Quote:
Originally Posted by Mixed76
Hi all,
Looking for the same information as the original poster. Anybody know why the turbo cylinders have hardly any cooling fin area? Seems like turbo cars make more heat and more fin area would have been provided.
|
When I first saw a set of 3.3 cylinders, it reminded me of air-cooled drag racing mills - common at one time to remove finning for faster warmup on nitro/blown setups.
That thinking may have been a factor. But Mahle didn't do this with their 3.4 kit for 930s, factory didn't with any turbo after the 3.3, and L&N Nickies are fully-finned. And many guys have run 3.2 cylinders or Nickies in high-output forced induction applications without issue.
So it would seem that whatever made the factory think it was a good idea was disproved.
A lot of things with the 930 were apparently (from Stark's book, I think) based on the factory originally thinking these would all end up as track rats flogged by racing drivers - and that they might struggle to sell enough for homologation (which they had to get for the 935s). So they were apparently astonished (and delighted) when the turbo sold strongly to people who drove them on the street.
It's clear the factory over-engineered a number of things. Which certainly became clear to them after a few years of production. However, many things in the 3.3 930 were retained unchanged across the entire production run, because apparently significant changes would have required a complete smog re-test. So only incremental updates for emissions.
For example, the very last 3.3 930 motor in 1989 still came with the very cold (and insanely expensive now) platinum W3DPO plugs. Which luckily, last well, run great and never seem to foul even in street usage (well, mine never have). Factory didn't use those in the later turbos either - the 965 (still a 3.3 motor) went down a heat range, and the 3.6 turbos went down to a 6...
And the 3.3 965 replaced the ~10lb magnesium recirc valve casting with a plastic Bosch part weighing an ounce or two and a rubber elbow instead.