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DOHC - 2.3L Duratec / Mazda L Engines Discussions and Topics specific to the Duratec 4 cylinder engines

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Old 08-01-2015
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RPM 2.3l

When im driving 60 mph plus my rpms stay about 2500-2700 and on. So on long trips on the freeway my truck wastes alot of gas. Is this normal for a 2.3?
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Old 08-01-2015
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What kind of transmission?

Do you have stock tires?

What rear axle ratio do you have?

For stock tires size and axle ratio look here: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes

That info is on the driver's door sticker


Most newer transmissions are 5-speeds, manual or automatic

4th gear is a 1:1 ratio with engine RPMs, so if engine is spinning at 2,700RPM then rear drive shaft is spinning at 2,700RPM

5th gear is an "overdrive gear"(OD), usually about .75:1, so engine RPMs are lower than drive shaft RPMs.


So lets say you have stock tires(27" tall), 3.73 rear axle gearing

In 4th gear at 60MPH your RPMs would be 2,785rpms
In 5th gear at 60MPH your RPMs would be 2,089rpms

So if you have an automatic maybe it isn't shifting to 5th gear(OD).
On some automatics you can lock out OD, when driving up hills or pulling a trailer you really don't want trans to shift into OD, you lose engine torque to maintain speed under load, so maybe you just need to "push a button" to get OD back.

This has nothing to do with engine size, it is just the physics of gearing

Last edited by RonD; 08-01-2015 at 08:49 PM.
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Old 08-02-2015
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Quote:
Originally Posted by RonD View Post
What kind of transmission?

Do you have stock tires?

What rear axle ratio do you have?

For stock tires size and axle ratio look here: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes

That info is on the driver's door sticker


Most newer transmissions are 5-speeds, manual or automatic

4th gear is a 1:1 ratio with engine RPMs, so if engine is spinning at 2,700RPM then rear drive shaft is spinning at 2,700RPM

5th gear is an "overdrive gear"(OD), usually about .75:1, so engine RPMs are lower than drive shaft RPMs.


So lets say you have stock tires(27" tall), 3.73 rear axle gearing

In 4th gear at 60MPH your RPMs would be 2,785rpms
In 5th gear at 60MPH your RPMs would be 2,089rpms

So if you have an automatic maybe it isn't shifting to 5th gear(OD).
On some automatics you can lock out OD, when driving up hills or pulling a trailer you really don't want trans to shift into OD, you lose engine torque to maintain speed under load, so maybe you just need to "push a button" to get OD back.

This has nothing to do with engine size, it is just the physics of gearing
Thanks for the info. Its an automatic 5 speed the axle is 4.10. Does it sound correct with the info i gave on my rpms? Im not sure how to calculate. Ill try the OD tomorrow on the freeway.
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Old 08-02-2015
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4.10 ratio is for better pulling power(towing) and acceleration, not for MPG and highway driving
Which is odd since most 4 cylinder Rangers had 3.73 or lower ratios because people buying a 4 cylinder truck(or any vehicle really) were doing so because of MPG not better towing or acceleration, lol.
The lower the rear axle ratio the lower the RPM at highway speeds, but you also have less pulling power and acceleration at lower speed, so it is always a trade off.

4.10 ratio
27" tires
4th gear (1:1)
60mph
3,000RPMs

5th gear(OD)
2,300RPM

If you had 26" tires
4th gear
3,200rpm

5th gear
2,400rpm

So yes, you are probably running 26" tires and in OD(5th gear) at 60MPH you should be at 2,400rpm


You have the 2.3l DOHC Mazda L Duratec engine in the '06 Ranger, which is a high RPM engine, 143 horse power but at 5,200RPM, and highest torque 154ft/lb at 3,750RPMs
Which might explain the 4.10 axle ratio, it could be gutless as heck under 2,200 RPMs, so 3.73 axle would probably not work very well, in 5th gear even a slight uphill grade would require shifting into 4th because there would be no torque or HP to maintain speed.

Last edited by RonD; 08-02-2015 at 02:05 PM.
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Old 08-03-2015
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Quote:
Originally Posted by RonD View Post
4.10 ratio is for better pulling power(towing) and acceleration, not for MPG and highway driving
Which is odd since most 4 cylinder Rangers had 3.73 or lower ratios because people buying a 4 cylinder truck(or any vehicle really) were doing so because of MPG not better towing or acceleration, lol.
The lower the rear axle ratio the lower the RPM at highway speeds, but you also have less pulling power and acceleration at lower speed, so it is always a trade off.

4.10 ratio
27" tires
4th gear (1:1)
60mph
3,000RPMs

5th gear(OD)
2,300RPM

If you had 26" tires
4th gear
3,200rpm

5th gear
2,400rpm

So yes, you are probably running 26" tires and in OD(5th gear) at 60MPH you should be at 2,400rpm


You have the 2.3l DOHC Mazda L Duratec engine in the '06 Ranger, which is a high RPM engine, 143 horse power but at 5,200RPM, and highest torque 154ft/lb at 3,750RPMs
Which might explain the 4.10 axle ratio, it could be gutless as heck under 2,200 RPMs, so 3.73 axle would probably not work very well, in 5th gear even a slight uphill grade would require shifting into 4th because there would be no torque or HP to maintain speed.
Ok i understand now. I think im gnna start pulling a 4 horse trailer since it was made to haul haha. I appreciate your input. All the info was useful. Thank you.
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