So I finally decided it was time for more mods and bought some direct fit 200 cell high flow cats , installed right before a drag racing event.
results : inconclusive

noise : way up at WOT
power: appears to be down compared to stock , trap speed was down compared to runs with stock cats. Butt feeling also telling me car is down on power

Adjusted for the extra flow in the tune with not much improvement
Now I have not replaced the midsection yet and its all stock, but dont think leaving it stock is making things slower compared to stock can it?
I did a temperature test with the infrared thermometer and test shows 100 degree difference between the front and the back. Front is hotter, which tells me by all internet searches that catalytics are bad and restrictive, but Im not sure if this test applies to high flow cats? Can you guys with high flow cats verify this is normal please?

 

How did you get CA certified 200 cell cats in San Diego. I'm replacing mine this week and could not find any after market cats for my 5.0L car anywhere.

 

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You cant get legal aftermarket ones

 

Thanks, that's what I thought. I got tired of getting CEL warnings about once per month referring to my CATS as the problem, so I decided to bite the bullet (and it's a very big bullet), and purchase new ones from the dealer.

 

Isn't oem warranty for the cats like 100k mi and 8 years?

 

Yes, but I have about 150,000 miles and the car is over 8 years old.

 

Cats out of a late model Mustang will weld right in. Mine acted similar, loud and slow with 200 cell cats. Mostly too loud. Picked up a set of take off's form a 2010 or so and welded them in place. Flow well enough and the noise level dropped back to realistic.

 

This is a good thread and important subject as many will be in this position where decats or 200 cell you'd think be the way for more power vs staying with oem.

 

That is very strange, I lost no power with mine. A forced induction motor is an air pump, open the front end, open up the back end, adjust VE, etc. in the map and you should have much more power with increased flow and air volume.

 

I agree . The only way I would loose power from the cats is if they are more restricted . So I'm trying to see if it's in the tune or the cats

 

I put free flowing mufflers on my XK and lost a lot of power, especially down low. I couldn't wait to remove them (reverting to stock) and ended throwing them in the trash...

 

There is a difference between a forced induction motor and a NA one, you may have lost some of the necessary back pressure or unbalanced the VE.

 

I'd say unbalanced the VE

13.72 is the best time i have run in an n/a xk which has 100cell cats and tune to suit

also in terms of the xkr by memory cambo ran 13.18 in stock form then 12.8X with 400 cells / x pipe and adjusted tune allowing for more back pressure

 

What is "VE"?

 

Volumetric Efficiency...

VE maps are the curse of modern OBDii processors. The original electronic fuel injection monitored the engine rpm, throttle setting, manifold pressure (MAP) and a temperature or two and determined what fuel dose to apply to the engine based on Speed / Density (S/D) maps which were coded for stock engine component air flow. Throw in a set of heads or different cam which lowered the MAP and the engine had problems due to trying to run richer for the lower MAP. Later EFI engines used mass air meters which could care less what mechanical components were in the engine (within limits) and coded based on air flow. They are what really uncorked performance limits in the early '90's. OBDii is a much more stringent program due to government meddling and like S/D systems it will code or just not perform if the actual performance doesn't match the 'assumed' performance. To me it really was a step backwards for the home grown builder.

 

8/80K

 

This is elementary, but did you do a "hard reset" after installation?
Check engine light on? If not, it is some indication that the cats are prperly working correct fuel ratio mixture to the politically correct level.

 

Not just a reset but ecu reprogramming as well to account for lower back pressure...
Now Check engine light occasionally comes on for cats inefficiency , bu this is expected for high flow cats.
Now can anyone with high flow please confirm if the temperature test is still valid fo high flows cats or is it supposed to be reversed as in my case where inlet is 100 degrees higher than outlet?