Gen 2.5 3.8 Swap
- Thread starter Atrais
- Start date
even up here it would be 5 years away. coffeegoat
Adventurer
The ECU was the biggest hindrance in my mind to doing any kind of major upgrades to the engine - you just end up doing so much software customization that unless you're doing it for fun it's opening up a can of worms you have to live with every single day...
There was a thread a while back on 4x4wire where someone put a supercharger on a 3.5, it was awesome, but you could tell the guy was retired and loved working on his rig, I just want it to generally work, hence, it'll stay stock for me.
That's probably also why the aussie aftermarket stuff mostly runs on piggyback ECU's so you can leave the factory stuff alone and add inonly what you need.
There was a thread a while back on 4x4wire where someone put a supercharger on a 3.5, it was awesome, but you could tell the guy was retired and loved working on his rig, I just want it to generally work, hence, it'll stay stock for me.
That's probably also why the aussie aftermarket stuff mostly runs on piggyback ECU's so you can leave the factory stuff alone and add inonly what you need.
Toasty
Looking for that thing i just had in my hand...
The ECU is a minor issue with swapping a 3.8, considering the fuel maps exist already and the ECU is EEPROM. Unlike Franks supercharger install or say MIVEC install.
Toasty said:
EvoScan is a logging program. ECUFlash is used for re-writing the flash files. EvoScan is cheap and can run off a generic Chinese OBD2 cable, but it can't actually change anything. ECUFlash is free, but requires a $170 programming adapter to read and write ECUs.
Toasty said:
It's flash, not EEPROM. The 3.8 has a knock sensor, so the fuel and timing maps are set up very differently from the 3.5. It can be done, but it's more complicated than the copy-paste job you're making it out to be.
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Swank Force One
Adventurer
None of the evo/dsm guys i've talked to will touch this thing with a 10 foot pole either.
The Evo and DSM stuff was already mostly in place from a hardware and electrical perspective. Their main hurdle was figuring out the software side. That's something they did spectacularly. The trucks take a lot more wiring and mechanical modification to swap in the newer engines and electronics. Is it really worth the effort for 3/10 of a liter of displacement and a slightly more low end torque?
I'm putting a 6G74 and a reflashed 98 Montero ECU into my Mighty Max, but that's only because it's an easy 50-60hp bump up from the thrashed out 12 valve 3.0 I have in there now. I had originally planned to go to a 3.8, but I just don't know if it's worth the extra hassle.
Swank Force One
Adventurer
I dont think that's how people are approaching it. We're talking about running the 6g75 on 6g74 ecu/harness/sensors and having the 6g74 ecu flashed/tuned to make it safe. I'm reasonably sure i could make it safe with just an FPR and would be ok with installing a basic standalone if necessary, but would be way happier if the stock ecu could be easily retuned for the smallish changes.
The 6g75 is generally a more robust motor, more power is more better, and my 6g74 is generally extremely haggard. Costs the same for me to get a 6g75 and they're more plentiful.
The 6g75 is generally a more robust motor, more power is more better, and my 6g74 is generally extremely haggard. Costs the same for me to get a 6g75 and they're more plentiful.
How do you figure the 3.8s are more plentiful? I thought the 3.8 car blocks were missing enough motor mount bosses to make it tricky to fit one into the truck. People have the same problem putting them in 3000GTs. All the 3.8 Montero engines I've seen have been pretty pricey and availability was spotty.
If it helps, I've got ECUs from a 4 or 5 different Monteros and Montero Sports, including a 3.8 gen 3. I haven't dumped the code off the 3.8 yet, just because I've got too many other things on my plate right now. But if someone is far enough along to need maps, I'll see what I can do.
If it helps, I've got ECUs from a 4 or 5 different Monteros and Montero Sports, including a 3.8 gen 3. I haven't dumped the code off the 3.8 yet, just because I've got too many other things on my plate right now. But if someone is far enough along to need maps, I'll see what I can do.
I generally am able to find 3.8's with lower mileage for the same price as comparable 3.5's. I'm talking about the 3.8 Montero motor (non-MIVEC btw). Sensor swap, I THINK something has to be done with the cam trigger plate and some drilling for a couple of the mount holes and it's good to go. Since you'd be tuning it anyway, I'd just use the 3.8's IM, swap on a different throttle body (maybe a q45 or the like, just weld on a flange and port to match it) and tune it from there. Not too bad, you get a little extra displacement, and a better flowing set of heads. Could also chuck some RPW cams in there if you really wanted but *shrugs*.
lordtrunks
camp loser
If you use the gen 2(2.5) heads it is about as close as you get to bolt on power in a truck that already has a 3.5 but it bumps the compression way up like about 12:1 possibly even 13ish:1 you need to either retard the timing back or swap in a some lower compression pistons which is how I would go then have the injectors cleaned and flow matched get it all put together and then drive it and watch log any lean spots BTW the montero 3.5 has a knock sensor the sport does not
Swank Force One
Adventurer
I'm not sure how they're more plentiful, they just simply are in my area. I wouldn't pay for a Montero 3.8, i'm capable of doing the few hours total extra work to dump a car 3.8 in a Gen2.5. The mechanical stuff is cake, it's just running it properly that seems to be the issue.
I'm not far enough to need maps, nor will it stop me if it comes down to it. I'm personally ok with throwing a Haltech at it if i need to. Would rather invest in that than dump money into my 6g74. Once i handle another project or two ahead in line, then i'll grab a 3.8 out of the junkyard to rebuild and clean up on a stand. Once it's ready to go in i'll holler and yell and see if maybe we can figure out how to get 3.8 maps on the 3.5 ecu?
Atrais said:
That's only if you're using the newer 3.8s from the cars. The 3.8 Montero was a transitional model. It used partial CANbus, drive by wire, different ignition, but didn't get the high resolution trigger wheels or coil on plug setup. The cam/crank trigger pattern is the same as any other Mitsu V6 going back to the early 90s.
So the engine and sensors should run fine on a 3.5 ECU if you install the 3.5 throttle body, PTU and coils.
lordtrunks said:
So you're saying use the 3.5 heads on a 3.8 block to get a CR bump? Interesting. Seems like it'd be really touchy about knock though.
lordtrunks said:
I know the DOHC does, but are you sure about the SOHC? I don't remember seeing it in the ASA diagrams.
Swank Force One said:
That sounds great. I might eventually be interested in a Galant or Endeavor 3.8, but for now I just want to get the 3.5 running. I'll still do what I can to try to get the 3.8 maps adapted over. I'm hoping to clear my plate and start putting some dents in this project in April.
coffeegoat
Adventurer
Well this thread just went way over my head, but I do know that the 3.5 came with a knock sensor on the 2001 Gen 3 montero (NM model) which is a SOHC. There are some pictures of it in my build thread.
PA_JERO
Adventurer
Does anyone know where to find the swap oldcolt did, using a 3.8 block and dual cam heads? Or is anyone here even familiar with oldcolt? I'm pretty sure that swap or build happened before 4x4wire was a thing. I have thought about taking a chance on this, but I would like to find someone with a bare 3.8 block to put on a stand for some detailed pictures. This would also give a good reference on whether or not using 3.5 SOHC heads on a 3.8 block would actually work, especially knowing 3.5 SOHC blocks are different than 3.5 DOHC blocks.