Supercharger boost = higher economy?

[Meph]

the catch is that in second gear your probably turning 2-3 times as many revolution to produce 1 mile of distance compared to 5th. Loading the engine in 5th gear at the same RPM and Load would simulate the fuel consumption with 2 or 3 times the mileage. Sadly the reality is a standard ICE will never see 72-105 MPG in boost, so logically it is an error.

In addition, lower loads require less air, less air will require less fuel at a givin a/f ratio. I require 5-10 times more fuel in boost than at lite cruse.You may burn fuel most effiently at x rpm and x load but that doesn't mean your using less. An engine will always require less fuel with a lighter load at the same RPM (99.999% of the time, there may be ignition issues to consider but a correctly tuned ignition follows this rule. Sorry if this is hard to follow Im not the best at explaining, but I have been tuning a turbo engine for a year now.

[EdKiefer]

Originally Posted by Meph

the catch is that in second gear your probably turning 2-3 times as many revolution to produce 1 mile of distance compared to 5th. Loading the engine in 5th gear at the same RPM and Load would simulate the fuel consumption with 2 or 3 times the mileage. Sadly the reality is a standard ICE will never see 72-105 MPG in boost, so logically it is an error.

In addition, lower loads require less air, less air will require less fuel at a givin a/f ratio. I require 5-10 times more fuel in boost than at lite cruse.You may burn fuel most effiently at x rpm and x load but that doesn't mean your using less. An engine will always require less fuel with a lighter load at the same RPM (99.999% of the time, there may be ignition issues to consider but a correctly tuned ignition follows this rule. Sorry if this is hard to follow Im not the best at explaining, but I have been tuning a turbo engine for a year now.

Yes, no way it can really get 37mpg in second gear under those conditions .
The Mini S EPA is rated like 24/34 mpg

[iplaysdrums]

Whoa. I definitely didn't get emails about any of these replies but the first. Thanks, everyone. It looks like the best course of action is to continue doing what I've been doing, and not to bother with the expense and headache of installing a smaller pulley.

I've done some back and forth with my aeromods, but I just got some parts for side skirts (and possibly a prettier front airdam), so hopefully gains will continue to increase. For anyone who's interested in the thread about my aeromods: http://ecomodder.com/forum/showthrea...ics-13787.html

I have a temporary trip device installed around the rear of the car about which I haven't gotten around to posting, but I'll definitely take photos in the next few days (before I remove the temp. and install the permanent). Thanks again, everyone, for the information. This forum has completely changed the way I think about driving.

[wdb]

I'll have to dig around to find the hill climbing threads; it's a subject near and dear to my heart (as you might imagine).

I assume that superchargers are like turbochargers in that they can be designed to provide boost at various rpm levels. A smaller unit that is geared to spin up quickly can provide boost at pretty low RPMs. I drove a 1.1 liter turbodiesel Fiat in Italy that had effective boost at 1500RPMs.

[EdKiefer]

Originally Posted by wdb

I'll have to dig around to find the hill climbing threads; it's a subject near and dear to my heart (as you might imagine).

I assume that superchargers are like turbochargers in that they can be designed to provide boost at various rpm levels. A smaller unit that is geared to spin up quickly can provide boost at pretty low RPMs. I drove a 1.1 liter turbodiesel Fiat in Italy that had effective boost at 1500RPMs.

turbo's can be setup like that to even have higher boost at lower speed if needed .Superchargers generally have more linear curve , meaning more rpm=more boost as there powered off crank rpm .

[comptiger5000]

Ed is correct, assuming a centrifugal supercharger. Roots blowers make a lot of heat, but they have most of their boost at very low rpm, and actually build some boost at idle in many cases.

[JQmile]

Works on a diesel....there's a dude who put a centrifugal on his Duramax and he's seeing a mileage increase.....apparently less fuel makes the same amount of power with boost, which outweighs the hp penalty of driving the blower. In a gas rig you can only go so lean though.

[Arragonis]

Originally Posted by wdb

I drove a 1.1 liter turbodiesel Fiat in Italy that had effective boost at 1500RPMs.

What model was that ? I'm currently FE lusting after cars (Ford KA or Fiat 500 for example) with the 1.3 Multijet which seems super economical, didn't know there's a 1.1 ?

Found this graph over somewhere where they have an argument about superchargers vs turbos and which has most bang per buck.



I can only think of one production Diesel with a supercharger though, the Mazda 626 of the early 90s. It didn't sell well, here anyway.

I think just adding boost to a Diesel would promote more complete burning so you would get more HP for the same amount of fuel, I am no expert though. I have considered a larger turbo for if/when mine fails. In for a penny, in for a grand...

[EdKiefer]

My comments were only towards gas engines, diesels work better with forced induction.

On gas motor even if you kept A/F the same if would still use more gas ,unless you could change gearing or something and FI needs richer mixture with gas to stop heat .Generally A/F goes needs about 0.5-1.0 richer so NA loaded might be 13.0-13.5 to 1 and boosted 12.5 to 1

[Phantom]

I have wondered what would happen in terms of FE if the turbo/supercharger is set to the point where it is pushing the air in at 0-1% above what is needed running NA. Reduce the pumping loss to suck air in and increase VE.