higher gearing vs torque converter losses - Fuel Economy, Hypermiling, EcoModding News and Forum

escymkii · 09-22-2016, 10:53 PM

I was wondering if its beneficial to be in a higher gear in an automatic but have losses in the torque converter? I remember I had an astra before tho i did not experimented it properly i remember that if i activated snow mode which enables it to start at 2nd gear the FE reading in my UG drops significantly. Now i have a nissan maxima (no obd port so no UG to be installed) which loves to be in 3rd gear is this intentional by nissan engineers to save fuel? I tend to manualy downshift to 2nd to have a more direct power from the engine thinking that 3rd gear will have losses in the torque converter. Is my assumption correct?

jamiec · 09-22-2016, 11:12 PM

Does your Nissan have a lockup torque converter?

MetroMPG · 09-23-2016, 10:30 AM

I'm going to wager: highest gear is best. I wouldn't drive in 2nd even if you have no lock-up in any gear.

me and my metro · 09-24-2016, 12:37 AM

Figure out what rpm your torque converter stalls at and stay above that rpm for minimum loss. Most converters stall around 2000 rpm, you can check by revving it in low gear. See how high the engine will rev in gear before it spins the tires. Don't do this for very long you are making heat very quickly.

escymkii · 09-25-2016, 03:59 AM

Torque converter lockup is only on the highest gear. Stall is around 2000rpm. So would it be beneficial to activate snow mode so that it starts in 2md gear?

Daschicken · 09-25-2016, 04:49 PM

I had a 2001 Nissan Maxima 4 speed auto that made me ask this same question. When the car was warmed up, it would be in 4th gear in the neighborhood (25mph). I usually turned off OD to keep it in 3rd instead, but I think it actually got better gas mileage in 4th at that speed. I think it hung around 1100-1200 rpm in 4th maintaining speed, while 3rd was 1200-1300. That seemed backwards to me because 4th fully locked at 25 mph would be about 700 rpm, so that's a lot of slip.

I kind of miss that car. I miss its amazing throttle response, decent low end torque, and its interior. But I definitely DON'T miss that craptastic 4 speed auto. I looked at my fuelly back when I had the car, 22 mpg. I wasn't as good at hypermiling back then, and I didn't have my long highway commute, but that is still pretty bad.

escymkii · 09-26-2016, 05:59 AM

I agree. well here its the crapier engine (VQ20de) and a slightly different appearance (called the cefiro). The transmission I think for its time is nice (smooth) but makes driving experience like ****. Mine also has 2 way seats at the back and a massager at the back. Very cool for a cheap car.

Well back to the topic

@me and my metro : you mentioned staying higher than the stall well everytime my car sticks to 3rd gear annoyingly it will be lower than the stall rpm(1,800) Giving it gas will eventually downshift it to 2nd

me and my metro · 09-26-2016, 01:25 PM

If your normal driving speed is below stall in any particular gear your converter will be making heat by slipping. The question is can the car handle the tranny heat. The highest vacuum gage reading usually gives the best mileage. Sometimes you are in the converter and this is ok if you can float along. The next higher gear will just slip the converter more without lockup.

cosmick · 09-27-2016, 10:44 AM

I once had a 78 Camaro 305, TH350 with 1200-stall, 2.41:1 axle. All stock. First mod was a 3.08:1 axle, second was a tach, third was a B&M TorkMaster 2000 torque converter.
With the stock converter, cruising on the interstate, lifting off the gas resulted in the RPM dropping by 200 RPM. The launch from a dead stop flashed the converter to 1200.
After the converter swap, launch inproved to 1700, and felt better. But the interesting part was when cruising, lifting off dropped the revs by only 50. So the thing was more efficient.
A better launch with more mpg, it paid for itself at some point, while making the car more fun to drive and easier to live with.
Gearing to cruise at stall RPM is good, and use an ATF cooler, but consider a tighter converter also. Any of the big names can tighten up any stock converter, no matter who made it. Its all the same. Put it on a lathe, cut the factory weld holding the 2 halves together, open it up, clean it, tweak the fin angles, clean it again, weld it back together, re-balance it, paint it, ship it back to the customer.

escymkii · 09-28-2016, 11:44 PM

well one of the problems here is that you cant cruise on normal drives because traffic is horrible and there are lot of speed bumps for i think every 1/4 km or less.

I was also thinking if for example i find a way to place it on a higher gear would it be more efficient (will have a trans cooler if ever).