Hacker383sc

I have an all stock 2016 Z06 A8 4000mi. What kind of boost gauge readings are you guys seeing at wot? Anyone know the stock psi rating? I have read that it is supposed to be around 9-9.5psi stock. If thats the case I seem to be a little low at 9psi at sea level. Ill check/swap the air filter out and prob put an aftermarket gauge on it. Lemme know. Thx guys

cheapthrills

I have read altitude effects boost. Where are you?
https://en.wikipedia.org/wiki/Superc...titude_effects

Oh and fasten your seatbelt

Higgs Boson

that's not a precise gauge

Toddiesel

Jesus bruh. You're doing a buck 24, holding your cell phone, taking a bunch of pics, with no seat belt on. Come on! And Higgs Boson (nice username btw) is correct. the stock boost gauge on any car is not going to be super accurate. I've seen mine go up to like 12 and i know it isn't that high. I barely hear any whine

Toddiesel

Geez. I mean, I ain't saying i haven't done 150+, but I'm wearing my seatbelt and I ain't running snapchat!

davepl

I checked, and a typical Bosch MAP sensor is rated +/- 1kPa, which is pretty damned accurate. The ECM clearly knows the absolute barometric pressure as well as the relative pressure.

Where'd you get the idea they're not precise? Or do you believe there is error between the sensor and gauge? Or are you asserting that the gauge display is manipulated (like Temp is) for the sake of the user?

I wouldn't try to parse a single PSI out of it, but I don't see why it'd be inaccurate beyond "hard to read".

Toddiesel

Not speaking for my particle friend (get it?) but I did agree with him, so I'll put in my $.02. I imagine stock gauges have come a long way in the last couple of decades, but back in my late teens in the late 90s/early 00s, everyone that had a boosted car had an aftermarket boost gauge and it always had a different reading than the stock boost gauge and everyone "knew" stock boost gauges were "garbage". Granted since this was in the 99-03 time frame, and most people had 5-10 year old cars, we're talking about 20+ year old technology

Higgs Boson

i said the gauge isn't precise, not the sensor isn't precise.

have you ever measured map directly and watched the gauge? there is a difference, the gauge is basically a dummy gauge, like a coolant gauge that only shows cold, normal, and overheating.

also, there are a ton of factors that will screw up how much boost you are making, we all know the throttle blade closes and opens based on the torque model to regulate airflow (not boost) and power. the boost solenoid can open the bypass valve and purge some boost, etc etc.

wagoetzmann

Boost Dash Indicator – Calibration

I obtained a new vacuum/boost gauge and verified it’s calibration using several known correct gauges before temporary installing it.
I teed this gauge to the supercharger’s by-pass valve’s backside or bottom line.
My car has a 2.31 top pulley.
I filmed a hit using launch control.
Temporary boost gauge 0 - 20 psi in 1 psi increments; dash indicator 0 to 15 psi in 1.5 psi increments.

At the hit the gauge went to 9.5 psi but the dash indicator only went to 4.5 psi, a factor of 2.11:1.
Top of 1st gear the gauge went to 12 psi but the dash indicator only went to 7.5 psi, a factor of 1.71:1.
Mid 3rd gear to gauge went to 11 psi but the dash indicator only went to 9 psi, a factor of 1.22:1.
Seems the longer the time factor the closer the more accurate the dash indicator got.

I also noticed the vacuum side was much closer to being accurate….
Temporary vacuum gauge 0 – 30 inhg in 2 inhg increments; dash indicator 0 - 15 psi in 2.5 psi increments.
(15 psi = 30.54”hg)

davepl

That's what I meant by "manipulated for the sake of the user (like Temp)". That said, you'd think if the gauge is going to embellish it would do so to spec, not below it.

If Marketing conspired to design the gauge they'd make sure it read peak advertised boost as per the brochure.

If Legal conspired to design the gauge they'd make sure it only ever understated boost, never overpromising.

If the Race team conspired to design the gauge, it'd point up at nominal boost so it's easy to read at a glance.

If Engineering conspired to design the gauge it sure wouldn't be 15 psiu divided into 10 tick marks, because that's weird.

Have I ever closely watched the gauge and compared to MAP data? No, being a street-driven car, when it's in full boost I need to be looking where I'm going... unlike a manual, I can't hold a high load in a gear because of kickdown, so if I'm at full boost, I'm moving.

Higgs Boson

I don't know why they do what they do. I didn't mean watching the computer while you drive, you can save the data and look later.

wagoetzmann

Question - Which parameter gives correct boost pressure? Boost inHG nor MAP KPA/PSI don't. GM must have a multiplier factor they use....just to confuse everyone?

Warp Factor

I don't know about him, but I make part of my living from calibrating gauges, and they can be way far off, regardless of the manufacturers claims, even when they claim to be "lab grade" or "National Measurement Institute certified".

Higgs Boson

Manifold Pressure - Hi Res
in HPTuners is the correct one for the E92

3 Z06ZR1

11.9 on the dyno with halltech intake and headers funny thing boost went up a 1/2 pound with the headers but who looks at the boost gauge anyway?

Poor-sha

Run PDR, download the file, and open it in the Cosworth Pi Toolbox. My car is running around 11 psi at peak. There is an "intake boost pressure" channel that is actual psi and a separate "boost pressure indicated" which is just a percentage and I suspect is what is sent to the dash gauge. Even at 11.17 psi the indicated pressure value is only 54.9%.

Help setting up the toolbox is in this video:

Warp Factor

PSI or boost pressure, referenced to what? Ambient local atmospheric pressure at startup? Theoritical sea level pressure? PSI above a total vacuum?

Higgs Boson

you must log Baro and MAP - Hi Res and subtract and then you have a kpa you can convert to boost.

Poor-sha

Well the intake boost pressure is by default in kpa but the toolbox lets you convert it to other units and I chose psi since that is what everyone was discussing.

Higgs Boson

what i am saying is I don't recommend using the pids called "boost"

use Baro and MAP - Hi Res and do the math, say 164 kpa - 97 kpa = 67 kpa or 9.7 psi

the reason is many pids in the list are not measured, they are calculated or they are generic or they are legacy (meaning pulled forward from older generations). many spent a lot of time (over on HPT Forums) figuring out which were the ones worthy of logging and using, the rest are trash.

I am not saying that sometimes the other ones might make sense or calculate out properly, but even a broken clock is right twice a day.