fredag 27 juni 2014

What you always wanted to know about the WW Okrasa kit

The launch of the Wolfsburg West Okrasa kit was a game changer in the world of VWintage Speed. With a complete kit to a competitive price Wolfsburg West has done a great job. Their replica is in most cases very accurate. Some things are not exactly as the original, perhaps there are technical reasons, or perhaps it is a compromise to get a decent production cost. However, those wanting to bolt-on the kit as-is on a 30/36 hp engine might want to know what effect these changes will have to their motor.

  1. The venturies
    The original Okrasa kit had Solex 32 PBIC carburetors with 23 mm venturies, as opposed to 21.5 mm in the stock 28 mm unit. In the TSV1300 kit Okrasa did increase it to 24 mm. But according to the information I have seen Wolfsburg West uses venturies  with a whopping 26 mm diameter. This is what Porsche did use for their high-RPM 70 hp pre-A 1500 Super engine. Thus, the replica carb is good for those who want to further hot rod their engine. But for the bolt-on crowd using stock displacement and cam this is rather big.

    Bigger venturies means a lower velocity of the gasses, which results in less power at low-end rpm's. If you have a heavy full-bodied street driven car with a small 1.2 l engine this is not what you want. Thus, a replacement of the ventuires is to recommend if you want the performance to be as Okrasa intended.
  2. The combustion chamber
    As recently mentioned the normal Okrasa head for the bolt-on kits had either 40 or 42 cc combustion chambers giving a compression ratio of 7.2:1 respective 7.5:1 with a reasonable deck height. Wolfsburg West claims 7.5:1 in compression when they advertise their kit, however according to two independent sources (at the combustion chambers of the actual product sold is 45 cc.

    With a decent deck height you will then arrive at a compression not too far from the stock 6.6:1, which is rather conservative if you want the kit for more than looks. I don't know the reason why WW did chose to have larger chambers. Was it a compromise for manufacturing, an attempt to keep customers heads running extra cool or did they forget the deck height volume in the calculation?

    In any case, if you want original Okrasa performance it's a good idea to cc the heads to see if any machining is needed to arrive at the desired ratio.
Don't get me wrong, I think the WW kit is a great initiative, but as usual in the VW aftermarket world you need to check what you get and modify as needed.

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