3.0L to 3.5L 24v SOHC Engine Conversion Updates ...
June 5th, 2012 The moment of truth has arrived in this little project. Seeing if it starts and runs. This turned out to be incredibly anticlimactic. Which, if you're installing a new engine, is probably the best way things can turn out. Even without exhaust the new Mitsubishi 3.5L sounds healthier than the 3.0L it replaced. The electronics seem to be happy so far. The only problem is the disconnected O2 sensors and one would expect the computer to whine about that.
The next step was to trailer the vehicle to the exhaust shop have the y-pipe and down pipe modified and bolted back on. This also went without a hitch, more or less. The assembly bolts up and doesn't appear to leak. It's good enough to get it somewhere that will do the job right but that's all. For $176 and about 1 hour of work you'd think they'd put some thought and effort into the job rather than just slap something together and call it good. Too bad for them. I won't go back and I'll make sure everyone knows what kind of work they do.
Now that the vehicle is legal on the highway again the tech drove it back to the shop so we could check out clearances. It's a good thing we did. Between the front settling and the longer 3.5L oil pan we had major clearance issues. With the vehicle sitting flat on the ground there's only .5" to .75" of clearance between the track bar and oil pan. Just enough clearance to get the vehicle back to the shop from the exhaust shop while going about 35 Mph but that's all.
Thankfully, the track bar is at the rear of the pan so there's room to modify the oil pan sump without interference from the oil pickup (too much). Once the modified pan is reinstalled and the dealership pronounces their work done the next step will be to change springs on the front and reclaim the 1" or so in height the vehicle lost.
June 13th, 2012 Wow. So, this evening didn't go so well. Everything was ready to go. Tech checked, double checked and then checked everything again, test drove it, gave it one last review and then started to drive it around to customer pickup and the alternator went south. I haven't decided if it doesn't want to come home or it just doesn't want to leave all its new friends at the shop.:) Anyway, too late this evening to pick up a replacement alternator from AutoZone© so it looks like I'll have to wait one more day.
June 14th, 2012 It's on the road! Finally! Step one of my incredible 'Two Step Process' is finally completed. It's really strange to open the hood and see nothing different. It looks EXACTLY the same as the 3.0L except it's cleaner. Weird.
After running it for twenty miles in stop and go traffic in 85 degree weather up to 45 MPH I fired up my OBD II scanner to check out the computer - my primary worry with this swap. Fuel trim, O2 sensors, etc. are all reading what they're supposed to be reading. The next step will be testing at highway speeds - 70-75 MPH - and higher RPMs. After about 100 miles of in town and highway driving, I've rechecked the Fuel Trims. It appears that they've shifted to an average of about -9%. While is is still within the ECU's ability to make adjustments it's not where I'd like it to be.
The only issue so far is the temperature dash gauge. For some reason it's reading higher than it should at a specific temperature. The sensors are the same for the 1997 3.0L and 2002 3.5L and the engine isn't running as hot as the gauge says so I suspect it may be due to the extension of the wire. At least that's my best guess at this point.
Performance-wise, it's great! The extra torque is definitely noticeable. It doesn't accelerate much differently from a stop but it's easy to tell that the engine doesn't have to work nearly as hard to get 5500 lbs moving. It is obvious that there's a LOT more low end torque. I can accelerate in fourth gear up hill starting at 2000 RPM. With the 3.0L that was impossible. The 3.0L just didn't make enough torque below 3000 RPM for a vehicle that weights that much. I can't wait to see how it does on the highway going over the mountain passes.