Having adopted 7 exhaust units (three '05 and newer model years) to store in my rental shed (just 5 more and I can start the 12-step program!!), I got to talking with Hank at Rhinewest about the change in construction parameters that I thought occurred in '05. He confirmed it, and wuz aware of it due to the many swap-outs he has made whereby the OEM units were exchanged for the Remus setups.
Using a dial caliper (micrometer is what I call it?), I measured the exhaust flange I.D. and O.D. of the units. All measured identical in mm. Then I measured the O.D. of each of the exhaust pipes. These pipes snake around each other before combining to go into the collector just before the O2 sensor, near the catalytic converter. There are two different measurements evident.
32.5mm O.D. for the '99 - '04 units.
34.9mm O.D. for the '05 - up units.
These measurements are as close as I can get, using well-worn eye-candy checkers!!
My question to Hank wuz; why? He sez he thinks it has sumpthin' to do with the change in HP, beginning with the '05 model year; that the change for '05 and newer models resulted in freer/better exhaust flow; AND that if one were to install a larger O.D. unit on a '99 to '04 engine, and not modify the Motronic programs, the engine idle may be affected, along with some other less than desirable performance factors (likewise a performance hit with an '05 up unit, installed on a '04 or prior model). He stressed that it wuz only his
opinion, and that there may be more to it than that.
Sooooo - is there??? I certainly don't wanna give/sell an exhaust unit that is not model year specific for installation. Hoping to hear from some of you mechanic/engineer types with good info. Thanks in advance.