93 octane?

[tbot]

If the 2-3 psi statement above is true, then why do even FI cars make more power at sea level?!?!

That sounds like a bunch of bullshit to me.

[chromal]

If the 2-3 psi statement above is true, then why do even FI cars make more power at sea level?!?!

That sounds like a bunch of bullshit to me.

Well, they wouldn't have to work to make up that 2-3 PSI difference when operating down at sea level vs high elevation, so it still seems intuitive that they're gonna generate more power there, either because they can achieve more total boost, or work less hard (turbo RPMs) to generate the same boost... Though I'm definitely no expert... I dunno what I'm missing that your BS meter has tripped, maybe someone who is an expert can clarify things?

[TheNewBlack]

It's already been clarified, to death.

[chromal]

It's already been clarified, to death.

So, then, having read the clarifications, are you saying that turbos don't make up a 2-3 PSI loss from 6-14k elevation, or, well, what ARE you saying? *scratches head* Personally, I just think it's interesting, thought a technical discussion in a forum like this would be an ideal way to learn more about it from like-minded folks in a club of people who supposedly are interested in this sort of thing....

[~Barn~]

"Your Mileage May Vary" is the best way to approach any technical discussions on this forum. =)

Seriously though, I think the biggest disconnect that comes about with conversations like these are the "it will be fine" set, not having the same perceived goals/conditions as the "need to make the most power" set.

I personally have advocated the you-can-use-low-ocatane dictum on this board, but I have also come to learn that if you choose (now that I am) to use higher octane gas in your forced engine, your ECU can actually compensate to *create* power.

Two totally different end-games of course, but both with equal validity. YMMV.

[erod550]

Or, if you're not going to get tuned, you could just run an OTS map made for 91 octane instead of 93 since that's what we have available. Cobb has both available.

[TheNewBlack]

So, then, having read the clarifications, are you saying that turbos don't make up a 2-3 PSI loss from 6-14k elevation, or, well, what ARE you saying? *scratches head* Personally, I just think it's interesting, thought a technical discussion in a forum like this would be an ideal way to learn more about it from like-minded folks in a club of people who supposedly are interested in this sort of thing....

"supposedly"

[chickenwafer]

If the 2-3 psi statement above is true, then why do even FI cars make more power at sea level?!?!

That sounds like a bunch of bullshit to me.

Because at sea level, there is obviously higher pressure ambient air pressure. So, they have a head start, so to speak.

To quantify:

Sea Level: Ambient air pressure- 14.7psi, turbo compress air to 10psi. Net PSIA is 24.7 PSIA

At 5000ft elevation: Ambient air pressure- 12.2psi, turbo compresses air to 10psi. Net PSIA is 22.2 PSIA.

Of course, these are generalizations, because ambient barometric air pressure changes greatly depending on atmospheric conditions such as temperature, weather, humidity, etc.

[iani1.1]

thank you sir. that was very informative.

[erod550]

Sweet, so that means I can start telling people I'm running 30psi (18+12.2).

[chickenwafer]

Sweet, so that means I can start telling people I'm running 30psi (18+12.2).

LOL, you could be accurate if you said 30psia

PSIA is Pressure per Square Inch ABSOLUTE, which factors altitude into the total positive pressure.

PSIG, the unit of measurement we all normally use, is Pressure per Square Inch GAUGE, which just measures any change in pressure from ambient. So most people who say PSI mean PSIG, usually PSIA is denoted.