Help with building your Speeduino, installing it, getting it to run etc.
By kettlekev
#58712
Having successfully got my 750 2 stroke running on speedy, I am starting a new project on a 4 stroke turbo bike.

Can someone pls sanity check me on the sensors list.

Crank position
Cam position
MAP
WB O2 sensor
TPS
IAT
CLT

What is the function of the boost solenoid feature? Is this related to the waste gate control in any way?
By kettlekev
#58716
Makes sense. I can see in the manual there is a map table for boost but I cant see a basic explanation of how it works??

Why is the cam signal not important?
By kettlekev
#59668
I guess I will need an external BARO sensor as well?

The boost table controls to a waste gate pressure in Kpa and I assume the BARO sensor is the source for that?

My general turbo setup diagram (mostly a gas flow diagram) is;
CX Turbo setup.JPG
CX Turbo setup.JPG (80.84 KiB) Viewed 1014 times
The tricky bit is knowing where to start with the boost control map.

The simple mechanical waste gate on the bike slowly opens as pressure builds to a set psi (19-20 psi) where it is fully open. I dont think anyone has tried to 'map' that so that will be a challenge......
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By jonbill
#59669
I think whether you need a baro sensor depends on how much the baro pressure can change during a ride/drive - Speeduino takes a baro reading from the MAP sensor at startup, before the engine runs. So if baro won't change much during your journey, you won't need an additional sensor.
If on the other hand you live on the top of a big mountain, and ride to the town in the valley, you probably will need a baro sensor.
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By PSIG
#59675
kettlekev wrote: Sat Nov 19, 2022 9:35 am I guess I will need an external BARO sensor as well?
Agreed, the 2nd real-time Baro sensor is optional. I use one whenever I can, as it simply adds to tune stability. One of my personal "rules" is to avoid (as much as possible) anything that makes the ECM work harder to stay on-target, forcing the ECM to make lagging corrections for deviations from tune. The problem with reactive lagging corrections, is that they only work after the burn, so the run is already incorrect before it tries to fix it. Proactive corrections like Baro work to keep the tune correct, so the deviation from tune is minor and effects are less, while reactive corrections (e.g., WBO2) are hopefully minor. You are herding cats, and Baro helps with that, keeping them mostly in-line instead of chasing them after they get away. :lol:

While the effect is incremental, everything works 'better', from idle or boost control, to AE, timing or detonation control, etc. The less 'edgy' your tune is, or lower requirements for efficiency and performance, the less required or helpful these accuracy enhancers are.
kettlekev wrote: Sat Nov 19, 2022 9:35 amThe boost table controls to a waste gate pressure in Kpa and I assume the BARO sensor is the source for that?
The MAP sensor is the primary boost sensor. While barometric pressure affects it, the system will still target the boost levels set. This means on a high density-altitude day, the turbo/SC will work harder to reach the same boost level. Not relative boost (compared to baro), but actual boost (MAP), e.g., 100kPa ambient will boost 50kPa to 150kPa target. 80kPa ambient will boost 70kPa to 150kPa target. This occurs whether Baro is active or not, but baro can alter fuel and timing if needed to stay on-tune while it is deviating from original tuning conditions.
kettlekev wrote: Sat Nov 19, 2022 9:35 am The tricky bit is knowing where to start with the boost control map.
The simple mechanical waste gate on the bike slowly opens as pressure builds to a set psi (19-20 psi) where it is fully open. I dont think anyone has tried to 'map' that so that will be a challenge......
Not tricky. Think of it as a target table of where you want boost to go. Any mode will require tuning and tweaking, but starting with simple and moving to PID (if needed) will allow you to refine where the system stabilizes boost pressures on the table. Baseline is the default wastegate set pressure (spring and diaphragm) of your system, and is the lowest available boost. Boost controller opening raises the boost by diverting the pressure used to open the WG, forcing higher boost. Take care to not confuse boost controller open/closed with wastegate open/close.

I may not be reading you right, and boost builds on a closed wastegate, until it reaches close to target boost pressure, and then the WG opens to attempt to hold boost at that set pressure. It is a simple reactive regulator system. The WG should not be 100% open (normally) as that would be at the edge of uncontrolled boost, often seen as "boost creep".

With the default of boost control valve closed, the wastegate will open at its sprung pressure, the lowest boost pressure. With BC diverting the pressure to open it, boost (MAP) may be raised. The more you open the boost valve to divert pressure, the higher your boost rises (for the given conditions). While there are many variables and factors involved, the basic concept is simple—deny the pressure to open the wastegate, and the MAP (boost) will rise.

Of course, I would suggest you work your tune up to this point. ;) The last thing you would want to do is WOT to "see what it does". You always want to work up to that level, so you have a very good prediction of what it will do and what it will need to be safe. Have fun! 8-)
By kettlekev
#59678
Baseline is the default wastegate set pressure (spring and diaphragm) of your system, and is the lowest available boost. Boost controller opening raises the boost by diverting the pressure used to open the WG, forcing higher boost. Take care to not confuse boost controller open/closed with wastegate open/close.
Bear with me. Very new to turbos......
So my baseline as I understand it is the 19-20 psi that opens the waste gate.

If the boost controller is diverting the pressure that opens the waste gate (as the boost controller closes as in my diagram), isn't that lowering or maintaining the boost (as revs rise)?

I am obviously confusing it somewhere.....

EDIT. Think I've got it. With the boost control in the normally open position all pressure goes to the WG. So it can stay open. As the BC valve closes some of the pressure gets diverted reducing pressure on the WG spring/diaphragm which would start to close the gate and keep boost pressure high.

Need to get my head around where to start with the table setup next..
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By PSIG
#59690
Important is to know exactly which way (of many options) the wastegate and boost controller are configured. Options depend on if you have a single or dual-port wastegate, and boost levels required. Normally, the default with a disconnected BC, the WG will see manifold pressure and open at spring pressure for minimum boost. This avoids a signal failure from runaway boost. Only with signal commanding the BC to bleed pressure from the WG (or redirect it to the top of the WG diaphragm) will you get increased boost above the WG spring rating. Examples here and many other sites.

If your WG is rated 19 PSIG, that's the minimum boost, and BC will take it higher. That's typical, but verify how yours is configured or you will chase your tail trying to figure it out.
By kettlekev
#59693
Thanks. In my setup the Boost control valve is a 3 way valve. This common line of this valve feeds the waste gate, the normally open port is fed from boost pressure so that in a control signal failure, boost pressure is always fed to the waste gate.

The normally closed port (that is controlled by the Speedy map/table) is fed back to the inlet manifold.

So as I understand it, this 3 way valve gives fail-safe protection.

I also plan a bypass valve that I assume would be set to max boost pressure positioned before the throttle bodies to protect the system during rapid throttle closure which again will vent to the inlet manifold.

On the boost table, So if my max waste gate pressure is 20 psi, this populates the low end of the table. But how do I know what shape to make the table and what my possible max boost pressure is?

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