Back story; I'm in the process of rebuilding my GC8 track car. I've got a forged 2.1 stroker and SC42+ turbo ready to go in and I'd like to reverse the inlet manifold this time around (obv its fitted with FMIC too)

By reversing the inlet, the stock header tank doesn't really suit the job anymore and that's got me thinking...
The hot water from the turbo feeds directly into the header tank from where it can go straight back to the water pump and not be cooled by the radiator.
That's helpful for a road car to warm up more quickly while the thermostat is closed, but I'm more concerned about maximising cooling efficiency.

So, what do you guys think about taking the turbo coolant outlet and t'ing into the top radiator hose?
Hopefully my diagram shows everything I'm taking about.

 

Has nobody made any alterations to their cooling system then? I can't be alone?!

 

Yes lots of people was going to answer yesterday but about the only useful thing you have done there with no disrespect is number one.

 

No worries, I'm here for any and all thoughts and opinions. Appreciate the input.


For what its worth I’ll go through my reasoning on the changes, in case anyone finds this thread in the future while looking for info. (Sorry for the long post!)

Not to say I’m definitely right. This is my opinion on things (as a mechanical engineer)

1. Throttle body heater is to prevent it from icing up in cold climates. Not an issue on a track car that doesn’t get used in winter. It would only soak heat into the inlet track and undo work done by the intercooler.

1. Cylinder 4 coolant bypass. Its proven that cylinder 4 runs hotter than the other 3* (linked to common misfire and lean running problems) The coolant flow through that head does have a bit of a dead end loop behind cyl 4** and I agree with other people opinions that is the reason for it running hotter.

I’m actually undecided whether water will flow in through or out off the bypass. But either way, it solves the dead end and will improve overall flow around cyl 4.

1. Taking off the Modine is 50% for packaging reasons and 50% about cooling.

Its job is to help warm oil up when the engine is cold or help cool the oil if it gets very hot. But its not designed for prolonged track use, where the oil is often 115-120° and just dumps too much heat into the water.

An external air to oil cooler is better for cooling the oil and won’t heat up the water. I'll just have to wait a little longer for oil to warm up before use.

It is possible to have the Modine and an external oil cooler (I’ve tried it) but with the modine fitted the thermostatic sandwich plate for the oil cooler take off and the oil lines sit pretty low down and very close to the headers. Which obviously means the oil lines get radiantly heated by the exhaust and it make routing them safely more difficult.

1. This idea occurred to me a few days ago and I’ve not really done much research on it yet (hence this thread)

What I need to understand is the pressures and flow of the top radiator hose and the turbo line. If the relative pressures aren’t right then it could easily prevent proper coolant flow through the turbo.

I wish I had time to rig up my old engine on a stand so I can do some static testing.


* https://www.blingstrom.com/modmonday...you-still-care
** This guys video describes the engine coolant pathways very well

 

 

Have a look at this mate

https://www.scoobynet.com/general-te...ispreloading=1

 

The way I see it with the to do/not do the cylinder 4 cooling mod is this, yes you will get more even temps, yes you will get less knock readings with the knock sensor being above that cylinder which is now slightly cooler and able to add a bit more timing or whatever BUT, you've just screwed your early warning system right up.
Yes that cylinder runs hotter but it runs hotter for a reason, the knock sensor is on cylinder 4 so with that running slightly hotter if knock is detected it can dial back timing before damage is done to it or the cooler cylinders, remember the knock sensor is above cylinder 4 not 1,2 or 3 so if you even out temps, the knock sensor detects knock above cylinder 4 and dials it back, but cylinder 4 is now the same temperature as cylinder 1 which it can't detect knock on as well and has actually been knocking for 10 miles because what the system is expecting is cylinder 4 to be the hottest and the one it bases other factors on.

​​​​​I know the guy that created the mod did a load of thermal testing and it shows cooler temps but did he take into account how the ecu uses the information its sensors provide and the assumptions subaru expect when calculating timing etc. , I genuinely don't know but I doubt it. Now if you move the knock sensor to the new hottest cylinder or run multiple knock sensors (assuming there's even a mount point over all other cylinders for a sensor, I haven't checked myself) probably a worth while mod but on its own I wouldn't personally

 

You are 100% correct Sir just I don't type. The cooling mode is in my opinion and alot of others is a backward step doing away with a failsafe way of monitoring the engine.