07-11-2015, 10:33 AM
Hi guys, I have just been reading info about cold air intakes etc and how intake temperatures affect a diesel.
I am curious as to how these engines know what the intake temperature is. I know that the MAF sensor has a temperature probe in it which is used to determine density of the intake air. It is also used to advance or retard the injection timing to allow the engine to compensate for the slower burn with cold air and faster burn with hot air.
Here is the bit that confuses me though. These engines originally don't have an intercooler. Is there some generic setting somewhere that says that the turbo at max boost will always increase the intake air temperature by a certain amount.
For example,
15c + (generic turbo temperature increase) = 65c intake manifold temperature. = Injection 12* before top dead centre
24c + (generic turbo temperature increase) = 74c intake manifold temperature. = Injection 8* before top dead centre
(I have no idea actual injection starts just showing an example)
Now imagine then that you throw an intercooler into the mix. You still only have that MAF sensor reading, and then the generic turbo temperature rise setting in the ECU.
15c + (generic turbo temperature increase) = 65c before intercooler temperature = Injection 12* before top dead centre.
But then if you say measured the temperature after the intercooler and it was say 22c.
65c - 22c = 43c difference between what the ECU thinks is entering the engine and what actually is entering the engine.
Then you could get away with more timing advance than what the ECU thinks is actually required? Meaning you could have better fuel burn, higher cylinder pressure, better mpg from the same amount of fuel but just injected earlier than the car though it could be?
What are your thoughts guys? Would it be possible to have a temperature probe like the one in the maf and get it fitted into the entrance to the manifold to then map the car suiting the actual temperature of the intake temps?
Jack
I am curious as to how these engines know what the intake temperature is. I know that the MAF sensor has a temperature probe in it which is used to determine density of the intake air. It is also used to advance or retard the injection timing to allow the engine to compensate for the slower burn with cold air and faster burn with hot air.
Here is the bit that confuses me though. These engines originally don't have an intercooler. Is there some generic setting somewhere that says that the turbo at max boost will always increase the intake air temperature by a certain amount.
For example,
15c + (generic turbo temperature increase) = 65c intake manifold temperature. = Injection 12* before top dead centre
24c + (generic turbo temperature increase) = 74c intake manifold temperature. = Injection 8* before top dead centre
(I have no idea actual injection starts just showing an example)
Now imagine then that you throw an intercooler into the mix. You still only have that MAF sensor reading, and then the generic turbo temperature rise setting in the ECU.
15c + (generic turbo temperature increase) = 65c before intercooler temperature = Injection 12* before top dead centre.
But then if you say measured the temperature after the intercooler and it was say 22c.
65c - 22c = 43c difference between what the ECU thinks is entering the engine and what actually is entering the engine.
Then you could get away with more timing advance than what the ECU thinks is actually required? Meaning you could have better fuel burn, higher cylinder pressure, better mpg from the same amount of fuel but just injected earlier than the car though it could be?
What are your thoughts guys? Would it be possible to have a temperature probe like the one in the maf and get it fitted into the entrance to the manifold to then map the car suiting the actual temperature of the intake temps?
Jack
