cooling efficiency between the 3.3l turbo and 3.0l NA
 

Hello all,

Reading the MANY threads regarding the air cooled 911 engines (specifically the 78-83 years), there was one thing that has been bugging me. I am curious to know why Porsche chose to place cooling fins on only the bottom side of the cylinder for the 930? This seems counterintuitive to me since they reduce the cooling area while increasing power output.

Maybe to make up for this loss in cooling efficiency, they increased the flow rate of the fan when compared to the 3.0L?

Porsche fan specs:
3.0L - 1:1.81 drive ratio - 1380 l/s @ 6000 Crank RPM
3.3L - 1:1.68 drive ratio - 1500 l/s @ 6000 Crank RPM

I have searched threads relating to cooling or cylinder head temps, and the only thing that I came across that was a little helpful was this (where I found the fan specs).
http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/489193-porsche-turbo-engine-cooling-issues.html

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.

Dan

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Fins enhance convective cooling and you want to equalize cooling as much as possible around the cylinder and especially closer to the combustion chamber.

On the top the fan blows directly onto the cylinders to equalize the cooling effect they enhanced the cooling on the bottom and top vis differentially sized fins, turbo also used a higher temp alloy than on n/a, RR530 wasn't used on n/a until the 993 series

3.2 n/a used the higher fan speed too
http://forums.pelicanparts.com/uploa...1576684195.gif

Bill, thanks for your reply and the fan airflow info. What is the speed value in the table, air velocity?
Dan

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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.

Not true
here's a 993 GT2
http://forums.pelicanparts.com/uploa...1577040980.jpg

92mm Mahle
http://forums.pelicanparts.com/uploa...1577041131.jpg

and what happens when things go wrong
http://forums.pelicanparts.com/uploa...1577041131.jpg

Looks finned to me. No chance of mistaking that for a 930 jug:


http://forums.pelicanparts.com/uploa...1577046582.jpg

One question of the use of the RR530 alloy. Was this used since the beginning on the 930's? Or was this only used when the 3.3l's came out?

RR350, Bill typo'd it. Also used on 993s. I've never seen an answer as to whether the 3.0 930s had it or not, but many discussions here of RR350 over the years.

Also info on Wikipedia (as it was developed before WWII and used on many aero engines - the "RR" stands for Rolls Royce, who developed and still license it).

Many have started with SC or 3.2 heads to make insane power levels on both street and track cars; less metal to remove. No-one has reported them melting in forced induction applications.

Just did a different search looking at PN's and found this thread.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/776570-2-8ss-build-3-0-turbo-engine-questions-2.html#post8059854

So guessing the 930.104.341.2R was used on the 3.0 and the 930.104.341.3R on the 3.3's. If that assumption is true then the 2R does not use the special alloy, since it has a "Y" stamping instead of the "RR350" like on the 3R.

Also it seems like the 3.0l were fully finned looking at the thread below?

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/1017445-930-50-engine-sale-1975-turbo-3-0-a.html

RR350 wasn't used on the 3.0 turbo, also fully finned cylinders.

Just found this thread (again) while looking for something else...

It seems that various smaller "S" motor cylinder heads, 3.0 turbo heads and 935 heads had a "Y" designation cast in (same location where the RR350 is cast into 3.3 turbo heads). This indicated the use of "Y-alloy" - early911sregistry forum thread with pictures: Y-alloy heads? Your 2.4S has 'em

Wiki says "experimental series Y" alloys, aka "Y-alloys", were developed during WWI: Wiki Y Alloy.

Further development during the late 1920's led to the series of Hinduminium (High Duty Aluminium Alloys), aka the "RR alloys" Wiki Hiduminium - of which RR350 is a member.