924Board.org

[garyw]

I am curious of what value an intercooler really provides for daily driving since it really only makes a difference at higher speeds? I don't live in a country where I can drive over 80 mph (~120 kph) for any distance and the car has enough kick to pass anyway so what do I get out of one other than bragging rights?

Aren't I better off, money-wise, installing a boost control valve and gauge and just uping the boost a little?

Thats another thing. What is the difference between a boost control valve from an auto parts store and a pressure regulator valve from the hardware store? I was just looking at a pressure valve at Home Depot for under $30. It was infinitely adjustable with a lockable cap so that it did not move and it came with a pressure gauge. They certainly look the same.

[macBdog]

An intercooler will prevent detonation when you decide to up the boost. At stock boost levels it is not required... which is why Porsche didnt fit one.

Auto parts store boost control valves are coloured purple, made of aluminium, cost more, and have names like "Super ultra mega turbo smash tokyo jesus fist 5000". Go with the hardware store version, just as good and inconspicious.
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1979 931 with a 350 chev
1973 911E with EFI

[Khal]

[goturbo]

Most people don't know what a mechanical boost controller does so they don't realize that they can get a hardware store variety needle valve and make it do the same thing for a fraction of the cost. That's how they sell the Super ultra mega turbo smash tokyo jesus fist 5000's for elleventy hundred dollars. So the more you know the more 'over the counter' stuff you can get and adapt it to work for a lesser dime-which is good for those of us on thinner dimes

As for the intercooler deal...

I am not sure where you heard that IC's only work at high speeds but that's not really true. As a fact higher speeds produce a diminishing return on overall IC efficency. In other words the ability of the IC to radiate heat to the moving air becomes limited to the ammount of time that the air is in contact with the surface of the heat exchanger. There are many factors that play into that equation but for the most part an IC is still effective in preventing detonation at lower speeds, like say 20-30 mph. So for my daily driver when I go into a curve at 40 mph I want to have maximum power while exiting to accelerate me back up to 65 mph and the IC works just fine. Adding a water washdown to the IC makes it even more effective at lower speeds. IC + boost controller = really funner daily driver.

Bottom line if you want a bit more poke and don't want to spend too much $$$ rig the hardware valve. But if you want to push the boost, get the valve and throw on an IC (wow I just made that PITA sound real easy), for reasonable boost levels it will work fine driving at most any legal speed.

[Glen931]

An intercooler will cool the intake air better at high speeds. there is no deminishing returns. the higher the heat differance the faster the heat is transfered from the intercooler. the speed of the air over an intercooler has no corrilation with the amount of heat that may be transfered. the controlling factors are temp differance(between intercooler and air) and pressure of atmospheric air. heat transfer takes place instantly therfore there is no need for the air to pass over the IC slowly. the increased air flow keeps the temp differance to a maximum therefore cooling the IC more than at low speeds.

"In other words the ability of the IC to radiate heat to the moving air becomes limited to the ammount of time that the air is in contact with the surface of the heat exchanger"

as the speed of the air increases it limits the time for the air to heat up. there is always more air to follow it, so there is always going to be cooler air in contact with the core at higher air flow.


you are correct that it will work at slow speeds as well, but it only becomes more efficiant as the air flow across the core increases. water spray is a good way of reducing the temp of the IC.
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"Nitrous is like a hot chick with an STD, you know you want to hit it, but you are afraid of the consequences"

1980 porsche 931 beige
1987 Porsche 951 red, 51kmiles.. prefect cond.
1978 ford fairmont wagon 2.3 turbo engine

[numbbers]

Well, all of you guys are right to an extent. An air to air intercooler will not help much until you have air flow through it. So, you either need to be moving, or you need to run a fan for airflow. Also, and air to air intercooler, can actually be detrimental on hot days, because the intercooller will heat soak from underhood temps, when the car isn't moving. Therefore, your carge air will be hotter when you are in traffic.

Since these cars tend to suffer on low end performance, right off the line. I believe the best solution is an air to water intercooler with a fan. The water gets cooled when you are moving, or to a lesser extent, with the fan. And, your charge air gets cooled by the water, just when you need it, as you leave the line.
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1980 924 Turbo

[simsport]

Just as long as you have a dedicated water supply for the intercooler as heat soak from the rad makes it much the same as the air-to-air otherwise.
Cheers
Simon
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Blown is always best!

[garyw]

Lots of differing opinions on this. Coming from the far north it seems to me to consistantly keep the charged air cool, you need air flow to draw off the heat. In winter, Canadians call this windchill . So if I am sitting in traffic or at a red light my A2A intercooler would not be doing me much good.

Does anyone know how to build an economical air to water intercooler?

[Darin81T]

haha.... Will you explain to me how you're going to be creating boost while sitting at a red light?

[garyw]

I don't want or expect boost sitting at the red light but I do want as much as I can get as soon as possible. I don't know about you but I spend most of my time driving the car in the city. Not on the highway or a race track. When the opportunity comes to accelerate I want power as quick as possible so I can race to the next red light. If I have increased the boost the intercooler probably needs to cool the air quickly to keep up with the increased pressure. If I am going to this kind of trouble to do this alteration it needs to work in the environment I am using it in. Otherwise why would I go to the trouble of installing it in the first place?

I know that increasing the boost and adding an intercooler does NOT lower the point at which the turbo kicks in, but I also do not want to blow my engine.

[J1NX3D]

mmm i still say an i/c with an i/c squirter is still best for cooling inlet charge with a bit more boost
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'86 944

[MunkPuppy]

[numbbers]

Well, I have a Toyota one that I am going to try to modify and install, but that project is on hold while I am selling my house.
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1980 924 Turbo

[ideola]

garyw, Have you considered adding a water/methanol injection kit? Seems like a less expensive, more DIY-friendly alternative and provides many of the same benefits (simultaneoulsy cooling the air charge and boosting the octane to reduce the risk of detonation). While perhaps not suitable entirely on its own for a racing application, for a street application, it might be the ticket
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erstwhile owner of just about every 924 variant ever made

[garyw]

Thanks for the link I will read through it. Injecting methanol sounds a little scary.

I have been doing some reading on intercoolers. Apparently for every degree they cool the intake temperature the exhaust temp is cooled the same amount. All this in turn reduces the stress on the engine. I would imagine that methanol cooling has the same effect.