M30B35 Swap FAQ

[Mark Goddard]

Thanks Canuck YYC,

I think its an M30B34 now ive researched the ECU. I guess it was changed to a more 'modern' and more widely available unit, from the 2.8 it used to be.
I think the cheapest option to squeeze a little more out of the M30B34 may be to fit a Mark D'Sylva EAT chip, ive e-mailed him so hoping to get some figures from him. Car already has E28 mechanicals/suspension etc, and lowered/bisteins/7 series sport LSD, getrag 265 etc. Would like to break the 200 bhp barrier with at least 230 lb/ft of torque. Need to ditch the electric seats and elecrtic windows, dont like weight.

[Bimmerguy2002]

You need to do the m30b35 swap to get those numbers, especially go to motronic 1.3.

[Zaffer]

If I remember correctly, doesn't the m30b35 make 208 hp? What does that number jump to if it's chipped? I am seriously considering doing the swap in a year or so and would like to know more about what kind of numbers I can see.

Also, anyone have any more info. on the question I asked concerning the pins and connectors and how it's done?

[MrNic3Guy]

I was reading this thread and thinking of doing this swap in the furture. I was checking out Wikipedia, and it said something about known problems with M30 motors. Is this really true?

http://en.wikipedia.org/wiki/BMW_M30

[edit] Known Problems [1]
These problems may not necessarily apply to all versions of the M30 engine.

-An "oil spray bar" is mounted above the camshaft. This hollow metal tube has perforations on its underside that spray oil over the camshaft and rocker arms, but with time the two banjo bolts that hold the bar in place can loosen. As a result, oil passage through the spray bar will get restricted, and some of the camshaft and rocker arms may not get cooled and/or lubricated properly, leading to fatal wear.

-On some models, the return valve in the oil filter housing fails with time, thus making oil run out after stopping the engine, instead of keeping it in the housing. While not a critical problem, it results in the engine needing up to five seconds to build up proper oil pressure upon engine start. BMW replaced the oil filter housing with a more durable valve around 1991.

-While not a problem by design, the spacing between the valve rocker arms and the valves must be adjusted approximately every 30,000 km (20,000 miles). Failure to adjust might lead to poor running, increased fuel consumption, and engine wear.

-The engine fan is mounted with a viscous coupling that expands when heated. As the engine becomes warm, the coupling gets a better grip on the fan, thus leading to increased rotation of the fan, and more airflow. If this viscous coupling fails, the fan will only rotate relatively slowly (as driven by the engine by a V-belt), and will not provide sufficient cooling, leading to overheating. Overheating can extremely quickly lead to engine failure, such as a destroyed headgasket or a warped or partly melted cylinder head.

Makes me really think about it now.

[MrNic3Guy]

If I remember correctly, doesn't the m30b35 make 208 hp?

http://en.wikipedia.org/wiki/BMW_M30

[Bimmerguy2002]

I was reading this thread and thinking of doing this swap in the furture. I was checking out Wikipedia, and it said something about known problems with M30 motors. Is this really true?

http://en.wikipedia.org/wiki/BMW_M30

[edit] Known Problems [1]
These problems may not necessarily apply to all versions of the M30 engine.

-An "oil spray bar" is mounted above the camshaft. This hollow metal tube has perforations on its underside that spray oil over the camshaft and rocker arms, but with time the two banjo bolts that hold the bar in place can loosen. As a result, oil passage through the spray bar will get restricted, and some of the camshaft and rocker arms may not get cooled and/or lubricated properly, leading to fatal wear.

-On some models, the return valve in the oil filter housing fails with time, thus making oil run out after stopping the engine, instead of keeping it in the housing. While not a critical problem, it results in the engine needing up to five seconds to build up proper oil pressure upon engine start. BMW replaced the oil filter housing with a more durable valve around 1991.

-While not a problem by design, the spacing between the valve rocker arms and the valves must be adjusted approximately every 30,000 km (20,000 miles). Failure to adjust might lead to poor running, increased fuel consumption, and engine wear.

-The engine fan is mounted with a viscous coupling that expands when heated. As the engine becomes warm, the coupling gets a better grip on the fan, thus leading to increased rotation of the fan, and more airflow. If this viscous coupling fails, the fan will only rotate relatively slowly (as driven by the engine by a V-belt), and will not provide sufficient cooling, leading to overheating. Overheating can extremely quickly lead to engine failure, such as a destroyed headgasket or a warped or partly melted cylinder head.

Makes me really think about it now.

The 1st one is just taking the valve cover off and putting loctite on the bolts
The 3rd one is just a valve adjustment
The 4th one a fan, is normal wear item.

[MrNic3Guy]

These are some things that would need to be done, before dropping in the motor. Kind of important.

[Bimmerguy2002]

Same with the m20, its no different. Some n00b who has never opened an engine probably wrote that, its not bad stuff, its ignorance.

[MrNic3Guy]

[fastpat]

Well, I was all set to yank the e24 B35 wiring harness I'd acquired and buy a Super eta harness, but this FAQ has convinced me of the goodness of staying with the B35 harness after all. It fits the engine, I'll do the connector swap.

Great write up, superlative illustrations, the pin out description .jpg and the pin out diagrams, are what's been needed for a long time.

Thank you for going to the trouble in accomplishing these things.

Here's my photo's of the B35 engine, anyone is welcome to use them to illustrate this swap.

[BDK]

Friggin Great write up!!!
Does auto vs 5 spd play into this at all?
Sorry, i suck at anything eletrical ....
I ask cuz I just picked up a late 88 e24 B35 out of an Auto car and I am going to slap this into my 89 e30 5 spd cab...
I am researching the swap now on the e30 forums but thought I would ask here while everyone was talking about it...
Thanks

[Brad D.]

No, the transmission doesn't matter. It has its own ECU and is totally independent from the engine's ECU. I am not 100% sure on this, but I think you are going to want to get a e34 b35 wiring harness for your e30 swap since it already has the correct C101 fuse box connector whereas the e24 b35 harness has a square fuse box plug like the e28.

[BDK]

Ok, B35 gurus,
I picked up my early B35 mit 115K today and it has the early 150 ECU, this is 1.1 Motronics same as the later M20's (like mine) have so this should be plug and play now pretty much correct.
I have kinda researched (R3V archives) that I should be able to just use my M20 harness mit extending some wires...
Is the 179 ECU mit 1.3 that much better?
Is my hp/tq the same as the typical B35? 208/225?
all I can find is the B35 info listing as such and this motor looks to be B35 all but the ECU...
Anyway, I like what I got for the price I paid so now we head forward....
Thanks for any and all wisdom...

[Bimmerguy2002]

if you have an 88+ and on wiring harness that has the quick release under the intake manifold. Cut that connector off and use a normal set of injector wiring from a 87 325i or super eta e28 harness, they have the quick clips that dont require a pick. Like a couple feet of wiring Anyway....

If you have an 87 325i, then you just need to extend. Both require extending regardless.

[lito]

will the oilpan of a m90 engine fit a m30b35 block?

[lito]

m30b35 is it wasted spark or full sequential?

[SamSpade]

Lito, we met at the track 2 weeks ago. The guy has some serious turbo power in his 30 yr old e24, 430rwhp at 1.2 bar iirc.

The m30b35 uses Motronic 1.3, which means it's still a single coil rotor-distributed spark, albeit timed by the ECU. Injectors are batch-fired 1/3/5 and 2/4/6.

Let's get together sometime before or after I finish the m30b35 transplant on my e23.

[lito]

ok..tnx mr sam...hope to hear from you soon

[jaydick]

Okay as I prepare to carry out a M30B35 swap on my 1986 BMW 635csi, I have some questions regarding the wiring harnesses. My M30B35 motor came from a 1989 635csi. I obtained the wiring harness with the unit and there is a plug 12-pin plug that resides near the DME that I am not sure what it connects to or what has to be connected to to it (see picture with large black plug figure 1.). On my 86 manual 635csi near the DME on wire harness is a green and white 4-pin plug that interfaces (see figure 2). Can someone that has done the engine swap tell me what needs to be hooked up from the green & white plug to make this swap work?

Need help.

Thanks

Jay

Figure 1.

Figure 2.

[Brad D.]

Since I'm not entirely sure what the first plug is it would really help to see where the plug is in reference to the rest of the harness. In the second pic you only need to be interested in the white connector, which is C103. With the e24 harness it should just plug into your e28's C103 connector.

[Kyle in NO]

Figure 1 should be the connector that plugs into your fuse box.

[jaydick]

Since I'm not entirely sure what the first plug is it would really help to see where the plug is in reference to the rest of the harness. In the second pic you only need to be interested in the white connector, which is C103. With the e24 harness it should just plug into your e28's C103 connector.

Brad I will take a few more shots of the 89 E24 wiring harnness to better exhibit where this plug comes from and post back here in the forum for additional analysis.

Thanks

Jay

[Brad D.]

Figure 1 should be the connector that plugs into your fuse box.

That's what I thought too at first but the fusebox plug (C101) is a 17 pin plug, not a 12 pin plug like that one.

[Jean]

No, the transmission doesn't matter. It has its own ECU and is totally independent from the engine's ECU. I am not 100% sure on this, but I think you are going to want to get a e34 b35 wiring harness for your e30 swap since it already has the correct C101 fuse box connector whereas the e24 b35 harness has a square fuse box plug like the e28.

Wrong info. E34 b35 harness has a 25 pin X20 connector, not the same connector as on the e30 with 20 pins.

[Brad D.]

I used an e34 harness and I could have sworn its C101 connector has 20 pins.