibels aren't lower, but the frequency is higher and is IMO more tolerable. The noise before was more of a deep roaring, but now it is kind of a higher pitch humming, which is less disruptive when trying to have a conversation IMO.

Also, unsurprisingly, I noticed that the car takes less throttle input to maintain speed on the highway, and it doesn't seem to have as much difficulty climbing hills in 4th gear. It didn't really feel like it lacked power climbing hills with the old trans, but I barely notice when I get to a small hill with this trans when I am cruising down the highway.

[litesong]

Originally Posted by EcoCivic

Well I have an update. My transmission went out after 243K, so I installed that JDM SLXA transmission that's been sitting around for the last 3 years. This transmission is geared shorter than the OEM trans.... My RPM going 60 has increased from around 2300 to around 2900.....

My 2008 manual Hyundai Accent had 2980rpms at 60MPH. Wanted a higher geared transmission, but settled for used, but bigger wheels/tires. Over 3 years ago, I went from 175x70x14 inch wheels/tires to 195x65x15 inch wheels/tires. Eventually, I moved up again, to 205x65x15 inch tires(nice fit in wheel wells, but close to mudflaps), with rpms reduced to 2730 at 60MPH. Very happy with my decision, specially for the dirt cheap, but well performing tires I've gotten. Big bumps to the Accent are swallowed much better with the big tires, handling is much better & the Accent belongs on the highway, now. Last summer, eighteen tanks in a row were over 40MPG with highs of 45, 47+, & 48+MPG. Never had over 45MPG, previously. Have a second car that got the big tire treatment & that car is sweeter to drive, also.

[litesong]

Originally Posted by Frank Lee

I have never been rear-ended.

So your buns are still cute?

[litesong]

Originally Posted by mpg_numbers_guy

The manual transmission will provide better fuel economy around town, but the automatic will likely get better fuel economy on the highway, due to its taller gearing......

Not necessarily. We have both a 2013 automatic Elantra AND a 6% lower geared 2016 manual Elantra (same series). Both are rated the same EPA highway mileage. As a featherfooter tho, I try to keep speeds down, & would say the manual gets slightly better MPG on highways. On back roads with both transmissions in high gear, the manual gets somewhat better MPG. Of course, going over mountain passes, the manual gets about 6% better MPG. With its lower gearing, the manual has much better acceleration & speed holding ability on mountain slopes.

[EcoCivic]

Originally Posted by litesong

Not necessarily. We have both a 2013 automatic Elantra AND a 6% lower geared 2016 manual Elantra (same series). Both are rated the same EPA highway mileage. As a featherfooter tho, I try to keep speeds down, & would say the manual gets slightly better MPG on highways. On back roads with both transmissions in high gear, the manual gets somewhat better MPG. Of course, going over mountain passes, the manual gets about 6% better MPG. With its lower gearing, the manual has much better acceleration & speed holding ability on mountain slopes.

Good to know, thank you for the information! I suspect that the manual transmission gets better highway MPG because it is more mechanically efficient than the auto since it has less moving parts and no internal oil pump.

[litesong]

Originally Posted by EcoCivic

Good to know, thank you for the information! I suspect that the manual transmission gets better highway MPG because it is more mechanically efficient than the auto since it has less moving parts and no internal oil pump.

You're probably barking up the right tree. The manual 2016 seems more powerful, & NOT just because its geared lower. The 2016 Elantra has 2 or 3 HP LESS than the 2013 Elantra. However, the 2016 engine seems smoother & more responsive than the 2013. I do love the 2016 manual in the mountains to 4000 feet. Soon, I'm going up to Mt. Rainier & Chinook Pass (5500 feet). Expect the manual to continue its mountain superiority over the 2013.
Both Elantras have a total of 135,000+ miles, & nothing has ever had to be repaired on either one.

[EcoCivic]

Originally Posted by litesong

You're probably barking up the right tree. The manual 2016 seems more powerful, & NOT just because its geared lower. The 2016 Elantra has 2 or 3 HP LESS than the 2013 Elantra. However, the 2016 engine seems smoother & more responsive than the 2013. I do love the 2016 manual in the mountains to 4000 feet. Soon, I'm going up to Mt. Rainier & Chinook Pass (5500 feet). Expect the manual to continue its mountain superiority over the 2013.
Both Elantras have a total of 135,000+ miles, & nothing has ever had to be repaired on either one.

Good to know, thanks for sharing. One possible explanation for why the manual trans may feel faster is because it has no torque converter. The energy wasted by the torque converter never makes it to the wheels. Assuming that the torque converter is 90% efficient at full throttle, it could be wasting up to 15 horsepower on a 150 horsepower engine that could be going to the wheels, which certainly would be noticeable.

That and a manual trans is a lot lighter than an auto and likely has less rotational mass since a clutch is probably a lot lighter than a torque converter.

Here is a thread I made about manually controlling my torque converter lockup if you want to check it out. https://ecomodder.com/forum/showthre...-new-post.html

[litesong]

Originally Posted by litesong

Over 3 years ago, I went from 175x70x14 inch wheels/tires to 195x65x15 inch wheels/tires. Eventually, I moved up again, to 205x65x15 inch tires..... Big bumps to the Accent are swallowed much better with the big tires..... & the Accent belongs on the highway, now.

The road that shows the most benefits from the larger tires, is the Highway 2 west bound trestle as it approaches Everett, WA from the East. Within the last year & a half, it was repaved with very smooth & quiet pavement. However, the joints on the trestle are wide & they didn't pave close enough to the joints. With our larger car, which doesn't have the large tire treatment like our smaller car, the trestle tire thumping is disconcerting. The smaller lighter Accent, with tires that are 6/10's of an inch GREATER in diameter, than on the larger car, has a nicer(less thumping) time on the trestle.