If accessories could kill… MPG

[InlineDave87]

So, i did a crude test today as i had a customer that was 40 miles away to see how much my AC is killing my MPG. I took advantage if the cooler morning and the 2-55 AC (1/4 window open). Running my AC i was barely getting double digits for MPG and with todays test i got about 15.5mpg. Its got me wondering if there is something majorly wrong with my AC if im loosing 4-5 mpg with it on. Then it made me remember this test from Engine Masters and thought this could be a good thread to discuss parasitic loss.

 

[aussie7mains]

AC needs a lot of power, probably around 2-4kw, so yes thats going to affect fuel economy. Anything that takes power will, the alternator, water pump, air pump etc. And IMO the most wasteful of all is the auto transmission, first off even with a lock up clutch in the convertor, the oil pump takes power, then we have the constant drag of all those bits running around. Without a lock up clutch things get worse.

 

[Shorty]

gear oil instead of ATF in the M5od would be a parasitic loss too I would think. Accessories bolted to the truck (visors and stuff like that) would also have an adverse affect on economy. Large tires of a grippy soft rubber compound rather than properly inflated tires with with "normal" tread pattern. It's a good thing I don't have a long commute.

I just converted my alternator to a 3G. Would that have a greater parasitic loss than the original alternator?

 

[Frank]

Large tires of a grippy soft rubber compound rather than properly inflated tires with with "normal" tread pattern.

tires have a huge impact on economy. Knobby or even square-type tread pattern (Good Year Wranglers) use more fuel. Late in my trucking career stopped using the knobby drive tires, and went to straight-line grooved "steer" tires on the 8 drive wheels. Gave a several % increase in economy, reduced humming road noise considerably, and actually tracked and pulled better in snow than the knobbys, which would pack the square groves worse than the straight groove tires.
Every lb of underinflation reduces economy several %. Max inflation rides rougher, but economy and tire life are worth it.

 

[aussie7mains]

gear oil instead of ATF in the M5od would be a parasitic loss too I would think. Accessories bolted to the truck (visors and stuff like that) would also have an adverse affect on economy. Large tires of a grippy soft rubber compound rather than properly inflated tires with with "normal" tread pattern. It's a good thing I don't have a long commute.

I just converted my alternator to a 3G. Would that have a greater parasitic loss than the original alternator?

The drag caused by higher viscosity oil in the transmission would be almost unmeasurable in the grand scheme of things tyres would also not rank very high unless they were very low in pressure, the energy loss in a tyre is due to the flexure in the side walls. As to your altenator, it will only supply the load applied to it, if that hasnt changed then it wont be any different.

 

[InlineDave87]

The drag caused by higher viscosity oil in the transmission would be almost unmeasurable in the grand scheme of things tyres would also not rank very high unless they were very low in pressure, the energy loss in a tyre is due to the flexure in the side walls. As to your altenator, it will only supply the load applied to it, if that hasnt changed then it wont be any different.

Funny story, i double checked my tire pressures this morning. Front are suppose to be 35 and rear 41. Found my tires were at 31ish all the way around. Got the front to 35 psi and the rear to 43ish. Had a 43 mile drive this morning for work so i decided to check to see what the difference the tire pressures makes. It was mixed driving, but mostly highway with speed trap zones. Ended up using 2.4 gallons which netted me 17.9 mpg compared to my last test last week where i got 15 mpg with just turning off the AC. The AC remained off for this trip too. I still think my truck should be getting me better mpg than that but im happy for now with the results.

 

[Jesse73]

Funny story, i double checked my tire pressures this morning. Front are suppose to be 35 and rear 41. Found my tires were at 31ish all the way around. Got the front to 35 psi and the rear to 43ish. Had a 43 mile drive this morning for work so i decided to check to see what the difference the tire pressures makes. It was mixed driving, but mostly highway with speed trap zones. Ended up using 2.4 gallons which netted me 17.9 mpg compared to my last test last week where i got 15 mpg with just turning off the AC. The AC remained off for this trip too. I still think my truck should be getting me better mpg than that but im happy for now with the results.

Just goes to show what a little “optimization” can do.

There are a lot of things you can do without compromising on utility. If you don’t have a front air dam, that helps a little on the highway. Tonneau cover on the bed helped me about 1/2 mpg on the highway as well.

I always wonder how much energy my power steering pump uses. As far as in town driving, I’m not ever going back to a manual box. But I do think possibly a larger diameter pulley could be fitted to the pump to drag less on the engine. Pump runs to bypass most of the time anyway I’m led to understand.

 

[Frank]

Just goes to show what a little “optimization” can do.

There are a lot of things you can do without compromising on utility. If you don’t have a front air dam, that helps a little on the highway. Tonneau cover on the bed helped me about 1/2 mpg on the highway as well.

I always wonder how much energy my power steering pump uses. As far as in town driving, I’m not ever going back to a manual box. But I do think possibly a larger diameter pulley could be fitted to the pump to drag less on the engine. Pump runs to bypass most of the time anyway I’m led to understand.

Pumps use surprisingly little HP. Can't put hands on the math right now, but it's surprising. Probably more total power is consumed by the belt than the pump. Serpentine wins the economy prize here.

 

[63 Sprint]

At one time it was calculated that each rib on a serpentine belt is able to handle up to 2 hp load.

 

[InlineDave87]

I always wonder how much energy my power steering pump uses. As far as in town driving, I’m not ever going back to a manual box. But I do think possibly a larger diameter pulley could be fitted to the pump to drag less on the engine. Pump runs to bypass most of the time anyway I’m led to understand.

I know there are aftermarket electric power steering units out there that might pair nicely with a manual box. Ive thought of doing this to eliminate parasitic loss from the ps pump and also to free up a spot for possibly a supercharger in the future.

 

[Frank]

Are there some that pair with a manual box? The few I glanced at came with a rack/pinion. Not going there. Have a link?

 

[sixtseventwo4d]

Auto trans or standard; Dave?

 

[Frank]

At 14 volts, 53 amps pulls 1 HP.

 

[InlineDave87]

Auto trans or standard; Dave?

Standard m5od r2

 

[InlineDave87]

Are there some that pair with a manual box? The few I glanced at came with a rack/pinion. Not going there. Have a link?

Universal Electric Power Steering Kit - ePowerSteering.com

Universal Electric Power Steering Kit - ePowerSteering.com

epowersteering.com

Sorry for the late reply. Flaming Rivers has some that replace the whole steering column thats more than i would want to pay, but i found this one thats almost a third of the price. Not to toot my own horn but i got mad google skills

 

[InlineDave87]

So heres a good one today. On my newer truck my battery went dead as i was taking my wife to work today. I ended up having to jump it get my wife to work then fuel it up and go get a new battery. When i fueled it up it showed me about 350 miles to empty. After swapping out the battery the miles to empty went up to 410. My tank is a 26 gal tank so it was worth little more than 2 mpg. Goes to show what an electrical load can do on your engine.

 

[aussie7mains]

At 14 volts, 53 amps pulls 1 HP.

No account for inefficiency, 14v @ 53 a is 746w= 1 hp, but an alternator is only about 60% efficiency, so its more like 1250w. As to an electric ps pump, again, it will only draw what is needed to operate, so could be quite low on average. Parasitic loss is real, but most of it is down to those dreaded slushies, a manual trans running in a direct gear will give lower losses. Think of how hot a slushie gets, thats wasted energy! If you were really serious about economy you would be driving a manual trans 1000kg vehicle with a small diesel, and no AC. The pommes are masters at this.

 

[gb500]

The pommes are masters at this.

For those not in Australia -
'Poms( or Pommies)' is an Australian term of endearment for the English

 

[InlineDave87]

Automatic trans these days are more efficient and some even surpass manual trans (or so they say). They are just not as fun to drive. My truck has the M5OD R2. Im fixing to start up a youtube channel where Ill test and experiment to see what helps save fuel outside of the norm. Then depending on how things go, change it over for performance. If im lucky it can be both.

 

[danriffle]

How about switching to an electric fan to avoid the parasitic loss there?