Hi, all.
I was coming back from San Francisco tonight, and traffic was light, so I tried to do a very simplistic mileage test using the built-in MPG measuring system.
(As a side note, I remembered a factoid from my 1991 Q45: once the cruise control is engaged, each click of the Set button reduces the speed setting by 1 mph, and each click of the Reset/Accel button increases the setting by 1 mph. Sure enough, it works the same on my M45 and the speed setting were exact (reading the speedo carefully, of course). Cool! )
Anyway, here is what I did:
* Starting at 60 mph,* I set the cruise control in 5 mph increments from 60 mph to 80 mph,* let the car settle into the speed for about a mile,* reset the MPG counter,* recorded the average MPG after 5 miles.* If the road wasn't reasonably flat in that 5 mile section, I would reset the counter and go for another 5 miles.
Here are the results and they are kinda interesting and confusing at the same time!
* Indicated 60 mph: 29.1 mpg* Indicated 65 mph: 27.0 mpg* Indicated 70 mph: 25.6 mpg* Indicated 75 mph: 23.2 mpg* Indicated 80 mph: 23.2 mpg
What is interesting (peculiar?) is the slightly higher than expected reading at 70 mph (off the slope), and the lack of a real change from 75 to 80 mph!
Note that, at a steady 65mph, the M45 met its CAFE "mileage" of 27mpg for highway driving! Also cool!
Anyone have any explanations for this? Is it some gearing/engine-power/something-else anomaly?
I think I have going to have to repeat this test someday over a wider range of speeds!
Z
A simple M45 mileage test ... interesting results!
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
At a steady rpm [speed] the fuel is well defined because each cylinder get the same amount per rotation. The O2 sensor ecu feedback loop controls the AVERAGE mixture within 2% at a steady rpm.
If you now the exact amount of mpg at one rpm you can easily calculate what it will be at any other rpm, because from 50-75 mph it is LINEAR except for the slight decreases due to wind resistance.
Indicated 60 mph: 29.1 mpg
Indicated 65 mph: 27.0 mpg [65/60=1.0833 ...29.1/1.083 = 26.8]
Indicated 70 mph: 25.6 mpg
Indicated 75 mph: 23.2 mpg [75/60=1.25.....29.1/1.25=23.28]
Indicated 80 mph: 23.2 mpg
MPG is all rpm [speed] related.HOW much HP an engine can make at high rpm has little to do with the fuel consumption at cruise other than the displacement which has to be filled...........after all at 60 mph you are not making much over 28 HP.
60/29.1=2.0618 gallons per hour x 6.2 pounds = 12.78 pounds per hour/0.45=28.4 HP per hour on average.
It is amazing that the 1985 EPA Highway MPG standards which are for a average speed of 57 mph with no excursions above 60.5 mph are still relied upon today with people driving 75 mph.
IF speeds were limited to 55 mph we could import at least 10% and probably 15% less oil.
If you now the exact amount of mpg at one rpm you can easily calculate what it will be at any other rpm, because from 50-75 mph it is LINEAR except for the slight decreases due to wind resistance.
Indicated 60 mph: 29.1 mpg
Indicated 65 mph: 27.0 mpg [65/60=1.0833 ...29.1/1.083 = 26.8]
Indicated 70 mph: 25.6 mpg
Indicated 75 mph: 23.2 mpg [75/60=1.25.....29.1/1.25=23.28]
Indicated 80 mph: 23.2 mpg
MPG is all rpm [speed] related.HOW much HP an engine can make at high rpm has little to do with the fuel consumption at cruise other than the displacement which has to be filled...........after all at 60 mph you are not making much over 28 HP.
60/29.1=2.0618 gallons per hour x 6.2 pounds = 12.78 pounds per hour/0.45=28.4 HP per hour on average.
It is amazing that the 1985 EPA Highway MPG standards which are for a average speed of 57 mph with no excursions above 60.5 mph are still relied upon today with people driving 75 mph.
IF speeds were limited to 55 mph we could import at least 10% and probably 15% less oil.
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szh
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Unfortunately, no longer a Nissan or Infiniti, but continuing here at NICO! - Location: San Jose, CA
Dennis, thanks very much for your posted response and detailed explanation!
When I started the test, I expected (a) a fairly consistent drop every 5mph plus a little for wind resistance, and (b) that the slope would get a bit steeper downwards as the speeds went up, because wind resistance increases non-linearly with speed. I guess I did not go fast enough to explore item b.
My confusion was with regard to the two anomalous data points at 70mph and 80mph. I will need to repeat these tests someday to get more data.
Inre the HP at 60mph, I had not realized it was that low a need!
As an aside, my wife's Acura 1997 2.2CL gets better gas mileage overall, so I would assume that its steady state gas usage at a constant 60 mph is better than the M45 (although I have not checked yet!) The implication is that it uses less HP to maintain that speed - my intuition says that this is because of (a) lesser vehicle weight, (b) fewer cylinders and (c) smaller frontal area. Am I way off on these assumptions?
Thanks again,
Z
When I started the test, I expected (a) a fairly consistent drop every 5mph plus a little for wind resistance, and (b) that the slope would get a bit steeper downwards as the speeds went up, because wind resistance increases non-linearly with speed. I guess I did not go fast enough to explore item b.
My confusion was with regard to the two anomalous data points at 70mph and 80mph. I will need to repeat these tests someday to get more data.
Inre the HP at 60mph, I had not realized it was that low a need!
As an aside, my wife's Acura 1997 2.2CL gets better gas mileage overall, so I would assume that its steady state gas usage at a constant 60 mph is better than the M45 (although I have not checked yet!) The implication is that it uses less HP to maintain that speed - my intuition says that this is because of (a) lesser vehicle weight, (b) fewer cylinders and (c) smaller frontal area. Am I way off on these assumptions?
Thanks again,
Z
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szh
- Posts: 18857
- Joined: Tue Jul 23, 2002 12:54 pm
- Car: 2018 Tesla Model 3.
Unfortunately, no longer a Nissan or Infiniti, but continuing here at NICO! - Location: San Jose, CA
Q451990 wrote:No doubt! My truck (2.4L) averaged 22MPG on the last tank and I was thrilled!
Heath
Ah! My data was on constant steady-speed measurements ... with a mix of 30% non-highway and 70% highway, I average closer to 16mpg on every tank.
So, your truck is still doing way better than the M45 if you got 22mpg over a full tank of gas!
Z
Sorry to jack the post but man your company sure does do some nice stuff, I love this product.
Left unattended on construction sites overnight and through the weekend, heavy equipment such as road graders, front-end loaders, tract vehicles and skid loaders are convenient targets for thieves and vandals.
“One answer to the problem of heavy equipment theft is a concept we call The Virtual Security Fence,” says Terry Whelan, Operations Manager for National Systems & Research Company (NSR). “One of NSR’s TC 2000 Series products, this technology sets up a virtual perimeter around a piece of equipment using GPS to establish position. If the equipment leaves the perimeter, an alert is forwarded by pager or e-mail via a cellular network to the appropriate party.”
This technological miracle is provided courtesy of the cellular network. Transmissions are short, providing virtually error-free messaging over an ubiquitous network.
Along with providing virtual fencing, NSR’s TC-2000CM also comes equipped with a vibration sensor, automatically activating the system when the vehicle is moved. TC-2000CM can also track a stolen vehicle down the highway, and can even locate it once it has been concealed within a garage or warehouse, a principal advantage over satellite-based systems. Railroads have also expressed interest in TC 2000 products to track locomotives and monitor mechanical functions such as heat and fuel consumption. For railroads, the technology creates a virtual fence in reverse. Instead of receiving messages, a locomotive equipped with the device transmits them, informing the railroad yard, for example, that it is about to arrive.
TC-2000CM can also monitor oil pressure, fuel levels and just about everything else that can be tied to a sensor. These features apply equally to locomotives or heavy equipment. They are particularly advantageous to heavy equipment operators and dealers as they give them the opportunity to repair problems before the vehicle even breaks down.
Left unattended on construction sites overnight and through the weekend, heavy equipment such as road graders, front-end loaders, tract vehicles and skid loaders are convenient targets for thieves and vandals.
“One answer to the problem of heavy equipment theft is a concept we call The Virtual Security Fence,” says Terry Whelan, Operations Manager for National Systems & Research Company (NSR). “One of NSR’s TC 2000 Series products, this technology sets up a virtual perimeter around a piece of equipment using GPS to establish position. If the equipment leaves the perimeter, an alert is forwarded by pager or e-mail via a cellular network to the appropriate party.”
This technological miracle is provided courtesy of the cellular network. Transmissions are short, providing virtually error-free messaging over an ubiquitous network.
Along with providing virtual fencing, NSR’s TC-2000CM also comes equipped with a vibration sensor, automatically activating the system when the vehicle is moved. TC-2000CM can also track a stolen vehicle down the highway, and can even locate it once it has been concealed within a garage or warehouse, a principal advantage over satellite-based systems. Railroads have also expressed interest in TC 2000 products to track locomotives and monitor mechanical functions such as heat and fuel consumption. For railroads, the technology creates a virtual fence in reverse. Instead of receiving messages, a locomotive equipped with the device transmits them, informing the railroad yard, for example, that it is about to arrive.
TC-2000CM can also monitor oil pressure, fuel levels and just about everything else that can be tied to a sensor. These features apply equally to locomotives or heavy equipment. They are particularly advantageous to heavy equipment operators and dealers as they give them the opportunity to repair problems before the vehicle even breaks down.
-
szh
- Posts: 18857
- Joined: Tue Jul 23, 2002 12:54 pm
- Car: 2018 Tesla Model 3.
Unfortunately, no longer a Nissan or Infiniti, but continuing here at NICO! - Location: San Jose, CA
Yup! It is a neat capability.
We regularly see stolen construction and agricultural equipment being recovered very quickly by the Highway patrol after being stolen.
One other customer of ours has set a geofence about 50 miles from the Mexican border on the major highways in Arizona, Texas and California and are now averaging one or two stolen equipment catches per week!
About eight months ago, one of our car theft-recovery systems helped break up a car theft ring in Atlanta. A car was stolen and tracked onto a particular street and the Atlanta Police were dispatched to that street. They called and said that they did not see the car, so we fine-tuned the location into a building - that was sufficient "due cause" for the police to knock on the door and they found a chop shop!
Z
We regularly see stolen construction and agricultural equipment being recovered very quickly by the Highway patrol after being stolen.
One other customer of ours has set a geofence about 50 miles from the Mexican border on the major highways in Arizona, Texas and California and are now averaging one or two stolen equipment catches per week!
About eight months ago, one of our car theft-recovery systems helped break up a car theft ring in Atlanta. A car was stolen and tracked onto a particular street and the Atlanta Police were dispatched to that street. They called and said that they did not see the car, so we fine-tuned the location into a building - that was sufficient "due cause" for the police to knock on the door and they found a chop shop!
Z
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Q45tech
- Moderator
- Posts: 14365
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
A 4 cylinder has two injections per rpm a V8 has 4.A 2.2 liter has 550cc cylinders a 4.5 liter V8 has 561.75 cc only 2% larger........call it a wash, so at the exact same rpm a V8 uses twice as much fuel per minute second hour year. A V8 even uses twice as much at idle. A V8 has more internal friction to overcome than a I4 per minute.
Unfortunately a 4 cyclinder has to rev 20-25% higher to achieve adequate torque to maintain the same cruise speed as the virtually unstressed V8.
So a 2.2 liter I4 might be compared to a 2.64 liter engine.
Even the V6 have to rev higher but usually only 10-15% so a 3.5V6 [583 cc] acts like a 3.92 liter unit.
Notice that most cylinders are in the 500-600cc range. But at cruise the volumetric efficiency is so low [around 20%] that they only receive 100cc of air or less.........
So it's really only fair to compare the same type [V8, V6, I4] as to displacementThe older 4.0 V8 Lexus engine use to get 10-12% better MPG at the same speed as the Q45 4.5 liter......they both turned 1950-2000 rpm at 60 mph and MB V8 5.0 liters got 10% worse than the Q.
Unfortunately a 4 cyclinder has to rev 20-25% higher to achieve adequate torque to maintain the same cruise speed as the virtually unstressed V8.
So a 2.2 liter I4 might be compared to a 2.64 liter engine.
Even the V6 have to rev higher but usually only 10-15% so a 3.5V6 [583 cc] acts like a 3.92 liter unit.
Notice that most cylinders are in the 500-600cc range. But at cruise the volumetric efficiency is so low [around 20%] that they only receive 100cc of air or less.........
So it's really only fair to compare the same type [V8, V6, I4] as to displacementThe older 4.0 V8 Lexus engine use to get 10-12% better MPG at the same speed as the Q45 4.5 liter......they both turned 1950-2000 rpm at 60 mph and MB V8 5.0 liters got 10% worse than the Q.
In Seattle I always found everyone going 59mph in a 60. It seemed like almost paranoid rank and file behavor -- cant blame them, since the state is desperate for revenue. In Spokane it was usually 69mph in a 60. And on I-5, youre entrenched in your novel and not really moving at all. 100mph+ on I-90 through Cle Elum all the way to Ellensburg.
-Jesda
-Jesda
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