Is 5th gear gutless uphill with every 4.0?

[AllanD]

I had an 84 Turbo Coupe Thunderbird.
It would come up the Cajon Pass in 5th gear at 80mph.

Yeah, but Cajon Pass is only 4000-something feet.
(Ok, you made me look it up 4180ft)

Try it going over Loveland Pass which is nearly three
times as high (11,980ft) (US-6 in Colorado)




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[Thumper113]

If I had wanted to push 4th over 3000 rpm I could have held over 110 kph, as it was I held 100 kph in 4th @2800 rpm.

I run my 4.0 over 4000 rpm quite alot here cause the mountain passes range from 9000 ft to 11900 ft (I live at 6000 ft) with grades up to 9%, most long grades are 4-6% though. 5th gear is useless in those places if you wanna keep up with traffic. Hasn't hurt it in the 7 years I've been doing that.

Change your oil regularly & keep the level full & keep your cooling system in tip-top shapes & you can twist 4000+ rpm's all day long without worrying about anything except the gas gauge dropping faster than it normaly does (provided your engine was taken care of by previous owners(s) ).

 

[almostclueless]

Change your oil regularly & keep the level full & keep your cooling system in tip-top shapes & you can twist 4000+ rpm's all day long without worrying about anything except the gas gauge dropping faster than it normaly does

Aside from the inescapable fact that every revolution of an engine is another toward the engine wearing out. Sure, startup contributes to wear, but so does just running the engine.


Oh, BTW......the vibrational and inertial loads on the engine parts increases as a function of the square of the RPM increase. Pistons and connecting rods have to change directions in a very short time. Now, not only multiply that by 33 to 50 percent due to the RPMs you say an engine can turn all day long, but also increase the velocity change for every engine part that basically moves back and forth in almost a straight line.


These are trucks, not 250cc GP works bikes.

 

[MAKG]

almostclueless, you're forgetting about the lubrication system. Which works a whole lot better when you spin the F out of it.

The coefficient of friction is LOWER at high RPM. You're assuming it's the same.

 

[Thumper113]

Aside from the inescapable fact that every revolution of an engine is another toward the engine wearing out. Sure, startup contributes to wear, but so does just running the engine.


Oh, BTW......the vibrational and inertial loads on the engine parts increases as a function of the square of the RPM increase. Pistons and connecting rods have to change directions in a very short time. Now, not only multiply that by 33 to 50 percent due to the RPMs you say an engine can turn all day long, but also increase the velocity change for every engine part that basically moves back and forth in almost a straight line.


These are trucks, not 250cc GP works bikes.

Thanks for interpreting the "all day long" as being "literal", when it's usually taken as an "expression". I must admit, I haven't driven my truck "all day long at 4000 rpm" because I don't drive my truck all day long. I don't think I could handle driving for 24 hours straight. So yeah, I was wrong in saying it could be done all day long. Although most other folks probably knew what I was getting at when I made that comment.

Of course it's not a 250cc GP with very low (by comparisonof a 4.0) reciprocating weight. That doesn't mean a 4.0 that's in good shape to start with will have it's life cut drastically short by running at 4000 rpm's for a mile or two at a time on numerous occasions during a long drive when climbing mountain passes in a lower gear to maintain the speed limit. My 4.0 (that's what I'm using as the example) has lived through it so far in the last 7 years from 74K miles when I bought it to it's current 169K miles. The only thing I've replaced on the engine (other than general, normal, maintenance items) because of a failure in all those miles has been the fan clutch. I suppose I'm pretty lucky then. If the engine fails me now, I'll fix it & go on with life.

 

[almostclueless]

almostclueless, you're forgetting about the lubrication system. Which works a whole lot better when you spin the F out of it.

The coefficient of friction is LOWER at high RPM. You're assuming it's the same.

No amigo....I was referring to what I could generalize as vibrational and inertial loads, such as;

http://en.wikipedia.org/wiki/Engine_balance


As for the oil pumps, if I'm not mistaken they're all gerotor configurations that will supply a stock engine proportionally throughout any reasonable engine speed.

 

[AllanD]

That's nice but generalizations from a wiki page is hardly relevant.

Do you need to worry about a 4.0 engine that spinning faster than
you NORMALLY drive it?
No, because you aren't outside the "envelope" that the engineers
who designed it, balanced the engine for.

And in point of fact you cannot spin a 4.0 to dammaging rpm's because
it's computer management simply will not allow it.

Will a 4.0 spun to 4000rpm for several minutes each day on a daily basis
climbing mountain passes wear out faster than one that isn't? Absolutely!

Will it wear out faster than one that is perpetually lugged by
some idiot that doesn't bother to get the engine spinning fast
enough to devlop full oil pressure? No.

Do what you have to do and don't waste time worrying about things you cannot control.

The point about bringing up the oil pump yes they are gearotor designs that will develop pressure and volume proportionally as rpm increases.
The POINT is the engine's NEED for oil pressure is simply not
met until 1700-2000rpm and pump relief pressure is rarely reached
before 3000-3200rpm.

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[MAKG]

Yes, the pumps are. But the oil doesn't flow the same way at all RPMs.

It IS true that the engine will wear faster at higher RPM than lower (IF it isn't lugged), but honestly, these days it takes hundreds of thousands of miles to do that even with the high revs. Virtually all engines get done in by collisions or screw ups before then (e.g., exploding radiator hose at just the wrong time).

You can also do MASSIVELY more damage from a single overheating event than you will do from a lifetime of 4000 RPM revs.

So, while it may be a true statement, it's not anywhere near as useful as it sounds.

 

[Kona]

There is NOTHING ON GOD'S GREEN EARTH to prevent you from "pushing" your engine over 3000 RPM. Even my big stupid 1972 250 inline 6 is very happy there (this is the one that idles at 400 RPM and makes good torque at 800 RPM), and that's even what one does routinely to get this thing to 70 MPH on the highway.

I wish I understood why anyone thought that was a problem.

Run your 4.0L right up to the redline if you want. It won't brake ANYTHING even if you do it for hours.

I don't think it is a problem, I just was not in a hurry enough to make it noisier and burn a bit more gas for 10- 20 kph!

 

[High Desert Ranger]

Yeah, but Cajon Pass is only 4000-something feet.
(Ok, you made me look it up 4180ft)

Try it going over Loveland Pass which is nearly three
times as high (11,980ft) (US-6 in Colorado)

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Perhaps if I get the money to fix the body damage and broken windows from having the car parked in an area where someone else's kids can find rocks.

But from my time spent randomly working on the car, I know that it had what a lot of car of it's time did not have, A Barometric Pressure Sensor. I wonder how useful that would be on the Loveland PAss.

 

[MAKG]

But from my time spent randomly working on the car, I know that it had what a lot of car of it's time did not have, A Barometric Pressure Sensor. I wonder how useful that would be on the Loveland PAss.

Marginally useful at best. It means that for speed density systems (which doesn't include the 4.0L), you can calibrate the MAP sensor dynamically, instead of waiting for WOT or a restart. For a MAF-based system, it's redundancy. Under nominal conditions, it doesn't do anything. It only helps detect off-nominal conditions such as a fouled MAF.

I think you know this, but a BARO is just a MAP sensor open to the outside instead of the intake manifold. It's not unusual to see the two sensors combined into a MAP/BARO with two ports.

Loveland Pass is a challenge for any vehicle, but it's many times worse when the driver emasculates it by insisting on the same RPMs. I made it over that at full highway speed (70 MPH) in a Bronco II with an over-200K-miles 2.9L. I just had to be comfortable with doing it in 3rd gear. It survived just fine, and went on to pin the speedometer later on I-25 (still at 6000 feet....).

When that 2.9L died, it wasn't due to the bottom end (it ate its camshaft). It still had good compression and bright silver bearings right before it died, and might have made it another 250K miles, according to its then-owner, if he wanted to go through the trouble of replacing the camshaft. Instead, he put another engine in there (a V8, I believe).

 

[MAKG]

I don't think it is a problem, I just was not in a hurry enough to make it noisier and burn a bit more gas for 10- 20 kph!

Unless you have it floored, it won't burn more fuel. If you have it floored in the higher gear, it may burn less.

 

[AllanD]

Marginally useful at best. It means that for speed density systems (which doesn't include the 4.0L), you can calibrate the MAP sensor dynamically, instead of waiting for WOT or a restart. For a MAF-based system, it's redundancy. Under nominal conditions, it doesn't do anything. It only helps detect off-nominal conditions such as a fouled MAF.

I think you know this, but a BARO is just a MAP sensor open to the outside instead of the intake manifold. It's not unusual to see the two sensors combined into a MAP/BARO with two ports.

Loveland Pass is a challenge for any vehicle, but it's many times worse when the driver emasculates it by insisting on the same RPMs. I made it over that at full highway speed (70 MPH) in a Bronco II with an over-200K-miles 2.9L. I just had to be comfortable with doing it in 3rd gear. It survived just fine, and went on to pin the speedometer later on I-25 (still at 6000 feet....).

When that 2.9L died, it wasn't due to the bottom end (it ate its camshaft). It still had good compression and bright silver bearings right before it died, and might have made it another 250K miles, according to its then-owner, if he wanted to go through the trouble of replacing the camshaft. Instead, he put another engine in there (a V8, I believe).

Mike he's talking about a BAP on a 1984 Thunderbird turbocoupe.
Turbocoupes didn't have MAF, they had a mechanical VaneAirMeter.

But it's all irrelevant because the ford training manual I have on
the 2.3turbo engine clearly states that the computer only "looks"
at the BAP's data at engine startup, but yes, it was only to give a quick calibration reference for the air meter.

It really won't have any effect on altitude compensation.

that being said I will say that an '84 T'bird was an "early" 2.3Turbo and thus probably didn't have a boost control solenoid that would increase the boost
beyond the mechanical setting of the wastegate actuator (all bets are off if he modified the engine with a boost control) and while that may seem to "limit" the engine, that particular turbocharger a Garret T-03 with
a 60trim .62A/R compressor housing and (probably a .48A/R turbine housing)
is EASILY capable of maintaining 12psi to 19,000feet or so
and factory boost on an '83-84 turbocoupe was only 8psi....

So yeah, even loveland pass wouldn't present a challenge even to a 160hp thunderbird turbocoupe, it'll probably make that long climb up US-6 to the scenic overlook like a homesick angel racing home from hell.

while a 5.0 Mustang would be left wheezing behind you.

At high elevation there is no ammount of displacement that'll keep up with even modest forced induction.

Now, to make a trip out there with my old (highly modified) Saab.

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[Will]

Another reason to make sure you downshift is that you definately don't want to get the pedal down far enough that the TPS sends a wide-open-throttle signal to the computer. Your engine is meant to run like that for 10 or so seconds probably but I could see the catalytic converter setting your carpet on fire or something after 5 minutes.

Having an exhaust temperature sensor on my truck I'm very concious of torque. I don't know how exactly a gas motor follows this but it's got to be similar. If you are running more torque, you have more cylinder pressure and heat and the parts are all deforming more. When you downshift and speed the motor up by downshifting into 3rd from 4th, the rpm goes from 2800 to about 3600 and that seems bad. But in reality, you are also asking 30% less torque from the motor so the heat, pressure and load on parts goes way down. They deform less receiving fewer high-stress cycles.

Goes back to my time in the artillery. You automatically discard a cannon tube after a certain number of Effective Full Charges. Say a tube is rated to 1,000 EFCs. A maximum charge is one EFC. If you fire 1,000 of them, the tube is done. The metal is fatigued enough to not be trusted anymore. If you fire the minimum charge you could fire 100,000 shells before the tube was condemned. Even cutting the charge by a small increment greatly increases it's life.

An engine is no different. At maximum torque you are doing a lot more wear on it than at maximum rpm.

 

[AllanD]

Ahhhh... I remember getting an arguement long ago when I told someone that the
very defination of Torque and horsepower peak could most simply be expresses in
terms of airflow....

The torque peak is quite simply the rpm at which the engine moves
the greatest ammount of air PER CYCLE
The power peak is the rpm at which the air moves the greatest
ammount of air per MINUTE.


So while centrifugal forces acting against the recriprocating parts increases with the square of speed, thermal stresses are greater on the pistons. valves etc near the torque peak, because that is when you have the hottest, most forceful flame.

I agree with what Will says, and will expand on it....Spinning the engine faster at part throttle GREATLY reduces strain on the internal parts over WOT at lower rpm.

"High" rpm in a 4.0 is a really relative thing, a 4.0 OHV is doing all it is
capable of doing at 4200rpm (it's power peak), but that is particularly SLOW
for gasoline engines in general.

Hell I used to have a diesel that made peak power at 4400rpm!

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