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      04-23-2011, 03:16 AM   #11
mikelaca
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Drives: 2010 550i GT
Join Date: Sep 2010
Location: So Cal

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Quote:
Originally Posted by smmmurf View Post
We have all seen Pencilgeek's dynos which show a 30+ ft-lb improvement around 2-3k and ~35hp around 8200, but the peak figures do not tell you what the actual improvement in driving feel is.

The car runs noticeably smoother and less jerky, especially when cold. It has a lot more low end torque below 3000 RPM in day to day driving.
Ok, so I read this thread and thought yeah right. Please, slightly higher octane (9) will make that much of a difference. Bull. But being that it was a Friday night and I had spare time on my hands, and there just happened to be a 76 station selling 100 Octane ($10/gal) a few miles away, I thought, OK, I"m going to test this out and then call BS on this post.

So I drove to the station and filled up my car with 65% 100 Octane 76 Gasoline, 35% 91 Octane Shell. Then I drove off.

I should now say that my 2 biggest complaints about the M3 is the fact that it SUCKS in low end torque and is herky/jerky. The jerkiness is very noticeable when slowly driving off from a light, and the lack of low end torque is especially noticeable when you decelerate rapidly, take a hard right turn, then jump on the gas exiting the turn, there's just a dead/slow second before the engine really kicks in.

So I drove around with the Gasoline blend, and I must say I'm stunned. Floored. Flabbergasted. EVERYTHING the OP said is true, and then some. The car was not jerky once, not even with the power button engaged.

With the Power button disengaged, it felt like it had the HP of when the Power button was engaged on 91 Octane.

Low end torque is back, it now has torque in the low end like an AMG or 911. Moreover, the RPM needle is SO SILKY smooth and linear throughout the rev range. It pulls strong and smooth like a tug boat. And when just cruising the engine is smoother.

Also, in reverse, which is always a too hot/too cold endeavor, reverse is now linear and like a 335.

Honestly, the car is as smooth as a V-12 760Li but as torquey as an AMG or X5M.

I am beyond stunned. I feel like I just went from a 328 engine (my 91 octane M) to a V12 760Li ( my M with this 100/91 blend).

Words can't describe the difference.

So my questions are:

1. This is REALLY expensive. Honestly it would be cheaper to pick up a meth or crack addiction. Is there some way to get the similar boost for less money, such as those fuel additives/octane boosters they sell in car part stores?

2. Why does barely a 10% boost in octane have a monstrous affect on performance. What is the science behind it?

3. Why does the M engine benefit from it so much? I know Porsche, Mercedes, and other engines drive with a smooth rev range, tons of low end torque on 91 octane, Sure they probably would drive better on 100 octanem but they drive fine in low speed/low RPM on 91. Yet why does the M engine seem to need 100 octane in it to be more useable daily than almost any engine out there? There's gotta be something about the engine. Is the engine just so damn high-end F1 derived that it can't function nearly as well on "everyday" fuel? Kinda like you can't put a supercomputer in your home even if you have the space because you'd need industrial A/C Refrigerants running 24/7 just to cool the room?

And I'd encourage anyone reading this who has any torque/smoothness/jerkiness complaints to do the test I did. You won't believe the difference. I'm going to be so sad when this tank runs empty and I have to go back to 91 octane.