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Old 01-01-2017, 10:28 PM   #1
CMatos
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1986 325e Build w/ M20B25 Swap

Hello. Ive been a long time reader. I wanna start off by saying this post is pretty lengthy so beware. I recently purchased a non-running 86 325e. I purchased it with the intent of getting it on the track. It is a very solid car so I decided to invest the time and money into getting it ready. The entire car was in stock form when I purchased it. There is zero rust, but ALOT of maintenance was deferred, and parts had gone well past their life expectancy. The car could not be run due to a severe oil leak from the rear main seal.

I put a lot of hours into this car over the last month getting it to where it is now. However, I am still struggling to get it running properly. After pulling the motor, cleaning, re-gasketing, and re-installing, I ran into many problems. First, it wouldn't start at all. I traced this back to a faulty cps. I replaced both for good measure and it fired right up. Now running, it had a huge surging idle. I traced this back to the ICM. I replaced it with a used unit. Surging went away, and the ICV was operating correctly. During these tests, I also found a faulty TPS so that was also replaced.

Now I am at the point where the car starts and idles, but doesn't do much beyond that. If I open the throttle and hold it at the same spot, the rpm's will wander down then up rhythmically. Also, if I try to open the throttle in any type of rapid succession, it will respond to the first blip, then maybe the 3rd or 4th. In between it just doesn't respond at all. I checked fuel pressure at the rail, and all seems good. I checked compression and all seems good. I checked for spark and injector pulse, and all is good. I ran all of the Bentley tests at the DME and everything checks out. I am getting the proper resistance from the coolant temp sensor, and I also checked the cold start system for proper function, and all is well. Thermo time switch is working properly. I swapped in a good used DME, but no change. I swapped in a good used AFM, but no change. I tested main relay & fuel relay. All is good. I checked fuel pumps (both new), filter(new), and FPR(new). All is good.

Im at a complete loss at this point. The only test that has not been done on the car at this point is a smoke test for vacuum leaks, but I can't see this being the issue based on symptoms and being that I replaced all vacuum lines. I dropped the car off at a local shop last week for them to look at it just in case I'm missing something obvious and simple. No luck on their end yet and they've looked at it for 2 days. Im very frustrated because I was expecting to get this motor running with half this effort and cost. This engine honestly isn't worth this amount of time or money to fix. Im at the point where I need to stop the bleeding, cut my losses, and just pull the motor again. It looks like this is the route Im going to take if the shop doesn't return with any good news.

My next course of action is to swap in an M20B25 motor. I have been doing a lot of research into this swap, and it appears to be very simple and straightforward. I am trying to plan everything out now so I do not have to stop working once the swap begins. I don't want to realize halfway into the swap that I have a wrong part. So Im here looking for some information to make sure this doesn't happen. I also want to see exactly which parts I can salvage from my existing 'e' motor/transmission. I have a good idea for most of what needs to be done. I plan on putting in the 'i' motor, AFM, DME, and wiring harness. I understand that anything other than the 87 harness will need C101 pin #20 cut in order to prevent shorting the ABS circuit. I also need to rework C104. So here goes.


1) Can I transfer my 'e' single mass flywheel and new clutch kit over to the 'i' transmission? Im not sure if Ill get the 'e' motor with or without the transmission, so Id like to be proactive and just plan ahead for both scenarios using either transmission.

2) Can I transfer the new water pump? Im assuming it'll work so long as I keep the 'e' cooling system in place. I believe the 'e' water pump has a provision for a return hose.

3) Any issues with transferring the timing belt, tensioner, ignition coil, cap, rotor. Im pretty this is all fine, but I want to be 100% sure.



Some, but not all things that have been finished so far:

- Front and Rear Subframe powder coated with reinforcements welded in for differential, sway bars, and motor mounts.

- New polyurethane bushings- subframe, trailing arms, differential, and front control arms.

- New heavier duty motor and transmission mounts.

- Rebuilt shifter assembly

- New clutch kit. Resurfaced flywheel.

- New rear axles

- New front wheel bearing

- Bilstein Sport Suspension w/ H&R Race Springs.

- Rebuilt calipers, ss brake lines, rotors, pads

- New driveshaft flex disk & center support bearing.

- New complete SS exhaust (headers to muffler are dual pipe)

- Replaced ALL cooling hoses

- Replaced ALL vacuum hoses

- Cleaned/Tested fuel injectors

- Replaced TPS, ICV, ICM, AFM, DME, spark plugs, coil, wires, cap, rotor, timing belt, water pump, and accessory belts.

- Re-gasketed the motor (rear main seal, oil pan, valve cover, head gasket, rocker end seals, intake/exhaust manifolds, throttle body, etc)


If you made it to this point, then I appreciate your patience and time in reading this. Thank You.



PICS:

Day of arrival


New Wheels & Tires


Front Suspension & Brakes:





Motor, Rear end, & drivetrain work:






















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Old 01-02-2017, 09:16 AM   #2
spec-al
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Quote:
1) Can I transfer my 'e' single mass flywheel and new clutch kit over to the 'i' transmission? Im not sure if Ill get the 'e' motor with or without the transmission, so Id like to be proactive and just plan ahead for both scenarios using either transmission.
Yes, but don't do it. It's a boat anchor. Something like 10 lbs over the stock 325i flywheel weight.
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Old 01-02-2017, 09:22 AM   #3
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Swapping from a 86e to a 87i is less work than to a 88i+. I've done both, the 88i has different routing for the cooling system, and uses a different water pump. I ended up having to rewire the fuel injectors to work with my 87i harness as well.

You will want to swap the rear end too. The 325i motor with the 325e rear end (2.93) is a dog. First time I drove the car post swap I questioned how much faster it even was haha.

Last edited by spec-al; 01-02-2017 at 12:09 PM.
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Old 01-02-2017, 09:38 AM   #4
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Yes, but don't do it. It's a boat anchor. Something like 10 lbs over the stock 325i flywheel weight.
That's a good point. I'm assuming the clutch itself is the same? I would like to reuse my new clutch if possible.
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Old 01-02-2017, 09:45 AM   #5
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Swapping from a 86e to a 87i is less work than to a 88i+. I've done both, the 88i has different routing for the cooling system, and uses a different water pump. I ended up having to rewire the fuel injectors to work with my 87i harness as well.

You will want to swap the rear end as well. The 325i motor with the 325e rear end (2.93) is a dog. First time I drove the car post swap I questioned how much faster it even was haha.
I know the 87 harness is pretty much plug and play, but I didn't realize there was an issue with injector wiring on later model harnesses. Also, as far as the cooling goes, couldn't I just use my 'e' water pump as long as I retain my 'e' radiator and hoses? I thought the only difference in the water pump was the hose connection. Would the 'e' water pump mount up to the 'i' motor? I just don't see any benefit or reason to changing the entire cooling system over to an 'i'.

I actually plan on swapping the diff and gauge cluster after I get the motor swap complete.
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Old 01-02-2017, 10:06 AM   #6
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The clutch itself will be the same but there are combos of flywheel & trans that require a 323 TOB so do some reasearch. I went with an RHD 7 lb flywheel when I did my swap which I highly recommend if you don't already have a flywheel.

Early cooling systems are all the same so you're good there. As for the drivability issue on the e, I'd def have a smoke test done before I started swapping engines.

Other than that you've got some pretty parts there and a nice foundation.
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Old 01-02-2017, 10:21 AM   #7
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Originally Posted by jeffnhiscars View Post
The clutch itself will be the same but there are combos of flywheel & trans that require a 323 TOB so do some reasearch. I went with an RHD 7 lb flywheel when I did my swap which I highly recommend if you don't already have a flywheel.


Early cooling systems are all the same so you're good there. As for the drivability issue on the e, I'd def have a smoke test done before I started swapping engines.

Other than that you've got some pretty parts there and a nice foundation.

I could be mistaken, but I believe the use of the 323 TOB comes in play when re-using the 'e' transmission, but I could be wrong. It sounds to me like I shouldn't have any issues with using the 'i' transmission/flywheel and putting in my 'e' clutch kit.

Im waiting on the smoke test now, but Im not convinced that its a vacuum leak. I dont like downtime, so I just want to be proactive here and get my ducks in a row.
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Old 01-02-2017, 10:26 AM   #8
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Originally Posted by CMatos View Post
I could be mistaken, but I believe the use of the 323 TOB comes in play when re-using the 'e' transmission, but I could be wrong. It sounds to me like I shouldn't have any issues with using the 'i' transmission/flywheel and putting in my 'e' clutch kit.

Im waiting on the smoke test now, but Im not convinced that its a vacuum leak. I dont like downtime, so I just want to be proactive here and get my ducks in a row.
I'm pretty sure all the transmission/clutch stuff is more or less interchangeable between the e and i. The 'e' cooling stuff *should* work as Jeff has mentioned, but when I did the swap I got a new water pump, hoses etc. Later cars I think build date 88+ got the revised cooling system (diff rad, water pump, routing, overflow tank).
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Old 01-02-2017, 10:35 AM   #9
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Re: the flywheel, I just took a look at your pics and the flywheel looks like an "i" flywheel to my eyes.

The eta flywheel looks like something out of an old timey car... But do a little research.
http://www.r3vlimited.com/board/showthread.php?t=43809
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Old 01-02-2017, 10:40 AM   #10
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Re: the flywheel, I just took a look at your pics and the flywheel looks like an "i" flywheel to my eyes.

The eta flywheel looks like something out of an old timey car... But do a little research.
http://www.r3vlimited.com/board/showthread.php?t=43809
I know that there are two types of flywheel for the 'e'. The single and dual, but Im not sure about interchanging from 'e' to 'i'. I think my safest bet is to use the stock 'i' flywheel with my clutch kit.
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Old 01-02-2017, 10:46 AM   #11
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This is my "i" flywheel for reference.
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Old 01-02-2017, 10:53 AM   #12
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This is my "i" flywheel for reference.
Hmm.. Definitely looks very similar. I know my flywheel is an 'e' because it does have the metal hump for the CPS. Other than that, they look identical. Once I pull the transmission, I can get them side by side to compare.
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Old 01-02-2017, 12:07 PM   #13
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Hmm.. Definitely looks very similar. I know my flywheel is an 'e' because it does have the metal hump for the CPS. Other than that, they look identical. Once I pull the transmission, I can get them side by side to compare.
Interesting! I assumed all the etas had the boat anchor single mass, but maybe the dual mass isn't that far off from the "i" flywheel...
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Old 01-02-2017, 12:12 PM   #14
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Based on your parts list, looks like a great starting place for a DE car! The 'i' motor is way better for that. I think we popped 3 b27s doing endurance racing and had waaaaay better luck with b25 with a stock rebuild.
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Old 01-02-2017, 12:18 PM   #15
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Based on your parts list, looks like a great starting place for a DE car! The 'i' motor is way better for that. I think we popped 3 b27s doing endurance racing and had waaaaay better luck with b25 with a stock rebuild.
I agree. I just wish I would've made this decision from the start because it would've saved me a heck of a lot of time and some money. Live and learn I guess. I know the stock 2.7 probably would've gotten old pretty quick since it isn't exactly ideal for track use. I know the 2.5 is the better choice for me.
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