[robnitro]

Argh, on my TDI it was nice, you could block off the front lower grille to help warmup with no issues.

But the 35d gives me obd2 p code and a bmw code for IAT sensor. Of course, it's going to be 30 C without airflow and yes, outside was 5C or what not. But just annoying at how finnicky the BMW ecu is. Maybe I was spoiled with 2001 obd logic. It was also a hell of a lot easier to tune

I suppose I will open up the IC section and just deal with the wasted heat of super cooling the air, lol.

Still, worthwhile to cover up 1/2 or 2/3 the radiator. On the day we had 70 degree weather I forgot to remove the block and coolant never went above 95 C. Gasser BMWs normally run 100-105C, lol!

[floydarogers]

TDIWyse did a radiator block; search and you may perhaps find it (might have been on bimmerfest rather than here.)

Don't know why you want to cover the lower area - it's mainly the intercooler, not the radiator.

[335dsleeper]

IAT is in the MAF. Not sure why it'd throw a code for a restricted radiator. Are you positive that's the cause?

[Mark M]

The other year I used smoked plexi and silicone adhered to the back of the kidney grills. It did a good job blocking the radiator. However for my climate / use I never saw appreciable or quantifiable gains.

[robnitro]

The maf can't measure iat because that is pre turbo.
Iat is after the ic, before the throttle/egr.

I wanted to block the ic because of 2 things.
-Diesels are more efficient with warmer intake air, it also helps advance timing which also adds to efficiency.
-The intercooler not really being needed could be protected from snow/salt.

[335dsleeper]

Originally Posted by robnitro

The maf can't measure iat because that is pre turbo.
Iat is after the ic, before the throttle/egr.

I wanted to block the ic because of 2 things.
-Diesels are more efficient with warmer intake air, it also helps advance timing which also adds to efficiency.
-The intercooler not really being needed could be protected from snow/salt.

Warm air is never more efficient than cooler air. Cold air has more oxygen per volume than warm air, which makes more power for given air volume. Warm intake temperatures do not increase injector or in the case of a petrol engine ignition timing. Everything you've posted is incorrect.

This ONLY reason to block radiator airflow in cold climates is to allow the vehicle to get to operating temperature faster so your heat works sooner.

Your MAF and all BMW MAFs measure IAT. Charge air cooler temp sensor or CACT sensor is post intercooler and measures charge air temp. You also have an Outside air temperature sensor which again will not be effected by you blocking your radiator.

So, like I said before, you blocking your radiator isn't going to throw an IAT code.

[dmanb2b]

335dsleeper,

Not debating your statement, but trying to learn. I have seen this in my TDI and now with my 335D, MPG drops by roughly 10% in the winter?

I attributed that to longer engine warm-up period, which is the argument to run a top grill block.

[BB_cuda]

Dman, I thought the mileage drop off was more attributed to winter diesel.

[TDIwyse]

Originally Posted by floydarogers

TDIWyse did a radiator block; search and you may perhaps find it (might have been on bimmerfest rather than here.)

...

One version I used was here:
http://www.bimmerfest.com/forums/sho...d.php?t=594801

I'd make one cautionary comment regarding diesel engine thermal efficiency and air temp entering the cylinders... it can be fairly complicated interaction, and colder is not always better :-) One example: http://www.iaeng.org/publication/WCE...p1581-1585.pdf

"At low load, bsfc is increased as boost air temperature
increases. At part load, the bsfc is decreased as boost air
temperature increases. "

[Hoooper]

Originally Posted by 335dsleeper

So, like I said before, you blocking your radiator isn't going to throw an IAT code.

The code for what you refer to as charge air temp shows up as iat. If you block the intercooler off the charge air temp will be way higher than expected so it could certainly throw a plausibility code for that sensor.

[335dsleeper]

Originally Posted by BB_cuda

Dman, I thought the mileage drop off was more attributed to winter diesel.

It is

[lnxguy]

You guys get winter diesel in the US? I've always assumed that you didn't. If so, that will definitely account for the mileage loss.

[TDIwyse]

One other thing... If you just block the kidney grill openings, you also block the fresh air from going into the OEM intake openings which are behind and above the grill openings. This can have a significant impact on the air temp measured by the MAF, as it's pulling in air that is warmed up from the radiator and behind the block, and no longer has fresh air pushing/pressurizing that area. This increase in intake air temp can be very pronounced at low speeds and at stop lights.

The radiator block I use is slanted such that ambient air can still slide up the cover into the OEM intake openings, yet it blocks the air from hitting the radiator. Yes, it acts kind of like a "scoop". No, I don't measure any power benefits from the "scoop" :-)

[lnxguy]

Uh oh, TDIWyse 'Power Intake' inbound!!!

[dmanb2b]

Originally Posted by 335dsleeper

It is

OK, thanks guys. I'll have to check in some old threads over at that other diesel forum , but I'm not convinced that is the entire reason, although I do agree it is rationale for some of the overall MPG drop in winter months. I say this as I have a very regular 90 mile roundtrip daily commute with cruise set 90% of the trip. I also reset my avg fuel consumption daily, before I leave the house. Especially in the fall and spring, when daily avg temps can vary significantly in the north east, I have seen at least a 3-4mpg drop in both my TDI and now the 335D, when temps are closer to freezing vs. when temps are around 60-70 degrees...on the same tank of fuel. I have seen this in both my diesel powered vehicles as well as gas powered, although not as pronounced with gas powered as the engine itself is less efficient. Hence why I have always assumed it's a ambient temp thing. Forgot that winter diesel also contributes...that said...I treat the heck out of any diesel that goes in my cars.

I'll start a separate thread later today or tomorrow, so as not to take away from the OP's thread...unless this has been hashed out before...if so sorry I did not search

Sorry OP

[f00dstamps]

Originally Posted by 335dsleeper

Warm air is never more efficient than cooler air. Cold air has more oxygen per volume than warm air, which makes more power for given air volume. Warm intake temperatures do not increase injector or in the case of a petrol engine ignition timing. Everything you've posted is incorrect.

This ONLY reason to block radiator airflow in cold climates is to allow the vehicle to get to operating temperature faster so your heat works sooner.

Your MAF and all BMW MAFs measure IAT. Charge air cooler temp sensor or CACT sensor is post intercooler and measures charge air temp. You also have an Outside air temperature sensor which again will not be effected by you blocking your radiator.

So, like I said before, you blocking your radiator isn't going to throw an IAT code.

Do you have a suggestion for a good CACT to fit our application? Is the ideal spot to weld a bung in the hard pipe that is post intercooler and before the throttle body?

[335dsleeper]

Originally Posted by f00dstamps

Do you have a suggestion for a good CACT to fit our application? Is the ideal spot to weld a bung in the hard pipe that is post intercooler and before the throttle body?

That's where the oem sensor is. You could weld a bung there or just tap the intake manifold and thread in the sensor.

[robnitro]

Originally Posted by 335dsleeper

Warm air is never more efficient than cooler air. Cold air has more oxygen per volume than warm air, which makes more power for given air volume. Warm intake temperatures do not increase injector or in the case of a petrol engine ignition timing. Everything you've posted is incorrect.

This ONLY reason to block radiator airflow in cold climates is to allow the vehicle to get to operating temperature faster so your heat works sooner.

Your MAF and all BMW MAFs measure IAT. Charge air cooler temp sensor or CACT sensor is post intercooler and measures charge air temp. You also have an Outside air temperature sensor which again will not be effected by you blocking your radiator.

So, like I said before, you blocking your radiator isn't going to throw an IAT code.

Block was in front of the IC and up to middle of radiator. That's why IAT went up. I have it now covering the middle of radiator only and no codes tripped. I'm ok with not being able to block the IC, I just find it annoying at how sensitive the BMW ecu is. The battery low warning is another annoyance, some get it running ign off, radio on, even when they have a 6 amp charger attached!


Normally we are running excess air, unless WOT (even then, on stock tune it's conservative). Even on the cold days with the IC blocked, IAT was max 35 C, much lower than normal IAT temps on a hot summer day. So, I don't see how you can make more power from the same fuel with AFR above 20 on low to mid range throttle. Maybe if the ecu adjusted for less boost with the higher density, there would be less energy used by the turbo.
But then as we learned, the 35d engine doesn't run a maf based tune.
Not sure then what exactly happens, is the lambda that sensitive to request less boost for colder air, or is it a dumb lookup table?

Timing, sorry I wasn't clear. I meant effective timing.
Warm air does decrease ignition delay. Even if SOI is the same, the fuel and air mixture being hotter would start and finish burning earlier. On the TDI, there were maps that reduced timing as IAT and fuel temps went up for that reason (probably NOx concerns). I do see on other threads that IAT doesn't affect the 35d stock engine maps much at all. So if SOI is the same, but ignition delay decreased- it would act like an advance. EGR adds delay by the way. Some on ecuconnections who keep EGR can advance the timing more in that EGR active range and see similar economy to egr off. I did a few tests on my TDI but couldn't come up with a statistical difference on the few trips, so that's up in the air.