I used to live in Oregon and work at a strange little mom and pops tire and service center. We repaired RVs, and all sorts of other odd vehicles nobody else wanted to work on. I was fascinated with the "house" layouts inside the RVs and always enjoyed taking a peek inside them. But I hated moving the big rigs around, so actually owning an RV never really crossed my mind. Until I met my first Toyota Dolphin! It was a hard vehicle to forget. It was a SUPER weird story, and it was pristine. And it had the most evil "wheel" on it I ever encountered over the years, other than some widow makers and a Humvee H1 with the self inflating setup. The Toyota wheel probably gets first spot too in that list. It was a single wheel, with two tires on it. Turns out it is what's called a "foolie" and is actually what almost did the Toyota RV makers in. If you find yourself with an older pre 1986 Toyota RV and you have a 5 lug "dually" wheel on the back, look up Toyota RV Axle recall and get that crap off of there ASAP! But that's not the story here.

The owner had just bought this thing from some tweekers on a bender. Kinda sounds like they had either been inspired by, or were the inspiration for, Breaking Bad. Stuff was about to be done to this poor thing, bad stuff. He saw it and decided he wanted to rescue it. Asked how much they wanted. $3,000 they said. He pulls out his wallet and makes a show of counting money. And said something to the line of "I have that in cash right now, minus a zero." They said "Deal!" and snatched the money. I think there was a brief time where he was concerned he had lost the $300, but they produced a title and signed it over.




He drove it away not even waiting to go get temp plates. He was a bit worried they would figure it all out. I think he actually stopped at the shop on his way taking it home. The tires were SCARY bad lol! Anyway,s as I loved to do, I asked him if I could look inside. He obliged, and I did. And fell in love! The layout on these Toyotas RVs is amazing for as small of a footprint as they take up! It was the first chance I had gotten to look into a Toyota. I was smitten. I most likely got to drive it too (at least around the lot) as it stuck in my mind how comfortable it was to drive and maneuver. I kept an eye out for more and saw a few around I got to look at closer. Another 1-2 might have made it to the shop to be worked on.

But as I discovered, they were not very common. For years after that, I combed want ads looking for any Dolphins for sale. When I found any, they were too far away or too expensive. Too expensive was a pretty low number too, as I had no real "need" for an RV. I could live out of one, but I am not exactly a minimalist either. I moved to Florida, life went on.

At some point I figured out that the Dolphin, was not the only Toyota based RV made. Probably by accident and not finding "Toyota Dolphin" hits, but coming up with "Toyota RV" ones. I eventually stumbled across a local ad for a Toyota Mini Cruiser. The timing was right too. I had just sold my long term project car, and a storm had damaged another car. There was money for it. We bought it!

And my schooling in all things RV, and some things Toyota, was about to get real... I have been wrenching for 25+ years now. But this was new territory for sure. Starting with it dying right after we paid for it and the title was signed over. In the normal "mechanic buys perfect car, and has to get it towed home" scenario.

 

Well first on the list was the dead battery got recharged. And alternator was not charging. I think I may have done this there before giving up and towing it home. Oh but wait ya can't test an RV alternator like you can a normal car one, there is an isolator. Replace alternator, still not charging. Blip throttle, charging. Not sure if to this day I could correctly test an isolator setup and get, accurate numbers... And I am not sure if that original alternator was actually bad. There were multiple issues like a dead house battery that was still connected to the isolator setup. So it might actually not have been charging the engine battery, but trying to charge the bad house one... Meh I confuse myself years later trying to figure that out.

After a two week ordeal to get it towed the 40-50 miles home, finally get it home. Get battery, cables, and alternator sorted, and it dies again. less stressful at home, no time crunch to deal with. Fuel pump had died. No surprise 40ish year old pump with probably 10yr old gas. But there is a gotcha for sure! Simple job if you put it up on a lift and drop the tank. RV sides though make doing that in the driveway impossible, even on ramps.

Pondered this problem for a few days, then decided to cut a hole in the floor. Measured more than a dozen times carefully trying to work out where to drill and find good reference points inside/out I could go by. When I finally drilled the 6" hole, I was off slightly. I could have centered it maybe 1-2" better, but it was good enough! It was a small struggle to get the pump and sending unit out, had I been that 1-2" over it would have been butter. I solved the hole with a marine access screw down cover. I had to enlarge it slightly, and centered it a little better when I did.

I got to know the little beast. And the more I worked on it, the more I loved it! I would not start it for months, and the engine would fire up each time without even the slightest hesitation. Toyota built it WELL. I had some issues early on, forget exactly what, but I almost 'squirted it at the very beginning. Doing so was always pretty high on the list. But it ran, so I left that alone to tackle the other projects on it. ALL the lights had to be replaced, except for the front OEM turn signals. DOT markers were all damaged, burnt out, or missing. The RV taillights were destroyed and I couldn't find easy replacements.

Plenty of other projects had to be sorted out and systems verified or repaired. It sat. For 2 years... Finally the wife had enough and was threatening to sell it for the 4th or 5th time. And I just wanted to actually go drive it! So I made the final push to get all the lights fixed and working. Now that 2yrs I didn't spend completely idle on it. I collected a LOT of parts and made plenty of other repairs to it.

A BIG upgrade that was basically a deal breaker for me, was getting 6 matching wheels. These came with the Toyota 5 lug on the front, and 6 lug dually wheels on the rear. Dumb. The later V6 ones came with matching 6 lug all around, but again these were always hard to find for sale and basically never seen in a junkyard. But my spy network paid off and my boss actually stumbled across one. He FaceTimed me to show me. And told me to take a "sick day" the next day and even lent me his truck to actually go get everything. Let me tell you, that was an ADVENTURE! But not only did I rip the whole front end out of the junkyard truck, by that evening I had ripped the front end off of mine, and replaced it with the neused parts from the junkyard. The front 6 lug conversion requires replacing the spindles/hubs/brakes/and a couple other random bits.

Finding tires, that was fun... It takes a weird size that took multiple tried to find "in network" or my former boss might actually just have been too lazy to really look. Tired were replaced. Rear equalizer system made, so a normal car 4 sensor TPMS system could be utilized.

Finally all had come together and Monday it went for its first proper shakedown drive! There were two big issues. The first, ZERO power. The second, smoking hot rear brakes. Easy to conclude the rear brakes were locked up causing the lack of power... They weren't. Turns out lack of power was due to timing being something like 40-50 advanced. How this engine rans so smoothly that far out, baffles me.

Not sure what the brake issue is yet, if there actually is one. But when I upgraded to the larger front calipers, I didn't change out to the correct master cylinder. I may have been lazy and only bled the front brakes too? That project was a little while ago. I did figure out and purchase the correct master to use, so that is in the "waiting parts pile" at least. There is also the LSPVB in the back. It is set for a balanced front/rear about in the middle. But it is already made essentially useless by the additional weight of the RV house. There is a long thread on the Toyotamotorhomes.org forum about the issues that thing causes.

Well I figured since I have been over here posting threads and asking questions, I would at least share the project and its progress! I have a build thread over on the Toyhomes forum, but it is more focused on the RV aspects of the build. (I can link to those if anyone is interested). I guess over here I will focus on the more "Toyota specific" aspects to the build. And especially focus on the next stage of the build, MegaSquirting it, and my process for doing so. I will go into more detail on that and why in a future post.

EDIT: I will go dig up or take some pictures for here shortly. Made a mess trying to type on the compute,r but upload pictures from my phone lol.

 

Sorting out new wiring diagrams is always fun! Good preparation here is the biggest trick to making the install go smoothly later on. There were some good resources for this one at least. DIYAutotune: How to MegaSquirt Your Toyota 22RE But their diagrams were a little sparse and confusing. So had to actually dig out paper and pencils for this one.



A couple things I learned over the years of doing this is to maintain consistency, and DOCUMENT EVERYTHING. I use the same templates, especially for the wiring pinouts. A drawn out wiring diagram would be nice, but a detailed plug, pin, wiring colors, and explanation is actually much more useful. Once sorted out on paper, I put it back into my digital template on the laptop.



Exploring my ideas and thinking about the best approach to utilize the mostly empty 22RE case. I ordered some terminal blocks. Unfortunately then I sat down and sorted out just haw many I needed. They are a little on the big side. I went with the 15 amp blocks. Probably could have gotten away with the 10 amp guys, and they would have fit better in the case. Oh well. I will see how these work when they arrive tomorrow.



Soldering up the DB37 plugs is probably the most tedious part. And super easy to do badly. Quality wire is critical too. For many years, I have exclusively used GXL wire from KayJayCo But the materials needed to build a good harness are pretty steep. With plugs and heat shrink, the average harness could easily climb past $400. Just for materials. This time I used wire bundles from DIYAutotune. The quality of the wire insulation seems just a little bit lower, but the printed labels is very nice. And the price is defiantly right. Most likely I will have to order another pack or two if I actually go and build the whole engine harness from scratch. For now, this is just an adapter/extension cable. I am leaving the factory harness in play.



All that is left to do is to put the ground wires in and then decide how many lines got through, or utilize the terminal blocks. Leaning towards all of them passing through the blocks, then I can have quick and easy test points.

I need to clean off a few components from the OEM plug and PCB. There are a few on it that could cause for some interesting trouble shooting... I left the PCB and slicked it with a Dremel to have the plug better supported and to have something to screw down to the case.

 

After a lot of thought, I decided on this for the location of the MegaSquirt. I was going to put it where the factory ECU was, but it would require surgery to the body sheetmetal to fit it in there. And I would have had no place to hook in additional stuff or customize. This is a pretty decent compromise.



The next part , soldering to the ecu plug and installing the blocks, should go a lot quicker. I have to verify a couple details of the factory wiring first though. I am optimistic that it might even power up today for the initial tests.

 

So yeah, when in doubt ALWAYS triple check wiring. Especially when reusing the factory harnesses. The wiring diagrams and fusebox labels are misleading... The BATT pin on the 22RE plug is supposedly powered up by the EFI fuse. So I thought it was odd that the DIYAutotune pinout was calling for using the B/+B1 pins instead. So I with a test light and the new breakout case installed to see what was going on. The DIYAutotune diagram was correct. Looking at the fusebox, the EFI fuse is a 15 amp one. 15 amp is excessive for just the ECU... MS only calls for a 2 amp fuse on its pin 28 switched power feed. I need to figure out what else is being powered up on this fuse. Engine has a separate 15 amp and Ignition has a 7.5 amp. Having trouble finding decent fuse diagrams for this. I suspect the fuel pump might be powered up off that fuse.

For now, I will just solve this with a simple 2-3 amp breaker or fuse in the breakout case. But doing any real upgrades on the system, is going to require a second fuse box. That brings me to the main goal of this project though.

So why even bother with Standalone EFI in an RV???

Disclaimer: I don't want this thread to turn into another "it won't work debate." Simply put, it WILL work. But how much remains to be proven. So this thread is about proving this. And figuring out how to get there.

Probably the biggest reason to go standalone is simply, because I can and it is FUN to do! But that isn't a good enough excuse. At first glance it seems a foolish choice. Lets power up a heavy RV with a small little 4cyl engine. But these RV's weren't as heavy as most of the day, and the little 2.4L 22RE wasn't as little. Yes, the 22RE powered Toyota motorhomes have a reputation for not being the fastest. But they had something else NO OTHER RV back then, and very few even today can boast about. Good fuel economy! There are plenty of reports on the Toyotamotorhomes forums of 13-16mpg with more than a a few claiming to have hit as high as 22mpg.

Over the years I have done a CRAZY amount of standalone (mostly MegaSquirt) installs. I discovered that a side effect of many of these installs was actually getting MUCH better fuel economy. Oddly, most tuners only tune for power and don't bother with the cruise sections of their maps. Older ECU's with narrowband oxygen sensors also were never tuned for much leaner than 14.7. The oxygen sensors weren't capable of safely controlling lean conditions. But at cruise, most motors don't care if they are running lean, as long as they can change that as soon as the throttle tips in or the engine load moves into a power band. The AFM flap vane meter in our Toyotas isn't fast, or sensitive enough to do this.

So it is actually possible to have power, and get good fuel economy. I am not sure why most tuners ignore this. But you can quickly tell they have, just from looking at the AFR target tables. Even pro dyno tuned maps I have come across RARELY show any attention paid to this. The tools are already there, so why not use them?! The modern standalone ECU's are all fast enough with enough resolution in the maps. And all of them utilize wideband oxygen sensors that can run in the lean ranges safely.

My goal isn't that crazy, I want to see a fairly consistent 20mpg. I do know I won't ever be able to accomplish this on all stock Toyota EFI components. The AFM vane meter is the first thing that has to go. Removing that alone, will give a nice performance bump too. Experience has taught me that a significant performance improvement will come from full 3D tunable igniting maps alone. In fact even more than fueling. We put a 'squirt on a Jeep with a Holley 4 barre,l just to replace a burnt out ignition module, leaving the Holley on it. Just changing out the ignition controller, got us an almost 6mpg fuel economy bump up! And it felt like a whole new vehicle.

A turbocharger setup might be in the future for this too. When sized correctly, a turbo can also greatly improve fuel economy in the off boost areas. Much more effective use of the avalible resources. But this won't be the first stage... It gets too deep into the "spending money to prove a point" category.

Another goal of this is simply to prove that modern EFI can GREATLY improve results on older systems like ours. But in the end if I make crazy claims that I am getting 30mpg on a Toyota RV, who in their right mind will believe me? Unless, they can follow a simple recipe and repeat my results for themselves. And no, probably won't see crazy numbers like 30mpg, but again I think 20mpg is easily reachable.

To reach 20mpg consistently might be doable with a few changes. The AFM meter, as mentioned, needs to go. The oxygen sensor upgraded to a wideband. Fuel injectors upgraded to more modern high impedance ones with better atomizing multi hole spray patterns. A slight fuel pressure increase will probably be needed to effectively utilize these. And while I will initially retain the stock distributer, I think heating up the spark will make a difference. Future stages are likely to see the ignition completely redone.

Currently though, the only Plug and Play option for our trucks is the DIYAutotune 4Runner/Pickup 22RE/22RTE MSPNP Gen2 Plug and Play ECU At $799 plus about $199 for a wideband, this makes an easy to follow recipe pretty expensive. Few, if any, would spend that much to prove I am wrong, or believing I am right just to get slightly better fuel economy. MegaSquirt has come a LONG ways since it first came out on the market 21 years ago. But there are also no $149 ECU's still available... MegaSquirt used to be very grassroots, but it has grown up to become a serious contender to the big names in EFI.

Over the years I have seen a lot of MegaSquirt installs dome badly. Probably half of the ones that came to me, were because the owners had failed in their own attempts. So perhaps the $1000+ for a plug and play solution starts to be more reasonable. But for those willing to put a little time in, there are still some cheaper options available. There is a new grassroots system out there, Speeduino. It utilizes the same tuning software MS does. And my understanding is that its firmware is also loosely based off the MS stuff. The best part is that you can buy premade or DIY Speeduino ECUs that would put a n EFI conversion like this back into an affordable bracket. Cheaply enough that I might try one out just for the amusement factor!

This is a the main reason I went with utilizing the factory harness, even with its limitations. It would actually have been quicker for me to redo the whole engine harness from scratch. But then the whole idea of a "plug in solution" goes out the window.

Over the years I discovered that with a little guidance it is actually easier for most people to build a decent ECU, than a wiring harness. And in the end if the project fails, or more likely the wife decides to sell it out from under me, I can quickly swap back in the factory ECU. I am using a MS3 with all the bells and whistles. It is actually a good bit more expensive than the $799 PNP in the link above. But it was sitting on my shelf collecting dust, and I had nothing to poke at and keep my brain sharp.

Whatever the actual outcome of the project, it will be fun! I have never tuned a heavy vehicle like an RV before. And I have always wondered how it would differ from a normal car or truck. Plus it isn't something most would even consider doing. I can't imagine that the stock Toyota maps in my factory ecu are optimized for an RV application.... It is going to be fun no matter what the final outcome!

FINALLY, my Amazon package of terminal blocks has arrived! I am off to go do some actual work! I probably won't be powering this up tonight, the late delivery unfortunately cost me too much time. Still a fair chance for it to happen tomorrow.

Anyways next post update will be mainly pictures instead of lots of boring words. Nobody reads those anymore.