620R cooling

[Mark w]

Chris 

I think it does and I've been trying to get my head round how a larger diameter bypass would help the engine run hotter .

The larger bypass would return hot water more quickly thus informing the stat to open and regulate a hot engines temperature down by letting in more cold water quickly but owners are reporting the opposite problem ,cold running ,suggesting either the stat isn't there ( as it wasn't on early cars pre the stat modification ) or there is too much cold water getting through .

The " too cold running " isn't symptomised by a rapid drop after getting hot whilst stationary followed by a quick blat during which the system might take time to catch up and close the stat . It's more characterised by a cooler engine temp in steady speed running when the radiator water is getting very cold due to low ambient temperatures . Increasing the temperature of the return water from the rad does cure the problem albeit I do accept that blanking off some of the rad in the winter does seem less elegant a solution than a more sophisticated engineered solution .

 

 

[Doctor]

What is the constant circuit in 620?

[Mark w]

For ease of reference ive put the 620 water inlet picture next to the " standard " plastic version 

Ive made the assumption that thermostat fitted to the plastic version is the one used on the 620 .

The thermostat flange has a cut out on it to coincide with the expansion bottle feed used on " normal " cars .

This cut out definitely coincides with the hollowed out section on the alloy version ( mid position of the two bolt holes ) . Does anyone with an intimate knowledge of this thermostat design know if it has any capacity to flow through this  cut out when notionally closed ? 

 

 

 

One thought that crossed my mind looking at this is that the central dished section of the aluminium plate needs to be hollowed EXACTLY the same depth as the thermostat body is thick so that its clamped in its seat  .If its hollowed out too deeply the thermostat wont be clamped in position and even in its fully closed position cold water will bleed round the outside of the thermostat as its pushed towards the engine block ----- 

 

 

 

[Doctor]

How about drilling the hole through the cut out on our alloy flange and fix the 16mm elbow there aimed towards the back of the block? That would give us the ability to connect the expansion tank feed and use the bypass pipe return for its original purpose. 

The bypass would originate at the cast water outlet at the back of the cylinder head behind the number 4 that we can modify to add the 16mm elbow instead of the bottom plug.

Problem solved?

[7 wonders of the world]

Doctor - see where your coming from but no 

We need to establish which stat is inside the new alloy housing first.

Looking at the plastic version purely for reference purposes and clarity, the small 16mm pipe is where the expansion bottle would feed into, this allows water flow irrespective of thermostat position, therefore the bleed and bottle return always has a circuit.

32mm inlet is the return from the rad (cold water) which open flow once the stat has opened and permits flow.

gold bypass hose into the block communicate water temp directly to the stat and once the stat is open is itself closed of via the small disc on the bottom of the stat.

If for reason of space we cant rework the pipework in this area I have other thoughts too... 

 

[7 wonders of the world]

Just looking again at Mark's photos It does look like the OE stat is removed from the plastic housing and mounted in the new version though and retained with what looks like a m3 blind hole in the housing....? cant zoom clearly enough to confirm though.

 

[Shortshift]

Given the number of people who are clearly dissatisfied with the standard cooling system on their 620, it seems to me that there is probably a reasonably sized commercial opportunity here for anyone who can come up with a properly engineered retrofit kit.

James

[7 wonders of the world]

the small cut in the new alloy housing looks to be open to the main machined centre too, meaning that the cold return from the rad cannot be fully closed and will always bleed back via this.

compare to the plastic OE where the stat centre sits and closes the 32mm inlet fully.

again an easy enough mod to sort if we can establish space for a new inlet in the housing too, whilst the OE is 16mm in order to facilite a heater return, this could be reduced to 12 (1/2") or even 10mm if your not running a heater. 

[Purplemeanie]

Hi Folks,

  I'm late to the party here... I know this is a 620 discussion but just wanted to throw in some work I did for my blog a couple of years ago when doing my 420. I hope I got everything right but it might help some people visualise what's being talked about, I appreciate its not the same as the 620's but hopefully the diagrams and the animations help the discussion. And of course I may have got some stuff wrong when I was writing things up and would greatly appreciate any corrections if I have.

https://www.purplemeanie.co.uk/index.php/2017/09/23/build-session-17-5-caterham-420r-water-and-oil-overview/

Cheers, John

[Doctor]

OK, we need to take one apart then. 

[CtrMint]

I've not had chance of a late to logon to BC, but just want to say great support to the original thread, thanks.

Would it be helpful if I record video of the engine bay to help clarify layout, or are things pretty clear now.

 

[Mark w]

Mark

if you have a heater I wouldn't mind seeing how that's plumbed in .

[CtrMint]

I do.   I'll sort a film out

[Mark w]

The interesting bit will be where your heater return pipe is connected ( assuming your expansion bottle is connected to the bypass connection on the block .....

[Doctor]

It will be T-ed into it. 

[7 wonders of the world]

Mark (IOM)

if you have a borescope probe might you be able to film around the area the alloy water inlet fits to the block please - interested in what clearance exists around this and the Rotrex plumbing..?

[Doctor]

I might help with that as well, mind you, mine is an SV. 

[7 wonders of the world]

 

[Doctor]

Had a look at it yesterday - the coolant inlet comes in between the supercharger inlet and the plenum chamber inlet - not much space left. Lack of space is the primary reason the plastic thermostat housing does not fit. 
 

the solution in my opinion it to modify the billet aluminium flange by adding another pipe inlet (16mm) for the header tank to connect into. Aligning the new pipe inlet with the thermostat bypass would allow the header tank to be in permanent flow circuit. This would then free up the bypass inlet on the block for its intended purpose - for the bypass hose coming back from the cylinder head. Job done. 
 

Another temperature management issue is the lack of oil temp measurement on 620R - this is criminal. I'm in the process of sorting it out. One more addition I would consider is coolant/oil heat exchanger to help with quicker oil warm up - 10W-60 causes oil pressure to run at 65lb/inch2 when cold falling to 30 when warmed up. This could either be a stand alone unit or incorporated into the oil filter housing. 

[Titanium7]

Here is an image of the 16mm Heater/Expansion bottle pipe running to the block above and I assume behind the thermostat contained in the bespoke billet thermostat housing. 

[CtrMint]

Well I was just going to use the iphone.... 

If anyone is interested we could do this using a live Youtube stream which everyone could comment on?  Let me know if there is sufficient support for that.

[Mark w]

This diagram says to me that the heater circuit is the bypass and the expansion bottle is Td into it .

 

 

[Titanium7]

Yes I would agree with you Mark.

[Mark w]

I think the Bypass " missing " is a good call and could be rectified but I also think , possibly a greater issue is the volume of cold water that comes from the radiator , even when the thermostat is supposedly closed 

[7 wonders of the world]

Which is the point I've been making all along.

The new alloy housing has a constant flow from the rad - which need modifying to stop this.

the additional feed to the alloy housing needs to be re established as I previously mentioned with a little creativity this can be achieved, dropping the hose to 12mm or even 10mm is space is very tight, though the larger to better if it has to serve a heater too.

The alloy housing also need to be checked to ensue its either got the correct stat or is capable of housing it.

Oil wise you can add a Mocal OT2  -12 stat, in the scavenge hose this can be specced with 89 or 92 degree stats. the cheapest place I've found is here, the 92 degree is to order or you can buy a new waxstat for about £15

http://www.mattlewisracing.co.uk/product.php/1835/0/mocal_remote_oil_cooler_thermostat

Oil temp we had some new parts made up to replace the pear drop shaped cover on the Raceline DS sump pan which retains the gauze finger, ours now have a nice boss on them to house a temp sender in the oil flow to register peak temps.

If theres enough interest I can see about getting a batch made up...?