Richard Murray's Coolant reroute

 * From: "Murray, Richard" <>
    * To: "Maillist Miatapower (E-mail)" <>
    * Subject: Coolant ReRouting Kit vs Stock Configuration Back-to-Back Test Results (Long)
    * Date: Tue, 27 Aug 2002 16:17:14 -0400
    * Return-Receipt-To: "Murray, Richard" <>

I took a week of vacation last week and, in addition to all my other chores, managed to do a back-to-back comparison of my Coolant ReRouting kit vs. the stock configuration. Here is a description of the test equipment, process, and results.
The test equipment consisted of:
'00 1.8L engine with a FM 1.6L ECU.
1.6L thermostat housing and cover with a new stock '00 thermostat mounted at the front of the head.
ReRouting kit with a 1.8L thermostat from the original '00 engine. The stock 1.8L thermostat has a nice wide opening, but the plunger is a rubber coated 1/4in cylinder with a ridge at the base and a bulge that makes opening "sticky".
Manual switching 1inch NPT valve mounted between radiator inlet, stock thermostat housing outlet, and ReRouting kit outlet to the radiator. The ReRouting kit flow was forced to go through two right angles while the stock configuration flow was straight through. Pictures are available from my home email address ( <> ).
Dual Westberg/FM temperature gauge connected to two 4-postion switches.
Six liquid temperature sensors, connected to the switches, located on the engine in the following positions:
1. Back of head
2. Oil pan
3. Top of 1.6L thermostat housing in the normal radiator fan
thermo-switch position
4. Coolant pump inlet fitting (I will refer to it as the mixing bowl),
in the flow from the radiator outlet
5. Mixing bowl, in the flow from the heater outlet
6. Turbo coolant outlet tube

Two indoor/outdoor temperature gauges measuring the passenger compartment temperature, the air inlet to the radiator, and the air inlet to the engine.

Low pressure (9-10PSI) radiator cap on stock radiator. Stock heater coolant routing. For consistency, the existing coolant routing to the turbo was used, the two thermostat housing nipples were blocked, and the fan thermo-switch was mounted in the turbo coolant return line. I have discovered this is the best place for it anyway. The low pressure radiator cap was used because the radiator hose fittings on the switching valve were too short (no room) and I did not trust them to hold at normal pressures.  One of the fittings did leak and was fixed with safety wire placed under the band clamp.

I had concerns about sensor #3 during the reroute test, because its mount high up on the thermostat mount would be in a dead flow area and I wanted to measure the temperature at the front of the head. Subsequent measurements proved that my concerns were groundless, there was negligible difference between that mount and its current position in the hole at the front of the head.

The test process and conditions:
I only had one day to perform the tests and restore the car to normal.

The ambient temperature was 81-83F into the radiator, 87-89F in the passenger compartment, and 110F at the engine inlet during cruise. These conditions are not a strain on either configuration. The heater was off for the tests. Subsequent measuring was done on the heater effect.

The first test trip was on city streets to the auto parts store and back to check for leaks. The route there and back was on streets with 45-50MPH limits and traffic lights about every 1/2mile.

The second test was a longer trip of about 60 miles primarily on expressways. The expressway test was basically over two different sections, one where I was held to between 65MPH and 80MPH by traffic and a second section of about 10 miles where I was held to between 80MPH and 90+MPH by prudence. I then stopped at an exit, switched the valve and drove home. The trip was split in two, the first half was with the stock configuration and the second return half using the reroute kit, over the same roads in reverse order. I should have switched the testing order, because the minimal coolant flow through the 1.6L housing during warm-up slowed the front thermostat a bit during the stock test and the stagnant coolant in the bypass tube from the stock test boiled and formed a steam bubble. That bubble caused a short
temperature spike at the very beginning of the reroute test, until the steam was pushed out to the radiator.

The results:
City traffic:
Stock configuration: #1- 200F, #3 - 180 to 190F
Reroute configuration #1 - 195F to 205F(speed dependent), #3 - 200F

<80MPH section:
Stock configuration: #1- 200F, #3 - 180F, #4 - 160F steady, #5 - 190F steady (10F delta to #1, however I suspect that 5F is conduction from #4 on the common housing)
Reroute configuration #1 - 200F to 205F(speed dependent), #3 - 200F, #4 - 180 to 195(cycling at steady speed) as low as 125F when slowing down, #5 - 195 to 200F (5F delta to #1)

80+MPH section:
Stock configuration: #1- 210F, #3 - 190F
Reroute configuration #1 - 210F to 220F(one time spike), #3 - 205F

Subsequent measurements in daily driving with only the rerouted
Heater on; the delta temperature between #1 and #5 was 15F to 40F (air flow speed dependent).
Heater off; the delta temperature between #1 and #5 was 5F.
Turbo cooling, delta between #1 and #6 was 10F at cruise. From previous measurements I know that 5F of this is from the oil cooler and 5F from the turbo.
The temperature delta between #1 and #4 (radiator outlet) cycles between a needle's width (high flow) and 40+F (low flow).
The temperature delta between #1 and #3 only varies between a needle's width and 5F.

My conclusions:
The ReRouting kit achieves its goals of using the radiator more efficiently, and flattening out the cylinder to cylinder temperature. The kit sends coolant to the radiator consistently 20F higher than the stock configuration while maintaining the same thermostat controlled temperature at the back of the head. The kit minimizes the temperature difference between #1 cylinder and #4 cylinder from 20F in the standard configuration to a 5F maximum. And that 20F is a mixture delta, the actual delta is even higher.

A wide opening low temperature thermostat could lower the overall engine temperature under normal conditions and take advantage of higher capacity radiators under adverse conditions. So last Sunday I took a stock 1.8L thermostat with a wide opening, installed a 160F cartridge, and shaved some of the rubber off. During the next couple of rainy days we get, I will install it.

The mixing bowl seems to be the secret to flattening out the temperature at the front of the engine. I know from my experience two years ago that a heater bypass to the radiator will help overall cooling in the stock configuration, but I do not know its effect in the rerouted configuration.

When the thermostat is open and flow is high, there is about a 5F drop across the heater core and a 5F drop across the radiator.