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I've currently got an edge insight on my sig. Looking to get the edge boost gauge and wondering if tall recommend putting the sensor in the intake horn or another spot? My insight reads 36.6 with my efi live tuning but I know I have a few small leaks in my intercooler so I knows it less.
No real difference between air horn or a boost bolt into the manifold. If you are reading 36.6psi boost (as opposed to MAP) then you won't see a difference with an external gauge. Until you clear 40psi of boost there really is no need for the external gauge. With your CTS you can get the EAS universal sensor harness and a 100psi 5V sensor to integrate the boost reading into the CTS.
So should I be reading the boost from the MAP or the intake horn. I would think that since I have a few leaks in the front of my intercooler I would see a considerable difference in psi before the turbo and after the intercooler. Just want to know best spot to get readings and yes. I will be getting the edge sensor and sensor setup. I already have the 12v power and the expandable egt and turbo timer. I'll be also getting the temp sensors for my diff and transmission in the future.
First let me explain what I meant by MAP. The computer has two PIDs that are related. Boost and Manifold Absolute Pressure. Both of these PID are read from the MAP sensor in the intake manifold or do be more correct MAP is read and Boost is calculated. MAP goes from 0psi in outer space to about 55psi and is about 14.7psi at sea level. The computer takes the MAP pressure and subtracts the Barometric pressure that is read from the sensor on the Air filter intake to the turbo to determine the boost pressure. This means that at sea level the valid range for boost is 0 to a little over 40psi and go a couple PSI higher at high altitudes. So if you are seeing 0psi on the CTS with engine on but not running you have the boost PID.
35-40psi of peak boost is about all you will get with a stock turbo so having a external boost guage doesn't really provide any benefit if you are reading 36-37 psi anyway. The pressure you are concerned with is what the intake manifold sees and there won't be a significant difference between reading the air horn or the manifold; however, reading the manifold would be the best location for accuracy but the numbers will be less than 1psi difference.
Every inter-cooler has a pressure drop going through it. So if you were to measure the turbo side of inter-cooler you would read 2-5psi higher reading. This is normal and not really worth being concerned with. Having a boost leak on the engine side of the inter-cooler doesn't affect the drop significantly your reading on the two sides would probably be less than 1psi difference between no leak and having leaks. I.E. they would still be within 2-5psi of each other.
If you think you have boost leaks you are better off fixing the boost leaks and not worrying about adding an external boost gauge until those leaks are fixed. It isn't hard to build a intake adapter that will allow you to pressurize the system enough to check for boost leaks. It doesn't take more than about 5psi to cause soapy water to bubble on a leak.
Ipennock.... Thank you for that in depth explanation of how this all works. I think I have about a 1-2psi leak on the engine side roughly where the front bumper doesn't cover the lower inter cooler. Just was wondering was was most accurate.
The next question is should I be using the insight boost pid or the MAP pid instead or does it really matter? Based on your reply I don't think that it does matter so I might just stick with the boost pid. I will be adding a temp sensor to my transmission once I do the transmission cooler that another TDR member shared with me.
The boost PID works fine and is easiest to use. I brought up MAP PID because we occasionally get the question on why "I see 14 psi boost at a idle".
If you think you have a boost leaks you should get it fixed. It won't affect your peak boost that much but it will hurt part throttle boost which reduces your fuel milage.
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