Can a Rocket III take down the establishment, and rule this island

[Gerald]

euh...but if you are looking for 16psi (1100hpa) and stock can do 1200hpa switching back to stock means you don't have to change the map tables? is that then not less work? and the 1.2 stock version has a better fine-reading due to 5 volt for 1200 and not 5 volt for 2600.

way out of my comfort zone here

Past me also.

 

[TURBO200R4]

He is way beyond my experience
I can barely understand the concept much less how u could make it work.
When it comes to turbos all i know is it boasts power and there fun to drive.

 

[ruzzle]

Love your pretty blue vacuum lines, Arto! Very colourful.

 

[R-III-R Turbo]

euh...but if you are looking for 16psi (1100hpa) and stock can do 1200hpa switching back to stock means you don't have to change the map tables? is that then not less work? and the 1.2 stock version has a better fine-reading due to 5 volt for 1200 and not 5 volt for 2600.

way out of my comfort zone here

Sorry typo on my post, I meant I was "seeing" 16 psi on the stock MAP sensor.
The common (mis)understanding is the Rocket's stock MAP sensor was a 1 bar, well it's not exactly 1 bar.
If it was exactly 1 bar, as in only capable of reading up to 1 bar, it would only read from 0 to 14.5psi (14.5 psi = 1 bar). Not 16 psi or more.
I am 'seeking' a lot more than 16 psi as that would only be 1.5 psi boost
Hope that clears it up.

You would think that since the MAP is only used for like 6% throttle or less, then it will only ever need to read 0 - 1 bar anyway, but the trouble is if you go into boost with only a 1 bar MAP then it could be damaged, and you certainly won't be able to use it to map by boost.

If you are going to see 16 PSI at max boost, that's a little over 2 times atmospheric pressure so you would need a MAP sensor that can measure that pressure. If the stock MAP sensor max's out at 1.2 BAR it couldn't give correct info for fueling above that.

Curious, why does BMW even have a 2.6 BAR sensor???
Are any of their bikes supercharged?

Yeah there you go.
The MAP is a BMW part 8637899 which is used in a bunch of cars;

Re understanding, maybe a walk through is best.

What people think is zero pressure, e.g. the air in the room around us, is actually around 1 bar / 14.5 psi / 1000hPa... atmospheric pressure.

A pressure gauge might only read pressure above atmostpheric, like a vacuum gauge only reads from atmospheric (0 psi on a vac gauge) down to -14.5 psi (which is actually 0 psi in absolute terms - e.g. outer space is 0 psi. Then you get to planet Earth and it's atmosphere imparts a pressure of around 1 bar at sea level).

A MAP sensor reads in absolute terms, so it reads from 0 psi upwards.
A 1 bar MAP will read from 0 to about 14.5psi (1 bar).
A 2 bar MAP will read from 0 to 29psi or so (2 bar). And so on.

To me a MAP sensor is like a variable resistor, where if it sees higher pressure then it lowers resistance and thus higher voltage gets sent. Or if it sees lower pressure then it raises resistance, causing voltage drop, and lower voltage gets sent.

Another note is 0 - 5V is a commonly used transmission method for sensors and instrumentation etc.
E.g. look at the TuneECU screen below, you can see 0 - 5V being used to transmit temperature, throttle position, pressures, fuel level.

A normally aspirated engine only requires a 1 bar MAP sensor because it will only see 'vacuum' i.e. somewhere between 0 and approx 14.5 psi / 1000hPa / 1 bar.
But a turbo engine with say 2 bar of boost will need a 3 bar MAP as it will see the same 0 - 1 bar as a NA engine see, plus the additional 2 bar of boost. Makes 3 bar altogether that the MAP will need to read.



Looking at the screen below from TuneECU (this is from the bike with the OEM MAP sensor attached), you can see that the ECU is reporting that the barometer is seeing 979hPa.
This is transduced by the ECU using the 3.94V the MAP is sending it.
So if 979hPa is 3.94V, then 5.00V is about 1242hPa or 1.2 bar.

Somewhere in the ECU's programming (that we can't see with any publicly available program I know of) it has a scale that equates 0.00V = 0hPa at the bottom end, and 5.00V = 1242hPa at the top end (I suspect).

You can also see the MAP sensor is seeing 610hPa here on average across the 3 cylinders as the engine idles.
The MAP signal voltage is 2.50V.
So again, if 2.50V = 610hPa, then 5.00V = 1220hPa or about 1.2 bar.

So it appears the barometer and the MAP sensor on the Rocket IIIs are around 1.2 bar capability, from what I've seen.

But one cannot be certain without seeing the spec on the sensors, as there are too many variables to get an accurate back-calculation. E.g. the lag between TuneECU reporting/displaying the pressure value and the voltage value, etc.

Now back to the screenshot of the same engine, but with the BMW 2.5 bar MAP sensor wired in instead of the OEM 1 bar;

The ignition on here but engine is off.
On the barometer, if 4.12V = 1023hPa, then 5.00V = 1242hPa or 1.2 bar.
The MAP sensor voltage then beside that says it is sending 2.00V. According to the barometer, atmospheric pressure in that location on that day was 1023hPa. Therefore the MAP sensor is seeing 1023hPa and is sending 2.00V as a result.
If 2.00V on the MAP is 1023hPa, then full scale i.e. 5.00V will be about 2558hPa or 2.6 bar.
Making it a 2.6 bar sensor rather than 2.5 bar.

So I was delighted when I wired it up, to see 2.00V, because the BMW sensor had no ID of what pin did what, but they turned out to be the same arrangement as the OEM pins so everything worked perfect 1st go.



So finally back to this throttle balance screen;

It's the same engine and everything as before, when the MAP value was around 630 hPa at idle (I know it said 610hPa above but that was at 1200rpm or so as the engine was cold, but it settled to about 630hPa) when it had the OEM "1" bar MAP sensor.
But now it has the "2.5" bar MAP sensor, and the throttle MAP value displayed has suddenly changed to 340hPa.

The new MAP sensor has to be seeing the same actual pressure as before when engine is idling (say around 630hPa).
But due to the built-in scale in the ECU, that we cannot see or change, the ECU it gets reported on screen as 340hPa instead.

Walking through the math;
New MAP sensor sees 630hPa, which is the known actual real pressure with engine idling, but based on its own scale, it sends 1.38V, as per screen below.
N.B. the MAP volts displayed here is correct as in what the new MAP is sending, but the displayed MAP value of 340hPa is incorrect, that is just what is calculated by the ECU based on what volts the new MAP sends.

So the change occurs when the ECU sees this 1.38V and transduces it (using its built-in scale, the one that we cannot see or change, the one that was designed for a ~1.2 bar MAP sensor, where for example 3.94V is 979hPa (or 248.477hPa per 1.00V) as per screenshot far above) to about 340hPa.

Does that make sense?
Or maybe I made a balls of it (it's late here)


BTW some years ago I made an adapter harness for the MAP sensor, where the signal wire is piggybacked by another wire that runs to the 0 - 5V input on the PCV. So the PCV uses this signal to autotune by MAP value. But that's another day's posting.

 

[wjb]

It sounds like the BMW sensor is scaled differently than the stock sensor and is sending signals that are confusing the stock ECU.
Does the TTS supercharger kit use the stock MAP sensor? If so, do they compensate for above atmospheric pressure by rescaling the values of the stock sensor? Maybe with the tune?

 

[R-III-R Turbo]

Yeah that's it, both MAP sensors have to transmit with a 0 - 5V range but since their pressure ranges differ, the volts sent from each when seeing the same actual pressure are different.
And the ECU is setup to receive the 0 - 5V signal from a 1 bar sensor.
It is not expecting one from a 2.5 bar sensor.

Nonetheless, this should just move the cell being referenced in the fuel or ignition map table a little bit.
So I just alter the values in the cells that the ECU is referencing, and ignore the column header.
E.g. the cell in the TuneECU map for 640hPa & 1000rpm was used for idle fuelling before with the 1 bar sensor, now it will reference the cell where 340hPa column and 1000rpm row intersect.


Oh and re TTS, in my day they instruct to just remove the MAP sensor.
Unfortunately this leaves one with a perpetual check engine light.
Not sure if the kits since 2016 have included a solution.
@RICHARD ALBANS might advise.

 

[TURBO200R4]

I have a tool that uses a 9volt battery and it can send a voltage signal from 0 to 9volts. For example 2.35 volts
I use this tool when i have an expensive part that I want to confirm is definitely ba
Anyway would it be possible to use a tool like this to set the tables?

 

[Gerald]

Sorry typo on my post, I meant I was "seeing" 16 psi on the stock MAP sensor.
The common (mis)understanding is the Rocket's stock MAP sensor was a 1 bar, well it's not exactly 1 bar.
If it was exactly 1 bar, as in only capable of reading up to 1 bar, it would only read from 0 to 14.5psi (14.5 psi = 1 bar). Not 16 psi or more.
I am 'seeking' a lot more than 16 psi as that would only be 1.5 psi boost
Hope that clears it up.

You would think that since the MAP is only used for like 6% throttle or less, then it will only ever need to read 0 - 1 bar anyway, but the trouble is if you go into boost with only a 1 bar MAP then it could be damaged, and you certainly won't be able to use it to map by boost.



Yeah there you go.
The MAP is a BMW part 8637899 which is used in a bunch of cars;

Re understanding, maybe a walk through is best.

What people think is zero pressure, e.g. the air in the room around us, is actually around 1 bar / 14.5 psi / 1000hPa... atmospheric pressure.

A pressure gauge might only read pressure above atmostpheric, like a vacuum gauge only reads from atmospheric (0 psi on a vac gauge) down to -14.5 psi (which is actually 0 psi in absolute terms - e.g. outer space is 0 psi. Then you get to planet Earth and it's atmosphere imparts a pressure of around 1 bar at sea level).

A MAP sensor reads in absolute terms, so it reads from 0 psi upwards.
A 1 bar MAP will read from 0 to about 14.5psi (1 bar).
A 2 bar MAP will read from 0 to 29psi or so (2 bar). And so on.

To me a MAP sensor is like a variable resistor, where if it sees higher pressure then it lowers resistance and thus higher voltage gets sent. Or if it sees lower pressure then it raises resistance, causing voltage drop, and lower voltage gets sent.

Another note is 0 - 5V is a commonly used transmission method for sensors and instrumentation etc.
E.g. look at the TuneECU screen below, you can see 0 - 5V being used to transmit temperature, throttle position, pressures, fuel level.

A normally aspirated engine only requires a 1 bar MAP sensor because it will only see 'vacuum' i.e. somewhere between 0 and approx 14.5 psi / 1000hPa / 1 bar.
But a turbo engine with say 2 bar of boost will need a 3 bar MAP as it will see the same 0 - 1 bar as a NA engine see, plus the additional 2 bar of boost. Makes 3 bar altogether that the MAP will need to read.



Looking at the screen below from TuneECU (this is from the bike with the OEM MAP sensor attached), you can see that the ECU is reporting that the barometer is seeing 979hPa.
This is transduced by the ECU using the 3.94V the MAP is sending it.
So if 979hPa is 3.94V, then 5.00V is about 1242hPa or 1.2 bar.

Somewhere in the ECU's programming (that we can't see with any publicly available program I know of) it has a scale that equates 0.00V = 0hPa at the bottom end, and 5.00V = 1242hPa at the top end (I suspect).

You can also see the MAP sensor is seeing 610hPa here on average across the 3 cylinders as the engine idles.
The MAP signal voltage is 2.50V.
So again, if 2.50V = 610hPa, then 5.00V = 1220hPa or about 1.2 bar.

So it appears the barometer and the MAP sensor on the Rocket IIIs are around 1.2 bar capability, from what I've seen.

But one cannot be certain without seeing the spec on the sensors, as there are too many variables to get an accurate back-calculation. E.g. the lag between TuneECU reporting/displaying the pressure value and the voltage value, etc.

Now back to the screenshot of the same engine, but with the BMW 2.5 bar MAP sensor wired in instead of the OEM 1 bar;

The ignition on here but engine is off.
On the barometer, if 4.12V = 1023hPa, then 5.00V = 1242hPa or 1.2 bar.
The MAP sensor voltage then beside that says it is sending 2.00V. According to the barometer, atmospheric pressure in that location on that day was 1023hPa. Therefore the MAP sensor is seeing 1023hPa and is sending 2.00V as a result.
If 2.00V on the MAP is 1023hPa, then full scale i.e. 5.00V will be about 2558hPa or 2.6 bar.
Making it a 2.6 bar sensor rather than 2.5 bar.

So I was delighted when I wired it up, to see 2.00V, because the BMW sensor had no ID of what pin did what, but they turned out to be the same arrangement as the OEM pins so everything worked perfect 1st go.



So finally back to this throttle balance screen;

It's the same engine and everything as before, when the MAP value was around 630 hPa at idle (I know it said 610hPa above but that was at 1200rpm or so as the engine was cold, but it settled to about 630hPa) when it had the OEM "1" bar MAP sensor.
But now it has the "2.5" bar MAP sensor, and the throttle MAP value displayed has suddenly changed to 340hPa.

The new MAP sensor has to be seeing the same actual pressure as before when engine is idling (say around 630hPa).
But due to the built-in scale in the ECU, that we cannot see or change, the ECU it gets reported on screen as 340hPa instead.

Walking through the math;
New MAP sensor sees 630hPa, which is the known actual real pressure with engine idling, but based on its own scale, it sends 1.38V, as per screen below.
N.B. the MAP volts displayed here is correct as in what the new MAP is sending, but the displayed MAP value of 340hPa is incorrect, that is just what is calculated by the ECU based on what volts the new MAP sends.

So the change occurs when the ECU sees this 1.38V and transduces it (using its built-in scale, the one that we cannot see or change, the one that was designed for a ~1.2 bar MAP sensor, where for example 3.94V is 979hPa (or 248.477hPa per 1.00V) as per screenshot far above) to about 340hPa.

Does that make sense?
Or maybe I made a balls of it (it's late here)


BTW some years ago I made an adapter harness for the MAP sensor, where the signal wire is piggybacked by another wire that runs to the 0 - 5V input on the PCV. So the PCV uses this signal to autotune by MAP value. But that's another day's posting.

Have to read through this several time and try to think through what you're saying, end of the day, don't think this will change things in my world, but good to try to understand and learn.

 

[Frans]

@R-III-R Turbo thanks for the write-up!

 

[R-III-R Turbo]

Have to read through this several time and try to think through what you're saying, end of the day, don't think this will change things in my world, but good to try to understand and learn.

I don't think I'm explaining it very well and that is because I don't fully understand it myself.
As they say if you cannot explain it to a 5 year old then you don't really understand it yourself!
What doesn't help is the lag in reporting values to screen.



One reason why I still use Windows TuneECU over the Android, you have this lovely cell tracer thing that highlights the column and row in the tables that the ECU is referencing from for fuel or ignition, as the engine runs.
Where the column and row intersect, is the cell containing the value that the ECU is working off.

E.g. in this screenshot, the yellow outlined cell is the one.

Based on MAP value (650hPa) and engine speed (1290 RPM) received, the ECU is taking 3452 x20 mg as the mass of air being inducted, and then via its invisible injector spec, is determining the pulse time to open the injector for, to achieve an air/fuel ratio of whatever is in the corresponding cell in the AFR table.

PCV has a similar feature, except it actually highlights the cell itself, which is better.

Anywho the above is with the 1 bar MAP sensor.
The red outlined cell is around where idle is, with the 2.5 bar MAP sensor.
So that is around where I must adjust the values in the cell until I get a nice air/fuel ratio at idle.
And just use L tables to fuel real small throttle positions like 0 - 3%.

If that don't work good (probably because there is not much room on the left side of that cell), I will have to work around it with good ol PCV.
I asked Alain for a special TuneECU turbo map that has up to 2500hPa in the L tables but he doesn't seem interested.