Hi fellow Jaguar enthusiasts,

Has anyone here done a modification to isolate the main engine and supercharger cooling systems? I haven't been able to find a thread on the subject on this forum.

I think having hot engine coolant (~190 F) running through the charge-air coolers is not the most effective approach, and is a large contributor to heat soak in our cars. I also think this modification goes hand in hand with upgrading the SC coolant pump. There is Youtube video showing an elegant solution to this problem with quite impressive results, and I am wondering if anyone here has made this modification. If not, I plan on doing it soon, and will document it on this site if there is interest.

 

There is only one point where the cooling systems connect.(besides the air bleeds)
A small hose between the return paths allows the two systems to share the reservoir.

I suppose a little heat might be transferred but they are mostly separate.

The lower left in the diagram shows the connection pipe.

 

thank you for your quick reply, @motorcarman. Sorry, I am sure I am mistaken, but doesn't the system also share a connection here:


There might be a check valve located in that junction...

 

That's the line he was referring to, that connects the return lines. It connects the cooled side of each radiator to equalize pressure between the two systems, although looking at it, I'd be surprised if there was a significant amount of exchange between the two systems.

The issue you're trying to address is not actually an issue in my mind. So-called "heat soak" is coolant heating up when the car shuts down. That coolant is being heated by removing heat from the engine, which is a Good Thing. Coolant temperature goes up, but the mechanical components are being cooled by that action. "heat soak" affect coolant, not mechanicals.

I see a lot of folks, after running the car hard, letting the car sit and idle for several minutes until the coolant temp settles down. The best way to let temps settle down is to stop generating heat, i.e. shut the thing off! Keep in mind that coolant temperature is not the same as engine core temperature. The coolant gets hot by removing heat from the engine, which is harder to do if you let it keep burning fuel.

As for hot coolant affecting the SC air exchange, keep in mind that the only connection between the two system is on the cooled side of the radiators, and serves for pressure equalization between the systems rather than actual fluid interchange. If you want to build a completely separate SC cooling loop, you'll have to add another expansion tank with a pressure cap, at least, although I'm not sure you'd actually need a thermostat in that loop. I wouldn't think that expansion tank would need to be pressurized, you might get away with a pressure cap allowing expansion into an atmospheric-pressure expansion tank, which would suck the coolant back in as it cools.

I think you're addressing a non-issue.

 

This illustration has a little more detail and may or may be more accurate as the SC coolant supply from the engine side comes from the heater return:


Green is cold side SC cooling system and orange is hot side SC cooling system. The return side of the heater circuit looks to be directly connected to the SC radiator, but not inline with the SC coolant pump (14). The purple connection is to the reservoir/expansion tank (10). I suspect that there is a one-way valve where the connection is made, circled in blue. If this is the case, there should be no mixing of hot engine coolant and the SC cooling fluid. Does anyone know if this is the case?

 

Thanks @wfooshee for your input. For me, the biggest source of heat soak is when parking the car after a drive, be it short or long. The charge-air coolers are connected directly to the heads, albeit isolated by intake gaskets, and when parked after a drive, are heated up by the engine block. This heats the tanks to running temp, thereby heating the coolant, approaching 190 F. It is highly noticeable, even after a short drive to the store on a hot day. If the systems are mostly isolated, then a high flow pump accompanied by a fan that runs when driving at low speeds/idle (traffic conditions) will, at least in part, mitigate this issue. Also, running the pump and fan for a brief period after shutoff will also reduce this problem. If the systems are not mostly isolated, then this will also need addressed to help with this problem. Of course, I might be completely wrong about this whole matter :-)

 

Yes a better pump can help and a bigger IC is also a help.
As posted above the system share a common bleed port. People have built completely isolated systems but it's a lot of expense and not really any documented power gains.

The biggest problem is your engine has the old "Heaton" M112 blower. It's called a Heaton instead of an Eaton for a reason.
Are you planning to change the pulley?
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■ look for Joel Brown ( usa). He is doing research and developping cooling system ,seperate charge cooler on
fb modified jaguar site.
If I find it i'll post it here
■ Scott Holford (Gb) hugely modified xjr jaguar x350/ x358 admirers and owners also Fb

 

Here is one link.
https://www.facebook.com/share/p/16HM5oshwu/

 

Here is one link.
https://www.facebook.com/share/p/16HM5oshwu/

 

Thanks @clubairth1 , I do plan to eventually install a smaller pulley. However, TBH, I am extremely happy with the performance when the engine is cold, it's just not great when I'm making stops or stuck in traffic, which is sometimes often (if that makes sense). On a warm day here, when driving about town, my SC-engine doesn't really feel much quicker, if at all, than the my NA engine, though I do not have any empirical data to compare. I'll probably do some tests with a thermocouple and maybe some smartphone 0-60 measurements make this more scientific, before I begin any work.

 

@Petz , thank you, I'll check these out!

 

I should also add, that if I undertake this project I will be sure to collect some data first and post them here. Also, as I envision it, it should (possibly) be a relatively cheap project involving only several parts and rerouting the factory hoses. We shall see...

 

Its very noticable how much quicker the car gets when its colder outside so no doubt that cooling will help. Im following this thread.

 

Here is a relevant thread relating to heat soak in the AJV8 by @34by151 and a brilliant solution.

 

I agree when the temperatures drop look out! That SC just LOVES it when it's cold out.
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