Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

NV6R · 07-26-2012, 08:13 AM

My '96 Jeep XJ 4X4, with a 4.0l has cracked 30mpg; actually, a best of 30.16mpg. This mileage was GPS confirmed, so I know it to be 100% accurate. This was before I did a lift (4"), a winch, winch bumper, and added a set of 235/75R15 Hercules Terra-Trac tires. When I achieved the 30.16mpg I was running a 1.5" lift (surprisingly, didn't seem to harm the MPGs), 235/75R15s Michelin LTX MS2s, and an AX-15 manual.

Oh, I also have some other mods that you may be interested in: I am running Dodge Neon injectors (703s), a full-length header, and changed my gearing from 3.07:1 to 3.55:1. The gearing has helped the mileage, since it is now in a happier stop when cruising.

With the XJ and it's aerodynamics, any speed beyond 65mph is going to make you lose MPGs, but when in overdrive the engine is WAY out of it's TQ band at that speed, so you will lose MPGs this way, too. Now, with the full-length header and the Neon injectors, the TQ band is considerably lower than it was stock, so the engine is more efficient at a lower RPM, and this is also helpful in another way: the AX-15 is most efficient at around 2000RPMs; my TQ peak with the header is now around 2300RPMs, so they sync up pretty good.

Now, with the lift and other stuff, I am lucky to get 22mpg -- 18mpg highway most of time. The thing is, my city MPGs aren't much different, so this is telling me my aerodynamics are screwy. When I put the winch bumper on, I had to remove the stock air-dam, and I think that REALLY killed my MPGs. I am designing a front air-dam to hang below the bumper, and this should bring back some of my MPGs. I am going to design it to where I can take it off when I go off-road, and have it mount to the roof for storage. I'll post pics when I get it done.

07-26-2012, 08:13 AM	#250 (permalink)
NV6R EcoModding Lurker Join Date: Sep 2011 Location: United States Posts: 3 Thanks: 0 Thanked 2 Times in 2 Posts	My '96 Jeep XJ 4X4, with a 4.0l has cracked 30mpg; actually, a best of 30.16mpg. This mileage was GPS confirmed, so I know it to be 100% accurate. This was before I did a lift (4"), a winch, winch bumper, and added a set of 235/75R15 Hercules Terra-Trac tires. When I achieved the 30.16mpg I was running a 1.5" lift (surprisingly, didn't seem to harm the MPGs), 235/75R15s Michelin LTX MS2s, and an AX-15 manual. Oh, I also have some other mods that you may be interested in: I am running Dodge Neon injectors (703s), a full-length header, and changed my gearing from 3.07:1 to 3.55:1. The gearing has helped the mileage, since it is now in a happier stop when cruising. With the XJ and it's aerodynamics, any speed beyond 65mph is going to make you lose MPGs, but when in overdrive the engine is WAY out of it's TQ band at that speed, so you will lose MPGs this way, too. Now, with the full-length header and the Neon injectors, the TQ band is considerably lower than it was stock, so the engine is more efficient at a lower RPM, and this is also helpful in another way: the AX-15 is most efficient at around 2000RPMs; my TQ peak with the header is now around 2300RPMs, so they sync up pretty good. Now, with the lift and other stuff, I am lucky to get 22mpg -- 18mpg highway most of time. The thing is, my city MPGs aren't much different, so this is telling me my aerodynamics are screwy. When I put the winch bumper on, I had to remove the stock air-dam, and I think that REALLY killed my MPGs. I am designing a front air-dam to hang below the bumper, and this should bring back some of my MPGs. I am going to design it to where I can take it off when I go off-road, and have it mount to the roof for storage. I'll post pics when I get it done.