Mixing Fuels With Different Octane
 

Recently came from Florida were 93 octane is practically everywhere, aaaaaaand now I'm in Colorado where I believe there isn't a single 93 pump. The premium gas here is 91 octane.

The power loss is extremely noticeable, and I can't take it anymore. Maybe elevation has a factor in to with the feeling.

I've been referred to add a little e15 to the tank. However this to me sounds sketchy. I have also been referred to add a little 100 octane to the tank.

I just want to at least match 93 octane again, nothing less. Whats the best way to go about this?
How would this work with tuning, considering every mix will be different.

Most pump gas nowadays is e5-e10 anyway. The only losses to octane would be pulled timing due to knock. You have a logging device to check timing?

The power loss is 80%+ due to altitude. Higher altitude, less air density, less oxygen, less boom. That's the drawback of NA for ya. FI or deal with it.

Edit, just saw mod list lol I'm dumb. Uhhh idk what's up then. Altitude still probably plays a part. Add octane booster? Turn up the boost?

Yea I'm JDL Turbo'd lol. I want boost to a minimum. I actually switched to the 5 PSI wastegate spring and it felt fine in florida. I figured it'd be the elevation but however comma, I did have some 93 left in the tank when I started driving in colorado and that still felt fine to me, I mainly felt it while staying on 91 for the first two weeks till now.

Add a little Blendzall 485 Racing Castor, it will slow the burn and give you a cool, racy smell.

Hey, Spuds ....... you wanna correct that statement ........;)

(or am I misreading it ..??)


humfrz

Nope.

So, are you saying that stock FR-S would lose 80% of its power at an altitude of 14,000 ft., compared to its power at sea level ..... ??


:confused0068:


humfrz

So do you have a way to log timing? Octane should only really affect knock compensation stuff right? If the ECU is pulling timing then yes, adding octane booster of some sort to every tank should help bring timing back up. 91 vs 93 octane has no more or less energy than the other.

So I'm not too familiar with how your blow off valve works, but if it's regulated by a spring, it's likely based on pressure differential to ambient. Ambient pressure at 5000 feet is about 2-3psi less than sea level under the same conditions. As far as your initial driving, pressure changes with weather so maybe that had an effect.

I think he is saying that of the power loss he feels he is missing - 80% of THAT LOSS is coming from the altitude. I think.....:thumbsup:

Not 80% of the overall power.

I would think that a car reduced to 34 WHP would be deemed more than "noticeable".

I do data logs and send then to my tuner, James Martin.... I have already updated the tune to this location and 91 octane...

I don't quite get your statement about psi and elevation. I am set to 5 psi spring, which usually goes to a maximum of 8 psi. You're saying that I'm actually getting 2-3 less of what my boost gauge reads?????

Well I would think your boost gauge would read absolute pressure but I really don't know how turbo stuff works lol. Hopefully someone can help you out.

Now, that makes sense. I reckon I was reading what he ( @Spuds ) said differently .....:bonk:


humfrz

It says it blends with premium gas. So you use this mainly as a safe factor or for driving feeling

I have a few motorcycles that are pretty high compression and I throw a little 485 in there to help quell detonation, especially if I get some lower octane gas than I really want to put in them.

I have been using it for many, many years and in my experience it works well.

FWIW, the bikes are injected and have cats, no problems. In fact, seems to keep things very clean.

Since the castor is a lubricant I think I will try it when I get the crickets, who knows, might help. :iono:

I read it as meaning "Makes only 80% of its power at elevation," or losing 20% of it's power, with 80% remaining available. Fun... three different interpretations of the same statement, with VASTLY different meanings and conclusions. One literalist whose interpretation is completely justifiable based upon the original statement yet probably not at all what the original poster was trying to say (Humfrz), and two interpretations by folks trying to figure out what the original poster truly was TRYING to say (me reading it as 80% of the power, and SCQTT reading it as 80% of the REASON for loss of power is due to elevation) Hmmmm... wonder if there's an allegory there anywhere in today's journalism.... oh, never, mind.. ;)

Let's do the thing the journalists don't seem to ever do or care about.. let's find out what the O.P. REALLY meant..
@Spuds ?

Annd the winner is... @SCQTT! 80% of the perceived loss is due to altitude was the original meaning. Maybe I was wrong anyway.

Well, good to get that clarified .........:thanks:

I suggest you get that 80/20 rule clarified prior to your wedding day.

You: you can be right 20% of the time .... and I'll be right 80% of the time

Her: Nope

You: OK, You can be right 80% of the time .... and I will be right 20% of the time?

Her: Nope

You: OK, what % of the time can I be right?

Her: Depends on what % of the time you want to be happy ......:D


If you don't want to believe that ...... check back with me in five years .....:eyebulge:


humfrz

What about a water/methanol injection system?

Only a pussi run on meth

According with Dom Toretto

WTF!! You looked under my hood?

So far, only boosters and water/meth..

No one has mixed different octanes?

It's fine. People mix different octane fuels all the time. It will blend and average out. If you can find premium somewhere that is.

I thought you were talking about mixing different types of fuel. That's also done quite a bit. As I said, most pump gas in the US I've seen is up to e10 (10% ethanol) anyway. Usually there's a disclaimer saying so at the pump.

Maybe I don't understand the problem?

Mixing is no problem. Don't know why this is even a question.

Not so much questioning the action of mixing but the portions of mixing. For example... 8 gallons of 91 octane, mixed with 3 gallons of 100 octane... how much octane would that total. I honestly haven't heard mixing with 100 octane being a problem or not, just looking for peoples experience.

Edit: I did come across a conversion chart, that may have answered my main question.

http://www.e90post.com/forums/attach...1&d=1197922704

Just wanted to hear people experiences before I do something stupid. Ive never mixed different octanes so...

I was also recommended e15 but it looks like thats about 88-90 octane, but more ethanol of course

I would talk to your tuner about logging your car and checking it out first. You may not even need 93, 91 may be perfectly fine.

A chart for those who are math challenged ..... :D


humfrz

Yep, someone once said that engines can get by with gas with lower octane ratings at higher altitudes ...... :iono:


humfrz

Not sure math challenged over..... fuel challenged?

Us married people know how to calculate this real well.