Which is most accurate? Im getting different boost readings from all three. The RPD under WOT is hitting about 25. The factory boost gauge under WOT spikes to almost 27 and the scan gauge tops out at 22.7. I have 3bar maps. Anyone ever experience this?

 

Haven't paid much attention to mine.

I have the factory boost + RPD + Interceptor.

I do not have my Interceptor set to show boost.

They all get the info from the same source.

 

Yeah its got me bugged. I could not get the aeroforce to read more than 22.7 psi. Im not trying to blow my engine up but I was concerned with the spikes on the factory gauge. I have a 24 psi tune. The RPD is the closest with the reading at about 25 its hard to see accurately . Thats acceptable. I figured i would see what the scan gauge says and it wont go higher than stated. It hard to look at all 3 at once so I did WOT pulls for each. The factory boost gauge does come back down to about 24 but it hits 26 or 27 first. I know they get there info from the same source and its weird they all read different.

 

Perhaps the rpd has a touch of smoothing built into it.

I use hp tuners for logging so I rarely look at boost on any gauge. Too hard to read while wot

 

Mechanical will give you the truest boost level without lag from any of the normal gauges. The stock boost gauge is really slow to respond to anything and Aeroforce is going over the OBD2 which isn't quick either. RPD might be quicker, but I'd be surprised if it was as fast responding as my Autometer SportCompII.

 

Agreed. If you want near instant, true readings you have to go mechanical.

Since the RPD reads from the PCM I'm going to say there's that ever so slight delay just like the factory boost gauge.

 

In case you were curious just how much more sensitive and responsive mechanical is. This is a side by side of an Autometer Cobalt Boost gauge and the stock gauge in an SS/SC. At one point around 17 seconds, the mechanical peaks at 10psi while the stock is just swinging past 10in/hg of vacuum. Not my video.

 

Yup rpd and Aero force don't read the same on boost, heck mine are off like 1-2 mph if I have them both reading mph

 

The reason for that is 2 different data sources. Aeroforce is OBD2, RPD is over the GMLAN.

Here's a screen cap from the video at 18seconds showing the difference.

 

I don't think the Aeroforce can read over 22.7. I got rid of the factory gauge and got an electrical boost gauge. It goes to a boost sensor from manifold and electrical to the gauge. That or mechanical would be best. The stock gauge uses a calculation to tell boost where as mechanical is realtime boost, and electrical is similar, just converts pressure to electrical signal

 

I figured as much, mechanical is the always way to go. Ill be picking one up and replacing the factory boost gauge. Im just shocked how all 3 have different readings with the stock boost gauge being the highest. Either way thanks for the clarification and videos. Guess I have to buy a Christmas present for myself.

 

Autometer SportCompII matches the stock gauges the best IMO. You'll need to add a resistor to knock the brightness down.

 

Since the RPD feeds off the LAN which gets it's pressure readings off the MAP sensor and the factory boost gauge gets fed it's own signal out of the PCM which also feeds off the same MAP sensor I presume then I have to wonder how accurate logging with HPT is as far as boost goes......

Personally, I don't really care how much boost my car makes. All that really matters to me is if it's pulling hard, IAT's in check, and no KR. The boost reading itself is just a guideline for me to notice if something's wrong.

 

Perhaps HPT traverses the lowspeed GMLan to the highspeed side and has information passed back from the MAP? IDK.

If you wanted to see if they feed off the same sensor, probably do, you can short pin 1 and 3 on the MAP sensor with the key on and engine off, should shoot to like 23 or whatever 5v gets you, shouldn't harm anything but might throw a code

 

I was actually trying to look that up. It crossed my mind also. Thats what got me thinking of all this when the boost gauge was reading high. I know I was logged at 24psi. I dont know alot with these cars but I am learning quick. I agree with your statement. Christ, I have enough reading between 3 gauges to know if something is really wrong with the car. The car pulls Hard enough for me. My IAT's are good most of the time (just not in Manhattan traffic). As far as knock, I see it only when I let the fuel run low (1/4 or less) sporadically, I figure this is the crap from the gas settled to the bottom and the octane is dipped a bit. I only ever run 93. As far as the boost gauge, Im torn between the Carbon Fiber series, Sport Comp and Sport Comp II Decisions.......

 

They have one that Looks pretty well stock, it's. Gm series

 

If you want the stock look, the Sport Comp II is the way to go. LED backlighting and a good looking needle/gauge face. They sell a bowtie one as well if you're into that, not for me.


Regular Sport Comp is front lit and the needle looks cheaper.



CF series doesn't match at all, but if you like it you like it.


The GM series doesn't match our needles, those gauges match closer to the 1990's Chevy trucks.

 

I went with the sport comp II Bowtie VAC/BOOST. I like the extra red in the gauge. It matches my Aeroforce which has the red SS logo. I didnt see that one at first. Im glad you guys brought it up. Thanks for the help. Hopefully it comes by the weekend. I'd like to get it in and see what it reads.

 

Full mechanical?

 

There is a different Gm one I can't seem to find anymore that did match , even had the red around the edge.

 

Yup, The same one you have posted with the bowtie except it has the vacuum with it. Tom, I didnt see the other one either. That would have been nice. Here is the pic of the one i got. what do you think?

 

The RPD tops out at 25.5psi and the 3 bar maps can log up to 32.2psi. So if the stock gauge is hitting 27psi I'd log it to make sure because that is too much boost for the stock turbo. I like to tune up to 24psi on the stock K04

 

After I install the gauge if its still hitting 27psi, ill get it checked out. It seems to spike then drop to 24 or so. Until then, im not going to push it to hard. I have NO knock right now and never had any above 3000. I sometimes get it down low when I feather the throttle or initial take off. Keeping the tank above 1/4 seems to eliminate it.

 

Running really high boost requires less timing and both these factors cause higher EGTs which is bad. What timing are you running at WOT?

 

I had intended to post the vacuum ones, oops.
I got that same one except without the bowtie. Quality piece. Do yourself a favor and pickup a pack of resistors and a rheostat. You're going to want to dial down the brightness on that sucker. I don't recall what resistance I ended up at, but I stuck the rheostat inline with the gauge and dialed it down to where it was even with how bright I like my dash lights and then measured that to solder in some resistors instead of leaving the rheostat.