low compression pistons on a 2.1 DJ

[PetenAli]

I'm not sure yet if I am going to reuse the pistons and liners that came out of the old 2.1 DJ that i am rebuilding. If I buy new part of the trouble is the cost of the high compression piston / liner kit. The best price I've found is about 700 euros plus shipping from Germany.

I was thinking today about using brand new MV low compression pistons which seem to be much more readily available and about 2/3 of the price of their high comp counterparts.

If I did go down this route I know I would lose some power but don't think I would lose too much torque which is important to me in a heavy Syncro. I guess that I would time it at 5 degrees BTDC instead of 10 degrees BTDC and use ordinary unleaded instead of the higher octane.

I can't see that this would be a problem if I retain the Digijet system from the DJ but does anyone have any observations on this idea?? I can't find anything on the Wiki but if this has been discussed before it would be good to read the thread.

Thanks,

Pete

[Aidan]

if you go with the low compression pistons then probably best to go to the MV ECU and loom with lambda that way the ecu can change fuelling and timing with feedback from the lambda, running an MV as DJ will be an even more compromised setup as the ECU has the DJ map and that's it

imho running a DJ on unleaded 95ron at 5' it probably has no more power than the MV, you can forget the 112bhp anyway as that was for unleaded at 10' - as stated imho - if someone wants to rolling road a van at 5' on 95ron supermarket fuel then I stand to be corrected - the only vans I know have been tested were running 98 SuperShell at 10' and got something like 108/109bhp on old engines, extrapolated, on 4wd roads, both syncros

shame we haven't got a tame rolling road owner in the club - would love to see some of the diesel 'upgrades' tested and see what they really make and how (eg AAZ fitted with 90% JX stuff), it would be useful to know from a gearbox point of view too

[kevtherev]

shame we haven't got a tame rolling road owner in the club - would love to see some of the diesel 'upgrades' tested and see what they really make and how (eg AAZ fitted with 90% JX stuff), it would be useful to know from a gearbox point of view too

I have to agree there Aidan.
I too would like to see what a carburated 2.1 would produce...with both a pierburg and a twin set .
Plus throw some LPG in and we could get a nice clear picture of the petrol side of a flat four engine

[PetenAli]

Thats really helpful Aidan - thanks. I wondered why I couldn't find if anyone else had tried this! Swapping to the Digifant set up would probably be even more complex for me so I may have to bite the bullet on the DJ pistons / liners. I'm going to do this rebuild but I'm learning a lot on the way - not least how expensive parts are when compared to air cooled!!

By the way, I wouldn't run a DJ on 95RON and 5 BTDC. I learnt that the hard way in my early months of ownership and with advice from Syncrosimon. I was only thinking about changes that would be necessary if it had been viable to fit the lower compression pistons. I always time my current DJ at 10BTDC and use 98RON - in fact I'm just off out to check the timing and other things as we are off to the Lakes next week.

[Aidan]

swapping to digifant pretty easy just swap the loom and ecu and fit a lambda to the exhaust, I have spare set up, wiring and ecu complete