Equation Formula for Boost Gauge with SCT livelink

[Devman]

Ok I have been trying to come up with a formula for my boost sensor for months now. I have an electronic boost/vac gauge from speedhut which comes with a 3 bar boost sensor. The gauges range 30InHG to 10psi. The sensor actually has a linear pressure-voltage relationship and is as follows:
-30-30 scale .5 to 4.5 voltage range, 0=1.81volts
at -30 PSI the sending unit will return 0.5V
at 0 PSI or neutral pressure the sending unit will return 1.81V
at 30 PSI the sending unit will return 4.5V
I have been trying to get boost to read properly on my livewire TS for about a yr now. all my wiring is always done to perfection. Any help with makin up a formula would be extremely appreciated.

Also if you or anybody reading this is familiar with LiveLink, how come I cant export a user defined pid to the livewire?

When your using LiveLink and you press tools at the top and then press equations, How do I transfer a equation formula to the LiveWire TS

 

[Nate14120]

On a line graph showing correlation between -30 to 30 and 0.5 to 4.5, the incline is 15psi per 1v.

Your samples of 0 to 1.81 and -30 to 0.5 do not follow the same incline mathematically. That incline is 22.9psi per 1v.

Either you samples are wrong or your sensor isn't linear.

 

[Devman]

Ive recieved tht same data from mulitiple sources. However speedhut.com were the ones tht told me it was linear

 

[Black02GT]

Ok I have been trying to come up with a formula for my boost sensor for months now. I have an electronic boost/vac gauge from speedhut which comes with a 3 bar boost sensor. The gauges range 30InHG to 10psi. The sensor actually has a linear pressure-voltage relationship and is as follows:
-30-30 scale .5 to 4.5 voltage range, 0=1.81volts
at -30 PSI the sending unit will return 0.5V
at 0 PSI or neutral pressure the sending unit will return 1.81V
at 30 PSI the sending unit will return 4.5V
I have been trying to get boost to read properly on my livewire TS for about a yr now. all my wiring is always done to perfection. Any help with makin up a formula would be extremely appreciated.

Also if you or anybody reading this is familiar with LiveLink, how come I cant export a user defined pid to the livewire?

When your using LiveLink and you press tools at the top and then press equations, How do I transfer a equation formula to the LiveWire TS

Edit: My first post below had the X and Y axes switched which obviously yields an incorrect equation. Post #10 is correct, sorry for the confusion.

That is because OP tricked you, it's not -30psi it's -30 inHg which is
-14.7346 psi. Anyway the equation should be y = 0.0895x + 1.8148. Just keep in mind that it will measure vacuum in PSI with this equation but I'm sure you more interesting in boost.

Unfortunately, I pretty sure the custom formulas only work in Livelink though.

 

[Devman]

That is because OP tricked you, it's not -30psi it's -30 inHg which is
-14.7346 psi. Anyway the equation should be y = 0.0895x + 1.8148. Just keep in mind that it will measure vacuum in PSI with this equation but I'm sure you more interesting in boost.

Unfortunately, I pretty sure the custom formulas only work in Livelink though.

what do you what do you mean by the OP tricking me? but I'm going to try that equation out that you gave me and see how it works

But yeah I realized it was -30 inches of mercury but I didn't even think of converting inhg in to psi that should be very helpful. Thanx so much

I've been trying to work this problem out for like a year. however I did speak with SCT today or derive systems as they're now owned by and I asked them if they could come up with a formula for me based on the sensor data, i also asked if their was a way to transfer a custom equation formula to the Livewire or if I could add a user defined PID to my livewire configuration pid list and they basically said no to everything LOL which is retarded if you ask me why wouldn't you be able to transfer a custom formula or a user-defined PID to the Livewire. or at the very least change one of the formulas that they already have made up. like they have formulas for a 1, 2 and 3 bar map sensors why couldn't they just let me change one of those formulas to suit my needs. another thing I had mentioned to them today about the Livewire TS is that when you're in the datalogging screen monitoring your pids there is a second screen that you can swipe to and it says "not in use and that this page is no longer required and to be replaced by a secondary layout. swipeback." he had told me that that second page worked in an older firmware version but I don't see why they would ever get rid of that. It seems like it would be so much better to have a secondary layout to swipe to so you can monitor a bunch more PIDS. the only problem I could foresee with that is if you have too many PIDs listed and being monitored at once it would probably switch from Rapid packet mode to single packet mode and you would see the data rate go real slow. he also said that they're probably going to get rid of it in a future update. And they will probably do it sooner than later because I had mentioned it to them. I remember I had mentioned a problem to them while ago about something and then 2 days later they had an update out to get rid of it.
But basically to conclude it looks like I'm going to have to get a GM 1 or 2 bar map sensor and add yet another sensor to my Boost/Vacuum system just to properly see boost with my Livewire which is extremely dumb if you ask me, I have a boost/vac sensor in place and wired up to the Livewire and I can make the proper formula in Livelink and monitor it with Livelink but I can't do that with the Livewire data logging device itself straight stupid.

 

[Black02GT]

what do you what do you mean by the OP tricking me? but I'm going to try that equation out that you gave me and see how it works

But yeah I realized it was -30 inches of mercury but I didn't even think of converting inhg in to psi that should be very helpful. Thanx so much

I've been trying to work this problem out for like a year. however I did speak with SCT today or derive systems as they're now owned by and I asked them if they could come up with a formula for me based on the sensor data, i also asked if their was a way to transfer a custom equation formula to the Livewire or if I could add a user defined PID to my livewire configuration pid list and they basically said no to everything LOL which is retarded if you ask me why wouldn't you be able to transfer a custom formula or a user-defined PID to the Livewire. or at the very least change one of the formulas that they already have made up. like they have formulas for a 1, 2 and 3 bar map sensors why couldn't they just let me change one of those formulas to suit my needs. another thing I had mentioned to them today about the Livewire TS is that when you're in the datalogging screen monitoring your pids there is a second screen that you can swipe to and it says "not in use and that this page is no longer required and to be replaced by a secondary layout. swipeback." he had told me that that second page worked in an older firmware version but I don't see why they would ever get rid of that. It seems like it would be so much better to have a secondary layout to swipe to so you can monitor a bunch more PIDS. the only problem I could foresee with that is if you have too many PIDs listed and being monitored at once it would probably switch from Rapid packet mode to single packet mode and you would see the data rate go real slow. he also said that they're probably going to get rid of it in a future update. And they will probably do it sooner than later because I had mentioned it to them. I remember I had mentioned a problem to them while ago about something and then 2 days later they had an update out to get rid of it.
But basically to conclude it looks like I'm going to have to get a GM 1 or 2 bar map sensor and add yet another sensor to my Boost/Vacuum system just to properly see boost with my Livewire which is extremely dumb if you ask me, I have a boost/vac sensor in place and wired up to the Livewire and I can make the proper formula in Livelink and monitor it with Livelink but I can't do that with the Livewire data logging device itself straight stupid.

Sorry, meant to quote the second post. The reason why it wasn't linear was the psi vs inhg confusion.

 

[Nate14120]

Sorry if I created confusion. I didn't know there was a different unit of measurement for vacuum. Thought I'd dust off my math skills...didn't go so well.

 

[Devman]

That is because OP tricked you, it's not -30psi it's -30 inHg which is
-14.7346 psi. Anyway the equation should be y = 0.0895x + 1.8148. Just keep in mind that it will measure vacuum in PSI with this equation but I'm sure you more interesting in boost.

Unfortunately, I pretty sure the custom formulas only work in Livelink though.

I tried your formula and this is what I came up with
(.5*.0895)+1.8148 = 1.85955
(1.81*.0895)+1.8148 = 1.976795
(4.5*.0895)+1.8148 = 2.21755
although I don't think your equation was meant for voltage I think your Y=PSI maybe you could help me a little further to understand your math and work out a formula to input into livelink
If I do 1.8148+(30psi*.0895) = 4.498
1.8148+(20psi*.0895) = 3.6048
1.8148+(10psi*.0895) = 2.743
1.8148+(0*.0895) = 1.8148
Ok so I figured out how to get my voltages now how do I turn that around into an equation to get psi

Yea so obviously the data I got from speedhut and others when they said negative 30 they meant negative 30 inhg not psi.

 

[Devman]

Sorry if I created confusion. I didn't know there was a different unit of measurement for vacuum. Thought I'd dust off my math skills...didn't go so well.

No worrys Nate I was just as confused if not then more confused then you were, but it looks like Black02GT is clearing stuff up, So after a year or more of trying to figure this out I made a slight breakthrough

 

[Black02GT]

PSI = 11.179(voltage) - 20.288

My fault switched up the axes

y = 11.179x - 20.288

 

[Devman]

PSI = 11.179(voltage) - 20.288

My fault switched up the axes

y = 11.179x - 20.288

Ok so I implemented your equation and it came out like this
(.5*11.179)-20.288 = -14psi
(1.81*11.179)-20.288 = 0.05401psi
(4.5*11.179)-20.288 = 30.0175psi
which seems to be perfect and nobody else has been able to help me out to that extent. Thank youuu

 

[Black02GT]

Ok so I implemented your equation and it came out like this
(.5*11.179)-20.288 = -14psi
(1.81*11.179)-20.288 = 0.05401psi
(4.5*11.179)-20.288 = 30.0175psi
which seems to be perfect and nobody else has been able to help me out to that extent. Thank youuu

Anytime, my bad on the first post. I was posting between stuff at work and never checked the output.