I would think this design will cause turbulence then right into a bottle neck. This could end up hurting more than helping. Also, you might run into fitment problems. You are better off as other have said with one large cat.

Honestly, this is the trade off. Is the headache really worth a couple percent of power? You are still never going to be as efficient as a TP. for 10-15whp at 500whp, who cares?

 

I believe you're THE FIRST "green" evo owner in the community

I truely respect that!!

 

I think you make a good in the second paragraph. Is the % difference BETWEEN a single and double 100cell cat worth the headache? Let's see:

At 500whp:
300 cell HFC vs Test Pipe = ~-50whp
100 cell HFC vs Test Pipe = ~-30whp
Custom 100 cell HFC x2 vs Test Pipe = ~-10whp

That is a worst case scenario. So i guess it's probably not worth the headache after all. O well.


Haha, i wouldn't quite call it green. It's certainly no greener than anyone else running a stock cat haha.

 

My $.02;
If you are going to spilt the exhaust flow into two cats, keep it seperated and just do the dual exhaust thing. As mentioned before, merging them back will lead to more turbulance.
Let's find out if two cats flow better than one.

 

I agree that you are halfing the restriction by doubling the cat, but the gains will be more like 10whp if I had to make a guess. The biggest issue with your design is size; simply put, 2 3" cats would not fit very easily under the car as they are competing for space with the driveshaft. Another option would be to weld the milspec 100 cell cat further down the exhaust towards the tip.

 

2 cats will flow better then 1, but the apllication does not fit, and you can argue the cost of adding a second cat for 10whp as worthwhile or not.

 

I highly doubt adding this customer setup would only net you 10whp at 500whp over a single milspec cat.

But other than the difference in savings (10whp and 20whp) going from one cat to this custome setup, and fitment (which i'm not sure of either) you're in agreement right?

I'm tempted to try it just for testing purposes at this point haha.


But Like MR Turco mentioned, the headache of ~20whp is not worth the time and money of a custom setup.

here's the final drawing of what I would have tried if i went through with it lol.

 

So that setup looks like you had the right idea if you did go through with it. Keep in mind tho, the more power you make and the more the "cats" flow, the less they are actually doing their job. It kinda defeats the point of refusing a test pipe. just my 2 cents

 

thats the design I was referring to. but with 2.5 pipes it will be about 6.5 inch width instead of 7.5 for dual 3s. 6.5 width will fit under car, the 7.5 will not. The splitting of pipes into two 2.5 will not be a restriction compared to running into 200 cells of cat a few inches later.

 

I'm in agreement about the 2 cats flowing more. With the second drawing you will have some turbulence from the different exhaust velocities merging in the same place...not sure how much that will affect things though.