M20B27 on LPG - Developments

[StuBeeDoo]

Well, if the W.A.R chip has no other benefit for me (which I doubt) at least I've overcome my persistant fast idle on LPG issue by dropping the idle timing on the map I'm using for LPG running.

[e301988325i]

Well, if the W.A.R chip has no other benefit for me (which I doubt) at least I've overcome my persistant fast idle on LPG issue by dropping the idle timing on the map I'm using for LPG running.

Well that's good news, have to report mine is fine, although a little low before the VAP is fully warmed

[StuBeeDoo]

If all the stuff arrives PDQ and I get my finger out, I might even have the MAF mod done in time for the dyno session.

[e301988325i]

another thought, you could use an adaptor to mount a cone filter to the front of the AFM, but instead use it to connect a round hose to the stock airbox. I have IIRC one if you require.

Stu, I do have one, but it's fairly primitive, M20/M30 AFM suitable with lots of holes, ancient and corroded (aluminium), 75mm plain OD. It's yours if you want it, but TBH I'd buy a new cone filter for £15 with a new adaptor, one or the other one I linked too. Pm me your address if you want it, FOC.

[StuBeeDoo]

Thanks Alex, but I'll try it without first.

[StuBeeDoo]

Time to start with the MAF conversion - the main bits are on the dining room table. OK, so it may turn-out to be a total waste of time and money, but my theory is that the Miller MAF at nearly £300 may flow better then the standard AFM, but it's still only 51x51mm at its inlet. And because I've not used the stuff off my car, if I fail with the mod I haven't disabled the car for any longer than it takes to swap it all back.

Sorry the pic's aren't the best...........



The MAF is from the M50B20 engine. I chose it because it's 70mm outlet, the same as the M20 AFM. I've taken a few measurements and made a few calculations.
The inlet into the AFM is 51mm square. CSA here is 2601sq.mm.
As best as I can measure it, the AFM outlet is 49x42mm. CSA = 2058sq.mm.
Now, I don't know if an AFM needs venturi effect to work correctly, and TBH I can't be arsed to find out. But it seems to me that there will be some venturi effect within the AFM, intentional or not.
The internal diameter of the MAF is 63mm. CSA = 3117sq.mm. Obviously this doesn't include the reduction in CSA brought about by the mesh, but I can't think it will be reduced to anywhere near the inlet or outlet CSA of the AFM. I don't think it will actually be very much different to the CSA of the 60mm standard 325i TB with the spindle taken into account.




The MAF is approx. 50mm shorter than the AFM, This will mean that when the mixer is fitted the whole assembly will be roughly the same length as the AFM and I won't need the bodged intake boot anymore.






The "land" on the air filter casing could be a problem, but I think I've come-up with a solution.

More to follow as it gets done.

[e301988325i]

Here's one I made earlier, I'm really interested to see how you get on, not being able to see a 'nice' solution for getting a seal on the standard airbox forced me to go cone filter.

The dimensions for the AFM's are based on the smallest point, I was looking at restrictions.

For others reading this, it is quite possible to extend the rectangular hole in the standard airbox to suit the M30 AFM (courtesy of Hongkongfuey for that one, I have his air box in my possesion).

for info the M20 AFM is 38 x 48mm = 1824sq/mm
for info the M30 AFM is 38 x 72mm = 2735sq/mm
M20 60mm TB = 2350sq/mm - spindle shaft is actually 8mm dia.
M20 64mm TB = 2700sq/mm - 15% bigger in area

I hadn't worked that out before, makes interesting reading.

edit - improved accuracy based on actual 8mm TB spindle shaft, and notice how the big bore M20 TB is so close to the M30 AFM.

[Ant]

venturi tube not required for the MAF Stuart, only AFM REQUIRES that hence cones loose TQ on these.

early chromie airbox from an M10 with efi would be a good choice, fits in the bay and its steel so easily modded to suit the task @ hand.....

Me, I'd go ITG JC60-67 everytime

[StuBeeDoo]

Right, I've done a bit more of the MAF mod today.

This is the AFM with the lid removed. Apologies, once again, for the shite photography.




..... And the same but with the loom socket and the PCB etc removed.



You can see the IATS in the top right-hand corner, still in situ. It's held in place on 2 posts which are cast as part of the AFM body. These are longer than the flange of the IATS and are burred over to hold the IATS in place. There is silicon sealer between the AFM body and the IATS flange. I ground the burring off with a Dremmel-type jobbie, being careful not to damage the IATS flange too much, then levered the IATS out of the AFM body.

Here's the IATS removed from the AFM.




Moving on to more interesting stuff - check this out!



70mm hole cutter I bought to fit the LPG filler in the car. Thought I'd never use it again. It came in handy for this.....
A sheet of 2mm perspex I happened to have kicking about, left over from some household DIY.




I cut the hole in it, then cut it roughly to the shape I need to adapt the MAF into the air filter casing.
Another not very good pic. but this is the new adaptor sat on the MAF.




If you've ever had an AFM off the air filter, you'll have noticed the 2 pins moulded into the air filter case, between the stud holes either side. These came in handy. I drilled the adaptor, using the old AFM gasket as a template.



The adaptor was then held in place while I used it as a template to guide the hole cutter going through the air filter casing.



Here's the MAF loosely fitted in the air filter.




I've got the correct o-ring for sealing the MAF to the air filter on order with BMW. I don't really want to do much more until it arrives. I'll possibly have another update on Thursday.

[Gunni]

classic

[StuBeeDoo]

classic

In what respect Dude?

Classic bodgery?
Classic waste of time?
Classic balls-up?
Classic ingenuity?

BTW if anyone's interested, I think the bigger MAF could be fitted this way as well.

[e301988325i]

That's looking good Stu.

Based on experience, I'm assuming the hole saw probably cut a little over, perhaps an old section of inner tube (wheelbarrow) stretched around the 70mm od of the MAF, could possibly give a rubber seal all along the 15mm 70dia length and allow a bit of movement between the MAF and airbox.

Or perhaps cut something like this up around the 70mm od

http://cgi.ebay.co.uk/HEADPHONE-HEAD-PH ... 3363219313

Just trying to think of ways of guaranteeing the seal

[daimlerman]

classic

Wish I was allowed to do that kind of work indoors,I get banished to the cold garage!

Looks good,Stu,hope it works.

[StuBeeDoo]

^^^ Plenty more to come Alex, including sealing.

[StuBeeDoo]

Wish I was allowed to do that kind of work indoors,I get banished to the cold garage!

No power in my garage, so she's got 2 choices;-
1) The back door gets left open so that I can run an extension cable from the nearest socket (in the kitchen)
2) I work in the dining room.

[StuBeeDoo]

No photo's yet, but the adaptor's now bonded/sealed to the air filter case.

A couple of things I need to think about, and any suggestions from you chaps will be taken on board:-
1) Where should I fit the IATS? Does it have to be in the inlet tract (ie in the the MAF somewhere), or will the air filter casing be OK?
2) How am I going to support the outlet end of the MAF? The post thingy that supports the AFM won't be any use as it doesn't line-up. I think it will definitely need supporting because the mixer will bolt straight to it and it's pretty heavy.

I've worked-out how I'm going to secure the MAF inlet into the air filter casing. There will be a pic. or two when it's done.

[e301988325i]

A suitable size version of this might be nice, I can't find one though.

http://cgi.ebay.co.uk/5-x-SPRING-TOOL-C ... 33514d9e8f

or

http://cgi.ebay.co.uk/U-Bolt-Universal- ... 33616747d5

I think common sense would be to mount the AITS in as similar position to standard as possible, ie directly in the airflow. Although I see no logical reason not to mount it in the airbox.

[StuBeeDoo]

That's a thought, Alex - thanks for that.

Since I submitted that last post, I've realised that once I've got it all mounted-up, I might be able to find some way to utilise the existing support post with some kind of clamp around the mixer body.

[StuBeeDoo]

Based on experience, I'm assuming the hole saw probably cut a little over

I thought it would have as well Alex, but it didn't. I had to open it out slightly with my Dremmel-type tool. The MAF is actually a nice snug fit in the bore.



I've now got my head 'round the IATS siting issue. I'm going to make a bracket to hang it inside the air filter, right in front of the MAF inlet.

[Ant]

drill a hole and bond the IAT into the MAF tube dude

it will work best in this location as air will be flowing over it constantly

[daimlerman]

The MAF is actually a nice snug fit in the bore.
[/b]

As the bishop said to the actress......

[StuBeeDoo]

drill a hole and bond the IAT into the MAF tube dude

it will work best in this location as air will be flowing over it constantly

Cheers for that Ant. I appreciate that any advice you give here is potentially doing yourself out of business.

Having said that, can you tell me what the situation is with the voltage that the MAF sends to the ECU? I've read that the MAF puts out 0-12v where the AFM is only 0-5v. Is this correct and is it going to present me a problem? If so, what's the work-around?

TIA.

[Ant]

std AFM uses a 6V signal from the ECU, your MAF should take a 12V input and convert that to a 0-5V output for the ECU to use as load input.

HTH

[StuBeeDoo]

^^^ Thanks for that Ant - no more questions from me now. I appreciate your input.

This is where I'm at now. I collected the o-rings today.



I'm hoping I can utilise the support post with a clamp around the mixer.
The jobs left to do are;-
Work-out some way of holding the MAF securely against the filter
Fit the IATS
Sort the wiring
Tidy the adaptor plate edges

[CHR1S1990]

very nicely done stu - but a question, why didnt you use the airbox the MAF was attached to originally? they clip straight on don't they?

[StuBeeDoo]

very nicely done stu - but a question, why didnt you use the airbox the MAF was attached to originally? they clip straight on don't they?

They're not the same. I had a look under a couple of bonnets (E34 and E36) and I couldn't see any way of making the whole airbox fit in the E30. The problem is that the E30 engine bay is cramped on the induction side.

[CHR1S1990]

fair enough! i was just looking at some pics on another thread thats all though they are M5x engines, and looks like it would be a PITA with the extra length of the BLOS

[e301988325i]

MAF's looking good Stu.

[StuBeeDoo]

Another small update:-

I tried to get the IATS as near to the correct orientation as I could, although it's at the opposite end.



I think I've worked-out how I'm going to secure the MAF to the casing. I need to find a couple of body washers.
Tomorrow evening I'm hoping to get the soldering done.

[StuBeeDoo]

After spending over 3 hours trying to get the bloody soldering done - and nearly throwing-in the towel in sight of the finishing post due to my inability.........
I've had it running.
The petrol fuelling is all to hell, as expected. But it starts and runs on LPG, although the Leo parameters need adjusting.

Here's today's batch of photo's.

Firstly, my solution to holding the MAF into the air filter casing. The nuts with captive washers that held the AFM in the casing came in very handy. I drilled-out 2 of the AFM stud holes, put 25mm long 6mm bolts through from the inside, held them with normal nuts, put the MAF in position and used the nuts from The AFM to catch the flange around the periphery of the MAF.
Bodge?
Perhaps, but it works and it isn't life-threatening. The first pic is also a good shot of the IATS in place.






The next one is the original socket from the AFM soldered to the wires from the MAF plug and the IATS. Isn't heatshrink cool?? The red cable left hanging is for the 12v ignition live feed. I spliced it into the fuel pump relay feed, but I may move it somewhere else because in the summer I pull the fuel pump fuse as I never need to run on petrol.



After I bound the cables and terminals with loom tape, I introduced the MAF assembly to the car. I almost had another "throw in the towel" moment when I found this..........



I managed to get the mixer and MAF to mate-up, but I had to disconnect the ICV from its mount so that I could twist the intake boot to the necessary position.
Then I had to instigate bodge number 2 to get a seal between the mixer and MAF. I'm too embarrassed to take a photo of that one, but it involves 3 cable ties.

So that's it - almost job done. I just need to get the mapping done now. I've finally got a 3D ignition map on LPG at last.
I could have got 'round it simply by having a new mixer of the AFM type, but IMHO they're not big enough in the venturi department.

I'll post the dyno results 2 weeks today.

[e301988325i]

Sounds like you've had a frustrating day! Glad it's all up and running, is it driveable? I'd be interested to hear what you've had to adjust on the Leo and vap to get it running nicely with the new MAF.

Looking at the angle between your MAF/Mixer and inlet elbow I think you may end up with a better end result putting the cone filter adaptor on the stock airbox and a bit of silicone hose between that and the MAF to give a bit of flex better alignment.

Looking closely this one comes with the same adaptor I offered up, and has a 70mm+ through bore.

http://cgi.ebay.co.uk/84-98-BMW-E30-E36 ... 483bc8482a

[StuBeeDoo]

It is drivable Alex, but it's idling way too fast - 1500rpm+

It was getting dark by the time I finished, so I'll have a another go in the morning.

I like your idea for mounting the MAF. If I'm honest, I should have taken more notice when you first suggested it. I'll do something along those lines when the weather gets warmer and there's more daylight hours.

[StuBeeDoo]

Actually Alex, I should have enough stuff here to do what you suggested but in a slightly different way.

I think the plan is going to be;
Leave it as it is for now and get the mapping done.
Then, when I'm happy with it mod the old air filter casing.

At least that way, if for some reason it can't me made to run on the MAF I can still go back to the AFM easily.

[e301988325i]

I think it'd be a good idea to carry the stock AFM and air box in the boot for a while!

I really can't understand why your idle is so high? The ECU ignores the AFM signal at high loads and when it receives the idle signal from the TPS, does your econometer swing to infinite mpg on the overun above 1500rpm?

My two worst inlet bodges were when the garage I was using said the inlet elbow which was split would be £100 from BMW, so I taped the ridges with duck tape to seal them! On another occasion I used nothing but duck tape to connect the M30 AFM to the rubber boot when I couldn't get it stretched over the AFM and had no access to the required hot water! I drove 100 miles like this with no problems!!!

[StuBeeDoo]

I really can't understand why your idle is so high?

I think it's because there's now extra "draw" through the venturi, Alex. That's all I can put it down to. I've had to knock the Leo default down 7 steps to get the idle a whisker below 1k.

does your econometer swing to infinite mpg on the overun above 1500rpm?

Yep!


While I've been test piloting, I've taken note of my vap. temp. reading:-
On the road, it runs at 50deg +/- 2deg. IIRC that's about what the vap should run at.
Within a few seconds of pulling-up (say at traffic lights) it goes up to 60ish and if stood idling for any length of time it maxes-out at 74.
Once it gets above about 65deg, the idle speed increases.