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Howdy folks,

I've noticed that my map values in the log have changed recently and don't read the correct amount of pressure.

I used to subtract the baro pressure from the absolute map in the log and that would give me my boost reading. The highest I saw was 46 absolute or something so I figured that it was getting data from the 4 bar boost sensor.

Lately it looks like it is pegged at 23psi which makes me wonder if it has reverted to the stock Tmap.

I was doing some tuning yesterday and ran about 40psi of boost according to the dyno and the log still shows 23psi.

I also noticed that the boost error is always showing it to be under which has been causing the closed loop boost control to go nuts. I asked for 27psi after 5000rpm and it ran 40psi. This was ok as I knew it was going to happen and the fuel was there etc etc, but it seems as though there is something going on.

Anyhow that's about it. Any ideas are appreciated.

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You can log IBP which is your actual boost pressure instead of logging map. 

What map sensor and map scaling are you using? 

Make sure your units are correct as well. Some of them are in inHG and are not currently configurable in 1.25

Also are you using the tmap switch over logic in the custom os? 

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6 hours ago, Puffwagon said:

I have just noticed that in the log it shows 363 kpag and it converts to 260 kpa in the drop down.

The unit converter says it should show 463kpa when the log shows 363kpag.

I'm not sure what the issue is here. Both statements make sense. KPag is simiply kPa + barometric (roughly 101.325 kPa)

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I'm using a bosch 4 bar map and I worked out the scaling ages ago. It is 26.75 etc slope and 1.84 etc offset.

The log is showing 77ingh/37.9psi/363kpag when the actual boost was 39.5 psig. It has shown more boost in the log than 23psi before, but now it isn't showing the correct amount.

The log shows 363 kpag. If I put 363 kpag into the unit converter it turns it into 463 kpa. If I change it in the log from kpag to kpa, it minuses 100kpa instead of adding it.

I'll try the IBP logging and see if that changes anything.

 

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Just did a quick log. The IBP is reading correctly and showing 50psi which is 35psig. The manifold absolute pressure is still stuck at 38psi, which it never used to be.

It is still showing a very minor underboost error which is odd, as the desired boost is 10psi under the actual boost at this time. There is nothing in the wg settings that would allow it to act like this. It should hit boost cut (0.8 cut) at 5psi over target. The boost cut used to work.

 

I'm using the Tmap switchover and it is set to 4.2 volts. I left it there to keep the drivability of the stock tmap. I spose I can try it at 2 volts or something?!

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16 hours ago, Puffwagon said:

I'm using a bosch 4 bar map and I worked out the scaling ages ago. It is 26.75 etc slope and 1.84 etc offset.

The log is showing 77ingh/37.9psi/363kpag when the actual boost was 39.5 psig. It has shown more boost in the log than 23psi before, but now it isn't showing the correct amount.

The log shows 363 kpag. If I put 363 kpag into the unit converter it turns it into 463 kpa. If I change it in the log from kpag to kpa, it minuses 100kpa instead of adding it.

I'll try the IBP logging and see if that changes anything.

 

Hi PuffWagon,

    Can you help me with your 4 bar Bosch Settings as they are way off from what I have and would cause under-reading of boost. Here are the settings I have:

image.png.0fccef259bee92e2623fbf5a530f98e9.png

Lets change this to start with and see if we get in line. 

With respect to:

"The highest I saw was 46 absolute or something so I figured that it was getting data from the 4 bar boost sensor"

the 46 "Hg is roughly the 23psi you may be seeing.

 

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9 hours ago, Darryl@pcmtec said:

Hi PuffWagon,

    Can you help me with your 4 bar Bosch Settings as they are way off from what I have and would cause under-reading of boost. Here are the settings I have:

image.png.0fccef259bee92e2623fbf5a530f98e9.png

Lets change this to start with and see if we get in line. 

With respect to:

"The highest I saw was 46 absolute or something so I figured that it was getting data from the 4 bar boost sensor"

the 46 "Hg is roughly the 23psi you may be seeing.

 

 

I used that scaling and the boost reads lower now. As such the wgdc stayed at 100% for much longer than it should have. It didn't trigger overboost at all at all. The desired boost is still at 26psi.

I think a sensor might be stuffed cos the boost control was working fine and now it isn't.

 

 

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So yerp I got a solution  now I reckon.

After using my scaling, Daryl's scaling and Stathi from IMS scaling, I could see there was still an issue.

There was advice to put the stock Tmap to 6V a while ago so I had done that. Also my voltage switchover to the 4 bar sensor was 4.2 volts. I put the stock tmap values back in and changed the switchover to 3.5V.

The first run on the dyno today pulled 35psi with a desired boost of 20psi. After I changed the tmap range and the sensor switch point, it ran a total of 22psi with a 2 psi boost error...so basically normal. I've yet to look through the log but it seems that it was probably the voltage switch point. I wonder if the stock tmap is on it's way out?

Anyhow this can be marked as sorted for now. Thanks for the help guys 😁

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PuffWagon, it has been a long time but I thought I made the MAP switch point 4.15V and just below the factory MAP max Volts for the reasons you state. I remember the original 4.2 volts was awound 18.5 psi. I agree the max volts should be set to something over 5.0.

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Puffwagon, as a quick test without the engine running turn on the ignition and check the readings of the two sensors. They both should read the same value and it should be around 100 Kpa depending on altitude.

With the engine running you could load it up a bit and check other readings as well, just keep it below the voltage switch point.

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Had a quick check of the values with the engine off.

The tmap was saying 14.56psi which is about right here. We're at sea level.

The boost sensor was showing minus 1.5psi with my scaling and plus 0.66psi with Stathi's scaling.

I left his scaling in there for now and will get further into it when I've got time.

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Update:

It made 22psi with desired boost of 20 the other day, after I lowered the tmap voltage switchover to 3.5V.

Today I changed only the desired boost to 25 psi and it ran up to 32 psi.

I've also just checked logs and can confirm that the manifold absolute pressure in the log used to read up to and over 47psi and now it is pegged at 38psi. There is still something going on that shouldn't be. I'll try swapping out the tmap and see if that changes anything.

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On 2/14/2021 at 10:57 AM, Puffwagon said:

I have just noticed that in the log it shows 363 kpag and it converts to 260 kpa in the drop down.

The unit converter says it should show 463kpa when the log shows 363kpag.

 

On 2/14/2021 at 5:04 PM, Roland@pcmtec said:

I'm not sure what the issue is here. Both statements make sense. KPag is simiply kPa + barometric (roughly 101.325 kPa)

 

The log shows 361kpag/260kpa/37.75psi.

If you put 361kpag into the unit converter it will convert it to 460kpa. The log converts 361kpag to 260kpa.

If I take the 360kpag number, it converts to 52.2psig. If we subtract the barometric pressure of 14.7psi from it, it converts to 37.51psi. The dyno was showing roughly 35psi.

It appears there is an issue with the logger. I think that the psi figure in the logger is actually supposed to be the psig figure. It never used to be like that, as I'd have to subtract the baro from the psi figure in the log to get my actual boost pressure. It's also listed as manifold absolute pressure which means it includes the barometric pressure in the figures, unless listed as "kpag" for example.

Whether what I've described is 100% correct or there is something else happening behind the scenes, there is something happening now that wasn't before.

I can put up some pics if needed to show that this is happening but I think I laid it out fairly clearly.

Haha I've also had someone else verify that I'm not just imagining things ;)

 

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So another update...

This morning I hooked up a 35psi boost gauge and with the desired boost at 25, it was running over 35psi. With the desired boost at 26 it went over 40psi.

I came home, removed the signal pickup for the knock box from the boost sensor signal wire and it seemed to fix it. It was a needle pickup so maybe it had earthed out on something? Just by removing that, the car went back down to 25psi, albiet with funky wg control.

A few runs up and down the road to fix the wg duty etc and it seems to run 25psi most of the way up.

Since I had tuned it and scaled the injectors to suit the previous load it was seeing, everything will be rich af now. It's still got 60% inj duty with 10psi less boost, so it will need more dyno time.

 

Anyway, as always thanks for the help and hopefully this one can be put to bed once and for all.

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