Any guess on what MPG gains I'd get if I removed power steering and air conditioning?

[cheapybob]

I think on my 97 Saturn SC1 I can use a different belt and bypass either or both of these without needing any other changes.

Anyone know how much MPG gains I might get by bypassing either or both of these?

[Compaq888]

expect 3-5mpg

[Matt Timion]

I'm guessing 1-2mpg, but I'm VERY interested in knowing either way. Are you going to run a controlled experiment in order to determine the exact results?

[cheapybob]

Originally Posted by Matt Timion

I'm guessing 1-2mpg, but I'm VERY interested in knowing either way. Are you going to run a controlled experiment in order to determine the exact results?

If I do it I will. I have a scangage and a 25 mi test trip that I run at a steady 60 mph to compare with. 1997 Saturn SC1, EPA rating 28 city, 39 highway, 33 overall. Baseline with no mods, fresh tuneup, 45 psi tires and all synthetic fluids was 40.4 mpg. Adding hot air intake got it to 43.6 (max temp 119f). Insulating it and putting in a 2c higher thermostat got me to 46.8 (max temp 179f). Adding a resistor to fake IAT temp of 242f and a manifold to get the intake temp higher (up to 230's) got me to 51.4. Aero mods to smooth front end and cover almost all holes got me nothing. Spark plug gap reduction to .035 got me nothing. Using my foot instead of cruise control got me to 53.3. If I run it at 65 mph the mpg drops by 3 or 4. MPG's are higher is I was to go slower, but that's too dangerous here in Chicago. 60 in a 55 is about as slow as you want to go if you value your life.

[MetroMPG]

can you give a bit more info about your testing?

- were these tests conducted at the same ambient temperature?

- round trip, or one way? (grade & wind issues)

- in a traffic flow, or on your own (aero differences from corridor effect)?

- cruise control for testing purposes or manual control?

[cheapybob]

The baseline and mods up to 46.8 mpg were in cold conditions, ie around 30f. The more recent ones were at about 65f. Interestingly enough, all the Saturn gurus were saying my MPG improvements would dissapear with warmer weather and summer gas, but it hasn't happened that I've seen.

All are round trip with same 5 mi warmup trip to starting point back to the same end point with RPM +/- 100 max, and there was no drafting of traffic, ie nothing closer than 50 yards in front of me. Cruise was used for initial tests just to eliminate variability, but I don't plan to use it because I found that I can do much better with a steady foot. Cruise control costs 3 mpg from what I've found as compared to keeping one eye on a TPS and RPM reading. I don't do any of the coasting, shutting off the engine, or driving at 45, or porposing type stuff like I've read here. My point was/is to see what I can get normally driving on the highway at reasonable speeds. Around town I'm getting just under 40 mpg in suburban stop and go driving at an avg of 27 mph. I only mention that for comparison purposes since I consider that kind of driving impossible to use for any kind of test because there are way too many extraneous variables involved.

[cheapybob]

Originally Posted by Matt Timion

I'm guessing 1-2mpg, but I'm VERY interested in knowing either way. Are you going to run a controlled experiment in order to determine the exact results?

BTW, I found someone that added PS and an idling AC compressor to their Saturn, and they said there was no noticeable change in gas mileage. Admittedly this person wasn't testing for gas mileage, either, but I'd guess that means if I get 1-2 mpg out of it, I'd be doing well, and 3 to 5 mpg is an unreasonable expectation. If it were AC that was running vs no AC, it might be a reasonable difference.

[kickflipjr]

Hey, cheapybob i guess you found the site from my link on saturnfans. I was hoping we could get some more saturns on this honda dominated site :P




http://www.gassavers.org/forum_topic/ac_and_power_steering_on_fe.html

this thread shows some improvement by removing ac/ps.

[Matt Timion]

Originally Posted by kickflipjr

I was hoping we could get some more saturns on this honda dominated site :P

As do I. I didn't realize until recently that Saturns were build for fuel economy. Just check out the EPA ratings for Saturns and you'll see that high MPG was always a goal.

[diamondlarry]

MPG's are higher is I was to go slower, but that's too dangerous here in Chicago. 60 in a 55 is about as slow as you want to go if you value your life.

I have driven in Chicago numerous times at the posted speed limits(45 & 55) and have never have never had any problems nor have I even had any close calls. I stirred up quite a bit of trouble on another forum by sharing my views on going the speed limit so I won't go into that much here but I never worry about going the posted speed limit wherever I am; it's not my problem.