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MG TD TF 1500 - Water pump debate

I was talking to Dave Zyp about water pumps and the idea that adding more vanes to the water pump didn't really increase the flow. I later remembered that in a long ago (Newton was still teaching) physics class we were told the way to improve flow in an impeller pump was to increase the diameter of the impeller or the speed of the impeller. So I'm throwing this out for debate/discussion: Will decreasing the size of the TD water pump pulley increase the flow of coolant through the system? The floor is open.

Tim
TD12524
TW Burchfield

Nothing against esoteric discussions.. but the original pump on a properly tuned XPAG keeps the engine cool on 100 degree days in 1 1/2 hr. stop and go traffic on the interstate... now back to the esoteric physics discussion. Regards, Tom
tm peterson

Tom, glad it works for you but there seems to be a pretty good market for increased vane water pumps. Obviously not everyone has the success you've had with cooling issues. A search of the archives reveals almost 30 different discussions about cooling.

Tim
TW Burchfield

I was on a Brit Car run on Saturday. We drove a mountain pass between two sight-seeing points. We climbed about 2,000 feet in 15 minutes in 90*F heat. I never went past 92*C.

Unless you can markedly reduce friction with a redesign, more pumping = more work. I've got no desire to divert even 1 more of my meager supply of horses to the water pump.

......
MAndrus

MAndrus do you think installing a smaller pulley on the water pump would increase the horsepower load on the engine?

Tim
TW Burchfield

Under normal conditions; You have a thermostat. Its job is to keep the car temperature (relatively) fixed at some temperature. It does this by restricting the flow. If you increase the flow, the thermostat will react and restrict the flow.

If you can increase the flow, in spite of the thermostat, then the issue is the transfer of the engine heat to the air stream. That's a function of the temperature difference between the radiator and the outside air, surface area of the radiator and the airflow through the radiator.

Increasing the water flow, and overcoming the thermostat lowers the water temperature going into the radiator and that can decreases heat energy flow into the air stream.

Most often, as I understand it, MG's have temperature issues at low speed, such as stop and go traffic and parades and perhaps climbing hills.
I would suspect that at low speeds the water flow might be less than desirable. However there is also an issue due to the fan speed being low.

If low speed were the only operating condition then yes increasing vane speed could help.
In the old days (Post Newton) I would turn on the heater (Not an MG), take the car out of gear, and increase the RPM.

So if parades are the issue, yes a smaller pulley might help BUT that will decrease HP and should not be needed at higher RPM's.

There was a thread, not long ago, on converting to a 6 vane fan.

I did some research and the 6 vane configuration does increase water flow. Although it is unclear, to me, why it does.

I have not addressed the "going up a hill" temperature increase.

If I had that issue I would clean out the block and the radiator before I proceeded with anything else.

Jim B.
Jim B in NJ

Jim, I agree with your comments. However, a smaller pulley would increase flow at idle as well as at speed. The thermostat would only restrict flow when the coolant temperature dropped below the thermostats operating temp. So if your engine is overheating at idle and the thermostat is wide open a smaller pulley would increase flow and perhaps reduce overheating (and cause the thermostat to close. The issue I discussed with Dave Zyp was that increasing vanes in the pump also reduced the amount of water in the cavity as well (a six vane impeller has more volume than a four vane).

As to your comment, "Increasing the water flow, and overcoming the thermostat lowers the water temperature going into the radiator and that can decreases heat energy flow into the air stream." Isn't a lower water temperature entering the radiator the goal? The lower water temperature going into the radiator means the water from the engine is a lower temperature.

Tim
TW Burchfield


"Isn't a lower water temperature entering the radiator the goal? The lower water temperature going into the radiator means the water from the engine is a lower temperature."

I believe the goal is to get heat out of the engine. If the water temperature is not high enough you cant get the heat out.

In regulating the temperature, the thermostat is trying to maintain this transfer of energy.
The temperature, however does also effect engine performance.

Yes a smaller pulley could help idle temperature. But nothing is free.
If you move more water you must use more energy. Work over time is energy. Work is force times distance. Times time is energy.
(The force it the force needed to move water through the block.)
If you have more water at low speed you have even more at higher speed (unless the pump cavitates.)
Thus you use more HP at all speeds.

There is a balance between over design and just enough.
We can put in more cores, we can (perhaps) move more water, but we use more HP. Even more cores winds up using more HP since the thicker radiator and additional water adds weigh. Moving weight take HP.
Perhaps not once you get to speed since air drag takes over, but getting there will take longer.

I would want a clean block, a clean radiator, and perhaps a 6 vane pump.

If I look at the design equations for a vane pump. The contain the inlet area, the out let area and the diameter. I cant find any that seem to treat the number of vanes.
There must be something in the 6 vane pump that makes it more efficient.

Jim B in NJ

TW...

In theory, you could fix a pump requiring so much power (or gear a factory unit to pump so much water) that 47 HP won't run it past a slow crawl, right? So yea, it takes add'l HP to pump more water just like it takes more HP to move a heavier car.

Easily tested. Hook up an electric motor to a pump via a gear set (to totally eliminate slippage) and pump a set amount over a set interval. Measure the amps.

Change the gear ratio and do it again. If you pumped the same water faster, you needed more amps to do it.

Don't forget to factor in slippage. The harder you need to pull on the pulley, the more energy you will lose during the transfer from pulley to belt to pulley.

We always have to pay for the work accomplished in some way. No free lunch.

.......
MAndrus

MAndrus agreed. However, I wonder if the miniscule amount of HP lost to a smaller pulley would be outweighed by having a cooler (non-overheating) engine. After all, people put non stock, multi bladed fans on their cars which take more HP to move more air. Given the loss of a very small amount of HP vs overheating I'll go with the HP loss. Note: I'm only talking about cars with an overheating problem. If I had no overheating problems then of course I wouldn't change a thing.
TW Burchfield

Let's see -- I was having problems that put my temperature gauge needle up in the oil pressure range when doing the Town's 4th of July parade. Plus high readings when motoring along at 4500 rpm. A year or so ago I had Butch Taras rebuild my water pump and included a 6-blade turbine. I also installed an MGB fan. I no longer have ANY water temperature issues, neither high speed nor low. Bud
Bud Krueger

Bud, no doubt those fixes would work for the majority of overheating problems. My point of discussion is if a smaller water pump pulley would also alleviate overheating problems. I'm not suggesting there aren't equal or better ways to fix an overheating problem.

Tim
TW Burchfield

Tim, I'm not about to get into your 'esoteric discussion', but remember that there's a camp whose thought is 180 out. They think the coolant's going through the radiator too fast already, so the heat's not being extracted. Bud
Bud Krueger

Too late Bud you are already involved (unless someone hacked your account and posted above). :-) Any possibility you could direct me to that discussion about coolant going through a radiator too fast?

Tim
TW Burchfield

Jim B

You said, "I believe the goal is to get heat out of the engine. If the water temperature is not high enough you cant get the heat out." But the heat in the water comes from the engine. If the water isn't getting hot then the engine isn't hot. The thermostat regulates how much water circulates through the radiator. If , as you say, the water isn't hot enough, the thermostat will slow down or stop the coolant flow to the radiator. So with a 180 degree thermostat the coolant won't flow to the radiator until the it reaches that temp no matter how many vanes, what fan or what size pulley. I think we are really talking about temperatures above the thermostat rating.

Tim
TW Burchfield

Tim, not sure if my archive-hunting can find some of that, but I'll give it a try. Bud
Bud Krueger

Thanks Bud. I was just wondering what the reasoning would be and if there is any evidence behind the idea that coolant is going through the radiator too fast. I'll check the archives as well. I didn't realize it was a discussion that took place here.

BTW if you are wondering why I'm posting this "Thought Problem" post it's that I am stalled on my TD waiting for the head to be finished. I've even went so far as to construct a windshield wiper motor out of 4 spares and I already have two that work. In other words, I'm bored. :-)

Tim
TW Burchfield

Hi Tim. The over heating was a problem when you took out the thermostats out of a flat head Ford. You had to put flow restrictors in place of the thermostats. Check out the flat head Ford group.
One of the other problems I've seen numerous times is people close up the slats in the grill too much.


Butch
R Taras

Butch. I'm actually old enough to have owned flat heads before they made a comeback. You're right, not enough heat is bad (not as bad as too much heat) for an engine and performance. I'll remember the slat comment when I get my car running. Thanks.

Tim
TW Burchfield

I would really focus your attention on the radiator. I have a dimpled core 4 row on my TF. Recently I switched tstats to one with a bleed hole to help with getting air out of the system on a refill. The hole is only about 1/16 dia and has a small brass tickler plug in it to boot. With this small opening, my car no longer gets to opperating temps unless it is over 75 out. Period. The water pump is not the issue... Remember, this block came from a thermosiphon design with no water pump. If you are having cooling issues at low speeds, recore your radiator and put in a pusher fan with an electronic tstat behind the grill shell so you can't see it and you should be good to go.

Alex
Alex Waugh

Can't find it, Tim. It wasn't the topic, just an idea put forth by a member, and supported by some others. The idea was that the heated coolant was going through the radiator too fast to optimally transfer heat to the fins/airstream. The same argument was being used about getting heat from the heater. Bud
Bud Krueger

Bud, thanks for taking the time to look. I didn't find anything either. I'm not sure how the coolant could go through the radiator too fast when the thermostat would prevent that. If the coolant didn't lose enough heat in the radiator then the engine would heat up and the thermostat would close. I believe this "too fast flow" would only apply if there was no thermostat present. A way to test that theory would be to put a slightly larger pulley on the water pump to slow down the flow. But if I'm missing something here I'd appreciate someone who subscribes to the "too fast coolant flow" theory would enlighten me. I've been wrong before (just ask my wife).

Tim
TW Burchfield

You can drive a pump too fast as well and get cavitation. Depending on impeller design. Obviously if you are having overheating problems, and if a properly setup stock system will keep heat in check even in 100 degree temps, then one should find the root cause of the problem instead of mask it by trying to overcome the problem with more flow etc.
L Rutt

An observation. I had no thermostat, had standard 4 vane pump, original fan and radiator. On a 95 deg day here in VA water temp was near 100 degrees C on the gauge at 50 mph.
Changed to a 6 vein from Moss a month ago and now I'm at 85 degrees C on a 90 plus degree day. That's a lot. Now I need a thermostat.
Peter Dahlquist

L Rutt, I wish I was having cooling problems. That would mean that my car was on the road and running. I started this thread just to discuss the idea that increasing the flow of coolant through the water pump might help an overheating problem. I am not saying a clean block, good thermostat and efficient radiator are lesser solutions.

Tim
TW Burchfield

Here's an interesting article on this issue.
http://go.jeep-xj.info/HowtoWaterpump.htm

Regards
Declan
D Burns

D,

I find most of the assertions in that poorly written article either hogwash or severely begging for hard data sources in the footnotes.

...
MAndrus

This guy dyno tested a V8's water pump and found it needed 8hp.

http://www.youtube.com/watch?v=qizv46ZVMt0

I'll assume our puny little pumps require a bit less.... I hope.
MAndrus

TW, in another thread, I conducted a flow test on three TD water pump vane varieties (4 vane, 6 vane and improved design 6 vane). Results clearly show that the flow increases - check the archives for the data.
For anyone with heat issues a six vane pump is a valuable and relatively inexpensive modification with definite advantages.
I would only add that my experience is that if you are having heat problems, you need to fix the underlying problems first. They could stem from blocked water passages in your engine block (which was my problem!) or a radiator in need of "rodding" or replacing. If you don't fix the big problems, a water pump may not help you much.
I rebuilt my engine, cleaning out all passages and performing the drilling mod mentioned in other threads; disassembled and cleaned and "rodded" my radiator. The result should be a car running at or near original specs, I hope. But I'm also including a rebuilt modern water pump with an improved 6 vane impeller design, and I will report on how well it all works when it's back on the road.
I'm NOT a believer in the argument that any improvement moves water TOO fast through the engine. While that is theoretically possible (racing engines, tuned to the max, may encounter such problems) .... with our engine and pump setup, we are a long, long way from having such issues, and any reasonable improvements (6-vane water pumps, electric fans, 6 blade fans, etch etc) should all show improved cooling, and that's a good thing.
Geoffrey M Baker

Here's the link to the flow data thread:

http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=8&subjectar=8&thread=2015052220351326535
Geoffrey M Baker

The only time I have had flow problems was when I fitted a rebuilt water pump (not by me).I had immediate cooling problems in traffic.
I checked the rebuilt pump and found a new shaft had been fitted, the taper pin hole was in the wrong position giving too much clearance between the impellor and body. I turned the impellor 90degs moved it in re-drilled and taper reamed the hole and fitted the pin.
Problem solved.

I know we don't get the high temperatures you get in the US and Aus but never get too high engine temps and can see the stat open and close via the temp gauge.
Ray TF 2884
Ray Lee

Alex Waugh,

Could you please advise more details on the thermostat with the air bleed hole. Sounds like something easy to install but with good results.

I haven't run a fan on my TF since my 2006 rebuild. An electric (puller)fan wired to a temperature sensor at the bottom of the rad solved my heating problems, including running to the MG International in Gatlinburg TN in 2006 when the ambient air was in the 35° to 40°C range (I think that's around the 95°f range) and stinking humidity. Car ran like a train including a charge up the "Tail of the Dragon", never overheated, and I've never been one to hold back on the revs!

Gord Clark
Rockburn, Qué.
Gord Clark

This thread was discussed between 03/08/2015 and 07/08/2015

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