N52 Swap Discussion

[hoveringuy]

I received my Plan B in the mail today. (maybe that didn't come out right?)

Anyway, I received my Mercedes aux pump. It fits into my coffee mug and pumps a measured 1600 liters/hr. Dead silent.

Here's the mind-blowing part. 1600 litres per hour is 23% of 7000 litres per hour, or the main coolant pump running at 23%. So, 2000 liters per hour will cover this pump and plenty for flow through the radiator.

It probably won't go in the car but the Koi love it!

[hubcapboy]

Looked into the heat situation and I think the solution is pretty simple (at least as far as work-arounds go).

This is outstanding. I just walked over to my harness and clipped out the relay for the aux pump. I'm not stressed out about having the pump idle at 35%; these cars were sold and run in the desert... The duty cycle of that pump isn't a concern. The only compromise to the original design is potentially we'd be sucking enough heat out of the engine that it wouldn't be able to reach it's "super hot" eco operation temperature, which I'm completely fine with.

I've been physically modifying my Z4 harness to incorporate the oil level sensor, tesla booster power, gauge temp sensor, tap the oil pressure switch, add the C101, incorporate the Z4 IVM, add a sport button, an L-Can connection for an OBD reader (TBD if that works), an OBD plug, the accelerator cable, and a dash cable that will carry the cruise control wire, brake pedal switch, clutch switch, tach, wheel speed, and econometer signals between the DME and drivers side. I've also lengthened all the connections on the intake side using a spare X3 harness so that the DME can reach the glove box.

Most of that has been discussed, but the instrument cluster temperature gauge has some new developments. hoveringuy is happily using his original e30 temp sensor in a new bung on the oil filter housing to drive the gauge, and it seems to be indicating for him perfectly. An easier way of doing this is to put a sensor housing in-line with a hose. For some reason I'm not really thrilled about either of these, and after figuring out that my e36 dual temp sensor wasn't going to work in the last 24 hours (it's a four plug sensor with the correct thermistor for the ECU and a second sensor for the gauge... but the resistance values are wrong... I thought I could correct them but it can't be done passively) I've gone in a completely different direction which may or may not work out.

We can get numerical coolant temperature from the DME, and the DME is constantly doing weird stuff with coolant as we found out with the heating issue and the fan switch vs thermostat feedback loop. Watching that needle jump up and down as the DME makes different decisions about what to do with the coolant is as uninformative as using the charge light to indicate if the N52 alternator is charging... Every time you put your foot down, the DME turns off the alternator, and it would look like a fault on the dash.

Instead of measuring coolant level, I'm going to try and use the sensor to measure Head temperature. Garageaholic has a video where he measures the temp gauge's response to different resistances, and his profile of the gauge looks like this:

Gauge Position	Indicated at
	Ohms
End	325
Blue Start	122
Low Line	70
mid	42
High Line	31
Red Start	22
End	14

Through a lot of poking around, The 1k model of this thermistor:

https://www.tdk-electronics.tdk.com/...be_ass_K45.pdf


will present 87 Ohms at 98.6 degrees, which is right around where I think I want the middle of the gauge to be. Using fixed resistance to adjust that creates the same problem I was having in correcting the e36 sender... That since the resistance you're adding is fixed and the sensor is logarithmic, you only see your fixed resistance for a large part of the scale. Using two of these thermistors connected in parallel does two things... It lets you sample (and electronically average) two locations, and it brings the resistance at 98.6 down to 43.5 Ohms... which will read just a little below center on the gauge. Here's the whole table of temperatures I expect to indicate at the different points of the gauge:

Gauge Position	Indicated at	Temp C
	Ohms	2 in ||
End	325	35.6
Blue Start	122	62.9
Low Line	70	80.6
mid	42	98.6
High Line	31	110
Red Start	22	124
End	14	144

I haven't tracked down a good spot to fix the M3 studs, but probably one towards the front of the head and one towards the back.. This will give the actual head temperature (not the coolant temperature, which is a stand-in for that) and won't jump around as thermostats open and close and electric pumps decide to change speed. Even if it doesn't read dead center at operating speed, it'll be good feedback on engine temperature.

[nando]

Looked into the heat situation and I think the solution is pretty simple (at least as far as work-arounds go). No external pump is needed, indeed that would be silly as the waterpump can flow regardless of if the engine is on or off (N52 cars even have an HVAC button specifically for this). I haven't looked but I sort of doubt that E60s with the N52 have a separate pump just for that when the stock N52 pump can already do this.

I took screenshots of the pump operation in 3 states - at idle with the heater at full blast, the heater off, and also with the engine off and the heater on max (REST). That should tell me the typical states of the waterpump operation regarding heater controls.

here's the heat turned off - minimum pump speed is 15% at idle:


here's the heat set to max (84 degrees) - pump speed is at 76%:


Here's with the engine off, and the heater at max (REST) - pump speed is 35%:


Now, the pump is controlled with thermal load. There's not really a map, but a set of constants
(K_EWP_*). the DME uses demand to decide how much to operate the pump on the fly. All are in units of liters/hour - the N52 pump has a maximum capacity of 7000l/hr:


Suffixes:
MN = min - the minimum pump flow with the engine warmed up.
MX = max - the maximum pump flow
WA = warmup flow rate. Notice the pump is turned off entirely during warm up. This helps to warm up the engine faster.
MN1 = This is the min pump flow at start with an already warmed up engine. We probably don't care about this, it's just designed to get the coolant flowing until the engine is in a "normal" state (there can be hot pockets when you turn off a hot engine etc).
AP = it's not actually clear from the code or the description - but I think this is the base flow rate for using the REST position

So basically, I think if we increase the K_EWP_MN to about 2000l/h, that should give us about the minimum speed needed to run the heater. This is a workaround without needing CAN inputs of course - and it would be easy enough to switch this value back to stock for a "summer" tune.

Also I found this interesting - this is the map for running the pump while bleeding the coolant system:



The Y axis is pump flow and the X axis is time (not sure of the exact units, probably CPU cycles or something). If you've ever bled an n52 engine before, this graph will make a lot of sense..

[nando]

There probably is a CAN message from the HVAC system to tell it when you're heating the car. There must be a way to force it to flow a minimum amount of coolant or some other way to tell it you're using the heater. I have never looked at that because nobody has ever mentioned an issue with heat, but it seems pretty important!

On the N52, it uses the electric pump itself to heat the cabin with the engine off (the "rest" function). We have full control over the DME, so I don't see why it couldn't be made to work.

[Caperix]

The bigger cars, use a aux water pump to help circulate coolant, even the e60 with a n52 has one off the upper radiator hose. It is adding a potential failure point, though most just drip when they leak. Are you using a can translator board? You would need to find what code the ihka sends to the dme but it should be doable. I know m54 z4's were available with the low ihkr HVAC system in the us, I don't know if that continued to the n52 cars but it should have much less communication involved.

[hubcapboy]

Mercedes uses the aux pump to circulate coolant and provide heat when the engine is off but still warm.

[hubcapboy]

Huh look, the Mercedes SL heater control valve I bought to experiment with relocating the valve to under the hood has an aux pump attached to it:

[hoveringuy]

I haven't had cabin heat up until now and was getting tired of cold feet, so I finally plumbed it up. Some things are different on the N52, but the primary cooling loop is basically the same. Hot coolant leaves the engine, flows through the radiator, is metered by the thermostat and then pumped back into the engine. I fabricated a small manifold to tap the engine outflow and send it to the bottom pipe of the heater core.

It absolutely sucks!

No warm air even when at operating temp at idle. I did get a small amount of hot air when I did some driving. What's going on?

As an experiment I triggered the coolant pump to 95% through INPA once I was back in the garage and got a plethora, a veritable gusher of hot air. Like, a lot!

So, I think what's happening is that the engine doesn't know that I'm trying to make heat and runs the coolant pump at low speed which isn't pushing anything through the heater core. Need either 1) an aux heater circuit circulation pump or 2) a way to tell the ECU to ramp up pump speed for heat.

[hoveringuy]

My fuel pressure was 6 psi short of 5bar, and my stock fuel pump was very noisy, so I installed a new Douchewerks DW200 with the 9-1031 install kit. This is supposed to flow 210 liters per hour at 5bar while drawing 11 amps.

For the install you're supposed to just use a hose clamp to attach it to the support rod, but I didn't think that was secure enough and added a bracket, because I love brackets. I also didn't use the supplied accordion flex line and used fuel line instead. My other hints are that the pickup was hitting the bottom of the tank if I lowered the pump all the way to the bottom, and the position of the clamp is important so that it doesn't hit the fuel transfer tube inside the tank. The filter sock was clocked to the correct position for the tank, however.

It's quieter than my stock pump and boosted the rail pressure.

[hoveringuy]

Let's talk about my weight.

Just crossed the scales at 2460lbs, with a full tank of gas and the almost exact configuration I had with the M54. That's a 23# reduction from M54 to N52. Some other things that changed are aluminum X3 brake booster (-6lbs) and 5" rear springs (-2lbs), so the N52 is around 15lbs lighter than the M54 which includes a 6speed transmission, dual-mass flywheel over the G260 single, and dope S54 headers over the OBD2 manifolds. (plus I have beefy steel engine mount arms, a steel oil pan that can double as a skid plate, and hydraulic engine mounts.)

Replacing my passenger seat with a Sparco, deleting rear interior (because I won't be able to get people back there, anyway...) and maybe a CF hood would easily get me below 2400.

[hoveringuy]

If you are eliminating the mass air flow meter, I would just pull the pins out of the harness for the intake air temp instead of spending $124 on that cable. I looks like it is a obd 1 e36 intake temp sensor they are using.

Yeah, pretty much exactly. We've ordered the $12 sensors and we'll just extend the wiring ourselves with the super-common 2 pin plug.

I would never, ever suspect that I don't have a MAF, it runs smoothly throughout.

[Caperix]

If you are eliminating the mass air flow meter, I would just pull the pins out of the harness for the intake air temp instead of spending $124 on that cable. I looks like it is a obd 1 e36 intake temp sensor they are using.

[Caperix]

The design of the mass air flow meter changed with the n52k motor & msv80 dme. BMW documentation says they went from an analog to digital air flow meter. I believe this is also when they fazed out the mass air flow meter for euro markets. That is likely the difference you are seeing in the wiring diagrams.

[hubcapboy]

Converting from MAF to euro IAT to reduce intake restriction, or is there something else I'm not aware of?

I believe that some people convert from MAF to euro IAT to incorporate what they think is a less restrictive (complete) euro intake. The rumor from nando is that the MAF operation isn't optimal anyway, and he doesn't include it in his tune (he can correct me, but that component of operation in his flashes must be based on the euro air box/euro IAT).

Since the swap flash will never read the MAF anyway, using an equivalent IAT sensor in a better location is preferable to accommodating either the euro IAT *or* the combo MAF. I don't have an airbox with the correct mounting for either of these sensors, so my celebration here is that rather than use an aftermarket pipe that accommodates a MAF like this:



I can just locate an intake air sensor anywhere that's convenient, like this:

[Bored]

This ECU fan control pleases me. I expect that this is exactly what I'm going to be doing, with an additional override after the fan control box that puts my fan on high speed when my AC compressor clicks on. I won't have any feedback issues with an override switch... the thermostat will just behave as designed.

I'm currently extending and appending a Z4 wiring harness to suit the chassis (documentation to follow) and I want to confirm what we'd previously discussed related to the MAF/IAT sensor, because I have a pin number mismatch between the connectors on the X3 and Z4 harnesses I'm combining. Here's the BMW diagram for several of the N52 engines:

Pin 4 on the connector is always sensor ground (M_HFM) and Pin 5 on the connector is always the Intake Air Temperature Signal (A_TANS). These always connect to pins 27 and 28 respectively on DME Sub-connector X60005.

Pin 1 on the connector is always the MAF signal (A_HFM), but the DME pin for that signal changes between models. *I believe* this becomes moot, because Nando's tunes specifically do not use this sensor. Looking at the last diagram, "depending on version" some e90's after 2007 have a IAT sensor that doesn't include any MAF function or wiring. Which versions? Here's one example of a part number:

13627547822

Intake air temperature sensor

From:09/01/2005To:-Weight:0.016 kgPrice:Part 13627547822 was found on the following vehicles:These are all European n52 models, but curiously not the European Z4... which kept the full sensor!

Rather than having these extra signals, grounds and power signals floating around in my harness, I'm going to pull everything but the two wires for the IAT out. Even if I left them connected, I have a 50/50 shot of knowing which pin we would send the MAF signal to based on the info above.

I don't know if power or additional grounding is required for the sensor I have to detect temperature, but I think it's unlikely. If I don't get an intake temp reading when this goes together, I'll track down on of the 13627547822 sensors. Here's the difference:

Converting from MAF to euro IAT to reduce intake restriction, or is there something else I'm not aware of?