turbo: altitude vs hp
05-04-2005, 04:16 PM
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turbo: altitude vs hp
Everyone says altitude is going to have a direct effect on your hp, but i really dont see why on a turbo'd vehicle. The amount of air your forcing in is regulated by your wastegate. Your wastegate does not care at what altitude your at.
whether your at 20,000 feet on sea level, if its the same temperature out, 10psi of air is the same.
The only reason the air is thinner at higher altitudes is because there is less atmospheric pressure.
The only thing that would be effected is that your turbo would have to work harder to make the same power. So unless your turbo is maxed on its effeciency, i dont see how you would lose any power and i dont see how your a/f would change
its not like theres less oxygen at higher altitudes, theres just less air.
whether your at 20,000 feet on sea level, if its the same temperature out, 10psi of air is the same.
The only reason the air is thinner at higher altitudes is because there is less atmospheric pressure.
The only thing that would be effected is that your turbo would have to work harder to make the same power. So unless your turbo is maxed on its effeciency, i dont see how you would lose any power and i dont see how your a/f would change
its not like theres less oxygen at higher altitudes, theres just less air.
05-04-2005, 04:49 PM
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Re: turbo: altitude vs hp (DaZman69)
Doesnt thinner air, mean less air/oxygen being pulled in at a time? You will have to work your turbo harder to reach the same PSI that you would at lower altitudes. In otherwords you will make less power.
It has a much worse affect on Naturally Aspirated Engines compared to FI
It has a much worse affect on Naturally Aspirated Engines compared to FI
05-04-2005, 07:29 PM
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Re: turbo: altitude vs hp (95GSRTT)
no...thats what im explaining, you will make the same power, your turbo will just have to spin faster because of the decreased pressure, you will not have anymore exhaust back pressure on the hot side
your boost is controlled by a mechanical device....a spring
your boost is controlled by a mechanical device....a spring
05-04-2005, 07:38 PM
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Re: (BoostfedEK4)
There is actually less air. So if you have one cubic foot of air at sea level, there is less air in that cube box at altitude.
Turbo cars are not effected as much as N/A and supercharged cars are.
Turbo cars are not effected as much as N/A and supercharged cars are.
05-04-2005, 07:46 PM
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Re: (Mario.)
correct. Only the spool time will change, and since you are probably in colder weather it may benifit you a little bit in terms of charge density. Remember PSI does not = CFM.
05-04-2005, 07:46 PM
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Re: turbo: altitude vs hp (DaZman69)
The air is less dense, therefore your turbo has to grab a little more, the atmoshperic pressure is lower so it directly effects hp, you can counter this however, by turning up the PSI on your turbo
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05-05-2005, 07:04 AM
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Re: turbo: altitude vs hp (knockout)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by knockout »</TD></TR><TR><TD CLASS="quote">The air is less dense, therefore your turbo has to grab a little more, the atmoshperic pressure is lower so it directly effects hp, you can counter this however, by turning up the PSI on your turbo </TD></TR></TABLE>
wrong
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mario. »</TD></TR><TR><TD CLASS="quote">There is actually less air. So if you have one cubic foot of air at sea level, there is less air in that cube box at altitude.
Turbo cars are not effected as much as N/A and supercharged cars are. </TD></TR></TABLE>
you dont understand
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BoostfedEK4 »</TD></TR><TR><TD CLASS="quote">the air is less dense in higher areas and vise versa. same as colder air is more dense than hot air.</TD></TR></TABLE>
nor do you
IT DOESNT MATTER HOW THIN THE AIR IS, 6psi of air at any sea level is the SAME DENSITY....(same temperature of course)
</TD></TR></TABLE>wrong
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mario. »</TD></TR><TR><TD CLASS="quote">There is actually less air. So if you have one cubic foot of air at sea level, there is less air in that cube box at altitude.
Turbo cars are not effected as much as N/A and supercharged cars are. </TD></TR></TABLE>
you dont understand
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BoostfedEK4 »</TD></TR><TR><TD CLASS="quote">the air is less dense in higher areas and vise versa. same as colder air is more dense than hot air.</TD></TR></TABLE>
nor do you
IT DOESNT MATTER HOW THIN THE AIR IS, 6psi of air at any sea level is the SAME DENSITY....(same temperature of course)
05-05-2005, 07:06 AM
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Re: turbo: altitude vs hp (DaZman69)
your turbo will just have to spin faster, it will not work harder
what i mean is the exhaust back pressure will be the same/really really close
what i mean is the exhaust back pressure will be the same/really really close
05-05-2005, 10:04 AM
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well your right, a turbod car shouldnt lose power due to less atomspheric pressure. Except you fergot to factor in one thing....less dense air at high altitudes means less intercooler effiency, so if your on that fine line between a max performance tune and blowing up ur motor, your car wont be able to hack it at higher altitudes
05-05-2005, 10:30 AM
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Re: (z6)
Wow. Okay, there are two types of pressure.
There is "absolute pressure", and "gage pressure". Absolute pressure is usually measured in bar, where 1.15 bar (14.7 PSI) = zero boost pressure. However, when you refer to "6 psi of boost" you are referring to gage pressure, which is pressure above atmospheric.
Let's say at sea level the abs. pressure is 14.7 PSI. On top of Mt. Everest it is about 70% of that, or about 10.3 PSI absolute. Now imagine you have a turbo with a 6 PSI wastegate and run it at these two locations.
Since the wastegate uses the atmosphere as reference, it can only create a gage pressure of 6 PSI. So at sea level, this equates to 20.7 PSI absolute, and on Mt. Everest it is 16.3 PSI absolute.
So the same car, with the same turbo, and the same wastegate settings, will obviously see more power at sea level. To see the same amount of power, the car on Mt. Everest would have to set his wastegate at 10.4 PSI (to see 20.7 abs.)
There is "absolute pressure", and "gage pressure". Absolute pressure is usually measured in bar, where 1.15 bar (14.7 PSI) = zero boost pressure. However, when you refer to "6 psi of boost" you are referring to gage pressure, which is pressure above atmospheric.
Let's say at sea level the abs. pressure is 14.7 PSI. On top of Mt. Everest it is about 70% of that, or about 10.3 PSI absolute. Now imagine you have a turbo with a 6 PSI wastegate and run it at these two locations.
Since the wastegate uses the atmosphere as reference, it can only create a gage pressure of 6 PSI. So at sea level, this equates to 20.7 PSI absolute, and on Mt. Everest it is 16.3 PSI absolute.
So the same car, with the same turbo, and the same wastegate settings, will obviously see more power at sea level. To see the same amount of power, the car on Mt. Everest would have to set his wastegate at 10.4 PSI (to see 20.7 abs.)
05-05-2005, 11:21 AM
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Re: (beepy)
well thankyou for knowing what your talking about beeby
i realize what you are saying....but your 6 psi of gage pressure is not really being referenced to the atmosphere. Its controlled by a spring. The spring has the same resistance even if your in space
i realize what you are saying....but your 6 psi of gage pressure is not really being referenced to the atmosphere. Its controlled by a spring. The spring has the same resistance even if your in space
05-05-2005, 11:23 AM
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Re: (z6)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by z6 »</TD></TR><TR><TD CLASS="quote">well your right, a turbod car shouldnt lose power due to less atomspheric pressure. Except you fergot to factor in one thing....less dense air at high altitudes means less intercooler effiency, so if your on that fine line between a max performance tune and blowing up ur motor, your car wont be able to hack it at higher altitudes</TD></TR></TABLE>
wow good thinking....but i dont see it making a noticable different, i'm kinda putting that in an irrelevant category, but its definatly true
wow good thinking....but i dont see it making a noticable different, i'm kinda putting that in an irrelevant category, but its definatly true
05-05-2005, 11:41 AM
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Re: (DaZman69)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 »</TD></TR><TR><TD CLASS="quote">well thankyou for knowing what your talking about beeby
i realize what you are saying....but your 6 psi of gage pressure is not really being referenced to the atmosphere. Its controlled by a spring. The spring has the same resistance even if your in space</TD></TR></TABLE>
Not in all cases.
The spring presses against a diaphragm. When the pressure on the opposite side of the diaphragm reaches the point where it overcomes the spring pressure, the valve opens. Simple enough right?
Now what about the "invisible" spring? What is it? It is air pressure on the spring side of the diaphragm. If there is less air pressure on the spring side of the diaphragm then it will take less pressure on the opposite side of the diaphragm to open the valve.
All the spring can do is regulate the "differential pressure" that is required to open that valve.
Now if the sprung side of your wastegate is "sealed" the atmospheric pressure will have no effect on the actual pressure that the wastegate will regulate.
If it is not sealed (dual port wastegates), you will get less pressure when the atmospheric pressure drops.
Now if you use an electronic boost controller that uses a "MAP" sensor to detect boost it doesn't matter what altitude you are at because "MAP" sensors reference Absolute pressure (PSIA) and it will control your boost at what ever level you set it to.
i realize what you are saying....but your 6 psi of gage pressure is not really being referenced to the atmosphere. Its controlled by a spring. The spring has the same resistance even if your in space</TD></TR></TABLE>
Not in all cases.
The spring presses against a diaphragm. When the pressure on the opposite side of the diaphragm reaches the point where it overcomes the spring pressure, the valve opens. Simple enough right?
Now what about the "invisible" spring? What is it? It is air pressure on the spring side of the diaphragm. If there is less air pressure on the spring side of the diaphragm then it will take less pressure on the opposite side of the diaphragm to open the valve.
All the spring can do is regulate the "differential pressure" that is required to open that valve.
Now if the sprung side of your wastegate is "sealed" the atmospheric pressure will have no effect on the actual pressure that the wastegate will regulate.
If it is not sealed (dual port wastegates), you will get less pressure when the atmospheric pressure drops.
Now if you use an electronic boost controller that uses a "MAP" sensor to detect boost it doesn't matter what altitude you are at because "MAP" sensors reference Absolute pressure (PSIA) and it will control your boost at what ever level you set it to.
05-05-2005, 12:09 PM
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Re: turbo: altitude vs hp (DaZman69)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DaZman69 »</TD></TR><TR><TD CLASS="quote">your turbo will just have to spin faster, it will not work harder
what i mean is the exhaust back pressure will be the same/really really close</TD></TR></TABLE>
The faster the turbo has to spin, the harder its working. You know how to read a compressor map, right? (seriously, not trying to insult your intelligence here) Well look at the different speeds the turbo has to spin. The faster it goes the more out of its efficiency it gets, just like a small turbo at 20psi wont produce the same power numbers as a large turbo at 20psi. The larger turbo is much more efficient at producing the same pressure which equals more power.
what i mean is the exhaust back pressure will be the same/really really close</TD></TR></TABLE>
The faster the turbo has to spin, the harder its working. You know how to read a compressor map, right? (seriously, not trying to insult your intelligence here) Well look at the different speeds the turbo has to spin. The faster it goes the more out of its efficiency it gets, just like a small turbo at 20psi wont produce the same power numbers as a large turbo at 20psi. The larger turbo is much more efficient at producing the same pressure which equals more power.
05-05-2005, 05:47 PM
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Re: (z6)
I like the info about the size turbo, SO this is ahy the stock eclipse guys running 30psi arent blowing stuff up? But then isnt 30psi still 30 psi to the engine if the boost gauge is reading it?
05-05-2005, 06:58 PM
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Re: (GForceInteg)
there is not less AIR there is less oxygen in that air.. at sea level there is i think around 20 % oxygen in our air.. up there has less oxygen.. it will still be at 10psi both places but the higher alt will be slower because there is less oxygen.. and your **** will run rich..
05-05-2005, 09:04 PM
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Re: turbo: altitude vs hp (Unsivil_audio)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Unsivil_audio »</TD></TR><TR><TD CLASS="quote">
The faster the turbo has to spin, the harder its working. You know how to read a compressor map, right? (seriously, not trying to insult your intelligence here) Well look at the different speeds the turbo has to spin. The faster it goes the more out of its efficiency it gets, just like a small turbo at 20psi wont produce the same power numbers as a large turbo at 20psi. The larger turbo is much more efficient at producing the same pressure which equals more power. </TD></TR></TABLE>
yes, it will have to spin faster, but...it will not create more exhaust back pressure.
the only time it will be of concern is if your turbo is at its max effeciency. Then yes it will definatly effect your hp.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TrueNorthStar »</TD></TR><TR><TD CLASS="quote">
Not in all cases.
The spring presses against a diaphragm. When the pressure on the opposite side of the diaphragm reaches the point where it overcomes the spring pressure, the valve opens. Simple enough right?
Now what about the "invisible" spring? What is it? It is air pressure on the spring side of the diaphragm. If there is less air pressure on the spring side of the diaphragm then it will take less pressure on the opposite side of the diaphragm to open the valve.
All the spring can do is regulate the "differential pressure" that is required to open that valve.
Now if the sprung side of your wastegate is "sealed" the atmospheric pressure will have no effect on the actual pressure that the wastegate will regulate.
If it is not sealed (dual port wastegates), you will get less pressure when the atmospheric pressure drops.
Now if you use an electronic boost controller that uses a "MAP" sensor to detect boost it doesn't matter what altitude you are at because "MAP" sensors reference Absolute pressure (PSIA) and it will control your boost at what ever level you set it to.
</TD></TR></TABLE>
i have definatly took that into consideration....your wastegate is not sealed, and the atmospheric pressure would effect when it opens.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by konigturbocivic »</TD></TR><TR><TD CLASS="quote">there is not less AIR there is less oxygen in that air.. at sea level there is i think around 20 % oxygen in our air.. up there has less oxygen.. it will still be at 10psi both places but the higher alt will be slower because there is less oxygen.. and your **** will run rich..
</TD></TR></TABLE>
i also thought about that....where did you get that info from. I didn't think the percentage of oxygen was any less at higher altitudes
The faster the turbo has to spin, the harder its working. You know how to read a compressor map, right? (seriously, not trying to insult your intelligence here) Well look at the different speeds the turbo has to spin. The faster it goes the more out of its efficiency it gets, just like a small turbo at 20psi wont produce the same power numbers as a large turbo at 20psi. The larger turbo is much more efficient at producing the same pressure which equals more power.
</TD></TR></TABLE>yes, it will have to spin faster, but...it will not create more exhaust back pressure.
the only time it will be of concern is if your turbo is at its max effeciency. Then yes it will definatly effect your hp.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TrueNorthStar »</TD></TR><TR><TD CLASS="quote">
Not in all cases.
The spring presses against a diaphragm. When the pressure on the opposite side of the diaphragm reaches the point where it overcomes the spring pressure, the valve opens. Simple enough right?
Now what about the "invisible" spring? What is it? It is air pressure on the spring side of the diaphragm. If there is less air pressure on the spring side of the diaphragm then it will take less pressure on the opposite side of the diaphragm to open the valve.
All the spring can do is regulate the "differential pressure" that is required to open that valve.
Now if the sprung side of your wastegate is "sealed" the atmospheric pressure will have no effect on the actual pressure that the wastegate will regulate.
If it is not sealed (dual port wastegates), you will get less pressure when the atmospheric pressure drops.
Now if you use an electronic boost controller that uses a "MAP" sensor to detect boost it doesn't matter what altitude you are at because "MAP" sensors reference Absolute pressure (PSIA) and it will control your boost at what ever level you set it to.
</TD></TR></TABLE>
i have definatly took that into consideration....your wastegate is not sealed, and the atmospheric pressure would effect when it opens.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by konigturbocivic »</TD></TR><TR><TD CLASS="quote">there is not less AIR there is less oxygen in that air.. at sea level there is i think around 20 % oxygen in our air.. up there has less oxygen.. it will still be at 10psi both places but the higher alt will be slower because there is less oxygen.. and your **** will run rich..
</TD></TR></TABLE>
i also thought about that....where did you get that info from. I didn't think the percentage of oxygen was any less at higher altitudes
05-05-2005, 10:16 PM
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Re: turbo: altitude vs hp (DaZman69)
Ben Strader of EFI University
This topic would be a good one to cover in your classes. You could use all your cool bicycle analogy.
I see this topic everywhere and alot of confusion on this topic.
This topic would be a good one to cover in your classes. You could use all your cool bicycle analogy.
I see this topic everywhere and alot of confusion on this topic.
05-06-2005, 03:58 AM
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Re: turbo: altitude vs hp (RA166E)
He does cover this in his EFI 101 class a bit. The cool this is, you can ask him more about anything he teaches and he will go into further detail
05-06-2005, 04:27 AM
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Re: (konigturbocivic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by konigturbocivic »</TD></TR><TR><TD CLASS="quote">there is not less AIR there is less oxygen in that air.. at sea level there is i think around 20 % oxygen in our air.. up there has less oxygen.. it will still be at 10psi both places but the higher alt will be slower because there is less oxygen.. and your **** will run rich..
</TD></TR></TABLE>
This is true. the higher up you go, the less oxygen there is. there isn't less 'air', but just less oxygen. this was covered in highschool if i remember correctly.
also for reference, my car was tunned in MN which is higher in elevation than CA, i took a road trip down to the Rocky Mountains and while up in the Rockies my car was running rich as hell when i checked it with my laptop.
</TD></TR></TABLE>
This is true. the higher up you go, the less oxygen there is. there isn't less 'air', but just less oxygen. this was covered in highschool if i remember correctly.
also for reference, my car was tunned in MN which is higher in elevation than CA, i took a road trip down to the Rocky Mountains and while up in the Rockies my car was running rich as hell when i checked it with my laptop.
05-06-2005, 02:21 PM
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Re: (shermanyang)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by shermanyang »</TD></TR><TR><TD CLASS="quote">
the higher up you go, the less oxygen there is. there isn't less 'air', but just less oxygen. this was covered in highschool if i remember correctly.
</TD></TR></TABLE>
there is less air....
theres less pressure, so if you capture a cubic foot of air at 10,000 feet it will have less mass then a cubic foot of air at sea level
im still in doubt that there is less oxygen
the higher up you go, the less oxygen there is. there isn't less 'air', but just less oxygen. this was covered in highschool if i remember correctly.
</TD></TR></TABLE>
there is less air....
theres less pressure, so if you capture a cubic foot of air at 10,000 feet it will have less mass then a cubic foot of air at sea level
im still in doubt that there is less oxygen
05-06-2005, 04:16 PM
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Re: turbo: altitude vs hp (DaZman69)
Having driven the same car turbo @7psi at sea level and then within 2 hours driven it at 8000ft (summit) @7psi, I can guarantee you that the car is way, way faster at sea level.
While boost held at 7psi in both places (AVC-R), the car felt as if it were naturally aspirated at high elevation. This makes sense, since we're just running a 7psi pressure differential from atmospheric press, which is way lower @ 8000ft.
While boost held at 7psi in both places (AVC-R), the car felt as if it were naturally aspirated at high elevation. This makes sense, since we're just running a 7psi pressure differential from atmospheric press, which is way lower @ 8000ft.