anonymousagain

Looking to replace/upgrade stock Cats on '86 with some hi-flow units and looking for some clarification on differences between 100cpi and 300cpi.

Does 100cpi flow significantly better than 300cpi?

Does 300cpi clean significantly better than 100cpi?

Assuming sound output is similar??

CA car, so emissions matter --> which would lean toward 300cpi units, but is there really a difference?

Any insight greatly appreciated

Ketchmi

In my dyno testing the 300cpi cats lost 7-8 horsepower, the 100cpi lost 1-2 horsepower. On an 86.5' the 100's should pass emissions with no problems at all as long as it is operating in closed loop mode. There was virtually no difference between the factory cats and the 100cpi in local smog testing. Will they do as well cleaning up a dirtier running car? I don't know but we do sell 300cpi as an option for the 16 valve cars, the CIS is not as tightly controlled as the LH.

FlyingDog

Beerfish failed VA emissions with (I think) 100cpi, but his is an open loop only LH Euro S.

anonymousagain

Thanks Dave. In the predicament of considering non-Cats with X, switched to stock for smog test, or just running full-time compliance w/Cats and be green as well without swap hassle. Glad to hear that properly running is the key, not cleansing capability of the Cats.

IcemanG17

Kirt
Did SATA not pass........generally the stock cats work well and last just about forever.....vs the aftermarket cats that don't last long at all.....

anonymousagain

Brian, just considerations for upgrade to exhaust for better flow...assume stockers will pass just fine

Thread searches indicate a significant loss with stock Cats, so I've always thought to go X sans Cats for biggest hp gain. Figured to just swap back to the stock system for the check, but with hi-flo Cats only ~$300, been contemplating X w hi-flo's to just be done with it; technically it's the more greener option too.

928DK

I have an x-over and cats from 928specialists and they have passed emissions twice now.
(also no smog pump)

Anyone know how any cells/cpi the cats from 928specialists are?

Bernhard

Mike Frye

I can't speak to the 100/300 difference. I think there was only one available for my setup through 928 Motorsports (300cpi?).

If you're interested, I was having a heck of a time getting through inspection with the stock cats (including an O2 sensor that I couldn't get to budge). Here is a scan of my emission results before and after the change:

Stock (20yr old cats) and bad O2 sensor:



with 928 Motorsport Crossovers with new O2 sensor:



I'm probably losing 10 hp or more with the cats vs. without, but it's legal .

Ketchmi

Hey Mike...928 Motorsports resells our crossover, you have 100cpi cats. They have a 1 to 2 horsepower loss verified on many dyno runs. Still nice and clean when the engine is operating properly...

Fastest928

We have dyno' our x with both our 300 cpi metal foil cats and open pipes and no difference in power...

Marc

anonymousagain

IIRC, both Motorsports and DEVEK X-pipes showed similar ~25hp hp gains -->

so, is the Cat loss-vs-no loss due to the Cat that's flowing different?
or the X design combined with Cats?
or perhaps a downstream variable difference like muffler(s) to account for the loss-vs-no loss?

Hmmmm...sorta assumed that similar component RandomTech-like hi-flo metal Cats were essentially the same ??

Mike Frye

Sorry, you told me that once before. I gotta write this stuff down.

Bottom line: if your car is tuned well, the cats almost don't have to do anything, so open up the pipes and let the HP roll!