Would a De-Cat make your engine run cooler?

[Jimhughes]

Apologies if this is in the wrong section wasn't sure where to post and also if its a bit of a stupid question!
I had a decat pipe installed on my 1.8t A6 a few weeks ago and ever since I've noticed the temperature gauge never seems to go above 80 and seems to be mostly around the 75 degree mark when up to temperature where before it used to sit bang on 90.

I've had all the common 1.8t temp sensor/thermostat issues with it already and these have both been changed within the last 3 months so was just wondering if removing the Cat could in any way make my engine run that much cooler? I imagine it probably wouldn't and some more sensors etc are to blame but may as well ask!

[Jimhughes]

I also imagine I might get some stick for using a de-cat pipe but was done mainly for cost at present rather than just performance as my exhaust was blowing badly right near the Cat..Will be upgrading the whole system eventually when funds allow!

[OlberJ]

If the cat was blocked then removing the cat will free up exhaust gas flow and quite possibly cool the engine easier.

[Toltec]

Jimhughes said:

I also imagine I might get some stick for using a de-cat pipe but was done mainly for cost at present rather than just performance as my exhaust was blowing badly right near the Cat..Will be upgrading the whole system eventually when funds allow!

You should not get any negative responses on here, this is PH not Eco-Mums.

[mick_coupe]

Had my Harley De-Catted, it runs cooler !

Mick

[Ozzie Osmond]

Your radiator thermostat doesn't control engine temperature, it controls coolant temperature. If you drive your car around town or fit some cardboard across the radiator you should soon be able to find out if the system is capable of getting up to temperature and eliminate your decat question.

For engine temperature you need an oil temperature gauge. In your situation I'd get one fitted and see what it says, otherwise you're in the dark.

[Jimhughes]

Thanks for all the replies. Cheers Ozzie, thinking about it there is an oil temp sensor on the dash I will have a check later to see whats going on with that also after a run around town.

[Jimhughes]

mick_coupe said:

Had my Harley De-Catted, it runs cooler !

Mick

Cheers Mick also!

[graham22]

Is the cat in the down pipe on those? I know the 2.0T has a pre-cat in the down pipe as well as one under the car.

Would imagine one so close to the turbo would generate heat within the engine bay.

[anonymous-user]

NO.


(next question please)

[OlberJ]

How do you figure that MT?

Brand new cat v's de-cat i would agree but if it's clagged how is that not going to cause a back up of heat in the exhaust?

[GroundEffect]

Your engine wouldn't run as cleanly therefore wouldn't produce peak torque therefore wouldn't reject peak heat?

[Monty Python]

I'd imagine not, as the engine temperature is controlled by the cooling system and is designed to operate within set limits. If it's outside these limits then it'll adjust flow rates etc. to bring it back in. So, unless the valves/thermostats are faulty of there's a blockage somewhere, simply removing an external source of heat shouldn't make any difference - the system would simply reduce the amount of coolant going to the radiator.

[Oilchange]

How so?

GroundEffect said:

Your engine wouldn't run as cleanly therefore wouldn't produce peak torque therefore wouldn't reject peak heat?

[Devil2575]

Monty Python said:

I'd imagine not, as the engine temperature is controlled by the cooling system and is designed to operate within set limits. If it's outside these limits then it'll adjust flow rates etc. to bring it back in. So, unless the valves/thermostats are faulty of there's a blockage somewhere, simply removing an external source of heat shouldn't make any difference - the system would simply reduce the amount of coolant going to the radiator.

Are cooling systems that smart?

I've not worked on the system of a new car but on the cars I have the thermostat is either open or closed and the engine has quite a wide range of acceptable operating temperature.

[Art0ir]

A decat should mean lower EGTs and thus cooler turbocharger (on the hotside at least) which is good.

Can't imagine how it would affect coolant temps though.

[GroundEffect]

Devil2575 said:

Monty Python said:

I'd imagine not, as the engine temperature is controlled by the cooling system and is designed to operate within set limits. If it's outside these limits then it'll adjust flow rates etc. to bring it back in. So, unless the valves/thermostats are faulty of there's a blockage somewhere, simply removing an external source of heat shouldn't make any difference - the system would simply reduce the amount of coolant going to the radiator.

Are cooling systems that smart?

I've not worked on the system of a new car but on the cars I have the thermostat is either open or closed and the engine has quite a wide range of acceptable operating temperature.

No, the flow rate is determined by the water pump (in most cases driven by the FEAD) which is fixed to engine speeds. The only control is usually the thermostat which would open/close dependant on temperature alone.