MS45.0 --> MS45.1 success! Wideband fuel control now possible

[pokeybritches]

After months of work, I’m happy to report that I’ve successfully swapped the stock MS45.0 ECU for MS45.1! Since I haven’t seen anyone else do this before, I’m going to call first

The advantage of MS45.1 is that it uses wideband oxygen sensors for fuel control. MS45.0 is the standard ECU found in the 2003-2005 BMW Z4 3.0i and 2.5i, and it uses narrowband control. Narrowband sensors are all but worthless at full load because they can only tell the ECU that a mixture is lean or rich as compared to lambda 1.0… not *how* lean or rich. Wideband oxygen sensors can read the exact lambda of the mixture, allowing the ECU to provide precise fueling to meet the mapped targets. This is safer and will result in more power, especially if street tuning the engine with data logs.

On pump gas, lambda 1.0 = 14.7 AFR. Pump gas AFRs of 14.5 and 10.0 would read identically with a narrowband sensor. Even in a naturally aspirated application, this discrepancy in AFR can have a massive impact on how the car performs. In a forced induction application, the variance in AFR values could make the difference between an engine bogging, underperforming, and prematurely wearing components (rich) or catastrophically failing (lean).

The hardware conversion is easy once you get past the software challenges with the ECU, and I’m working to make the entire solution totally plug n play with a swap-in ECU. The only downside with the conversion is the loss of sport button functionality. This doesn’t make any difference to me personally since I have dialed in my preferred throttle mapping into comfort/normal mode. If you like the light-up button more than horsepower or long-term reliability, then this conversion is not for you. If you prioritize performance and robustness no matter the conditions, then I hope you find this solution as exciting as I do!

[Steeler]

Originally Posted by pokeybritches

After months of work, I’m happy to report that I’ve successfully swapped the stock MS45.0 ECU for MS45.1! Since I haven’t seen anyone else do this before, I’m going to call first

The advantage of MS45.1 is that it uses wideband oxygen sensors for fuel control. MS45.0 is the standard ECU found in the 2003-2005 BMW Z4 3.0i and 2.5i, and it uses narrowband control. Narrowband sensors are all but worthless at full load because they can only tell the ECU that a mixture is lean or rich as compared to lambda 1.0… not *how* lean or rich. Wideband oxygen sensors can read the exact lambda of the mixture, allowing the ECU to provide precise fueling to meet the mapped targets. This is safer and will result in more power, especially if street tuning the engine with data logs.

On pump gas, lambda 1.0 = 14.7 AFR. Pump gas AFRs of 14.5 and 10.0 would read identically with a narrowband sensor. Even in a naturally aspirated application, this discrepancy in AFR can have a massive impact on how the car performs. In a forced induction application, the variance in AFR values could make the difference between an engine bogging, underperforming, and prematurely wearing components (rich) or catastrophically failing (lean).

The hardware conversion is easy once you get past the software challenges with the ECU, and I’m working to make the entire solution totally plug n play with a swap-in ECU. The only downside with the conversion is the loss of sport button functionality. This doesn’t make any difference to me personally since I have dialed in my preferred throttle mapping into comfort/normal mode. If you like the light-up button more than horsepower or long-term reliability, then this conversion is not for you. If you prioritize performance and robustness no matter the conditions, then I hope you find this solution as exciting as I do!

Fantastic news Josh.

I'm in. Looking for the required parts now.

[GuidoK]

Very interesting.
I assume you mean with loss of sport button functionality you mean the change in throttleresponse and that the change in steering response keeps working?

[pokeybritches]

The sport button no longer illuminates, and I have not tested steering response or automatic transmission shifting since my car is a manual. I'm fairly certain the ECU broadcasts sport mode status via CAN, and if the ECU no longer recognizes its status, sport mode will not be announced as active on the data stream. The ECU does have parameters for setting the sport mode status to ON by default, so it may be possible to have it always active.

My next project is hydraulic steering conversion, so I'm not really sweating any loss of the heavier steering mode.

[wdb]

Cool! I'm not a potential customer but I love that you're doing it. When I had the 3.0si I wished that the stupid "Sport" button wasn't even there. It made the throttle into an on/off switch. I did like the heavier fake steering feel but then I didn't really mind the lighter fake feel; I just drove the car with my hips instead of my hands. That said, hydraulic steering will put a smile on your face for sure.

[Bmwteo]

hello! does this swap work ? or not yet

[pokeybritches]

Yes

[Bmwteo]

and how much does this conversion cost ?

[Steeler]

Originally Posted by Bmwteo

hello! does this swap work ? or not yet

Hello, yes the swap works.
Basically a plug and play harness and DME swap.
I have installed the necessary parts on my FI M54.
Engine starts and runs. Fine tuning of the DME is ongoing.

[pokeybritches]

Originally Posted by Bmwteo

and how much does this conversion cost ?

It will be in the neighborhood of $500 once released. This includes a refurbished MS45.1 ECU, VIN change, EWS removal, other modifications to the software, and copy of your MS45.0 tune to MS45.1. It does not include the wideband oxygen sensors or wiring harness, but a full pnp harness is fairly cheap these days. Due to time constraints, I’m only working with existing customers at the moment, but I plan to open it up to everyone once my current 3.0i project wraps up.

[Terraphantm]

Originally Posted by pokeybritches

The only downside with the conversion is the loss of sport button functionality.

It’s been a while since I poked around with this, but the sport button functionality can be enabled. Requires some hardware modifications to the DME and the appropriate software switches to be triggered. I had it working on my e46 zhp before I sold it.

Edit: Found my old pictures and notes:

Software changes:

LC_VAR_SOF_SWI_MON: 00 -> 01
C_V_SOF_SWI_ON_BOL_MON: 00EC (1.15v) -> 00F6 (1.2v)
C_V_SOF_SW_ON_TOL_MON: 020A (2.55v) -> 0200 (2.5v)
LC_VAR_SOF_SWI: 00 -> 01

Middle two are probably not strictly necessary

Hardware changes:


Add a ~7nf cap to the highlighted spot (will be empty on the MS45.1)


Add the items labeled in red above (the items in yellow appear to be for an unused button)

You will have to remove a 10kΩ resistor that's present on the MS45.1 in place of the 10 nf capacitor (see below)



The actual status LED is a bit broadcast over CAN, which is read by the EPS ECU which triggers the LED. E46 doesn't have such a thing, so I built a little arduino circuit to read the bit and trigger the LED. Nowadays you could probably use cheaper / more compact hardware to do the same (I last worked on this 7 years ago apparently). That's probably also something that would need to be considered for cars that convert to hydraulic power steering. It may also be possible to modify the DME code to trigger some output based on the sport switch, but I didn't dig too deep into whether there are any suitable unused outputs.

[pokeybritches]

That’s some awesome work!! I’m going to see if I can’t get sport mode activated on MS45.1 too. Thank you!!

I had experimented with some of the sport mode parameters to try and get it to default to “on” at startup. Your solution is significantly better.