A Evo came in today to switch from a test pipe to a 130 cell metal substrate high-flow cat because he wanted to get rid of a little stink and make the car a little quieter.

A 130 cell metal substrate is much more free-flowing than a 300 cell metal substrate cat, and even more free-flowing than a normal ceramic "high flow" cat.

I threw it on the dyno to check for any power changes and make any adjustments needed because of the switch.

Some interesting stuff happened.

Here are the power curves just strapping it on the dyno, no tuning changes whatsoever.

Dotted lines are 130 cell cat, solid lines are with Test Pipe:



Down in power from peak torque all the way to 7100 rpm. -17whp / -11wtq

Now, looking at the boost log, you can see why.

Dotted lines are 130 cell cat, solid lines are with Test Pipe:



Down on boost through the whole rev range. -2psi on average.

So at this point I am thinking the drop in power is because the wastegate duty cycles in ecu-boost just need to be adjusted because of the added back pressure from the cat. So I matched the boost as close as possible to when the car had the Test Pipe:

Solid lines are 130 cell cat, dotted lines are with Test Pipe: (the dotted and solid plots switched for this plot, my apologies)



Notice that the cat boost plot is not as smooth as the test pipe plot, also it has small fluctuations throughout the plot where the test pipe plot is pretty solid.

So now the boost was back to matching what the car was making with the test pipe, so the power curves should be closer to matching right? Well, yes and no.

Solid lines are 130 cell cat, dotted lines are with Test Pipe: (the dotted and solid plots switched for this plot, my apologies)



Curves match exactly now, until approx 5,500 rpm where the high-flow cat just cannot match the flow of the test pipe. Peak horsepower still down 16whp. 6500+, down more than 20whp.

Very interesting test case indeed. Now I wonder what a 100 cell cat and a traditional ceramic "high flow" cat would see in differences.

 

Wow, once again this is some great information. other then the test pipe what does the car have for mods? Is this the stock turbo?

 

I read it and think what you are saying is the high flow cat cannot match the power of the offroad pipe, is that right?

 

Evo 9

WORKS throttle body
WORKS 76mm DP
WORKS 3in TB exhaust
Cosworth 272 IX cams
HKS exhaust adjustable cam gear
SAMCO IC hoses
Nisei LICP
Denso 720cc Injectors
GM solenoid
Perrin FMIC
Hyperforce System
RRE rally cat
GST SuperDuperDefcon5 open air filter
Titek tubular 02 housing
Ported stock exhaust manifold
Ported and coated hotside
ARP head studs
FP actuator
Stock evo 9 turbo (ported)

Strongest stock turbo Evo on our dyno. Before this highflow cat it held the stock turbo record on our dyno with 91 octane at 339whp. To put that in perspective, even some FPgreen equipped evo's don't hit that on 91 oct on our dyno.

 

Turco, I think its time for a test pipe on your baby

 

Yup, past 5500 rpm you can see the high flow cat loses power over the test pipe, on this Evo.

btw, this "high flow" cat was a $700 "JDM" unit.

 

nah. I will get a nice high flow cat though. It is still only 4.6% gains from the test pipe. I like the sound the cat adds to the exhaust anyway.

 

Get a good metal substrate cat like this one if you really want one. Cobb makes a good one as well. Also the forum member "atvalet" can source 100 cell cats as well.

I can imagine a 300 cell metal substrate cat or the traditional ceramic high flow cats would be a even larger difference in power. The ceramic cats are like putting a brick in your exhaust stream.

 

I was debating between the perrin and cobb. I would never put ceramic in, like you said a brick.

 

I like the cobb unit better personally, I think it's cheaper as well.

 

Actually it is about $70 more IIRC. I actually think they are the same but i dont have any empirical data to prove that. I know the Cobb has a 300 cell core and i believe the Perrin is the same.

 

Looks like perrin is $205 retail and cobb is $250 retail.

I've seen and tuned both and the cobb seems to perform better to me, but that could be isolated cases as they where on two different evos.

 

Interesting. Can you estimate what sort of gains the cobb has over the perrin? I would be interested to see how the cobb performs.

 

Damnit...is this the Apexi Super Catalyzer. Mine just came in today??? Considering my car probably only puts down about 300-305whp on your dyno do you think I would notice as much difference?

 

Great data. Thank you for sharing it Bryan.

Another factor here is the exhaust cam gear. If it was set up aggressively due to the testpipe (e.g. more overlap) and was not tweaked when the cat was installed, then the effect of the additional backpressure of the cat will be more pronounced.