octane rating qs

im from south texas, i went up to new mexico last week and the octane ratings at the pumps were diff. i was ina rental so i didnt care. but this winter i wanna take my sl to the mountains for some good drining. supreme here is 93 octane, but over there its only 90, could it be because the altitude??? will my car be ok with 90 octane??
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If you are in really high altitude your car will run just fine on 91 octane as there will be significant changes in altitude and thus thinner air causing less compression. If you go to Colorado up in the mountains they sell 85 octane as their standard grade gasoline.

yea it was about 9k above sea level
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an SL will be fine with 91 octane anyway. Only the turbos need 93.

Here in Utah we only have 91..

an SL will be fine with 91 octane anyway. Only the turbos need 93.
Again that is untrue. In a lot of places the highest you can get is 91. The owners manual even says run at least 91. It doesnt say 91 for non turbos and 93 for turbos.

Here in Utah we only have 91..

Yep, we can't get 93 here and my TT has never complained about it.

when i was in OK City for training all they had was 91 and it made my car run like garbage and smell terrible. Tried different brands but didnt do any good. After the first few fillups it eventually started running smoothly, but still felt sluggish like it was down on power and still smelled. Maybe the ECU has to learn what fuel your running or something?

they had 91, but the reasoneis that the airs thinner, so they needa compensate for the i guess. so it will burn right
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when i was in OK City for training all they had was 91 and it made my car run like garbage and smell terrible. Tried different brands but didnt do any good. After the first few fillups it eventually started running smoothly, but still felt sluggish like it was down on power and still smelled. Maybe the ECU has to learn what fuel your running or something?
I think it was in your head.

The air is thinner, ie less oxygen, so less oxygen means less fuel needed.

when i was in OK City for training all they had was 91 and it made my car run like garbage and smell terrible. Tried different brands but didnt do any good. After the first few fillups it eventually started running smoothly, but still felt sluggish like it was down on power and still smelled. Maybe the ECU has to learn what fuel your running or something?

I think it was in your head.

The air is thinner, ie less oxygen, so less oxygen means less fuel needed.

Probably the altitude had something to do with it and the ECU had to readjust the trims to account for the changes too.

no the cars shouldrun just fine at higher altitudes with the slightly lower octane rating. i just wanted to make sure cuz i dont wanna be stuck in a part of thecountry with shit gas. i saw a vr4 up there hauling ass, his car seemed fine, lol. and another stealth parked.
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no the cars shouldrun just fine at higher altitudes with the slightly lower octane rating. i just wanted to make sure cuz i dont wanna be stuck in a part of thecountry with shit gas. i saw a vr4 up there hauling ass, his car seemed fine, lol. and another stealth parked.
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Altitude affects forced induction cars very little to nothing at all. Thats proven.

Hell, Matt Monet at Dynamic Racing runs 8's at 5000 feet.

so is that canfirming my statement? lol
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Altitude affects forced induction cars very little to nothing at all. Thats proven.

Hell, Matt Monet at Dynamic Racing runs 8's at 5000 feet.

Where or how is this proven? Cause I know for a fact that if I run at my track here in Utah (4200ft) then drive down to Vegas and run there is almost a full second difference. take in to account that they prep better in vegas then here but not 1 second better prep...

Also the car won't have issues with changing altitude thats what you have a barometric sensor for ;)


Jason

Track prep makes a HUGE difference. The first 60' makes or breaks a good run.

Right here NHRA only allows half altitude correction for supercharged and turbocharged cars.

http://www.nhra.net/tech_specs/altitude.html

As it is LV is still at 2100ft so if your car was suffering due to altitude it would still suffer in Vegas.

Its also been discussed many times on 3si how altitude does not effect FI cars by people like Monet. If FI cars suffered from altitude then airplanes would be fucked considering thats where SC and TC's came from originally.

EDIT: Found a formula (note this is for NA's)

hp loss = elevation x 0.03 x hp @ sea level
1000

So a 320 hp NA engine at sea level would make about 280 hp 4200 feet. A forced induction engine may lose 10 hp at that altitude.

yea, the higher the altitude, the thinnr the air, thats not a 3s fact, but a fact of the universe. the higher the alt, generally, the less power u produce, thats physics, and fact for an internal combustion 2 and 4 stroke engine, even rotorys. if matt ran at the sa trak, near sea level hell prolly imprve his time..physics is on his side anyways. but altitude is not everything, colder air is denser air, notice matts runs r at night, where in roswell can be really cold. but during the day at roswell its super hot, if he ran in the heat of the day it wouldnt be as quick of a ride. but the night air doesnt balance out the altitude difference, altitude, is a bigger factor
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yea, the higher the altitude, the thinnr the air, thats not a 3s fact, but a fact of the universe. the higher the alt, generally, the less power u produce, thats physics, and fact for an internal combustion 2 and 4 stroke engine, even rotorys. if matt ran at the sa trak, near sea level hell prolly imprve his time..physics is on his side anyways. but altitude is not everything, colder air is denser air, notice matts runs r at night, where in roswell can be really cold. but during the day at roswell its super hot, if he ran in the heat of the day it wouldnt be as quick of a ride. but the night air doesnt balance out the altitude difference, altitude, is a bigger factor
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Matt himself has even said he'd be lucky to pick up 1 tenth by racing at sea level. Its a FACT that forced induction is not affected much at all by altitude.

wait, ok, so because the turbos compress the air right??? so the only thing that would be happening differently is the compressor wheels would spin faster since they have to compress thinner air, am i right?
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Exactly. The boost curve would be slightly altered but power difference would be minimal. A NA car suffers because it can only use the available oxygen.

so this means i should find a vr4 engine and tranny befori go, hahah well dam
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You will feel a difference. I dont know the altitude difference between Kingsville and where you are heading but it may only turn out to be a 10-15 hp difference.

0 to 9000 feet...the mountain road there is insane in the membrane. hey alil off thread topic tho, snce im not gonnahave the awd powertrain loss of a vr4, what should i expect a dyno run at?
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I assume you'll be on RT 82 since it climbs pretty high?

According to the formula if you made 210 hp (closer to actual hp, not 222 rated by Mitsubishi) you would be down to 153 hp at 9000 ft. Thats about 125 whp. :eek: Your car will be a slug.

lol dammm ok then im waiting till i find a tt engine. r there any reliable engine dealers, either through ebay or other website, that have relisble engines??? i no its risky, but im planning to haveit on stands and overhauly it all before i put ir in
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wait, ok, so because the turbos compress the air right??? so the only thing that would be happening differently is the compressor wheels would spin faster since they have to compress thinner air, am i right?
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but would the stock turbos be able to effectively compensate for the thinner air? it seems like the guys who dont feel a difference all have big ass turbos

A turbo is a turbo and they act the same. The boost curve will slightly change but peak power will remain almost unchanged.

would you be able to run higher boost at a higher altittude?

Monet runs 32-35 lbs of boost.

:eek7:

whoaa
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If FI cars suffered from altitude then airplanes would be fucked considering thats where SC and TC's came from originally.

actually, jet engines (turbofans, like the type found on modern airliners) are greatly effected by altitude...though not in quite the same way. The issue they have is that up at 32000 ft or w/e, the air is so thin that there's very little difference between over-revving the engine and stalling it, and they create less power at altitude. Doesn't just have to do with cruising altitudes either...The runways at Denver intl airport are almost twice as long as the runways at San Antonio intl, and for good reason.
But yea theyre still not effected nearly as much and conventional reciprocating engined aircraft which dont have a hope in hell of reaching those altitudes.