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      08-30-2012, 10:48 AM   #1
E92_SID
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Supercharger numbers at altitude 5200ft?

Hello all... I am just wondering if anybody has any numbers (0-60, 1/4 mile, ect) of what an E9X supercharged at altitude might run?

As we all know, NA engines lose a ton of power at altitude. An example of this is the fact that the best time I have seen a stock E9x run the 1/4 mile here in Denver (5280 ft) is 14.69. I know our cars are running a lot faster than that a sea level.

For this reason, I am seriously considering a supercharger. Just want to make sure that it is worth it. Its pretty sad that up here, M3s need a supercharger to keep up with the tuned 335 guys
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      08-30-2012, 11:13 AM   #2
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Contact member e60cs5. He has a ESS supercharger on his E92 here in SLC, we're about 4200ft.
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      08-30-2012, 07:15 PM   #3
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Theoretically, there should be no difference between SL and any altitude as long as you are able to maintain the same amount of boost. Not knowing for certain, but I would guess the software would allow boost to build to X psi/bar as long as the atmospheric conditions and the supercharger are capable. I am curious too. I thought about SC'ing my car as well. Living in El Paso, there is a noticeable difference that is immediately felt since I left Germany.
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      08-30-2012, 07:57 PM   #4
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You won't maintain the same boost pressure at altitude that you would at sea level. Superchargers are not like turbos in that respect. You will lose 1-2 PSI of boost per 5000 ft.

Hopefully someone will chime in with real world results.
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      08-30-2012, 09:48 PM   #5
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Quote:
Originally Posted by M3PO View Post
You won't maintain the same boost pressure at altitude that you would at sea level. Superchargers are not like turbos in that respect. You will lose 1-2 PSI of boost per 5000 ft.

Hopefully someone will chime in with real world results.
True, but you could put a smaller pulley diameter on to compensate to bring the boost back to the normal rating without over stressing the block.

Well, until you drive the car down to sea level
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      08-30-2012, 11:15 PM   #6
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There is a massive difference between SL & 5000ft. About 2 psi.
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      08-31-2012, 06:27 AM   #7
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Im at 5500 ft and all I did was run a different crank pulley and SC pulley to ensure I made the required boost level for the VT2 625 kit.

Issue is when you take the car to sea level, you will be required to chage the pulley again otherwise you will over boost.

Remember with a turbo, there is a boost target level that the ECU will always regulate and spin the turbos accordingly.

SC is mechanical and boost is not regulated by ECU. To make it spin faster or slower is a direct result of the pulley set up. At altitude air is thinner and SC must spin at higher RPM to make same boost at sea level


I started this thread when I first boosted my E92

http://www.m3post.com/forums/showthread.php?t=374270
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      08-31-2012, 01:11 PM   #8
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Quote:
Originally Posted by arter View Post
True, but you could put a smaller pulley diameter on to compensate to bring the boost back to the normal rating without over stressing the block.

Well, until you drive the car down to sea level
Yep, you must be careful not to spin the SC beyond it's limit though.
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      09-04-2012, 07:23 AM   #9
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Quote:
Originally Posted by M3PO View Post
Yep, you must be careful not to spin the SC beyond it's limit though.
with ESS, you are ok going up to 650 kit and compensating with a smaller pulley and crank set up.

Currently I run a custom 128mm crank and 95mm SC pulley for the VT3 set up and I make 7,5psi at 5300 ft.

At sea level this set up would make around 10 psi

Its not 2 psi its actually 22% loss so you apply a factor of 0,78 to whatever the SL rating is

There is no chance you could a run a LC VT3 motor at the desired 10-12 psi level at 5300 ft on the current T3 Vortech blower.
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      09-04-2012, 07:26 PM   #10
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Quote:
Originally Posted by Bob MG View Post
with ESS, you are ok going up to 650 kit and compensating with a smaller pulley and crank set up.

Currently I run a custom 128mm crank and 95mm SC pulley for the VT3 set up and I make 7,5psi at 5300 ft.

At sea level this set up would make around 10 psi

Its not 2 psi its actually 22% loss so you apply a factor of 0,78 to whatever the SL rating is

There is no chance you could a run a LC VT3 motor at the desired 10-12 psi level at 5300 ft on the current T3 Vortech blower.
I think the limit of that unit is something like 94,000 RPMs?
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