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Old 05-15-2019, 04:56 PM   #51 (permalink)
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LOL your basic understanding of modern fuel systems is a impressive ZERO. All my cars, including the big ram 3500, get 30%+ better millage at 70 than they do at 55. Why you ask? Efficiency of the motor. You get it up to the sweet spot where it can hold an RPM due to gearing, and it burns LESS fuel to maintain that speed, because it is not having to constantly fight the gears and work harder. (I find that to be somewhere around 2800rpm in both my turbo cars, around 2k on the diesel.)
You're so full of shit. The aero load difference between 70 and 55 is huge, and that's what you're using most of the BTU's in that engine for. This example is for OTR trucks, but the physics are the same for any vehicle, including a bicycle.

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Above 55MPH "AERODYNAMIC HORSEPOWER DEMAND INCREASES BY THE CUBE OF SPEED INCREASE".
How this plays out is a truck that can achieve 7 MPG at 55 MPH, will get 6 MPG at 65 MPH and only 5MPG at 70MPH
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Old 05-15-2019, 05:00 PM   #52 (permalink)
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You're so full of shit. The aero load difference between 70 and 55 is huge, and that's what you're using most of the BTU's in that engine for. This example is for OTR trucks, but the physics are the same for any vehicle, including a bicycle.
^^This. Other posts are lulz.


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Old 05-15-2019, 06:10 PM   #53 (permalink)
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I did, to some degree it's pretty much just his opinion. Take a look at historical data from credible sources (NHTSA, IIHS, insurance companies, etc.) and the data shows otherwise.

The "better mpg at higher speed on the highway" statement would be nice if it were true, but it isn't unless somethings wrong with the vehicle or you've got unbelievably massive feac loads. It only becomes true around 20mph when your feac loads (constant vs. speed) are getting to be a large percentage of engine torque load.

Read up on automotive LVD modeling. Rolling resistance and air drag are approximately a square of vehicle speed. The bsfc improvement of loading the engine at a higher torque through gearing would be pretty minor compared to the appx. doubled amount of total drag going 70mph vs 55mph.
You're wrong because diesels have a really peaky torque curve and that guy found it was 2000 rpm.

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Truckers passing each other at 45 mph in 75mph going up a hill here should be shot. Even on I-17 up Black Canyon where signs specifically tell truckers to stay to the right, this happens ALL THE TIME.

Stay the hell in the right lane.
I love people complaining about truckers as they rush to the mall to buy stuff.

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I still maintain that someone driving at 100 mph is probably safer than the average idiot doing the speed limit completely distracted by everything ni their car.

those of use going legitimately fast are actually paying attention.
I hit triple digits everyday, usually on a road posted 55 mph.
no fucks given about what the fucking sign says.
What a rebel.

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I have no problems with going slower than the limit.

just keep your ass to the right.

I will fucking murder you for going the limit and pacing the car next to you in the left lane.
when I flash my lights at you, that means I want you to get the fuck out of my way, because I intend on going much faster than you. The fact that I approached your bumper at a 30mph closing speed was your first clue.
Ooooh, aggresive. Plus, you have determined that you're the finest driver you know. Huh.
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Old 05-15-2019, 06:37 PM   #54 (permalink)
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So stay out, nobody will miss you. Some people recognize that hitting a deer/moose/bear/tree or sliding off an icy road and rolling into a ditch is their fault, not an "accident" and they slow down when the conditions dictate.

All higher speed limits do is result in people driving more, commuting farther, and buying more gas. The extra tax revenue is the only reason there is a speed limit over 55mph in this country.
This. US41 and US2 along with most roads in the UP are still mostly 2 lane and pass through many small towns. 65 is too damn fast for these wooded highly animal populated hiways.
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Old 05-15-2019, 06:41 PM   #55 (permalink)
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LOL your basic understanding of modern fuel systems is a impressive ZERO. All my cars, including the big ram 3500, get 30%+ better millage at 70 than they do at 55. Why you ask? Efficiency of the motor. You get it up to the sweet spot where it can hold an RPM due to gearing, and it burns LESS fuel to maintain that speed, because it is not having to constantly fight the gears and work harder. (I find that to be somewhere around 2800rpm in both my turbo cars, around 2k on the diesel.)
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Old 05-15-2019, 06:43 PM   #56 (permalink)
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You're so full of shit. The aero load difference between 70 and 55 is huge, and that's what you're using most of the BTU's in that engine for. This example is for OTR trucks, but the physics are the same for any vehicle, including a bicycle.
Since we used my car as the example, lets go with that...

So, Same road, same drive, same lack of traffic, start with same full tank, no change in tune, same % of E85. 65mph I get exactly 8mpg, run it up and keep it at 85, and I now get 10mpg.

I will wait while you try to explain that.
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Old 05-15-2019, 06:43 PM   #57 (permalink)
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Wyoming and Montana have fairly new 80mph most places. Fatalities have gone up each time the speed limit is raised. It also went up when they had the Reasonable and Prudent.
Utah is 80 in areas now also.
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Old 05-15-2019, 06:55 PM   #58 (permalink)
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Cross from parts of NM to Tx and all the sudden the speed jumps from 55 MPH 75 MPH road is the same construction just cross the state line
I was driving on Hwy 62 from Carlsbad to El Paso in a Nissan Frontier rental and I had that thing maxed out at around 95mph into a stiff headwind getting passed left and right.
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Old 05-15-2019, 06:57 PM   #59 (permalink)
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Since we used my car as the example, lets go with that...

So, Same road, same drive, same lack of traffic, start with same full tank, no change in tune, same % of E85. 65mph I get exactly 8mpg, run it up and keep it at 85, and I now get 10mpg.

I will wait while you try to explain that.
What car? Any mods? Change tire size? Is it reading the same amount of miles at the different speeds?
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Old 05-15-2019, 07:04 PM   #60 (permalink)
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What car? Any mods? Change tire size? Is it reading the same amount of miles at the different speeds?
Same car, modded, held at same speed (as close as CC can do), readings taken from COBB software off OBD2 port (during my road testing of the tune at the time) . Same tires, I would imagine same air pressure as it was done same day.

Testing was done looking for an issue I was having under 3000rpm. I do not rule that out as a possible contributing factor (surging when put under load at 0 bar under 3k)
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Old 05-15-2019, 07:09 PM   #61 (permalink)
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Wyoming and Montana have fairly new 80mph most places. Fatalities have gone up each time the speed limit is raised. It also went up when they had the Reasonable and Prudent.
Reasonable and Prudent was awesome !
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Old 05-15-2019, 07:27 PM   #62 (permalink)
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My commute is a flat 35 miles in almost a straight line. I have driven the whole thing on the 128mph governor in my car. I'd fall asleep doing the 55/60mph speed limit.

90mph limit would be nice. But I'd settle for 75 like Texass has.

Nobody around here does the speed limits on the highways. Always 10 over and the police don't seem to mind it that much. Maybe they don't like driving 55 either.
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Old 05-15-2019, 08:04 PM   #63 (permalink)
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Same car, modded, held at same speed (as close as CC can do), readings taken from COBB software off OBD2 port (during my road testing of the tune at the time) . Same tires, I would imagine same air pressure as it was done same day.

Testing was done looking for an issue I was having under 3000rpm. I do not rule that out as a possible contributing factor (surging when put under load at 0 bar under 3k)
so you're calculating it by injector pulse time vs VSS
on something with aftermarket injectors and ecu maps

larboc knows his shit real good and is in tight with the skunkworks of some OEMs near as I can tell, but you don't need none of that to have the most basic understanding of aerodynamic loading
that aside, you're making stupid claims backed up with poor data

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Old 05-15-2019, 08:51 PM   #64 (permalink)
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Same car, modded, held at same speed (as close as CC can do), readings taken from COBB software off OBD2 port (during my road testing of the tune at the time) . Same tires, I would imagine same air pressure as it was done same day.

Testing was done looking for an issue I was having under 3000rpm. I do not rule that out as a possible contributing factor (surging when put under load at 0 bar under 3k)
Turbo, right? More pressure at higher RPM, greater efficiency?
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Old 05-15-2019, 09:25 PM   #65 (permalink)
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Most our freeways in utah are 80mph now. You cant even tow your boat over 55 in Cali and we will let semis blast down the freeway doing 80 if they can. I have contractor friend that does service work in the UDOT buildings around the state and he says hes seen speed limit signs for 85.
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Old 05-16-2019, 04:28 AM   #66 (permalink)
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This. US41 and US2 along with most roads in the UP are still mostly 2 lane and pass through many small towns. 65 is too damn fast for these wooded highly animal populated hiways.
Screw off grandpa. Nobody is forcing you to go that fast. The people that want to go that fast on a rural highway should be able to.
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Old 05-16-2019, 05:04 AM   #67 (permalink)
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that aside, you're making stupid claims backed up with poor data
Yeah, welcome to an OverBear post.
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Old 05-16-2019, 05:15 AM   #68 (permalink)
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Most our freeways in utah are 80mph now. You cant even tow your boat over 55 in Cali and we will let semis blast down the freeway doing 80 if they can. I have contractor friend that does service work in the UDOT buildings around the state and he says hes seen speed limit signs for 85.
You've driven across the Salt Flats.
There is no reason it shouldn't be 85 from Wendover to the Toole exit.

Nevada has some areas that they moved up to 80 with a sign below that says "Strictly Enforced" so I only do about 84 in those areas.
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Old 05-16-2019, 05:24 AM   #69 (permalink)
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Screw off grandpa. Nobody is forcing you to go that fast. The people that want to go that fast on a rural highway should be able to.
This is funny because most grandpas I know up there run 70. The people that don't run the speed limit up there are the same ones that couldn't run the speed limit when it was 55.
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Old 05-16-2019, 05:36 AM   #70 (permalink)
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Since we used my car as the example, lets go with that...

So, Same road, same drive, same lack of traffic, start with same full tank, no change in tune, same % of E85. 65mph I get exactly 8mpg, run it up and keep it at 85, and I now get 10mpg.

I will wait while you try to explain that.
There's something wrong with your car unless it's a truck. I don't know what car you have, if the engine is heavily modified, or what the coast down curve looks like, but if it's getting 8mpg at 65mph you'd better be grossing 20,000lbs, even on e85. I'd start there.

There's no getting around physics, it's going to take around twice the power to push a vehicle at 85mph as 65mph. Google some typical SI engine bsfc maps (or better yet pick up a copy of heywood) and look at how implausible it would be for an engine to use 20% less fuel to make twice the horsepower anywhere near road load conditions. Unless of course it was tuned really badly or the gearing was way off for street use. Could also be fuel leaking out onto the ground at a constant rate, making your MPG look better with higher ground speeds.
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Old 05-16-2019, 06:05 AM   #71 (permalink)
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The fuck are you smoking?

90s cars are perfectly fine up to triple digit speeds. It's the trucks and other things that need to punch a big hole in the air that don't do all that well at 75+ with sub-200hp.
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I did, to some degree it's pretty much just his opinion. Take a look at historical data from credible sources (NHTSA, IIHS, insurance companies, etc.) and the data shows otherwise.

The "better mpg at higher speed on the highway" statement would be nice if it were true, but it isn't unless somethings wrong with the vehicle or you've got unbelievably massive feac loads. It only becomes true around 20mph when your feac loads (constant vs. speed) are getting to be a large percentage of engine torque load.

Read up on automotive LVD modeling. Rolling resistance and air drag are approximately a square of vehicle speed. The bsfc improvement of loading the engine at a higher torque through gearing would be pretty minor compared to the appx. doubled amount of total drag going 70mph vs 55mph.
I am aware of the aerodynamics.

I'm also aware that if I drive at 55, my junk constantly drops a gear because it wants to be in 6th at all times, but at 55 that's like 1500 rpm, so the motor downshifts every time you breathe on the pedal, or hit a slight incline.
murders the fuel mileage.
that may be more of an auto trans thing than anything else.
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Old 05-16-2019, 06:10 AM   #72 (permalink)
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What a rebel.



Ooooh, aggresive. Plus, you have determined that you're the finest driver you know. Huh.
I do what I want. You should try it some time.

I am not aggressive. Far from it actually. I am courteous, I let people zipper merge, I don't tailgate, I always use my signals.
I drive fast, and I do it more safely than most of the fucking idiots I see on the road glued to their damned phone trying to kill everyone else that are doing the speed limit.

until a few months ago I hadn't had a speeding ticket in 20 years.
fucking sneaky sneaky airplane got me.
and I haven't had a car off the road since I was 16 and driving in my first winter.

so I'd say my driving record does indeed indicate that I am better than average. My ridiculously low insurance rates also seem to confirm that
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Old 05-16-2019, 06:19 AM   #73 (permalink)
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I am aware of the aerodynamics.

I'm also aware that if I drive at 55, my junk constantly drops a gear because it wants to be in 6th at all times, but at 55 that's like 1500 rpm, so the motor downshifts every time you breathe on the pedal, or hit a slight incline.
murders the fuel mileage.
that may be more of an auto trans thing than anything else.
The shifting may be annoying, but the gear change fuel penalty still shouldn't offset the halving of road load power demand from 70 to 55 unless something is seriously wrong.

Have you tried manually selecting 5th?
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Old 05-16-2019, 06:28 AM   #74 (permalink)
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The shifting may be annoying, but the gear change fuel penalty still shouldn't offset the halving of road load power demand from 70 to 55 unless something is seriously wrong.

Have you tried manually selecting 5th?
haven't really.

I'm also not sure about torque converter lockup and shit.
It does what it does and I don't fuck with it unless it quits doing what it's supposed to do.

but having driven the same stretch of road at varying speeds, it gets 1mpg better doing 70 on that road than it does doing 55. Its your average 2 lane hilly country road.

according to the instant lie o meter anyhow, which has proven to be pretty accurate. At least to within a half MPG when compared to hand calculating.

there's also crazy intake manifold shit that happens with variable length runners and shit.
who the fuck knows what the krauts have going on in there.
short of changing the tune to 330 stuff, I haven't fucked with the DME to find out what makes it tick.
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Old 05-16-2019, 06:39 AM   #75 (permalink)
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short of changing the tune
start changing things, it's real easy to set up the maps wrong in spots, end up with little islands of just barely lean enough to run (8-9:1 afrs)
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