Xu10J4Rs Race Engine - Thermostat Or No Thermostat ?

[lybker 26 2 Cars]

Having cooling issues in the past, i wonder now i have uprated my cooling capacity with a radiator that holds 4 x the capacity, does it make sense to remove the thermostat also and what would the pros/cons be by doing so?

 

Engine is a turboed gti6 engine

[welshpug 1,657]

Always run a thermostat, running too cold is not good for an engine

[allanallen 528 2 Cars]

4x tge capacity! Seems a bit extreme! Without a thermostat a correctly layed out cooling system of that size would never get warm.

[lybker 26 2 Cars]

It might be....just got tired of running hot, so sketched a new 100mm thick radiator i got constructed in China - hoping the issue is now gone. Reason for thinking about loosing the thermostat is because of the very speedy heat buildup especially on and around piston no 4, so i worry the blocked waterflow could lead to knock untill the thermo has fully opened and flow is sufficient. Alternativly i heard word of poor filling af woter in head and block if none is installed. Hence the need to ask the experts :-)

[petert 586]

Try a restrictor, ie remove the gizzards from a thermostat, to see what the limiting factor is.

[allanallen 528 2 Cars]

Which temp t/stat are you running currently and what sort of ambient temps are you in?

 

What car used to run drilled holes in the thermostat, was it the longman 306 engines?

[lybker 26 2 Cars]

Belive ambient enviroment is similar to typical uk (denmark) and I do not yet have enough track time in the car to evaluate enginetemp - during mapping on dyno it was typical 70 C without the thermostat fitted in a room with 15-20 C ambient.

[Sandy 191]

Panelling in a standard alloy rad I've found to be the most effective. Most of the aftermarket rads my customers have used, have looked chunkier, but don't cool as well. Forcing air to go through the rad, rather than around it, brings a big step forward in cooling.

I advise running a stat, but you need to use an 82/83C one, rather than OE 89C. Check there's sufficient restriction in the back loop (heater and bypass), add an 8mm hole restrictor if necessary; to ensure it's not too easy for coolant to flow that way, but you must have a back loop or drill a few 3mm holes around the outside of the stat, so coolant can circulate when the stat is closed, or the coolant can boil before the stat sees the heat!

The importance of running a stat is two fold, firstly, engines have optimum running temp for performance (and reliability/durability), which I've found to be almost always mid 80s on these on the engine dyno, where we can control and evaluate it. Secondly, although engine management obviously has compensation tables for coolant temp variations, no matter how good the calibration of these tables is, the optimised 3D map structure does not vary in a linear way with temp, as the tables do, so it's essential to keep the engine in a narrow temp operating band, to map it accurately initially, get the best from it in terms of perfromance/economy and as said, make it last.

[lybker 26 2 Cars]

excellent write up - exactly what I was asking for - thank you! :-)

 

Ensuring forced air through the RAD is essential - hence the new split with rad below and intercooler (on top of each other and not layered)

 

Burning the coolant was my worry, but ensuring minimum water flow by drilling holes until the point where thermostat opens makes sense. This I will do.

 

for the heater, I could install a flow reduction valve to avoid loosing efficiency if to much circulates this direction and not through the rad as intended.

[bobdylan_55 1]

I am running also a gti6 turbo and a 4x larger radiator and running at 32psi boost. On the rolling road it was peaking at 70 degrees C with no thermostat and then cooling to 60 C when on idle. I would say a thermostat is probably necessary unless you want to run at a constant 60-70 C which is probably not advisable.

[lybker 26 2 Cars]

this is similar to my experience- my boost level is up to 25psi of boost for now....32 is..... A lot :-)

 

I will go ahead and fit a thermostat including limited bypass to avoid potential boil af coolant as heat develops fast during acceleration