Technical ways to improve gas mileage: TBI, EFI, Water Injection, etc.

[Elksnoutmtman]

Sent: 4/10/2005

Have anyone thought about switching to an injector system?
I saw something about that on one of the other discussions.  I'm at least curious about it with gas prices go up so high.

[denisondc]

Sent: 4/10/2005

Some people have installed a tbi injector system, in place of the carb, but I dont recall that they gave us feed back on the mpg improvement. Telling us that it starts better and runs stronger or smoother doesnt help much. The same things might be true if they just installed a new carburetor and fuel pump in place of a leaking cruddy old carb that badly needs rebuilt, ie. more than 6 - 8 years since the last rebuild.
If you do a search on the topics you might find reference to that tbi installation.

[Derrek]

Sent: 5/8/2005

I am not certain that fuel injection would make a huge difference in fuel mileage. As I stated in the thread "40mph uphill", I bought a weld in bung from Summit racing and used a spare 02 sensor from my Dakota, along with my multi-tester, to monitor exhaust 02 while driving. To my suprise, the 02 was almost perfect through the entire range of accleration and cruising. Taking this into consideration, I don't think that a fuel injection system could make a large improvement, unless it replaced a poorly tuned carburetor....

I am curious as to how much aerodynamics play into fuel mileage. I am also curious if there are simple changes that could be made it improve this. I have been trying different air dams to redirect the air around, rather than under my RV. I have not finished all of the testing yet, but in one test, I showed a 16% increase after making some aerodynamic changes....  At 7 mpg a 16% increase would take the fuel mileage to slightly over 8 mpg. Over an extended period, this would be a pretty good return on a very small investment of time and money.....

I was thinking of taking my RV to a wind tunnel..but at $10,000 per hour.....I better be able to make some serious mileage improvements...

(Reminds me of the new UPS commercial, where they are showing Dale Jarrett the UPS truck in the wind tunnel.....LOL)

[The_Handier_Man1]

Sent: 5/8/2005

OK how about this water injection for our Winnebagos?  Has anyone looked into this for better mileage?  We have gallons of water and even a pump. Now if a faucet was installed over the carb and presto....instant water injection...LOL.  Well what do you think?   Les

http://www.motherearthnews.com/library/1979_September_October/Water_Injection_Wizardry

[Derrek]

Sent: 5/8/2005

Hey Les,

Water injection was a hot topic here a few years back..... I don't recall if anyone actually said they installed a water injection system.....

Doing some research on the net, I found that water injection tends to generate some very heated discussions in various group forums.... Some swear it would, should, and does work, while others say its a crock....

There are lots of water injection kits on the market. The mileage increase comes from being able to advance the timing without detonation....

While conducting some fuel mileage testing recently, I decided to put the "add acetone" trick to the test....NO DIFFERENCE AT ALL....not even slightly...
Adding a small (precisely measured) amount of acetone to gasoline is supposed to lower the surface tension and allow the fuel to atomize better, resulting in smoother running and better mileage.

Here is some info on adding acetone (if your curious, again, my test results showed no change at all)
http://www.pureenergysystems.com/news/2005/03/17/6900069_Acetone/

[JCMAC]

Sent: 9/15/2005

HI,
  In my '72 D22C, I get 6-7 MPG.  I tow a Jeep Cherokee (3100#) like it wasn't there.  7 MPG on cool days, on the flat at 55 MPG.  Remember the HP goes up with the cube of the speed [2X speed = 8X HP....or 65 vs. 55 = 1.65X the HP] and a noticeable reduction on MPG!
  I got Doug Thorley headers - BIG difference, 5-6 MPH more on those big grades and 1/2-1 MPG better.
  Then added a Edelbrock aluminum intake (Performer 440): added 1-2 MPH on hills and a tad better MPG.  I'll let you know how my Edelbrock 750 CFM does.
John

[Elandan]

I put some Doug Thorley headers on my Elandan and they are great, power is MUCH improved and I noticed 2-3 MPG increase (not on the first trip, I was enjoying the power too much)

I found this place and they have the best deal on them, here are the Chevy Chassis headers:

http://www.dougthorley.com/cartgenie/prodList.asp?scat=38

If you use the promo code MH - it gives you 15% off of their prices... just thought it might help!

[pvoth1111]

An internal combustion motor to run its best and get the most from it needs great computers....if you want to improve mileage and  power get a modern power plant.....get a computer controlled transmission with many gears....get a laptop and tune that sucker....throw away the carburetor and quit dumping raw fuel down the intake and out the exhaust....

[Stripe]

Up until they started putting additives into gasoline, the Pogue Carb would put those "computer controlled" engines to shame..


http://truedemocracyparty.net/new-energy-sources-and-inventions/200-mpg-pogue-carburetor/

[JCMAC]

  If you have a good cooling system, run a 195°F thermostat = better MPG.  Run a 160°F thermostat = more HP.

John

[Sasquatch]

I installed a Professional Products active learning 4bbl TBI injection system on my 76 Executive with a M500 chassis and a mildly built 440.  I have tracked my mileage for 21 years now and the injection system did more to improve mileage and driving pleasure than any other upgrade (I have done a ton).  It now starts, hot or cold with a bump of the key.  It runs flawlessly at any RPM, any load, elevation and temperature.  I averaged about 6.5mpg over the last 20 years.  Every mod I did (headers, exhaust, cam, ignition, etc.) all improved the power, but mileage stayed about the same.  I cruise at 65mph out here in the mountain west.  Last summer I took a 1600 mile trip to the California redwoods... I saw as high as 8.5mpg on two separate tank fulls, and averaged 7.9 for the trip.  So I picked up 1.4 mpg.  Power went up, engine smoothness went up, driveability improved dramatically.  It will never pay off the $2000 invested in the system, but the driving pleasure is worth every penny.

[Rickf1985]

That last sentence says it all. Generally the increase in mileage will never pay for itself but the dependability of the engine is greatly increased. As is the lifespan due to a lot less gas going past the rings.

But think about it for a minute, a 1.5 MPG increase over a 50 gallon run is an extra 75 miles of travel. That is an extra hour and a half before you need to get gas! That is substantial. 75 miles at 7.5 MPG is 10 gallons at 2.50 a gallon is 25.00 saved on one 50 gallon run. That is also substantial. So according to my math, at 7.5 mpg you will need to go through 800 gallons, which at 7.5 MPG equals 6,000 miles at 2.50 a gallon to pay off the system. That is not bad at all!
This is all assuming the figures I used are within the range of the gas prices at the time and based on the 2,000 dollar price of the system.

[DRMousseau]

When your talkin less than 10mpg,.... a consistent 1mpg difference is HUGE!!!

I've often thought of an EFI system for much the same reasons. The improved drivability being the most important, easy starts, flawless uniform operation throughout RPM range, regardless of load and environment. Instant computerized fuel adjustments with modern ignition technology insure that every drop of fuel is efficiently accounted for, with absolutely no thought or skill of the operator. A typical driver can see an improvement in mpg with EFI systems, a skillful operator may see very little. but we've come a long way since the days of tweaked carbs, with the spark advance and throttle controls on the steering column!

I drove 6500mi last year and averaged 8.3mpg overall. Lowest of 6.9mpg and a max of 10.1mpg during that time period. No mods what so ever, an old 440 with over 100,000miles pushin a '73 20' Brave. I seldom exceeded 55/60mph. I will note that the lowest mpg was mostly cold weather miles and the highest was in heat with max engine temps that pushed the cooling system to it's limits, and without regard of city or highway. Given adjustment for chassis and weight difference,... quite comparable in mileage performance to that of your '76 Executive.

Surely your Exec's 440 had much improved HP,... but HP does not equate to MPG. You can move and power a motorhome with 500hp V10 or a 5hp Briggs single. And while that Briggs will require a huge reduction in gearing and still take forever to get anywhere, you jus might see a bit better mileage simply because there's less resistance to wind at only 3mph. Still, I would really expect that Briggs to get little more and no less than about 6mpg in your RV.

While gasoline has the BTU potential of MUCH greater MPG,... the internal combustion engine is grossly limited on converting gasoline to do so. Much of the energy we CAN convert, is lost to wasted heat. If the ICE gets too hot,... it will destroy itself. The only REAL way to improve MPG in these engines,... is thru improved thermodynamics. Even then, the design of the ICE is limited to about 50% efficiency max. That's a lot better than the 25-30% we see in the best of todays engines, but the cost and materials needed would be prohibitively expensive and still lack durability.

I'm gonna get a lot of flack here,.... but an EXTREAMLY general "rule of thumb", is you expect about 10-15hp per gallon, per hour from many engines in use today. You can expect about twice that per hour from diesel fueled engines (a bit more efficient even though diesel fuel has less energy potential) . This has been SLIGHTLY improved in many recent modern engines. By this "rule", your 440 rated at 225hp at 4500rpm will use about 22.5gal per hour,... loaded down, tached out, givin' ya all it can on an uphill grade at say, 70mph, maybe 3-5mpg??? eh,... close enough. Given that most of us run about 60mph at jus under 3000rpm,.... 7-8mpg or so is really about it!

Oh,.... that 5hp Briggs? I'll take all it's got to go that 3mph,.... it'll use about 1/2gal of gas every hour doin it too. That's about 6mpg. That 500hp V-10 will be SCREEEEEMIN' at over 6000rpm, you'll cover a LOT of miles in jus an hour if ya can hold on to your RV at those speeds,.... and you'll still see much the same mpg.

(Now if they could design a a space-age ceramic internal combustion engine to withstand the heat,... no more cooling systems to worry about,... eh, they'd probably shatter when you started em' up. Cold engine, instant explosive heat,... Maybe a pre-heater?!? or maybe a bullet designed RV body,... high ballistic coefficient so it drives easier in those cross-winds,.... or maybe,...)

[Froggy1936]

I have installed a 1995 5.7 (completely rebuilt) Eng and a 4L80E trans in my 1977 Mini Winnie The Engine is MFI computer controlled along with the Transmission 3 speed with OD and lock up TQ Even though I now run @ 59 MPH avg (seems like the speed everything works best) My MPG is the same as my Quadrajet and T400 3 speed used to get at same MPH but at approx. 900 RPM higher So all that was really accomplished was a 900 RPM drop Still get between 8 and 9 MPG . I have not yet tried running any long distance @ 55 MPH Frank

[Rickf1985]

Frank, you should be getting better than that, do you have an A/F meter on it? Then again, you are pushing a small block to it's limits so that might be part of the issue. Torque is made by long stroke and medium bore, the 5.7 is just the opposite with a 4.00 bore and a 3.48 stroke. The 454 on the other hand is 4.25 bore and 4.00 stroke. Much longer stroke. The only thing better would be the 8.1 with the 4.37 stroke. This is where the diesels get there massive torque from is the very long strokes. Doc, I hate to disagree but there are more BTU's in diesel fuel than in gasoline therefor more energy per gallon.

[TerryH]

Doc, I hate to disagree but there are more BTU's in diesel fuel than in gasoline therefor more energy per gallon.

Have to agree here. if I recall correctly diesel creates from 120% upwards the energy created by the equivalent amount of gasoline. All "related" to BTU's.

[DRMousseau]

I stand corrected,... Diesel fuels have about 13% more heat potential per gallon than does gasoline.

And with high-compression diesel engines being twice as efficient as typical gasoline engines, that "general rule" I've used has been pretty good in most instances. But I gotta admit,... it's been falling apart lately, as new modern gasoline engine technology has boosted it's efficiency a LOT, as compared with very little improvement in diesel engine technology.

Still,.... it gonna take X amount of "energy" to move an object and maintain it's motion over a given distance against resistances, regardless of time. And that factor of "time", is what confuses folks when tryin to improve MPG. Horsepower is a measure of power with a factor of time. Improving HP efficiency DOESN'T improve energy efficiency. It improves Miles per HOUR,... but not Miles per GALLON. The small improvements done to reduce wasted, unused or unburned fuel, doesn't improve engine efficiency, but improves MPG by reducing waste. The latter, is that seen in modern electronic engine management systems. It can be a huge improvement in reducing waste for some.

Sasquatch noted in his post, that he has greatly improved technologies in his 440 as compared to the basics that I had been running,.... we both have comparable MPG. Many note improved HP with headers, different carb, TBI systems,... and some note improved MPG's too. But so do those who "carefully" tune and adjust their basic stock setup. Derrek noted in his post here a few years ago,... that his O2 emissions were near perfect, and that he would likely not see any improvement in engine efficiency by installing a TBI system, and therefore no REAL improvement in MPG. He also noted that he'd be better off looking elsewhere for improving mileage,... like reducing drag and wind resistance.

I tend to agree. Drag and wind resistance is probably the biggest factor we contend with. It increases dramatically with speed with a HUGE affect on mileage. We can maybe reduce the drag of rolling resistance a bit, and weight too. Both improve MPG. But hard to reduce the effects of the aerodynamics of a big box! Jus can't flatten the box,...  and cant really improve our engine's efficiency.

ugh,... 7-8mpg's it is!

[TerryH]

DR, totally agree with you re drag and wind resistance being a large draw on MPG efficiency.
Have you ever considered "Air Tabs"?
http://www.airtab.com/
I don't have them,  but they are always on the back burner of my intentions. I want to go with a fairly substantial solar system with an air deflector. If I do so the Tabs would come after the solar installation to incorporate the deflector.
Curious as to if you've looked into these.

[Oz]

Froggy1936 has had them on his Minnie-Winnie for several years now.  NOTE (they are supposed to be applied in a specific direction to achieve desired results)

[TerryH]

Thanks, Mark. I had forgotten that Froggy1936 has these installed.
Thanks also to either yourself or Joan for cleaning up my previous "weird" post.
Terry

[DRMousseau]

I've only had the Cruise Air II for about 6wk,... it's my new home since the ol' Winnebago fell over and is no longer usable. It's ready to go, but I haven't filled the nearly empty 90gal gas tank yet or taken any good runs, so I don't yet know what my mileage is. It's 34', with a 460 Ford, and MUCH more weight. I EXPECT to see 6-7mpg and hope to see 7-8mpg on my venture to Florida in a couple months. For it's size, I'm sure I won't be dashin' about nearly as much as I did in the D20, which was also my primary transportation to the store and work and whatever else. So my annual driving and fuel costs will likely be reduced a bit.

I've wondered a little too, about those "airtabs", and they may reduce drag a bit at higher speed,... but reducing low speed frontal resistance seems more important to me.

The kids once asked what a hurricane is like, since I've seen a couple. I tell them, "Take a ride in the back of a pickup on the expressway,.... then stand up,... add rain and your pretty close." LoL! Now hold a 90sqft panel up, and you'll have an idea of jus how much pressure is on the front of an RV!!!

How much drag do we contend with??? Those of us who have enjoyed motorcycles would know that an RV or semi-trailer can quickly suck up a 200lb rider on his 300lb cruiser when you get too close. Factor in that big surface area again, and you'll know it's a LOT of drag force back there. But it too diminishes greatly with speed. While those airtabs MIGHT be an improvement for tractor/trailers making long high-speed runs regularly, I'm jus not sure there's any great benefit for RV's, unless the majority of your miles are on the highway. And this is the only reason I WOULD consider them a bit more. Jus a tiny savings on that twice a year 1000mi Florida run would be helpful. But the even at the generous percentage the manufacture states,... this would only be about 5-7gal savings on those trips. At a cost of about $250,... it'll take about 10 trips before I maybe see a return on them. But like EFI,... they might likely improve drivability more. Most see better improvements in the vehicle stability at speed. That would have been GREAT on the D20!!!

[Sasquatch]

To add to my post.  My Executive weighs quite a bit for a 26' coach.  It weighs in about 13.5k empty.  One of the reasons I have put so much into it was how well and solid it was built.  Also, where I live factors in.  Our freeways are a minimum of 65mph and many at 75-80mph now.  Plus long mountain grades at 6%+.  All this factors in.  With speeds so high on the highways, 55mph travel is dangerous in my opinion, which is why I cruise at 65.  With all the suspension mods and rebuilding I have done the coach is perfectly happy at those speeds.  (low profile radials, Air ride, Bilsteins, sway bars, new brakes)

My next drive train project is some sort of over drive.  I have no idea which route I will go as of yet.  Options I am considering are Gear Vendors, Rear end ratio swap, and transmission swap.  At 65 I am turning 3200 rpm and I would like to get that down to around 2600.  I have plenty of grunt to spare at those RPM's, so the lower Rs should net some more efficiency as well as quieter noise levels for more comfortable driving.

I still need to up the compression in the motor as well.  It still has the factory stock 8.1:1 which is pretty low for any kind of power output.  I am thinking of just rebuilding the stock motor and installing a set of Edelbrock small chamber aluminum heads which should put it in the low 9:1 range.  I can get a set of the aluminum heads for about the same price as having a good machine shop fully rebuild my heads.  So many projects.....

[Rickf1985]

Be careful with the compression unless you plan on running premium gas! If you bump up the compression and then have to back up the timing to prevent pre-ignition then you have gained nothing.

[DRMousseau]

Again, power improvements are not energy improvements. Your not gonna gain mpg with power improvements. And ya can't REALLY make improvements to limited energy design efficiencies. Increasing compression will gain some power,... you'll also gain a lot of heat you'll have to dissipate. Is your cooling system up to it??? If ya can't, you'll have to reduce timing, use cooler sparkplugs, and/or improve the octane rating to prevent the nasty pings and knocks due to more heat. I've considered nitrous systems for the pop needed to get up a short hill or pass a somewhat slow vehicle safely. HUGE improvement in power for a few moments,.... and heat, and stress, and excitement. But when not needed, it's jus there, waiting, while the stock engine runs as it normally should and was designed for.

Reducing engine rpms in whatever way, still doesn't improve mpg. Ya still gotta move 6-7tons from A to B. But if you have enough power at lower rpm's to maintain against wind, road, and gravity,... then you might see an advantage in longer engine life. Maybe! Your engine was designed to produce maximum HP and torque, most efficiently, in a specific rpm range. Long sustained runs are usually best at that engine speed. Outside that range,... you'll find unseen stress and strain that can actually be damaging, AND detrimental to mpg.

If you had a big multispeed transmission, gearbox, or whatever... your STILL gonna drive on that RPM curve. Goin 20mph in 12th gear isn't gonna be good on your engine if not designed for that. Neither is running 80mph in 2nd gear! And there's still no mileage gain,... the latter will see worse mpg due to wind resistance too.

You sound like ya have a good setup,.... and mpg is about right for a rolling 6-7ton box. Ever think of a hybrid assist??? Better mpg,... thought not truly due to improved engine efficiency.

[Sasquatch]

8.1:1 compression is simply too low to build any good power or efficiency.  Especially when controlled by my fuel injection system.  Going into the low 9's would still allow the use of regular unleaded.  As far as cooling goes, my system works so good it is hard for me to get it to run warm enough, even on the hottest of days, so heat is no issue.

Lowering the rpms, as long as your motor will run well at the lower speed, will net a better mileage.  Each time that 440 makes a revolution it is moving a LOT of air and fuel.  Slowing it down will help.  I have designed my motor configuration to start pulling hard at 2,200 rpms, and be in the sweet spot between 2500 and 3500.  So lowering the cruise r's down to the lower range could not hurt.  But you are right, with my previous setup it did not have the power to push that rig at 2500 that it does now.  And back then, lowering the engine speed at cruise would have hurt because it was not optimized to produce power at that point.  I cured that with getting the right cam grind from Comp, advancing it 5 degrees, tuning the injection system better, and the long tube headers/exhaust combo.  I joke that it will pull a house off it's foundation at idle now.

This coach was built when 55 was the cruise speed.  And at 55 the motor is turning a nice slow 2600-2700.  55 is too slow for the areas I travel and for me.  Spent too many years in fast cars and on fast bikes to be comfortable cruising at 55 when traffic is going 80.