shifting a Manumatic

[ever_green]

I have 09 impreza 2.5i that's got a modified shortblock. the mods are in the signature but the main thing is that the car makes its peak torque at 4000rpm vs 4500rpm now (on the dyno). Even though the peak torque has dropped, both top end and low end power have been improved so the torque curve is much flatter now. ie. 95% of torque is made at ~2000rpm. For the stock engine subaru BSFC graph claims a sweetspot of 1500-4000rpm at 80-90% load. i think 4000rpm bsfc is no longer the case since my high lift cams engage as early as 1500rpm and car runs rich above 3000rpm now(depending on load). so i have been using the sport shift when in economy mode to improve MPG. i used to be shifting at 3000rpm & allowing the TC to fully unlcok at 80% load. but mileage did not improve, at least around town. so i decided to shift at 2000rpm instead and 60% load. but the torque converter makes this a pain in the butt. with +60% engine load the RPMs jump past 2000rpm as TC unlocks, even when im in overdrive at 25mph! unless i back off the throttle and drive slowly i cannot shift at or below 2000rpm.

just wondering what people's experiences are in shifting an automatic in order to improve fuel economy? drive slowly and let the torque converter slip to shift at low rpms or just let it fully unlock and shift at higher rpms?

[nbleak21]

I accelerate quick (80%) to 2500rpms in first, let off to shift into second, and repeat to third where I either lug around there in TCLU or repeat and lug 4th TCLU depending on in-town speeds in my CR-V (No manumatic, but TCLU in 3rd & 4th is nice!)

[GRU]

I haven't done much testing on different ways to accelerate but i swear i get the best results from accelerating quickly...if i accelerate slowly i'm getting (about) 10 mpg (depending on the exact speed) so it if takes me 30 seconds to get to 50mph, i'm better off to get 7 mpg and get there in 15 seconds

[ever_green]

Originally Posted by GRU

I haven't done much testing on different ways to accelerate but i swear i get the best results from accelerating quickly...if i accelerate slowly i'm getting (about) 10 mpg (depending on the exact speed) so it if takes me 30 seconds to get to 50mph, i'm better off to get 7 mpg and get there in 15 seconds

ok so youre suggesting unlocked TC shifts at 2200rpm vs locked 1500rpm at low loads. what if i leave it in D then and let it shift at 3000rpm at 80% load? that would make my life easier too. will that extra 800rpm cost me considerable MPG?

[GRU]

My opinion is 800 rpm will not make much difference...you will probably get better results shifting at 2500 rpm vs. 3500 rpm but i believe it's not much, the best results are from conserving momentum (avoiding stoping) and coasting in neutral