Some questions about the M20B25.

[TDP 0]

So some months ago I decided it would be fun and a bit of a lark to put the M20B25 out of a 1989 E30 into my 1980 E21. Oh how I laughed... and oh how short lived that laughter was.

Anyway, given my vast mechanical knowledge (gleaned entirely from dimly remembered episodes of Knight Rider and from ignoring good advice) I did not envisage too many problems. Yes. Turns out there were one or two after all.

First. Turns out the M20B25 is a fuel injected engine. I know! Who knew?

As a result I've had to learn a whole new vocabulary. Exciting phrases like airflow meter, oxygen sensor and fuel return now pop up in my everyday conversation. Here's an example:

'Sweet jebus! It needs a what? Airflow sensor? Where the hell does that go? It sounds expensive. And it's different from an oxygen sensor?.. which I also don't have. Right. Choice.'

Which is why I need the help of clever and good looking people like you lot.

Here is a photo of my engine:

Here are some questions:

1. Should there be an airflow meter where the green circle (and fetching pink rag) is?

2. Do I connect the pressure/feed fuel line to the thing inside the red circle?

3. Is the blurry thing with the purplish circle around it what I connect the vacuum hose for the brake booster to?

Here is another photo:

And some more questions:

4. The thing with the green question mark pointing to it has a pipe attached to one side of it, but not the other, despite appearing to have fittings for both sides. Should there be something connected to it and if so where does it go? (I've tried looking this up on the internets and so far every other picture I've found as been missing the 'out' pipe on this fitting).

5. Does the fuel return line connect to a nozzle on the end of the injector rail roughly where the red circle is?

6. Where does the oxygen sensor for these engines go?

7. Is there any hope for me at all? (I just want to be loved).

Any help with any of this is gratefully received. I'm a total noob when it comes to fuel injection.

[325jones 0]

So some months ago I decided it would be fun and a bit of a lark to put the M20B25 out of a 1989 E30 into my 1980 E21. Oh how I laughed... and oh how short lived that laughter was.

Anyway, given my vast mechanical knowledge (gleaned entirely from dimly remembered episodes of Knight Rider and from ignoring good advice) I did not envisage too many problems. Yes. Turns out there were one or two after all.

First. Turns out the M20B25 is a fuel injected engine. I know! Who knew?

As a result I've had to learn a whole new vocabulary. Exciting phrases like airflow meter, oxygen sensor and fuel return now pop up in my everyday conversation. Here's an example:

'Sweet jebus! It needs a what? Airflow sensor? Where the hell does that go? It sounds expensive. And it's different from an oxygen sensor?.. which I also don't have. Right. Choice.'

Which is why I need the help of clever and good looking people like you lot.

Here is a photo of my engine:

Here are some questions:

1. Should there be an airflow meter where the green circle (and fetching pink rag) is?

2. Do I connect the pressure/feed fuel line to the thing inside the red circle?

3. Is the blurry thing with the purplish circle around it what I connect the vacuum hose for the brake booster to?

Here is another photo:

And some more questions:

4. The thing with the green question mark pointing to it has a pipe attached to one side of it, but not the other, despite appearing to have fittings for both sides. Should there be something connected to it and if so where does it go? (I've tried looking this up on the internets and so far every other picture I've found as been missing the 'out' pipe on this fitting).

5. Does the fuel return line connect to a nozzle on the end of the injector rail roughly where the red circle is?

6. Where does the oxygen sensor for these engines go?

7. Is there any hope for me at all? (I just want to be loved).

Any help with any of this is gratefully received. I'm a total noob when it comes to fuel injection.

[hotwire 352]

Q1 - Yes - Do you need one? - If so can help

Q2 - NO - this is the pressure regulator which has the return line connected to it

Q3 - Yes

Q4 - Yes, but cant remember what off hand - will clarify for you

Q5 - No - this is the feed in - see Q2

Q6 - In the exhaust front pipe - have you got that?

Q7 - Not sure, but God loves a trier

Does the 2.5 have the engine loom/ECU (computer) etc? You will obviously also need to wire the engine to the car

[*Glenn* 854]

Not being negative here...but I think you have taken on a little bit more of a project here than I think you can handle

You can do it..but it is going to cost $$$

From the questions you are asking it is obvious you havent researched this project. And you have limited mechanical knowledge.

As I've said before...do the research first..then the maths...double it... then decide

I can sell you all the bits you want off a parts car I have at work

Or ring our forum sponsor Ray @ HELLBM

However I do hope it all works out for you

Good luck with the project

Cheers

Glenn

[will 169]

Just to expand on what Hotwire has stated..

Q1. You need an airflow meter, but must make sure you get the correct airflow meter for the motor you are using. Some airflow meters have 4 wires in and others have 5. The airflow meter plug on the engine wiring loom will tell you which one yours uses. Make sure it is an airflow meter off a 2.5 motor.

Q2. you connect a return fuel to the petrol tank to this point.

Q3. Yes, but use a proper vacuum pipe here or it will collapse under vacuum and your brakes will broke....

Q4. This is not used in a motronic motor, in fact this fitting on your manifold is usually seen on an earlier non-motronic motor where that takeoff point goes to an idle stabiliser that prevents the car from stalling if you blip the throttle. Just block it off.

Q5. You connect the fuel line from the fuel pump to this point on the fuel rail.(not to the front as in Q2!!) Also ensure that you use the correct fuel pump, different pumps have different pressures and can cause all sorts of problems if the wrong pump is used. Must be a pump for a 2.5 motronic motor.

Q6. Not all motors use an oxygen sensor, you will need to check what the car the motor came from had installed, if you are unsure take the vin number to BMW and get them to query it, that will tell you whether it was equipped with an oxygen sensor.

If yours had an oxygen sensor, it would go in the manifold downpipe fairly close to where it connects to the cast iron exhaust manifold, I would also get a new one if you need it as these things can be quite problematic and not worth messing around with a second hand one... (imo anyway).

You can also get rid of the oxygen sensor by using a CPU from a car that didn't come with one from the factory.

Q7. I applaud you for jumping into the deep end and giving it a go. This is how I started so many years ago now (hahahaha, I am such an old git now! ), I do not have any formal training in being a mechanic but got stuck in and have successfully done things over the years that would scare even qualified people. Go for it, there are many (non-qualified) people on the forum that have also climbed in and tried (and succeeded). I regularly get phone calls from members here who are in the middle of trying to get something done, have come unstuck and are needing assistance to sort something out. I would think that most of the people racing in the BMW series are in this boat, non-qualified but willing to give it a go..

Good luck in your project, give me a yell if you need any more advice/assistance, but remember I am in the crazy far north so can't just drop in... (send PM)

Will

[Grant 4]

TDP - best and most amusing read i've had in a while.

Whilst I am no help at all, good luck, sounds like you have created a fair bit of work and learning for yourself.

Cheers

Grant

[TDP 0]

Brilliant!

Thanks for the info and advice guys, you folks are the best!

Thanks also for the offers of parts etc, I think I've sourced everything I need now. I do have an ECU and loom and I'm going to leave the electrical side of things entirely to the professionals. The sparkys tell me they can fit an oxygen sensor (the car doesn't have one and there is no bung in the (aftermarket looking) exhaust) which means that once I've fitted the airflow meter and connected the fuel and brake booster lines my part is pretty much done. The point that Will raises about the fuel pump worries me though. What research I did do (finding out how to spell M20B25 and on what day my back-pay would be in my bank account - well spotted Glenn) suggested that I'd be all right with the K-jetronic pump as, because of the nature of that system, it flows good strong pressure. I guess I'll find out.

I'll admit it's been a steep learning curve, particularly on the fuel injection front, and at times quite frustrating (if you want to see a grown man cry ask me why my exhaust has a partial hacksaw cut through it) but it's also been quite fun and, at times, satisfying. I'll let you know how (if) it turns out.

[Gus 5]

rock on dude. listen to Will. I love that guy.

[westy 614]

Cant help, but Im lovin every minuite(sp) of it.

Best of luck.

Youre starting where I did!