So I am going to be taking my Mini and another Turbocharged car (that requires 93) up to altitude.

9000' is where it'll be parked, and there are several 10,000'+ passes.

The question I have is octane, or lack there of in Colorado at this altitude.

The highest octane in a few remote mountainous areas I've found on is only 87

91 was available near the airport and in Boulder when I was there...

I know that air is less dense at 9000' than 182' where George is currently garaged, but being a completely stock '06 R53 MSC, there is a supercharger there.

So will the compressed air going into the cylinders be at the same pressure as it will down here at near sea-level and I need to get several cases of octane booster?
or
Will it be down the same % from going to 9000' and 87 octane will be fine?

BTW, I usually run either 93 (since most pumps in N. NJ have 87, 89, 93) or 91 (Sunoco only).

 

I have had no real issues with 91 octane at altitude. It's also normally the highest octane they sell here in Co. I don't think I would use anything less (87).

 

Take the 325xi, especielly if theres snow


Jack

 

A supercharger operates at a constant ratio to the crankshaft, unlike a turbocharger. In this case, the pressure ratio remains fixed. As atmospheric pressure decreases, so does your manifold absolute pressure. So, calculate your pressure ratio (if your current manifold pressure is known) and then calculate the manifold pressure at 9000'.

In a turbocharged vehicle, the ECU/boost controller/wastegate is calibrated for a certain manifold pressure. As the compressor is not directly linked to the crankshaft, it can spin faster to accomodate a higher pressure ratio (but same boost level). This phenomenon can result in over-spinning the turbo and subsequent turbocharger damage on cars which have undersized turbos from the factory. The Audi S4 (2000-2002) comes to mind.

Would I recommend taking octane booster? Yes. Even on moderate-performance NA cars I've had knocking issues on 89 octane. Bear in mind your bottles of octane booster will only raise the octane a few points (ie: 87 to 87.5). If you really want to boost octane, buy a couple gallons of Xylene or Toluene from your friendly local home improvement store. These are the active ingredients in octane boosters and have an octane rating of 117 and 114, respectively. They should cost about $15 a gallon... which is MUCH better price than your average bottle of parts-store octane booster.

 

My 07 MCS has no issues with the Colorado 91 premium. No problems in the mountains above 11,000 feet, either.

I had heard (may be an old wives tale), that the MINI 02-06 and 07-08 does not like the octane booster. Any comments or other thoughts?

Don

 

Have you tried this on your MINI? What ratio to gas do you need? Just a gallon in then the rest is fuel?

 

The formula is simple. Gallons of Xylene or Toluene x 117 (or 114) plus gallons of gas x 92 (or whatever octane gas you are using) divided by total volume. For instance: 10 gal of 92 octane plus 1 gal of xylene: (10x92 + 1x117)/11 = 94 octane (rounded down due to significant digits). We used this on an SRT-4 with great results at the drag strip. Ran the best ETs and trap speeds the car ever did using a ratio of 3X:4G... although when cold the atomization was so poor and the octane so high, the ignition system was not capable of igniting the mixture! Solution: add more gasoline to dilute the mixture back to a reasonable octane.

While I haven't tried it in a Mini, the principle is the same for all gasoline engines. Don't get greedy and raise it too high or you will run into trouble. Unless the fuel lines are made of macaroni noodles or the fuel tank is full of chocolate syrup, I wouldn't expect any trouble when used in a Mini.

A gallon of either of these solvents costs about $15. Some areas have banned the sale of Toluene beacuse it is environmentally unfriendly. It is highly volatile (by which I mean it evaporates rapidly, the REAL meaning of volatile) so it is considered a contributor to smog. Xylene is its slightly less volatile, more expensive, and higher-octane brother.

In the end, a gallon of Xylene or Toluene will cost about the same as buying race gas, but the advantage is you can go down to Lowe's at 8 on a Saturday night and pick some up before you head down to the drag strip. Also, it can be hard to find race gas that is unleaded in some areas. Leaded race gas does bad things to the O2 sensor and catalytic converter.

Please note: Xylene and Toluene are chemically related to gasoline but are found in the solvent section of the hardware store. Don't get it on your paint.

 

I might just be tempted to try this, what's the worse that can happen? Destroyed fuel pump, erroded fuel lines, messed up injectors, damaged fuel rail, soil the O2 sensor, melt the Cat...ok, maybe I won't try it.

 

Wow I've never seen a community so afraid to try "new" things. This has been used the world over by motoring enthusiasts. Toluene is one of the principle components of gasoline. The fuel pump is designed to pump it. The fuel lines/rail/injectors are compatible with it. It does not contain lead, so your O2 and Cat will fine FINE.

Toluene was called the "rocket fuel" of the Formula 1 turbo era because it virtually eliminated any possibility of detonation. We are talking about using it in small quantities to boost octane a couple points and add a margin of safety. The hardware is compatible and detonation is reduced, so what's the problem?

If you can find anyone who has had the problems you list, then feel free to post their testimonials. However this is a tried-and-true method of safely boosting octane. Do a google search! I'm actually rather surprised that the Mini community has never heard of it until now.

 

Did a googel search, according to european car running to much [toluene] can destroy your emission control systems. Basically due to the fact that still burning fuel is being shot out the back of your engine, although this only seems to apply to "high revving" cars according to them.

http://www.europeancarweb.com/tech/0...ted/index.html

Basically, it looks like as long as run high grade stuff [toluene] and dont use to much of it, you should be fine. I myself wouldnt want to use it every day, but could see myself using some for AX or something.

 

Well, I have never heard of that stuff till I read this thread. I was only listing those things as something that could go wrong if something did. The 91 octane around here works for me, I'll stick to it for now.

 

Well when my Mini has a carburetor, I'll start worrying about the results of that test. Good info though. Gotta love EC's testing methods. When testing varying levels of toluene, they experimented with 10, 20, 30% levels, but when comparing to other octane boosters they used .64%. WTF?

 

I love reading threads like this....

Here's the issue:
'86 944 Turbo: Manual Boost Controller, Larger K26-garrett turbo (NO chance of overspinning that thing) new TIAL wastegate, aftermarket ECU, new knock sensors...

The WG operates on absolute pressure.
The Turbo gets its power from the exhaust stream... the compressor has less air to compress, so boost comes on later but it still generates full boost.

I will be making 93 octane gas blends (or dialing back the MBC)

Now, I have no idea how the setup works on the Mini...
The car is completely stock except for a set of winter tires/wheels in the stock sizes... (17")

So, what I'm understanding is that the SC compressed less air (as there is less air to compress) and it cannot build up pressure to an absolute maximum via a WG like the 944... therefore the lower rating of 91, which Mini recommends, is fine...

 

My buddy also has an 86' 944 turbo, With the kkk series turbo and is pushing 27 or so psi aorund 350..

 

my mini lives at 10,000 ft, and I run 91 octane ( all they have here) and it runs fine.

I don't know where you will be traveling, but I-70 from one side of the state to the other has 91 octane readily avaliable

 

FYI:
They have 91 and 93 in Steamboat.

 

Precisely. Simplifying the explanation to pressure ratios is not technically correct as the Roots blower has no internal compression ratio, but it helps conceptually link the difference between a crank-driven and turbine-driven "compressor" at altitude.

In actuality, the M45 does not compress the air, it just pumps more than the engine can consume. The engine desires to consume air at the same rate (lbs/min) but the blower provides fewer lbs/min at altitude. Work the math backwards a few iterations, and you will find that the result is reduced manifold pressure.