Quote:
Originally Posted by milo9
Besides wanting feedback on if any of these ideas are worth trying does anyone think using boost just to get up a steep grade would produce better MPG than just creeping up it trying to keep the vacuum as low as possible without downshifting?
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Hi milo,
First, you should downshift to keep the RPMs in the best range for your engine.
It takes lots of power to go uphill. Assume that your suv takes 20 hp to cruise on the level at 60 mph, and that about half of the power goes to RR and half to aero, also that the rolling resistance is about 2% of the weight. So 10 hp for RR. A 10% grade adds 5 times as much power as RR, so add 50 hp for the grade. It takes 3.5 times more fuel to go up that hill, like 25 mpg on the level to 7 mpg climbing. Being able to go faster up the hill will use gas faster.
You mention altitude, at 6000 ft the air pressure is down to about 80% of sea level and engine performance is reduced. Can you blow enough air into the air cleaner with your leaf blower to get that power back? Probably you can. You'll need to decide if it is worth it.
First, lets consider your leaf blower, 130 mph is about 11,000 f/m and the outlet might be 3 inches in diameter(?) So that would be about 570 cfm. If your engine is 3.5 l, (about .12 cu ft) and it's winding up to 3000 rpm, at full throttle that's 180 cfm. Even if the blower is not an efficient compressor it could help. There is a formula for figuring the power required to compress air, and that is what you need to know,
one version is here. That page is a little off for this use, since we're raising a low pressure to 1 atm. But anyway it takes 2 hp to raise 180 cfm from 11.7 psi to 14.7 psi. My electric leaf blower uses 12 a at 120 v = just under 2 hp. At least it's in the ballpark.
With the usual inefficiencies you might expect to get half the improvement suggested by these numbers.
But... there is the electrical issue, can the charging system deliver 1500 extra watts? You'll need an invertor and wiring. There's the crazy plumbing for the air cleaner. When the blower is turned on it can't leak, and when it is off it shouldn't be a restriction.
To answer your last question, there is no way this will improve your mpg.
(Also to amplify what niky said, to raise the pressure by another 6 psi requires 4.5 more hp, and that's at 3000 rpm. To add that much boost at 6000 rpm would total 13 hp.)
-mort