Intercooler 101 -

[Craig 930 RS]

http://www.are.com.au/techtalk/intecoolersMR.htm Overlook the fact that they are selling their own intercoolers........the information here is really good. Helps cut throught the BS and internet-based misinformation. Spend 1/2 hr and read through this stuff - esp if you are looking for an IC. Stuff like this: Most of the charge flows through the bottom 35% of core, with the top 65% causing detrimental pressure drop until high boost is reached. Worse again if other pipe is on the bottom too !! Not perfect, but very good & very cost effective. Nowhere near as important to have diagonally opposite tanks like both designs on the left. Very small eddies & small uneven distribution across core window. Detonation and intercoolers: The most single deadly forced induction engine destroyer (apart from no oil) has two common names :- Detonation or when I did my time at college, Pre Ignition. My interpretation of these is when the spark plug ignites the intake charge, the flame front travels rapidly but smoothly, across the piston face to fill the combustion chamber with the exploding fuel charge & force the piston back down the bore. When something happens to destabilize the smooth travel of the flame front (wrong combustion chamber/piston dome shape, little/no squelch surface, sharp edges, hot heat range plugs, advanced timing, excessive compression, high boost, too low octane fuel,) one or more smaller fronts can start & these then collide, resulting in an early &/or more violent explosion, resulting in the knocking or pinging noise that sometimes can be heard from the top part of the engine. Interestingly, it is easier to hear a standard car/ute ( our terrible unleaded) pulling away from the lights up a hill, than it is a turbocharged car. I have to admit that I lost an engine of mine only this year, whilst testing on the open road (steepish hill) without hearing it. Radio on low & passenger reading data, I felt the engine nose over but by the time I clicked it & coasted to a stop, it was missing on one cylinder - side gone out of the top of the piston - expensive! That quick. Don't pass me off as a dickhead & it wont happen to you, be aware. The boost gauge decided to read at 60% of actual boost sometime just before the testing started, I adjusted it up thinking someone had changed it & it's that simple. The cooler the intake charge - the less chance you have of detonation ! I'm also positive that a consistently stable (air/water is supreme here) cooler intake charge also increases the life of headgasket, valve & seats, top bore-ring-ring land to a noticeable degree, whilst offering considerable more power potential. How important is intercooler selection now ????

[911nut]

Originally posted by Craig911
I'm also positive that a consistently stable (air/water is supreme here) cooler intake charge also increases the life of headgasket, valve & seats, top bore-ring-ring land to a noticeable degree, whilst offering considerable more power potential.

I read somewhere that Porsche abandoned the water/air intercooler after the 934 because as the water heated up the intercooler became less efficient than an air/air unit.

[slow&rusty]

Originally posted by 911nut
I read somewhere that Porsche abandoned the water/air intercooler after the 934 because as the water heated up the intercooler became less efficient than an air/air unit.

I would have to say your above statement is incorrect as pertaining to a street production car.

Air To Water Cons:
1) Needs a separate radiator...where would you mount one on a 911? In the nose, 15feet from the engine?
Under the car - will get damaged eventually?
Cut a hole in the rear arches and mount there - way too expensive!

2) Requires a separate electric pump that is always cycling - more expense, more wiring and more load on the alternator! More things that can go bad.

3) More plumbing and chances of leaks - therefore more maintenance, owner headaches and costs!

4) After around 40mp/h an air to water is just as an efficient as a good air to air.

I only know of one car that came with a factory installed air to water intercooler - the Toyota Celica GT Four from 1988 to 1991 - a very low production car packed with technology but eventually the air to water was abandoned even on this model in favor of a top mount ait to air.

Yasin

[Jim2]

Thanks for the post Craig. I'm just about to start on the I/C for my car and this info reinforces some of my thoughts.

Several months back a friend told me about this site but I ha been unable to locate it.

Jim

[al clark]

If you are running A.C make yourself a refrigerated I/C.bring your air charge down to 50 deg. or so.

[Craig 930 RS]

One of the prime messages I've received from that site - and from other sources a few months back - is stay away from the square end tanks with extreme to one end end inlets/outlets.

Frankly the design doesn't get much worse than that.
Sure are easy to build, however.

[NathanUK]

Originally posted by 911nut
I read somewhere that Porsche abandoned the water/air intercooler after the 934 because as the water heated up the intercooler became less efficient than an air/air unit.

I read it as though they meant water injection with air directly into the engine, not water for the intercooler.

I might be wrong though.

[slow&rusty]

Originally posted by 911nut
I'm speaking in strictly thermodynamic terms but as we all know Porsche used racing to explore technologies for the road products.
If Porsche thought water/air was a great benefit to road cars all turbos would have them today. I'm sure that the disadvantages that you listed weighed in to their decision.

I ONLY speak "strict" thermodynamics - its what I do for a living.

Yes racing was and is used as a mule for Road cars - agreed.

The reasons I listed above ARE the reasons their road cars do not use air to water. Back in 1988, $350,000+ Ferrari F40s rear engined turbocharged monsters like the 911 Turbo used Behr air to air intercoolers.

I can go on and on...but I am already boring and grumpy.

Yasin

[mppickett]

I've had cars with both air-to-air and water-to-air intercoolers and I prefer the air-to-air for all the reasons Yasin mentioned. The water-to-air ICs work fine but are much more complicated to set up so they work correctly.

[Noah930]

I read somewhere that Porsche abandoned the water/air intercooler after the 934 because as the water heated up the intercooler became less efficient than an air/air unit.

I think it was the (racing) rulesmakers that originally banned the water-cooled intercooler. So Porsche had to use an air-to-air intercooler.

[911nut]

Thermodynamics aside, Porsche used the water/air intercooler on the 934 due to space restrictions in the engine bay. The cooling fan was on top of the engine and the tea tray spoiler was not yet homolagated, forcing the location of ther intercooler to the front of the car. This configuration was retained from 1974 until development of the 934 stopped in 1976. Porsche continued to use water/air intercoolers on the 935 until the end of 1977 (taken from "Porsche 911 Story").

[911nut]

Originally posted by slow&rusty
I would have to say your above statement is incorrect as pertaining to a street production car.
Yasin

Yasin, let me edit my response to this.
I was not talking about the practicality of water/air intercoolers on street cars. It is intuitively obvious that they are more complex than air/air.
Since you are the expert here, please comment on what happens to engine fuel/air calibration when the water in the intercooler rises in temperature over ambient (and it will since no radiator is perfect at shedding heat).

[NathanUK]

I don't believe CIS measured temperature of the air entering the engine. What it does do though is measure the volume of all the air going into the intercooler after the air filter. This is what works out the mixture, the volume of air.

I didn't know the 935's used water for the IC's. I know they called some cars the 934.5 as they were updated 934's to 935 spec.

[Jim2]

Here is my latest project. The concept comes from RSR turbos and some 935 variants. During 2006 I did a number of pressure tests around the tail and started devising an intercooler which could take advantage of high and low pressure regions without relying on the engine cooling fan. Just started on this a couple days ago.


Jim

[NathanUK]

Why not just make a ducktail out of the IC

[onefstm]

TPC uses liquid/air intercoolers on their supercharged 911's. They mount the heat exchanger in the tail and the actual intercooler in the engine compartment. For their application, they claim that this design works much better than the air/air. Also, Ruf is using liquid/air intercoolers with their new supercharged motors.

As far as factory liquid/air systems go, you should look at the Ford Cobra, Lightning truck, and GT. With the Cobra and GT, tuners are using the stock liquid/air intercooler and ditching the supercharger for twin turbos. They can then make 600-800 rwhp through the stock liquid/air intercooler. Pretty impressive for a compact stock system.

[1980 911 sc]

there are a ton of cars on the road today that use air to water to air intercoolers. very very rarely does the selection of a stlye of intercooler have anything what so ever with science. space and cost rule in production cars.


LOL look at the stock IC on a 930 it is way undersized for the motors potential...

[Craig 930 RS]

Name a few......I know of none.

[1980 911 sc]

think super chargers and think ford =)

it is all too easy to throw the water IC under the blower

if you go aftermarket there are a ton... ati kits TCP kits

PS Craig, I love your ride

[Lukesportsman]

Ford Lightnings, Harley F150s, Cobras and even that crappy Ford GT all are running water/air intercooler systems. Some of the others you might consider are the AMG Mercedes like the S55, E55 or others. British cars have also joined in this with Jaguar's XJR or XKR. In AU the Holden Commodore is available with a water/air intercooler.

The Ford system (whatever your thoughts of domestic cars) has been proven to have capacity for short bursts of 700hp with nearly minimal change in output air temperatures. I'm not making an argument for one over the other as the air/water certainly has issues but for a street application where there is more time off boost than off it works well. In racing applications the water is going to saturate in temperature and loose its effectiveness versus air/air.