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So I have a bit of an update... While the dodge 4.7 engine performance changed noticeably with this update, the jeep did not. on a longer day trip with me driving I got the 23.3 mpg tank over 125+ miles. The wife on the next tank had some longer hiway runs and got a 17+ mpg tank. Both are pretty high for her jeep wrangler JK. Her in town mpg' however tanked on another tank and was coming in at 10.5 or so and then an 11.5 or so. Pulled the mod and her mpg's went back up to 15's on her normal drives.
So what I have learned... I believe the benefit will show if the intake manifold volume and the engine has the ability to make good vacuum overall. There have been a few scenarios where vacuum goes to 0 on the 4.7 truck engine and it becomes a total turd.
I have picked up a check valve to use on the 4.7 motor to see if I can improve on that condition where there is 0 vacuum. What I did was to put it inline with the bigger tube hooked up to the brake booster line and added a smaller vacuum line to the same cap as the brake booster line feed to that tube. 2 lines on the same cap. The thinking is when the vacuum in the IM is high, it draws a vacuum in the tube quickly but then when the throttle is opened up, it is bleeding air back into the tube at a slower rate. No idea if this will help or hurt, will have to drive it and see. There is a slight change in performance on the drive earlier in this config.
MPG's have been in the upper 18's to 19 mpg pretty consistently, and that is with a new gas leak at the top of the tank so i cant fill it 100% now as I did previously. I believe the leak is coming from pump seal and will be swapping it out soon. With the leak like it is, mpg numbers dont hold a lot of weight since there is fuel loss.
If the new config works out for the Dak, will duplicate on the jeep and see how it does. I did experiment with different sizes of tube on the jeep and the smaller tube performed better.
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