Charge Cooler Header Tank

[Evil_Dr_Fish]

Hi guys...

Why is the Chargecooler Header Tank a lot smaller than the 'main' header tank?

Are there any advantages / disadvantages to larger or smaller tanks? Does it ideally need a pressure realease cap?

Many thanks all,

Robin

[neal]

Not that I have one but:

Why is the Chargecooler Header Tank a lot smaller than the 'main' header tank?

The capacity (in terms of coolant volume) is a lot less in the chargecooler circuit that the the engine circuit so it expands less when heated.

Are there any advantages / disadvantages to larger or smaller tanks? Does it ideally need a pressure realease cap?

It should be sized so that it will be full at the point where the coolant starts to boil, at which point steam will be released and you lose the coolant anyway so a larger one doesn't help. Which brings us onto the pressure cap. It's less essential than the engine circuit (hence the lower stock pressure setting) since you're less likely to boil the coolant unless you're really working the turbo/chargecooler. But it doesn't do any harm to use a pressure cap to raise the boiling point somewhat. With the pressure cap and a boiling point of say 115'C the intake air temperature will be at the point where the ECM should start reducing the boost and retarding the timing anyway.

[98GT3]

Hi guys...

Why is the Chargecooler Header Tank a lot smaller than the 'main' header tank?

Are there any advantages / disadvantages to larger or smaller tanks? Does it ideally need a pressure realease cap?

Many thanks all,

Robin

I don't know for sure, but I would imagine that the chargecooler header tank is smaller because it doesn't have to cope with the extremes of temperature as an engine cooling system header tank and therefore the expansion and contraction of the fluid is much less. The tank has to be large enough to cope with the rise and fall of the fluid, if the tank is too small, then it will loose fluid under expansion and could when cooling contract to completely empty and draw air into the system. On the next cycle of heat and cool, if the trapped air cannot purge for whatever reason then it will purge even more fluid from the tank and so on. I don't think a tank can be too big, but it could take up luggage space!

Phil

98GT3

[Jonathan]

The later cars don't have tanks at all !

The coolant for the chargecooler is filled via the chargecooler itself.

Any expansion is taken up in the main pump vacuum side, the head of water in the main tank then acts as it's effective pressure cap.

Any contraction is sucked out of the main coolant tank as it cools in a similar way as the main tank sucks back from the expansion bottle.

Fact is a working chargecooler should never get more than 10/20 degrees above ambient on normal driving (perhaps more on sustained boost and top end speeds) so it wont expand much.

[bzguy]

The later cars don't have tanks at all !

The coolant for the chargecooler is filled via the chargecooler itself.

From what model year on Jonathan ?

[Evil_Dr_Fish]

Great stuff guys - thanks

So... a pressure release cap may be an idea but just in case something goes wrong?

The header itself - do I take it that it doesn't really need an overflow in that case and simple "in and out" pipes will suffice and a capped hole in the top to initially fill it through!

[Jonathan]

One and t'other.

Anything pre 1993 uses the twin tank, early S4 did and so does the SE, they rust plenty.

After S4 (S4s / GT3) used the single plastic tank which dont rust and is sorta see through so you dont have to rely on your wires.

I've modded my SE from a twin to a single out of convenience.

I take it you wanna fit a chargecooler system ?

IMO you're probably best off asking someone who's done it on a G car already or cloning the system off a later car.

In the older (twin version) system you simply have an over fill port out of the CC reservoir which has a blank cap over it. Not sure if this dumps to air or back into the cooling system like the newer version. The only way you're going to get that kinda pressure imo is if your pump is very powerful or it develops a blockage, can't circulate and the fluid boils.

It's an idea to have some kind of relief, if the fluid boils and there is no way to vent it could damage the tubes in the heat exhanger in the chargecooler, I dunno what they are rated at....or it'll just blow off one of your pipes

I'd try and copy someone who has done it before - at least it'd be tried and tested.

[Tentenths]

Didn't Steve (Unity1) fit one to his Turbo (yeah, okay it's an S car)?

[Paul C]

Great stuff guys - thanks

So... a pressure release cap may be an idea but just in case something goes wrong?

The header itself - do I take it that it doesn't really need an overflow in that case and simple "in and out" pipes will suffice and a capped hole in the top to initially fill it through!

It#s gonna kill Wayne seeing me reply to a Ch*rg*c**l*r thread...

My CC header level settles at about an inch below the cap.

This is because when the coolant gets warm it expands and then cools.

IF i fill it right to the top, it will expand when hot, blow out the

release cap and settle at about an inch below the cap again (where

it will stay).

Fit no release cap and what happens when the coolant expands?

You put the whole system under uneccesary pressure for the sake

of omitting a device that releases it.

Tighten up those hose clamps and run without... Why?

[Evil_Dr_Fish]

Those diagrams are really useful!

I think I prefer the idea of separate and independent circuits - otherwise CC temp would be heavily influenced by engine temp.

Plus it means I don't have to get in and mess with something that works just fine atm!

The second diagram is almost exactly what I had in my mind - except I would have gone and put the header tank 'in line' rather than parallell with the coolant flow.

Very useful to have seen - I will do it like this now instead

[Jonathan]

I think I prefer the idea of separate and independent circuits - otherwise CC temp would be heavily influenced by engine temp.

Actually it's doesn't, people think it's joined but touch the pipes and they're stone cold. The most influential part (apart from the compression of the air by the turbo) is where it is situated on the engine.

There is no or little flow from the header tank to the CC circuit at all - that connection pipe is simply to bleed air out of the CC system.

On freescan, the air temp might be 18c and the chargecooler never reaches above 26c in comparison to the engine which is at 80-90c.

Check out Dermot's site where he has gone to lengths to insulate the pipework and the chargecooler itself from the engine bay heat.

Plus it means I don't have to get in and mess with something that works just fine atm!

That's the best reason tbh...modifying mine to the single system caused a lot of headaches with the pump and where to fit it, water levels and so on.

The tank is in parallel to help eliminate air in the system, if the level goes down the header tank simply drops as well to accomodate the loss. The system is essentially closed loop where the tank acts as an accumulator or capacitor to fluctuations in exansion and pressure (just as it does in electronics).

Take that out into an open loop system and you introduce air bubbles and pump starting issues, it's tricky to explain without showing it but basically the pump gulps quicker than it pressurises on start and unless you have a very large header you'll get instant air lock as the pump is starved - some pumps wont even be able to deliver the pressure required to 'push only' the water around the circuit, it'll just sit there whirring....pumps rely on a vacuum + pressure partnership which allows a small pump to move large volumes of fluid quickly.

[Evil_Dr_Fish]

Useful stuff - thanks Jon

I'm deffo going to go down the separate route and at least the 'parallel' nature makes sense now (whereas I would have not thought about it and just lazily, copied the stock setup blindly! lol )

Working on the vaccum principle etc... I assume it makes more sense for me to fit a header with a one in and one out and use a pressure release cap rather than a header with an overflow pipe

[Jonathan]

Ya, tbh the volume in the circuit doen't change much at all, the thing Paul is talking about is probably the surge from the pump / pump pressure as opposed to any heat related expansion - remember they are mechanical RPM dependant pumps so they are variable flow/pressure as opposed to an electric one which is constant.

An interesting read is Dermot's site : http://www.lotusesprit.org/ (engine mods / chargecooler)

You can see what temperatures the system runs at and stuff Dermot's done.

I think you're best off copying the layout Lotus done for the SE turbo, the only prob is you wont be able to tell the functionality of the system easily - us lot with more technologically advanced cars (hehe ) have freescan and that can measure the MAT, I dunno about the G car.

You could install a temperature sender into the cabin from the Chargecooler MAT sender though without much hassle.

IMO it's always worth having a pressure relief, basially if the pump cocks out (I take it you're going for electric, so say the fuse goes) the fluid in the chargecooler will heat upto 80c + so you'll build pressure. Much better the car being able to vent in a controlled manner than shooting once of the hoses off and water spraying everywhere or hitting the cam belt or something else that moves.

Andy is the chaps name with a Silver (red decals) who has a chargecooler on his G car, he was at the rolling road day we done a year or so ago.

Can't remember his forum name.

[Evil_Dr_Fish]

Thanks Jon - Yeah You mean Ajay I have been pestering him with questions for some time!

[Jonathan]

Thats the chap.

[Drfatz]

I actually am in a similar situation. When I got my wrecked SE someone had removed the double header tank. Now since I have done a substantial amount of upgrades I decided to put on a MUCH larger charger cooler which basically has twice the capacity of the stock one. The problem is the chargecooler barley fits in to the engine bay with the hatch closed as is. There are bleed screws on the top of it and then water in/out lines. So my problem is even if I install a separate header tank for the CC system the CC will be the highest point in the system and I can't hook lines up to the bleed holes because there is no room. My thought was just to get rid of the header tank and connect the CC directly to the system. Then heat up the car and bleed the CC system with the bleed screws ( which can be accessed with the deck lid open) top off the coolant while the system is hot and then just let it be. This way when it cools down it will be under some pressure, but when it heats up the system will be full so it shouldn't need any more coolant. Also I have a 10psi safety valve installed just in case the pressure becomes to much when hot. Honestly if this doesn't work I am not sure what I am going to do. Thoughts?

-Graham

[Artie]

I actually am in a similar situation. When I got my wrecked SE someone had removed the double header tank. Now since I have done a substantial amount of upgrades I decided to put on a MUCH larger charger cooler which basically has twice the capacity of the stock one. The problem is the chargecooler barley fits in to the engine bay with the hatch closed as is. There are bleed screws on the top of it and then water in/out lines. So my problem is even if I install a separate header tank for the CC system the CC will be the highest point in the system and I can't hook lines up to the bleed holes because there is no room. My thought was just to get rid of the header tank and connect the CC directly to the system. Then heat up the car and bleed the CC system with the bleed screws ( which can be accessed with the deck lid open) top off the coolant while the system is hot and then just let it be. This way when it cools down it will be under some pressure, but when it heats up the system will be full so it shouldn't need any more coolant. Also I have a 10psi safety valve installed just in case the pressure becomes to much when hot. Honestly if this doesn't work I am not sure what I am going to do. Thoughts?

-Graham

Graham,

The chargecooler is the highest point in the system. It sits about 8" higher than the header tank. That's why it's such a pain to bleed and get working right once you drain it or refill.

Artie

[Drfatz]

Shouldn't the chargecooler have some kind of expansion tank then? I am just wondering why even have a header tank for the CC system. Why not just fill the CC, bleed it and be done with it.

-G

Graham,

The chargecooler is the highest point in the system. It sits about 8" higher than the header tank. That's why it's such a pain to bleed and get working right once you drain it or refill.

Artie

[Artie]

Shouldn't the chargecooler have some kind of expansion tank then? I am just wondering why even have a header tank for the CC system. Why not just fill the CC, bleed it and be done with it.

-G

It does have an expansion tank, that's what the header tank is for, since the temps in the cc system don't vary that much( in theory) so there' s not much need to expand and contract fluid. I put a lever vent cap on my CC header tank, this helps bleed any air out as the system operates, actually quite helpful!

Art

[Drfatz]

So then why not just fill up the CC system from the top of the CC and then bleed out all of the air from the CC and not bother with an expansion tank. I mean in theory the CC system should not heat up much and there is enough rubber line to expand and contact to keep the pressure from getting to high. I guess I really don't understand why bother with the CC header tank.

-Graham

[Artie]

So then why not just fill up the CC system from the top of the CC and then bleed out all of the air from the CC and not bother with an expansion tank. I mean in theory the CC system should not heat up much and there is enough rubber line to expand and contact to keep the pressure from getting to high. I guess I really don't understand why bother with the CC header tank.

-Graham

Problem is when you go to fill it you'll force an airpocket into the cc when you fill it and recap it. If there is an air pocket lower in the system, you'll never get it out. If you have a small header tank, you'll have a point in the system with a stopping point in the system to hold the air for expulsion. In reality the CC header tank doesn't need to be as big as it is! Maybe 4 or 6 ounces would suffice realistically. So long as there is a fill cap.

Artie

[Evil_Dr_Fish]

Am I right in thinking that besides looking nice, it doesn't *need* to be ally either? It could in theory (if mounted away from the turbo etc) be a plastic one?

(I do understand the physics however, of shiny, heat reflective surfaces in warm envrionments!)

[98GT3]

Am I right in thinking that besides looking nice, it doesn't *need* to be ally either? It could in theory (if mounted away from the turbo etc) be a plastic one?

(I do understand the physics however, of shiny, heat reflective surfaces in warm envrionments!)

Yep you're right, it can be plastic. The later ones - GT3 vintage are plastic and that is a combined tank with the engine.

Phil

98GT3

[Drfatz]

Problem is when you go to fill it you'll force an airpocket into the cc when you fill it and recap it. If there is an air pocket lower in the system, you'll never get it out. If you have a small header tank, you'll have a point in the system with a stopping point in the system to hold the air for expulsion. In reality the CC header tank doesn't need to be as big as it is! Maybe 4 or 6 ounces would suffice realistically. So long as there is a fill cap.

Artie

Hmmm...I guess the sticking point I have is I don't understand how you expell the air from the stock system if the header tank is lower then the CC. Simple physics says that if the CC is higher and you open up the header tank which is lower, the fluid will come out of the header tank. My situation is a little different since I have bleed screws at the highest point in the system. If the entire point of the header tank is to trap air in the system for expulsion then I guess I don't need one...maybe

-G

[Jonathan]

Fishy - here's something I came across my old fruit :

http://www.sm-engineering.co.uk/alloy_header_tank.php

Graham, in the later cars (shown as the single tank system in the drawings) they did away with this secondary tank for the CC.

There is not any significant expansion in the CC circuit (unless it's faulty) to cause any problems, I guess it was an attempt at keeping the 2 systems seperate.

With regards to airlocks - the issue probably arrises from weeping oil into the CC system (as you know it's driven off the end of the oil pump)...if you open a CC pump you'll see something like this after a few / 10 years :

This crap gets into the whole system and you'd be suprised at the pressure it builds up.

When re-filling that can cause an airlock as the water slowly screeps through the pipes in the cc radiator.

The idea is to fill it from the CC slowly and let it all flow through. My GT2 (1989) had this problem and it took DAYS to let the water level sink through the rad, so much so I never got to bleeding it fully - I have to remove it and inspect it for any permanent damage before mebbe fitting my spare. Thats why coolant changes are so critical to maintaining the system.

I've done the GT3 3 times since I've owned it (on seperate maintenance projects) and it bleeds 1st time in a few seconds, you might find any poop in the sytem is not overcome by the weaight of water ontop of it as you fill.

Look at the diagram carefully - the 2nd tank is NOT part of the circulation system, it's an overflow from the CC air bleed port.

If it expands fluid is dumped into the tank, as it contracts then fluid falls back into the system.