Posts: 614
Joined: 3/19/2005 From: Boston, MA Status: offline
Hey everyone. I got a question for those who understand programming more than I do.
I'm in Colorado Springs, which is about 6000ft above sea level. When I bought the car, I was told it was pre-programmed for the high altitude. That seems like a load of horseshit, but I have no way to know for sure. Not to mention, I just spent about 4 months down South for couple of military classes.
Anyways, tell me how far off I am. Intakes such as the Steeda say they require a tune, which is obvious since the engine light comes on after installing them. What exactly causes this? Is it simply a higher amount of oxygen coming in?? If so, how come I never saw the engine light in my trips to and from the Springs? Could it be because the change was gradual?
Also, if I were to install the Steeda when I live at such a high altitude, is there a possibility there would be no problems with the engine light?
On a side note, I just want to say being this high up sucks. I can feel the lack of power, and my wallet can feel the reduced gas mileage....
< Message edited by flapjack -- 6/18/2005 4:10:18 AM >
Hi flapjack! I'm glad you asked that question. I don't know the answer but it just made me realize something. We are going on vacation in a week to Colorado Springs! I have purcahsed the Steeda kit and already had my Xcal re-tuned. I will be putting it on today and hadn't thought about the altitude change until I read your question. I hope someone can answer for us poor old dummies. Kind of sorry to hear about the loss of power too. I'm really starting to get used to this great running machine!
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V6 5-speed Sonic Blue. GT fog lights, Magnaflow dual exhaust, Steeda CAI, X-cal tuner, sequential tail lights, black shorty antenna, flaming horse hood decal.
The denser the air, the greater the tendency to pre-ignite and/or detonate, so the lower density at higher altitudes allows for greater advance without the knocking that the same advance would cause at lower altitudes. With a high altitude tune the engine will likely knock as you get closer to sea level, but the ECM will compensate for this immediately and knocks will be very few and far between. But then, when you return to the higher altitudes, the advance should return to it's optimal position over time, and until it does there would probably be a barely noticable drop in power.
I imagine that this is may one of the components that causes illumination of the check engine indicator with the installation of a CAI. I come to this conclusion because: The cooler air will be more dense, and according to the propaganda, will be flowing more freely, thus allowing significantly more mass into the combustion chamber. The greater mass of the fuel/air charge equals a greater tendency to detonate (all other things being equal). Then, when the knock sensor tells the ECM that it has detected the inevitable ping, the computer modifies various parameters based on a programmed pattern to compensate and try to correct the knock. When the programmed adjustments do not acheive the expected result, the ECM throws an exception to illuminate the check engine light. It has assumed that since it cannot correct the problem by making adjustments that fall within the "normal" range, then there must be something wrong with the system.
This is certainly not intended to be a comprehensive answer, and I invite contributions and corrections to my assumptions. Especially from, say, an SVT tech?
So if I'm understanding this right, I shouldn't have a problem having a low altitude tune and take it to a higher altitude. That is at least not a knock problem. Is this correct? And thank you for the great response.
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V6 5-speed Sonic Blue. GT fog lights, Magnaflow dual exhaust, Steeda CAI, X-cal tuner, sequential tail lights, black shorty antenna, flaming horse hood decal.
Yeah, for a number of reasons I would imagine that you'd be ok. Primarily, because you're already tuned for optimum performance, and driving from one pressure/altitude to another is surely within the normal limits of "correctability" (if that's a word). And I say that should be true whether you are going from high to low pressure and vice versa (for the home-bound segment of your trip). I wouldn't be suprised if you heard a few knocks, 1 or 2 at a time on the way home under heavy accelleration, but it shouldn't persist.
Be sure and use a higher octane gas at the higher elevation though. I have to use at least 88 with some octane boost, and I am at 3500 feet. DO NOT use the 86 that they offer in the higher altitude, it states this in your manual.
Also when i went to buy my car from a dealership, they stated they order their cars with a high altitude tune on the computer, I said thanks and when to the dealer a town away since my car is going to germany in August and I wont need this damn high alt tune.
Posts: 614
Joined: 3/19/2005 From: Boston, MA Status: offline
MustangBuddha: Thanks for the detailed reply. Makes a lot of sense.
Badash: Actually, I've only seen 86 in Amarillo. They have 85 here. Why would they sell it if it's bad, then? All the guys in the shops here say to use the lower octane at higher elevations because you're just blowing fuel out the tailpipe otherwise.... since there's not enough air to burn all the fuel.
Look at your owners manual. I think its page 211 or around there. It specifically states not to use anything under 87, and they also specify not to use the lower octane's that are available in the higher elevations. I used 86 until my fuel sender went bad, then the wife looked up in the manual and saw that it says not to use anything under 87. I switched to 91 for two tanks, sender works again, check engine light went out, and I went down to 88 and have had no problems.
This weekend, I took two seperate trips of about 1 hour each way for a total of 4 hours or 241 miles of driving, including the little around town driving and got 27 MPG.
< Message edited by Badash -- 6/19/2005 6:40:20 PM >
I live in Denver CO and have never had problems with lower octane so that is totally hogwash... I use the middle grade here which happens to be 87 (as recommended by ford)... also as far as tunes go I trully doubt it - when I moved here in 99' i brought an explorer i purchased from FtL florida with me and never had any problems with emission or anything related high altitude
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Tune for high altitude? - 
