Winter success!
 

Not quite winter just yet, but winter gas is here and the temps are down so it was time to fight back. In the summer I was averaging around 43mpg on my commute. When the winter gas hit and temps dropped I was struggling to get 40mpg. I recently added a HAI and rear wheel skirts and along with a vacuum leak/lean burn thing I've been playing with, I've seen some tremendous results. The last three days of commuting have averaged 44.4mpg! I'm pretty excited about getting the same mpg in the winter as in summer.
It seems this combination of mods has been paticularly effective on the slightly down hills where I must keep the throttle open and can't coast. I used to get high 50's to low 60's mpg in those areas and now am getting high 70's to low 80's in those areas. It also takes a bit more throttle angle to climb the up hills. Open road mpg is slightly better, but not as dramatic as the slight down hills. The up hill mpg is pretty much the same as before. Also coasting has benefited from the better aero.
So here are some pics of the different mods: Vacuum Leak, HAI and Skirts.

how did you make the vacuum leak work?
 

i want to try it

go go go !

Yes,, aerodynamics are even more important in cold weather -- the air is denser so lower drag helps more. My worst tank average all last winter was 41mpg, and this winter I have video mirrors and partial front skirts, too.

Be careful with the vacuum leaks to get lean burning. There is an area from 50 degrees rich to peak egt that you can damage pistons and valves at higher power settings. If you are able to get leaner than that you will be good to go. Also if your calibrated leak is not in a central location you may be just getting one or two cylinders lean and not all of them.

Could someone tell me why my car notices no changes for aero? I am simply 40s mpg in a 2750 pound sube wagon. It uses more to warm up in the winter, then wot is wot as normal. I even put the steel bar roof rack back on, and it even whistles...no difference...fold in mirrors? who cares!
at 1781cc, and a little carb (if 280cfm for the displacement is considered "little")...why isn't the aero drama applicable?
I resorted to getting intake, heat and cold mix just right, and tune up...40s mpg, and summer of course brings more on the highway..I have chuckle out loud at how far above 40s mpg it goes..no concern for aero whatsoever.
It is even a square looking car, all wheel drive, all those heavier bearings and axles, and driveshaft and rear end..and ten gears in the 4lo-hi tranny...

Why? anybody?
I have a conclusion....

Small sample size. One tank is too low a number to be drawing conclusions from.

Bestclimb is right. I burned holes in six pistons on a one cylinder 90 cc. Suzuki trail bike. It happened like clockwork every 2,000 miles. Then I remembered I'd changed the fender from a low mount to a high mount when all the piston burning started. I changed back to the low mount fender, and no more holed pistons. That little disruption in cooling air flow caused dangerous high temperatures. I hate to think what a vacuum leak can do.

Don't worry, I'm more crazy than smart, and I'm pretty crazy :)

I happend on the vacuum leak thing by accident. Typicaly when I have a vacuum leak with this car, and it's happend a few times in 256K miles, it will surge or ping a bit on accel. This time I forgot to hook up this line, which happens to be a calibrated leak from the factory (you can check out my other thread for details), and I had no drivability issues, just a check engine light telling me it was lean and I was suddenly getting much better mpg. With no driveability issues, and an abundantly cheap supply of these motors, I'm willing to let it go and see what happens. Of course I am not going WOT while doing this :)

All seems well so far, I'm half way thru the third tank will all three of these mods and the results are still the same. However, this is the first tank of commuting. I'm interested in seeing how much of a difference it makes when it gets really coooold.

I still have my line disconnected and have yet to get a SES light (4 tanks so far, 1600 miles or so). I did put a restrictor in the line that reduced the size of the leak to approx. 3/16" dia. to prevent a light. Seems to be working. WOT when the engine is warmed up seems to be much peppier, probably the timing is advanced. Maybe someone over at ZX2uner would be willing to give it a try to see if there is any performance gain.