Hi guys,

I have a problem with a Plx Vac/Boost with the 3map bar sensor integrated and I'm trying to connect it to the ecu (hondataS300V3). Does anyone running this setup?
I tried with D17 and D19 pins on my p30 ecu but the reading is totally off.
I tried as well to put it in the analog input but seems to work only for datalog and the map sensor does not work in the tables.

Can anyone help me?

 

I've never heard of anyone using an aux input for MAP in Hondata. It's not an option for NepTune.

Did you rescale your cal with the equation on the PLX datasheet? Is the unit grounded correctly at the ecu?

Why not use a stock style extended range MAP sensor (such as the ones Hondata, et al. sell) instead of an external unit?

 

Because I already have the plx wideband and the touch screen gauge. I hate to have 10000 gauges around so I bought the vac/boost module.

I'm trying to find out the problem...I think that I'm missing something with the software

 

That's fair, the PLX daisy chain feature is nice and having a ton of gauges is not so much. I'd be inclined to just use it for the display and rely on the stock system for actually running the car if it was my setup, but that's beside the point if you're set on using it.

Have you correctly entered your MAP sensor cal in S Manager?

 

In the hondata forum they said that it cannot be used as map sensor, but to me sounds wrong. I'm trying to calculate the exact scalar/offset but math isn't my best quality LOL

 

That actually sounds pretty right to me. The map sensor hardware is part of the original ecu hardware, not the Hondata piggyback board. It's likely hardcoded in and the s300 probably doesn't have any say in what input it comes from. Worth a shot though.

 

Finally I had time to give it a shot. Connecting the output from the plx VAC/BOOST unit to D17 on the ecu, and adjusting scalar and offset everything seems to work. I just have to retune the fuel map for the Idle I think, because now the "map" read exact the same as the gauge, while with the oem map sensor I had an offset with the gauge. In fact now it reads 22 vaccum while before it was around 20.

Does anyone know why hondata highly suggest to not use the plx as a map sensor? It doesn't make any sense to me... I'll update tomorrow with new tune

 

they say not to use it because for the readings to be consistently accurate the sensor has to not only feed the signal to the ecu, but the sensor has to also be grounded to and powered by the ecu. otherwise the signals will fluctuate and deliver incorrect fuel and ignition more often than not.
also because the secondary output wires of those guages do not have a zero response time like a direct factory wired sensor, there is always a little bit of a delay due to the computation required within the gauge's circuitry. and if attempting to "T" into the signal wire that feeds the gauge, that's even worse because you can't share the signal with two receiving units; the voltages will be incorrect at both.

 

But what's the point to use the plx module as a datalog unit then? In the hondata forum they said that is good only as a datalog unit. But if it is not accurate, then the datalog is pointless....

and what if I connect the plx with the ground and power that goes in the stock map from the ecu?

 

The point is to use the plx as a datalog unit. key word datalog unit. not ecu component.
yeah, to use only as a datalog unit, simply for looking at, nothing else. definitely not for connecting to the ecu.
and definitely don't connect the plx to the power and ground from the ecu, that will make matters even worse.

 

Well I did it and it worked, but as you said it has a good amount of lag. I am a bit stubborn on these things, I always want to try learn and understand.

Thanks anyway! I can say that this would be helpful to whom will buy the boost/vac plx module.

 

eh, you live you learn. That's how the best in the world become the best, by trying new things and attempting to improve things, and determining what works and what doesn't.