Explanation: Turbo vs. NA at Altitude
03-07-2006, 05:18 PM
#11
Junior Member
Join Date: Jan 2005
Posts: 1,068
Likes: 0
Received 0 Likes
on
0 Posts
yeah.. that can still be affected
That essentially is the time when the car is still NA, need to get air into the motor to produce heat to get the turbo spooled. So time too requested would be slower.
Actually an interesting test, not sure how close you are to mtns. But doing some logs at low altitude and high altitude to see what the change in requested boost is.
Actually an interesting test, not sure how close you are to mtns. But doing some logs at low altitude and high altitude to see what the change in requested boost is.
03-07-2006, 06:26 PM
#12
New Member
Join Date: May 2003
Posts: 21
Likes: 0
Received 0 Likes
on
0 Posts
Re: no you don't need to explain again you need to pay attention
PD thanks for the explanation--glad to see better heads around to account for what I feel with a turbo at higher altitude. This certainly makes sense.
03-07-2006, 07:05 PM
#13
AudiWorld Super User
Thread Starter
Join Date: Aug 2005
Posts: 3,008
Likes: 0
Received 0 Likes
on
0 Posts
So you're confirming that the program will compensate for altitude if additional boost is available?
And obviously there's less headroom when you're running chipped, using all available boost already.
03-07-2006, 07:19 PM
#14
Senior Member
Join Date: Dec 2005
Posts: 8,364
Likes: 0
Received 0 Likes
on
0 Posts
Re: no you don't need to explain again you need to pay attention
Logger, I respect your opinion from the first go round, but I don't think this thread has exactly clarified or resolved the issue of turbos at altitude.
These theories(at least as presented) about available or reserve boost, and how that may be called upon by a turbo engine in varying air densities is not engine, model, or even auto specific.
Cooler heads may be prevailing here, but I don't know if they're necessarily more knowledgeable ones.
There are several issues which come into play with the car turbo here such as ECM, A/F, emissions, bypass, internal heat limitations, etc.
These theories(at least as presented) about available or reserve boost, and how that may be called upon by a turbo engine in varying air densities is not engine, model, or even auto specific.
Cooler heads may be prevailing here, but I don't know if they're necessarily more knowledgeable ones.
There are several issues which come into play with the car turbo here such as ECM, A/F, emissions, bypass, internal heat limitations, etc.
03-07-2006, 07:42 PM
#15
AudiWorld Super User
Thread Starter
Join Date: Aug 2005
Posts: 3,008
Likes: 0
Received 0 Likes
on
0 Posts
Re: Look.....
I think you're basically right, but the value seems to be closer to 3% per 1000'.
An aircraft handbook is a good reference because the engines work on the same principle, and because the effects of altitude are thoroughly documented.
Everything else seems right, except we know the VAG ECU program does not use all available boost. That is why these engines respond so well to tuning, and it's also why unchipped engines can adapt to altitude without losing power: basically, the computer turns up the boost to compensate for thinner air.
I'm thinking OEM peak torque can be maintained as high as 8000-9000 feet because, as the tuners have proven, there's a lot more boost to be had at peak torque. But peak power probably starts to drop off much lower -- maybe even below 4000 feet. There's just not that much more boost available at peak power.
An aircraft handbook is a good reference because the engines work on the same principle, and because the effects of altitude are thoroughly documented.
Everything else seems right, except we know the VAG ECU program does not use all available boost. That is why these engines respond so well to tuning, and it's also why unchipped engines can adapt to altitude without losing power: basically, the computer turns up the boost to compensate for thinner air.
I'm thinking OEM peak torque can be maintained as high as 8000-9000 feet because, as the tuners have proven, there's a lot more boost to be had at peak torque. But peak power probably starts to drop off much lower -- maybe even below 4000 feet. There's just not that much more boost available at peak power.
03-08-2006, 02:04 PM
#17
Junior Member
Join Date: Jan 2005
Posts: 1,068
Likes: 0
Received 0 Likes
on
0 Posts
What don' you get about the fact that the car can vary boost at altitude to get the same power
BAsically tahts all a chip is doing.. varying boost.. ITs all the car does in different climates.. varies boost..
take a look at block 006 field 4 and get back to me on what the car is and isn't doing.<ul><li><a href="http://www.ross-tech.com/vag-com/m_blocks/001-009.html">http://www.ross-tech.com/vag-com/m_blocks/001-009.html</a</li></ul>
take a look at block 006 field 4 and get back to me on what the car is and isn't doing.<ul><li><a href="http://www.ross-tech.com/vag-com/m_blocks/001-009.html">http://www.ross-tech.com/vag-com/m_blocks/001-009.html</a</li></ul>
03-08-2006, 02:56 PM
#19
Senior Member
Join Date: Dec 2005
Posts: 8,364
Likes: 0
Received 0 Likes
on
0 Posts
Re: What don' you get about the fact that the car can vary boost at altitude to get the same power
yes, to some extent, with some loss, and with resultant heat issues(harder working) that may then be controlled by ECM(dialed back). this is not a straight correlation of 'on demand' turbo power compensating by simply calling on extra boost. check it out.
03-08-2006, 04:45 PM
#20
Junior Member
Join Date: Jan 2005
Posts: 1,068
Likes: 0
Received 0 Likes
on
0 Posts
Yes there will be more heat but that is more dependent on the IC system to control it
AT higher altitude you may have lower temps then sea level so you will have cooler inlet temps which will result in cooler outlet temps given teh same boost level.. Not to mention the ambient air being cooler will have a greater effect on cooling through the IC system
The point is the car has the ability to read ambient temp (inlet) and post intercooler temp, also pressure in the system and ambient. Not to mention the MAF reading air coming in.. and the 02 sensor reading air coming out.
The car can figure out EXACTLY how much power its putting out and that is what is being requested not boost.
Doesn't matter if the incerase in boost results in slightly hotter charge temps it has the ability to request say another psi of boost to compensate for the increased charge temps.
Example say at sea level the car neeeds 10psi at X rpm to get 200hp. Lets for arguments sake say that the engine makes 100hp without boost so the 10psi is worth 10hp each. This is simply for units to make a point. I understand that at elevetion that 100hp from no boost may be 95hp.. thats besides the point.
So say at altitude that for each 1psi you get now only 8hp.. So you now have 80hp or 180 total. So the ECM says ok run 13psi.. you now have added 24hp to the equation. FActor in some slight loss of effciency for heat (which again is almost negligible with our IC system if you actually did some research on it before commenting).. and a few hp to make up for the loss of the intial 100na hp you are now back at roughly 200hp with 13psi instead of 10psi.
REally not a difficult concept to grasp at all.
The point is the car has the ability to read ambient temp (inlet) and post intercooler temp, also pressure in the system and ambient. Not to mention the MAF reading air coming in.. and the 02 sensor reading air coming out.
The car can figure out EXACTLY how much power its putting out and that is what is being requested not boost.
Doesn't matter if the incerase in boost results in slightly hotter charge temps it has the ability to request say another psi of boost to compensate for the increased charge temps.
Example say at sea level the car neeeds 10psi at X rpm to get 200hp. Lets for arguments sake say that the engine makes 100hp without boost so the 10psi is worth 10hp each. This is simply for units to make a point. I understand that at elevetion that 100hp from no boost may be 95hp.. thats besides the point.
So say at altitude that for each 1psi you get now only 8hp.. So you now have 80hp or 180 total. So the ECM says ok run 13psi.. you now have added 24hp to the equation. FActor in some slight loss of effciency for heat (which again is almost negligible with our IC system if you actually did some research on it before commenting).. and a few hp to make up for the loss of the intial 100na hp you are now back at roughly 200hp with 13psi instead of 10psi.
REally not a difficult concept to grasp at all.