What does your Tachometer read @ 80 MPH on the interstate?

[HVACTech]

I recently made two trips in my 1989 Dodge Ram. averaging 80 MPH (with 85 to 90 at times)
I got 13.5 MPG with the A/C on. and on the second trip I got the same with the A/C off. that was not what I expected.

I asked my friend what he was getting in his nearly new truck. (probably a 2015)
and he said at those speeds. about 15. he did not remember the Tach reading.

what are you getting?

(I calculate my RPM's to be 2350 @80MPH.)

[oyarde]

In my 04 F150 , about 20 mpg @ 70 mph . In the 06 Impala I was driving before that , 29 mpg @ 80 mph . I do not think the AC makes any difference .

[Anti Federalist]

About 2100 in a VW diesel.

[fisharmor]

3k in my 91 Saturn 5 speed. That's one of the many things Saturn $#@!ed up with the 96 redesign. Changed the ratios so does 3500 at 80.

2350 for a truck sounds really low. Is it a manual? That's the only way I could see it being under 3500 in your truck. All the auto trucks I've driven are revving pretty high at 80.

[TheCount]

Somewhere around 6k on the bike

[HVACTech]

3k in my 91 Saturn 5 speed. That's one of the many things Saturn $#@!ed up with the 96 redesign. Changed the ratios so does 3500 at 80.

2350 for a truck sounds really low. Is it a manual? That's the only way I could see it being under 3500 in your truck. All the auto trucks I've driven are revving pretty high at 80.

I swapped out the 3 speed for an overdrive. it is a 43RH and the specs are .069 for the overdrive. coupled with a 3.55 rear end and 28" tires... that calculates to 2350 rpm. at 80 MPH
as near as I can tell.. this is the same set up all the new trucks are running.
I think in 5th gear, that is not overdrive. without overdrive, the engine RPM and the wheel RPM are one and the same.
that is sorta why I am asking.
when the speed limit is 75. most folks are running 80.

[specsaregood]

About 2100 in a VW diesel.

I thought those were illegal now, reported.

About 3k in a 2007 Honda Element. It gets about 20mpg whatever the situation. It's like a big box on wheels.

[HVACTech]

About 2100 in a VW diesel.

I wonder if that holds true for the big diesels.

[luctor-et-emergo]

I wonder if that holds true for the big diesels.

I think my $#@! car (it's French) does about 3100rpms in 5th gear at 80mph. Next car will have 6 gears.

[fisharmor]

I swapped out the 3 speed for an overdrive. it is a 43RH and the specs are .069 for the overdrive. coupled with a 3.55 rear end and 28" tires... that calculates to 2350 rpm. at 80 MPH
as near as I can tell.. this is the same set up all the new trucks are running.
I think in 5th gear, that is not overdrive. without overdrive, the engine RPM and the wheel RPM are one and the same.
that is sorta why I am asking.
when the speed limit is 75. most folks are running 80.

I daresay you should be doing better than 13.5 then. I think the only truck I had that was that bad was a 77 chevy fullsize van with a 400, 3 speed, and high differentials.

[tod evans]

I daresay you should be doing better than 13.5 then. I think the only truck I had that was that bad was a 77 chevy fullsize van with a 400, 3 speed, and high differentials.

I had a '78 Chevy 1 ton full time 4-wd with 4.56 lockers under both ends, 70mph was 5600rpm, it got around 6-7mpg loaded or unloaded (built small block) but it'd pull a house if you could hook it up.

My 56 doesn't do 80mph either.....

[DamianTV]

I'll have to take a look, I think about 2500 RPMs at 80.

[pcosmar]

No Idea

I don't drive 80.

[satchelmcqueen]

in my 06 liberty (3.7L) i am at 2600@ 80mph. i get about 17mpg.

in my 70 maverick (200 straight 6) i am at 3300 @ 80mph. i get about 15mpg.

[cjm]

There's a very good forum out there at http://ecomodder.com that covers a lot of fuel efficiency stuff: mods, deletes, hypermiling, non-E fuel, etc. I recommend checking it out.

...and speaking of non-E (for those that haven't heard of it): http://pure-gas.org/

...and to answer the question -- don't know RPM at 80mph, but will take a look next time I'm out.

[HVACTech]

I daresay you should be doing better than 13.5 then. I think the only truck I had that was that bad was a 77 chevy fullsize van with a 400, 3 speed, and high differentials.

I was disappointed when I checked the MPG. but I am not so sure now..
it has EFI but it is throttle body of course.
it only has one oxygen sensor, and we mounted it on the drivers side collector for the headers.

I have been driving this very same truck for 12 years. and I was just about to get rid of it...AGAIN...
when I found a set of factory bucket seats and the console as well....

that is the same as a boob job for an old truck. (trucks don't rust where I live)

[HVACTech]

in my 06 liberty (3.7L) i am at 2600@ 80mph. i get about 17mpg.

in my 70 maverick (200 straight 6) i am at 3300 @ 80mph. i get about 15mpg.

that sounds like the other honest answers that I have got so far... I see these crazy #'s and I think.. where? in Kansas with a tailwind?
I asked the question because there are lots of cars running that speed today.

200 cubic inches converts to 3.2 liters. I bet the Liberty has overdrive and the maverick does not...

[HVACTech]

I think my $#@! car (it's French) does about 3100rpms in 5th gear at 80mph. Next car will have 6 gears.

80 MPH converts to 128 KPH.... I wish my $#@!ing country would desist from forcing me to make all these $#@!ing conversions!
WTF America!
cue @Anti Federalist

there is only ONE way to measure Revolutions... and Americans are about to find out.

[satchelmcqueen]

that sounds like the other honest answers that I have got so far... I see these crazy #'s and I think.. where? in Kansas with a tailwind?
I asked the question because there are lots of cars running that speed today.

200 cubic inches converts to 3.2 liters. I bet the Liberty has overdrive and the maverick does not...

you are very correct. overdrive on liberty and only 3 gears in the maverick. the maverick only weighs 2800lbs but those rpms are high for gas. i usually drive it 65. when i get my 347 in it, itll be a 6 speed auto.im aiming for a gear thatll get me at 2500rps at 90mph.

[HVACTech]

you are very correct. overdrive on liberty and only 3 gears in the maverick. the maverick only weighs 2800lbs but those rpms are high for gas. i usually drive it 65. when i get my 347 in it, itll be a 6 speed auto.im aiming for a gear thatll get me at 2500rps at 90mph.

when I first put in the overdrive, I tried to run the original 2.76 rear end gears.. it did not work worth a $#@!.
what I learned along the way.. is that each engine has a "torque curve"
torque is what spins the wheels. not Horsepower.

I was shooting for low end torque. (it is a truck) and I use it as a truck.
since it an 89.. I was concerned that I was running it too fast on the interstate.
the gas pedal feels REALLY good at 80 MPH.

[Anti Federalist]

is that each engine has a "torque curve"
torque is what spins the wheels. not Horsepower.

Long stroke, less cylinders, higher compression, lower RPM = more torque.

Short stroke, more cylinders, average compression, higher RPM = more horsepower.

As a rough rule of thumb.

Diesels are ideally suited to automotive applications.

But we can't have them.

Because Uncle, and his kingly decrees and fatwas.

[HVACTech]

Long stroke, less cylinders, higher compression, lower RPM = more torque.

Short stroke, more cylinders, average compression, higher RPM = more horsepower.

As a rough rule of thumb.

Diesels are ideally suited to automotive applications.

But we can't have them.

Because Uncle, and his kingly decrees and fatwas.

you are one strange cat...

diesel is an oil. and exhibits a much longer flame (plasma) propagation time.
(diesel expands for a longer period of time)
this is why it produces more low end torque.
octane has a high vapor pressure. (diesel is very low) octane needs other stuff to be mixed in.
to control it's vapor pressure. or, like @<u><a href="http://www.ronpaulforums.com/member.php?u=38380" target="_blank">Suzanimal</a></u> it will burn hot and fast.

when you mix "other" stuff in with octane. it becomes 'Gasoline"

how can you tell how much of the "good stuff" (octane) that you are getting?
look at the pump, (look at the fine print) it will give you the octane rating!

Reid vapor pressure (RVP) is a common measure of the volatility of gasoline. It is defined as the absolute vapor pressure exerted by a liquid at 100 °F (37.8 °C) as determined by the test method ASTM-D-323.

if, perchance. you DO NOT KNOW what the volatility of octane, has to do with absolute vapor pressure....
mebbe you should NOT have pissed off your very favorite HVACTech!

[Danke]

I would never drive at 80 mph, that would be illegal here.

[oyarde]

I would never drive at 80 mph, that would be illegal here.

My 57 Chevy had no seat belts and got 17 mpg at 50 mph to 80 mph so I just drove it 80 , I do not think it is illegal here for a barefoot Indian smoking a cigarette to drive 80 with a straight 6 and the window down drinking a Miller High Life with no seat belt . At least I hope not , Lol

[Danke]

My 57 Chevy had no seat belts and got 17 mpg at 50 mph to 80 mph so I just drove it 80 , I do not think it is illegal here for a barefoot Indian smoking a cigarette to drive 80 with a straight 6 and the window down drinking a Miller High Life with no seat belt . At least I hope not , Lol

Injuns always think they are above the law. We used to have a solution for that.

[HVACTech]

I would never drive at 80 mph, that would be illegal here.

I like to visit my friends in Texas.

Speed limits in the United States vary depending on jurisdiction, with 75 to 80 mph (120 to 130 km/h) common in the Western United States and 65 to 70 mph (100 to 110 km/h) common in the Eastern United States.
https://en.wikipedia.org/wiki/Speed_...y_jurisdiction

[Suzanimal]

you are one strange cat...

diesel is an oil. and exhibits a much longer flame (plasma) propagation time.
(diesel expands for a longer period of time)
this is why it produces more low end torque.
octane has a high vapor pressure. (diesel is very low) octane needs other stuff to be mixed in.
to control it's vapor pressure. or, like @<u><a href="http://www.ronpaulforums.com/member.php?u=38380" target="_blank">Suzanimal</a></u> it will burn hot and fast.

when you mix "other" stuff in with octane. it becomes 'Gasoline"

how can you tell how much of the "good stuff" (octane) that you are getting?
look at the pump, (look at the fine print) it will give you the octane rating!

Reid vapor pressure (RVP) is a common measure of the volatility of gasoline. It is defined as the absolute vapor pressure exerted by a liquid at 100 °F (37.8 °C) as determined by the test method ASTM-D-323.

if, perchance. you DO NOT KNOW what the volatility of octane, has to do with absolute vapor pressure....
mebbe you should NOT have pissed off your very favorite HVACTech!

I'm not burning hot and fast. O_o I'm a nice girl. I don't even know what I'm doing in this thread. I don't know anything about cars and less about gas.

[tod evans]

I'm not burning hot and fast. O_o I'm a nice girl. I don't even know what I'm doing in this thread. I don't know anything about cars and less about gas.

Lemmie tell you 'bout my bean recipe....

[Suzanimal]

Lemmie tell you 'bout my bean recipe....

Mr Animal made some super spicy charros beans last year and farted all night for a few days. He was killing me. I woke him up beating him with a pillow in the middle of the night several times. He was sleeping on his side with his butt facing in my direction and damn near gassed me out of the room. I'm not kidding, I woke up gagging it was so bad. I still get nervous when he eats beans, I think he gave me PTSD.

[satchelmcqueen]

when I first put in the overdrive, I tried to run the original 2.76 rear end gears.. it did not work worth a $#@!.
what I learned along the way.. is that each engine has a "torque curve"
torque is what spins the wheels. not Horsepower.

I was shooting for low end torque. (it is a truck) and I use it as a truck.
since it an 89.. I was concerned that I was running it too fast on the interstate.
the gas pedal feels REALLY good at 80 MPH.

yes. im going to use a streetfighter trans thats like the original C4, but it is able to handle around 500hp. the 347 im putting in dynos at 400 and around 450 torque. but the key thing to my gearing will be an overdrive unit made by a company called gear vendor. its a simple bolt on to the trans that replaces the tail section. it splits each gear and makes the 3 speed into a 6 speed and keeps the rpms up when it shifts where the power band is. it can be shut off and on with a button on the shifter. they use them on dragsters and losts of drag cars. the rear end gear will depend on the size of tire i use and what i want that final gear to run at.

guys on the maverick forums are runnin a 4.10 rear gear and still cruise at 80mph with about 2500rpms. it really allows you get the entire low and high end the way it works. its expensive, but this is my fun car until i die so im going to make it exactly what i want it to be. maybe next year ill have it all together. still need to get disc brakes and rebuild the front end.