a possible way to improve mpg

[Ecomike]

I have not messed with the adjustable MAP sensors myself, but I have read about it in the Mods section here and either the Pirate or Madxj site tech sections. Somebdy posted a simple screw operated adjustable MAP that lets you lie to the ECU about ambient pressure, basically shifts the entire reading to the ECU by a few tenths of a volt from 0 to about 28 inches of vaccum, so that 0" reads as say 1 or 2"s, or vica a versa.

If your getting 21 to 22 mpg with a 4X4 renix Jeep DON"T MESS WITH IT! :twak:

Interesting.....very interesting.

Ecomike, I'm curious to know what effects you get from playing with the MAP sensor. Unfortunately, $$ and time have conspired against me, and I'm not allowed to experiment too much on my Renix (daily driver and all....) However, I'm one of those who pulls an average of 21-22 MPG out of a stock Renix 4x4. How I wish I had the resources to do that diesel swap!!

boojo35,

So when exactly is this valve overlap, and how does it avoid piston contact? Is it on the up exhaust the stroke or the intake down stroke? I am having hard time visualizing it happening with out piston contact, or gases going the wrong way during overlap. Is it just barely open on the intake valve, but not enough to make piston contact as it exhausts to TDC? How does it keep exhaust from be pushed into the intake manifold.
Please give me the windbag version this time, LOL :laugh3: so I can follow it precisely.

I can see how a turbocharger with possitive boost pressure in the intake manifold would solve the scouring problem!!!!!

jeepcomj,
I know some Physics and Chem Eng professors (real windbags :twak that use to give ME headaches too, :laugh3:. This light duty little thead is nothing compared to them!:laugh3:

 

[techno1154]

I have ceased to read the last 3 posts. they're just too darned long. I'm a windbag, and they've out-windbagged me. I'm surprised, and defeated. not from lack of intelligence, but lack of stamina to read their posts while simultaneously absorbing information.

:laugh2: :laugh2:

 

[boojo35]

My windbag answer is, the valves can be opened quite a ways with the piston at tdc and not hit the valves...... in fact on a non interference motor, the motor can completely jump time and have the valves open at max lift and still not hit the pistons..... I am not positive, but I do not think the 4.0L is an interference motor...... open the valves all the way at any time and they do not hit the valves...... as far as the windbag answer for exhaust scavenging and valve overlap...... do a Google search on either one...... there is a ton of info...... I have a corvette project:repair: to attend to this evening and cant really type one of my most impressive posts......

 

[jeepcomj]

:laugh2: :laugh2:

Pat, I'm a Pat too.


haha, i think i get the headache cause it's late when I post usually...and I don't read good after 15 hour days


I just read some of it and basically agree with the concepts. unfortunately, at this point, I'm unable to interject any well-planned statement to get you guys blowin wind again, as I'm too tired...yet again.

 

[traitor5150]

It's not that easy to get better milage if it where everyone would do it. This is a terrible idea all it will do is restrict your engine make it run like crap and make your milage worse. Without even getting technical or explaing why just accept that answer...:dunce:

 

[Ecomike]

That's too short concise to be a true windbag answer, LOL.

I use to make a living selling & servicing cleaning eq. and chemicals to engine rebuilders which is where I picked up a lot of engine knowledge among other places, but I have yet to do a complete engine rebuild, so I have gaps in my mechanical engine know how. I was not aware of the safe overlap, and of safe valve opening of the valves at TDC. I think I had heard of non interference motors but the details are a vague fog now. Been too long ago.

Anyway, that makes a lot more sense know. Thanks.

My windbag answer is, the valves can be opened quite a ways with the piston at tdc and not hit the valves...... in fact on a non interference motor, the motor can completely jump time and have the valves open at max lift and still not hit the pistons..... I am not positive, but I do not think the 4.0L is an interference motor...... open the valves all the way at any time and they do not hit the valves...... as far as the windbag answer for exhaust scavenging and valve overlap...... do a Google search on either one...... there is a ton of info...... I have a corvette project:repair: to attend to this evening and cant really type one of my most impressive posts......