Running Very Cool

[Longboarder]

Heat dissipated by radiator = Heat created by engine

reduce the left hand side of the equation by blocking off part of the radiator

 

The first statement is the aim but is incomplete. The cooling system you build should be designed to dissipate more heat than your engine can produce. ie it should be capable of overcooling. So that's right for starters. Engine, pump and rad must be fine.

Remote thermostat housing was a problem in the K and on your diagram the red line is vital for establishing warm up circulation. It should leave engine side of the stat, supply the heater and then return to the pump feed, not the top of the rad. While the stat is closed this line has full pumping force going through it. That force can't go anywhere else. So with the stat closed it will be feeding the top of the rad and the expansion bottle. I doubt all the flow can be going to the rad so some must go through the expansion bottle and out in reverse flow through the green (to the stat housing and thence through the black to the top of the rad) and through the blue to the top of the rad.

So I think that explains the early gentle warming in the stat to rad black hose which should stay cold till the stat opens and then suddenly become hot.

So you have additional flow through blue, red and green hoses to the top of the radiator, through it and back to the pump. This is uncontrolled by the stat which can hardly be opening at mid 70's and I suspect this is enough to give you the overcooling. Basically the stat can't do its job.

So first redesign of the cooling system is pic one but it's not complete. The red line should be moved to the pump inlet hose and be at least 15mm bore. But system is not self bleeding of air.

To bleed air back to the expansion bottle you need to reinstate the blue line to the rad top. To act as a bleed, flow in blue once the stat is open has to be rad to bottle so pressure in the bottle must be low. If all the red line is 15mm and the blue is 5mm or so then this should be the case with the stat open.(pump sucking on bottom of rad and no longer pressurising the red line as much of the flow goes through the stat.)

The green line seems to be redundant.

Test your system as it currently stands by clamping the green closed, nipping the blue to nearly closed and start from cold. OK in that state you will still have some flow via red to top of rad as it is still the main warm up circuit. See how it performs.

End up with pic 2? Good luck and I hope this works.

I wouldn't put off driving it as it is if the sun shines in the next few days. Short term workaround I live with but still niggle away at the problem in the back of my mind.

 

Nigel

Edited April 3, 2016 by Longboarder

[alanrichey]

It looks like you have an open circuit so to speak..The red from the stat will be open and allowing coolant to flow to the expansion tank. .from there the blue to the rad, the pump will there by be ignoring the stat..This will most probably be part of the problem.

I'd look into developing a simpler system. Not only to cure a issue but also less hoses and joints equal less leaks.

 

Makes sense, although actually I don't regard it as an issue any more as the car is behaving perfectly. It's now moved from being a problem to an intellectual exercise in thermodynamics.

[alanrichey]

 

Remote thermostat housing was a problem in the K and on your diagram the red line is vital for establishing warm up circulation.

 

Careful, it's not a 'K' it's a 'T', and it uses the standard cooling method, not the peculiar one used by the 'K' so don't get confused by that.

 

 

 

the red line should leave engine side of the stat, supply the heater and then return to the pump feed, not the top of the rad.

 

I agree, So far no-one has explained that RHE mod to me.

 

 

 

So I think that explains the early gentle warming in the stat to rad black hose which should stay cold till the stat opens and then suddenly become hot.

 

Eh ? Jumping the gun a bit here That was the test Jim recommended, and I have yet to carry it out. At this stage we don't actually know the stat is being bypassed,. And even then I would have thought that would affect the warm up time, not the final stabilsing temperature ? If you require a coolant flow of X through the radiator to keep the engine at a constant temperature I see little difference between a water flow of X through a full opened thermostat and a collant flow of 90% of X through a partially opened thermostat and 10% of X via other means. Same overall effect .

 

 

 

So first redesign of the cooling system is pic one but it's not complete. The red line should be moved to the pump inlet hose and be at least 15mm bore. But system is not self bleeding of air.

 

Sorry, I'm not really interested in redesigning at this stage, although I am happy to try temporarily blanking of lines for testing. As I said in my last post this has moved from a problem (which it was at the beginning of the thread and has now been fixed) to an intellectual discussion on the workings of the system.

 

 

 

I wouldn't put off driving it as it is if the sun shines in the next few days. Short term workaround I live with

 

You misunderstand, I am now totally content with the new design. Car is running absolutely perfectly for the first time in months. I think my next redesign will be to make the grill blanking plate adjustable so I can then adjust the running temperature to the EXACT value I want. Maybe just up it from 88C to 90C. Show me another car where you can do that

[Snapperpaul]

Coming into this thread at a late stage so will only give observations.

I immediately spotted the thermostat bypass issue with the header tank providing the flow through.

Simply holding the different pipes as the engine warms up should indicate which warms first

Taking cap off header tank should show if you have flow through.

If you have a working system and are running low temps then great most of us suffer from hot running.

 

My only only issue is reading the temps off the ECU and the assumption that this is a correct reading, I would try and get a second temp reading just to be sure

Edited April 3, 2016 by Snapperpaul

[alanrichey]

My only only issue is reading the temps off the ECU and the assumption that this is a correct reading, I would try and get a second temp reading just to be sure

 

Good point, although to be honest, as long as it doesn't boil over, I am not all that bothered about the absolute temperature value of the engine..

 

My initial concern over the the cool running was that all the things the ECU controls that use temperature as a parameter (fuel/air mix, ignition timing, idle speed.....) would not be working correctly because the engine was not running within the optimal 80C-100C band. So in made more sense to use the temperature used by ECU as the guide, regardless of it's accuracy and do something to get that value into the optimal band.

[Longboarder]

 

an intellectual discussion on the workings of the system

Exactly. At my remote distance from the earlier problem it can only be an intellectual conundrum. As with many of teasing snags that pop up on Rhocar I would love to fiddle with the bits as the engine warms up and see what gets hot/cold and in what order. I wonder what percentage of uncontrolled coolant is bypassing the stat and getting through the rad. Enough in these coldish spring days I presume to slightly overcool the engine.

I don't imagine there is much fuel enrichment in the ECU's temperature tables for it to be a problem.

 

Nigel

[alanrichey]

 

I don't imagine there is much fuel enrichment in the ECU's temperature tables for it to be a problem.

 

Probably not, and as I have now found out I had been running for 2 years with a broken lambda sensor so the ECU wasn't controlling the fuel/air mixture at all and I was running in Limp-Home Mode it is really academic. But like you with my cooling problem, now I have the extra information available to me I can't bear to leave something not quite right.

 

(Why do they call it Limp-Home Mode when the car actually performs rather better in that mode (apart from the emissions) then under normal conditions?)

[speedtripledan]

I dyno.d my 406 coupe v6 with a dodgy lamba it put out 30hp more on the dyno than manufactures claimed. It was running very rich at the time nearly killed the dyno shop with the fumes. The fault was intermittent and you could tell some days it flew others not so

Edited April 3, 2016 by DanE

[alanrichey]

Mine's the same. The default map runs the engine a bit rich and with a working lambda sensor the ECU leans it off between 3% & 6 %

 

Fascinating stuff.

[Kerry]

I believe the small hole in the thermostat is to allow a small flow of water to vent the system and allow the hot water to reach the thermostat

[Guest 2b cruising]

True about the air bleeding but the t/stat gets hot from the under side expanding the wax to open it.

If it has a hole, that should have a giggle pin in it.

Edited April 4, 2016 by 2b cruising

[alanrichey]

Just to close off this thread, having now run under my new system for 2 months I can confirm the old-school solution works (thanks for reminding me Mick). Even though I have also fitted a mesh behind the grid to go with my highly technical temperature velcro-controlled grill masking system I took her to Rutland Water yesterday on the hottest day of the year and she sat rock-solid at 88C all the way there and back and I didn't have to resort to turning the fan on.

 

 

I have to withdraw all the negative comments I made about the Superspec cooling system, once it is fixed, it's actually superb

[megadodo]

One question and then my thoughts. Where is temperature being read from and is it accurate (okay, that's 2 questions!)?

Now my thoughts.

If the cooling system is running properly then an oversized radiator wouldn't be an issue as the thermostat should be regulating the water flow out to it to maintain the correct temperature. You are having to block off some of the airflow which is the same as having too big a radiator. So, too much water is reaching the radiator whether or not the thermostat is opening or not. I would agree with others that the system is bypassing the thermostat somehow and is the root cause of your cool running unless of course the reading of the water temperature is inaccurate.

[alanrichey]

As I have said before in this thread the Temperature is coming from the ECU. I have no idea if it accurate but again, as I have already stated, that doesn't actually matter. Provided the engine is running fairly hot and not boiling over and the temperature gauge is staying within the Normal range then I really don't care what absolute temperature the engine is actually running at.

 

However I DO care what the ECU thinks the temperature is, as that figure is being used to set all sorts of other things, idle speed, ignition advance, fuel/air mixture...... So I like having the ECU think it is running at 88C rather than 70C as that is a nice hot temperature that means all the other parameters will be around the normal. If it is a bit inaccurate and the temperature is actually 92C, who cares ?

 

Maybe when I started this thread I should not have used actual values I should have used 'flipping cold. 'nicely normal' and bl...y hot'

 

But I don't really want to repeat all the points that have already been made in this thread as the other members of the forum must be absolutely bored to death with the subject. That is why I said I was closing it off

 

Bye

 

Al