Good evening!
As some of you might know I've started electronically modifying my SLK.
I've read a few topics about the pre-facelift model that the car already pulls timing at 35 degrees celcius intake air temperature, and also a few topics where people put a resistor in line with the IAT signal wire from the MAF to make the car believe the intake is a bit cooler.
I didn't know if this applied to the facelift model, so I started testing.
My testing method:
Do 4000 to 5000rpm pulls in third gear and log both IAT and timing advance.
Seems it does apply to this car.
What I noticed:
When intake air temperature is below 35 degrees, you get about 16 degrees of timing advance. After a few pulls, the intake air temperature raises to about 40 degrees. At this point, there is 14 degrees of advance. So it looks like the ECU pulls about 2 degrees of timing when the intake air temperature climbs around 40 degrees.
40 degrees is really easy to hit, and from my experience with tuning very premature to start pulling timing. If it's even remotely warm outside you'll reach 40 to 45 degrees very quickly with a pulley'd car.
I then tried the resistor mod some people talked about, but it looks like that doesn't work on the facelift model. If you put a resistor in-line, any resistor at all, the ECU ignores the IAT sensor's value and uses a default value of 50 degrees celcius.
I feel like this loss of timing is very noticeable, the car gets noticeably more sluggish after continued spirited driving.
I'd like to know from some people more seasoned tuners on this car, is this a common and known problem? How do people usually get around this?
As some of you might know I've started electronically modifying my SLK.
I've read a few topics about the pre-facelift model that the car already pulls timing at 35 degrees celcius intake air temperature, and also a few topics where people put a resistor in line with the IAT signal wire from the MAF to make the car believe the intake is a bit cooler.
I didn't know if this applied to the facelift model, so I started testing.
My testing method:
Do 4000 to 5000rpm pulls in third gear and log both IAT and timing advance.
Seems it does apply to this car.
What I noticed:
When intake air temperature is below 35 degrees, you get about 16 degrees of timing advance. After a few pulls, the intake air temperature raises to about 40 degrees. At this point, there is 14 degrees of advance. So it looks like the ECU pulls about 2 degrees of timing when the intake air temperature climbs around 40 degrees.
40 degrees is really easy to hit, and from my experience with tuning very premature to start pulling timing. If it's even remotely warm outside you'll reach 40 to 45 degrees very quickly with a pulley'd car.
I then tried the resistor mod some people talked about, but it looks like that doesn't work on the facelift model. If you put a resistor in-line, any resistor at all, the ECU ignores the IAT sensor's value and uses a default value of 50 degrees celcius.
I feel like this loss of timing is very noticeable, the car gets noticeably more sluggish after continued spirited driving.
I'd like to know from some people more seasoned tuners on this car, is this a common and known problem? How do people usually get around this?
