[robnitro]

I recently installed a 2 gps coolant heater, similar to what the tdi manuals have near the oil/water cooler. It runs until about 65C coolant temp using 2 temperature switches (nc) in series with the relay coil control and a low voltage cutoff in series to not power them below 13v (so they don't come on with engine off). They do about 550w at 14.5 volts-18a each plug-36a total, no problem for our 180a alternator and no codes. It helps speed up warmup especially on light driving.

I also made it plug in, approxinately 400w with a 12v psu on a timer.

It's nice to start up with coolant at 35c for 2 hours of heating.

But this bmw ecu is so obsessive compulsive. Because coolant was at 35 C and intake air was 0 C, the ecu gives an obd code. 7b. For map temperature sensor (iat)

Is there some kind of coding that I can do to eliminate this excessive wrong checking with iat?

I also had the same problem when I blocked off the intercooler to help keep iat warm, which gives better combustion in cold weather. It's just ridiculous, the tdi didn't complain so much unless the sensor was consistently wrong.

Meanwhile with bmw, we have overly sensitive iat, battery and other stupid codes that don't actually mean there is a problem. It seems like they built it to be dealer service friendly, lol.

[nicklockard]

Originally Posted by robnitro

It seems like they built it to be dealer service friendly, lol.

Nailed it.

[robnitro]

What's funny is there is coding to stop the bulb checking and so on. So much extra stuff that seems nice but causes headaches (as I have seen with trailer wiring blowing out things etc)

[nicklockard]

I'm convinced they do crap like this to intimidate people into not wanting to even try working on their own cars.

[robnitro]

Cleared those codes, and second day got codes again. 7b for the map sensor, and some code for egr flow. LOL. Yeah, umm cause my heater heats the coolant, including the egr cooler. Sheesh, what a picky fickle ecu!

Just to confirm that this issue is not a sensor, I did 2 days straight of no pre warming. No codes.

[lnxguy]

I'm wondering if you could code these out.

[nwsnowboarder]

Originally Posted by robnitro

I also had the same problem when I blocked off the intercooler to help keep iat warm, which gives better combustion in cold weather.

100% contrarian to my experience. I have owned 6 different diesels in the last 32 years. In cold, dry air diesels always perform much better due to a greater concentration of oxygen molecules/volume of air. The purpose of the intercooler is to lower iat, thereby increasing the concentration of oxygen resulting in a cleaner, more efficient burn.

Blocking off the radiator on the other hand, will get and keep the engine up to operating temperature in a cold weather environment.

[robnitro]

Originally Posted by nwsnowboarder

100% contrarian to my experience. I have owned 6 different diesels in the last 32 years. In cold, dry air diesels always perform much better due to a greater concentration of oxygen molecules/volume of air. The purpose of the intercooler is to lower iat, thereby increasing the concentration of oxygen resulting in a cleaner, more efficient burn.

Blocking off the radiator on the other hand, will get and keep the engine up to operating temperature in a cold weather environment.

Yes, that is true if you are running rich and need more air. The IC still cools off my intake charge a lot even with most of it blocked off because the pre turbo air is so cold. It's designed to cool down 80+ C air, so when it is around 0 C, theres much less work for it to do!

On the 35d engine which runs excessively lean even on a hot summer day. 29+ afr is typical. Meanwhile, in papers about child weather diesel combustion, colder air introduces more ignition delay and less mixing.

Another example of why the 35d doesn't benefit from cold air (besides full throttle):
Egr rate is determined by an expected maf flow.
I'll use the measurement of mg/str as the tdi vcds uses and I have adapted into torque custom pid.
Light load, it wants to see 320 mg/str, where no egr is 500 mg/str.

Remember maf reads mass air flow. So if you have same velocity, but the air is 10% more dense, it will read 10% higher - cold air for example.

With warm air, to get 320 you might need around 45% egr, to dilute the oxygen/mass airflow.
With very cold air that has 10% or more density, you need 55% egr rate to get the same 320 mg/str request.
The request airflow is also throttled during warm up and regen, but the point is that with our stock tuning, egr request sets the air the engine will see. Colder air, more egr, warmer air, less egr to get the same target maf reading.

At WOT you can see improvements, but I doubt it on the stock tuning which is very conservative to not soot up the DPF. If you do fueling mods or a retune, yes it will help to have colder air.