IM 240 test

[Zedn]

Originally Posted by sideshow

there must be alot of undeducated exhaust shops around these days
it took me awhile to get any decent info from them

there are new aftermarket cats available these days
some are euro 4 compliant and i think are 200 ppi
i think ppi is parts per inch or something like that
its basically a figure for the amount of perforations in the cat
the euro 4 this shop were using had say a number of 200
then they said if u really wanted to pass then the very latest cats available where
euro 5 compliant and they have 400 ppi
which is double the holes in the honeycombe when compared to the 200 so the surface area of the material is double so they work much better
he said they use these now for cars that need to pass emissions

CPSI cells per square inch. I believe most OEM cats are 400 CPSI. Catalytic convertors require heat so need to be mounted as close to the motor as possible. On factory cars they have to trade off between close enough to work but not too close that they dont last. (Can you tell i was just on howstuffworks.com?)

In our application obviously space is an issue, but our cars dont really do that many Ks so durability is less concern.

Sideshow, when you tune a crate motor, do you use the fan output or standalone fan circuit? I wonder if a lot of the problems people have passing are due to the operating temperature being different to the factory setup. This combined with the spacing of the cats and could mean the difference between pass and fail.

If all else fails, piss into your exhaust. Apparently the urea does the trick.