I currently have a 1987 turbo ii car sitting at my place with 4.10 gears in it. I also have a bonestock 2000 LS1, and will soon be purchasing the t-56 to begin a hinsonsupercar performed ls1 swap.

Throughout my car years thus far I've been solely focused around drag only. I finally came to the conclusion that this time around I would like to make an all around daily driver.

For now, the motor will go in with longtube headers, an asp pulley, an ls6 intake. The future will hold nitrous, f13 cam, and possibly mild headwork. I want the car to idle well, handle well, get incredible gas milage, and be an overall all around type of car. Not some drag project. Some will say why care about milage in this type of ride? Well, I care because I'm building this to be my daily driver.. not a drag car. The bolton only ls1 will be powering this car for quite some time (likely next season). I want this to be like a car coming from a factory except alot older.. heh.

Now that you have the history here is what I'm thinking. The obvious advantage gas milage wise with the rx7 are weight. The 4.10 gears will probably hurt some on the highway, but I don't think it'll hurt much in the city due to my experience with both 4.10's and 4.30's in an f-body platform. I think with the right size tire this will probably be very little.

The thought had crossed my mind to mill the heads while the motor is sitting in my garage, and buy some new head studs and decent gaskets and put them on for future nitrous uses. My goal is to get OVER 30mpg. The obvious advantages of compression raise say by a few points (10.8?) would be response and power. But how does this effect gas milage? The added compression would likely utilize the gas better, but will it actually negatively effect gas milage, positively, or have neglible effect?

I do know that the AFR and maminator combo has shown some increases in milage due to increased efficiency combustion chamber wise, but that would likely be in the future.

Any help is greatly appreciated!!

Thanks,
Josh

 

In short... raising compression will also increase fuel economy.

-Mindgame

 

Thanks for confirming my thoughts.

Just out of sheer curiosity.. There is obviously an intended operating range for a highway cruising ls1 motor w/ 4.10 gears. I would think that would be between 1500-2000. Is there a point where compression would likely cause inefficiency at this particular range? Or is it pretty much gains everywhere at any augmented compression ratio?

This is way past practical use, I suppose because my goals are so modest. However, this is just for sheer curiosity's sake:

Which compression ratio also has the most effect on gas milage? Static? Dynamic? Will grinding a cam to have the highest amount of compression (ie. no overlap? I suppose) help gas milage as well?

I might be confused about how each statistic plays a role in engines, because I am relatively new to motors and have not yet commited them to memory. I have been doing some searches to try to clear up some of my questions with no luck.

Thanks a ton,
Josh

 

i have 13.6:1 so mine must be really good although i only get 120 miles to $80 of 5.50 a gal vp 110

 

^ thats not that great but with the autos your gonna lose alot.

If your going m6 you shoudl be happy