Hypergear Turbochargers and High flow Services Development thread

[SargeRX8]

My cold starts idle at around 10 on my wideband. I kind of actually can't stand the lean popping but I always thought it was something which shouldn't be happening. My car is sucking alot of air, -95 according to my profec b. My old car sat on around 85. When this one idles at 85, I know I popped off a vac line somewhere.

Ill take away some fuel and see what she does.

[Rolls]

-95 what?

[zebra]

decibels?

-95 on the Richter scale lol

[Super Drager]

95kpa maybe?

[SargeRX8]

I have no idea. It reads positive boost, for example, as 100 which is 10.0psi. 155 would be 15.5psi. It reads vacuum as -95 on idle, -50 maybe on cruising, so I have nfi.

[DVS JEZ]

9. 5

[Trozzle]

95 x 10^2?

THAT'S.....

OVER......

9000!!!!!!!!!!!!!!!!!!!

[Rolls]

I have no idea. It reads positive boost, for example, as 100 which is 10.0psi. 155 would be 15.5psi. It reads vacuum as -95 on idle, -50 maybe on cruising, so I have nfi.

Most likely -9.6mmHg then, that is fairly low. My skyline reads about negative 14-15 and negative 20 when backing off at higher rpm.

[DVS JEZ]

I dont think its the same as most gauges. Im having a mental blank but the dyno shows 9.5vac on most skylines. Even mine but my gauge shows -20 vac

[SiR_RB]

I've always wondered why my Profec b shows -99 while idling ?

And it's been pressure tested few months back and there are no leaks?

[Rolls]

Might be inches of mercury and not millimeters, and hence -0.99 inches, but that = -25mmHg which is far too high vacuum.

I'm stumped, it should be either of these units, I don't even know what else you can measure vacuum in. It is possible that 9.9 is just the maximum reading and it can't read any higher vacuum than that, when you back off at high revs does it read a number higher than 99 ?

[SargeRX8]

99 is the highest number it reads in negative pressure, vacuum. Then it bounces back to idle. My other boost gauge shows -20 vacuum when on idle. For me I ignore these figures. I listen to the engine and I can hear if it's idling right and feel it through that chassis. Feels good as is.

[discopotato03]

It works like this .

You can't measure a vacuum because it is nothing zip zero zilch . Anything abouve a total vacuum is positive pressure even if it isn't as high as sea level atmospheric pressure here on earth .

The confusion exists because cork head humans got in the habit of measuring air pressure using two different base lines or datums .

1) Absolute Pressure Psi"a" . The correct way is to say a total vacuum is zero and anything above is positive pressure and it puts sea level airpressure at around 100 kpa/1000 millibars/14.7 psi (same). Some engine management systems read off absolute pressure with a manifold pressure sensor so 0 would be a total vacuum and 100 kpa sea level atmospheric pressure . Abouve 100 kpa is said to be positive pressure ONLY because its higher than atmospheric pressure . Anything from 1 to infinity is positive compared to absolute 0 .

2) Gauge Pressure Psi"g" . This is where pressure is referenced using sea level air pressure as 0 . When you have a compound gauge it trys to show you pressure thats lower than its 0 when the pressure is lower than atmospheric . They are really just a means of making a distinction between atmospheric pressure and anything thats added to it .

The silly thing is gauge pressure can make people think you can have a negative pressure when in fact technically speaking you can't have less than nothing .

From a tuning perspective I think absolute pressure (psia) is better to use because the graduations rising from absolute zero are easier to comprehend than ones rising either side away from an atmospheric pressure 0 datum .

Next time you look at a turbos compressor map pay attention to the pressure ratio (PR) scale . Because these pressures are a ratio of anything above atmospheric pressure to atmospheric pressure they will say for example PR = 2 when a compound guage shows 100 kpa/15 psi . This is because the first 1 bar (bar means barometric sea level air pressure) is just this and the second bar is the pressure above atmospheric .

An absolute pressure gauge would show atmospheric pressure as 100 kpa/15 psi and the second bar as 200 kpa/30 psi .

A .

[Rolls]

Also explains why 20psi with all factors the same isn't double the air of 10psi, it is actually 24.7 and 34.7 psi, so a ~1.3x increase in air, not 2x increase in air.

And explains why you make less power the higher up a mountain you go.

Edited December 10, 2011 by Rolls

[discopotato03]

And the reason why it does is because in absolute pressure terms 0 doesn't change .

Gauge pressure sets 0 at 100 kpa absolute but atmospheric pressure changes with weather and altitude .

A .

[Trozzle]

ALL THIS SERIOUS DISCUSSION IS PUTTING PRESSURE ON MY BRAINZ

[Kenna802]

hey not sure if in right thread but since i have a hypergear turbo i thought id ask My atr43g3 turbo run at 18psi straight from the actuator but when i replaced the head gasket the exhaust cam was found to be 2 teeth out. Since i have put them back to proper timing car now boosts at 15psi Just wondering if thats happened to anyone else?

[Rolls]

Less restriction, hence same airflow produces less boost. You are probably making the same power yes?

edit: You said exhaust cam not intake cam, it has now advanced the exhaust timing, hence less energy is wasted out the exhaust, the turbo then sees less energy and spools less hence less boost.

Makes sense to me, your car is probably running much efficiently, however it is probably slightly laggier in regards to boost response, it will flow better in the high rpm now though.

Your power curve will have shifted towards redline slightly, you will make more power though, that is if you get it retuned on 18psi, DEFINITELY get it retuned, the load points will have completely changed, you could be detonating driving it like that.

Edited December 10, 2011 by Rolls

[Kenna802]

Bugger another tuning session lol Makes sense though as the car is more lag down low but i haven't tried to feel whats up high

Also the tuner at the time overloaded the timing in the car by about 10 degress ( 35 degress at 6500 rpm ) I have backed timing off the whole chart down to 24 degress at 6500max after most of the spark plugs got destroyed with the head gasket.

[Rolls]

but i haven't tried to feel whats up high

Don't, seriously don't load it up on boost at all until you get the tune checked. Won't cost much to tweak it hopefully, just depends how out it is now.