Experiment Moving the Baro sensor/injector latency
 

I am thinking of moving my Baro. sensor to the intake manifold Just to see what will happen.

I am taking a wild guess that the Milliseconds time in our injector scaling is multiplied by 256 just like Oltmann has found on the timing tables. I also think that the nonstandard units is KPA.

I think it could help with more consistent fueling and getting the injector/Maf scaling done correctly.

The car might have some partial pressure calculations deep in the ECM but It might not. If it does then it would have to calculate it based on MAF and engine capacity while using the baro sensor as a base for them. With the sensor in the manifold calculated capacity at that pressure should be the actual and it would not have to make an adjustment.

Under pressure(boost) it would compensate for the additional injector lag. Which the car could potentially do With MAf and capacity, while using the Baro as a base for them also. But I don’t think it does.

It appears that injector scaling goes as high as 16 PSIA, and as low as -2PSIA, but the calc load max only goes from 7-14 PSI A. So I believe that sensor is capable of a much larger scale then Cobb lets us see.

This also makes me think injector scale could be rescaled to account for the higher fuel pressures.

Also the calc load max. I am not sure what this does but in N/a the max pressure would be Atmospheric and it is positioned correctly. Once you roll into boost this sensor can’t see the aditional pressure. It could possibly help a lot to rescale it for higher pressure such at 30PSI and 2.16 Calc max load.

Questions
1.What do ya’ll think about this?
2. Is anyone running higher then stock fuel pressure? If so have you adjusted the injector latency scale to account for increased lag due to additional pressure.
3. Has anyone who uses programs like Mazdaedit seen any tables that might be calculating Vacuum pressures?
4. Any specific thoughts on the baro pressures being in KPA and the lag time being MS times 256?
5. Does anyone have any experience with the capabilities of this sensor? A Few google searches look like it might be used for MAP on some cars.
6. Does anyone know what Baro. calc load max does?
7. Is Baro. Calc load max normally adjusted when tuning for a turbo?

Logan

interesting. during the days before we had the cobb and were using the INT x--elevation did impact the tune.

4. Yeah MS*256 is probably right. Doubt anyone has cared that much about it. I don't see where you got the idea that Baro is in KPA, only tables I have with a baro component go up to 2. At 2KPA it would be .29psia. It could be in plain atmospheres, but then it couldn't be a negative number. Could be psig which would explain everything. Could be a unit that the ecu easily understands which requires conversion for us to understand.

6. Yeah all the max load tables provide guard rails for the ecu's load calc. If you don't increase them but increase the load range on your fueling/timing tables the ecu will hit what it thinks should be the max load and stop looking at the tables. It can cause bad problems with a turbo tune. I think the max load tables all get multiplied together, but don't quote me on that.

Harlan,

If you look at it in standard on Cobb it goes up to a max of 2 but if if you go to non standard it is 110.82(KPA?) which converts to 16.07 PSIA. That is a pretty reasonable pressure range figuring it might go from 14.7PSIA at sea level with a little additional pressure.

Who said there was a problem ?

No
Not ever seen an issue ..... yet . Have not tried boosting at altitude though.

No one in particular said it is a problem. It is just a hunch I have so I figured what can a little experimenting hurt.

I just found this thread by Oltmann, which looks like there is a table to calculate partial pressures.
https://www.rx8club.com/engine-tunin...essure-229295/

That's cool , interested to see what you come up with .

Are you saying he was wrong or did you just not read his thread?



.

I had barely looked over it last night. I was only up about 36 hours at that time. So i didn't read it real well.

I do think he might have been slightly wrong. He said a value is pulled then the baro pressure is removed from that table.

I think the baro is used to figure calculated load. Then the table is used.

After seeing that table and thinking about it a bit. The sensor probably won't help in the manifold, But if it is in the intake then It might make a difference.

First, he explains that the sensor is only used indirectly for other calculations.

Second, do you understand that atmospheric pressure @ sea level = 14.7 psia?

I guess I missed that. After rereading his thread I can't find anything about it again.


Yes, but it is temp and weather dependent. So when you're driving below sea level in a high pressure zone it can exceed 14.7PSIA OR under boost levels I've seen on this site
you could be looking at 29PSIA or so.

IMO to use the sensor as you suggest would require a dedicated map and corresponding software dedicated to that purpose. I would suggest caution in exploring your intended purpose with an actual FI application.

That's why I'm playing around with things before I go FI. It looks like there may be a few maps that work with it but Cobb isn't the right tool for them. My overall plan is to upgrade and tune each part. So if there is any problems I can pinpoint it and address it. My next thing is Injectors.

if the Baro sensor output exceeds 4.7V a high voltage CEL will be thrown, that only leaves you with 0.5-0.7 V range at the top to work with. If the sensor is as linear at the top as the indicated graph then you likely don't have that much boost range. It should be easily determined based on the info provided. However, Oltmann already addressed the boost question as proposed by Brettus back in the earlier thread.

Cool, I did not think about looking for info like that. Those CEL's are able to be turned off in Cobb ATR

P0107 - BARO sensor circuit low input -
P0108 - BARO sensor circuit high input

it still won't buy you much and then you're screwed if it fails

????