hi !

AM a bit confused, about I came over 2 size of piston for the xu9j4 1905 cc engines ..
1- 83 mm
2- 83.5 mm


I see my engine code is DC 6.. How can I knw whether its 83 or 83.5 mm piston in it ?


Regards
Snave

All 1905cc Mi's were 83mm bore x 88mm stroke.

What you've probably read is that you can bore the standard (usually worn out) liners to 83.5mm which of course requires a set of aftermarket pistons & that increases the capacity to 1928cc.

BTW. You can bore the liners a little further to 84mm which takes the capacity to 1952cc if desired.

To be clinically anal, they are actually three XU9J4 piston sizes. The smallest is stamped A, B in the middle, and the largest is C. They are all nominally 83mm however. I always throw the A's and B's in the bin, but keep the C's when I strip an engine.

The D6C piston also has a Z stamped in it, whilst the DFW is stamped X.

aha! I was about to ask how to identify my pistons!

they're D6C A's, the smallest size I take it? shouldn't be too much of an issue in low mileage liners ?

I just blown my engine ..i think was due to oil surge or fuel ... damn it I wanna cry .. it make a huge noise katakatakataakkataa .. ( think conrods has been gone too..
now heading toward wossner forged piston and will have to check the crank shaft too..

dont mean to be a c**t but my moneys on the crack bein knackered

Sorry Pony I dnt get your point !

Anyway mate Im down to go for forged pistons, standard 83mm pr put 86mm. wat do you think .. ?

http://wossneronline.com/forged_pistons/in...products_id=168

I think pony means that along with spinning a big end bearing (as it sounds like you have) & this usually, but not always it results in a cooked crankshaft too.

If you've got a 1905cc Mi, then you're restricted to 83, 83.5 or 84 mm bore, the max safe limit liners can be bored to. 86mm bore requires new liners & block machining.

You may not need to go to the aftermarket forged pistons route if your Mi16 engine spec is 'DFW' (9.7:1 CR) making 148 hp (108Kw), & get a set of 'D6C' pistons ( 10.4:1 CR) that make the 160 hp (118Kw) these engines are most known for. It's a much better base to work from.

Hi Jeff

Thanks for clarification,
Another question
How would I knw if my My16 is DFW or DC6, coz I had a look and it's written DC6

I do think its a DC6 have just taken a pic of it..



I do think DFW was the mi16 for america, jap and australian market because of low emission issues..


With the DC6 can i go for 83.5 piston without having to rebored the block ?

You're in luck! You have the higher CR engine so, unless your liners are worn out, there are many tuning options which are only limited by your budget. You can't fit 83.5mm pistons into a 83mm bore. The liners will need machining to 83.5+ piston-to-bore clearance.

See-http://www.pumaracing.co.uk/pug16v.htm for further tuning options.

If however, you still want to up the CR further, 2 options are available-

You can skim (deck) the block & liners to achieve least 10.8:1 CR, or go for aftermarket pistons as I did with Wiseco, up to 11.5:1 forged ones).

If you PM petert, he may be able to give you the spec sheet for some high CR Wiseco forged pistons or talk to Woosner & see what's available.

Thanks a lot JeffR !

Hello to all,
I would like to inform me if it is safe to rebore the liners in 84mm or even in 85mm.
Wossner has 83, 83,5 , 85mm pistons(XU9J4).
Where you could find forged pistons in 84mm?
I would like to know,also,the max.safe lift of cam,using the original pistons.
How much it is possible to machine the original piston heads,to welcome bigger cam lifts?
Where I could find(economic) stronger valve springs and solid valve lifters?
Is it easy to midify the hydraulic lifters in solid ones?
Are they some drowings?
I am owner of a Citroen Visa GTI,transforned in 4WD,using the D6C engine(with ph2 Newman cams and throttle bodies) and the transmission system of the 405Mi16x4.
Thanks in advance,
Kostas.

84mm yes, 85mm no. Why not just use 83.50mm? Wiseco make 84mm. Iapel also make pistons. The problem with all of them, although I haven't seen a Wossner piston, is that they don't centre the conrod like the standard piston does. This means you still have some machining work to do if you're going to rebuild your engine correctly. This involves machining the inside of the piston flat and making thrust washers to control the side float.


http://www.taylor-eng.com/images/pistons/c...ust_washers.jpg

I'm rebuilding two 1.9 engines at present with 83.50 Iapel pistons. They have very deep valve reliefs that would accommodate huge cams. Unfornutately, this is detrimental as it comprises CR. If installed in a std. block/liner, they're only 10.8:1. I decked the block/liners to achieve zero deck height and bring it up to 11.25:1.

The pistons I designed for Wiseco a few years ago are much better in this respect. They have shallow reliefs, a touch deeper than standard, which means you can control the CR and valve/piston clearance as required. The part number for these:

83.50mm 10686-5216 (0.150" Intake Depth - gives 0.195" total valve/piston clearance)
84.00mm 10686-9295 (can't recall the Intake Depth)

Maximum safe lift on the standard piston is 0.110" lift @TDC (assuming 0.080" safe limit)

Catcams make a good replacement spring, but you need to shim it up slightly if you don't use their retainers. (contact QEP)

Yes, you can convert the standard lifter to solid. Or, buy new ones from Arrow.


http://www.taylor-eng.com/images/pistons/i...iston_liner.jpg