Can someone compare their RPM/mph

[cmattina]

I have myself a 1993 4x4 5speed Ranger Sport

Someone made a comment in an older post that he is reving at 2500 going 70-75mph. I find that I am at 2100-2300 going 55mph, and about 2500 going 60-65 at best. I've also been getting pretty bad fuel economy (18-19mpg 25% highway).

One thing is a previous owner put some gayass cold air intake thing on it, so maybe that could be part of it. But there is a new filter on it and freshly cleaned MAF. And the previous owner changed the thermostate to one slightly cooler. Also, it is a 4x4 is going to add a bit of drag, but I have manual locking hubs, and I am speaking about when the hubs are free.

Regardless, how do those specs compare to your's?

 

[UrbanRedneckKid]

Sounds like a gearing problem. What gears are in your axles?

Mine does 3000rpm @ 70mph, but I've got 5.14 gears.

And no, there is no link to the intake or thermostat or 4wd, to this issue.

 

[scotts90ranger]

It's more of a tire question than gearing as all 4x4 2.3L Rangers came with 4.10's...

With my truck stock 4x4 on 31" tires I got a consistent 19mpg pretty much no matter what I did. But that engine was a little tired with one cylinder being low on compression, it was doing 23mpg right before that when it was 4x2 on 28" tires with 3.73 gears.

To estimate engine speed versus a tire diameter at different gear ratios go HERE and use the 4.11 line to get the driveshaft rpm which will be the engine speed in 4th gear, multiply by .79 to get the engine speed in 5th gear.

For the record, when I was still N/A with 31's it did the best in 4th gear at anything below 55

 

[cmattina]

It's more of a tire question than gearing as all 4x4 2.3L Rangers came with 4.10's...

With my truck stock 4x4 on 31" tires I got a consistent 19mpg pretty much no matter what I did. But that engine was a little tired with one cylinder being low on compression, it was doing 23mpg right before that when it was 4x2 on 28" tires with 3.73 gears.

To estimate engine speed versus a tire diameter at different gear ratios go HERE and use the 4.11 line to get the driveshaft rpm which will be the engine speed in 4th gear, multiply by .79 to get the engine speed in 5th gear.

For the record, when I was still N/A with 31's it did the best in 4th gear at anything below 55

I can definitely imagine my engine being tired for that matter with 185 000 miles. And I have stock tire size. I remember hearing 4:10 for the gearing. So, by using that website, I can find out the "proper" engine speed?

 

[cmattina]

Okkaaayyy. So after reading that chart, I am pretty close to those specs.
I have 28" tires. So, with 4:10 gearing, I am in the red (towing). So if i want better fuel economy, as I do very little towing, and use it as a daily, should I think about changing my gearing to 3:55 or 3:73?

 

[UrbanRedneckKid]

Put some 31"s on it, with a 2" leveling kit.

 

[adsm08]

You can't just compare two vehicles like that. Transmission, gearing, and tire size all make differences in the relationship of the two numbers, and without having all of those be the same any comparison made between the relationship of MPH and RPM is a worthless number.

I would use a metaphor that I read in a book once. "It's like comparing apples and trout".

 

[scotts90ranger]

Comparing a 2.3L 5 speed Ranger to a 2.3L 5 speed Ranger is a pretty accurate comparison, true one was a '89 and one a '93 but same transmission, same gear ratios, my tires were a little taller, his engine has a little more power and sophistication (no MAF on mine).

No lift needed for 31's on a '93, I was running 31's on my '90.

For starters, what kind of gas mileage are you getting, and how does it compare to the 19 I was getting? Depending on how it's doing now and what you do with the truck change what I might say... The chart more references V6 engines that have a little more low end torque, the 2.3L isn't gutless but it's still a 4 cylinder... These engines like to be in the 2500-3000rpm range for decent driveability. If I remember right (my tach hasn't worked for a few years...) my truck was running 2500-2600rpm at 55mph in 5th gear, a hair under 3000rpm at the same speed in 4th gear which is why I cruised in 4th at that speed, it didn't like to hold 55 in 5th unless it was flat ground.

 

[UrbanRedneckKid]

No lift needed for 31's on a '93, I was running 31's on my '90.

True. But they look dumb without being leveled.

 

[kimcrwbr1]

Have you checked your speedometer with a gps or even have someone follow you and compare. If you have bigger tires without changing the speedo gear you moving faster than what your speedo is saying. The less you press on the skinny pedal the better the gas mileage. Especially with a four cyl you need to regear for larger tires to bring the Rs up in the power band?

 

[kimcrwbr1]

Did you reset the computer when you cleaned the MAF. Disconnect the battery for 1/2 an hour to set new values on the computer may help also?

 

[RonD]

A gas engine gets it's best economy and lubrication when engine coolant is at 200deg-220deg.
All motor oil "weight" is rated at 212deg.
Running an engine cooler is not "better for the engine", quite the opposite, oil is thicker and carbon build up is more likely.

Put back in the 192deg or 195deg thermostat, if you want the best MPG for your engine model.

The different intake is probably why the person switched t-stats, it is a bit of a trick sellers of air filters and intakes do.
An intake or filter won't do much unless you can change parameters of the air/fuel mix.
On computer controlled engines this is not easy to do.
So intake sellers often "recommend" a colder t-stat.
This lowers the average engine temp so lowers the incoming air temp, cooler air is more dense so computer will add more fuel.
You get more power, but there goes the MPG.

You also may have a computer temp sensor starting to go out.
Fuel injected engines can not have a standard "Choke" setup, no jets.
So they use a temp sensor, the computer is told by a sensor if engine is cold, it then runs engine rich and advances the timing, like a choke did, until the engine warms up, this is called an ECT sensor(engine coolant temp), it is a two wire sensor often located near the one wire sensor used for the dash board temp gauge.

Good info here on the ECT
http://oldfuelinjection.com/?p=28

If the ECT is acting up engine could be running rich more often or longer than it should.
Getting the correct t-stat back in may change that.