Fuelly Forums - Full Throttle at low RPM, or High RPM and low throttle

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Quote:

Originally Posted by fowljesse (Post 149969)

So, in the simplest terms, are you saying that it's generally most efficient to stay at about 75% throttle, shifting early, until @ cruising speed?

That has worked best for me. Any time I try to use lighter throttle it ends up being less efficient.

Quote:

Originally Posted by theholycow (Post 149979)

That has worked best for me. Any time I try to use lighter throttle it ends up being less efficient.

how do you know what throttle percentage you're using exactly, scan gauge?

cow is that possibly only specific to your car?

Quote:

Originally Posted by BEEF (Post 149614)

I knew quite a few people that had 300k+ on subarus and wouldn't own anything else. that was the family 4X4 where I used to live.

I never got one because they were (and still are) kind of expensive. when snow and ice are something that you have to deal with every winter (along with terrain), you have to have something to get you back and forth to work.

even the police force had a subaru outback sport. saw it around a few times and had a few friends that had the grand experience to see it up close (traffic tickets)

BTW, how did this old thread get brought up???

spot, it seems that all old cars (unless they are saturns) are junk. what's up with that?

oh dont put words in my mouth thats just what someone told me about subarus...

Quote:

Originally Posted by JanGeo (Post 149962)

What you are looking at is at light throttle and low burn rates (red) you burn more Grams of fuel to get a KWH of energy output 325 Grams per Kilowatthour. At wide open throttle burning fuel at a high rate (blue) you burn less Grams of fuel to get a KWH or energy output 275 Grams per Kilowatthour (50 grams per KWH less fuel). And the center of the graph is the "sweet spot" to operate the engine however it is also where the engine is producing a lot of torque - centered around 124 Nm of torque in the 1500-3500 RPM range which is probably when you are climbing a hill if you don't have proper gearing to travel at the speed of the road you are on. Keep in mind that this may be the power level needed to go 80 mph which although you end up operating the engine at peak efficiency it is also where there is really high air drag off setting this efficient engine operation with higher than normal speed air drag.

Thanks for your post. I find alot of people forget that you just don't look at the BSFC number itself but you also have to consider how much power or torque is being made to figure out actual fuel consumption.

People tend to get hung up on the good BSFC numbers and don't take in account that if you have great BSFC numbers with high load to medium load you will also have higher Torque or HP numbers in which require more fuel to be burned.

If you have better BSFC and have produced more power, the power hasn't necessarily been wasted; you use the extra work that was done to go further. If you just end up going faster and then braking then you've certainly wasted it.

Quote:

Originally Posted by theholycow (Post 149979)

That has worked best for me. Any time I try to use lighter throttle it ends up being less efficient.

This makes me very happy, because it's alot more fun!
That gives me a new tuning challenge; doing as lean of a burn as possible at 75% throttle, while keeping it at about 13.8:1 at 80%, and 13.7 at 80-100%.
Anyone in the Portland, OR area want to help with this?

It's no more fun. You don't go any faster.

Oh, I do ;) The difference between 25% and 75% is drastic on my car.
I'm concerned that I may get a ticket for "display of speed", or something. Sometimes I have to not give any gas coming from a stop, and always have to slip the clutch a bit, to not spin the tires.
At 75% throttle, my car would do the ? mile in about 17 seconds (at 90+%, it does high 13s).
I acknowledge that in normal cars, it wouldn't make much difference.
My car is far from normal, though.

If you're going faster, you're doing it wrong. You may not gain a fuel economy improvement; you may in fact lose fuel economy.

I often shift when I've only reached 1200RPM. You may need to go lower than that. The strategy may not be compatible with your car. Experimentation will answer all of these questions for sure.

Oh.
I get it.
I'll try it, and see how it works out.