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      06-13-2009, 07:58 PM   #1
dcstep
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Blending Fuel @ 5400ft w/ dyno runs

Some of you have been watching my struggle with tuning my 2009 M3 E92 at 5400 ft over sea level, just a few miles South of Denver. Expensive changes like Dinan throttle bodies and a Dinan chip resulted in a couple of hp. 100 and 105 octane fuel actually lost hp and the biggest gain so far came from changing the air filter!! My Macht Schnell filter netted me almost 6 hp over the other small gains from the Dinan mods.

Today I went back to the dyno with a blend of 91 and 100 octane unleaded fuel. The ratio was roughly 70/30 91/100-octane, mixed in the tank. I didn't mix it in cans, so I was relying somewhat on the accuracy (inaccuracy) of the gas gauge. The resulting octane is rougly between 93 and 94 octane.

The dyno shows a gain from 340.17 to 345.74 in peak hp with a comparable gain in peak torque from 245.55 to 250.12 ft lbs. The part that I really love and can actually feel in my butt is at 3000 rpm, the torque goes from 230.27 ft lbs to 244.23, an increase of almost 14 ft lbs. As you look at the graph I don't lose any torque at higher rpm, so this is a real gain over an important part of the engine speed range, from 2500 to 3500 rpm.

Remember, this info is probably only directly useful to those at altitude similar to the Rocky Mountain "Front Range" region of the USA (5400 ft). (You guys in Vail and Aspen are on your own). I've demonstrated that just adding as much octane as you can find does not work. Our theory is that the timing only advances so far and the higher octane just results in a slower burn and actually starts retarding the effective timing.

I'd be curious to read what happens at sea level when you go from 100 to 105-octane. PencilGeek reported roughly 30hp gain with 100-octane at sea level, so I wonder if the gains will continue, plateau or drop with 105. I think there's a chance it will drop. Also, given my experience, 97-octane might give more power than 100. You guys at sea level need to start experimenting with blending.

Next I'll try a 70/30 mix of 91/E85. My dyno operator thinks we'll surpass 350 hp with this mix. He has lots of experience dyno-tuning turbo cars running E85. He thinks that the extra oxygen and cooling effect will result in 6 more hp. We'll see.

I didn't show the AFR because the resolution of the graphs reduces the more that you try to show too much at once, but my tuner that if we can find a mapping program that he can get another 10-20 hp working only on the AFR. Let me know if you here of such software that can be licensed.

Dave
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      06-13-2009, 08:02 PM   #2
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Interesting. Keep up the experimenting I'm following this...

Also glad I can buy 93 at the pump here in NY
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      06-13-2009, 08:14 PM   #3
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Interesting. Keep up the experimenting I'm following this...

Also glad I can buy 93 at the pump here in NY
Yeah, but you'll gain even more by using 100-octane. Comparing 91 to 100-octane, PencilGeek gained about 30-hp at sea level in California. Your results should be closer to his than mine. Still, 93 IS better than 91 in all condition, so far. (I'd bet that the guys up at 7000 to 10000 ft are better off with 91 octane.

There used to be some 93 octane available here. I'm going to start looking again.

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      06-13-2009, 08:17 PM   #4
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Quote:
Originally Posted by dcstep View Post
Yeah, but you'll gain even more by using 100-octane. Comparing 91 to 100-octane, PencilGeek gained about 30-hp at sea level in California. Your results should be closer to his than mine. Still, 93 IS better than 91 in all condition, so far. (I'd bet that the guys up at 7000 to 10000 ft are better off with 91 octane.

There used to be some 93 octane available here. I'm going to start looking again.

Dave
There's a place 5 minutes away from me that sells 108 octane. I wonder how much I'd have to mix in a tank of 93 to get it up to about 97 octane or so... The stuff is close to $10 a gallon.
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      06-13-2009, 08:29 PM   #5
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Quote:
Originally Posted by J08M3 View Post
There's a place 5 minutes away from me that sells 108 octane. I wonder how much I'd have to mix in a tank of 93 to get it up to about 97 octane or so... The stuff is close to $10 a gallon.
100-octane tends to go for around $7.50, give or take, and you wouldn't need to mix if you could find it. You can build a little spreadsheet to estimate octane easy enough. Just take the percent times the octane then add the two results for the resulting approximate octane.

Dave
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      06-13-2009, 11:48 PM   #6
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Quote:
Originally Posted by J08M3 View Post
There's a place 5 minutes away from me that sells 108 octane. I wonder how much I'd have to mix in a tank of 93 to get it up to about 97 octane or so... The stuff is close to $10 a gallon.
108 is probably leaded. you don't want to run leaded fuel.
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      06-14-2009, 02:28 AM   #7
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Dave -

Thanks for posting the results. It is quite interesting. I guess an MS filter and race fuel is all ones needs for some more power!
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      06-14-2009, 08:54 AM   #8
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Dave -

Thanks for posting the results. It is quite interesting. I guess an MS filter and race fuel is all ones needs for some more power!

Has somebody done a stock baseline at sea level and just added the filter and 100-octane for comparison? I think that's going to be good for over a 10% gain in rear wheel hp. Not bad for a $99 drop-in part and a $4 or so increment in fuel price.

Dave
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      06-14-2009, 08:40 PM   #9
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As a fellow mile-higher will be following this post. Looking forward to the next installment.
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