More boost when cold outside
12-10-2002 | 10:29 AM
#1
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Posts: n/a
More boost when cold outside
Not really a question, more of an observation.
I have a Blitz Spec-R EBC and I have noticed when it is really cold outside the boost is higher. Not spiking, just higher. For example:
a setting of 25% when it's warm out holds about 8psi, the same setting when it's quite cold outside holds 10 psi.
I understand the concept of air density when warm and cold. I just didn't know that it would effect the controller?
psi is psi and something that is controlling it shouldn't care what temp. it is right?
Then I start thinking about tire preasure...when the tires are hot the psi is higher than when they are cold. BAH!
-disco
I have a Blitz Spec-R EBC and I have noticed when it is really cold outside the boost is higher. Not spiking, just higher. For example:
a setting of 25% when it's warm out holds about 8psi, the same setting when it's quite cold outside holds 10 psi.
I understand the concept of air density when warm and cold. I just didn't know that it would effect the controller?
psi is psi and something that is controlling it shouldn't care what temp. it is right?
Then I start thinking about tire preasure...when the tires are hot the psi is higher than when they are cold. BAH!
-disco
12-10-2002 | 10:50 AM
#2
For the given setting, when the air becomes colder more dense, the same duty cycle will produce more boost. Happens to us all. Use a second channel for a cold air max boost setting. That's what I do.
Ken
Ken
12-10-2002 | 08:42 PM
#3
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I think the reason for this being, since cold air is more dense, when it goes into the turbo and heats up it expands. Since there are more oxygen molecules in the same amount of volume of cold air as there are in warm air, when they reach a common temperature, there will be more boost from the cold air.
12-11-2002 | 12:24 PM
#5
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Thinking in volume..... warmer, thinner air is softer.....colder, thicker air is harder. More pressure on manifold and boost sensor when its cold. Parts per million.... if you got more little molecules in a bag and squeeze them, you're gonna feel more resistance- higher boost. Less of them and they'll squish easier- less boost.
12-11-2002 | 05:52 PM
#6
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Posts: n/a
hmmm.
Ok, right.
So what any given turbo is capable of is not a definite, but rather a constantly variable amount of boost depending on air temp. Correct? Because the boost controller setting is a percentage of what the turbo is capable of producing, yes?
So to say that our stock turbo, or any turbo for that matter is only capable of "XX"psi would have to be a false statement. Provided with the right air temp. I should be able to get my turbo to make pretty much any amount of boost I want, within the walls of reality, less the ecu/fuel restriction that is.
Interesting...
-disco
So what any given turbo is capable of is not a definite, but rather a constantly variable amount of boost depending on air temp. Correct? Because the boost controller setting is a percentage of what the turbo is capable of producing, yes?
So to say that our stock turbo, or any turbo for that matter is only capable of "XX"psi would have to be a false statement. Provided with the right air temp. I should be able to get my turbo to make pretty much any amount of boost I want, within the walls of reality, less the ecu/fuel restriction that is.
Interesting...
-disco
12-11-2002 | 10:35 PM
#7
VIP Member
Joined: Nov 2002
Posts: 79
From: colorado
standard temp and pressure
If you look at the compressor maps you will see that the manufacturers always specify a set of temp and pressure conditions for the map.
This assumption is usually ignored by the average catalog browser.
Yes within limits your correct.
Turbos are sensitive to the temperature pressure conditions at their inlet. (actually the density of the gas entering the inlet)
Increase the density at the inlet and you increase the mass flow of the turbo by a similar amount, all else remaining the same.
As a result of this your waste gate setting is only accurate for a narrow range of temperatures and barometric pressures and altitude. Large changes in any of those will change the actual boost you will see at the manifold.
Larry
This assumption is usually ignored by the average catalog browser.
Yes within limits your correct.
Turbos are sensitive to the temperature pressure conditions at their inlet. (actually the density of the gas entering the inlet)
Increase the density at the inlet and you increase the mass flow of the turbo by a similar amount, all else remaining the same.
As a result of this your waste gate setting is only accurate for a narrow range of temperatures and barometric pressures and altitude. Large changes in any of those will change the actual boost you will see at the manifold.
Larry
12-12-2002 | 12:15 PM
#8
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Posts: n/a
Dump your EBC and get a UTEC. Ver 2.5B of their software has closed loop boost control. With this you set the PSI you want at a certain RPM/TPS threashold and the computer takes care of the wastegate settings dynamically (then you don't have to retune every time you change elevation, temperature, humidity, etc). Plus you get all the other cool feauture of the UTEC (fuel and spark control, data logging, user programmibility, etc, etc.).
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