|08-07-2002, 08:23 PM||#1|
Join Date: Jun 2000
Location: Austin, TXVehicle:
My Stage 0 Situation
I've got the car up and running with the Stage 0 kit at .85kg/cm2. This boost setting is much lower than the 1.0kg/cm2 recommended by Shiv. I have fears of the altitude doing something messy with my car since every car has a wildly different state of tune.
I am tempted to have Christian confirm the state of the map and make any modifications necessary for $89-129. Has anybody actually had the maps checked at altitude and found it necessary/unnecessary? The biggest caveat is that Christian would prefer that I stuck with him afterwards because he wants to add some Cobb/Modern Garage Unichip tricks into my map and doesn't want them getting out.
Secondly, is it going to be worth $129 for each new mod-install fest that I do to have the car custom tuned? Safest? Yes, but damn does that get expensive quickly. Cobb will be on-hand in a few short months if that helps the justification any...
I'm not too familiar with how different the tuning states are at altitude so some ideas would be helpful. I'm 4k feet btw.
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|08-07-2002, 09:09 PM||#2|
Join Date: Apr 2001
Location: Fort Collins, COVehicle:
2004 Impreza WRX STi
Not to scare you or anything but I will share my experience with a unichip and altitude.
I took the time and went down to Cobb, in Dallas, to get my WRX tuned by him personally. All-in-all at the end of the tune I had a nice 265whp and 231wtq. He tuned to a A/F ratio of somewhere around 11.5:1 on average on full boost of 1.23kg/cm^2 =~ 17.5psi.
Now when I got back up here it was running pretty good for about 4-5 months then the summer heat came (95-100F) and it started detonating in the upper rpm range 6000+rpms. So I sucked it up and bought a wideband A/F and a Link so I could tune it myself.
Now I got my wideband before the Link so I hooked it up to see how the unichip was doing. I found out it was running leaner than what I got it tuned to at the same boost level of 1.23kg/cm^2. I went from running say 11.5:1 at a particular point to about 12.5:1 and at redline went from 10.9:1 to about 11.9-12:1. So I leaned out about a whole point for some reason. I chalked it up to "unknown effects of altitude" since most of the tuners in the country have very little experience tuning at altitude.
Conversely I would be worried about getting it tuned at high altitude and then driving down to sea level. Up here if you lean out you have a wider margin of safety in that you are running about 2-3psi less total pressure (due to atmospheric losses) than sea level. As a result of that if you do lean out a little bit you might/should be ok but if you go to sea level and lean out the same amount running the same amount of boost the problem will show itself more so.
Anyway I got the Link tuned to a nice 11.5:1 A/F and I NO LONGER have detonation issues. I have had about 5 knock events in the past 2-3 weeks of tuning it.
Just for the record I am NOT bashing or trying to bad mouth Cobb, Vishnu, or any other tuner that uses the unichip. I think they are good especially when tuned to your car. I have the utmost respect for Trey Cobb. He is a very good, polite, and knowledgable person when it comes to tuning my car and I can say nothing but good things about my visit to see him in Dallas.
Maybe I am just a bit too anal about the state of tune of my car. I mean I do run a wideband A/F, knocklink, narrow band A/F, boost, and EGT gauge and lately I have had my laptop open at the end of almost every drive to make sure the Link didn't see some knock that the knocklink missed (which has happened once or twice btw .
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