Aeromodifications for large motorhome

[Charles7a]

Hi Lee,

Thanks for your reply! I am surprised to hear you couldn't get an ADLD cable to work. I have a GM ODBI (not a ODBII) connection and ECM. TunerPro RT is freeware/shareware and works well for GM ODBI. But there is no easy way to track average MPG. It will only show real-time MPG. It will be easier to have a MPGuino permanently hooked up in my motor-home. I will start with your settings and tweak from there. If I had ODBII I would have bought a ScanGauge.

Boat-tails may work better than AirTabs for fuel economy, but I do not have room for a boat-tail. I need to keep my motor-home short for maneuverability and the ability to park it in my driveway. AirTabs do help stability when semi's , buses, and large RVs pass by in either direction. There was a noticeable difference. I do not know whether they helped my fuel economy. I knew that they helped stability so on my *PREVIOUS* RV I used them for ugly-as-sin "virtual" wheel skirts. Again, I do not know if they helped fuel economy or worked effectively as "virtual" wheel skirts.

Folks on this forum are adamant that AirTabs do not improve fuel economy or only help fuel economy minimally and are basically crap. They may be correct. They did help stability. Perhaps they do not assist with fuel economy because vortex generators actually increase drag to change the airflow. I will be keeping the AirTabs on due to the noticeable increase in stability during cross-winds and passing traffic.

Charles

[CrazyLee]

Hi Charles,

I haven't tried Air Tabs, and my RV doesn't sway much when a semi passes by. I'm leaving them off.

As for the ECM I'll have to check the part number for the type inside the box. I think the ECM is probably OBDI. There is little chance I'll mess with the box, it is sandwiched vertically on the steering column.

Try the MPGuino setup I used. I know that the VSS speedometer number was spot on. I reduced it by 1 to make it more accurate. I had lots of E-way travel to check mile posts. LOL The Micro pulses per gallon still needs work.

Getting new actual fuel mileage figures is easy, the costs may kill the budget! I'll have to fork $220.00 to fill it up! I'm waiting for prices to go down.

You may want to build an air bag boat tail. Make it from canvas and fasten it to the back. Make air scoops on top to blow it up when driving. WOW! what a sight that would be!

Maybe the OBDI cable you have is different. I got mine from ALDLCable.com What did you get? I may buy a blank cable and build a interface for it. Lots of options, so little time.

I have a brand new OBDI serial cable available if anyone needs one.

Lee

[pete c]

I think the boattail trailer is worth considering, since you have a toad anyway. This boat tail will be much longer and more efficient. Also is the benefit of not sandblasting your toad or putting lots of miles on the suspension.

Tight turns dictate that there be a fairly substantial gap between RV and trailer, but, I was wondering about the idea of a telescoping trailer tongue that could pull the trailer in tight above 40 mph where aero matters and large steering inputs mean you have bigger things to worry about than mpg as you are fixing to flip your shiny high $$$$ rig onto its side.

Another thing to consider is that some day you might want to sell that beast and the next owner might not be thrilled with all the holes you put in his rig.

This boat tail ought to be a simple build. It would be shaped more or less like a doorstop. Compound curves are nice and all, but, a PITA to build. The doorstop's door would swing up like a hatchback. I guess you could have the ramp swing up to meet the hatch. I willsee if I can throw together a pic when I have a chance.