TDI Cooling System Upgrades

[Deezler]

Hey all.

Spent several hours this weekend addressing a couple specific cooling system upgrades that I've had planned for my VW Jetta TDI.

First up, a Zero-Start coolant heater. I found a 750W unit on ebay for 30 bucks that I couldn't pass up. (kind of wish I had more watts, but oh well). Don't ask me why I've had this heater since Christmas but not installed in until now.
Followed an excellent installation write up found here:
http://pics.tdiclub.com/gwillie/zerostart%20install.htm

Plumbed it inline from the coolant-oil heat exchanger outlet:



Fairly tight fit in the engine bay. For context:



Unfortunately, the plug I had for the heater wouldnt fit through my grill blocks, so for now I have to plug the heater in this way. I plan to grab one of those Marinco outlets eventually. Yes, I know my garage is messy.



Next up, the thermostat. My scan gauge always showed a 179-181 deg. F opening temp for my O.E. thermostat. Too low for my liking, so I picked up a 195f Stant replacement. Upon removing the OE unit I was surprised to see the following:



87 C = ~ 188 F. So either it was leaking a bit / prematurely opening, or my coolant temp sensor is reading a bit low. In either case, the new 195F Tstat gets my coolant temp up over 190F (per scan gauge). Should help bump up the oil temps also, since they attempt to equalize through the heat exchanger.

I'll report some FE data once my next tank is through. Fortunately I filled up right before starting this work.

After ~2 hours in my 44 degree garage, the coolant temp is up to 92. Meh, not bad I geuss. But I was hoping for a little more impact. Any EE's here? I bought a 240V unit and simply wired it for 120V. Its rated at 3.1 amps draw at 240 V, so I figured it would just draw over a little double that at 120, and produce the same amount of heat, right? Could there be any way that I'm only getting half my watts?

The timer is set for 5am tomorrow, so we'll see how hot she gets before the drive into work.

[bwilson4web]

Originally Posted by Deezler

. . .

After ~2 hours in my 44 degree garage, the coolant temp is up to 92. Meh, not bad I geuss. But I was hoping for a little more impact. Any EE's here? I bought a 240V unit and simply wired it for 120V. Its rated at 3.1 amps draw at 240 V, so I figured it would just draw over a little double that at 120, and produce the same amount of heat, right? Could there be any way that I'm only getting half my watts? . . .

Did you have two heating elements in series that you wired in parallel? If not, you would be getting about 1/4th the heat:

P = (V*V) / R

240 V / 3.1 A ~= 80 ohms

(120 * 120) / 80 ~= 180 W.
(240 * 240) / 80 ~= 720 W.

180 / 720 ~= 25%

As a suggestion, you might want to plot the temperature change over time. We found that after 1 hour, nearly 80-90% of all temperature rise has occurred. We're using an ~400 W block heater.

In my case, I plug in the heater before I get ready for work. By the time I get in the car 30-40 minutes later, it is as ready as it needs to be. The maximum temperature rise over a 4 hour interval is running about 35 C above ambient but one hour provides about +25 C increase.

It also helps to plot the temperature rise after starting the car. My experience is a block heater saves about 1 minute of engine warm-up out of 5-6 minutes in the moderate temperatures of North Alabama.

Bob Wilson

[tasdrouille]

Good job on the tstat and heater!

[Daox]

Agree, nice install deezler.

Also some good info from bwilson. I have found the same thing with my Matrix. I had it warming up for 2 hours (300W heater). During the coldtest part of winter I put the timer on for an extra hour. This rose coolant temps at start up from 70F to maybe 90F (around 0F ambient) on a good day. Is it worth the extra hour and 300 Wh of electricity? Thats up to you.

[bwilson4web]

Hi,

This is the warm-up data I was looking for, the upper blue line of symbols:

You'll notice there is brief temperature drop as the coolant in the cabin heater core floods back into the block. But 0C is about as cold as it gets in my area.

For those curious:

• MG1 C - temperature of motor generator 1 closest to engine side of transaxle
• MG2 C - temperature of motor generator 2, traction motor and regenerative braking generator at end of transaxle
• Air g/sec - the mass air flow sensor data, indicator of engine operation and power level
• ICE rpm - internal combusion engine rpm
• MG2 rpm - the traction motor generator rpm, which is proportional to vehicle speed

Bob Wilson

[Deezler]

Originally Posted by bwilson4web

Did you have two heating elements in series that you wired in parallel? If not, you would be getting about 1/4th the heat:

Two heating elements? The heater came ready to install, I didn't crack the case on it. I'm not sure it's reconfigurable but I'll have to look into it. Here's a schematic of the internals, not much detail.



Thanks for the info though. I do plan to experiment with the timer until I find the optimal heating duration. I only have one hour increments to adjust but I can shift the timer's current time for when I would be unplugging the heater to drive away.

This morning I had 82F in 42F ambient garage after ~2 hours. But the timer then went off and I was back down to 72 by the time I started the engine.
One counter-productive aspect of installing this heater is the additional quart of coolant needed just to fill it. doh.

The big surprise was on the highway when my temps just kept climbing; the thermostat doesn't open until 206F! Arg. A little higher than I was hoping for, but the fans still don't come on at this temp, so I guess it's ok. The oil temps were ~15F hotter as well, so that's good.

No FE benefit from this mornings scan gauge reading, but I'll try to be patient. The car definitely runs smoother at 206F vs. 180, but some of the power crispness is gone under load, too. Oh well.

[bwilson4web]

You may be in luck. The diagram suggests there are two heating elements that may be wired in series. If so and each element measures equal resistance, you could rewire them so they are in in parallel AFTER CHECKING THE CURRENT LIMIT OF THE TEMPERATURE CONTROL! I would recommend contacting the vendor or manufacturer of the unit and make sure this is OK by them. The obvious advantage is you'll have four times the heat for a quicker warm-up.

What I don't know is if you have enough space to work on the electronics without having to break the coolant loop. You know better how easy it is to access the electrical side. Still, this is a fairly standard way vendors handle mixed voltage electrical systems.

I would also suggest setting your timer for a longer duration than your usual 'leave time' and then use the "unplug it switch" before you leave. The unit will still come on in time but when you actually get in the car, you'll unplug it and say 1-2 hours later, the timer will shutoff and stay off until the next day. That way if you stay home (sick or sleep-in or gone on a trip,) you won't run up an excessive electrical bill. <grins>

My car is outside so I slip-on shoes and 'house clothes' and run out to plug it in. The dog joins me and gets to stay out for a few minutes. Invigorated by the 'fresh air,' I come back in and eat breakfast, get dressed for work and head out to the car to unplug it just before leaving for work. But I plan to rig up an automatic plug in the future.

Bob Wilson

[Deezler]

Very good suggestions Bob, thanks for your insight. Really wish I had properly analyzed the electrical situation before installing the heater; it's not coming out anytime soon. I can't get to the electrical side without removal. I'd be a little wary of doubling the power output of this thing, too. And I have quite a suspicion that the manufacturer would NOT endorse me modifying this thing in any way. They did not even respond to my email inquiry about the feasibility of running this 240V model on 120V.

One question though, why are you squaring the voltage? B/C of the AC current? Watts = volts * amps, but is that only for DC? I should really know this... too bad I sold my circuits book back to the bookstore. I'm not 100% sure that there are dual heating elements in this thing... could be one longer looped element.

I think I will live with the low power for this spring and think about it again next fall. If I am indeed down at 175 watts, well then I suppose I'll just feel better about running the heater for a couple more hours before startup.

[bwilson4web]

Hi,

The squaring of the voltage comes from a combination of Ohms law and the definition of power:

I = amps
V = volts
R = resistance

I = V / R (Ohms law)
P = V * I (Power)

If you only have volts and resistance, combine the Ohms law with power:

P = V * ( V / R)
= (V * V) / R

What this means is for the same resistance, the power increases as the square of the voltage. So if the resistance stays the same, doubling the voltage results in four times the power. Cutting the voltage in half gives only 25% of the original power.

Now there is another approach that solves your voltage problem quite nicely, a step up/down transformer. I see any number of 1kw to 1.5kw 110/220 step up / step down transformers on Ebay in the $40-70 range. This would be an 'off the shelf' solution.

Bob Wilson

[Deezler]

Ah ha, of course. Well I think that pretty much sums it up; I'm at 1/4 power. Oh well.

Another great suggestion on the step up/down transformer, thanks. I think a better solution might be to just drop a 14/3 line from my garage down to the circuit breaker panel and wire a dedicated 220 outlet. hmmm....