Alright, so I installed my AEM digital boost gauge yesterday, no problem (Tee'd into the same line as the stock MR gauge). However, there is a difference between the two on full boost, 4th gear. The AEM seems to peak at 21-22 psi, yet the stock MR is around 1.4 (which is assumed to be ~20 psi). Is the stock gauge that inaccurate? I had always heard it was pretty accurate. Or is the AEM gauge inaccurate? I checked all the connections on the vacuum line and checked for kinks and it seems to be all good. Oh and also, my vacuum reads 16 in/hg at idle. Sometimes it will jump back and forth from 16 to 18 pretty rapidly (on the AEM gauge). Is that a normal number for vacuum?

All my IX has is a Megan TBE + Hallman Pro (set at stock of course).

 

You may not be able to catch the factory gauge showing peak boost with the naked eye. Its needle moves very quickly. Too, if your MBC is set to stock boost, 1.4 is just about right, if not a tad high, IME.

 

Another thing too. When I hit peak boost on the AEM gauge, it flucuates rapidly from like 20-22. It never really "stays" at a number. I was thinking...could I have a leak somewhere in some other vacuum lines?

 

I tried to compare my stock boost gauge vs my Defi boost gauge and as far as I could tell my Defi gauge spiked to around 19-20psi and my factory gauge would spike to 1.4 kg/cm2 which is about 19-20psi. Im gonna log my car to see if my gauges are accurate or not.

 

well since the are most likely not ported to the same source and the aem uses their stand alone sensor variances in the results are to be expected

 

thats cause internal wastegates have hard time holding boost, also if you have a crap boost controller this happens too...

its normal to not stay at one number

 

Yeah, I figured it could be that crappy stock waste gate. What about my vacuum being at 16 in/hg? Doesn't that seem a bit off?

 

search man...

 

I did search. And I see some people saying anything from 15-20 is normal and then some people saying 18-20 is the norm. I was looking more for a definitive answer.

 

Mine idles at 12-13 with M2 cams. I think 16 sounds about right. That sounds about what mine used to idle at with stock cams. If you're that worried about it, do a boost leak test and a compression test. If they're both good, I wouldn't worry about it.