Changing transmission or fuel injecting for better millage...?

[drewschulz101]

Hello!

I have just recently purchased a 1987 Elandan 34' with the Chevy 454.

I was wondering if anyone knows or has herd of anyone swapping the transmission from a 3 speed to a 3 speed with O/D (4L80) ??

I am also wondering the same but with switching from carborated to fuel injected?

Thanks for any info 

[beaverman]

it can be done, all it takes is money and computers !!!!!!!!!!!!!! and a lot of headaches

[MotorPro]

Either one will improve mileage slightly. You should break even in about 250,000 miles. Your best bet is to fine tune what you have. Carb adjustments and timing advance.

[Rickf1985]

Just so you have another opinion I will chime in and agree with what Motorpro says. It is all about how long it will take you to recoup the 3,000.00 plus you are going to put into it and whether that is worth it to you. A properly tuned carburetor engine will get pretty close to the same mileage as a fuel injected engine when you get into vehicles as heavy as these so your main gains there would be more in the dependability area. The engine would run smoother and last longer due to less fuel and combustion byproduct dilution of the oil. On the other hand an overdrive transmission will help a little by lowering the RPM but you have to remember that you are pushing a barn down the road. You have to keep the engine within it's power band to maintain the power needed to do that. If you drop below that power band then mileage will suffer dramatically. On long flat roads overdrive is good but when you hit steeper and longer hills you will be needing the higher rpms and a lot of times the overdrive transmissions will not downshift at the right times.

[cook elandan]

Just want to attach myself to this thread to see if you attempt it and any information you find.  I am looking to do the same.  I already have a couple  vortec 454s one MPI and one TBI with 4l80e that I am in the process of rebuilding to install into my Elandans.

[Rickf1985]

If you go that route you definitely want to go with the multipoint injection since it is OBDII and has much better computer control over the injection right down to the cylinder.

[cook elandan]

Yes, will be going mainly with the MPI, I am on a vortec blog and after hearing all the bad stuff with the vortec from the factory problems, soft cam, leaky injectors, leaky fuel pressure regulator, bad timing setup. But all fixable with improved items, the motor will be strong. And with a little modification, could push it up to 8.1L.
Rick and all the rest on here, is always good to hear your inputs. Thanks.

[Froggy1936]

Look in the projects section I have changed from Quadrajet & Turbo 400 To Throttle body inj & 4L80E trans  Knowing what I have experienced I would not do it again   The only real difference is a lower RPM @ cruiseing speed MPG difference is neglible Frank

[tmsnyder]

Just getting used to driving my P30 motorhome, initially I had the same thoughts as you but eventually found that it's quite happy singing along at 65 mph.  Once I got used to it singing (I'm used to my diesel suburban which turns ~1800 rpm at 60mph) I remembered that the GM engineers of that day knew what they were doing.  It's perfectly fine, just run it and enjoy.

If you want to try to save gas: 

- keep air up in the tires for safety's sake as well as mpg
- keep air filter fresh
- keep fresh plugs, wires, cap, rotor, oil and filter changes
- modify driving habits, slow down, time lights, stay out of the secondaries

Look in the projects section I have changed from Quadrajet & Turbo 400 To Throttle body inj & 4L80E trans  Knowing what I have experienced I would not do it again   The only real difference is a lower RPM @ cruiseing speed MPG difference is neglible Frank

[Surfinhurf]

get is running good,,efficiently,,then look at the gear ratio in the rear end.  Do you tow,,in the mountains?,,,most of our beasts had low gear ratio's to accommodate the shitty smog laden performance of the original engine. A  ring and pinion swap is cheap....er.

Good Luck
HURF

[eXodus]

how much MPG do you get ?


I had a 29ft Itasca with 454 TBI 4L80 and it got 7-8 MPG. 
You can probably get a full TBI setup with all wires and computers from a Junkyard for a couple bucks.


If you are not down to 4-5mpg just keep it in good service, drive it and don't think about it. It won't be worth the hassle.


Just if you really want to do something and have time and money to spare, drop in a late 6.5 Diesel (2000ish) with a 4L80 and some mods.
Or for Overkill a 12v Cummins.  But still you won't get any better then 12 mpg.

[tmsnyder]

12mpg is what I was thinking too, for a diesel conversion, max.   If it gets 8 now, diesel is typically 30% better as a swag, so 10-11 mpg is probably more realistic.  If it cost $3000 to do the conversion, and fuel was $2.50 a gallon for the next few years, the break even would be after 28,800 miles assuming the mileage went from 8mpg to 12mpg with the diesel conversion.

Just if you really want to do something and have time and money to spare, drop in a late 6.5 Diesel (2000ish) with a 4L80 and some mods.
Or for Overkill a 12v Cummins.  But still you won't get any better then 12 mpg.

[Rickf1985]

TBI is a glorified carburetor, It is only one step up from carburetion. If you want to take advantage of computer controls you have to go to MPI and OBD II. No matter what, You have to keep the engine in the power band so changing gear ratios be it by overdrive units, overdrive transmissions or read end gears you still need to have the engine in the 2500 rpm range to keep it in the power band for best performance. Below that you are lugging the engine against the wind resistance at 60 mph and your mileage will suffer. Now if you make major changes to the cam, intake and exhaust on the engine you can lower that power band but it is going to be very expensive to do so.

[Jupp318]

I know a guy here in the UK that has an Itasca about a '92 I think, and it has an injected 454. He reckons he gets about 18 to the UK gallon.  I think he must be joking as I get 6.2 mpg using LPG or about 8 mpg on petrol. As LPG is approx half the cost of petrol it is still cheaper to run than my old 318 D19 Brave. Would a LSX injected motor be the most efficient, I have what in the US would be a 2006 Pontiac with a LS2 motor and I get nearly 25mpg from it.

[Rickf1985]

An LS-2 can be a lot of different motors including a Pontiac 455 from the 70's but since you say 06 I am assuming you mean the 6.0l? That is still a small block and when it comes to moving all this weight there is no substitute for cubic inches. That is where you get the low end torque from and low end torque is what gets you moving. That motor is rated at 400 horsepower at 6,000 RPM and 400 ft/lbs. of torque at 4400 rpm. Both of those figures are totally worthless in a heavy vehicle. You would step on the gas at the light and it would just bog and barely move.

[fasteddie313]

Get an intake that has injector bungs and run megasquirt standalone engine management..


I bet you could do it for $1,000..


Then you can set all your air fuel ratio targets vs RPM and load (air) yourself, give fuel when you need it and cruise as lean as you dare..


https://www.diyautotune.com/

[Jupp318]

Rick,

I was only using the LS2 as an example of the LS series of engines as I have my own LS2 powered car. There is also a 454 version, given the electronic fuel injection and a more modern transmission also with electronic control and lock-up converter I would expect to see a big gain in economy.
The other question was what engine would a 1990-1995 Itasca use?. My friends say theirs is a 454 and they insist that it does approx 18mpg.  They do use it a lot and so have plenty of miles under their belt to have done the calculations.

[Rickf1985]

454 would be the correct engine for those years but I would dispute those mileage readings unless all they drive is totally flat ground and never above 50 MPH and drive away from a stop very, very slowly. I would believe 10-14 MPG. I guess I should ask what size Itasca before condemning the mileage. they go from 20 foot class C's all the way up to 34 plus foot Class A's. A smaller Class C might get that kind of mileage if you were a very conservative driver. Physics are physics, it takes a certain amount of fuel to move a certain amount of weight a certain distance. Add in wind resistance. Those things are not going to change regardless of the technology involved. You will get better than the 6-8 that carburetors average but you will never see 18 on a class A.

[Rickf1985]

I would love to see someone convert to TPI for $1,000.00. I just do not see how you can do it even after buying the parts separately.

Maybe if you are lucky enough to find a junkyard vehicle with ALL of the harness's and sensors on it.

[fasteddie313]

Well what fits these old big blocks as far as something you can find in the junk yard for a newer intake manifold that has injector bungs built into it?

Don't worry about the harness, just take the sensors with their plug and 6" of wire on em

I'm not so familiar with what fits what chevy, I'm more into Euro cars.. 

Get yourself a modern intake with all the injectors right in it..

Something like that with injector bungs right over the valves..

Get one with the injectors-fuel lines, intake air temp sensor/coolant temp sensor (same thing but 2), throttle body, throttle position sensor, grab the whole thing, and you need a manifold absolute pressure MAP sensor like how you would install a vacuum gauge..

All these sensors and injectors are basically free at the junkyard, grab a couple of each, anything GM if you cant find a pretty complete intake..

I can imagine getting that done for $2-300 if there is something that fits, there just has to be something OEM intake that fits chevy BBC right?

Then you need a wideband O2 setup to read your AFR -$100 -$150
http://www.ebay.com/itm/Innovate-NEW-3844-MTX-L-Wideband-O2-AFR-UEGO-gauge-kit-w-Sensor-Included-/400959341865?hash=item5d5b0a0529:m:m_3PAz631HU6ah74p71_L0Q&vxp=mtr
good one like mine for $150 or maybe a cheaper one.. You don't need a gauge just a controller and sensor..

Standalone ECU with harness and connections $400
http://www.ebay.com/itm/MicroSquirt-Standalone-Engine-Management-with-8-Wiring-Harness-/232033890411?hash=item36064c306b:g:F0wAAOSw2s1U06VK&vxp=mtr

You have a laptop already right or a computer in your MH?

So theirs $850 with a $150 budget left over for little stuff.. Oh add an inline fuel pump for $50-90..