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      10-03-2019, 05:39 PM   #1
wrk.eat.drive.rpt
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Drives: 2016 340i, 08 e92 m3
Join Date: Aug 2017
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Restrictor Baffle on M Coupe to open up power+ sound?

Saw this post on a recent BAT posting of a Z4 M coupe.

Any insights/validity/or folks that have actually done it? Very curious. (not saying it will make 30hp- but just the general validity of the claim of opening up air flow and making more power)


Repost his long post below- original BAT link- https://bringatrailer.com/listing/20...z4-m-coupe-41/


User: jkkerouac

"Own one of these already. Bought it three years ago and its the one BMW keeper I canít imagine ever selling (except if someone makes me an offer I canít refuse, but will still want a Z4 M Coupe anyway because I canít imagine any BMW of the past or future,that gets my yayas out even close to what a Z4 M coupe can do, and I say that based on having owned, driven, and modified nearly all series since the New Klasse)

This is really a 360 hp engine that BMW restricted the intake on to keep the same 330hp rating as the earlier Bosch controlled S54.
It easily blows the doors off of an S52 Z3, and pulls away nicely still, from the early version S54 in the Z3.
The S54 in Z4 M Coupes is the Siemens controlled version, with an actual 30hp more than the 330hp rated S54 in the E46, and 315 rated hp in the S54 Z3, let alone the 240 rated hp in the S52 Z3.
BMW kept the same 330hp rating by putting a restrictor baffle in the air filter box, above the air filter. Snap out that babble, remove the screen in front of the MAF sensor, and the measured MAF flow increase calculates out to another ~30 horsepower. Yet this Z4 M Coupe weighs barely more than the Z3 Coupe. Note that I said ďmeasuredĒ, and have the actual data logs that show 217g/sec before, then 257g/sec after.
With the 3.64 rear and six speed, the gearing and overall final drive ratio makes this far faster than any Z3M, even if you gave the Z3ís S54 the same 360hp engine as the Z4M has.

Also, the Siemens version S54 is exclusive to the Z4M. Its the final build, with all the correct bearings and vanos bolts and gaskets and seals and everything else that were trouble on the Z3 and E46ís version of the S54.

For that extra 30hp:
First get baseline numbers. Spray clean the MAF sensor, and use a clean K&N or Pipercross air filter.
Measure MAF flow before. Use third or fourth gear for more stable MAF flow readings. Take a few passes to get your best numbers. I had 217 g/sec at between 7700 and 7900 rpm.
FORCEFULLY snap out the air baffle from the top of the air filter box.
Unscrew and remove the screen in front of the MAF. Do reinstall the air horn. Remove the rubber gasket between the airbox and radiator support. Probably will want to dump out the little sandbox that accumulates in the bottom of the airbox.
For completeness, I also put a silicon intake boot. No one makes one for the E85/6, so I used Turnerís E46 boot that I recut the length and plenum mating angle to fit the E85/6. The 12 year old factory accordion boot was getting brittle, and I like to make my cars more reliable as well as faster, and still pass smog legitimately. To keep the vapor return line active, then use 3/8? inch fuel line hose to route the return hose that used to go to the boot, over to the intake chamberís bung that the hose would attach to on an E46. Complicated to describe, simple to do.
PM me and Iíll send a pic of the boot and rerouted hose. Didnít increase total flow but did increase midrange a bit.
Measuring after, I had 257 g/sec max at close to redline.
Rule of thumb says that half the flow increase = power increase.
The math is:
40/217 = .018433
.018433 / 2 = .092166
.092166 x 330 = 30.5 hp.

hat 30hp comes from removing the restrictor baffle in the top of the air filter box that is snapped in above the air filter, plus removing the screen in front of the MAF, plus removing the rubber gasket between the lower air filter box section and the radiator support.
My í07 MCoupe measured an 30.5 effective HP increase on my í07, based on measuring the increased MAF flow from 217g/sec before up to 257g/sec after, using the rule of thumb that Ĺ the flow increase is the power increase. The math is (257-217) / 217 /2 x 330.

Keep the MAF sensor clean and index your spark plugs for most accurate metering and combustion.