Hi all,
This is a new member from Finland and I thought to share some thoughts and experiences about my Megane II 1.5dCi, which I´ve had for quite some time now.
Problem from the beginning was that car has always felt very lazy with flat spots in torque and underpowered in general. I knew that 60kw diesel in Megane sized body is not going to be any rocket, but this bad?
I started to google around and first job was to disable EGR by turning it around 180 degrees and it helped a bit to the responsiveness, but the power was still quite lame. Got the OBD reader, but no error codes so everything is supposed to work as it should.
Next thought was, how about these tuning boxes. I know they are total waste of money with gasoline engines, but in turbodiesels they can actually work.
I know they are just a few cent resistor in a nice box, fooling ECU to see lower pressure in the rail, thus increasing the pressure. But for 60e you get all in a nice sealed box with plug and play connectors and everything, so it was not worth starting to build one myself.
This actually helped quite a lot and I was driving around happily for awhile. The mpg readings were showing really optimistic figures because ECU had no idea about the real amount of stuff going through the injectors. I didn´t care about it, I thought I still have the fuel needle to show how much fuel i have in the tank. At least so I thought until I was left in the roadside with empty tank, needle still showing 1/4 tank. Is it possible that that the fuel gauge is using ECU information to show the amount of fuel instead of the traditional sensor inside of the tank? Over time the error accumulates, until you run out of fuel. Apparently this is the case in 2005 Megane, since I removed the box right away and no problems with mpg or fuel readings since! Similar experiences, anyone?
Back in the square two, so I recently started to play around with the OBD reader and different monitoring software to see if there is something odd in the readings, is the turbo working ok etc.
I immediately noticed that IAT was showing +140C and the puzzle pieces suddenly fit together. Of course, if the ECU thinks you are driving in the Finnish sauna, you are not going to need very much fuel in that hot thin air. And in diesel engines amount of fuel = hp. The IAT sensor actually was shorted and Bosch technical specs confirmed that the reading is then somewhere around +130C. Strange thing is that I have never had a single error code about IAT sensor!?
Since the new sensor costs an arm and leg in the dealer, I wanted to first confirm that this is the source of my problems and thought to put a resistor between the sensor and ECU to see if I get lower temp readings and maybe better performance.
Hey wait! If my theory is right, what do I need the new sensor for? I have then manufactured a IAT modding tuning box which are sold in ebay.
Fortunately the 60kW K9K-722 is one of the few engines that don´t have MAF at all, which to my understanding might complicate things in some cases.
As a bonus, this mod is not going to mess up with fuel, so ECU will remain in control and mpg and fuel readings shouldn´t be affected.
I already made a small adapter with 5kohm resistor which I found laying around and I am going to test it this weekend. Let you know about the results.