TDI Cooling System Upgrades

[Piwoslaw]

Originally Posted by Deezler

But honestly I'll probably never buy a larger inter-cooler for this car. It's just not worth it. Unless I find a good deal on a used one.

Question: If there is room for it, would a second intercooler, hooked up parallel to the first, be of any good? It would reduce drag, plus give better cooling since the air inside is moving twice as slow. It probably wouldn't be worth buying a new one, but maybe if you could get a cheap used?

[Deezler]

Piwoslaw,

This has been done before by a few folks. One guy had a scoop molded into his hood to direct air down over a second stock inter-cooler. But he didn't keep it that way for long... I think the additional cooling benefit is partially diminished by the extra pressure drop you get in the system. Having one larger intercooler definitely seems like the way to go.

Some cars, like the Audi TT, split the charged air coming from a single turbo in a y-pipe and send it to both sides of the bumper for dual, parallel intercoolers. This seems like a lot of extra piping volume to me... But the pressure drop is probably lower.

[Piwoslaw]

Deezler, That's what I had in mind. If instead of one intercooler you have two of the same size, all ducts have the same large diameter, and the IC's are connected in parallel, not series, then the pressure drop should be smaller than with only one IC. Sort of like connecting resistors in an electrical circuit. Two intercoolers in parallel should work as well as one big IC, plus the two might be easier to fit into the engine bay. I don't know whether the benefits from that set-up would outweight the extra room and weight (assuming the second IC was scraped from a used car).

[Deezler]

Well,

One important note: DON'T RE-USE THE FREAKING ORIGINAL O-RING!

My new thermostat didn't come with an o-ring. The stock one looked ok, so I figured what the heck, it's the weekend (dealer closed), my car is torn apart, lets get this thing back together. The o-ring seemed a little loose, but well, it sealed for a week of driving.

Then I get home from Colorado to find my car is scary low on coolant in the airport parking lot. With the bottle of water I had on me, I limped her home. The new o-ring was much smaller and tighter. The original one must have slipped out on install and was horribly mangled. I can't believe it ever sealed at all.

All fixed now. Half way through this tank its looking very promising for FE benefits. I am tempted to re-fill early just to find out. Plus diesel is now finally below regular at the pump!

[COcyclist]

I also installed the Zero-Start (750 watt) coolant heater in my TDI. I use it mostly in winter so it is hard to say if there is a significant increase in fuel mileage. However the diesel engine starts easier when warm and makes full temperature much sooner with the coolant heater. It is nice to have heat in the cabin instead of waiting for the engine to reach temp before using the heater.

I am eagerly awaiting the OMI install. Are you going to start a new thread with a link or add it here?

[Deezler]

COCyclist,

I'll probably do pretty much the same thing. Only run the heater until the morning ambient temps get to about 45 or 50 degrees F. Since I bought a 220V heater (for some reason), I only get my coolant temps up to about 90 F, but thats still nice for a smooth startup.

The OMI install required a few more parts since I am upgrading the entire airbox and mass airflow sensor housing also. I think I have everything I need ordered now, so hopefully I'll get to it soon.

First tank re-fill after the heater and thermostat: 48 mpg. 1.5 better than the last tank. I think that's outside of my mileage measurement error, so I'm pleased.
Hopefully the warmer weather and my continually refining driving style aren't clouding the results too much..