2ZR-FE camshaft swap

so I've decided to go for this mod. After reading the 1nz-fe Cam Swap | PriusChat thread, the mod seemed to work without any hiccups, even after 20k miles, according to @ToyotaJesus.

With the gen 3, I see no major changes that would cause any issues. They once again took one of their standard otto cycle engines, and modified the camshafts, pistons, etc, to create an Atkinson cycle engine. The only difference is they started with a larger displacement engine. Both will have a static compression ratio of 13:1, which is high, but there are a lot more factors that determine the actual dynamic compression ratio. The gen 2's with the swap seemed to have no issues with knocking.

I am still looking into the steps, but I believe I need to pull both the intake and exhaust cam out of a 2zr-fe engine, take off the valve cover, and replace the camshafts. It appears I won't even need to remove the timing chain cover. Of course, this will require premium fuel.

I have been getting some data from my car scanner app. I've got, temps, motor torque, 0-60 times, etc. Should be able to compare before and after and see what it actually changed.

Thoughts?

 

I have been looking at the Toyota parts catalog, and listed all parts identical to the 2zr FE (corolla) engine in blue, all parts that are different in red:

• Crankshaft: 1340137021
• Intake cam: 1350137030
• Exhaust cam: 1350237040
• VVT intake Cam gear: 130500T050 or 1305037040
• Piston rings: 1301137110
• Pistons: 1310137120
• Short Block assembly (bottom): 1140037140
  • Top of crankshaft sandwich (INCLUDES PISTONS, probably why this is different)
• Engine oil pan: 114200T011
  • Forms bottom of the crankshaft sandwich
• Block sub-assembly: 1141009322
• Head Gasket: 1111537061
• Head sub-assembly: 1110139725

It seems the changes to this generation Prius engine are similar to the 1zfxe. The pistons are different to increase the compression ratio, piston rings are different, new camshafts to allow for Atkinson cycle operation, and seemingly a new cylinder head. I cannot find individual part numbers for the cylinder head block. Since the VVT gears are the same, it should be fairly simple to attach the new camshaft to the existing gears.

Unlike the 2nd gen Prius, this car has VVT on the intake cam, which means the compression ratio must adjust while driving. It may even operate with a fairly high compression ratio at times from the factory.

Going to try to find some camshafts in decent condition from a junkyard and pull them next.

 

Ok here's an update: I've been busy with school, but now I've got a bit of time, I'm gonna start hunting for a suitable intake and exhaust camshaft. It seems to me that as long as I get the timing right, there isn't much chance I'll hurt the engine. Definitely gonna go with the highest octane I can get, similar to what Toyota Jesus did.

From what I can tell, the majority of the engine is identical to the 2ZR-FE, so swapping them out shouldn't be a problem. The 2ZR-FE would have a different compression ratio, so there would be no need to worry about knocking, it's just a lot of work. Also, since the prius will only rev to 5200rpm, you won't get the full 134hp, it will probably be more like 115-120hp. You will still get the increased peak torque, and just overall increased torque across the engine rpm range.

 

Oh yea, definitely. I was just commenting on SloCt200h's questions, if one were to replace the entire engine. The actual effective compression ratio and what the computer chooses to do with the VVT is a pretty big unknown in replacing just the camshafts.

 

I have pulled camshafts from a 2009 Corolla, they look to be in good shape, just need a bit of cleaning. Going to try to install them today, and see how it goes. I took both the intake and exhaust cams, just so I can compare the profiles. Unfortunately, the corolla has VVT on both the intake and exhaust, while the prius only has VVT on the intake, so most likely I cannot use the exhaust cam regardless.

 

ok another update:
I was able to get the engine apart, and install the cams. I essentially followed guides on a head gasket replacement, and used the repair manual for reference. It really isn't that hard of a job, and SHOULD be doable in 2-3 hours. However, while torquing down the bolts, I set my torque wrench just below the minimum value, and eded up snapping a bolt. UGGHH. After going back and forth, I decided that using a screw extractor wouldn't be worth it. There are m10 threads Toyota put in the lower portion of the camshaft carrier, which were unused (the bolt I broke was an m8). I decided to put an m10 bolt through those threads, attaching the upper and lower portions of the camshaft carrier. This leaves no attachment to the head below, but because the construciton of the lower carrier is quite beefy, and
all the remaining center bolts attach to the head, I don't think this will cause any issue.

Below, you can see the camshafts compared. The intake camshafts are the same shape, but you can see the profile has a different shape, giving the prius a longer valve duration. I measured the max cam diameter, and found they are slightly different. The corolla max diameter is 42.93mm, while the prius is 41.9mm. Because most components are shared between the engines, I don't think this will be an issue, but I'll manually turn the engine to make sure.

From tracing the corolla exhaust cam profile, I have concluded that it is essentially the same shape as the prius exhaust cam. I plan on taking a few more measuremnts tomorrow.

Corolla intake cam in the middle, prius intake cam on the right:


You can see the replacement bolt in the center:

 

Tightened everything and closed the engine, engine is turning freely with no issues. Gonna try to start things later today, so here's to hoping that there are no more issues.
I also took some measurements of the camshafts:

Prius Intake camshaft:
max diameter: 41.9mm
min diameter: 36.9mm

Corolla Intake camshaft:
max: 42.9mm
min: 36.9mm

Prius exhaust camshaft:
max: 43.4mm
min: 38.5mm

Corolla exhaust camshaft:
max:44.4mm
min:38.5mm

Clearly, the camshafts both have the same minimum diameter, but both corolla shafts have an extra 1mm of lift, which is 20% more than the Prius. Installing the corolla exhaust cam would likely only help improve performance, but I don't want to mess with swapping the sprockets right now.

 

ok, things seem to be working, engine runs just fine. Drove it around a little and definitely noticed more torque from the engine. Engine also seems to be a bit louder, and seems to charge the battery quicker. I'll have to do a bunch more driving and some 0-60 tests to confirm this.

I was doing percent of the camshaft lift, so max diameter-min diameter. for the Prius it's 5mm, for the corolla it's 6mm

 

So I have done several 0-60 tests, and haven't gotten anything under 10 seconds. This is disappointing, as it definitely feels like it has more torque, especially at lower speeds. I have been recording data and comparing, and I noticed that MG1 never has a torque lower than -40Nm, and MG1 at negative torque values seems to be what is resisting the torque of the engine and allowing that power to go straight to the wheels.

This may be a software limit, which means that no matter what you do to the engine, you won't be able to make the car faster. This is disappointing, but I guess that's just safety limits protecting the hardware.