Ive been reading ALOT lately on how to improve fuel economy beyond engine tune. From what Ive read If one were to re-install a functional EGR valve and a EVAP can mileage should improve. Is this true, will fuel mileage increase with a functional EGR and EVAP can? If so how much is expected? 13/14 MPG @ $2 a gallon is getting old real fast.

 

I think both should improve gas mileage, yes..

the EVAP stops your gas fumes from leaving your gas tank, into the atmosphere.. when you shut your car off, all the fumes go to the canister... when you turn your car on, the fumes are fed into your intake.


EGR lowers your combustion temperatures, which lowers the chance of predetonation.. so you can set your timing advanced a bit more... EGR is mainly to control emissions...

 

I'm not certain of your locale as described in your profile - Whether you're in an ozone-rich area like Los Angeles or Chicago, or in Ozone Park, NY, near an electrostatic generator, or the upper stratosphere, but if you live where ambient temperatures are relatively high and/or at higher altitudes (where the vapor pressure of gasoline is relatively high compared to barometric pressure), fuel evaporation can account for 5-9% of average fuel use. Stated another way, in a 16-gallon tank, that's 1.4375 gallons of fuel lost to evaporation in ten days.

According to C.A.R.B. statistics (not as if they would LIE or anyting), a warm day and an uncontrolled fuel tank can account for 11½ ounces of liquid fuel evaporation in a single day. In ten days, you'll lose about a gallon at that rate of evaporation. With a functioning EVAP system, those losses can be reduced to about 2.6%, or only 3 ounces of liquid fuel lost in that same 10-day period instead of nearly a gallon.

Having a functioning EVAP canister can recover that fuel "loss" to propel your vehicle instead of evaoprating off the most volatile components. It also keeps the most volatile components in the system, so your total energy per gallon of fuel is maintained. Losing volatility is similar to using unnecessarily higher octane, in that less energy per gallon is produced.

As stated above, a functioning EGR can allow you to run more total spark advance, providing more efficiency, and fewer pollutants.

Low emissions and high power are not mutually exclusive ideas. The most powerful engines tend to be the most efficient ones at any given level of displacement.

 

Thanks for the replies.

Yes high altitude is a factor (Colorado) 5000ft+ and most summer time temps are above 90*.

I guess I'll dig up an EVAP can and EGR valve and give it a shot.

Ive also tinkerd with going full vacuum over ported for timing advance. Alot of people claim increases fuel economy through more advance under cruise conditions. This actually reduced my economy about 1MPG. Any ideas why?

 

Are you following the same course, in the same weather conditions, at the same speeds and loads to compare mileage?

The drop in mileage is not beyond reason, especially if your car was set up correctly in the first place (hopefully, your engine was set up for high altitude operation). A little tinkering can have adverse effects, or can have positive effects. One never knos until one tries. A little experimentation might get you the extra few MPG you're looking for. As long as you are methodical, and change only one or two variables at a time, you should discover what works best for you.

What coolant temperature are you running? My simplistic thinking tells me that a cold air induction and hotter head temperature (but cooler chambers temps from an effective EGR) might have some mileage benefits. I would also think that with the higher density altitude, a bit more advance would be beneficial, but only if the valve events coincide well with the ignition timing. If it were mine, and I had replaced the cam for any reason, I'd be tempted to install an adjustable cam sprocket and experiment with that, too.

 

Well the "test" conditions were close for the ported vrs full experiment. To awnser the rest of the questions, T-stat is 195* so around 210-215*, air management on the bird is open element, currently working on a dual snorkle that will get air from the stock location and the power buldge opening in the hood. I backed the timing off a month back so I could run lower octaine fuel without too much preignition, 10.5:1 setup.

I do have a couple questions though.

I did install a EVAP can monday. I have it installed without a vac controll just tank line to canister to carb. Should I install a vacuum contol valve or just leave it as is?

Also the EGR which would you suggest PBP or standard vacuum contolled? I have both, cleaned and ready to go.