TR2/3/3A TR3 Water Pump Question

[jsneddon]

On the Triumph mailing list someone mentioned that Ken Gillanders of British Frame and Engine has a water pump with hooked impellers designed to flow more water through the system for $140.

https://www.britishframeandengine.com/parts1.html

My question is this.

It appears to be the common consensus that removing the thermostat allows the water to flow too quickly through the radiator and doesn't give it the chance to cool down efficiently.

So if you put a water pump that increases flow aren't you doing the same thing?

Is this 6 blade impeller something you'd only want in a high RPM racing engine since at some point you are wanting to defeat cavitation from the wimpy orignial design?

 

[Dave Russell]

[ QUOTE ]

My question is this.

It appears to be the common consensus that removing the thermostat allows the water to flow too quickly through the radiator and doesn't give it the chance to cool down efficiently.

So if you put a water pump that increases flow aren't you doing the same thing?



[/ QUOTE ]
The "common concensus" is partially correct, but for the wrong reason. The "restriction" actually reduces the negative pressure (suction) on the intake side of the water pump by creating more head pressure on the pump. This negative pressure if too high, is what causes cavitation & loss of pumping capability.
and
Also the restrictor causes higher local pressures in the engine water jackets which reduces the tendency for localized boiling in hot spots. Internal local water pressures behind the thermostat/restrictor are much higher than the pressure cap rating which only sees the pressures after the restrictor.

It has nothing to do with "heat transfer time" in the radiator. Water cannot move too fast through the radiator to lose heat. True that the water loses less heat if it is moving faster, but the reduced heat loss is offset by moving more water through the radiator. In theory, 10 gpm through the radiator that loses 10 degrees of heat is about the same cooling as 20 gpm that loses 5 degrees. ACTUALLY, tests have shown that faster water flow through the radiator increases the heat transfer rate due to increased turbulance creating more water contact with the radiator tubes. Laminar flow through the radiator as opposed to turbulent flow, results in less water contact with the cooling tube surfaces.

So a pump that is designed to move more water without cavitating "may" increase cooling by creating higher localized pressures in the water jackets which reduces hot spot localized boiling & by creating more radiator flow turbulence. Localized boiling is generally around combustion chambers & exhaust ports. It all depends on radiator core design, water pump design, correct restriction, & intended engine usage.

In general, you would not gain much from a high flow pump unless everything else was properly matched AND, you actually needed it.
D

 

[martx-5]

That does seem to be at odds with one another, but the fact is, that the water pump also flows the coolant around the block and heads besides pumping it through the radiator. I think removing the thermostat has more of an effect on the amount of coolant that flows through the by-pass hose, resulting in less coolant getting to the radiator. The original design on the TRactor engines has a thermostat that closes off the by-pass when it opens to the radiator. I think the problems encountered when removing the thermostat have to do with aftermarket types that don't have the by-pass close off. In response to this, many guys have installed restrictors in the hose to alleviate this problem. Since British Frame and Engine sells alot of go-fast stuff, the additional flow water pump was probably designed to work with a radiator of larger capacity and other cooling system mods. If the correct thermostat is in the engine, I don't think the high volume pump should have an effect. I just never bought into the "the coolant is going too fast through the radiator" theory. If someone else has some real facts on this theory, I'd like to hear it, as I'm ready to re-do my TR3 engine and would like to know the best course of action.

 

[jsneddon]

hey martx - you and Dave must have crossed posts.

Dave's explaination makes much more sense. Keeping the pressure high before the pump from the restriction of the thermostat is the best explaination I've heard for this yet.

Thanks Dave!

 

[martx-5]

Yeah, I was typing while Dave was posting. He obviously has a strong engineering background.

I've heard this rumor, myth, or whatever you want to call it about the coolant flowing through the radiator too fast, and could never quite buy it. His explanation makes alot of sense.

Hey, Dave chime in on your thoughts concerning the original by-pass type thermostat and the aftermarket type that doesn't have that feature.

 

[Dave Russell]

The original type thermostat was designed to let "some" coolant flow circulate through the engine while the thermostat is closed. A very good idea to prevent localized hot spots as the engine warms up. Also gets the heater working sooner if this is a consideration. Then, when the thermostat is open, the bypass is closed, which allows full coolant circulation through the radiator.

Installing a thermostat without this feature, will allow "some" coolant to recirculate through the engine without going through the radiator when the thermostat is open. This will reduce cooling effeciency to some extent.

Leaving the thermostat out altogether will allow some coolant to bypass the radiator & also eliminate the needed restriction at this point, as explained earlier. Not a good solution at all.

I believe that there are sleeves available that take the place of the thermostat. They block off the bypass & also provide some necessary restriction to water flow. The down side is very slow warm up.

I personally would not use a non-sleeved thermostat even if it is a lot cheaper, & wouldn't use a sleeve in place of the thermostat unless the car was used for all out racing.
D

 

[Simon TR4a]

I had not planned to ask this question since I don't have a cooling problem, but I do like to understand how and why things work.
I also was skeptical because although the water might spend less time in the rad it would presumably be there more often!

Thanks for a very comprehensive explanation.
Simon.

 

[Mickey Richaud]

I noticed that in Moss' newest catalog they offer a skirted/sleeved thermostat now. I had ordered one from them a while back, and the "skirt" wasn't much of one at all. The new one looks much more effective. Comments?

Mickey

 

[Dave Russell]

Hi Mickey,
I guess you would have to measure the sleeve location from the mounting flange with the thermostat hot & cold, pan of water on the stove. Then compare it to the bypass opening location in the engine to see if the sleeve uncovers the opening when cold & blocks it when hot. Removing the thermostat & doing some careful measuring would answer your question. OR, maybe someone has already done this.
D

 

[Mickey Richaud]

Yeah, but I was hoping someone might know already. The stat that I got has a sleeve, but it's much shorter than the new one pictured in the catalog. When I got it, I didn't think it would make much of a difference, and I'm still running pretty hot.

I've got a recored radiator, and I really suspect it wasn't done properly. Everything else seems to check out (except for the thermostat). Even the aux. electric fan doesn't help much. /ubbthreads/images/graemlins/frown.gif

Mickey

 

[ron wilson]

Has someone actually received one of the new Moss sleeved thermostats ? (If so have you noticed any improvement) I have has one backordered for 2 months.

 

[donbmw]

I have installed a sleeve type a long time ago I realy have not seen where it help. I did install a aux fan that has been the biggest help when running around town and when I did a couple parades one that was stop and go for more than 1 hour.

 

[ron wilson]

I also have an aux fan which helps a lot. Also tried some water weter last summer and it also seemed to help some.
Just trying the sleeved thermostat to see if it is the final touch. I do fine if the day is not too warm say below 85 but still get nervous if the days is warmer than that.