Turbo chargers and intercoolers-Pete?

If the flow is free from turbulence, the heat transfer will be MINimised. That is not what you want. You need to make the tubes such that the flow is turbulent enough to effectively remove heat from the charge air.

Laminar flow requires extremely low Reynolds numbers (ie. flow relative to the size of the spaces) and is usually impractical for any real-world heat exchanger. And, laminar flow will reduce heat transfer, since the air in the center of the tubes will never touch the walls.

A differential pressure gauge would easily show the pressure drop. But, you just turn up the boost a hair to compensate.

Jon

You are both right. The point about the ducting is about distributing the incoming air evenly across the intercooler inlet stack and collecting it effectively at the outlet. Bloody headlights get in the way of good plumbing.

If the flow is free from turbulence, the heat transfer will be MINimised. ^^^^^^^^^^^^^ Has anyone calculated a Reynolds number, to see whether laminar flow can even exist under conditions where the turbo is needed?

The book I have ("Maximum Boost Designing, Testing, and Installing Turbo Systems" by Corky Bell ) indicates that plumbing to the intercooler should not have any abrupt changes in cross section, should avoid sharp bends, and should be of sufficient diameter that the speed of the air in the plumbing is below Mach 0.4. Although I would consider it to be common sense the book also indicates that the intercooler should be located such that heat from the engine compartment/radiator is avoided. The book gives an example using "typical" numbers and indicates that a

20% increase in power can be expected due to the temperature change (and density) of the intake air but a 10% loss of power can be expected from pressure drop due to all the plumbing and the actual intercooler so a overall power gain of about 10% can be expected from a well designed system(although he does indicate that with lower intake temperatures detonation is greatly reduced - and I gather that ignition timing could be advanced slightly resulting in more power, but I'm no expert). Overall the book seems to be very thorough in describing all the design possibilities/tradeoffs of a turbo system and I would recommend it.

-Kris

Eric R Snow wrote:

And as a rough guess, on a motor that size, 2 or maybe 2.5" OD tubing would be fine. Keep the bends smooth, roll a bead on each end to capture the hose clamp, and use good hose (for example

and seem to have a decent selection and prices, along with and The t-bolt style clamps and the permatorques seem to be about equally popular. I have an aftermarket frontmount intercooler on my 3.8L V6 Buick, with 2.5" tubing that goes down, back under the radiator, then up to turbo outlet and throttle body for about 7-8' of tubing total with virtually no lag from the tubing, and I push 22-23 psi boost and make about 440 rwhp on

93 octane pump gas (12.11 at 111.0 at 4060 lbs). You can use plain or aluminized mild steel exhaust tubing and mandrel bends, MIG it together, and paint or powdercoat, but it will be a little heavy. Or use aluminum tubing and mandrel bends and TIG or just use hose at each transition if you have to for example, but I don't know for sure that there tubing is weldable). Remember, any intercooler is better than none, and any frontmount (intercooler in front of radiator) is better than almost any other kind, and on my car a good frontmount is worth about 0.5 sec off the et and 5 mph more in the 1/4 mile (about 60 hp) compared to the stock intercooler.

-- Regards, Carl Ijames snipped-for-privacy@verizon.net

From their website:

" Silicone hose is NOT compatible with fuel or oil"

This concerns me because it is common for a turbocharger to blow some oil through. One of the coupling turbo hosed on my Volvo is lightly coated with oil on inside and it also appears that somehow the oil seems to sweat right through the hose because the outside looks oil coated. The turbo is new.

Just shows what I know! How aboutthe experimental planes that inject air into the stream going over the wings to get laminar flow? Is this way less flow per surface area than the air that cars use? Cheers, Eric

Probably. Say the plane is flying at 170m/s, about half the speed of sound. The area of a 5cm pipe is around 20cm^2, or .00025m^2. To equal the speed, you'r looking at .00025m^2*170m/s = .06 or so, about

60l/second. Say a liter cylinder, that's enough to fill one cylinder 60 times a second, or to feed a two cylinder 1l four stroke at 3600RPM. As you can see, it's quite easy to get significant fractions of the speed of sound.