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1998 Jeep Cheroke XJ Project Mileage Master Part III

Dyno
Pete Trasborg
| Brand Manager, Jp
Posted June 1, 2009

Cranking Up The Power And Increasing Mileage

In the last installment of Mileage Master, our '98 XJ, we added armor, skidplates, and recovery points front and rear so we could take it wheeling without killing vital components ("Project Mileage Master", Part II, October '08). Unfortunately, with the added weight we paid the piper in average mileage over a 5,000-mile test period.

So rather than remove the armor (some of which we'd welded to the body), we decided to try cranking up the power on our 4.0L engine by using some simple bolt-on power-adders. The theory is by making more power out of the same engine, it's more efficient. With everything else in the Jeep unchanged, that efficiency should translate directly to mpg.

But wait, there's more! We couldn't let the addition of a bunch of power adders go by without running them on the dyno to see what actual power numbers we made, as well as testing mileage gains.

While we could see instantly that we were making power thanks to the dyno, we didn't really see huge mileage gains. However, this is only the first part of the power adding tests and while we added a freer flowing muffler, the stock down pipe is still crushed in half (from the factory) and the stock catalytic converter has seen better days. Once we open it up more, we should see even bigger numbers in both mileage and power.

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Crank It Up
We didn't get back to stock mileage numbers with all this stuff, but we did make more power and find more fuel efficiency. Face it, if you are buying power adders and expecting them to pay for themselves, it isn't going to happen. But, we should be able to get back to stock mileage numbers and maybe even get better than stock mileage while having a Jeep that is much more capable off-road.

We went from a flat and level highway average mileage of 16 mpg back up to the 17-18 mpg we had been seeing when the Jeep was bone stock. One to two miles per gallon doesn't really seem like a good return on the parts invested, but we knew going into this we'd not see the parts pay for themselves. However, the Jeep is more enjoyable to drive and we are hoping that with the next round of power adders we'll see even better than stock mileage.

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Test Results

Test 1: Catback
Test 2: Catback and AEM Brute Force intake kit
Test 3: Catback, AEM Brute Force intake kit, and DUI ignition
Test 4: Catback, AEM Brute Force intake kit, DUI ignition, and Edge throttle body
Test 5: Catback, AEM Brute Force intake kit, DUI ignition, Edge throttle body, and Edge Trail Jammer

Engine Speed (RPM) Test 1 Test 2 Test 3 Test 4 Test 5
  HP Torque HP Torque HP Torque HP Torque HP Torque
3,000 99.4 174 105.1 184 99.4 174 108 189 112 196
3,{{{100}}} 100.3 170 106.2 180 111 188 110.4 187 113.9 193
3,{{{200}}} 104.8 172 107.8 177 112.1 184 116.4 191 117.6 193
3,{{{300}}} 106.2 169 113.7 181 115 183 120 191 120 191
3,400 108.1 167 115.9 179 117.8 182 121.7 188 123.6 191
3,500 112 168 117.3 176 125.3 188 123.3 185 128.6 193
3,{{{600}}} 114.5 167 120.6 176 127.5 186 127.5 186 130.9 191
3,700 116.9 166 124 176 128.9 183 129.6 184 134.6 191
3,800 120.8 167 126.6 175 131.7 182 136 188 136.7 189
3,{{{900}}} 122.5 165 130.7 176 133.7 180 138.1 186 141.8 191
4,000 126.4 166 132.5 174 139.4 183 138.6 182 143.2 188
4,100 127.2 163 134.3 172 140.5 180 140.5 180 144.4 185
4,200 131.2 {{{164}}} 136.7 171 140.7 176 142.3 178 145.5 182
4,300 130.2 159 138.4 169 141.6 173 144.1 176 147.4 180
4,400 130.7 156 139.9 167 142.4 170 144.1 172 146.6 175
4,500 131.9 154 139.7 163 142.2 166 143.9 168 146.5 171
4,600 131.4 150 139.3 159 141 161 142.8 163 145.4 166
4,700 131.5 147 139.6 156 139.6 156 141.4 158 144.1 161
4,800 131.6 144 139.8 153 138.9 152 138.9 152 143.5 157
4,900 129.7 139 137.1 147 137.1 147 137.1 147 141.8 152

Sources

Edge Products
Ogden, UT 84404
888-360-3343
www.edgeproducts.com
Performance Distributors
Memphis, TN 38132
901-396-5782
www.performancedistributors.com
Advanced Engine Management Inc (AEM)
aempower.com

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