620 Cooling - Radiator Bypass Loop

[Shortshift]

Whatever the technical rights and wrongs of this, I am really enjoying the high quality graphics!

James
 

[CtrMint]

Thanks Mark, got a better understanding now.

@James...  

[Titanium7]

As mine is still under warranty Oakmere has got agreement from Caterham to look at the overcooling so it's in there this morning. 

Here is the typical indicated temperature when running at 3000 revs with the ambient temperature around 15C. When you stop at traffic lights it shoots up to 90C when the fan kicks in and then drops again to 50C when you start motoring again.

 

 

[CtrMint]

It will be interesting to see how you get on.  As you know mine is under warranty too but Oakmere wasn't prepared to do anything other than fit the preloaded one-off thermostat which CC recommended, a stat CC admit hasn't gone through testing etc.  

Your temp behaviour is the same as mine, although over the mountain I can get mine into the blue.

[CtrMint]

My carbuilder parts have arrived today, amazingly quick service!  I'll put some photos up for completeness.  

[CtrMint]

I've upload some pics of the parts to my instagram. https://www.instagram.com/caterham7diaries/

The Gates flexible hoses are really nice, nice and thick, yet flexible, the internals are still smooth too.  The thermostat housing is OK, its Gates too, but it's surprisingly heavy.  I guess its due to the thick metal construction.  RimmerBros shipped the 82c stat today too, so I'll have a choice.  I've also bought some Red Viper Performance Superflex 32m and 19mm hoses, along with T clamp hose clamps. I've got plenty of parts to build with this weekend.

If I can find the motivation this evening, I'm going to have a run up The Mountain with the GoPro and Easimap, (assuming the battery on the old laptap survives) to get a baseline.  

[garybee]

I've never been a fan of the Gates flexible hoses having used the Vulcoflex type in the past (maybe new version is different?).  They tend to take a fair bit of force to form a curve.  Good for mocking up a system though.

[CtrMint]

Thanks, I've got the Viperperformance hoses coming too, so I'll be able pick the better hose from that.  

[Doctor]

Mine does none of this now, stays nice and warm. Let us see what does it say to the race track. 

[CtrMint]

Unfortunately the GoPro went flat, I thought charging it off the PC all day would work, guess there wasn't sufficient current from the USB when the PC was in standby.  Also didn't get an amazing run, however there's certainly enough data from the Easimap capture.

If anyone wants to take a look, here's the capture in csv and native easimap.

https://drive.google.com/drive/folders/1K2JAa8DAJGlli3iE_PpQulZ5DcFm6tlF?usp=sharing

 

[CtrMint]

Probably doesn't need any explanation

Link to the jpg

https://drive.google.com/file/d/1W527DL6nsCDLzwGpG8VicEDfEsYFttXD/view?usp=sharing

[CtrMint]

Having studied my chart now, knowing where I was and the speed etc. I would suggest this has more to do with the force on the thermostat rather than volume of air passing through the radiator.  The initial drop off in my graph was caused by strong use of RPM, but not high speed.  Higher speed sections over the mountain were actually lower RPM and didn't result in as much cooling, although I appreciate the temps were much lower by then.

[nutty7]

 I would suggest this has more to do with the force on the thermostat rather than volume of air passing through the radiator.

Could this not be proved, disapproved by just revving the engine when parked up.

[Mark w]

"Force on the thermostat " ? 
 

Maybe flow through the uncontrolled cut out around the thermostat ........,,, 

[Mark w]

Mark

ive sent you a mail 

[CtrMint]

Replied.  -- Easimap logging setup.

Btw, the work we did last year on the ECU should provide the option to permanently log the car from the OBDII without the need for a laptop and then export in a similar fashion.  We should be able to to get the hardware to around the size of a credit card, costing about 60GBP.   Sadly it's just time and motivation to finish the project.  Hopefully, we can get there, and share the solution.

[Shropshire AR]

Well my 620 has been in Oakmere for a couple of days trying to address the overcooling issue.

It appears they have changed the thermostat for what I can only assume is the preloaded one that CC have suggested.

The result is the running temperature at 3K revs has now moved up from 50C to 60C. The biggest change is that the speed of change of the temperature is much slower. So it takes longer to warm up (not an issue for me). Overall on a 40 mile return journey back of country A roads with periods of high revs and mixed speeds   Some stops at lights the temperature stayed between 65C and 80C. 
So, this does not negate the badly designed system and it’s inherent fault of not holding a steady temperature but it will do me for now until the warranty runs out or one of the team come up with a cost effective remedy.

At the moment I would lean towards a PRRT system having good success with them in the past but may be persuaded otherwise when the current tests by others have been completed.

 

[Doctor]

Hi Martyn, what exactly is preloaded thermostat? Stiffer spring??

[Titanium7]

Yes I suspect that's all it is. 

[Mark w]

I don't see how a stiffer spring would cause it to take longer to warm up .
If the stiffer spring slows the thermostat  opening you would think the reverse is true . 
 

 

[Mrp]

I'm not sure this post is helpful, but it is really interesting to follow as an engineer. I was lucky enough to have the choice between a 420R and a 620R both of which were available within my budget  when I decided to upgrade and trade in my 140 Supersport. Also having met IOM Mark at last years Chippy run.

As far as usability as I don't do track stuff I'm now pleased I choose 420R also following this thread.

For those of you that know me and what happened just after I took delivery, should be happy to know that RBTB are being added during the repair I hope.

Mrp 

[JonT]

Would drilling the thermostat have the effect described? You'd always get some flow through the rad, so it would take longer to warm up, but you'd also then need /much/ more flow to push it open under flow rather than temperature alone. 

[Shropshire AR]

No need to drill the thermostat as there's a milled cut out in the housing already allowing flow through.

[elie boone]

I have to admit i am not familiar with the 620 primary cooling set up but what if the primary circuit would only heat up the oil cooler ? so to connect the metal tube behind the thermostat to the oil cooler and going from there to the cylinder head outlet that way you would have a cooling flow in the engine and a more steady rise and fall in cooling temp when the main circuit opens but then one can't use the ali. thermostat housing with the big hole in it.

[CtrMint]

Having spent a fortune on hoses and connectors, I might be stuck before getting going. 

I kinda worked from memory regarding the space available, a bit of an amateur mistake I know.  Having been into the garage this evening and offered up the PRT housing I have to say, there is surprisingly little room for the additional hoses and PRT stat.  I've spent a small fortune on hoses to give me the greatest potential for success, even so, I think I'm being overly optimistic about getting stuff routed without risk of contact to the intercooler or belts.

The solution Mark W is working on in the other thread is probably the better strategy at this time...   I was so confident about this weekend too.  Kinda gutted my skills are letting me down here.