VEMS EGO correction, how do people use it?

[A80Avant]

After recommendations from various different people i have it as a closed loop till 130kpa and then open loop with the VE table alone. Seems to be working nicely.

However after considering using the water/meth a bit more often, i was wondering if i should use closed loop for all the map so as to allow the lamda to keep mixture from getting too rich when meth is injected. That way i wouldnt have to worry altering the table.

Of course the differences here are small, but id hate to loose power while injecting water/meth.

Do you think that lamda would be 'quick enough' and not oscillate too much? as VE table alone is pretty damn accurate!

[prj]

The problems with WBO2 feedback are:
* Misfire - if the engine misfires, the AFR will show lean (unburned oxygen in the exhaust).
* Delay time - can be seen very well from logs of requested vs. actual AFR, that the WBO2 is delayed. This delay varies with gas velocity somewhat as well.

If you want to use meth, the best would be a progressive system with a level sensor in the meth tank and a flow sensor in line as well.
If any of those sensors is not reading, it should switch map.

I wired this up on Motronic, VEMS has programmable I/O's, I guess you could do the same.
If you really want to use and abuse the power of meth, you have to run a huge lot of it and lean out your AFR's.
Of course, if you do not have flow and level sensors, this could potentially be very dangerous. I am still working on how to get proper map switching into my RS4's ME7 ecu.

[A80Avant]

I see. Those oscillations are what I'm afraid of. I have low level indicator, but not a flow indicator. The 2 times I had a problem with the kit was only observed indirectly, ie no IAT reduction or no led lightup at correct boost level. There are more gadget I could use but tbh I don't want to fill the car with.more gadgets...

sent using Android

[A80Avant]

There's a solenoid used from snow performance for purposes when the pump is higher than the tank, but I'm not sure if it could be used for flow detection

sent using Android

[prj]

Aquamist HFS-3 has a flow sensor, which actually detects if flow of meth has stopped to the engine...
Basically as you said, a level sensor is not good enough if you want to run a lot of meth.
If the pump goes bad or something else like that happens, the engine can blow up, so you need extra security.

P.S.
I would say UEGO feedback is not the right way to do this.
By the time that shows anything, you've already possibly damaged the engine, whereas with a flow sensor, the map can be swapped BEFORE the meth-less mix reaches the cylinders...

[A80Avant]

yeah, i see your point
but if wideband was going to be good enough for the fueling part of the equation, i would go with that initially, and then for the timing part of it, i would wait for the better knock control to get serious with the timing. I already know that if i give even 2deg of timing more on high boost atm, it doesnt knock, so i wouldnt go further than that.

What i didnt want to have is to become overly rich in which case there is no point, as power is lost rather than gained.

[prj]

Yeah, true, but imagine you have UEGO control leaning the mixture.
Now your meth runs out.

Now there is mix in the cylinders without meth.
It will start to knock and go lean very fast.

So knock control would be a "fast path" to controlling the detonation and UEGO feedback a "slow path".
However, both of those would react to something that already occured in the engine..

With a flow sensor you can swap maps and enrich/drop timing before it even knocks.
And of course the knock control and uego feedback would provide additional security.

[A80Avant]

yes, i need to find out if that solenoid that snow perfomance uses for siphoning conditions can work with vems by triggering a config switch, or at least a safe condition...