"Hypermiling" and getting excellent MPG - what to do?

[crasster]

I want to "push the limits" of my Dolphin.

On another forum that I visit, there are so many people that are "stuck" from RV travel because of gas prices.

I'm one who only wants to travel for my kids to have fun and see the USA.

I am too kind of "stuck" not exactly financially, but because I'm a cheapskate in ways.

I have another vehicle that gets 40+ mpg and the thoughts of "tents" is coming to mind for far trips.

A 900 mile trip in my 1987 Toyota Dolphin with the 22RE would cost around $500 or so (round trip) in gas alone on a good day. Here in Texas, gas is currently $3.55 a gallon which is probably better than many places in the USA. But it's still high.

So anyway I thought I'd ask here on the forum for any advice, any mods, or anything that can improve the MPG of the Toy home. I know this is probably pushing the button some, but I'd LOVE to get 20 miles per gallon. I know it's nearly a 6000 pound vehicle, but it is also a 4 cylinder.

I'm sure a thread like this will help many people. I really want to "push the limits of MPG" to help trips be easier on the wallet.

So far the following things I have heard can get you better MPG.

1) Absolutely correct tire pressure stated on the sidewall of the tires. You want it at maximum to reduce road surface contact. (some debate?)

2) Good clean oil.

3) Good spark plugs.

4) Unrestricted cat converter

5) Install a cold air - air filter. ***see below***

6) Lighten your load, empty tanks. Fill at destinations and empty before you leave.

7) Airtabs?

8) Slow down (yeah I know hard right LOL). 50-55 mph

I'm open to any suggestions and I hope all this helps others.

[Fred3]

Mine is an '84 Dolphin 4 cyl 4 speed stick.

New tires properly inflated, level ground at 5000' elevation commuting back and forth on wet and light snow and not much wind... drove 45 max just to see what I could get. I got 20 mpg over 200 miles. Here's the catch... my tires are not the ones the speedo is calibrated to. Therfore there is a 4% error as measured from real-time data. I actually got 19.2 for that tank.

I don't think it is possible (for me and my vehicle) to get much better. The point I made to myself is that if I drive with a very light touch, I'll get there... stop trying to make good time... don't be in a rush... and I'll save gas. If I'm in a rush, I can always drive harder... and sometimes I think it is worth it. By the way, Craig's list Humboldt CA has been advertising an 80 Dolphin that gets 20+ mpg. I dunno.

Worst mpg 11 into strong winds uphill and full throttle. Typical is 16.5, but multiply by 96% to get the real mpg.

I have not tried any non-stock setups such as air filters or whatever. I've thought a Webber carb would be an interesting change based on what others have said.

I have removed the roof air. I travel with about 15 gallons of water in the tanks. I minimize the weight we pack, but we do pack for 30 days for out trips, so the cupboards are pretty full of gorceries.

[waiter]

I live at sea level, I get between 13 - 14 mpg at 60mph. This number goes up to 16 - 17 if I slow to 50 - 55mph.

I'm planning a 10,000 Alaska trip next month, I flight plan at 55-60 mph, 13mpg, and $4 per gallon. Fuel cost is almost $3,100

As you'll surmise from my Avatar, I'm also heavy into aviation.

With the MH, straight and level, no wind, we have two factors that effect gas mileage, Rolling Resistance, and aerodynamic resistance.

Rolling resistance will be effected by some of the things you mentioned, weight, tire pressure, mechanical resistance (engine, transmission, drive train, etc)

As we start getting above 15 - 20 mph, aerodynamic resistance is going to be the biggest factor.

Drag goes up by the square of speed, Increase the speed by a factor of two, 30mph to 60 mph, and you just increased aerodynamic resistance by a factor of 4.

Some type of air deflector on the back would help.

I thought about getting an 6 ft piece of 12 inch PVC pipe, cut it long wise in thirds (3each, 120deg pieces that are 6 ft long), Then mount these on the sides and top with 4 -6 inch standoffs. These would help fill in that huge vacuum source, the back of the MH.

I wouldn't even want to guess as to what this would gain, maybe 1/4 mpg at 60 mph.

The largest gain will be realized by slowing down 5 mph.

Give me two Pratt Whitney F100-3 TurboFans with afterburner, and I could easily get the Dolphin up to Mach 1, Fuel burn would be around 2 gallons per second.

John Mc

88 Dolphin 4 Auto

[crasster]

Just brainstorming, but do you guys think a bug guard could help "throw" the air current off the windshield and getting stuck under the overhead bunk causing drag? Perhaps it would stream the air over to the more aerodynamic part of the bunk? Just a thought with 100% no scientific backing - just sitting here with a bottle of suds.

[Derek up North]

Though I've never used one (yet), I suspect a properly used vacuum gauge would be very helpful Then maybe change the rearend gearing (4.56:1, 4.88:1) so that the engine is operating at it's most efficient rpm for your chosen cruising speed, be it 45, 55 or 65mph.

I agree with what John says about the aerodynamics. You might also consider some sort of front air dam under the front bumper to redirect air flow from under the 'dirty' motorhome body.

I don't remember exactly what you've got, but the mechanical losses with a 5-speed will be less than with either automatic, especially yours (maybe) which doesn't have a lock-up torque converter.

[Ron 'n Sue]

I live at sea level, I get between 13 - 14 mpg at 60mph. This number goes up to 16 - 17 if I slow to 50 - 55mph.

I'm planning a 10,000 Alaska trip next month, I flight plan at 55-60 mph, 13mpg, and $4 per gallon. Fuel cost is almost $3,100

As you'll surmise from my Avatar, I'm also heavy into aviation.

With the MH, straight and level, no wind, we have two factors that effect gas mileage, Rolling Resistance, and aerodynamic resistance.

Rolling resistance will be effected by some of the things you mentioned, weight, tire pressure, mechanical resistance (engine, transmission, drive train, etc)

As we start getting above 15 - 20 mph, aerodynamic resistance is going to be the biggest factor.

Drag goes up by the square of speed, Increase the speed by a factor of two, 30mph to 60 mph, and you just increased aerodynamic resistance by a factor of 4.

Some type of air deflector on the back would help.

I thought about getting an 6 ft piece of 12 inch PVC pipe, cut it long wise in thirds (3each, 120deg pieces that are 6 ft long), Then mount these on the sides and top with 4 -6 inch standoffs. These would help fill in that huge vacuum source, the back of the MH.

I wouldn't even want to guess as to what this would gain, maybe 1/4 mpg at 60 mph.

The largest gain will be realized by slowing down 5 mph.

Give me two Pratt Whitney F100-3 TurboFans with afterburner, and I could easily get the Dolphin up to Mach 1, Fuel burn would be around 2 gallons per second.

John Mc

88 Dolphin 4 Auto

Have a Winni '92 and we 'were' going to try to make a round trip from Vancouver Island to Ontario. That's about 10,000 km. But we chickened out. It could have been fun.

Where will you be starting your 10,000 miles Alaska trip from? Any special things you plan to do to your Toy before heading out?

[waiter]

NW Ohio to Deadhorse Alaska - 10,000 miles round trip.

Prep is doing all the same stuff Cresstar is doing, and then some. Bring all the preventative maintenance up to date, and replace all critical rubber components (hoses, belts)

My Dolphin has been gone over with a fine tooth comb and is in better shape than the day it was new.

John Mc

88 Dolphin 4 Auto

[wistoy]

A new O2 sensor would help milage if not allready new. the 02 is how your computer reads and adjusts our injectors. - fuel to air ratio

[MikeS]

I've wondered for some time whether instead of using air, using helium in the tires and rear air suspension bags would add lift to the rig and reduce the rolling resistance.

Mike

[waiter]

Here's the Question; What weighs more, 45 pounds of air, OR, 45 pounds of Helium???

Helium has a density of 0.00018 grams per milliliter

Air (80% nitrogen) is 0.00128 grams per milliliter

A Cubic foot of air weighs about 10 times a cubic foot of Helium. (Density at sea level pressure)

If we were filling the tires by volume i.e. I need 10 cubic ft of nitrogen vs 10 cubic ft of Helium, the tire filled with helium would be 10 times lighter (well, the weight of the air in the tire)

HOWEVER, the tire would also be very flat, because it would be about 1/10 the pressure

You'll need to put in about ten times the helium (by volume) to get the same pressure. So the answer to your question:

No they would weight EXACTLY the same.

A couple followup comments regarding the use of Nitrogen. (Please keep in mind the air your breathing now is about 80% nitrogen)

You'll find 100% high pressure Nitrogen used in high pressure applications (struts, aircraft tires) three reasons:

1) Moisture - A regular ole air compressor is also compressing (concentrating) all those H2O molecules (water). Dried Nitrogen has had the H2O removed. Water contributes to corrosion and more importantly, can condense out and even freeze.

2) The higher the pressure, the more oxygen, Oxygen is the main ingredient in corrosion, oxygenation of rubbers, seals, etc.

3) The faster version of Oxygenation is commonly referred to as "Explosion", as in BOOM. In systems like compression struts, These are filled with Nitrogen mainly for the first two reasons, but in higher pressure struts, a condition known as "Dieseling" could occur if any Oxygen were present, and the strut is compressed very quickly i.e. like an airplane landing and the wheel struts compressing, like almost instantly as the plane hits the runway. (Picture in your mind a Diesel engine with the piston coming up on the compression stroke, BOOM)

John Mc

88 Dolphin 4 Auto

[Derek up North]

Some of the tire shops around here use Nitrogen at no extra cost.

http://www.popularmechanics.com/cars/how-to/repair-questions/4302788

However:-

http://news.consumerreports.org/cars/2007/10/tires-nitrogen-.html

[WME]

Beyond a very careful tuneup and proper driving habits, everything else you do will not be cost effective given the amount of driving a Toy MH actually does.

[86rader]

4 speed stick and driving very slow should get you to something close to 20 mpg. i doubt an auto equipped model could unless you had a very stiff tailwind.

[SteveJ]

I have been looking into the hydrogen generators (HHO) the claims are that they can increase your gas mileage by up to 70% with an initial investment of less than $100.00. When I can get around to installing one on my 90 dolphin I will post the results.

[zulandio]

SteveJ did you ever make that generator and if so did it have any effect on your gas mileage?

[linda s]

5 years later you probably won't get a response. The date is on all posts and it helps to know when stuff was put up

Linda S

[86rader]

It is an interesting topic though. There are some ways to improve aerodynamics. There is a pretty good thread on ecomodder.com about a guy that put a boat tail on his ford C class. I believe it also had the benefit of being diesel. If I recall he was able to get this rather large RV pretty close to 20 mpg.

For toys, I think, by far, the best mod is to just slow down a bit. C Class aerodynamics are horrific. Fortunately, they don't really matter a hell of a lot at 45 mph. One of these days I will find that 4 speed shorty sunrader. When I do, I think I can get it into the 20s.

 

[zero]

Doing it with a diesel that is already 30% more efficient changes everything.  My 1992 Dodge-Cummins extended-cab truck, 4WD, with a camper on the  back got 17-18 MPG average going to Kentucky from NY at 65-75 MPH the whole way.

I think conventional "hypermiling" as I understand it - is a load of hooey when applied to motorhomes.  If somebody wants 20 MPG with a gas engine - wind-resistance has to be cut and that usually means a low and slippery roof is a must.  Also an engine that - at cruising speed - is running at the peak of its torque curve.  Gas or diesel engine is at peak efficiency when at the peak of the torque-curve and that is sometimes hard to do with a vehicle designed  to run well at many different loads and speeds.

I find doing "studies" on fuel mileage greatly problematic.  I'm not sure if anyone throws off more BS then for MPGs.  Even people I know to be honest come up with fuel-mileage fantasies. I think one problem is that magical "one time 22 MPG fill" that sticks in memory, while the 99% of the 12-14 MPG fills get forgotten.  Also seem to be a lot of people now adays that do not know how to compute actual fuel mileage.

In my opinion - having a manual trans instead of a power-robbing auto trans with a constantly slipping torque-converter is a must for optimum fuel mileage.  Also a pop-up roof.  Also small tires and as low to the ground as can be done safely.  Also an efficient engine and sometimes - the carbed engines are better then the 80s EFI engines.  

[86rader]

A properly tuned carb likely is better than 80s EFI, so long as you are very careful with how you do it. The problem is that when you are asking that much from a small engine, you are quite likely to find yourself in a condition where you are applying too much throttle for conditions. In this case, the carbed engine will be in a rich mixture condition, whereas the smartypants EFI will make up for your clumsy right foot and maintain a proper mix. This is a case where a vacuum gauge is very helpful.

I do agree that the MT is definitely the way to go, for a few reasons.

First and foremost is you lose the power robbing torque converter. Another is you can effectively hypermile. By hypermiling, I mean doing things like installing a FI cutoff switch which will allow you to save a fair bit of fuel on long downhills. Newer OBD2 systems do this automatically. You can also take advantage of coasting in neutral (with the engine off if you are brave/stupid enough) to try. I do it regularly in my focus, I would be a bit more hesitant in a toyhouse, but, I could see conditions where it might work fine such as long moderate downhill stretches with no traffic.

[Back East Don]

3 minutes ago, 86rader said:

A properly tuned carb likely is better than 80s EF

I had a 86 Honda CRX HF which under the right conditions got great mileage.  It was light and small and when it was hot out, it easily got in the high 50's.  In the winter MPG dropped significantly but in the summer it was excellent.  We took a camping trip from MA to Virginia Beach.  We loaded up the back with our camping gear and a full cooler as money was tight for us back then.  We did an average on that trip of over 60mpg.  When it was hot out I could regularly repeat this on long trips.  It became a sort of personal challenge and I'd go easy on the gas pedal to try to get the best mileage I could.  Push this car though and it of course fell well into the 40's and if real hard into the high 30's.   This car had a 3 barrel carb unlike the regular CRX and SI version which were fuel injected.  The first barrel was for idle and was tiny.  Then the main barrel and passing barrel.  If you kept the last one from opening up it got great mileage.  Fairly easy to do with most normal driving conditions.  When the Prius later came out touting its great mileage in the 40's range, I found it particular.  I know that cars got heavier with all the safety requirements and all but I really enjoyed my little 2 seat roller skate.  This is all anecdotal and presented as only my experience.  Fun little car.

[86rader]

Would like to see Honda do a modern version of that car. Use a 3 cylinder < liter engine direct injection and a 6 speed. I'll bet such a vehicle could crack 70mpg on the highway. The first gen insights with MT were capable of getting close to 100 mpg in the right conditions. Wish they would bring that back. I suspect they might eek a few more mpg out of it with direct injection.

[Back East Don]

4 minutes ago, 86rader said:

Would like to see Honda do a modern version of that car. Use a 3 cylinder < liter engine direct injection and a 6 speed. I'll bet such a vehicle could crack 70mpg on the highway. The first gen insights with MT were capable of getting close to 100 mpg in the right conditions. Wish they would bring that back. I suspect they might eek a few more mpg out of it with direct injection.

The new CRZ was a lot of disappointment including mileage.  A lot of that is weight.  Just not a great car in any way.  Sluggish handling, poor comparative mileage and performance.  The joke is why did they call it the CRZ?  Because no one wanted to buy a CRY.

[86rader]

Yeah, the CRZ was a huge disapointment. They were more worried about making a comfy fast car than one that gets good mileage. Should have just updated the Insight. Give it a pure EV mode by adding a second clutch between the electric motor and engine.

[zero]

11 hours ago, 86rader said:

 

I do agree that the MT is definitely the way to go, for a few reasons.

First and foremost is you lose the power robbing torque converter.

Yes, and also the hydraulic pump in the trans robs power constantly. On farm tractors we could measure it and it took 4 horsepower, all the time, to run the transmission (hydraulic) pump.  I don't know what that figure is on something like an A43D. 

I used to love Subaru 4WD wagons when I lived in NY (as winter cars).  The difference between the autos and manuals was amazing though.  Both had 1.8 liter engines and 4.33 axle ratios as I recall.  Model with the three-speed automatic got around 18 MPG on the highway.  I had a 85, 88, and a 92 and all got same poor fuel mileage.   Same rig with a five-speed manual got 24 MPG on the highway, and again - I had many of them over the years.

Now with new cars and trucks?  Seems soon there will be NO manual trans option.  I don't know if that means they have removed the loss or we are all just getting dumbed down.  No manual trans available anymore in large GM or Ford trucks as it is now.  Autos with many speed ranges instead, but how pump loss is dealt with I do not know.

When it comes to Honda stories - yeah - they did good but were also very light.  I had a 1981 Accord with a 5 speed that got 42 MPG on a few trips, but mid-30s was more the norm.   My 81 Chevy Chevette did better at 46 MPG consistently (but it had a 1.8 liter Japanese diesel).  Such figures do not carry over to a vehicle that is working hard like a Toyota RV. if it did, I'd have one of those little diesels in it.

[Maineah]

Modern automatics do better than a stick these days for a few reasons. Multiple speeds, lockup converters and being able to shift quickly. The road mileage is pretty close for both with lockup converter but the auto will win else where because it can maintain a constant engine speed not on and off the gas every time it shifts and with multiple gears and electronic management  it often is a good deal smarter than the driver as to what gear it should be in for max results. If you want mileage in any thing slow down! I have engine scan device on my Tacoma and it is just about spot on to paper and pen on mileage. Towing my camper at 50 results in reasonable mileage close to 15 even in hilly areas once on the highway at 60 it drops to 13+ add 5 MPH it drops another 1-11/2 MPG at 70 I'm down to 10-11 a camper behind a truck is not much different than a MH. they are both bricks.

[Maineah]

12 hours ago, 86rader said:

A properly tuned carb likely is better than 80s EFI, so long as you are very careful with how you do it. The problem is that when you are asking that much from a small engine, you are quite likely to find yourself in a condition where you are applying too much throttle for conditions. In this case, the carbed engine will be in a rich mixture condition, whereas the smartypants EFI will make up for your clumsy right foot and maintain a proper mix. This is a case where a vacuum gauge is very helpful.

I do agree that the MT is definitely the way to go, for a few reasons.

First and foremost is you lose the power robbing torque converter. Another is you can effectively hypermile. By hypermiling, I mean doing things like installing a FI cutoff switch which will allow you to save a fair bit of fuel on long downhills. Newer OBD2 systems do this automatically. You can also take advantage of coasting in neutral (with the engine off if you are brave/stupid enough) to try. I do it regularly in my focus, I would be a bit more hesitant in a toyhouse, but, I could see conditions where it might work fine such as long moderate downhill stretches with no traffic.

Toyota was far ahead of the rest as far as fuel injection. It was multi port and very well controlled including off throttle fuel cut.. As far as I am concerned when the last carburetor is in the scrap heap it will be a good day they are nothing more than a block of metal with a hole bored in it to let fuel through.

[zero]

22 hours ago, Maineah said:

Toyota was far ahead of the rest as far as fuel injection. It was multi port and very well controlled including off throttle fuel cut.. As far as I am concerned when the last carburetor is in the scrap heap it will be a good day they are nothing more than a block of metal with a hole bored in it to let fuel through.

No it was not. I can't say I've researched the subject  much, but . .     The fuel injection in my 1988 22RE is crude and not something Toyota invented.  It is a crude copy of the 1973 Bosch L-Jetronic system that many Datsuns had in the 70s. It came out early 70s and many different makes of cars in Europe paid Bosch for license to copy it -just as Nippo Denso did for Toyota.  I call it "crude" because a four-stroke-cycle engine fires every other stroke.  So at 1000 RPM, each cylinder fires 500 times.  That L-Jetronic system fires every stroke, so one charge just sits there doing nothing until it gets used by the next (power) stroke.  My 79 Datsun had the same system.

Many cars and trucks with carbs got better MPGs then when fitted with various forms of electronic fuel injection (until in improved).  EFI certainly made them start better in cold weather though. It also made them easier to drive from a cold start.  No more choke, choke-pull-off, heat-riser valves, or accelerator pumps to malfunction and make cold driving miserable.  LOTs of other things to go wrong though.

 

[zero]

22 hours ago, Maineah said:

Modern automatics do better than a stick these days for a few reasons. Multiple speeds, lockup converters and being able to shift quickly. 

True enough for overall driving MPGs.  Not true for just highway  mileage.   NO matter how many ranges an automatic has -it still robs power to run a hydraulic pump.   A standard trans will have less loss when cruising down the highway in high gear.  That is, unless someone has invented an automatic trans with no power-robbing hydraulic pump .  Closest to that I am aware of is a belt-driven continuously variable trans (CVT) that Subaru had early-on with electric solenoids and no hydraulics.  Ford C-Max has it.  So do certain Toyota Corollas, et. al.  Some sort of hybrid Toric Drive but can't say I know much about the new ones.