BMW 540i on Dyno with Resonator and Silencer Removed

This was the second run of the day and is after removing the resonator and silencer and replacing with straight pipe. Modification resulted in a net loss of HP and Torque in the midrange of the powerband. Test run in 4th gear because dyno owner did not want 5th gear (1:1) speeds on his equipment.
267.0 hp @ 5750 RPM
264.4 ft/lb torque @ 4750 RPM
Vehicle: 1997 BMW 540i 6 speed
Modifications from stock:
Resonator and Silencer removeed
Royal Purple ATF transmission fluid
Electric Fan conversion
CDV Removed
M3 short shift lever

Category:

Autos & Vehicles

Tags:

• 540i
• dyno
• exhaust
• resonator
• silencer
• BMW
• 1997
• E39

[qcdstick]

Since this video has been getting popular again all of a sudden, here is the information from the day of the dyno.

ht tp://picasaweb.google.com/nbur­ress/­ExhaustModSpring2008

It has the dyno charts, A/F ratios, raw data etc... Pretty much everything I have on it. Some of you more technically minded people can mull it over if you like.

[qcdstick]

@qcdstick Just a head's up, you'll aparently have to type the link into your address bar... Youtube inexplicably is adding a couple "-" to the link so you can't simply remove the space and copy paste.

[540i6E39]

It could also be that the car hadnt adapted itself yet to the change in back pressure. wonder if you dynoed it after resetting the computer and driving for the 3 cycles if the numbers would be higher?

[qcdstick]

@540i6E39 It is possible, I'm not really sure on the finer points of how all that works. I don't think a re-test after adaptation would be meaningful since the atmospheric conditions would be a lot different by then. That, and it has been a few years since I did this so the car has many more miles than it had then also.

I will say that I like the change, and don't notice or miss any power loss that may be there. To my butt-dyno the thing still hauls some ass and sounds good too.

[theapeman1989]

wow! so you lost 3hp and almost 20 torques? something doesnt sound right

[qcdstick]

@theapeman1989 It is an engineered tuned exhaust system... The results are not all that surprising when you take that into consideration. There is nothing else to explain it; same car, same dyno, same day. The only thing that changed was the exhaust setup. Pretty cut and dry results.

[IPGAuto]

@qcdstick - Removing them caused less power? I'd throw on a catback and get rid of the resonators. Just to have that back pressure. I noticed a torque drop after doing a muffler delete.

[540i6E39]

i actually gained hp by going to a 3" catback with a magnaflow no chamber so in reality it sounds to me like your car hadnt adapted yet. i would almost bet that if u dynoed your car today even with your miles u would have a gain not loss.

[540i6E39]

well removing the resonator and silancer wont make u lose back pressure or if it does wouldnt be enough for u to have a 10hp loss... removing the muffler or changing to say a magnaflow muffler would make u lose some back pressure which is the whole point of changing it..

[cconant13]

@qcdstick Well it's not ALL the time, just when it's 110+ out and I'm sitting in traffic. The clutch is fine - I can stop the fan with my hand at idle, spin it backwards, etc... unless it's locked up because of the immense heat, of course. And it always disengages above 3000-ish rpm.