Questions about octane and canned tunes
 

Okay, so here it goes...I just purchased my truck and a CTS to go with it. At this point I am not getting any custom tunes on order for at least a few weeks as I have some other things that I need to buy for the truck as well right now. Can I run the 93 performance tune with 87 octane until I am ready to place my order for custom tunes or should I stay with the 87 tow tune?

I am planning on getting both custom performance and tow tunes for 87 octane in the near future, but am trying to make sure that I am squared away until that point.

Thank you.

NO!! The 93 performance tune is specifically for higher octane gas. Doing so could result in damage to your truck.

Use the 87 octane tow tune or fill the tank twice with 93 before switching to the performance tune.

X2! (What he said!) Perfectly stated, Longshot! :thumbs up yellow:

- Jack

I have an '07 but I'm sure the same applies. I'm waiting on my gryphon cs to get here. (stuck in the crappy weather in GA for now). But when it does I should run 2 tank fulls of 93 before switching to the performance canned tune? I would think the same would apply once I get my custom tunes (87 T & P, 93 P). How about going from a 93 performance tune to an 87 performance tune?

You want to run two tanks of premium before switching to the premium tune because there is 87 in the fuel lines and tank. The first batch of 93 is contaminated with 87 octane fuel. If you go to the gas station when the arm is on E you still have a few gallons left. You will only be diluting it with 93 octane, not replacing it. You will also have pure 87 octane fuel in the gas lines. If you load up the the 93 performance tune and drive agressively with 87 it can very easily cause problems.

The more 93 you add the more you will dilute the 87 octane. Then when you fill your second tank you should have the 87 diluted well enough to not cause trouble.

No problem in going down, you just have to be careful going up.

I've determined that my truck still has 5 gallons in the tank when the low level light comes on. So, after driving the truck home from the gas station to clear out the lines of the old fuel (7 miles), I'd determine the actual octane in the tank this way:

((5 x 87) + (25 x 93)) / 30 = 92

I think, really, you could probably switch to the 93 octane tune at this point without too much danger. Don't push the truck hard till you refill the tank with 93 though.

- Jack

Thank you for the responses. The answer to this next question may be posted somewhere else on the forum, but searching on my iPhone, I was having a hard time finding answers to match the question so here it goes.

What effect is elevation going to play in the use of any tune on a gas engine? The reason that I ask is that I live at around 1600 feet and work at around 4100 feet, passing above 5000 feet during the trip. I make this commute three times a week...two trips in x direction and one trip in y direction depending on my work cycle.

Is there any real effect with a gas engine like there is with say the PSD (read about one that had excessive smoking under tune). I am going to provide all of the elevation information when I order my custom tunes, but I am just trying to gain insight and wisdom on the matter in the process.

I thought telephones were for calling people. :D

It might effect your driveability but it wont be dangerous. Luckily you are gaining altitude where the air gets thinner. Worst case scenario you run rich while you are up high. It is high altitude tunes at sea level that can be dangerous.

I thought the same thing about phones until I got this one. Now I more or less live on it because I use it while I'm at work...I'm working nights now and even when on a work computer, I can't access forums, and can't drag my laptop to work. Anyways, side note aside.

This one has me puzzled a lot now. I am going to order 87 performance and tow tunes in accordance with previous suggestions and other readings. To throw another link into the chain, I do travel to sea level on a not so regular basis also. In around 3 hours, I can go from sitting on the beach to over 5000 feet. Next year I will be moving and will be living around 4100 feet, but trips to 1500-2000 feet won't be that uncommon with the occassional trips to the coast.

Now that I have started this discussion, it really has my interest peaked from a tune writers perspective, not that I know anything about it, and how to compensate for possible variables in providing a person the best tune for their application.

I'm pretty sure that the truck's MAF sensor is able to adjust for the altitude since its primary job is to measure the volume of air that enters the engine. I know that old vehicles and the diesels sometimes have a problem with it since they dont have MAF sensors or any way to correct automatically. I do know that Bill makes adjustments to the WOT fuel based on altitude because during WOT the truck fuels based on that number instead of the sensors.

Usually 5000 ft is the limit of low to high altitude tuning. Since you hover there all the time your truck (most of the time) experiences changes of about 3000 ft. The altitude section on the order form just helps give a ball park of where to set it.

I'll see if I can get Cody to comment, he actually knows what he's talking about. ;)