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Old Tue, May-03-2005, 04:09:06 PM   #31
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That is a nice thread. Since we already have two people writing about superchargers, I should write about turbo right?
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Old Tue, May-03-2005, 05:42:27 PM   #32
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Quote:
Originally Posted by Kaiser Sausage
That is a nice thread. Since we already have two people writing about superchargers, I should write about turbo right?
Go for it. Start another thread.
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Old Tue, May-03-2005, 09:53:51 PM   #33
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So what's an optimal A/F ratio for a S/C'd M3? Consider both a "simple" bolt-on kit and a complete ground-up engine rebuild install.

And would the A/F have to be constant or could it vary, depending on throttle position and rpms? (Idle vs WOT@ 8,500rpm)

Hope I'm not asking a question that has already been answered.


Thanks,

Greg
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Old Wed, May-18-2005, 06:11:42 AM   #34
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I totally agree with ArtM3, without dragging this any further. Lowering the compression ratio will definitely increase the lifespan of a F/I engine. It may not be required for a mass produced F/I engine application, because the average individual is looking for longevity of their vehicle. That is why their boost levels are usually low between 5 to 9 psi. Higher boosts almost always require lowering your compression ratio. It's almost common sense!




Quote:
Originally Posted by ArtM3
I was comm'ing with Osh & Hammerdown...lol

the main point: in a NA engine the main force for filling the cylinder is atm press ~ 14.7 lbs

in a forced induction engine with 1 atm of boost, you'll stuff twice (1 atm + 1atm) as much charge into it, and twice as much power...

if you have 1/2 atm boost (~7.5 psi) you'll have (1 + 1/2 ~150%) more power, this is pretty accurate, if you ignore losses due to flow restriction, etc.

in summary:
Bogie gets (1 + 11/14.7 atm) or 175% more power
Scott gets (1 + 7.5/14.7 atm) or 150% more power
or Bogie shoul get 25% MORE than Scott...
1.25 x 380hp(Scott @ 6700) = 475hp vs Bogies 473 dyno, pretty damn close


the point being, the claimed hp is plausible, and with the reduction in compression (IMO essential, especially on an 11.5:1 Cr) and some better headbolts/gasket, should be very reliable, probably more so than an engine without the Cr reduction...more power AND robustness, pretty damn impressive, but not magic, just good, sound, engineering practice...
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Old Fri, May-20-2005, 08:37:44 PM   #35
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Default great stuff.......

Great topic on here regarding the forced induction stuff..... some of it really brought home some of the work I did when I upgraded my audi ur-quatto 20v engine....... I know you guys in the states never got this version of engine but all this talk of reducing compression ratios, boost levels not being the absolute be all and end all is true..... after I had finished the engine was pushing about E46 levels of hp but 400lb/ft of torque..... and to be honest comparing it to my e46 m3 there was only one winner in the grin factor stakes.... ok I know it's an audi but really the engine was only 2.2 litre capacity-).......... keep up the good work guys!!!!
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Old Tue, Sep-28-2010, 08:01:22 PM   #36
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Thanks. Excellent posting. I suppose I should have read this prior to installing:-)
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Old Sat, Feb-23-2013, 03:42:55 PM   #37
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Default Re: Forced Induction for Dummies

Wow I just came across this thread on the internet in a random search for something else. I haven't been here in forever.....no more M3......but hi guys, 8 years later! LOL
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Discussing Forced Induction for Dummies in the E46 FAQ Forum - at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)