Altitude & Octane Tuning

[Mean Gene55]

Guys - I've tried the search feature but came up empty so I'll pick your brains. I've just bought a 2000 w/a 383 stroker & an F1R running 14# of boost. The car is in Arizona so it's tuned for 91 octane as well as for a 4500' altitude. I live in Louisiana so we have 93 octane plus we're pretty much at sea level so anybody want to take a guess as to how much more power is hidden in there when I have it re-tuned for my specs? Jon says he's putting down 750+ rwhp w/his current ( Arizona ) tune ( LOTS of other breathing mods besides the ProCharger! ). Just trying to get an idea of what to expect but I'm still post the resulting dyno sheet ( from Texas Speed & Performance ) once things are completed. Glad to be back amongst my domestic bretheren after a decade of imports!! Gene

[leojnknsC5]

Originally Posted by Mean Gene55

Guys - I've tried the search feature but came up empty so I'll pick your brains. I've just bought a 2000 w/a 383 stroker & an F1R running 14# of boost. The car is in Arizona so it's tuned for 91 octane as well as for a 4500' altitude. I live in Louisiana so we have 93 octane plus we're pretty much at sea level so anybody want to take a guess as to how much more power is hidden in there

Why would it be tuned for 4500' if its in Arizona? Phoenix is only 1300 feet or so. Flagstaff is over 6000 feet. If it has an F1R then its sensitive to altitude changes cause you'll gain or lose about a pound of boost for every 1000 feet of elevation change. If you take it to Louisiana at sea level you'll need to increase the size of the sc pulley, probably five tenths of an inch (call ATI), to bring it back down to 14#'s. The 93 octane wont really allow much more timing advance so the fuel isnt a big deal breaker.

So the question is: Does it make 14#'s at 4500 feet? Or does it make that much at 1300 feet? Or 6000 feet?

[Mean Gene55]

Leo - The car's in Hereford & Huachuca Oaks Camp there shows to be at an elevation of 5050' so 4500' seems to be correct. I'm just listing what Jon ( the seller/builder ) told me & that was "14# of boost @ 4500' & on 91 octane yielded 750+ rwhp". He didn't have the dyno sheets so I'll have to take him at his word ( no reason to doubt him yet ). As I stated before, the car has lots of other breathing mods & methanol injection in it's support system.
Thanks for the input about the boost vs elevation changes!! Guess I'll just have to see what happens when Texas Speed & Performance straps her down to their dyno next week. Wish I had some baseline dynos to compare it to but if being at sea level ( if ya wanna be technical - 89' above ) is gonna give me an additional 4# of boost ( or so ) I'll need a different pulley because Jon says that he can't get the power to the ground as it is!! Nice problem to have!! I'll post dynos whenever things are done.

Gene

[leojnknsC5]

Originally Posted by Mean Gene55

Leo - The car's in Hereford & Huachuca Oaks Camp there shows to be at an elevation of 5050' so 4500' seems to be correct. I'm just listing what Jon ( the seller/builder ) told me & that was "14# of boost @ 4500' & on 91 octane yielded 750+ rwhp". He didn't have the dyno sheets so I'll have to take him at his word ( no reason to doubt him yet ). As I stated before, the car has lots of other breathing mods & methanol injection in it's support system.
Thanks for the input about the boost vs elevation changes!! Guess I'll just have to see what happens when Texas Speed & Performance straps her down to their dyno next week. Wish I had some baseline dynos to compare it to but if being at sea level ( if ya wanna be technical - 89' above ) is gonna give me an additional 4# of boost ( or so ) I'll need a different pulley because Jon says that he can't get the power to the ground as it is!! Nice problem to have!! I'll post dynos whenever things are done.

Gene

The F1R has potential for alot of boost in a 383. And you might see 5# increase if you go down 4000 feet. ATI told me to change pulley size one quarter of an inch for each 2500 feet elevation change. Its an approximation and I found it was close but I really needed to increase pulley size .45 inch for 3000 feet drop in elevation. (Salt Lake City 4200 to Phoenix 1200 feet) But it will give you a place to start. If you are going to drive it to Louisiana, when you get to sea level avoid running the rpms too high where boost levels are the highest, until you get it redynoed.

If you dont change pulley size, with the pulley that is on the car you might see 20# at sea level, and then the question is whether the serpentine belt can handle that much boost. It may slip. Or lift the heads or blow a head gasket. Depends on what Jon built the motor to handle, boost wise.

[Mean Gene55]

Leo - Thanks for the pulley rule of thumb! I spoke w/Jason @ TS&P & he's at 3500' himself ( in Lubbock ). Fortunately, he told me about a tuner in my back yard ( well, 100 miles away ) so I'm having the car transported to Thunder Racing in Baton Rouge where we'll see what we come up with. Jason said he'd expect about a 2# increase in boost so changing to a larger pulley may end up being an option. Personally, I HATE the idea of LOWERING boost but if I can't get the power to the ground, what good does it do me?
Paul ( the Thunder tuner ) says that he's more concerned w/lifting the heads on the LS6 if we ramp up the boost rather than a problem w/the Lunati internals. Somehow I don't think I'll be going up in boost but I'll probably hold firm on the 14# ( retuned for my area ). Hey, it IS MY car & I'll just learn how to feather the throttle!!!

Gene

[Turko]

Hey guys I'm the other way around. I had my car shipped to Ft. Wayne, IN to get a d-1/cam and other stuff done to it. Anyways the elevation out there is 400 ft above sea level and the elavation here in El Paso, TX is 3300 ft. What should my concerns be? The only thing I have noticed is my AFR gauge reads 11.2 at idle and 10.2 at full boost 8lbs. Does everyone agree that I should retune or should I be ok. I really don't trust the gauge it's an innovate gauge so who knows if it's reading right. I'm supposed to be pushing around 525 rwhp and about 511 rwtq on a mustang dyno but don't know if the elevation and tune might be hurting it? Any help greatly appreciated.