m20b20 reassembly...

[Brdjo]

Hello to all

I decided to do some work on my non daily, 1985 e30 m20b20, and get the car ready for next slalom season.

Idea is to convert l jet to motronic 1.3 and thanks to e30 wiki I collected the parts necessary for the job.

Also since the head is sent to shop for rebuild, I was thinking that it will be a good time to replace rings and main bearings and kind a refresh the engine after long sleep at previous owner. To be honest I did not drive car much, but the previous owner said that the car did burn some oil over time and refreshing engine seem logical way to go did some measuring to check cylinder walls and in top position it has 80.04, bottom 80.00 so new rings should do the job..


So the engine is out, and cleaning parts and disassembling started

This will be my first engine rebuild and I am glad that is a m20. I guess i will have a lot of questions but I hope that i will have help from much more experienced people from zone So all my questions will be posted hire.. thank you in advance for any help given.


And the first think I will ask as I did disassembled oil pump for detail cleaning, is there some torq spec for 5x M6 8.8 bolts that bolts two housing of the pump?

[blimmer86]

http://www.e30zone.net/e30zonewiki/inde ... e_Settings

[magpie]

have you thought about m20 b25 conversion ?

[Brdjo]

http://www.e30zone.net/e30zonewiki/inde ... e_Settings

that was my first stop but I did not found info there or I misunderstand it, i guess that's it but I am not sure? this "to engine bolts" confusing me..


Oil Pump Cover Plate to Engine Bolts (M20 & M40 Engines) (M6 Bolts) - 10Nm

[Brdjo]

have you thought about m20 b25 conversion ?

Yes I did, but for now it;s has to be m20b20 because car must be registered and legal, and I already have lot of parts for m20b20.

basically what is missing from rebuild and conversion to motronic 1.3 is AFM, new crankshaft bearings, and gaskets.. so for first time engine rebuild, terms of cost and learning experiences it will stay as it is

b25 will be the real thing but it will have to wait some better times

[Brdjo]

So, just to be on safe side, bolts market red on picture are tighten to 10 Nm?

https://imgur.com/ABDFgCh

[Brdjo]

Need to replace one of coolant caps on block. How to remove old one? I was thinking drilling the cap and then somehow wiggle it out with screwdriver..?

[Brianmoooore]

Use a screwdriver or punch + hammer on the lip of the cap, taking care not to damage the block. Cap will 'roll' out.

[Brdjo]

Use a screwdriver or punch + hammer on the lip of the cap, taking care not to damage the block. Cap will 'roll' out.

Thanks for helping

Ok, and for installing a new one I assume something flat and hammer to push it in?

[Brdjo]

I have another one for you

The engine that I want to transform from l jet to motronic is m20b20 from 1985. The pistons on this engine have profile that goes deeper in the head and I assume that is why the compression ratio is 9.8:1 against 8.8:1 on later m20b20 engine with almost flat piston top.. The 731 head will be used..

My question is will the 1.3 motronic system work ok with 9.8:1 ratio.. Can ecu chip stay stock?

[Brianmoooore]

It'll work fine, but a little bit of mapping would improve things further. I think Speedtouch could help with an 'off the shelf' remap for a high comp. 2.5, but I don't know about a 2.0.

P.S. Thinking about it some more, a higher compression ratio requires the spark timing to be retarded slightly, whereas for maximum power, you normally need to advance the timing to just short of where 'pinking' occurs. The generic timing maps will have a safety margin built in (retarded), so as long as 'pinking' doesn't occur with the higher CR (very unlikely for such a modest increase), the standard map will work 'better' on your engine than the engine it was designed for.

[Brdjo]

Once again i am stunned by your knowledge.. Thank you very much Soon the assembly of bottom end will start..

[Speedtouch]

Indeed, it should run OK with the standard chip, however, if you later require a Mild/Wild EPROM upgrade chip, I can supply either for the M20B20.

[Brdjo]

Indeed, it should run OK with the standard chip, however, if you later require a Mild/Wild EPROM upgrade chip, I can supply either for the M20B20.

Thanks for help, of course that you will be the first one to call when time for chip comes

Now I just want to assemble engine and make it run

Today I got my crank shaft from the shop, as they said the main bearings on crankshaft has to be grind to fit the +0.25 bearing size and the connecting rod bearings are fine (in standard dimension) and they are only polished and fit new standard dimension bearings..
I did find this a little bit weird, how is possible that the main bearings on crankshaft need machining and connecting rod bearing do not, but then again I am not an expert on the subject

And one more thing, the worker from the shop assured me that I do not need to replace connecting rod bolts, and just to reuse old bolts.. I am not sure about this, I did read that main crankshaft bolts can be reused but connecting rod bolts need to be replaced with new bolts?

[Brdjo]

Yesterday I was playing with engine bay loom, adapting c191 connector from some kind of swapped homemade connector (really bad one).. Other then that it;s a stock 1.3 motronic loom. Now I need to sort thinks with oil level sensor, I did read on e30wiki that old sender can be used with some loom change, and I was wondering is it possible to cut old plug from sensor and solder 3 pin connector to mach engine loom. Obviously it will be one wire short, old sensor have two wires.. Is there a way around this and keeping engine loom connector untouched?

[Brianmoooore]

Easiest and best solution would be to change the level sensor to get the benefits of the dynamic level sensor as well as the static one, but what you say should be possible.
Brown wire on both type of sensors is earth, although the double sensor is also earthed through it body to the sump. Don't know if this also applies to the old type single sensor. This was not a too clever idea from the original designers, because if the main engine to body earth strap fails, all the starter motor current will attempt to flow through the sensors earth wire, with spectacular results.
The green/yellow on the later engine loom is for the static level sensor, and should be connected to the old style sensor. The blue/white wire was for the dynamic sensor, and should be left open circuit, although it is connected to earth by a 1000 ohm resistor inside the original sensor. Maybe some experimentation is needed to see if this is necessary.

[Brdjo]

hmm, now that I think about it, maybe I can install new wires to old sensor and insert a bulb on dashboard somewhere, separate from the rest of the stock harness.. do you know what voltage is sent to sensor? 5V?

[Brdjo]

after quick test of sensor, i realise that some kind of transistor must be used to monitor sensor, but will look more in to it..

[Brianmoooore]

Level sensor isn't a simple bulb and switch circuit like the oil pressure switch. Plenty of electronics involved, all contained in the roof mounted check panel.
Circuit is here: http://www.autolib.diakom.ru/CAR/BMW/19 ... /fig06.pdf , but no details of the internal electronics, most of which is contained inside a large IC, IIRC.

[Brdjo]

Thanks, I come to same conclusion... Will leave it for now stock

Yesterday I assembled the bottom end. For assembly oil I used 10w40 which may be a bit thin for first assembly, but that is what I had at the moment. So the head is not ready to go on the top, so the bottom end will be sitting for awhile (20-30 days), and I wonder what can I do to get it ready for first startup. My plan was to fill it with oil and then every 4-5 days to spin oil pump sprocket with electric drill hoping this will lubricate it? And of course couple of spins on flywheel?

[Speedtouch]

If you've used plenty of lube, you should only need to perhaps turn it over by hand once or twice over the period of a month.

[Brdjo]

Thanks

Out of curiosity, is there a force which should turn only bottom end, when is everything is assembled right. This one turn easily by 20nm, it will go lower but my torque wrench to not go below 20nm.

Now I wait for head to come and start final assembly of the engine..

oh I almost forgot, any tricks how to torque the big bolt on the crank xD I believe that this one is need to be turn to 400nm ?
When I was unbolting it I stack big lever under bolts on flywheel and it come out easily, maybe use the same technique

[Brdjo]

I have another question who requires experience

Did someone have use a solid engine and transmission mounts, like aluminium one.. Never use solid one before but I think it will gain some precise shift, due to no engine movement, which is very helpful for this kind of car use.
But in the other hand, I do not know how the engine supporting bracket and front axle support is going to hold up with it. last thing i want is to get something snapped and finish on the side of the track

So, any information will be helpful

[Speedtouch]

I suspect you'd end up with alot of NVH (noise, vibration, harshness) despite the 6-pot being a well-balanced engine...

[Brdjo]

I suspect you'd end up with alot of NVH (noise, vibration, harshness) despite the 6-pot being a well-balanced engine...

Yes for sure, but then again the car is for track use only, no road and traffic whatsoever..

[Speedtouch]

Maybe you could solid-mount the engine/box, but bear in mind you would probably end up frequently breaking propshaft/driveshaft joints, since the rubber mountings help reduce the torque stress on these parts when setting off, or changing gear, seeing as the engine/box has a bit of 'give' and twisting flexibility.

[Brdjo]

Maybe you could solid-mount the engine/box, but bear in mind you would probably end up frequently breaking propshaft/driveshaft joints, since the rubber mountings help reduce the torque stress on these parts when setting off, or changing gear, seeing as the engine/box has a bit of 'give' and twisting flexibility.

Yes that is one of my concerns.. that is why I asked to see what can be expect in reality

Also I work on some custom mount designs with Shore A80 rubber, and I will post drawing here for you to see it and let me know what you think

[Brdjo]

As I promised..

This is the design that i will be working on, black is A80 rubber, top and bottom will be machined from solid piece of steel..
If you have some suggestions, feel free to write it, before machining starts

https://imgur.com/a/lRvtwjc

[verde]

Solid mounting the engine and box is an idea depending what your looking for and what you will tolerate. I have solid mounted the 328 in my e36 drift car and I enjoy the responsiveness and the lack of movement during transition however there is no denying that I have potentially risked my subframe ripping and the whole car vibrates somewhat at idle.

[verde]

Solid mounting the engine and box is an idea depending what your looking for and what you will tolerate. I have solid mounted the 328 in my e36 drift car and I enjoy the responsiveness and the lack of movement during transition however there is no denying that I have potentially risked my subframe ripping and the whole car vibrates somewhat at idle.

I am happy to video this for you. Ultimately I think poly eurathane is probably a best of both worlds but as it’s my drift/hard road car I really don’t care about luxury..

[Brdjo]

Solid mounting the engine and box is an idea depending what your looking for and what you will tolerate. I have solid mounted the 328 in my e36 drift car and I enjoy the responsiveness and the lack of movement during transition however there is no denying that I have potentially risked my subframe ripping and the whole car vibrates somewhat at idle.

I am happy to video this for you. Ultimately I think poly eurathane is probably a best of both worlds but as it’s my drift/hard road car I really don’t care about luxury..

The car is for autocross race use only.. so vibration noise and harshness is not an issue..
The solid ones is the easiest and simplest solution for me to build, but I'm not sure how the engine subframe, engine arms and drivetrain will hold up.. That;s why I was thinking to put some 10mm A80 rubber in between top and bottom solid piece, to give just a bit of move.. and similar thing for transmission mounts.

How your propshaft/driveshaft joints holding? any other issues?

[verde]

If you are concerned about the subframe and arms etc then get the garagistic reinforcement plates. Iv got those on my e30 for the LS swap to prevent the mounts ripping the subframe out. I would weld those in then you have peace of mind.

My prop etc is all fine. I did snap a shaft once but keep in mind I’m running a small case welded diff with AD08s on for ”anormal”a use and then when being drifted it’s having its ass handed to it.

[Brdjo]

If you are concerned about the subframe and arms etc then get the garagistic reinforcement plates.

Subframe will be reinforced either way I forgot to mention..

Thanks for the info

[Brdjo]

Last weekend was the last event for this year.. I drive my daily for fun and to test new 4.25 diff for car that is in build process..

here is the video https://youtu.be/C8QC485ko9c

[Brdjo]

I run in the another problem.. :\
Last weekend I put the head on block and torque down bolts, in next order:

1. Clean the threads on block, WD40 and air. Test fit all bolts by hand.
2. Bought new head bolts (torx head)
3. New head gasket.
4. Torque down in stages, cross pattern order.
- 30 Nm
- 90°
- 90°

And two bolts (between 5 and 6 cylinder) on last 90° turn gave up a bit, around 40° a felt the force dropped a bit and restored around 60°, i keep turning till 90°. When I released the pull on wrench, gauge back up 10°. Then I turn it again to 90° and it stayed there.
To me this is felt like a bolts stretch out a bit if that is possible..

Did someone had a similar situation?