Fluid Motor Union (mid-section) getting built/installed this week
I'm personally not sure what octane gas was used, but if I had to venture a guess, I would hedge my bets on good ol' 93 octane premium, since the C63 takes premium and Illinois only dispenses 93 octane from its premium pumps.
Would the AFR lean out even more if 91 octane was run? I'm in CA, where 91 is the "premium" octane.
I understand there is some range for a safe AFR on these cars, but I don't know what that range is.
It looks like this midsection makes considerable power. And realistically, by this dyno, it looks like it makes almost as much hp as LT's, give or take 10 rwhp or so. With LT's and no tune I would think the car may get too lean, especially with 91 octane, so I was just wondering if similar provisions should be taken with this midsection as would be taken with LT's.
Last edited by SonnyakaPig; Feb 21, 2011 at 02:48 PM.
Now, down to the nitty gritty. We did the workaround on the fly (as we didn't predict MB would add a support brace underneath), and it only took us about 2-3 extra hours to fashion the workaround. We are currently looking at other workaround ideas, as well; we have a prototype C63 midsection with us that utilizes a step-up before the x-pipe and step-down after the brace. The design to go around that brace might change again, as well (seeing that the step up and down will change the flow dynamics of the exhaust by a very negligible amount, resulting in power changes in the range of ~.1 hp, according to our testing), but the original "hump" wasn't factored into the price of the midsection.
Our goal in making this midsection was to perfect the fitment while leaving the vehicle as unmodified as possible.
What would you guess the HP diff between the 93 and the 91 we have here out west?
And after being told that there are a few gas station franchises in Illinois that run 91 (Gas City comes to mind), the owner could have used 91 octane in his tank, or had a hybrid of 91 and 93. I'm not too sure, we'd have to have him key in on this specific part.
Negligible, maybe a couple two-t'ree ponies overall.
And after being told that there are a few gas station franchises in Illinois that run 91 (Gas City comes to mind), the owner could have used 91 octane in his tank, or had a hybrid of 91 and 93. I'm not too sure, we'd have to have him key in on this specific part.
EDIT: Can you post the dyno chart with the TQ curves?
Last edited by Sincity; Feb 21, 2011 at 07:13 PM.
We're going to offer this midsection for $1499.
Yes, we realize that the price is a bit high, but we're not manufacturing these on a large scale, nor do we outsource a single piece of construction outside the shop. Robots won't be welding this exhaust, Tom and Craig will. These are basically made-to-order midsections. We also believe that the sound change and power gains over stock should help rationalize the price point as well.
We're not selling this as some sort of quick hack-and-slash job. We put a premium amount of work into the products we decide to sell, and we only sell them in small quantities, so we believe that marketing these pieces as a premium product is apropos.
Besides, compared to higher-end BMW products, it's actually not a bad price point. The Active Autowerke midsection for the M3 currently runs about $2000 dollars, and they use all the same materials that we do, plus a robot makes it, and they push those things out in larger quantities.
In terms of fitment, this midsection will fit up to the stock headers (or any headers that utilize the stock header flanges/position) in the front and the stock resonator box in the rear. More info can be gleaned from the longer post I made on the first page, or you can make a post on here/PM/e-mail me with any specific questions.



