Winter studies...

[Super Dave]

Well, as the season starts to drop off, I move into some prep for 2008, and then look at some things that I didn't look at during the summer.

I'm trying to learn some stuff about aerodynamics to see if there are some simple things I can do to the trailer to potentially improve mileage.  If it makes it more stable, great.  Seems to be a decent amount of information out there about "separation" and how that generates drag. 

Looking for internet information, I stumbled into websites and some interesting forums. 

Once you say that you have a diesel vehicle, everyone wants to tell you about biodiesel and collecting vegetable oil even though they have gas engines themselves.  Honestly, a diesel will just about run on anything, and I'm really happy that I made my change to my bus years ago.  Even though diesels is very expensive, it's still economical compared to my experience with bigger trailers and gas motors.

Someone on a MPG forum pointed me toward a guy that was harvesting his own sunflower oil in Kansas, and to a website forum for Lister style engines, these single cylinder diesel engines used to run generators, etc.  I did some reading, and then I actually had a couple emails with the farmer in Kansas.  He's not a scientist, but he has some real world back ground in working with engines on the farm...pumps, trucks, combines, lister style engine, etc.

Some of his discussions went back to how the plastics industry started paying top dollar for some of the polymers that were left in petroleum that traditionally was in gasoline and diesel.  That was interesting as it related to some conversations with the folks at Power Mist back in the early 90's that amounted to the same thing, but also related that to what the EPA was requiring for all the designer fuels also.

So, cutting to the fuel chase.  I had a seal replaced on the bus rear end, and it was now cold, so I was going to fill up the tank with winter fuel so I'd be prepared for some of the minor driving I'll be doing with her to some lakes and all.  After my research and my emails with the guy, Dan, I decided to spike my diesel fuel with a couple items.  Within my 37 gallon tank I now have 34 gallons of petrol diesel, two gallons of new vegetable oil, and one gallon of regular unleaded gasoline. 

The bus has a few miles, so I'm not going to recommend this to anyone really, but it's going to be interesting more in the spring when I get better opportunities with less warm up time to see what the real results are.  So, far, I'm almost giddy about it.  I did a few things that day in the bus, and I should have used more fuel. 


I think most of the aerodynamic stuff will have to wait until spring when there's warmer weather.

[spyderchick]

Welcome to the wonderful world of hippies. You've got the geek part down, you've got the naked part nailed, so just grow a beard or obnoxiously long hair and you'll be a lifetime member.  (When you get your official membership number, I can give you the names of some local CSAs)

All joking aside, it's pretty cool that you're researching this.

[Super Dave]

Hippy?  Nah, it's capitalism all the way through.  I don't want to pay $3.50 for diesel with 11MPG,  I want 14MPG consistently.  Even if it's $1.50, well, I can buy more thongs.

I put 16oz of vegetable oil in the Taurus too.  It's not a diesel.  Same idea, but I have less information on it.  So far, so good.  I need more data.



Here's an interesting thing that has me thinking too.  Years ago, a friend of my dad's and our dentist were both using this product called Mixigo.  This was around the time after the fuel crunch and I think around the time when lead was being removed from gas.  So, I was like not born, right, being twenty-six years old... ::)

Anyway, my dad's friend Charlie and Dr Hoff both swore by the stuff.  Interestingly, it sure had a nice color like vegetable oil.  I just did a Google look up on it, and it still exists.  Low and behold they state it's a "balanced compound of ashless organic materials in a pure hydrocarbon solvent". 

More "fuel" for thought, eh?

[GSXR RACER MIKE]

I've been doing alot of researching on the aero topic myself over the last couple years, very interesting. For example just an 18" gap between tow vehicle and trailer is enough for the air to fill into that void and cause drag, almost as though the tow vehicle wasn't even breaking thru the air at all - the more that gap, the greater the drag. A pick-up truck pulling a flat front trailer is one of the worst situations you can have, in that situation the tow vehicle has almost no effect in reducing the drag the trailer will cause. I have a chart I found online that shows the drag co-efficients for different shapes, a flat front trailer is almost the worst thing you can have (with the front of the trailer actually being dished in and concave like a parachute being the worst on this chart). Another huge factor is the back of the trailer, the void created behind a trailer that allows for people to get a wind tow is a mileage killer. Changing the shape of the front of the trailer to a 'V' can reduce drag, but then it still creates 'detached' air flow around the trailer, just not as bad as a flat wall being forced thru the air. According to this chart about the best situation you can have realistically today is the round front horse trailers, why they are so good is the air flow around the front of the trailers stays 'attached' to the trailer and isn't being thrust outward off to the sides (like the wind blast you get from a flat front trailer going by you if your pulled over along the side of the Interstate).

On this chart a semi (without aero bodywork) pulling a flat front box trailer is the reference point with a 1 drag co-efficient, a flat front and back trailer being pulled behind a pick-up is 1.17, a parachute is 1.35, an aerodynamic semi with the high sleeper roof is about a .60, a 60* 'V' is .51, a round front / flat back (horse trailer) is .41, a 30* 'V' is .34, a round front / round back is .1, and a basic airplane wing shape (round front tapering back to a long 'V') is only .05! My trailer is a 90* 'V' nose which I'm guessing by this chart would be about a .8 or so. Some semi's have been experimenting with 1/2 round domes on the back doors of the trailer to help bring the air back together without creating turbulence (turbulance at the back, on the sides, and on top and under the trailer all cause drag), some have also been using air dams underneath the trailers to smooth out the air even more. Another way they come up with to help bring the air back together behind the trailer is something I've seen called a 'vortex generator' which are molded pieces affixed to the sides and top of the trailer at the very back edge, they help but not like an actual dome.

[Scotty Ryan]

Dave we need to talk more about this - For my current truck and possible new diesel van..... My Nissan manual says it requires 93 research octane min gas - I have tried 89 - but never 87.... I got about a 1mpg decrease with the 89.... But I have heard horror stories with running 87 in this truck..... I wouldn't be opposed to burning veggy oil - But not to sure if it would have any negative effects somewhere in the system..... I hauled the trailer up to Darien this weekend and when I got home I filled up - 10.3 MPG - you know how I drive - Grandma style - 65 HWY - and light footed.....Just recently I installed a K&N air filter - I almost can't tell a difference - Maybe tenths to the gallon.... Normal 10 miles to work - 8 on the highway for a tank gets me about 12 to 13 MPG.... Normal Highway I see 13.5 to 15 on average..... I have seen 17mpg - driving between 35 to 50 MPH from my house to Rhinelander in a snow storm..... Also I notice that during winter/colder months I get worse mileage - can't decide weather it's cause the computer runs richer in colder weather or cause I let the truck warm up more to defrost ice or cause the quality of fuel in winter months is different..... Still leaning toward the diesel van - just can't find time to do anything about it - and then there is the money thing.......

[Super Dave]

Holy crap, Scotty!  You could have borrowed the bus and got better mileage...with the trailer!

The vegetable oil in the gas is kind of out there for me right now.  The bus, well, if someone told me we could recycle poop in the diesel tank, I'd probably be setting up a collection point.   

Mike, you're on the same stuff that I'm seeing.

The detached air flow is the trick. 

Before the travel begins for the next year, I'd like to put air dams on the front of the bus and the trailer.  That can easily be made out of plastic lawn edging for cheap. 

I've seen the vortex generators, and that looks to be a good idea for the rear of the trailer.  Obviously, a good amount of drag is developed from the back side of the trailer.  There are the stick on style Airtabs, but I've also seen some of work done at a university in Georgia, I think, where it looks like they are just placing four foot pieces of aluminum angles against the side and top of the trailer at an angle to generate the vortex at the rear too. 

I've got to go price out some inexpensive sheet metal, but I've thought about lining the bottom of the trailer to keep the flow attached also. 

The gap between the bus and the trailer is a problem, as you recognize too.  I think there's over five feet of gap between the bus and my trailer.  Other exciting issues are the facts that my bus is narrower than my trailer, but it's taller.  So, they aren't really matched.  Next, when I put different tires on it, I went with a taller tire to lower my gear ratio so I could have a higher ground speed with my "optimum" RPM.  I haven't been able to reproduce some of my incredible MPG ratings from 2003 with the original, smaller tires.  Might be due to the fact that my bus now is taller.

I'm not going to make a change there in the tires.  Kind of pricey.  So are rear end gears.

I need more guidance on whether vortex generators on the bus would help between that gap.  Obviously, it would help when it's alone, which isn't often.  If it might help, I might go that route.  I was on a site where studies were done on flat front trailers where they put vertical slats maybe 8" wide on the trailer face that kept the drag down on the face of the trailer.  For me, everything gets tricky on turns when I've really got it jacked, and that might make contact between those two pieces.  I could literally build a little canvas tunnel between the bus and the trailer.  I think that would look gay, but at least it's an idea.   

[Super Dave]

Also I notice that during winter/colder months I get worse mileage - can't decide weather it's cause the computer runs richer in colder weather or cause I let the truck warm up more to defrost ice or cause the quality of fuel in winter months is different..... Still leaning toward the diesel van - just can't find time to do anything about it - and then there is the money thing.......

You get it both ways.  Longer warm up times uses fuel without moving you forward, and fuel is formulated in winter to start.  It's not intended for economy.  So, yeah, even if your driving habits were the same as summer for warm up times, it would still use more fuel.  Use an ice scrapper.   

Engine technology is really good.  I try to reduce my warm up times to minimums.  I'm looking at adding a winter front grill cover for the bus.  But I also want to use that during the summer.  One, it will be better aerodynamically.  Two, the PSD likes heat, and the cooling system is way over kill.  I might even loose the bug screen if I decide that it's hurting my aero dynamics too.

Mike, have you bought any yarn yet to do aero testing?  I wanna do some so bad.


Anyone got GPS close to me too?  I need to see how far off my speedometer is.

[Super Dave]

that situation the tow vehicle has almost no effect in reducing the drag the trailer will cause. I have a chart I found online that shows the drag co-efficients for different shapes, a flat front trailer is almost the worst thing you can have (with the front of the trailer actually being dished in and concave like a parachute being the worst on this chart).

Check these things out...
http://www.solusinc.com/vortexstrips.html
http://www.solusinc.com/vortexstrakes.html

[tzracer]

Hmmm, I just ride a motorcycle as much as possible. My street bike gets 47 mpg.


My wife's Ninja 250 cost $3000 new out the door, $75/year to insure, 75 mpg.

[Super Dave]

How much pulling my trailer?   

[Garywc]

just try mixing up anything
Diesels will run on just about anything even its own engine oil even if fliped over it will run on its own oil till the crank seizes. unless theres an air shut off. which some have but most have only fuel shut off in case of emergency.  so maybe  you can save your old engine oil and mix it in the fuel probably might smoke a bit but used oil is free. not sure what else will happen over time to the injectors

[Super Dave]

I'm ahead of you.  I've been using all my used engine oil for about two years now.  The bus, our cars, and the bikes.  I've got a little "station" here at home now where I can let the UEO gravity feed through some toilet paper to filter it.  I haven't seen a real increase in smoke with it, and I wanna say that the heaviest mixture I've ran has been 40%...I just didn't want to spend so much more money on Wisconsin diesel when I could buy it for less in Illinois...LOL!...so, I loaded up a nearly empty tank.

Honestly, it runs very well.  There's more BTU's in used engine oil than there is in diesel.