rocketing temperatures when returning to pits (fixed)

[mcerbm]

I have a 215bhp VHPD engine with dry sump, radtech radiator, 82C stat with 2mm hole. I have an emerald ECU with the fan controlled by the ECU so I can select the on/off temps.

I have found that when on track the radiator keeps the temperatures in check, possibly even a bit low. I found that the gauge in the pits while warming up the car seemed to read true for the 82c stat. But out on the track it could read lower into maybe 70c which should be when the stat is closed, is this normal? i.e the radiator is cooling the fluid which is static and it brings down the temperature of the closed loop circuit (even though it wont be flowing except for the 2mm hole bypass).

If I do a cool down lap everything seems to be ok. If I come off track for whatever reason at short notice the fan comes on (87C on the ECU) and it cant keep the temperature in check, it keeps increasing so I either have to go out and get some fresh air through the system or turn the car off. On the gauge it would rise to 110 - 115C.

There are three things that I think may be happening.

1) Although idling is quite fast 1200rpm the water pump (upgraded recently) isnt flowing enough to get the fan cooled coolant round the system effectively.

2) The ECU temperature senders may be under reading so the tru temp the fan comes on is hooter than anticipated and its gon etoo far to bring it down.

3) The position of the temp senders in the water rail is getting a roasting from the exhaust headers and is giving a localised high temp

I was thinking of getting the remote temp sender to get it away from just above the exhausts as a potential solution.

[revilla]

I think what you're seeing may not be unusual. After a good caning on track there's a lot of heat stored in the metal of the exhaust headers etc. Shut it down or drop to idle suddenly and the water flow no longer matches the flow of heat back into the head so the coolant gets very hot. A cool down lap gives everything chance to come to equilibrium.

[Wrightpayne]

The water pump you fitted should have metal impellers - plastic ones are prone to snapping!

Ian

[mcerbm]

Yes that’s correct it has metal impellers. 

[mcerbm]

Revilla, if the exhaust has a lot of residual heat would you say that the whole water rail is getting radiated by the exhaust and the sensors are reading a bit higher because of this? I'm just wondering why there was a remote "submarine" option for the sensors which I believe was implemented on the R500. Maybe because that was a hard worked engine and they had similar problems due to the much higher exhaust temps?

I'm 119bhp/litre and have a 200 cell cat restricting things to  certain extent so under bonnet temps are quite high.

 

[SLR No.77]

Fit the remote sender submarine, until you get your senders away from the exhaust you really don't have any idea when stationary what temperature it's running at.

[Paul Mason]

Sorry if being dim, but following thread as curious to learn more about temperature fluctuations and coolant systems. What does “fitting the remote sender submarine” mean?

[revilla]

My understanding is... and I may well be completely wrong because I'm not a track driver at all... that when working hard there will be significant temperature gradients in many places, for example parts of the head and liners will be a lot hotter than the coolant. There is therefore a flow of heat along these gradients into the cooler areas which are kept cool by the circulation of the coolant removing heat out to the radiator. If you do a cool down lap, you run the engine for a while producing a lot less heat but still with good coolant flow, allowing the temperatures to move towards equilibrium. If however you come in suddenly, the coolant flow reduces dramatically at idle or stops if you shut down. There are still significant temperature gradients however, so heat continues to flow into the cooler parts and into the coolant at a rate greater than en the rate at which it being carried away. So for a while, the coolant temperature can continue to rise and sometimes quite dramatically given the low coolant volume of the K, until everything equalises. So although irradiation of the water rail may be giving misleadingly high temperature readings, some of it is likely to be genuine heat soak and a genuine rise in temperature after shutting down. If you don't have a chance to cool the engine on the track it might be a good idea to run at a fast idle for a little while where possible to keep the coolant flow rate up until it settles.

[Jonathan Kay]

What does “fitting the remote sender submarine” mean?

It follows mcerbm's and Stu's thoughts about local temperature being affected by the heat of the exhaust, especially when stationary. The submarine is a metal component of the cooling system that vaguely resembles one.

I imagine that you can relocate the temperature sensor in it.

Jonathan

[Jonathan Kay]

Andrew's description of the changes in heat transfer sounds right. Would it also be logical to switch the radiator fan on early in the process when you know that it's about to happen?

Jonathan

[SLR No.77]

The fan and radiator are perfectly capable of preventing a ticking-over engine from overheating, when you come off track leave it ticking over for a while and the temperature will reduce. Running the engine also enables heat to be dissipated via the cooling system, if you stop the engine the heat will not be dissipated and can cause localised boiling, not good.

With the senders in the coolant rail you really have no idea what's really going on, get a sender submarine fitted into the bypass hose ... or heater hose if you're a wuss and have a heater.

[mcerbm]

Sforshaw, unfortunately my problem is I cant leave it ticking over for a while as the temp rises pretty quickly. If I get a cool down lap in then yes the fan does manage to keep it under control at tickover. But if I come straight off or after half a lap cooling down then it just escapes.

I have a map that I use with an earlier kick in temp of 60 degrees that I switch using the emerald map switcher as soon as I know I have to come in, but it still goes out of control even with the lower fan cut in point (assuming no cool down lap)

I should probably mention that all this is done in a competitive environment, so if I get a red flag in the session I may have to come in with no ability to do a cool down lap, and when I come in I want to get a good position in the queue to go back out on track.

If I came in and the temp rises quickly I would either shut off (yes not good as the heat is still there) or go out on track assuming no red flags and get air through the radiator. I wasnt sure if a fast idle say 2500rpm would induce too much heat through higher rpm to cancel out the better flow from a faster water pump speed, or if its exactly whats needed. I didnt experiment at the time unfortunately.

But yes I am sold on getting the remote submarine and getting an idea of the fluid temp and not just the water rail heat soak temp.

I may wrap the exhaust but powerspeed mentioned specifically not to do this. But it seems common place in other caterhams. The only difference is that I have a CAT.

 

[Dave J]

use an infrared temperature gun to see what temp the rad really is 

[mcerbm]

unfortunately the car is away for the winter so no further track days. I will install the submarine and see how it goes in the new season. If it is still bad I will look at wrapping the exhaust headers or upgrading the fan. I was hoping to fit an undertray to the car to reduce drag but will have to get ontop of this issue before I increase under body temps further!

[SLR No.77]

Tomorrow morning get onto Caterham and have them send you the submarine JK has posted in the picture plus blanking plugs for each of the threaded holes. Then fit it in the bypass hose. Then see if you have the same problem. All the information you have about temperature is from the gauge and where the sender is located is pretty well the hottest area under the bonnet when you're not moving, therefore until you've moved the sender all other comments are irrelevant. Also worth getting a temperature gun as Dave has mentioned, they're quite inexpensive now and good to help know what's going on.

There are differing views on wrapping the exhaust manifold, with the power you have I'd be concerned about retaining too much heat in the head, I've wrapped mine in the past but this became a concern (my VHPD is running more power than yours) and I now run unwrapped with no issues to other components.

Stu.

[mcerbm]

Thanks Stu, totally agree. Submarine will be installed and I’ll see where all this sits on my next trackday. I did do a temp comparison with a temp gun on the radiator inlet hose and the readout from the ECU sensor in the emerald software. This was done after the thermostat had opened but only at idle. The ecu read maybe 5C - 8C above the hose. That might be the start of the heat soak or just the thermal properties of the silicon hose not transferring all heat of the coolant to the outer surface of the hose. 

[SLR No.77]

Both the ecu and gauge sensors are located in the coolant rail, they'll both give false readings at standstill. More so with the gauge sensor which is over no.4 primary but the ecu sensor is also very close.

[TomB]

That's interesting , I didn't know such a submarine pipe existed. Does it go between the stat and radiator where the other metal pipe known as a 'submarine pipe' goes? If so, where is the take off for the narrow pipe to the coolant header tank? Any pictures of it installed? Would relocating the temperature senders help with accurate fueling and ignition from the ECU

 

 

[SLR No.77]

It fits in the 16mm bypass hose around the back of the engine, or if a heater's fitted in one of the two heater hoses, doesn't matter which although the one between the end of the coolant rail and the heater is probably the most convenient.

On an earlier cars (IIRC pre 98 ish?) it'll also need earthing because the gauge sender is only one wire, earthed through the coolant rail, that's why there's an M5 rod sticking out of the side. Twin wire gauge senders don't need the earthing point.

Stu.

Edited to add, if you order one make sure you get blanking plugs to fit in both the holes, they're needed to blank the holes in the coolant rail when you relocate the senders.

[TomB]

I see, so as I have no heater it would on the hose near my T-piece. If it fits inline, does it need any support or is it OK to install within the pipe? Given its location, it would required minimal wiring modification to move the senders from the main coolant rail.

 

It might make for more reliable readings - however, as my exhaust headers are wrapped, there is less heat below the rail than there could be.

[Albert Donaldson]

Interesting, I have repeated suffered with this on both a 180bhp K and a 220bhp K. temperatures absolutely fine on start up and when racing, come into pits and temp just keeps on rising. At first I couldn't understand why the fan would not come on but discovered that the emerald does not actually control fan its done by sender in radiator. Eventually I just put a switch in to turn on fan manually, however does not seem to cure. I'm going to try the submarine to relocate and see what happens. 

[SLR No.77]

Albert, the Emerald can control the fan, it may be that yours isn’t set up that way. The standard setup is through the temp sender on the top/rear of the radiator but there are pin-outs on the emerald that will do the same job but will need connecting.

Fit the sender submarine first though!

[mcerbm]

Since it is all associated with my cars cooling issues I wouldn't mind some comments on further changes I was planning to do to the cooling system. I already have a 82c stat with hole and top up point in the bypass hose  

1) the low flying article header tank mod. Header tank feeds into the bypass pipe rather than the tee piece on the radiator outlet. Supposed to have more even pressure input to the water pump. Be more consistent to fill the coolant system with out air locks. And allow my 82c stat to work more effectively by introducing hot water on the bypass side during warmup. 

2) removal of oil radiator and replacing with laminova heat exchanger in the top radiator pipe. Current problem is I struggle to get oil temp up and I do sprints / hill climbs and also a time attack type event (superlapscotland at knockhill). So I can only idle the car then it gets full whack off the line. The rad fan currently partially covers the mocal oil radiator which sits under the radtec radiator. Coolant gets up to temp fan comes on and starts to cool oil. I have blanked off 70% of the oil radiator now and it works a lot better now when on track (previously over cooling) but still it’s too cold for sprints etc. I’m in two minds wether to do this or not. 

[SLR No.77]

All the changes you are suggesting are positive. Personally I would do them in the following order with time between each to discover what effect each change has made:

1. Sender submarine (cheap easy and a definite must-do);

2. Get rid of the oil cooler and fit a Laminova;

3. Swap your stat and plumbing as you describe (this is the Rover PRRT mod).

 

Stu.

 

[mcerbm]

Stu, it wasnt the PRRT fix but just a re-plumbing of the header tank which an old rover engineer suggested was a better idea. It was in low flying sept 2012. I'm leaving the PRRT idea for now and hope the other fixes help me.

My only doubt about putting in the laminova is I lose the ability to tailor my on track oil temp by blanking a dedicated oil radiator. Having said that if they both sit approx the same temp I could blank off some of my radtech radiator to achieve the temps I want (just not blank the bit the fan occupies for obvious reasons).

Is there a sandwhich plate type heat exchanger solution that could integrate at the oil filter housing available (like duratecs I believe?), or is the laminova th eonly k-series option?