Hot air or cold air better for mileage?

[Super mud]

I thought engines were more efficient at WOT?

Lol

Also, read an article stating that accelerating to your cruising speed a little quicker is better for your mpgs because you reach a better gear ratio quicker.

I always wondered that. Newer cars seem to rev so much through the gears even with light throttle.

The reduction of combustion temp allows leaner mixtures which saves fuel. Also, the exhaust displaces fresh incoming charge and fuel necessary to maintain safe A/F ratio. the more Egr that can be introduced the greater fuel savings. Of course this is only feasible at high vacuum/light load which is why Egr is regulated by intake vacuum.

My EGR hasn't been working from what I can tell and have been debating on fixing it. I plan to modify the Map sensor voltage to run leaner and this sounds to offer some benefit to maintaining a good mixture.

Anyone ever use a "Colo(u)r Tune" on a 4.0 to check the mixture? My dads Triumph came with one. Haven't checked the thread size yet but the engine has SAE fasteners but saw somewhere the spark plug was metric.

 

[Bdiddy11]

I've been keeping track of my MPGs a little more by using a bluetooth OBDII and the Torque app for Android. What have I noticed so far?

This is being done using my 97 auto, UpCountry suspension package, somewhat recent tune-up, 235 tires, needs a new TPS, downstream O2 sensor and the exhaust welded up fully.

Driving from 0-15MPH I'm getting between 3-8MPG. At around 20MPH it moves up towards around 10. From 25-35 it moves up between 12-15ish. Because of my failing TPS, my throttle randomly spikes in RPMS and doesn't shift properly (RPMs go higher than normal before it shifts)

I have noticed my best MPG between 30-40MPH when the RPMS are in the 1100-1500RPM range. Once my RPMS go above 1550 doing 35+, my MPG drops by almost 2. When the throttle is between the above stated RPMS I get between 14.7-18 MPG in town. On the freeway when I stick it in cruise, RPMS about 2100 I typically get 15.8-17.6 MPG.

I'm excited to see the #'s change when my TPS and O2 sensor get here. Seeing these results makes me wonder if it would be better to start up faster from a stop to get up to speed and not granny pedal it off the line. The other thing I've noticed is the more that you're able to cruise to a stop, the better the mileage. At higher speeds I was getting up to 50+MPG by cruising to a stop, and around town typically 27+MPG cruising to a stop.

Once I've got my exhaust system all together and hopefully giving me the proper MPGs that it should, I'm going to collect more data as I'm interested in doing a 99 intake mod + IAT relocation and the cowl snorkle ("forced" cold air) mods to see if that helps any with regards to MPG.

I'm hoping that those mods would at least yield a 1-2MPG increase...*crosses fingers*

 

[Root Moose]

Yeah, driving style makes a huge difference to getting MPGs out of these trucks. With my stocker I was able to eek out 20 mpg average:

http://www.fuelly.com/driver/reece146/cherokee-2

I didn't do anything special other than apply the hypermiling techniques that aren't a pain in the ass to other drivers or downright dangerous.

I stopped logging when the Jeep blew it's 0331 head. I haven't gotten around to fixing it and have been driving my big Jeep since.

 

[bigalpha]

Seeing these results makes me wonder if it would be better to start up faster from a stop to get up to speed and not granny pedal it off the line.

This is definitely true. If you accelerate slightly faster, it puts you into the gearing that's more effecient, quicker.

 

[CherBear]

This is definitely true. If you accelerate slightly faster, it puts you into the gearing that's more effecient, quicker.

Ive done some very non-scientific research into this using my scangauge. So far results support this theory.