Bronco Engine RPM Calculator (for specific tire sizes & axle ratios)

[RagnarKon]

So... I starting looking at tires I could put on my Bronco when it eventually (hopefully) gets here next year. I'm still debating between the Black Diamond and Badlands, which have different axle ratios. I was doing some math to figure out what the engine RPM would be at specific tire sizes & axle ratios....

...and then I got carried away and created this:

I've included all of the standard Bronco axle ratios, the transfer case ratios, transmissions, and available tire size.

Available for download off of Google Docs:

Excel | OpenDoc

I couldn't find any detailed dyno results for the Bronco, so I didn't pre-program the RPM details. But If I did have the dyno details, the color code would be this:

• Red - Undesired RPM. Typically either above red line or so low that the engine is likely to stall.
• Blue - Geared towards fuel economy
• Yellow - Geared towards power
• Green - The "sweet spot" between power and fuel economy

The plus side of my inability to find dyno details is now you can specify the RPMs details however you see fit. Which allows you, in effect, to create your own axle ratio chart.

If anyone notices any errors (mathematical or otherwise), please let me know.

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[North7]

Great job, thank you.

 

[johndeerefarmer]

So... I starting looking at tires I could put on my Bronco when it eventually (hopefully) gets here next year. I'm still debating between the Black Diamond and Badlands, which have different axle ratios. I was doing some math to figure out what the engine RPM would be at specific tire sizes & axle ratios....

...and then I got carried away and created this:

View attachment 160201

I've included all of the standard Bronco axle ratios, the transfer case ratios, transmissions, and available tire size.

Available for download off of Google Docs:

Web (Preview) | Excel | OpenDoc

I couldn't find any detailed dyno results for the Bronco, so I didn't pre-program the RPM details. But If I did have the dyno details, the color code would be this:

• Red - Undesired RPM. Typically either above red line or so low that the engine is likely to stall.
• Blue - Geared towards fuel economy
• Yellow - Geared towards power
• Green - The "sweet spot" between power and fuel economy

The plus side of my inability to find dyno details is now you can specify the RPMs details however you see fit. Which allows you, in effect, to create your own axle ratio chart.

If anyone notices any errors (mathematical or otherwise), please let me know.

Here are 5star tunings dyno results if you want to add them

https://www.bronco6g.com/forum/threads/five-star-tuning.21885/

 

[HPNQ420]

So... I starting looking at tires I could put on my Bronco when it eventually (hopefully) gets here next year. I'm still debating between the Black Diamond and Badlands, which have different axle ratios. I was doing some math to figure out what the engine RPM would be at specific tire sizes & axle ratios....

...and then I got carried away and created this:

If anyone notices any errors (mathematical or otherwise), please let me know.

Great work! Thank you.

 

[RagnarKon]

Here are 5star tunings dyno results if you want to add them

https://www.bronco6g.com/forum/threads/five-star-tuning.21885/

Do you know if they published the dyno result data anywhere?

Tried hunting around their site a bit and didn’t see anything.

EDIT: Never mind I’m blind apparently. No results for the Bronco specifically… but they do have the Ranger 2.3L results and the F-150 2.7L results published… so I might be able to do something there.

I’ll play around with it this afternoon.

 

[johndeerefarmer]

Do you know if they published the dyno result data anywhere?

Tried hunting around their site a bit and didn’t see anything.

EDIT: Never mind I’m blind apparently. No results for the Bronco specifically… but they do have the Ranger 2.3L results and the F-150 2.7L results published… so I might be able to do something there.

I’ll play around with it this afternoon.

from their Facebook page

 

[HoosierDaddy]

Not a graph, but a pretty advanced calculator nonetheless. This one will auto populate the automatic gear ratios, you'll have to fill out the manual gear set .... manually....

All kinds of options to play with if you're getting serious about driveline mods.

http://www.grimmjeeper.com/gears.html

 

[BostonSasquatch]

So... I starting looking at tires I could put on my Bronco when it eventually (hopefully) gets here next year. I'm still debating between the Black Diamond and Badlands, which have different axle ratios. I was doing some math to figure out what the engine RPM would be at specific tire sizes & axle ratios....

...and then I got carried away and created this:

View attachment 160201

I've included all of the standard Bronco axle ratios, the transfer case ratios, transmissions, and available tire size.

Available for download off of Google Docs:

Web (Preview) | Excel | OpenDoc

I couldn't find any detailed dyno results for the Bronco, so I didn't pre-program the RPM details. But If I did have the dyno details, the color code would be this:

• Red - Undesired RPM. Typically either above red line or so low that the engine is likely to stall.
• Blue - Geared towards fuel economy
• Yellow - Geared towards power
• Green - The "sweet spot" between power and fuel economy

The plus side of my inability to find dyno details is now you can specify the RPMs details however you see fit. Which allows you, in effect, to create your own axle ratio chart.

If anyone notices any errors (mathematical or otherwise), please let me know.

I'm nominating you Bronco6G Official Nerd !

 

[PG_Bronco]

I just put some badlands wheels and tires (ko2) on my 4.27 OBX. I am a fan so far but have noticed A BIG decline in acceleration power (quickness). Any feedback or recommendations would be greatly appreciated! 2.7L

 

[refade1]

I just put some badlands wheels and tires (ko2) on my 4.27 OBX. I am a fan so far but have noticed A BIG decline in acceleration power (quickness). Any feedback or recommendations would be greatly appreciated! 2.7L

I did the same but on a 3.73 base bronco 2.3L seems to be fine for me

 

[Fmuguira]

Having the rpm numbers subject to the R&P gear ratio, tire height and transmission ratios is a part of the solution, estimate of how performance will be but you can’t discount wheel/tire weight.

Two vehicles with identical drive ratio, same vehicle weight and same engine with same torque and horsepower curves will perform differently if one has a 100 pound tire/wheel combination and the other has an 80 pound tire/wheel.

Look at some of the super cars wheel weights (and costs for a wheel)!!

 

[Fmuguira]

To expand a bit, Porsche claims 1 pound of reduced wheel/tire weight is equivalent to reducing 7 pounds of vehicle/body weight

Based on this 1-7 ratio then a 20 pound heavier wheel/tire combo as I mentioned above would be 20x4=80 pounds and then applying the 1-7 ratio would say those heavier wheels/tires would be like having 560 more overall weight in your vehicle. That’s huge !!!

 

[PG_Bronco]

To expand a bit, Porsche claims 1 pound of reduced wheel/tire weight is equivalent to reducing 7 pounds of vehicle/body weight

Based on this 1-7 ratio then a 20 pound heavier wheel/tire combo as I mentioned above would be 20x4=80 pounds and then applying the 1-7 ratio would say those heavier wheels/tires would be like having 560 more overall weight in your vehicle. That’s huge !!!

Thank you very much for this! I’ll admit, the main reason I switched to the tires and wheels was for the look. I was not a fan of the OBX look. I am hoping to get off road but the main purpose is my daily driver. I just traded in my ‘21 BB 3.73 2.7, I kept it stock because I didn’t mind those wheels and tires. Would you suggest with those details that I should try to find a lighter option?

 

[mpeugeot]

I just put some badlands wheels and tires (ko2) on my 4.27 OBX. I am a fan so far but have noticed A BIG decline in acceleration power (quickness). Any feedback or recommendations would be greatly appreciated! 2.7L

The stock OBX rim and tire combo is very light and going to anything else will be noticeable. Even the Black Diamond rims and tires are way heavier.

I wouldn't go as far as calling it a BIG decline in acceleration, but certainly noticeable. Significant decrease in fuel economy is another thing that you will notice.

Off-road, you are going to want those heavier rims and tires. I have a set of stock OBX rims/tires for commuting and I have 2 sets of off-road rims and tires.

Changes the look dramatically.

 

[mpeugeot]

So... I starting looking at tires I could put on my Bronco when it eventually (hopefully) gets here next year. I'm still debating between the Black Diamond and Badlands, which have different axle ratios. I was doing some math to figure out what the engine RPM would be at specific tire sizes & axle ratios....

...and then I got carried away and created this:

View attachment 160201

I've included all of the standard Bronco axle ratios, the transfer case ratios, transmissions, and available tire size.

Available for download off of Google Docs:

Web (Preview) | Excel | OpenDoc

I couldn't find any detailed dyno results for the Bronco, so I didn't pre-program the RPM details. But If I did have the dyno details, the color code would be this:

• Red - Undesired RPM. Typically either above red line or so low that the engine is likely to stall.
• Blue - Geared towards fuel economy
• Yellow - Geared towards power
• Green - The "sweet spot" between power and fuel economy

The plus side of my inability to find dyno details is now you can specify the RPMs details however you see fit. Which allows you, in effect, to create your own axle ratio chart.

If anyone notices any errors (mathematical or otherwise), please let me know.

Well Ford used a target of 2950 rpm (+/- 50). I know that because if you look at gear vs tire size, you end up with most of the vehicles running very close to that based on the tire size of a given trim and the gears installed. This also coincidentally puts the engine right on the beginning of the torque peak.

Non-sasquatch Badlands is the right answer.

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