StolenTeg

Does the psi really drop if it get warmer let say about 40 degree to about 70 degree? my friend car was boosting 10 psi but now it only hit 8 psi and he said it because of the cold air is denser therefore it run higher psi.
but as i understand it, the psi shouldnt changed is just mean there is more oxygen particle in the air when it colder and less when it hotter/humid therefore making more power at colder air but the psi itself shouldnt drop when it seeing hotter air.

mrbsponge

yep, my car was tuned in 90 degree weather then i moved and the winters here got about 30 at night. i was tuned at 18psi, but here in the winter it went to about 21-22

colder air is more dense, you will also run a bit richer in the warmer days

purpleh22

Right. Pressure should be pressure. A boost controller would be regulated by pounds of pressure not air density. Would it reach maximum pressure sooner if the air was colder/more dense? Would the difference be noticible? - Don't Know???

GaRn

On supercharged cars this is more common..

Heat might affect your wastegate spring which could cause this..

If your car is tuned properly (aka IAT multipliers) then it should run pretty much the same regardless of outside temp..

adseguy

pressure is pressure

P*V=n*R*T

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GaRn &raquo;</TD></TR><TR><TD CLASS="quote">

Heat might affect your wastegate spring which could cause this..

</TD></TR></TABLE>

I agree with that. I've had problems on EXTREMELY cold days. Problem is that the colder the air the more fuel is need so if you are already running ahigher PSI on accident and now you don't have IAT control then that's where problems occur , but also the reason why people tune at 12.0 AFR so if it goes to 12.5+ the motor will most likely be fine

tgreaves

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mrbsponge &raquo;</TD></TR><TR><TD CLASS="quote">yep, my car was tuned in 90 degree weather then i moved and the winters here got about 30 at night. i was tuned at 18psi, but here in the winter it went to about 21-22

colder air is more dense, you will also run a bit richer in the warmer days</TD></TR></TABLE>

Thats what the ait sensor is for.. Damn I just love my AEM EMS, perfect air/fuel no matter what the tempeture is..

SOHCD16y8

unfortunately uberdata doesnt correct for that. wish I could afford AEM

SOHC_MShue

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHCD16y8 &raquo;</TD></TR><TR><TD CLASS="quote">unfortunately uberdata doesnt correct for that. wish I could afford AEM</TD></TR></TABLE>
uberdata runs off the stock ecu code. There are always corrections for that. However they may not correct the right amount when you have larger injectors than it was setup for. Uberdata does have adjustable corrections for this now as well as crome. Cromes corrections have gotten pretty advanced now.

SOHCD16y8

yeah, i dont believe version ost2 has the correction factor though

vtec.dc2

i had this from day one going turbo.. and why i get my car tuned during winter (hondata doens't adjust like aem does). i deal with psi changes by increasing boost levels as the weather gets warmer

tgreaves

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vtec.dc2 &raquo;</TD></TR><TR><TD CLASS="quote">i had this from day one going turbo.. and why i get my car tuned during winter (hondata doens't adjust like aem does). i deal with psi changes by increasing boost levels as the weather gets warmer</TD></TR></TABLE>

Do you have your boost reference for the wastegate hooked up to the intake manifold or the compressor housing? If hooked to the intake manifold then the outside temps dont make a difference on the boost that your running, its always the same..

StolenTeg

I got a vacuum manifold T off at the brake booster line, so my psi shouldnt be going up or down when it hotter or colder right?

adseguy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StolenTeg &raquo;</TD></TR><TR><TD CLASS="quote">I got a vacuum manifold T off at the brake booster line, so my psi shouldnt be going up or down when it hotter or colder right?</TD></TR></TABLE>

It still might, but only 1-2PSI which isn't too much of a concern

SOHC_MShue

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHCD16y8 &raquo;</TD></TR><TR><TD CLASS="quote">yeah, i dont believe version ost2 has the correction factor though</TD></TR></TABLE>
yes it does. Any version has a stock correction factor built into the ecu code. Also yes you can add the editable correction factor tables script to ost2. Just gotta add it in the folder.

Weston

Not only does the cooler and more dense air have an effect on turbo efficiency, but it also affects your boost gauge itself... Boost gauges show relative pressure, so when the air inside the line is more dense than the air inside the car, it will show positive pressure.

What I'm saying is that the inside of your car is 70 degrees or so with the heater on, but it's 30 degrees outside. The boost going to the gauge is 30 degrees, but the gauge is comparing it to the pressure of air that's 70 degrees, so it will read slightly higher. Combine that with the benefits of colder air to turbo efficiency, and you see another PSI or two in the winter.

vtec.dc2

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tgreaves &raquo;</TD></TR><TR><TD CLASS="quote">

Do you have your boost reference for the wastegate hooked up to the intake manifold or the compressor housing? If hooked to the intake manifold then the outside temps dont make a difference on the boost that your running, its always the same..</TD></TR></TABLE>

intake manifoldopen

Tony the Tiger

It's usually the wastegate spring that gets softer as heat builds up... On the same tune, I get about 19-20 psi during a cold winter night, but on the same tune, I get about 16-17 psi on a warm summer day. Boost also comes a lot slower when everything has heated up compared to say a colder engine.

rhettster

It's weird because your wastegate should be the only thing that limits how much boost you run. Pressure is pressure, and if the wastegate spring is set to fully open at 10PSI, then it shouldn't matter what the temperature is.

I've heard the "heat makes the wastegate spring softer" theory before, but with the wastegate dealing with so much heat from the exhaust already, it seems funny that slightly warmer ambient temps would matter.

The boost gauge theory is plausible if your friend has a mechanical boost gauge. Mine is electronic, and the air temps have never affected my boost level. &gt;shrugs&lt;

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rhettster &raquo;</TD></TR><TR><TD CLASS="quote">I've heard the "heat makes the wastegate spring softer" theory before, but with the wastegate dealing with so much heat from the exhaust already, it seems funny that slightly warmer ambient temps would matter.
&gt;shrugs&lt;</TD></TR></TABLE>

It doesn't have anything to do with air temperature. A cold engine makes a bit more boost than a hot one from my findings. I can still have my boost vary with the same air temps, but once the engine heatsoaks (or exhaust/manifold/turbo/wastegate heatsoaks), I get less boost.

rhettster

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">

It doesn't have anything to do with air temperature. A cold engine makes a bit more boost than a hot one from my findings. I can still have my boost vary with the same air temps, but once the engine heatsoaks (or exhaust/manifold/turbo/wastegate heatsoaks), I get less boost. </TD></TR></TABLE>

That makes sense, but then what does the air temp have to do with anything? Once the car is warmed up and you're boosting, you're going to heatsoak whether it's 40 degrees or 70 degrees outside.

Are you saying that your car never fully warms up if it's cold outside?

SlwGsr

hes not saying it doesnt fully warm up. just the intake charge is going to be overall a bit colder all the way through. by the time 40 degree air gets to the tb is going to be overall a bit cooler then a 70 degree charge. the intercoolers going to be cooler in general which will help cool the charge down also. either way. when its colder outside your going to make more power per psi then when its warmer

rhettster

Sure, you're going to be getting denser air if it's cold out. And that'll make more power.

But that's not the question. The question is why this guy's boost gauge shows 2-3 PSI less boost when its warmer outside.