JSAautomotive
Banned
- Joined
- Apr 21, 2006
- Messages
- 3,564
They insert the "probe" into the tailpipe while the car is on the dyno. IM240 has hoses the slip over the whole tailpipe, hence "volumetric", whereas and ASM test (which also includes using a dyno) just has a probe that inserts in the tailpipe to take a "sample" of the emissions. ASM uses a math logic to come up with the PPM (lbs per millions) while IM240 uses the grams per mile factoring which is more accurate. It measures everything coming out of the car.