Engine cooling...Heads vrs Cylinders, what item is more of an impact ? Options

[Mueller]

So what item?, the heads or the cylinders have more of an impact on engine performance and longevity when properly cooled?


If someone had a bolt-on kit for watercooling, would you rather have watercooled heads or watercooled cylinders?

What temperature do the cylinders get to while the engine is working?

[scotty]

This should make for an interesting thread... Didn't Porsche start out by cooling just the heads on their race cars?

[Katmanken]

Muller,

My money is on heads. They are exposed to half of the flame front during ignition and they get ALL of the exhaust gasses. That wussy cylinder only gets exposed to a hot ball of exhaust as the piston drops ...and not all at once.

Also, as the piston drops to expose more cylinder, the pressure in the cylinder is dropping and the charge cools a little from expansion. Thus, parts of the cylinder never get exposed to the temps that the head does

Thats my story and I'm stickin to it. (IMG:style_emoticons/default/blink.gif)

Ken

Pull the pin, drop and run.....

[fiid]

I've got to go with heads. That must be why they have much more surface area of finnage on the 914, and also why sodium valves were used on the 2l.

Some head will be conduced to the head from the cylinder if we are talking about trying watercooled heads on a Type 4, plus the lack of air flowing throught he head will provide more airflow through the cylinder fins, so I think it may be quite an effective motor. Plus it will be porsche club legal.

Fiid.

[ArtechnikA]

Didn't Porsche start out by cooling just the heads on their race cars?

yup - and motorcycles too. if you want to see max HP/cc normally aspirated, go look at what those guys are doing. and you -know- they had an uphill battle selling all the ancillary water cr&p (rads, hoses, reservoirs, header tanks, pumps...) to the motorcycle people. IIRC (could be wrong...) Honda or Yamaha were the first to go with water cooled heads on the racing bikes. everybody said 'no way' until they started winning all the races...

[URY914]

Heads-hands down.

[ChrisFoley]

The heads are already oil cooled to a greater extent than the cylinders.
The cylinders are under more stress than the heads and if they overheat the rings won't work anymore. Also since cast iron doesn't conduct heat well the cylinders will heat up more than the heads with a temperature differential (inside-outside) of over 1200F.
It is well documented that switching to aluminum cylinders (Nickies) will lower the head temps as well as having other benefits. I can't see any point in going to all the trouble of watercooling unless you want to achieve power outputs of close to 100hp per cylinder.
LN Engineering claims that engine lifespan is greatly increased by switching to aluminum/Nikasil cylinders.

[Andyrew]

I can't see any point in going to all the trouble of watercooling unless you want to achieve power outputs of close to 100hp per cylinder.

Who's getting 400hp out of a type 4?

Or did you mean liter, ie 200hp?

Andrew

[ChrisFoley]

Who's getting 400hp out of a type 4?

AFAIK no one, but Porsche 6's in race trim can make more than 600hp.

I believe Jake Raby has a T4 project on the drawing board that will be well over 300hp N/A, and air cooled.

[redshift]

I say the jugs, what Chris said.

I want to investigate lowering the air pressure under the engine more.



M

[thesey914]

I've never heard of a cylinder temp gauge but i know there's such a thing as a head temp gauge

[redshift]

So, what can you do to an alloy head to make it cooler? Mount it on a cooler cylinder? You'd have to do something about them, and it seems like that would be the obvious first step, the weakest link.

Cast iron is good for cooking, it holds heat like a jealous bitch.

No offense to all the jealous bitches out there.

(IMG:style_emoticons/default/smile.gif)


M

[Dave_Darling]

Heads, all the way. From all reports, cylinder cooling is more than simply "adequate" if you switch to aluminum cylinders. Nothing else is needed. Now the heads, on the other hand.... They're already aluminum, and they need still more help! Giving them a nice aluminum heat sink (i.e., an aluminum cylinder!) helps them, but they could use more yet IMHO.

'Cause then we can go four-valve!! (IMG:style_emoticons/default/biggrin.gif)

--DD

[redshift]

But Dave.... I don't have alloy cylinders to start with.

The heads are the weak link on our cars for many reasons.. just guessing really, but I think mounting the heads on a better heat sink would bring the mean temps down.. there is a very small break-point in head temps vs mixture density, right.. every BTU helps.. (IMG:style_emoticons/default/smile.gif)

We need to set up shop in Peenemunde..



M

[Dave_Darling]

No guess-work required. LN Engineering and Raby have both done testing on Type IV engines. The ones with aluminum cylinders (LN's "Nickies") have run cooler head temps with no other changes. (Well, no two engines are ever going to be completely identical, but no other major changes.) The aluminum heat-sink, I believe, is what helps the heads cool a bit more.

The original talk on this thread was water-cooling. It isn't needed for the cylinders IMHO--a cheaper solution is available, just get "Nickies". Water cooling probably can help if done on the heads.

Plus that's the way the Porsche Factory did a number of their Turbo motors. (IMG:style_emoticons/default/biggrin.gif)

--DD

[maf914]

Porsche went to water cooled heads on their air cooled racing engines when they went from two valve to four valve heads. Too much stuff in the way to allow enough cooling fin area for air cooling. I can't remember if this was done for the still-born Indy project and transferred to the later 936 cars or was a 956 developement.

Mike

[Brad Roberts]

The piston rings only move in a 71mm area at the top of the piston bore (which is why the fins are bigger at the top) on a 2.0 engine.

Heads.


B

[airsix]

I look at it this way. Review Porsches history.
(over simplified)
First they built engines with iron jugs and aluminum heads. This got them to little more than 40hp per cyl. (early six) Porsche has NEVER gotten huge power out of an engine with iron cyls. They don't shed heat.
As HP increased the iron jugs were replaced by aluminum. This got them to as much as 75-100hp per cyl. (911turbo-917)
To get past the 75-100hp/cyl. cooling limit they watercooled the heads (935-959) for upwards of 125hp/cyl.
Then the 962 got watercooled heads AND cyls and could manage 125hp/cyl. and could do it for 24 hours straight.

(this was all off the top of my head so correct me if there are any errors)

So it seems to me that first you need aluminum jugs, then you need watercooled heads, then you need watercooled everything.

-Ben M.

[Jake Raby]

Cooler cylinders translate into cooler heads- period.....I have done the testing......Cooler temps result in better power and better fuel economy.

[fiid]

So we all hate cast iron cylinders. How tough would it be to add a water jacket to these??

My only objection to Nickies is the cost - and the fact that they can't be machined when they are done with how ever long they are good for (is that correct??).

If you are going to run a water circuit, it wouldn't be hard to add cooling for the cylinders once they are able to do something with the water.

Possible? Not worth it?

Fiid.