If you're using a PRRT, what temperatures are you seeing?

[k80rum]

As the title suggests.. I'm interested to hear what coolant temperatures people are getting in use.

 

Here's the background - apologies if it seems long-winded:

 

I've gone the PRRT route on my K series. Initially I thought this had led to cooler running temperatures than before, based on the temperatures I was seeing on the dash.

 

It turns out the dash display was under-reading and I traced this down to the original (non-Stack) sensor being used by the Stack dash, swapping this over has resulted in the dash and the Emerald seeing pretty much the same temperature and I've verified the values below 70 degrees against a digital thermometer.

 

I've just started the car for the first time, let it warm up and driven it up and down the road, so haven't really gone above about 2500 rpm and only driven for a couple of minutes. My idling temperature after that is showing as around 92 degrees and the fan is running.

 

This seems a bit high to me, given that it's not even being stressed with high air temperatures at this time of year. Does a high 80s/low 90s water temperature sound about right to others with this setup? I expect it will come down when moving and I haven't done any runs at speed yet, but the original cooling setup read quite a bit lower (albeit on the old Caerbont gauges)

 

My plumbing setup looks like this

 

Darren E

 

Website and Emerald maps library

 

Superlight R #54

 

 

 

Edited by - k80rum on 14 Oct 2007 17:49:05

 

Edited by - k80rum on 14 Oct 2007 17:49:40

 

Edited by - k80rum on 14 Oct 2007 17:50:49

[Mr Locust]

Darren,

 

the whole point of the thermostat is to achieve a fast warm up and even running temperature in the engine. If you fitted a 88 degC thermostat I'm not sure what you expected. The fan switch on my car was 92/87 degC before I switched over to using the Emerald for control of the cooling fan. All sounds about right.

 

 

 

Ian

 

Green and Silver Roadsport 😬

[k80rum]

Many thanks Ian, it's reassuring to hear that the temperatures sound normal.

 

Yes, I was expecting the fast warm-up, it was the idling temperature that I wasn't sure about - low 90's just struck me as a bit hot. I've got the grey PRRT which I believe opens at 82 degrees. I suppose I may just be a bit paranoid but I'm worrying that if the dash is under-reading at all around this range, my margin of safety is quite small.

 

Could you or anyone else reading this tell me what a normal operating range is and what would be above the upper end of normal? I'd always believed that 70-90 was reasonable with 100-120 being dangerous and 120+ being HGF territory. Does this sound about right?

 

 

Darren E

 

Website and Emerald maps library

 

Superlight R #54

 

 

[Mr Locust]

I recently changed over to driving the fan output from the Emerald and have it set 94degC on 92degC off. That is in conjunction with a standard thermostat (presumably 88degC, never had cause to remove it).

 

Most of the diesel engine suppliers I deal with use 110/112 degC maximum top hose temperature as the basis of their application sign off criteria, so your assumptions appear to be in the right area.

 

Ian

 

Green and Silver Roadsport 😬

[Nifty]

According to the gauge mine runs at a steady mid 80's, using an 82^oC PRRT.

 

I was concerned that since I still have the senders on the old narrow bypass they wouldn't get a good flow with the larger bypass fitted, and would therefore give an incorrect gauge reading. However, the fan cuts in and out at the correct temperature on the gauge so all seems well.

 

Keep off the straight and narrow 😬

[k80rum]

Thanks Ian & Nifty.

 

Darren E

 

Website and Emerald maps library

 

Superlight R #54

 

 

 

Edited by - k80rum on 15 Oct 2007 13:59:34

[PAUL MARRIOTT]

I can support the above grey PRRT, plumbing as your's but no byepass and a laminova in the return from rad leg, idling temp max 92 fan on fan of at 89 (SPA guages) in traffic mid 80s open road, blatting, motorway, on track all steady at 83 +/- 1.

 

Paul M

[Bricol]

Indicated 82 C whatever the weather and wherever I've been - at high speed on a motorway somewhere off south coast (of France) all on our own or bunched up in a traffic convoy, or at high revs, slower speed up and over the Alps multiple times.

 

Oil temp . . .now that's a different story - climbs rapidly when in traffic on motorway at constant 90+ or so - just can't remember the temp it gets to - still within oil capabilities, but higher than I'd have liked once it stabilised.

 

Bri

[k80rum]

Much appreciate the responses Paul and Bri.

 

It certainly sounds as though I should be seeing a pretty steady 82/83 degrees at the dash then. I'll double check what my fan on/off thresholds are and that the system is completely bled, then see what I'm getting during and after a short blat

 

Thanks very much indeed.

 

Darren E

 

Website and Emerald maps library

 

Superlight R #54

 

 

 

Edited by - k80rum on 15 Oct 2007 18:35:10

[Slipper man]

What is PRRT?

 

Whatever it is though, over 90 deg is much too high. The Minister setup on R400/500's starts to go into safe mode at (IIRC) 86 deg. The ideal temp is low 80's. The later R500's with ECU controlled fans are set to come on at 84 deg.

[PAUL MARRIOTT]

Slipper

 

the 90deg is set by the standard fan switch, could change it for a lower set point I suppose or programme it into the emerald. But it's been doing 90+ at idle for 35000mls / 7 years without problem.

 

For PRRT see here

 

http://web.tiscali.it/elise_s1/

 

Paul M

 

 

[Unclefester]

I have had some very odd results with an Eliseparts remote thermostat on a DVA (Oily) powered 200+bhp Elise S1.

 

After fitting the unit, I noticed a strange cycling effect on the digital Stack water temp display....it would bounce around from 78 to 87°C, taking around 10 seconds to complete the range, then reversing.

 

I asked Geary Powell, and he said about 1% of S1 owners had reported this, and offered to reimburse me, which was pretty decent of him.

 

I have obtained an MGF variant of the grey PRRT Landy system for the Elise, and a grey Landy system for our SV.

 

Not quite got around to fitting the Elise system, as I need an aluminium 'T' piece for the heater hose to main right rad hose connection where I had to put the Eliseparts stat.

 

The most fun part of the job on an Elise is removing the original stat!

 

The joy of mid engines...... 🙆🏻

 

 

 

Lucy in the Sky with Diamonds..ooooh hooo hooo!!...

😬 😬Abbey Road Time-Machine *eek*

 

[Peter Carmichael]

More interesting, however... what is your coolant pressure?

[Kevsta]

Peter, can you expand on why? I think I understand about it...the build up of pressure that is then bad when the stat open (I have drilled a v small hole in mine)...I also had a look at stats in a motor factors and noted that they had some with jiggle pins...oddest of all was the spec of car they were intended for...it didn't make sense!

[Peter Carmichael]

Kevsta,

 

My comment is not particularly to do with the PRRT or the pressure waves associated by the large mass of coolant flow being decelerated in mid-engined Elise configurations.

 

In my recent rebuild, I had an extra channel in the data logging and I was reading coolant temperature direct from the ECU. I therefore used the spare tapping point in the submarine pipe to fit a pressure sender and log the data. It has made interesting reading.

 

On days/nights with cold ambient air, the pressure in the system at this point (just prior to the standard thermostat housing on the bypass pipe) shows 0 psi above atmospheric pressure at running temperature and at speed. This is at odds with it showing a healthy 7-10 psi normal running pressure on a day with hotter ambient conditions, or when builfing up system temperature at idle on a cool day.

 

I have drawn the following conclusion:

 

The airflow over the air gap in the expansion tank is sufficient to cool the expansion tank air down to close to ambient temperature, thereby removing all beneficial pressurisation from the cooling system

 

The answer would appear to be to lag or relocate the expansion tank.

[Kevsta]

Hmmm...very interesting....I have a solution ...only use the car when its warm outside (waits to be battered with a cod ).

 

Seriously though...What knock on effect would that have other than if the temperature was to reach boiling point (already higher with antifreeze etc. in the system) at which point I presume the pressure would then rise enough to prevent this? Only my speculation and I'm certainly not of the cailibre in engine technology etc as yourself Peter.

[Nifty]

Peter,

 

You spend too much time researching and not enough time driving ❗ ❗ 😬

 

 

 

Keep off the straight and narrow 😬

[Peter Carmichael]

Seriously though...What knock on effect would that have other than if the temperature was to reach boiling point (already higher with antifreeze etc. in the system) at which point I presume the pressure would then rise enough to prevent this?

 

It isn't any good hoping for "boiling" to give you sufficient pressure to "prevent boiling".

 

The issue is that localised hotspots in the working areas of the engine are not suffciently protected from hot surface cavitation erosion - the process by which most K-series fire ring "head gasket failures" occur.

 

Hot surface cavitation is known to most people through the loud noise your kettle makes some time before reaching boiling temperature.

 

You spend too much time researching and not enough time driving

 

Honest, I fitted the pressure sender to give an early warning of a duff pressure cap. 😬

[Nifty]

Honest, I fitted the pressure sender to give an early warning of a duff pressure cap.

So, do you conclude that the pressure cap isn't working when the ambient temperature is low 🤔 ............ 😬

 

Keep off the straight and narrow 😬

[Jason Plato]

why not simply fit a decent reliable pressure cap

 

here is C7 TOP

Taffia rear gunner

[Nifty]

I did Dave

 

Keep off the straight and narrow 😬

[Peter Carmichael]

Like, duh!

 

Because ifI'd done that I'd never have foudn out there's no pressure when the weather's cold.

[Peter Carmichael]

DOn't forget the corollary though. If your dodgy pressure cap goes, it is still OK to drive your car in cold weather *confused*

 

Edited by - Peter Carmichael on 18 Oct 2007 23:21:00

[Mr Locust]

On days/nights with cold ambient air, the pressure in the system at this point (just prior to the standard thermostat housing on the bypass pipe) shows 0 psi above atmospheric pressure at running temperature and at speed. This is at odds with it showing a healthy 7-10 psi normal running pressure on a day with hotter ambient conditions, or when builfing up system temperature at idle on a cool day.

 

Is that one of the criteria behind specifying an 88 degC thermostat in a Rover 25?

 

Ian

 

Green and Silver Roadsport 😬

[Peter Carmichael]

Is that one of the criteria behind specifying an 88 degC thermostat in a Rover 25?

 

I doubt it. The problem I am seeing is that the expansion tank in the Caterham installation sits in a blast of cold air that passes above the radiator. System pressurisation will be part of the design criteria for the production Rovers, but the the thermostat temperature doesn't get a look in. The air gap is air. Unlike the bulk coolant, it has no great specific heat capacity (kJ/kg/K) and no great mass besides. This means that a cooling blast over a quite small surface area is able to drop the temperature close to ambient... at which stage there is no system pressurisation.