VCM scanner and logging boost

[Jroc]

Has anyone had issues with VCM scanner logging boost incorrectly?

I have a 2015 Hellcat that has had 3 bar MAPS swapped into it, @ostmike corrected for the 3 bar MAPS in the tune and the car runs just fine. The problem I'm having is the boost pressure in VCM scanner is reading way high. I did the 3.8 Whipple swap and have been under the impression that the car has been making 23 PSI this whole time, but Mike said that based on aircharge it's hitting about 17 PSI peak and asked me to watch the dash gauge which I did and was seeing 16 so 17 peak would make sense. The issue is on VCM scanner when I'm logging it says the boost is peaking at 22-23 PSI and then even looses boost after the peak where it will just say the cars making vacuum the whole run and doesn't pick boost up again until I get off the throttle and the boost levels come down. I just tried a custom math parameter (manifold absolute pressure - 14.7) and saw the exact same result as using HPTuners pre-defined PSI channel.

I have been using an old beta version for a while but just downloaded the newest stable release and noticed the same thing on the log. Has anyone run into this and found a workaround?

EDIT: I just realized that when the MAP reading hits 255 KPA it will not go above that and drops down and slowly climbs back up again which explains why it's losing track of boost during the run. What I can't figure out is why it's reading 6-7 PSI higher than the car or aircharge, or the other thing because I'm an overthinker, is VCM scanner right and is the aircharge and dash reading off?

 

[1971demon]

Has anyone had issues with VCM scanner logging boost incorrectly?

I have a 2015 Hellcat that has had 3 bar MAPS swapped into it, @ostmike corrected for the 3 bar MAPS in the tune and the car runs just fine. The problem I'm having is the boost pressure in VCM scanner is reading way high. I did the 3.8 Whipple swap and have been under the impression that the car has been making 23 PSI this whole time, but Mike said that based on aircharge it's hitting about 17 PSI peak and asked me to watch the dash gauge which I did and was seeing 16 so 17 peak would make sense. The issue is on VCM scanner when I'm logging it says the boost is peaking at 22-23 PSI and then even looses boost after the peak where it will just say the cars making vacuum the whole run and doesn't pick boost up again until I get off the throttle and the boost levels come down. I just tried a custom math parameter (manifold absolute pressure - 14.7) and saw the exact same result as using HPTuners pre-defined PSI channel.

I have been using an old beta version for a while but just downloaded the newest stable release and noticed the same thing on the log. Has anyone run into this and found a workaround?

EDIT: I just realized that when the MAP reading hits 255 KPA it will not go above that and drops down and slowly climbs back up again which explains why it's losing track of boost during the run. What I can't figure out is why it's reading 6-7 PSI higher than the car or aircharge, or the other thing because I'm an overthinker, is VCM scanner right and is the aircharge and dash reading off?

View attachment 110803

I'm as clueless reading this post...as if I was reading one of Hickster's....

 

[ostmike]

For tuning purposes I reference pRatio and Aircharge.
These are all the PCM uses (does not reference manifold pressure).
To roughly calculate actual boost pressure take the pRatio x 100 to calculate kPa and then convert it to Psi.
Just be careful how you use/reference "Boost" since it is the measure of resistance and not WHP.
One engine/SC combo could be making higher boost but producing LESS power than a similar combo (with the addition of a longer duration cam and headers) making less "boost".

 

[Speedy!]

There are also multiple ways to setup a custom "boost" PID. I think mine's set up to be (PRatio x Baro) - Baro but it's been a minute since I set it up. It reads correctly. I mainly reference aircharge but it is fun to see a boost number.

 

[fumanchu182]

boost is proportional to PR, PR is dead on in these cars.

(PR * Baro) - Baro = Boost

That was a pull after highway driving. So the 2.4 had fresh air over it.

If you have a 2.4… dont expect a lot of relief from any chiller. They just create too much heat. Also not indicative of sitting in a staging lane heat soaking with an exhaust leak like me 😂

https://www.hellcatforum.org/threads/live-action-from-fumanchu182.6592/page-85#post-346714

 

[Speedy!]

@fumanchu182 I think you're the one who told me how to create that custom PID.

 

[Jroc]

There are also multiple ways to setup a custom "boost" PID. I think mine's set up to be (PRatio x Baro) - Baro but it's been a minute since I set it up. It reads correctly. I mainly reference aircharge but it is fun to see a boost number.

https://www.hellcatforum.org/threads/live-action-from-fumanchu182.6592/page-85#post-346714

Thanks guys, I’ll give that a shot. I mainly want to log it just so I can graph it to watch for belt slip etc.

 

[fumanchu182]

You will notice belt slip when the rpm climb and boost does not. Also keep in mind false belt slip could be your supercharger bypass closing, suggest you log all three.

 

[Unholy707]

You will notice belt slip when the rpm climb and boost does not. Also keep in mind false belt slip could be your supercharger bypass closing, suggest you log all three.

I think he has a3.8, not sure if it has the hellcat electronic bypass?

 

[Jroc]

I'm trying to get this setup but which parameter are you guys using for PRatio? I'm still a bit of a newb with VCM scanner.

 

[Jroc]

I think he has a3.8, not sure if it has the hellcat electronic bypass?

Mine has one, I have a feeling the Hellcat 3.8 has quite a few differences from the hot rod or drag pak 3.8 that has been for sale for a bit.

 

[fumanchu182]

I'm trying to get this setup but which parameter are you guys using for PRatio? I'm still a bit of a newb with VCM scanner.

View attachment 110932

“pressure ratio” dont abbreviate

 

[Jroc]

“pressure ratio” dont abbreviate

Well that makes all the sense I even typed pressure and saw that one. Thanks!