One thing i have noticed is that my swift seems to get better FE if it is a little low on oil (i haven't run any experiments for it exactly but it seems like my best FE runs have all been in that condition). I know that in racing it is common to fabricate a tray to remove oil from the crankshaft and keep the oil in the pan from contacting the crank and robbing power . I wonder if FE could be improved this way as well. The swift tends to spin at pretty high RPM on the highway so it may benefit more than some other cars from this mod. Does anyone have any experiance with trays or the power gains that can be expected on an engine? I found a site that has them, this is what i had in mind
I did the windage tray and crank scraper at the same time. Might as well do both while you are at it. They are a pretty easy install and cheap compared to what they cost for most cars. As far as how much it helps there is no real way to tell with a small improvement, good luck getting any solid numbers. I probably would not do it unless I had time to kill or had to take the pan off for some other reason. But if the pan has to come off a car I pretty much always put one back on no matter what the car is. I figure less than an hours work on a metro for a .5mpg gain is worth it to me
The crank scraper can help get oil off the outside of the crank and let it run down into the pan. It tries to keep the oil from splashing up in the block and back onto the crank by removing it before it gets slung off when the crank is moving upwards. The windage tray tries to keep the oil from splashing around in the oil pan. An individual drop of oil hitting the spinning crank might not seem like much lost energy but there is a lot of oil being thrown around in an engine even at 2000rpm. The effect at low rpm is not as big as it is at high rpms but that does not mean that it is only useful for going over 4000rpm. It always gives you more benefit the faster you spin the engine but even at 1000rpm I bet there is a small improvement in oil control and efficency. All a windage tray and crank scraper do is to help keep from wasting kinetic energy by keeping the oil that has already went past the bearings and no longer doing anything useful away from the crank and rods and getting it back into the oil pan as smoothly as possible.
I look at it as one of those things you do that doesn't help a lot but is cheap and easy if you already have the pan off for some reason. Doing an A-B-A run would be near impossible to do considering how much time it would take to install and remove the stuff so it is pretty hard to get an accurate measure. I would guess an engine that is driven constantly at 3000rpm or so would pick up probably 1-2mpg and probably .1mpg at 1000rpm. That would give an average increase of around .4-.5mpg for most of the people on this board that drive slow. I have seen on a sb chevy an increase of 10hp by adding a windage tray so it can have a pretty good increase depending on the engine and its use.