Rob Edwards

Randy-

Good question- I'm going to try to convince Greg to let me take this intake off at home when I swap it back to stock so I can see how long it takes. My bet is it'll be 6-8 hours for me to do the swap. I've done two intake R&R's this year already (1 to install the Alpha N stuff on the GTS, and one on the GT, pre-sale, to chase possible vacuum leaks), so the stock intake setup is pretty straightforward by now.

It's going to go back to stock much sooner than the next smog due date (May 2014) so that Greg can get to work on replicating the setup. Likely shortly after we get to the dyno, hopefully in the next week or two.

danglerb

I'm not following what it is that happened.
When cold the pump circulates within the block.
When warm it transitions to drawing from the radiator.
Both modes the pump runs the coolant through the block before it goes to the radiator, what is the source of excessive pressure and why didn't it vent from the overflow tank?

John Speake

I think it going to be more than 125rwhp up on the stock intake power.....

69gaugeman

I'm sorry, but I am trying to get my head around this. If it is true that the water pressure of the pump caused the crimps to move then every 928 I have ever driven in should have leaking radiators. Who here hasn't run up to red line before the thermostat opened? Having extra HP does not change the way the pump works.

Now over heating is different. But usually the cap will release or the expansion tank will be sacrificed before the radiator.

I suspect something different was the cause......most likely a manufacturing issue or a cap issue.

davek9

IMO that rad left the factory with bad tank crimps, it's not the first one I've seen.
Brand new, bad, failure w/in 2k miles.

Dave

GregBBRD

In our theory, rate of acceleration is one of the factors. This engine changes rpms faster than any 928 engine I've been around.

My radiator repair guy has been fixing radiators since the dark ages. He claims that there is "localized" pressures within a cooling system. He says that the old "soldered on" tanks would bulge and pull loose the solder joints on the hot side tanks, when there were localized overpressure situations....and the cap would never open.

This is all new, to me, also. I'm not making this stuff up, as I go.....there's plenty of that, in the 928 world, already. Rob's tank was obviously pushed up and leaking. I figured it was a defective radiator. My "old school" radiator guy took the time to tell me what his experience has been, over the years. Just passing that information on.

GregBBRD

See post #21.

As far as failures with new Behr radiators, while anything is possible.....I'm going to guess that I've put in more of these than anyone, other than the Porsche factory.....and I've never seen a single failure.

GregBBRD

Randy:

If this intake does what I think it will do, combined with my exhaust system, to the 5.0 and 5.4 engines, we will certainly be applying for a CARB exemption.

My stroker engines are so clean that they can virtually pass the California smog test without any cats. No reason to think we can't accomplish the same thing on a stock engine.

All part of the plan......tiny steps, when self funded and not independently wealthy.

davek9

I've got pics of a brand new rad w/ bad tank crimp. A full refund was provided to the owner, it was on the left side, so the right side is not out of the question.

That aluminum is stiff, doesn't bend easy, I'm thinking u all were smoking more than rubber if u think that the water pump did that

GregBBRD

I'm not intentionally trying to make everything you say seem contrary....I'm just passing on what I see and what I'm told.

Actually, the aluminum on this new radiator is like butter and bends very easily. There was absolutely no chance any of the tabs would have broken off.....very flexible.

My "old school" radiator guy things the aluminum might get harder, as the years pass, which is possibly why the aluminum on the older Behr radiators is so stiff. He also mentioned that it is possible that materials have evolved, since the original Behr radiators were made for these cars, some 25 years ago. He says that on the current Ford and Chevy radiators with plastic tanks, one would have to work very hard to break off any of the tabs. The aluminum is very flexible and can be bent back and forth many, many times without breaking.

danglerb

Maybe something like water hammer?

Some valves shut off suddenly and send a pressure spike back up a water line hard enough to make the pipes "ring". We had a boiler like that and had to put in a vertical air filled pipe near the valve to cushion the shut off.

Simple test might be to use both hands and squeeze the in and out hoses to the radiator while somebody blips the motor. Blips are a bunch more rapid than any runs in gear.

On a not warmed up motor, a blip might also rapidly close the thermostat as a dose of cooler water comes from the radiator.

69gaugeman

Well, I am still not convinced. I thought about the acceleration in the water pump too, but two factors limit this theory. One is that it is an impeller style pump with quite a bit of clearance. Like a turbo charger it is inefficient at low revs and builds as speed occurs. The total amount of possible pressure is limited by design. Even if you accelerated twice as fast the pump has a design limitation. Now, to be fair I am not sure of what this limitation is, but I am sure there was a lot of thought when designing it at Porsche.

Anyone have a rad they want to blow up? Run a pressure test to failure and see what pressure will do it. Then stick a pressure gauge in Rob's car and see what is generated there. It will certainly prove or disprove this theory easily.

69gaugeman

If you have ever seen a thermostat operate you will understand that even from 100 C to 0C it operates quite slowly. You must remove the heat energy from the spring and that takes quite a bit. No water hammering there.

Speedtoys

Not the spring, the wax pellet inside a metal container that expands and contracts..that takes a while to absorb and shed heat...heat doesnt change the spring at all.

69gaugeman

Yes. That's what I meant. Thinking faster than I can type. But the point being it works slowly.