I'm entering this late since I've been on vacation, but I'm thinking that this experiment might yield might some interesting results. Let's break it down -- what happens if the same amount of air has to travel through a smaller tube? The air velocity increases -- like if you put your thumb on the end of a garden hose. So, faster air does what? Well, the throttle plate will be open wider to get the air moving, which we've determined allows better FE. But after the fast air hits the valve area, would it act like mini forced induction and require more fuel to prevent deadly detonation -- or introduce more air, less fuel?
you guys are all over the place on this topic and forgot about the fuel mixture at different loads and the efficency at different loads of an engine. This goes back to driving up a hill at different speeds in the same gear to figure out the best efficency of the motor for MPG. There should be a power - speed setting for a motor that yields the best mpg all affected by the engine timing fuel mixture valve timing bore stroke thermal efficiency intake and exhost factors.
The trick is to find it and operate at that point.
Let's break it down -- what happens if the same amount of air has to travel through a smaller tube? The air velocity increases -- like if you put your thumb on the end of a garden hose.
i think that comparison may be misleading.
- the intake air isn't travelling through a smaller tube, it's just going through a smaller opening, into the original size tube. i don't think the pressure "advantage" is maintained. svoboy essentially pointed this out when he mentioned the intake manifold is different (smaller volume/cross section) in the more efficient motor. if you don't change the manifold size...
- blocking a garden hose pressurizes everything upstream of the block; adding a restrictor plate doesn't do anything comparable to the ambient pressure. and i'm not sure if the effects of a pressurized hose can be compared to a de-pressurized (vacuum) intake manifold - though i could be wrong.
- also, the garden hose is expelling its contents (water) into a different medium (air) - an apples-to-oranges comparison. if it were expelling its contents into water (a narrow opening into larger volume), the velocity effect would be quickly diffused relative to air.
sorry, but i still don't see how adding a restrictor plate to an otherwise unmodified engine would help.
It's just a theory -- perhaps an optomistic experiment I could try.
How about this: since you're essentially "choking-off" the intake air, more throttle input is needed, power decreases, but what happens? Would the ECU realize the problem and compensate with more fuel, or since less power is produced, less fuel is used?
Race drivers use restrictor plates to reduce horsepower to even the playing field. I wonder how their economy is affected...hmmm.
all the restrictor plate does is limit how fast you can burn fuel so you run a little / a lot lower max power level. in the case of a smaller intake manifold there is higher velocity air flow and better atomization but we take care of that with acetone.
ok anyone else seeing slow down on response and gassavers.org not available in the past few days? it's why the double post - took so long that I forgot I clicked post already.
Added some 5cc GP-7 to a friends Xtera last night then topped off the gas tank from the lawnmower gas can to wash it down - could not syphen even a drop of gas out of the full tank after he drove a few miles. Thinks he gets in the teens but has no idea what he gets - just spends $60 a week on gas and drives like a nut sometimes. The top off with the gas can really fills it up nice glugg glugg - thing has something like a 25 gallon tank visible from the wheelwell.
So I know this guy that has a problem in town with accelerating too quickly. I won't reveal his identity, but could a restrictor force lower power around town so I...I mean so he could accelerate more slowly and use less fuel in town? Then on the highway more throttle input is required creating fewer pumping losses? I mean, it would be easy enough to try out and I could get a reading of fuel-trim (the chip I have has the capability to analyze manifold pressure too, but the car doesn't report it). I get back home late Friday...
I have a problem with the gas pedal on the xB - it is too light so much so that I get a cramp in my shin holding my foot OFF the pedal. Try a step spring on the throttle, one that adds extra tension on the pedal about 1/4-1/3 the way to the floor or even less, then you have to push HARDER to burn gas. I think an adjustable tension point on the spring would allow you to use it like a cruise control. Something I am thinking of trying. The restrictor plate would work for this applicaton also.