Racing: 1.8T engine cooling options

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walterclark
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Re: Racing: 1.8T engine cooling options

Post by walterclark »

Its hard to tell much about pressure from yarns unless they are attached at the edges of holes (in this case in the hood). You can get airflow direction and evidence of turbulence.

This simplest analogy to the front end is a wing. A high pressure area is created at the front of the wing and as air moves over the top (the longer path in this case) it creates a low pressure area.

Image

Of course a car's shape isnt that simple. But the high pressure at the front still exists as does the initial low pressure above that (over the hood).

Image

If not for the windshield, the entire hood area would be low compared to the surrounding air, but the windshield creates another wing leading edge sort of thing at its base so there is a high pressure area there and part way up the windshield.

Here is another representation which is fairly typical.

Image

Arrows pointing away from the body are low pressure and toward are high.
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Re: Racing: 1.8T engine cooling options

Post by Super1303 »

If I may put in my thoughts.
Living in the world of automotive diagnostics and tuning things that never meant to be tuned, I learned, changing to many things at once things can get weird.
You bought a new radiator with 30% more cooling.
Before cutting holes here and there, shouldn't you see if this cures your problem first?
You might cause other negatives that might be unnecessary if the job was taking care of by the radiator upgrade.
Each case is different but why chase your tail by not know what is causing what result?
Ether way, this is becoming an interesting thread in aerodynamics.
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Rabbit Farmer
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Re: Racing: 1.8T engine cooling options

Post by Rabbit Farmer »

Thanks, Walter. I had the correct understanding where on the hood the heat can be pulled from under the hood.

Evan... you are correct. I am driving the car at Okemo this weekend with just the new radiator and some taping off of some of the holes around the radiator. We will see how that works.

Next, we are working on a water sprayer. Between the two, that might be the solution. I might still add a small vent over the turbo to let radiant heat out once I get to the top of the hill.

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Coupla thoughts

Post by Mopar 151w2 »

A) Is it possible there is an air lock somewhere in the system? The "secret" to cooling several P-1 cars has been the use of a pressureized expansion tank, like so (RIP Speedy Bill)Image I know that some VW's have an expansion tank, and some do not - how do you test the function of a VW cap, and how does coolant recovery play into this? What I'm trying to say, is that getting all the air out is a big f'n deal. If there is not an air bleed at the high point in the system, you need to add one.Image maybe withImage A bonus - so many drag racers fell in love with Sirocco radiators that there are quite a few accessories, etc available in VW sizes.

As far as static cooling of the turbo - what about "forcing the issue" with an electric fan? Image Like this 8" AFCO (for oil coolers, maybe?) I bet you could air-pop corn at the top of Burke!
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Re: Racing: 1.8T engine cooling options

Post by RacingFrog »

I don't have experience with that specific engine but here are some thoughts:
Rabbit Farmer wrote: The car runs hot when racing it. I have turned on the heat in the car (full blast) to help with the cooling; the car is at 190-degrees (normal temperature) per the stock gauge at the top if I have the heat cranked; closer to 210-220 without it.
This is really surprising because heater cores are really small and don't do anything in cooling down the car besides just making the coolant path a little bit longer (and therefore a little more coolant in the system). Just having the setting to full heat without any fan blowing is probably going to give you the same results.
A first thing we do on Corvettes is to change the thermostat so that it opens earlier (usually 160F). A bigger or better radiator than stock can help if you can enough air to go through (that means absolutely no leaks around the radiator so that all the cold air can go through).
In my 69 Vette (known for cooling issues) having a 160 T-stat, aluminum radiator and an additional pressurized expansion tank (to have more coolant in the circuit) completely solved all cooling issues.
We'll see how my wife's Audi 2.0T will do at the hill!
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Re: Racing: 1.8T engine cooling options

Post by Rabbit Farmer »

John.... the high point on the system is the expansion tank. How do I know the cap is working properly? I don't. I do not believe there is an air bubble.... but I don't know that.

Turning on the heat inside the car is very effective; never tried it with the fan turned off.

I am now running a larger radiator, water/water wetter, gutted thermostat, new fans (still stock), new thermo switch (old one worked, but since I had everything apart), new upper/lower hose (not that it has anything to do with efficiency of the cooling system), blocked off some of the holes around the radiator to help force air through it, etc.

Also... working on a radiator spraying system using my old water/meth pump and tank.

I believe that changing the radiator by itself should be enough to take care of the problem.

Thanks for everyone's input. Appreciated.

Steve
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Re: Racing: 1.8T engine cooling options

Post by Mopar 151w2 »

Gutted thermostat sometimes cures an air pocket - For anything not run in hard winter, I drill a couple 1/8" holes in the thermostat, so it won't trap air, and keeps a little circulation thru the radiator, etc. 8-)
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Re: Racing: 1.8T engine cooling options

Post by walterclark »

John - the VW and Audi include the expansion tank within the cooling loop (usually at the "top") and the "radiator cap" is a one time use thing on the tank - vents once and you have to replace it. Almost any air in the system will end up in the expansion tank. I know my Audi A4 has an air purge fitting added to one of the heater lines because they didnt locate the expansion tank tubes that well so the heater lines end up being the high point.

Great tip on the thermostat. I had an airlock on mine (at the bottom of the system) for the first time in 10 years after reassembly last year and the T-stat wouldnt open so the system would not circulate or purge itself. My first solution was to backfill from both sides of the T-stat and later, when I had the engine back out, I drilled a bypass hole in the T-stat and hoped that would solve it for good.
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