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General Forums => The Mess Hall => Topic started by: xtrm4xjp on December 31, 2005, 01:31:41 AM

Title: MPG's with larger tires
Post by: xtrm4xjp on December 31, 2005, 01:31:41 AM

I'm wondering what kind of mileage guys are getting out of ther 4 bangers with 33's or 35's.  I've got a 94 sitting in the shop and am contemplating swaping it into a wrangler I'm picking up.  I also have a 3.9L 4 cyl diesel in a CJ that I might pull to swap in it too.  Just trying to weight things up.  Thanks in advance.

Anders

Title: MPG's with larger tires
Post by: FourbangerYJ on December 31, 2005, 10:19:22 AM

I have not checked the exact milage on mine. I run 4.88's with 35 inch MT/R's. I get almost the same as my friends 4.0 I a guessing low teens. I keep the RPM's on the freeway around 3-3500K.

The 4BT sounds like alot of fun!! Heavy beast but it can make a ton of power. Did you need to beef up the frame? What axles are you running with it?

Title: MPG's with larger tires
Post by: SMC4WD on December 31, 2005, 10:25:35 AM

I'm also 4.88 with BFG 35" M/T's...  

I'll get between 12-15 mpg on a good day.  I've done alot of external performance upgrades to increase horsepower, but that decreases fuel ecomony.

Title: MPG's with larger tires
Post by: Jeffy on December 31, 2005, 11:17:29 AM

I get around 16-18mpg with 35's and 4.56's with speeds over 70mph and reving over 4000rpm.  I used to get as high as 25-27 when my Jeep had 32's, stock gears and I kept the speeds below 65mph and keeping it below 3700rpm.

Title: MPG's with larger tires
Post by: xtrm4xjp on December 31, 2005, 01:06:32 PM

Thanks guys.  Confirms what I was kind of thinking.  You need to run a higher RPM to get the performance which sacrifices MPG.

I actually don't have a Cummins motor, it's an Isuzu 3.9.  The designation is a 4BD1.  It is comparible to a Cummins in power.  I jsut happened to come across it for a good price.  It gets between 30-35 MPG.  I guess with that siad I'll be putting up an ad in the for sale section.  Thanks again for the help guys.

Anders

Title: MPG's with larger tires
Post by: xtrm4xjp on December 31, 2005, 09:15:59 PM

Quote from: "FourbangerYJ"

Did you need to beef up the frame? What axles are you running with it?

I could have but I didn't cause I knew if I liked it I would swap it into something else.  I'm currently running a GM 10 bolt in the front and GM 12 bolt in the rear.  With the stock 3.07 gears, SM 420 trans, 300 t-case and 36's it crawls surprisingly well.  Still in the test phase though.

Anders