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Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 07-15-2015, 12:27 AM   #61
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Join Date: May 2015
Location: Seattle
Posts: 56
My Ride: E46 325ci
Originally Posted by PEI330Ci View Post
OEM Piston:

3.7mm down from the deck @ TDC

Ready for CC'ing:

Adding water:

17.4cc total volume
Bringing this thread back from the dead. Great stuff btw!

Here is my question:

Your measurement shows the lip of the OEM piston being 3.7mm down from the 211mm deck. This comes to 211-3.7=207.3
However, if you go this route: 44.8+135+28.32=208.12

Why don't these # match up? Furthermore, what do you think the static CR would come to using the following:

28.32 CH
138mm rods
84 crank
211mm block height

This would essentially push the piston further up by 0.2mm.

My plan is to use the 84 crank with the m54b30 pistons and the longest rods available without going custom pistons. Honda rods will fit the bill with slight mod to the width of BE and SE.
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Old 09-23-2018, 07:59 AM   #62
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Join Date: May 2005
Location: Belgium
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My Ride: BMW 330i
Originally Posted by PEI330Ci View Post
I've measured this stuff a number of times, and I'm still coming up with the same numbers. So here's what's been bothering me:

Cylinder bore = 3.307"
Stroke = 3.528"
Combustion chamber volume = 34cc
Piston/cylinder volume below deck = 17.4cc
Head gasket thickness = 0.030"
Head gasket bore = 3.346"

Plug all those numbers into a compression ratio calculator and you get 9.911:1.

BMW advertises 10.2:1 for the M54B30

The only thing I can guess is that BMW is not including the volume inside the spark plug, and the area above the first piston ring along the cylinder wall. The actual "pour volume" using fluid equals 55.723 inside the combustion chamber with the piston at TDC. Dropping that by just 2cc brings the compression ratio to 10.24:1, which might be the case if you didn't include the spark plug volume ect....

I'm sticking with real world numbers, so the M54B30 in my books is a 9.9:1 engine.

The CP pistons I have pictured above netted a compression ratio of 9.26:1 with a "pour volume" of 60.823cc.

Using a well known engine calculation software package, I was able to build a "model" of my engine to represent the actual power it made on the dyno. (252hp/229tq)

I then changed the compression ratio from 9.26 to 11.4:1 and netted a calculated 265hp/241tq @ 6400 RPM which was closer to what I was expecting when I built the engine.
Have you incorporated head gasket compression? I used 0.8 factor, giving a true 10.06:1 or simply 10:1
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Old 08-18-2019, 01:01 AM   #63
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Join Date: Jan 2015
Location: Melbourne, Australia
Posts: 514
My Ride: '98 E46 323i
Year: 98
Model: E46
Transmission: Manual

What is the maximum compression you think can be run on pump gas(US 93AKI/98 RON) while keeping a fully functional vanos? M54B30

I am looking at running 12:1 static with 266/258 Cat cams with full coatings etc.
Aftermarket DME with FFT based knock detection and alcohol injection to help with knock and intake temps.

Power is knowledge, So share the knowledge!!

Last edited by Blu302; 08-25-2019 at 10:49 PM.
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