IR thermometer results

[joe_db]

After 30 minutes at a fairly high power setting I got these results:
Hot end of manifold (front of engine): 568 F
Bottom of heat exchanger: 89 F
Top freshwater part of heat exchanger: 146 F
Coolant at cylinder head T fitting with heat and alarm sensor at the end closet to the engine: 166 F
Oil filter body: 136 F
Water Temp: 53 F
Temp Gauge reading - about 135 or so

With 50 degree water I am getting a delta of 57 degrees in the heat exchanger.

[hanleyclifford]

Thanks for bringing this subject up. I have often wondered what temp differential existed between antifreeze leaving the block and temp exiting the pump and headed for the side plate. That differential defines exchanger efficiency together with other variable like volume and velocity, all of which vary with rpm.

[joe_db]

Here is the wrap. It is a good enough insulator that despite the 568 degree reading, you can hold on to it (briefly). The hot spot on the manifold, not so much
Here is an engineering riddle for you: The longer the coolant is in the block, the hotter it gets. The longer it is in the heat exchanger, the colder it gets. So.....fresh water side pumping capacity may not have an obvious flow vs. temp relationship. Not so the raw water side, the more flow the colder the raw side will be and thus take more heat out of the system.

[hanleyclifford]

Originally Posted by joe_db

Here is the wrap. It is a good enough insulator that despite the 568 degree reading, you can hold on to it (briefly). The hot spot on the manifold, not so much
Here is an engineering riddle for you: The longer the coolant is in the block, the hotter it gets. The longer it is in the heat exchanger, the colder it gets. So.....fresh water side pumping capacity may not have an obvious flow vs. temp relationship. Not so the raw water side, the more flow the colder the raw side will be and thus take more heat out of the system.

Ed (engineer on site) had the definitive post on this a couple years back but danged if I can find it. I'll look for it.

[Ajax]

Aren't you running cooler than you'd like, for FWC?
I guess it would go up if the water temp were in the 80's, as in the summer.

[romantic comedy]

Joe, I dont see a riddle here. More flow is faster flow and thus less temperature difference. Same for the hot side or the cold side.

[joe_db]

The thermostat is original, so I assume it is a 140 degree unit. I am going to wait for summer to see if I need to change something.

Originally Posted by Ajax

Aren't you running cooler than you'd like, for FWC?
I guess it would go up if the water temp were in the 80's, as in the summer.

[joe_db]

I am not sure about that.
On the raw water side, no flow at all would provide no cooling and infinite flow would provide the theoretical maximum, i.e. the tubes would be at the raw water temperature.
On the fresh side, if you double the time it takes for the water to make a round trip it spends twice as long getting hot and twice as long getting cold too. Obviously too slow and you have a trickle of cold water going in one end and boiling over at the other end.
EDIT - never mind, I just read the other thread. The BTU formula shows total BTUs moved increases with flow.

Originally Posted by romantic comedy

Joe, I dont see a riddle here. More flow is faster flow and thus less temperature difference. Same for the hot side or the cold side.

ut

[romantic comedy]

I think I know the issue. Did not understand at first.

Something to consider is that the rate of heat transfer is higher with a greater temperature difference. A higher flow rate would show this.

[joe_db]

I may get some cheap Fleabay digital thermometers and hook them up the heat exchanger at the hot end, the cold end, and the raw water section. I will be very curious to see how it does as the water gets warmer next year. I am also tempted to move my temp sender to the output side of the manifold instead of where it is now or add a second sender there.

[hanleyclifford]

Originally Posted by joe_db

I may get some cheap Fleabay digital thermometers and hook them up the heat exchanger at the hot end, the cold end, and the raw water section. I will be very curious to see how it does as the water gets warmer next year. I am also tempted to move my temp sender to the output side of the manifold instead of where it is now or add a second sender there.

I did move my sender to the manifold forward plug hole which I tapped for 3/4" NPT because I believe this to be the hottest (accessible) location on the engine. But I do like your idea of multiple location monitoring.

[hanleyclifford]

Like this:

[Ajax]

Jesus, that thing is pornographic. Liberace's engine?

[hanleyclifford]

Originally Posted by Ajax

Jesus, that thing is pornographic. Liberace's engine?

Let's just say, it's prettier than me.

[edwardc]

Originally Posted by hanleyclifford

Ed (engineer on site) had the definitive post on this a couple years back but danged if I can find it. I'll look for it.

Here it is:
http://www.moyermarine.com/forums/sh...0&postcount=21

[hanleyclifford]

Thanks Ed - I bumped the whole thread but I'm putting that post into favorites since the subject comes up so often and is so important.

[joe_db]

OK - yesterday was the first test out of the slip and results were mixed
We were heard to Rock Hall and my wife was in hurry to make it to a craft show for Christmas shopping and called for maximum speed. There was no wind, so maximum speed was 2500 RPM and 2 inches manifold. The engine temperature rose past 180 to about 200 in the space of about 45 minute or so. The hot part of the HX was around 165 to 170 with discharge water back to the engine at 90 and raw water at 53 in and 70 out. The engine, depending on where you hit it with the IR, was around 200-210. I tried the old vice-grip on the bypass hose trick to no apparent effect. We backed off to 5" and the temperature on the gauge steadied around 185-190 or so. When we got into town and backed off the engine to dock, the temperature fell rapidly at idle power.
This concerns me for a couple of reasons and one of the main one is raw water will eventually be 85, not 55. I know modern engines run routinely over 200, but I just can't make my brain like the A4 being this hot.
My ideas so far:
1. Remove the thermostat for better flow and use the valve in the bypass if it ends up too cold. I have never even looked at my thermostat - who knows what shape it is in?
2. Add a second electric pump for more coolant flow. I was going to anyone for a standby, but I could run both at once. The future addition of a hot water heater and cabin heater argue for more pumping capacity anyway at some point.
3. Go to a mechanical pump. From watching the coolant move in the heat exchanger, the electric pump does not seem to pump it very fast at all.
3a. Maybe the pump is not that good. It is used, maybe it is below par. Check that too.

Besides for ending up at reduced power, which only cost us .3 knots in the end (5 inches = 6 knots, 2 inches = 6.3), it did all work. I suspect many A4s with 2 blade props are unable to run at the power level I do and would never see this issue.

[hanleyclifford]

Do #1 first and try again.