Xu10J4Rs Wossner

[Kapi306 0]

Hi!

 

Someone use wossner K9181DA?

 

In the catalog it has 12.2 : 1 cr with 2.8 cc dome volume, but, a quick calculation the cr with this piston is 13:1.

 

499.55 cc total displacement

37.2 cc chamber volume

7.13 cc gasket volume

2.8 cc dome volume

 

combustion volume (37.2+7.13-2.8)=41.53 cc

 

((499.55-2.8)+41.53)/41.53=12:96 cr??

 

 

 

What do I calculate wrong?

 

[welshpug 1,657]

why are you removing the 2.8cc twice? you only need to remove it from the compression volume not the swept volume, so the CR would be 13.02-1 with your figures.

 

 

not uncommon to see incorrect figures with wossner stuff.

[Kapi306 0]

Twice removing is a mistake ​

 

The problem is :

 

https://www.youtube.com/watch?v=85Lx4TY-En0

 

with catcams 109 at correct timing

[welshpug 1,657]

did you measure the pistons? I have heard of an engine ending up with 14+ -1 compression.

[Kapi306 0]

Unfortunately not

[petert 586]

I've got a set ready to go into an engine and yes, they're approx. 13:1 on 499cc. I'm planning to mill 3mm off the dome.

[petert 586]

Sorry, mine are K9182D050 (86.50) and have a 10.3cc dome, which I've confirmed. The CR with these is 14:1. Taking 3.2mm off the top gets the dome volume down to 3.9cc and a more respectable 12.6:1.

 

Your K9181DA's, if the dome is indeed 2.8cc would be around 12.2:1.

Edited November 23, 2016 by petert

[Kapi306 0]

With 2.8 cc dome 12.2:1 ? How?

but in the catalog the K9182DA has 7.5 cc dome....

 

(499.55+41.53)/41.53=13.02 cr

 

This calculation is wrong?

[petert 586]

Vs=499.55

Vc= 37.2+8.2-2.8

Vc=42.6

 

Where gasket = 8.2cc

 

CR = (499.55+42.6)/42.6

= 12.7

 

I was using a larger chamber volume to get 12.2

 

http://www.flatlander-ipp.nl/wossner/wossner-pistons-peugeot.shtml

[dcc 855]

am i right in thinking you have assumed the piston is sat flush as top of bore, dont you need to measure how far down bore piston is sat? Then add that to the compression height? Also the valve cut out volume?

[Kapi306 0]

So with my wossner piston my cr is 12.6 - 13 if other parts is OE.

 

37.2 chamber

1.2 mm gasket

[Kapi306 0]

am i right in thinking you have assumed the piston is sat flush as top of bore, dont you need to measure how far down bore piston is sat? Then add that to the compression height? Also the valve cut out volume?

 

 

I measured piston cut out volume. its about 4 cc. piston volume = -4+6.8=2.8cc

full dome volume 6.8 cc

Edited November 23, 2016 by Kapi306

[petert 586]

When I measured 10.3cc for the K9182, it was a "nett" dome volume, taking pockets etc into account. Yes, piston was flush with the deck. I did it so many times it drove me crazy. Then I did a CAD model and got exactly the same.

 

I wouldn't trust any Wossner data. For example, they quote 22mm pins for XU10J4 pistons.

 

Flatlander data was correct.

Edited November 23, 2016 by petert

[Kapi306 0]

When I measured 10.3cc for the K9182, it was a "nett" dome volume, taking pockets etc into account. Yes, piston was flush with the deck. I did it so many times it drove me crazy. Then I did a CAD model and got exactly the same.

 

I wouldn't trust any Wossner data. For example, they quote 22mm pins for XU10J4 pistons.

 

Flatlander data was correct.

 

 

 

Ok!

 

Thanks a lot!