TrinaBabe

iTrader: (3)

Well I think almost all Evo owners run thier cars around 20-22psi with the stock turbo on pump. If you are in that ballpark you are right where everyone else is. I would say if the map sensor reads 20psi your the same as pretty much everyone else (Which would mean the guage is reading around 21.5-22). If you can get away with a little less its fine or little more its fine. I really dont think 1psi would be the difference of a car knocking badly or running fine. Even with my GT35r I can run anywhere from 18 psi with high timing or 22psi with low timing.. I COULD run it at 24psi on pump and it only will knock intermitantly with relatively low timing... Im sure with less timing I could do it fine but I dont care enough to find out. I mean technically look at it this way.. if the map sensor reads 18psi but the guage is 20 and the car pulls hard and seems just as fast as others comparably.... you are better off saying 18psi You can tell people you run less boost but still make just as much power

EVO8LTW

iTrader: (41)

There is about a 3 psi difference between my Defi boost gauge and the AEM MAP sensor. I wouldn't care about 1 psi, but 3 is pretty different. Undermining my confidence even more is that I have a high quality ($80) tire pressure gauge that is supposed to be accurate to about .5 psi and it reads about 1 psi higher than my Defi at ~21 psi. So I've got a 4 psi range from lowest to highest.

While boost is just a tuning parameter like timing, it's going to bother me if I've got a gauge showing 25 psi on pump, even if the car isn't knocking (that I can tell from the UTEC), just like it'd bother me if had my UTEC set for 24 degrees of timing on pump and it didn't seem to be knocking.

Maybe one of the DC vendors can help me out with this by testing some of their gauges against mine. It's easy to do by just hooking up a boost gauge to a tire inflated to about 22 psi and see what they read. I made an adaptor by screwing together a 1/8" npt tire chuck to a 1/8" ntp barb fitting.

Sometimes I wonder if the power variances from car to car are partially due to inaccurate boost gauges. My understanding from some locals that have been custom flashed is that usually the tuner takes the gauge at face value and doesn't attempt to use boost as a tuning variable, so if the gauge reads low the car is going to be slower after the tune than if it had a more accurate gauge.

propellerhead

iTrader: (3)

Rich, PM me if you're interested in swinging by my house sometime this weekend. I'll be working out in the garage anyway.

We can compare your Defi against my Autometer w/ the GM 3bar sensor and my AEM 3.5bar against the pressure gauge I bought from McMaster. It's supposedly accurate to +/-2% at 30psi. We can tee them all together and get a simultaneous reading. I need to do this regardless to check the calibratation of my AEM sensor against the settings in my EMS.

FWIW, the mechanical Defi boost gauge I bought was bad right out of the box. I ended up returning it and sticking with the Autometer.

nj1266

iTrader: (6)

I know this is old, but I will bring it back from the dead since I have a realted question/issue. I am currently running an LM-1 Innovate and I have a GM 3 bar MAP sensor attached to log boost. Before this, I got a Defi D boost gauge.

I found that the Defi D reads 1-1.5 psi higher than what the LM-1 logs. I have done a good caliberation on the MAP sensor. 0v=-14.7psi and 5v=31.1 psi. The voltage with the ignition on and engine off is 1.6v=0psi. These numbers a pretty much inline with what other sources that use the GM 3 bar sensor have found.

Just this weekend I installed an XD-16 universal programmable gauge from Innovate. I hooked it up to my LM-1 and set it to read boost. I used the same calibration as above.

The problem is that when I am at idle the gauge cannot read -18-20 inhg like the Defi guage used to since the 3 bar map sensor can only go as low as -14.7 inhg. The only way to get around this is to get a higher bar map sensor, either the AEM 3.5 bar or the AEM 5 bar.

Bujt reading this thread made me concerned about the accuracy of the AEM sensors. Has there been any resolution the the OP issue?