best cruising rpm

froggy

 
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I'd like to know what is the best highway rpm for a 1977 2F engine.Over 2000rpm, it gets very noisy inside :rolleyes: but I know the engine can take a lot more. But how much? I just don't want to blow my good ol' 2F

BTW 1971 FJ-40, 1977 2F, J30-3 speed t-c, 4.11 and 31''



thanks :beer:
 

brian

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top gear in the both the 3&4 speed trannies is 1:1. so you're good to 65-70mph ALL day, 75-80(if you're feeling lucky, or brave, or just stuid :) ) to pass or down long hills.

she would cruiser better with 33's and the 4:11's.
 

froggy

 
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A 4 speed (for first gear) and 35'' are my next move, but for now can I say that a few hours at 3000 rpm is not bad, even for a old engine ?
 

brian

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froggy said:
A 4 speed (for first gear) and 35'' are my next move, but for now can I say that a few hours at 3000 rpm is not bad, even for a old engine ?
if you go through the effort of the 4spd swap(although not hard), do it with an aussie 4spd in front of your 3spd transfer case.
some will say otherwise, but it is the best way, with all toyota parts.
 

RHINO

 
 
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what is that 4 replies and only one answer to your Q??? :rolleyes: :flipoff2:


me and my pig (2F) are very happy cruising at 2500rpm all day.

dont know about your 31's but my 36's and 4:10 gears translate like this:

2500rpm=63 MPH
3000rpm=74 MPH and noticeably less MPG
 

rabid

 
 
 
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Let me know if you need a 4 speed setup, you are not that far from me, and I can get my hands on one.

It will not help much until you get the larger tires.

3K is getting up there for an F motor. I did 5 years of highway driving, 5 hours each way at about 65 MPH on an f-135. You should be pretty comfotable with the 2F at around 70, but I don't think I would go much faster. Bigger tires will greatly reduce your RPM, and increase the longevity of your motor.
 
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The folks who I trust seem to say that 2800 to 3200 is the max cruising
RPM for an F or 2F that has not been rebuilt -- especially if the oil
pressure is low. I am the sort that wants to get the longest life out
of my engine -- not get to where I am going sooner. If you are
running stock tires, at around 30", 3000 rpm is probably equal to
60 mph with 4.10 gearing.

Remember the old ads that said that cruisers would run all day at
80 mph? That's quite a joke cause that only happens when the
engine is at redline (4000 r.p.m.). I can only stand a cruiser
engine at 4000 r.p.m. for about 5 seconds.
 
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I drive my junk all the time.
I am running an SM420, and 35" tires.

I usually 'Cruise on the freeway between 2800-3200 rpms (70-80mph accodring to the calculator) with runs up to 3500 rpm for passing.
 

PabloCruise

 
 
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I also recomend keeping an eye on the vitals - like oil pressure.

I recall Mark W saying the time to be careful is after cruising on the interstate and you put it in N to coast onto an off-ramp. Your oil pressure drops, and that is when your bearings are in danger...

So I guess it is better to coast down with it in gear.
 
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i cruise on the freeway at 2800 all day everyday. been known to cruise it at 3600 for 4 hours (well excluding fuel stops :))

had mine hit 5500 last night briefly. it's original engine, about 400 000 k's on it. yes i know i'll kill it.

when is what i'm waiting for
 

FJ40Jim

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froggy said:
I'd like to know what is the best highway rpm for a 1977 2F engine.Over 2000rpm, it gets very noisy inside :rolleyes: but I know the engine can take a lot more. But how much? I just don't want to blow my good ol' 2F
BTW 1971 FJ-40, 1977 2F, J30-3 speed t-c, 4.11 and 31''
The 2F engine makes peak torque at 1800RPM. That is also best BSFC. So 1800 would seem to be the best cruising RPM. But there is an unusual problem w/ a FJ40 compared to a conventional passenger car. It is shaped like a brick... pulling a small parachute.

As a SWAG, let's say it takes 60 road HP to go 60MPH. A typical out of tune 2F makes 200ft/lbs of torque@ 1800RPM. Plugging that into the HP formula gives 200ft/lb*1800RPM / 5252= 68HP. We need to deduct for drivetrain and other parasitic losses, so we can assume that only 80% of the crankshaft HP is actually getting to the pavement. That translates into 54HP @ 1800RPM at WOT and we need about 60HP to push our hypothetical FJ40 on the highway.

If it takes 60 HP to push the vehicle at a given speed and there is only 54HP available to do the work on the ground, the vehicle will not be able to achieve or maintain that speed.

If the vehicle in question were a Prius, which only needs 10 or 15HP to go 60MPH, then cruising at best BSFC would be no problem.

The best cruise RPM for an FJ40 is somehwere above best BSFC, that will allow the engine to generate sufficient HP to accomplish the work, and have some reserve power available. BSFC really goes downhill above 2800RPM, so somewhere around 2400 seems like a good target.
 

John Smith

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When I had 4:11s and 33s I was at 3000 rpm at 65mph and drove for 10 hours straight with no issues many times. I now I have 36s and I am around 2400 or 2500 at the same speed which is much nicer. I have my redline set at 3000 rpm on my tach. Yeah the engine will go over 3000 but it is working pretty hard.
 

froggy

 
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thanks for all your help. I will keep it between 2500 and 3000 rpm. I just can't think going over 3000rpm. I'm gonna be a deaf old fart when going 50 years old :D
Maybe the 4 speed tranny and t-case makes less noise. At least,I know I won't kill my old 2F




:beer:
 

brian

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froggy said:
Maybe the 4 speed tranny and t-case makes less noise. At least,I know I won't kill my old 2F




:beer:

nope, final drive is 1:1 on both the 3&4 spds.
 
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froggy said:
thanks for all your help. I will keep it between 2500 and 3000 rpm. I just can't think going over 3000rpm. I'm gonna be a deaf old fart when going 50 years old :D
Maybe the 4 speed tranny and t-case makes less noise. At least,I know I won't kill my old 2F




:beer:

Earplugs :)
 
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PabloCruise said:
I also recomend keeping an eye on the vitals - like oil pressure.

I recall Mark W saying the time to be careful is after cruising on the interstate and you put it in N to coast onto an off-ramp. Your oil pressure drops, and that is when your bearings are in danger...

So I guess it is better to coast down with it in gear.
who coasts out of gear? i was always beaten to a pulp by my old man for doing that... he said that if your motor and wheels weren't linked, you were no longer in control of the car. e.g. if you blow a front tire out you can't accellerate that little bit to keep it balanced, or if you require drive to correct a slide or something...
 
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