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Water temp puzzle.....
MydT9 - 20/1/11 at 07:32 PM

Here goes, I have a Hayabusa enginea in a kit car and after a rolling road session this week I have the following situation:

Water Temp takes a long (i mean a long time) to get up to around 75c and then continues to about 92-94, if I switch on my electric Fans it takes a very very very long time to start dropping .

a) Rad is brand new standard MGF 1800i with twin push fans which are located at front of car;
b) It runs a Davies Craig high capacity electric water pump - located about 20" from Rad and is lower than the Rad; It has to push the water some 1.2m to the engine at the rear;
c) Water is flowing through engine as per standard Hayabusa configuration;
d) Temp sender is located in engine bay but shielded from any other heat sources;
e) Eng water outlet goes into a Swirl pot then to rad at front;
f) I have removed the thermostat from the engine as well as the original mechanical water pump;

So the question is why so long to warm up and why so long to react to forced air for cooling?

A possible reason for the weird Temp control is that the Water pump is pumping water too fast and hence taking time to heat up and hence too fast through rad to be cooled effectively.... what do you think?

Thanks,

Myd

r1_pete - 20/1/11 at 07:40 PM

Because you have removed the thermostat, there is now nothing to regulate the engine temperature.

matt_gsxr - 20/1/11 at 07:43 PM

are you using the Davies Craig variable flow controller?

stevebubs - 20/1/11 at 07:45 PM

Are these stationary tests? What is the ambient temperature around you? This affects what you will see.

However, my 2p based on the above...

Long time to warm up because of the removed thermostat

Long time to react to forced cooling? I would have thought it would run better at just over 90 degrees....

[Edited on 20/1/11 by stevebubs]

MydT9 - 20/1/11 at 08:05 PM

Hi,

I don't run a variable flow controller; and yes I probably should.

Ambient temp was around 8 degrees last Monday, rolling road tuner said that I should be looking at a stable 86-88ish based on his experience with similar set-ups so 90 sounds consistent with what he was looking for.

This was a stationery test on a rolling road so I would hope that when the car is moving it would achieve cooler air through the rad and through the engine bay.

Ok, thats great, thanks to you all for responding,

Myd

britishtrident - 20/1/11 at 08:26 PM

Some of the problems you are having are due to what are called distance velocity lags your rad and fan are a long way from the engine so it will take along while for cooled water from the rad to reach the engine.

The engine temperature should primarily be controlled by the thermostat , although it is and ugly looking thing the Landrover TD5 PRRT (sometimes called a PRT) external thermostat is ideal for this and should be installed in the bottom hose before the water pump,the by-pass connection on the thermostat is simply connected to Tee fitting in the top hose.


The job of the electric cooling fans are to switch in to keep the radiator water cool is enough to cool the engine not to directly control engine temperature. I would control each of the fans separately using different temperature switches to give cascade control of the fans.


I don't know if this applies to your car but on the old Imp engined Davrians the flow and return pipes from the rad used to run very close together where they through the tunnel -- do you best to insulate the return pipe from picking heat from the hot pipe.

MydT9 - 20/1/11 at 08:47 PM

That was some interesting info to note, fans are independantly switched although via a manual switch, it goes without saying that a thermostat needs to be added for control.

As for the twin ali pipe returns, they do run in a tunnel underneath the tub (like the Davrian) at a proximity of some 300mm apart so there could be mileage in shrouding the return one as you suggested, thank you

RazMan - 20/1/11 at 10:08 PM

quote:
Originally posted by MydT9
I don't run a variable flow controller; and yes I probably should.


You have just named your own solution

I run a Davies Craig pump WITH their controller, and the combination works extremely well IMO. If your pump is going full speed all of the time its no wonder the temps are slow to rise. The variable controller initially sends 'slugs' of water round the system, heating up, pumping cold in, stopping, heating up etc. That is not ideal in winter conditions (as I found) and a thermostat, although not recommended by Davies Craig, is the only way to bring the engine up to temp quickly IMO.

In my system (a Ford V6 middy) I have the rad quite a long way from the engine and the cooling is too efficient unless I recirculate some of the heated water with a thermostat. The Davies Craig pump does however need a small amount of flow to function properly or you stand a risk of overheating before the thermostat kicks in For that reason I installed a 3mm bleed hose which feeds directly back into the header tank. As a result, warm up times are quicker and my heater works more efficiently.

I would try something similar - CBS stock a suitable thermostat and it really works.

Oh and the fans should only really be required when idling for long periods and should only kick in when the rad cannot do its job. My single fan kicks in at around 98 degrees and my normal running temp is usually around 85-90 ish in the summer and about 10 degrees lower in the really cold weather.

*edit* You say that your temp sender is 'in the engine bay' Is it not close enough to the outlet from the engine? Just a thought.


[Edited on 20-1-11 by RazMan]

Dusty - 20/1/11 at 11:32 PM

Have you wired the fans for the correct rotation, ie to blow if in front of the rad or suck if behind?

And have you mounted them the right way round? They are often designed for efficiency in one direction only.

MikeRJ - 21/1/11 at 09:17 AM

quote:
Originally posted by MydT9

f) I have removed the thermostat from the engine as well as the original mechanical water pump;

So the question is why so long to warm up and why so long to react to forced air for cooling?


You put the answer before the question. Without a thermostat (or variable speed pump), how do you think the temperature could ever be regulated?

Thy not use the original pump anyway? Have a look at this link to see what a professional cooling system designer thinks of "Craig David" pumps...

[Edited on 21/1/11 by MikeRJ]

Uphill Racer - 28/1/11 at 11:30 PM

quote:
Originally posted by MikeRJ
quote:
Originally posted by MydT9

f) I have removed the thermostat from the engine as well as the original mechanical water pump;

So the question is why so long to warm up and why so long to react to forced air for cooling?


You put the answer before the question. Without a thermostat (or variable speed pump), how do you think the temperature could ever be regulated?

Thy not use the original pump anyway? Have a look at this link to see what a professional cooling system designer thinks of "Craig David" pumps...

[Edited on 21/1/11 by MikeRJ]


Also if you remove the stat from outlet of the head you need to fit a restrictor to keep the head pressure up.
Correctly sized this will raise the boiling point of the coolant in the head by producing a pressure behind the restrictor of 25 to 30 psi.
Removing the stat leaves the head Susceptible to localised boiling and possible failure due to the reduced boiling point of the coolant.