Tuning Motronic to burn very clean for MOT / NCT without cats

[prj]

Against all recommendation, I did order the 5" 100 cell cat. It sure has great flow area and should not be restricting the flow in any way, I hope... If I had ordered a cheaper cat and a bunch of v-band clamps it would have cost me the same, and I still have to change it before and after every MOT.

I think it will restrict...

Will become clear when mapping, if it starts knocking like crazy you will need to use your welder to weld that **** out really quick

[Thuppu]

Ahaha, maybe I should fit the v-bands anyway so we skip the cutting and welding thing then..?

Edit. In fact that would be fun to test, does a high flow cat add restricton, and how much vs. a straight pipe? Maybe I should fit a pressure gauge to the exhaust after the turbo...

[prj]

I can tell you without pressure gauge by seeing when it starts to knock.

[Rikki Kitto]

Get to know your tester a little better

[Thuppu]

Really hard to find any info of the flow of sport cat's. Here is one dyno graph 100 cell vs. straight pipe. http://forums.evolutionm.net/evo-eng...-cell-cat.html 5hp/11Nm drop at 300hp level(had to drop the boost, knock??), so on the double hp level the restriction can be a lot bigger. Of course the diameter of the catalyst does matter, 4" vs 5" has really big difference. Don't know what the size is in the link..?

[prj]

Well, as I said, from a tuning perspective - it increases the backpressure and that lowers the knock threshold...

[Thuppu]

Ok, I think I weld v-bands before and after. We can then test how much it affects the flow.