Chime in on this theory...
Chime in on this theory... The high-altitude performance of a turbocharged engine is significantly better. Because of the lower air pressure at high altitudes, the power loss of a naturally aspirated engine is considerable. In contrast, the performance of the turbine improves at altitude as a result of the greater pressure difference between the virtually constant pressure upstream of the turbine and the lower ambient pressure at outlet. The lower air density at the compressor inlet is largely equalized. Hence, the engine has barely any power loss.
Would wonder why those FI guys in CO seem to run faster at lower elevations then. Although the pressure is different what about molecules of Oxygen at different elevations? Higher elevation less O2 PPM? *I am feeling dumber as I think about this and type my reply*
FormerVendor
Joined: Dec 2001
Posts: 2,444
Likes: 2
From: WWW.SPEEDINC.COM
Well, that theory would be wrong.
Less air pressure/density equals less power, turbocharged or not.
An example (not real numbers, just to give an idea)
Sea level-
Boost- 20psi
impeller speed- 80,000
intake air temperature- 110
pressure ratio- 2.36
5000ft-
Boost- 20psi
impeller speed- 110,000
intake air temperature- 190
pressure ratio- 2.89
Less air pressure/density equals less power, turbocharged or not.
An example (not real numbers, just to give an idea)
Sea level-
Boost- 20psi
impeller speed- 80,000
intake air temperature- 110
pressure ratio- 2.36
5000ft-
Boost- 20psi
impeller speed- 110,000
intake air temperature- 190
pressure ratio- 2.89
Thanks for the input Charlie and 8
NOW thats the type of response I wanted to get. Thanks for the facts provided. The more I research and read , the more skepticle I tend to become. Its like a highschool textbook out here... we just have to take all the facts we can get, do out best to verify them, and then make a judgement.
I had a problem with the theory myself, but couldnt dis-prove either.
But, for the sake of argument, what if a bigger IC was used at high altitudes to lower the Intake charge temp..what effect did result overall? The pressure ratio would then drop...ouch, headache
Thanks 8
BTW, This theory was compiled by Spencer Brown. Half of it was written by Spencer Brown and the rest of it contains data from: Garrett, turbodriven.com, and Grapeaperacing.com . Of course it ended up in a guide mustang owners refer too.
NOW thats the type of response I wanted to get. Thanks for the facts provided. The more I research and read , the more skepticle I tend to become. Its like a highschool textbook out here... we just have to take all the facts we can get, do out best to verify them, and then make a judgement.
I had a problem with the theory myself, but couldnt dis-prove either.
But, for the sake of argument, what if a bigger IC was used at high altitudes to lower the Intake charge temp..what effect did result overall? The pressure ratio would then drop...ouch, headache
Thanks 8
BTW, This theory was compiled by Spencer Brown. Half of it was written by Spencer Brown and the rest of it contains data from: Garrett, turbodriven.com, and Grapeaperacing.com . Of course it ended up in a guide mustang owners refer too.
Last edited by Jammer; Dec 6, 2004 at 12:07 AM.
Since were on theory and Im just playing around with my current project (until the real project rolls through Bowling Green)...
What would happen if I ran my dual 3" exhaust which has a 4" "y" then splits back to dual 3" after the axel..and mounted my rear mount designed twins on just before the exhaust tips. As most know, Im in the middle of installing rear STS style twins...but the question here is...what if the turbos were not individually bank fed, but if exhaust went through a "y" and was split back. My initial thought is one turbo would spin faster ..the one with less restriction after the conversion from 4" to dual 3". OR, does the pressure equalize and will each turbo spin the same...I dont see that happening, but..any thoughts? I like to tread new ground, fail or succeed. BTW this is on a forged 409.
The question then begs, what if I mated the 2" intercooler pipes via "y" for the run back to the IC, and split that back into each IC entry point.
What would happen if I ran my dual 3" exhaust which has a 4" "y" then splits back to dual 3" after the axel..and mounted my rear mount designed twins on just before the exhaust tips. As most know, Im in the middle of installing rear STS style twins...but the question here is...what if the turbos were not individually bank fed, but if exhaust went through a "y" and was split back. My initial thought is one turbo would spin faster ..the one with less restriction after the conversion from 4" to dual 3". OR, does the pressure equalize and will each turbo spin the same...I dont see that happening, but..any thoughts? I like to tread new ground, fail or succeed. BTW this is on a forged 409.
The question then begs, what if I mated the 2" intercooler pipes via "y" for the run back to the IC, and split that back into each IC entry point.
FormerVendor
Joined: Dec 2001
Posts: 2,444
Likes: 2
From: WWW.SPEEDINC.COM
Yeah, there is alot of information out there. Alot of information from 30 years ago. 
Joining then splitting the pipes for the turbo inlet and compressor outlet is not a problem at all.
One turbo spinning faster than the other would be more of a problem with a divided system, as the wastegates would have to be synchronized. In your case, joining the pipes balances the flow.
I would suggest doing dual 2.5 into a single 3in than splitting to dual 2.25 to the turbine inlets. It would help spool (alot). Tubing size on the turbine inlet side would have to be extremely small in order for 'it' to be the restriction, rather than the turbine housing/wheel.
Joining then splitting the pipes for the turbo inlet and compressor outlet is not a problem at all.
One turbo spinning faster than the other would be more of a problem with a divided system, as the wastegates would have to be synchronized. In your case, joining the pipes balances the flow.
I would suggest doing dual 2.5 into a single 3in than splitting to dual 2.25 to the turbine inlets. It would help spool (alot). Tubing size on the turbine inlet side would have to be extremely small in order for 'it' to be the restriction, rather than the turbine housing/wheel.
