Modded L67 at high altitudes? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-30-2010, 05:26 PM   #1
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Default Modded L67 at high altitudes?

Just wanted to ask if there would be any potential issues with me driving the Regal hard under high altitudes.

L67 swap, 3.4, headers, CAI, 104'*, 2.5" catback, tune.

Going to be driving through Colorado in a couple of weeks and they have some pretty steep hills, so I'm expecting some heavy throttle for a portion of it. Just wanted to make sure I wouldn't run into any problems or that there isn't anything I need to be worried about.
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Old 09-30-2010, 10:08 PM   #2
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I lived off and on in Colorado from, 1969-88. Never had any trouble with any car other than a 75 Dodge Truck with Cali Emissions BS.
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Old 09-30-2010, 10:29 PM   #3
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i drove my ssei to co this summer it had no prrobs
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Old 10-01-2010, 03:01 AM   #4
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Carburetors have no problems with altitudes, and there'* no re-tune necessary. It'* the fuel injected cars that have problems with air pressure. Who tuned your car for you? The thing is that in Colorado, you're only going to find 91 octane gas and some pretty high altitudes. Tune down a couple degrees and make sure you can run on 91 without knock completely.
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Old 10-01-2010, 08:16 AM   #5
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Hmmm would be worth a pm to Gojo83. He'* a Coly resident.

The thing with altitude is that the air is thinner and you have less oxygen to make power with.
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Old 10-01-2010, 11:21 AM   #6
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Quote:
Originally Posted by radomirthegreat View Post
Carburetors have no problems with altitudes, and there'* no re-tune necessary. It'* the fuel injected cars that have problems with air pressure. Who tuned your car for you? The thing is that in Colorado, you're only going to find 91 octane gas and some pretty high altitudes. Tune down a couple degrees and make sure you can run on 91 without knock completely.
The guy doing my swap is doing the tuning as well, and its a pretty "safe" tune. Its also a pretty "safe" list of mods too considering some people run 3.4'* without headers and only a 3" downpipe.

Wouldn't KR be less of an issue due to there being less air, and therefore less pressure and therefore less heat to deal with?
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Old 10-01-2010, 10:02 PM   #7
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You don't only get knock from intense air pressure and heat, but also from running rich or lean. At high altitudes, you run lean quite a bit!
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Old 10-01-2010, 10:36 PM   #8
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Quote:
Originally Posted by radomirthegreat View Post
You don't only get knock from intense air pressure and heat, but also from running rich or lean. At high altitudes, you run lean quite a bit!
But doesn't the MAF detect the amount airflow coming in and compensate accordingly?
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Old 10-01-2010, 10:41 PM   #9
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Quote:
Originally Posted by radomirthegreat View Post
At high altitudes, you run lean quite a bit!
When I was in Denver, (carburetor days) you had to use leaner jets to get some larger high compression engines to run right. All in all, 91 or 93 for a mildly modded V6, we're talking pure sillyness here. He'* taking a road trip, not going to run the Mile High Nationals. I highly doubt any effect will be noticed. Unless you pull a half ton of luggage or a travel trailer up over Loveland Pass. If it bugs you, turn the timing down 2 degrees...... Or buy my nitrous kit??? Only used by a little ole grampa on Sundays.
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Old 10-01-2010, 10:54 PM   #10
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Quote:
Originally Posted by xtremerevolution View Post
But doesn't the MAF detect the amount airflow coming in and compensate accordingly?
MAF'* sense airflow, not oxygen density in air.
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