Tuning or Cam for best MPG?
01-29-2010, 11:17 AM
#21
Milling the 317's enough to bring the CR up...would probably make the deck surface pretty weak, and I would bet that there'd possibly be issues with alligning/installing the intake manifold too.
People are constantly looking to buy 317's for forced induction applications, so I'm SURE you can recover some of the cost of the 243's right there...799's are the same as 243's, so that opens up some more possibilities as well...at a certain point GM started using those heads on a LOT more than just LS6's and LS2's.
People are constantly looking to buy 317's for forced induction applications, so I'm SURE you can recover some of the cost of the 243's right there...799's are the same as 243's, so that opens up some more possibilities as well...at a certain point GM started using those heads on a LOT more than just LS6's and LS2's.
01-29-2010, 11:18 AM
#23
When you lean out your cruising AFR beyond stoich you will be losing torque. To make up for the loss of cruising torque you need to add timing. While cruising you can play with your timing while watching your map values to see if the engine is working harder ( higher map reading ) or more efficient ( lower map ). That being said I found playing with timing while having the cruise control set did not really change the map value you at all. Ha ha go figure 
When I added my cam I also added a set of 243 heads with a proper valve job and I had them milled .020" for 11:1 compression. Believe it or not but the top cut on your valve angle can effect your gas mileage. It's hard to beat a set of milled, valve job 243's for maximum fuel efficiency.
When I added my cam I also added a set of 243 heads with a proper valve job and I had them milled .020" for 11:1 compression. Believe it or not but the top cut on your valve angle can effect your gas mileage. It's hard to beat a set of milled, valve job 243's for maximum fuel efficiency.
01-29-2010, 03:01 PM
#24
18 city / 24 highway mpg using hptuners was my averages, with headers, ls6 intake, slp lid. When I first bought my car I flew down to buy it and on the trip back I got my best mpg ever 26. This is when it still had the EGR on it. As soon as I removed the EGR and added headers I lost atleast 2 mpg. Now with the heads / cam my averages are 19-20 city / 25-26 highway mpg. I have seen a best of 29 mpg though.
02-12-2010, 07:46 PM
#25
That's right, I remember hearing about that sort of stuff when I was on thirdgen.org. One of the guys there drives a van and he was getting 20mpg hwy with his 5000lb bus of a vehicle. I think he installed an EGR system and was testing out different cams to see what gave him the best power while maintaining as high of mpg as possible.
EDIT:
Went through some of his threads and caught a bit about injectors being ran at a higher PSI...
"The finer spray pattern helps promote atomization which helps the engine deliver more power AND better fuel mileage. Cleaner emissions too, BTW."
Does this work on LSX motors the same as it does on TPI and TBI?
EDIT:
Went through some of his threads and caught a bit about injectors being ran at a higher PSI...
"The finer spray pattern helps promote atomization which helps the engine deliver more power AND better fuel mileage. Cleaner emissions too, BTW."
Does this work on LSX motors the same as it does on TPI and TBI?
Another thing that helps mpg's is compression. more compression like 10.5 vs 9.5 will provide better thermo efficiency and more low end power giving you better mileage. if its a stock lq9 you can swap heads out for a pair of ls6 style that will give a smaller chamber to up compression. It should still be on the safe side to run 90 octane or so with the aluminum heads.
