03-26-2009, 10:47 PM
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#37 (permalink)
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Base Member
Join Date: Mar 2009
Location: TEXAS
Posts: 171
Drives: 08 335i, 86 Ranger
Rep Power: 18
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Quote:
Originally Posted by serge
I lived in Colorado Springs (6,000 ft. altitude) and I'm pretty familiar with the negative effects of thin air on engines, specially NA ones. Someone stated on a previous post that at 5000 ft., a NA engine loses 3% power. Wrong. It's 3% every 1000 ft., equaling 15% power loss. As an example on how bad altitude is, my bolt-on Evo used to run 11.9 @ 115 mph at sea level, but was only able to manage a best 12.8 @ 108 at 5,500 ft (Denver), almost a full second and 7 mph slower.
The reason why your 335 is faster than your Z at 5,000 ft. is because the 335s ECU compensates for altitude with extra boost, around 2psi. My best friend has a modified 335 with Procede tune and he runs faster at altitude (Tucson, 3000ft.) than sea level. So, while your Z is losing about 15% of its power (285-290bhp "after taxes"), your 335 is basically keeping all its original power, which is believed to be around 320-330 bhp "tax free". There're plenty of posts on e92.com from owners with stock 335's "destroying" more powerful NA cars like the C6 Vette (LS2s), 911 CSs or SRT8s at >4000 ft. altitude. The 335s boost compensation feature does miracles on the 335 at high elevation.
Nevertheless, even though it may not be the faster car around the block, I'll be getting a 370Z as soon as I get back from my deployment  |
Are you sure his 335i is running faster at that 3,000ft? You are right, the ECU does adjust accordingly. The ECU is having to accomodate the altitude, but higher boost does not equal more power in this situation. For example, a FMIC actually drops the amount of boost required to produce the same amount of power.
On a side note, my buddy is coming into town with his 370z. We'll be heading out to the houston raceway park in baytown -- I'll try and post some vids.
Last edited by ianthegreat; 03-27-2009 at 06:07 AM.
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