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Posted by RallyEclipse98, Jun 13, 2011
420A Drivetrain Tech - Transmission, clutch, flywheel, driveshaft, gears, differentials, transfer case, shifter, etc - specific to 2G N/T DSMs.
Just shift at 2-3k. It's a high revving motor and is designed to be shifted around that range or a bit higher.
And what is "sport shift"? Is this the latest term among the kids?
Ever heard the the phrase, "to high of a gear"
It will work your transmission harder shifting to early which indeed will consume more gas!
If the commute is 60 miles a day, than idealy you would get best mileage staying around 55mph if its highway driving.
Post 25 is where I saw the term "sportshift."
This thread was the one that sparked my interest in short shifting to save fuel.
DSMnoobsauce...do you have any proof or credible sources to backup what you are saying regarding more fuel consumption with early shifts?
If you look into fuel maps for any car or just know how the engine operates you'll realize that you use more gas. The engine is trying to accelerate as fast as it can when you're at low rpm's with the pedal down, in order to accelerate at the same rate as say a lower gear at higher rpm's it needs to use more air/fuel to get going, thus using more gas.
That was me on post 24 of that thread, and the term is short shifting not sport shifting.
This thread has seriously conflicting information. I suggest the OP should Google ("short shifting" mileage) There are many references to using the technique to save fuel,both on the road and on the track.
I stand by my prior post on the subject.
How does the differential compression loading on the rod bearings between 3000 RPM and 6000 RPM compare to the differential inertial loading between 3000 RPM and 6000 RPM?
Please provide references.
I'm sure there's some scientific explanation, but the quickest way to explain it is by examples.
IE: you have 10 bags of cement to carry. if you carry 5 at a time, you're going to hurt yourself. but get it done in 2 trips. at the end of the day you accomplished your task but hurt yourself
or you carry it one bag at a time. you accomplish the same amount of work, but it takes you longer. at the end of the day you accomplished the same amount of work but didnt hurt yourself.
the way it relates to rod bearings is by amount of fuel burned per combustion stroke. if you bog the motor down it will see a high load value and dump x amount of fuel per stroke. lots of fuel=big boom=lots of load on bearings. AND if you're under 2k rpm then you're also not getting full lubrication, which = very very bad day for your bearings.
just look at a fuel map. at low rpm, high load x amount of fuel is injected. and at high rpm, low load same amount of fuel injected.
TLR- low rpm and bogging down = bad.
2K RPM in second gear is about 20 MPH in my Talon. Maybe I should.... Nah.
To the OP- here's the stock fuel map. higher number=less fuel=better mpg
You realize you're in a 420A forum, right?
That's the only fuel map I had, and I showed where the NA map ends
Fuel per pulse is relevant for tuning, but shifting changes the load and the RPM.
Less fuel per injector pulse would be a good thing if efficiency was measured in fuel /revolution. However; on the road or track distance/fuel is more important. Like for example, miles/gal.
Up shifting my Talon to second gear allows me to use only 57% as many fuel injector pulses/mile as in first gear. As long as fuel/pulse doesn't go up more than 57% the mileage will be improved.
Short shifting for fuel economy is an old well known technique to save gas. Like any rule of thumb it works best when staying on the ranch of reasonable. Don't shift from first to fourth at 10 MPH. If your car bucks and stalls you're overdoing it.
from what I have found on newer fuel injected cars with knock sensors is that if you are stalling the motor it is possible that you are damaging the motor however if the rpms are climbing then you are ok no matter the initial rpm's. I hope this helps a little. My advice to the OP is drive it one way for a tank and write down your MPG and then drive it a different way and see which one is better. Pretty technical hu?
@ OP: You are asking a question that hinges a lot of personal opinion. Research is probably needed on your part so you can form your own opinion... or you could decided not to care about saving an extra 4 bucks a month.
1st to 2nd: 2.5 - 3k
2nd to 3rd: 2.5 - 3k
3rd to 4th: 2 - 2.5k
4th to 5th: 2k
Cruising at 1.5k to 2k rpm, Autobahn with 3k-3.5k (70 to 80mph with cruise control)
After 25k miles of driving my car I always get about 28-30mpg including some high speed sessions on highways. The best I ever got were 37mpg with nearly a complete tank emptied on the highway (over 400miles of driving) I bet there is more potential for saving gas, but that are some solid numbers and I am happy with that.
But i just say you can generally i shift btwn 1.8k-2.5k when trying to save.
Man, in the future I may get an ultra-gauge because I'm nerdy like that.