subaru FB25 engine interchange

I have been driving around and put about 500miles on my 2017 Forester engine and I gotta say it's been great. My catalytic converter was bad so I replaced it, I assume the oil burning 2011 engine killed the cat as it only has 100k miles on it but only 50% or so of the honeycomb was still intact. 

Since I just have the 2011 TGVs hooked up in the engine bay I do have a pending P0171 code that comes and goes that I believe it due to the extra lean condition during cold startup but never trips the CEL. I was able to pass emissions test here in PHX, AZ and am getting 23-25MPG mixed driving. Cold start up is no issue either, only very slightly rough until warm and probably takes a bit longer to warm up than if the TGVs were in service.

Last thing I need to do is adapt the TGV magnets and actuators to the 2017 intake and looks like it's not going to be an issue so I'll keep following this thread or if I get time just jump on it and do the swap but I'll swap pins 4 and 5 first to verify the valves will turn in the opposite direction.

The black 2011 Forester magnets are mirror image in their placement of the magnetic North and South poles. I suspect they will need to be swapped left to right when moving to the Legacy manifold because of the direction reversal, but there have been enough surprises here that until I measure the voltages . . .

I thought I would do this yesterday, but still could not stay awake so here it is now.

For the 2016 Legacy manifold manifold with the magnets swapped out, the distance from the edge of the manifold case to the bottom of the black magnet is about 5.15 mm so about an additional about 2.1 mm is needed to correctly position the magnet over the sensor if the Forester actuator is reused.

The 5mm ID fender washers I got at ACE Hardware are about 1.15 mm thick  so two should be about right. I will check the absolute distances to make sure the magnet and sensor don't rub. I can sand the thickness down a bit if necessary.

Edit

For both the 2011 Forester TGV actuator and the 2016 Legacy TGV actuator the distance from the sensor up to the mounting surface is about 14 mm. The raised ridge makes it hard to be more exact.

With no shim washers added yet the distance from the 2016 Legacy manifold to the TOP of the black magnet is about 10 mm. So, with 2 washers it should be around 12.25mm which seems to leave plenty of clearance.

Below is a picture of the 2016 Legacy manifold with the black magnet and two shim washers installed. It measures about 7.5mm to the bottom of the magnet and 12.5 to the top of the magnet, give or take. Looks good mechanically.

I will investigate the magnets and clocking angles vs signal voltage next.

More surprises and some progress.

I accidentally grabbed the 2016 Legacy/Denso TGV actuator instead of the 2011 Forester/no name actuator and confused myself but good before I figured it out. DOH! They really do operate quite differently.

I happen to have two magnetic probes, one with the South pole out and the other with the North pole out so they stick together.

I previously used the two probes to test the sensor signal reaction to magnetic North and South poles.

However, in addition to the magnetic pole there is also magnetic field strength which depends on the individual magnet and the distance from the sensor. I guess the probes are so strong that they overwhelmed  the sensor if I got them too close in my earlier testing because taping the actual black or white magnets to a plastic pen and slowing spinning them over the sensor produced slightly different and more understandable results.

Using the 2011 Forester black magnet and no name TGV actuator the signal is 5Vdc with no magnet present or with one end of the magnet-on-a-stick over the sensor and abruptly drops to 0Vdc if the magnet is turned even a small amount and then stays at zero as the rest of the magnet is turned over the sensor, including the other end. The Forester computer seems to receive only two signal values, 5Vdc for fully open and 0Vdc for any other position.

Using the 2016 white magnet and Denso TGV actuator the sensor signal is 1Vdc with no magnet present and seems to vary over the range from about 5Vdc down to 0.8Vdc as the magnet is turned. The sloped top of the white magnets vary the distance/field strength too. The Legacy computer seems to receive an analog signal proportional to how far open the TGV is, but never very far below 1Vdc. I may revisit this later to see if anything useful can be done with it.

For now, it is clear that moving the black Forester magnets and no name TGV actuators to the Legacy manifold is the way to proceed. The clocking angle of the magnet relative to the shaft needs to be set so that the correct end is over the sensor when the TGV is fully open. Remember the two black magnets are mirror image so be sure to use the correct one for each side when installing the shims etc.

Next I will finish filing, shimming and clocking mine and verify the voltages and whether the black magnets need to change sides or not.

In reply to Skenton :

Thanks for the updates! Still following as I haven't yet swapped mine, as I've been replacing CV boots and planning to install a lift soon.

I do now intermittentaly get a P0171 (running too lean) code when I am ideling the engine more than usual, I'm sure it's from not having the TGVs operational. Otherwise the 2017 engine is doing great with no measurable loss of oil level running 0w-20 after nearly 1000miles.

In reply to Sodapopdave :

Did you have a chance to swap the power pins to check direction?

In reply to Skenton :

Nope, havent swapped the pins yet - I won't have time this week as we are heading out camping for New Years but I can next week and update for sure. 

In reply to Sodapopdave :

The service manual describes testing the TGV motor moving both directions by reversing the 12Vdc +/- inputs on pins 4 and 5. So I expect the pin reversal will be fine. The interesting question is what the computer does if it is not happy. Leave things in place and throw a code, try reversing directions, or something else.

In reply to Skenton :

Nice find! I'm certainly no electrical expert but I assuming the computer wouldn't know if pins 4 and 5 are swapped so I think it will work just fine once the magnets are clocked properly but that's just my guess. 

In reply to jdf60 :

I was looking at oil pans on Ebay and they claim the Forester and Legacy 2.5 oil pans are the same for 2013 and 2015, for what it is worth. Could you comment of the difference you saw?

Different outline? Same shape but additional/missing bolt holes? Different bolt pattern all together?

I am considering upper an oil pan swap to get rid of the CVT cooling port on the upper oil pan instead of capping it and want to understand any lower pan difference I might need to deal with.

Edit

It turns out there is a lot more variability in the upper oil pan than I was expecting. Looking at the casting numbers and trying to determine compatibility of 1B5 2B5 3B5 etc. Search for the document below for more details.

In reply to Skenton :

Sorry I've been offline for a while and forgot my login  info. 
If I remember correctly the pan used a completely different shaped gasket. So it had a different shape and bolt pattern. I'll look again next time I'm under there to be sure. I still have the 13 forester engine also so I can compare. 

Hello All!  This is a great thread...and very timely.  I have a 2015 Forester (FB25B w/CVT and PZEV) with a seized engine.  I have the opportunity to buy a 2018 FB25B with 13k miles on it....and wondering if any of you can give me either the push toward to away from trying this swap.  It seems like swapping some of the components over is pretty clear....but the TGV seems to be the issue that get a little tricky.  Anyone want to offer an opinion on if I should try this?  Here are the engine codes:

FB25B CYHZF (2015 seized engine)
FB25B XYHUA (2018 donor engine)

Also - while I'm here - any thoughts on the ability to swap CVTs?

TR580GH ZAB
TR580GH WAA (donor transmission)

Any advice would be greatly appreciated!

Steve

Is anyone still viewing these threads?  This is my first time here...and would love to know if there's any activity here.

We are around, just not active right now. Several of the "recent" folks completed their swaps and are checking back to see how I am doing with the TGV mods. Health issues sidelined me for a while from getting to the bench or garage but hopefully I can at least get back to the bench and nail down the magnet stuff soon.

In the mean time looking at pictures of upper oil pans and CVT cooling diagrams on a tablet while flat on my back was something I could manage and contribute.

The engine swap looks doable, I doubt the transmission is. The problem is the computers "know" about what they control and about each other. Staying with the computers that came with the vehicle is the only safe bet. We treat the donor engine as a long block and swapping parts fools the computer. Except for the TGV issue, which has a work around. I have not seen anything about CVT swaps.

What did the donor engine come out of? Different vehicles have different engine changes at different times.

I guess I need to update and reposted my summary document to include all we have learned about late model engine swaps.

In reply to jdf60 :

https://parts.subaru.com/p/subaru__/Engine-Oil-Pan/69985986/11109AA253.html

Here is a lower oil pan compatibility list with part numbers and supersessions if that helps

https://parts.subaru.com/p/Subaru__Forester/Engine-Oil-Pan/60249902/11109AA232.html

This one is for the Forester with the 2.0 instead of 2.5 engine above, it confused me for a while

In reply to Skenton :

THANK YOU SO MUCH FOR RESPONDING!  I really appreciate it.  I have access to a donor engine out of a 2018 Forester 2.5.  I have pics of the engine....and I am wondering exactly what you said....could I use the 2018 as a long block (block, heads, etc.) and use everything above the heads up (intake, egr, etc)?  Could I just swap over all that stuff from my 2015 Forester FB25B to the 2018 Forester FB25B?  Based on what I read, I might even have to switch over the timing cover.  I was looking at the 2018 FB25B and it doesn't even look like it has the TGV valves at the base of each intake arm....like the 2015 FB25B does.  Any thoughts?

The intake is different and cannot be swapped, hence the TGV issue. The 2017+ Forester FB25B became more like the Legacy 2015+ engine. The Rocker covers/coils might need swapping. The timing cover fits but the electric power steering has different pulleys than the older hydraulic variant so it depends on what you have. Depending on years the cam plates may need swapping, don't recall exact switch dates off hand.

Pics of TGV stuff?

Does anyone know if I can swap an FB20 into a 2014 forester with MT 6SPD. Would I need to use same year FB20 from a 2014/2015 legacy? Thank you

In reply to Maloney71 :

Did you mean FB20 or FB25? Legacy's have an FB25. In the USA market, FB20's are in the Impreza and XV. However, the JDM Forester (japanese market) has the FB20.

That said, I have never swapped a FB20 into a forester, but here's a YouTube video of someone who put an FB20 into a 2012 forester. I would imagine it would be similar for a 2014, but I can't say for sure.

https://www.youtube.com/watch?v=fX1djB62YMM

For anyone out there doing a similar swap, I just swapped a 2017 Legacy FB25 into my 2011 Forester 4 weeks ago. I built a simple harness extension so I could mount the 2011's TGV's off to the side and plug them in. Have run it for 500 miles now with no codes or issues at all.

Here's a recent YouTube video I found to be quite helpful, it outlines all of the steps necessary to do the swap.

https://www.youtube.com/watch?v=AZY9B3sLO0U

In reply to obsequious_knight :

That is  great video. Thanks! It really help for folks to see and not just read about it.

https://parts.fuszsubaru.com/a/Subaru__Forester/49223576__6027904/OIL-PAN/S13-031-02.html

According to the Subaru document about the updated FB25B upper oil pan casting they are VIN specific.

And indeed for 2014 Foreste4s as shown above 11120AA230 is for MT MODELS and 11120AA250 is for AT/CVT MODELS, meaning the addition of the extra coolant port or not. A bit of clarity!

In reply to elite150deluxe :

Did you decide to go for the donor engine out of a 2018 Forester?

If so, any news/problems? To date, 2017 was the latest donor I have heard of so curious about 2018. In 2019 the Forester changed from FB25B to the FB25D with direct injection. Legacy followed in 2020.

In reply to Skenton :

Any update on the magnet mods?  Ours has become my daily driver so I can't really experiment on it at this point. 
I did try to plug the original tgvs into the wire harness to trick the ecu and I still got both banks stuck open code. And I am pretty sure one original  tgv is bad because it doesn't move at all when I turn on the key.  But I would think the other side wouldn't throw the code with the dummy tgv plugged in and turning. 

Thanks for prodding me about this. I will break out the box of TGV parts tonight and try to pick up where I quit.

I recently got some new lung meds and am doing better. Knock on wood I can get back to the engines soon. They are sitting a few feet apart waiting for me to swap stuff.