Cylinder head cooling, thermostats and expansion tanks: Discussion...

[Jon Olds]

Has anybody attempted to improve the design of the GTIR cooling system, specifically;

1. The thermostat being near the top of the engine, so it will/may close if the water level ever reduces.. My mk1 golf has it at the lowest point, surely the sensible place for it.
2. The top hose level is around the same level as the water in the cylinder head. The cylinder head internal waterway surface area must be under 100% water coverage if local hotspots are not to be a problem.
3. There is no expansion tank, just a blowby valve system that I have minimal faith in
4. Ruddy great front mount in front of the water radiator.
5. Water pump speed has been questioned
6. Stuff all air flow out of the bonnet area, plenty of potential air flow in.
7. I have a double row copper rad in now, thinking they are more efficient than alloy for the same physical size?
8. Localised boiling after shutdown from full load a problem?
9. Water pressure at full engine load. ie is it enough to blow water out past the cap?
10. Water wetter work?

Possible mods;
1. Relocate thermostat, possible a remote unit at/near the bottom of the engine.
2. The existing bleed hole could be piped to an expansion tank, so it would bleed when running, or another tapping (1/4"?) could be T ed into the top hose and fed back to an expansion tank
3. Most cars have an expansion tank, why not the GTIR? No room (packaging?) No height available? (engine too tall?). I intend to add my own
4. Probably going to downsize my IC, as its hard up against the rad, so it doesnt get smashed when i 'rub' straw bail chicanes
5. My car peaks at 6K due to the turbo 34mm inlet restrictor, do I need to run a smaller pulley?
6. Going to attempt to 'aero' the air out, to get more flow.
7. Try an alloy rad (i have one already) when I do 4.
8. Electric water to circulate the water after shutdown
9. Going to plumb a dash mounted gauage in, out of daftness
10. Try some, but I am usually sceptical about american wonder fixes

The reason I am asking myself these questions is my rally car gets a real caning from warm for 5 miles the cools off, 8 times usually in a rally. From a thermal stress point of view this must be near the worst case scenario..
At stage end the gauge (midway up the bottom hose, capillary type) reads 90-100.
Had the head off mine a couple of times, as a precaution for a look. Never had any sign of head gasket issues.

It would be good to share these thoughts with you experienced guys. Feedback welcomed....

Jon

 

[warpspeed]

I'm fitting my rad in the boot just now with a swirl pot on the bulkhead and I'm using an electric pump, also not using an intercooler so will have a nice empty engine bay.
As for airflow, I'm using a flat bonnet with 3 vents for getting air out.

 

[Fast Guy]

Jon, are you actually having any problems with your cooling system? Is 5 miles running much more than 5mins driving? And how long cooling inbetween stages?
My car will reach 94 in slow moving traffic before the fans kick in and bring it back down, so as long as you have a pair of good fans you should be OK. You have alot more forward airflow to help cool you.

I would have thought if the water level dropped then the heat the thermostat would see would increase as there's no water cooling it or the metal around it from the several hundred degrees of heat working it's way out from the combustion chamber walls.

The overflow bottle does the same as an expansion tank doesn't it? It allows somewhere for the overpressurised system to go to, then allows it back into the system when it cools down. The only difference is that it isn't inside the pressurised part of the system like an expansion tank.

Unless your front mount is too efficient and you can afford to reduce its' size, then doing so will only increase charge temperatures and increase the temperature inside your engine (reducing power and increasing risk of det) and hence more heat back into the cooling system.

Don't shut down from load if you can. it will hurt the oil system and turbo more than the cooling system. I did read many years ago that if shut down hot you tend to get a syphoning action working around the cooling system which keeps some circulation going for a while. How effective that is I don''t know.

If water does blow out under pressure then it sucks back in when pressure reduces (or at least it's supposed to). Just keep an eye on your level to make sure your not blowing more than you suck.

I did use water wetter in my montego turbo, but I can't remember the results now. Have you seen that latest waterless (exspnsive) coolant?

 

[red reading]

Steady temps in my car whilst running hard on the dyno and anywhere really.....and that was with a standard uk sunny radiator.

 

[Mad]

Same as dan, never had any problems. I'm running a nasimoto (spelling) rad and i used to run a fan switch too but only needed to use it when in traffic.

 

[Jon Olds]

Jon, are you actually having any problems with your cooling system? Is 5 miles running much more than 5mins driving? And how long cooling inbetween stages?
My car will reach 94 in slow moving traffic before the fans kick in and bring it back down, so as long as you have a pair of good fans you should be OK. You have alot more forward airflow to help cool you.
Yes, I think I am. I need to add water as the day progresses. 5 miles 7 mins ish, stage average. 20 to 30 mins between stages. But I would pull the cap off and sometimes spew hot water at 15 minutes.

I would have thought if the water level dropped then the heat the thermostat would see would increase as there's no water cooling it or the metal around it from the several hundred degrees of heat working it's way out from the combustion chamber walls.
Not convinced. At all. Pure gut reaction though. Still a worry

The overflow bottle does the same as an expansion tank doesn't it? It allows somewhere for the overpressurised system to go to, then allows it back into the system when it cools down. The only difference is that it isn't inside the pressurised part of the system like an expansion tank.
How long doies it take to 'hoover ' back the water? How much is lost due to evap? Don't like the design at all, its like an afterthought

Unless your front mount is too efficient and you can afford to reduce its' size, then doing so will only increase charge temperatures and increase the temperature inside your engine (reducing power and increasing risk of det) and hence more heat back into the cooling system.
Forge front mount, so its massive. Have got a pair of K type thermocouples for a before/after measuremnet, but not got around to it

Don't shut down from load if you can. it will hurt the oil system and turbo more than the cooling system. I did read many years ago that if shut down hot you tend to get a syphoning action working around the cooling system which keeps some circulation going for a while. How effective that is I don''t know.
End of stage is park up and service, cant leave car running for > 5 mins after stage end. Block and other big lumps of metal are huge heatsinks, so re-boiling with no circulation is a possibility

If water does blow out under pressure then it sucks back in when pressure reduces (or at least it's supposed to). Just keep an eye on your level to make sure your not blowing more than you suck.
Adding water..

I did use water wetter in my montego turbo, but I can't remember the results now. Have you seen that latest waterless (exspnsive) coolant?
Would like to try it.

Thanks for the thoughts, this was what I was hoping for, a technical discussion

 

[Fast Guy]

If you're pressurising then possibly head gasket (cracked head a long shot)? Would have thought 15mins would be enough to cool down somewhat so as not to spew out due to residual heat.

The obvious - you don't have any small leaks in any of the hoses?

How much water are you adding? Straight water or coolant mix as I believe water on it's own is not as good a coolant.

I would have thought evapouration would be slow enough that in your circumstances it wouldn't be a problem.

Do you have good fans? 2 of?

 

[Jon Olds]

Maybe I have lost faith in the system TBH.
I have had two small leaks down the back of the engine, from some redundant 1/4" tapping off the main pipe. These are now welded up.
I need to make a pressure test cap, and pump it up with a footpump.
Usually use an AF mix 50:50, but have put neat water in also, as a last chance thing.
Thought water had very good heat trasnfer properties?
Good to have the discussion.
More comments welcomed
Jon

 

[red reading]

water does have very good thermal transfer properties till it boils, de ionised is the best. are you still having issues jon or is it just old pipes leaking?

 

[PobodY]

The only problem with DI is that it's corrosive. - Think of it this way; water usually had a whole load of metals dissolved in it, if you take them out it will try to find more to dissolve back-up.
Tap water isn't, but it's often full of calcium which can precipitate out and leave scale.

Obviously that's why you need to add a good inhibitor when you make DI into coolant.

 

[red reading]

Never knew that...logical when you think about it, what about using boiled water as that gets rid of a lot of scale?

 

[Jon Olds]

Pulsar has had a 'rest' (other toys to play with). Still thinking about the cooling system though. Latest thoughts are the pulsar front mounts everybody runs (me included..) may be oversized. A half sized one would give the rad a better chance. I see a similar symptom on my aftermarket turbed merc camper van.
Need more testing before I start chopping stuff around, specifically proving I have no water loss probs.
Jon

 

[red reading]

what sort of average speeds are you doing jon....it maybe overall airflow is the issue?.

 

[Jon Olds]

Since the Group B days, clubs have had to put chicanes in to slow us down. So, lots of 2nd, 3rd, 4th full acceleration, then full brakes (and I mean full brakes..) Mostly 30-100mph. Typical stage 8 mins, 70% plus at full throttle, I guess. The car is happier on the faster events. It also overtakes more at the end of the straights. There is no airflow IN control. I have the IC as far out of the way of damage as possible, hard up against the rad. Not helping. I don't duct air in to the IC as the ducting may get wiped out. Front bumpers are a bit sacrificial. The braking zones into the chicanes are usually littered with loose gravel and I am a late braker...

 

[red reading]

so you need a water spray system then, and possible others that are protected from damage......going to have a think on this as airflow is an issue for you

 

[PobodY]

After having been schooled by Jim and Ed on the subject of water injection, I was thinking that you could modify something like an Aquamist to operate as an intercooler/radiator spray. - Obviously that's more costly than just getting an old windscreen washer pump and letting that spray, but it gets much better nebulisation (which means more surface area of the water you're spraying, so increased efficiency).

 

[The Doc]

Also if you use the correct chemicals you will get better cooling from evaporation to take the heat away. i would look at fitting fans into the bonnet to pull the excess heat away from above as this is a point that is not likely to be damaged and there is room for some duct work under the boonet to improve air circulation.

 

[Jon Olds]

Fans. Good idea. Ive got a bracpan fg bonnet though and it would break my heart to hole cutter it. You've got me thinking though. I used a motorcycle cooling fan to blow air over a horizontal oil cooler on a race golf 10-15 years ago and I still have it somewhere. Under bonnet packaging may be tight though for ducting. The whole air in and air out thing needs improving

 

[Jon Olds]

also noticed waterless coolant around at 50 quid a gallon. anybody any experience?

 

[The Doc]

Have you also looked at using pvc or similar sheet to duct air from the bumper to the radiator as per the nissan group 'N' manual, as for the fan idea try having a look at a large single 14" maybe fan on a flat sheet bolted to the bonnet and blowing out of the standard intercooler bonnet vent?.