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2.6 litre VW SA Microbus going 20v

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  • 2.6 litre VW SA Microbus going 20v

    Following on from my newbie intro, here's a bit of background before I get stuck into it!

    I have a 1995 VW Microbus, built in SA with a 2.6 litre 10v "ADV" engine. I recently aquired a 7A engine with no loom or ems that had been previously run on lpg only in the back of a mid-80's VW pickup truck (this sort of nonsense isn't that common as they're mostly mpg-obsessed TDi converters who run out of gears. Takes all sorts!) which I will raid for it's head, manifolds, front end and anything else as required to fit to the ADV bottom end. Should be quite nice when done.

    I had the bus put on lpg (a whole other tale) as it's 10:1 and really likes ~100 octane, plus you can't argue with 71p/litre.

    The ems is a unique local-market Bosch of SA Motronic variant (55 pin ecu) which is a MAP sensed, fully mapped system but with batch-fire injectors (Bosch) and a Hall-effect distributor so it's a right old mash-up that was working fine...

    Then it developed a strange fault. Starts on the button on either fuel, idles ok but won't rev more than 1500 and just cuts out and stalls. No misfiring, it's like the ignition has been switched off.

    Does this sound familiar to anyone with extensive Bosch ems knowledge?

    The replacement list includes throttle pot, dizzy, MAP sensor, coil, leads, plugs, ignition switch, in fact everything but the ecu. I thought I'd found a bodged repair in the distributor tail and it behaved itself again but only lasted a few hundred miles then died when I popped out on a short journey a couple of days ago. Came back out after popping in to local fabricator's shop and it stalled as I tried to pull out of a parking bay. Got towed home by the old man...

    I could get a replacement ecu from SA but it will be used/checked and a good £400 which is most of the cost of a Megasquirt V3 system, so that's the route I want to go unless there's something out there that is better for the money?

    The most important thing is that whatever system I fit must have OEM reliability, support full dual maps for petrol and lpg and have an extensive knowledge base in case of any problems in the future.

    What does anyone think before I go and shell out? I'm bound to be asking a lot of daft questions as I get to grips with marrying the two halves of the engine together

  • #2
    Do'nt go there. I tried doing the same with my 2.5 SA bus. There are loads of differences between the 2 motors. Best thing to do is to fit the 20v motor, useing its loom and ecu, they are quite common here in the UK. 170HP standard versus 136HP, 220NM versus 200NM and rev 7000 easy. The 7A is a awesome motor. Nev.


    • #3
      Have to agree with Sa Boy, also you don't need to worry about dual maps and all that carry on, better off using the piggyback ecu from a more modern lpg kit to run dual fuel. (piggy backed off original ecu if you do get a 20v engine and ecu) For starters a standalon ecu does not have settings for taking into account gas pressure depending on temperature and amount left in the tank. It can work but it is not efficiant, and after all that is the whole point of going lpg. Even if you did go stand alone ecu for the petrol end, as long as that map is correct, the piggy back lpg ecu takes care of the rest.


      • #4
        Thanks for the advice fellas, a couple of things there that I hadn't considered about the lpg monitoring...

        I got it fixed and running in the end, had to open up the engine bay loom and found that the ecu main earth wire had cracked down to the last strand! It broke as I separated the wires. It was right next to where the dizzy tail exits the loom, I suppose 15 years of torque reaction and flexing had taken it's toll on the 0,5 wires.

        As for the engine conversion, I'm a precision engineer by trade and we do a fair bit of specialist machining for our local engine shop as well as for our own customers. I also have a tame welder/fabricator to hand for any alloy or tig work so if it means re-working the manifolds, no problem.

        I also learned a lot with a "never-quite-made-it" M90 blown Rover V8 a few years ago Kids were small, no cash, it had to go along with the '72 P6 that it was destined for

        The main reason that I want to get away from the OEM ecu is the fact that it's not serviceable in Europe and pretty old hat now. LPG does need it's own ignition maps so I need a system that will do that too. It's going to be messy I can see.

        Maybe the best route will be putting the 2.6 rotating assembly into the 7A after all?
        I'm collecting it on Saturday so then I can start seeing what's going to give me the headaches.

        P.S . SA BOY, I guess Charlie gave you my message when I thought I'd got wind of your stolen bus?
        Last edited by 95 Microbus; 30th January 2012, 23:32.


        • #5
          I met up with djh at the weekend (thanks again!) after I went to finally collect my engine, which was sat at a mate's workshop in Oswestry. Now it's safely at home

          He managed to sort me out most of the bits that were missing off the motor there and then, along with a few instant improvements like a nice bunch'o'snakes to replace the later cast exh. manifold that's on it, plus a load of other small bits. Good man!

          I'm a little worried as the sump is full of snot, but I bought it off a club mate who had run the engine in a truck, he swears it was healthy before it came out. But he kept the flywheel and rear seal housing for a diesel conversion...and it had then been stored outside under a Wales...where it rains...a lot!

          Anyway, I've decided to keep things simple and source a 7A engine loom and ecu for it, then piggyback that with a dedicated sequential unit for the lpg.

          So for my next newbie question: which ecu would make most sense for a stroked 7A? Am I right in understanding that one of the standard ones is remappable, but not the other?
          Last edited by 95 Microbus; 30th January 2012, 23:30.


          • #6
            Yes Thanks for the info regarding my old bus You must be well relieved now that you have found that illusive fault on your 2.6i. Nice looking engine you got there, its a later one, a lot of thought and work went into that exhaust manifold which is from the earlier 7A. If it's been standing in the damp it's worth droping the sump and having a look at big ends etc. If you are going to use your 2.6 crank, you'll need to remove the cyl head anyway. The internals of your 2.6 and 7A are the same except for the longer stroked 2.6 crank 95.5mm versus 86.4mm, bore is the same 82.5mm. If the 2.6 is the same as my 2.5 then the rods are the same length. Use the 7A ones as they are H beams, nice and strong. The problem I had with my 2.5 was the 7A pistons protruded a lot when fitted to 2.5 crank 92.8mm stroke. The 2.5 pistons have a shorter crown to compensate for this but unfortunately they have large cutterways on the piston tops, so could,nt use them for the conversion. Apparently I could of used 2.0 16V pistons x 5 as that motor shares the same stroke 92.8mm as the 2.5. I've never stripped a 2.6 engine before, so can't say for sure that you'll have the same probs as me. You could I supose weld and skim your piston tops and add small cutterways for the valves? If you need anything I have a lot of new spares for these engines: mains, big ends, head gaskets, rings, seals etc a lot cheaper than you can get locally.


            • #7
              i think it all depends what your goals are and how handy you are. the 10v motor will need machine work to make it work with the 20v head, also it is advisable to add the oil squirters from the 20v into the 10v while it is all in bits.


              • #8
                Nev, you have just saved me a wad of cash on the pistons! I had assumed that I'd be off to JE and have to cough up, completely forgot about the 2.0 16v connection.
                I remember the tales of tuners putting a Passat crank into a MK2 GTi block to get the elusive 1985cc way back when I used to read CCC mag...

                So the rods are all the same length then, I wasn't sure if the 2553's had a longer rod or not, looks like they did it all with a short comp height piston? Can't check the part numbers as the 2.5i doesn't exist according to ETKA, even though the post-1995 wagons are listed! I'll find out once it's all opened up.

                Machining is not a problem whatever, I recently had to clearance a pair of 1930's (that's pre-war!) pushrod Jag blocks for stroker cranks. All in a day's work!

                The 2.6i is running nicely now but needs a fresh rear crank seal, marks it's territory all over and our drive at home is in a right state


                • #9
                  Oh well the engine has to come out anyway, good time to fit 2.6 20v nice Loose the 7A flywheel as you will have to keep the 2.6 one with its clutch which mates with the T25 gearbox. You will need to fit timing pin to 2.6 flywheel, copy 7A flywheel pin position. Will need to mill out small notch in bell housing for speed and timing sensors, which mount on 7A block. Should be no prob for you and good fun: I'am going down a similar road by fitting Quattro WR engine to my blue 2.5. Will fit S2 turbo for better bottom end. Picked up engine yesterday. Off to SA on friday for hols, will try and get those spares, let us know if there's anything else you need.


                  • #10
                    Bloody hell! Will the 091 put up with the abuse? I'm talking to Aidan Talbot about sorting oil pumps (internal or external) to help our bus transaxles cope better with bigger motors. It's about time, nothing new but no-one seems to be doing it afaik.
                    Looking forward to hand luggage goodies!


                    • #11
                      Hi Ian, good thing I've a SA gearbox contact!!! Back after awesome hol with some goodies too. Have you stripped the 20v yet? I've got some new Golf 16v pistons, you could borrow one to see if it would work with your 2.6 conversion? Nev.


                      • #12
                        What distributor is that on the 7a? Looks to be a vacuum/mechanical advance unit that I didn't think ever came on 20vs...atleast not in the states


                        • #13
                          Well spotted, not standard here either. Someone has fitted 10v dissy? with lots of modification as they are totally different.


                          • #14
                            I hadn't notice that dizzy. Wouldn't surprise me as this engine was running on LPG only with no engine loom or ecu!

                            There's various bolts stuffed in things like breather pipes and where the IACV should connect.

                            Very classy...

                            Engine is in front corner of garage and keeps glaring at me, I must make some space and start on it! I've got some seat frames to modify first for new interior layout...

                            Nev, I've just re-read your info on the differences between 2.5 and 2.6 engines.
                            82.5 bore x 92.8 stroke on a 5 pot gives 2480 cc...that's 2.5 k-jet engine. The printed spec. in the 2.6i SA handbook is wrong

                            82.5 x 95.5 gives 2553cc of course. Time to put a tape measure on the 2.6 block, I bet it's the taller diesel one!

                            I suppose I'll have to pocket the OEM 2.6i pistons if they're OK, unless a playing around with rod lengths and comp. heights works out. The 2.6i does have a unique SA "22S" part number for it's rods, so may have a different length?

                            I can't pull the top off the engine to check, as the 2.6 is getting me around on a daily basis

                            Looks like I'll be be trawling the engine shop's piston catalogues after all!
                            Last edited by 95 Microbus; 24th February 2012, 13:08.


                            • #15
                              Not much progress on the engine, still chopping about seat frames to get this (probably unique) twin folding arrangement finished. But it's not a camper!!!

                              It's gone from this:

                              To this. Should have the new mounting frame made soon:

                              One encouraging bit of news:

                              I finally remembered to measure the height of the blocks. Straight down from the engine number boss gives an identical dimension of 280mm on both the 7A and the ADV

                              So I'm reckoning the 2.6i must use a shorter rod to get it all in.

                              I really need to get an odd ADV piston to get some flat-tops made (or info from SA on deck height and pin size) without stripping the motor prematurely...
                              Last edited by 95 Microbus; 22nd March 2012, 08:32.