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      10-20-2012, 10:13 AM   #10
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Drives: 2016 BMW i8
Join Date: Dec 2006
Location: Monarch Beach

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Originally Posted by pbonsalb View Post
You can make a little more or less boost just depending on atmospheric conditions. The blower spins at a fixed rpm, unlike a turbo, so it has zero adjustability. It can only compress what it gets, and what it gets is more or less dense depending on temperature and humidity.

The catless x-pipe reduces the restriction through the motor. This is why it adds power. On a boosted motor, boost is a measure of the restriction through the motor. Take the cork out of the backside and boost drops on a supercharged engine. Again, boost is fixed by the blower belt drive and has zero adjustability, unlike a turbo that will simply spool more or less fast to make the boost set by the wastegate.

Now raise the boost to ESS' specifications and you should see more power. However, I would first want to know why my installation made less boost than boost on identical kits on supposedly identical cars. There could be belt slip or a boost leak. Sometimes it is just a bad boost gauge, so I would want to check that as well against another reference.
Yesterday at EAS we double-checked for any boost leaks (none), blower belt slippage (none out of the ordinary) and pulley (correct one for 600 kit). Boost was also constant (4.9 to 5.1 psi) from my run a week ago where it was around 65 degrees compared with 80 yesterday (I made a little less boost yesterday).

EAS is also measuring boost @ the vacuum line like they do with all other supercharged M3's. They have dyno'd quite a few and so Steve@EAS was overlaying my dyno with others. Most others with the ESS 600 or VF 620 were 6-8 psi. Strangely, I made more power than most of these higher boost cars, which is why I'm not overly concerned. I have no idea why, but perhaps my car is just flowing better.
Daily: 2016 BMW i8
Airstrip: 2015 Porsche 991 Turbo S / GIAC FBO Meth 68mm turbos
Track: 2015 Porsche 991 GT3
Utility: 2012 BMW e92 M3 DCT
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