Daily Driver2k2

My pre cats are clogged and last saturday took the front pre cat off the exhaust manifold. Was a easy process, took about 1 hour without removal of the stock y-pipe. The precat was clogged terribly, the honeycomb pattern was filled and a huge chunk of it broke off the honeycomb fillment, which i am suspecting (1) it either disentigrated or (2) it broke off and is stuck at the main cat. Because of inclement weather i wasn't abale to get to the second precat by the firewall which will need removal of the stock y-pipe. Total time only took 2 hours. Notice a improvement right away, regained some flow as i put my hand next to the tail pipe. Before i was getting a weak flow with a near silent tone, now you can actually feel the exhaust coming out with a mellow tone. MPG went from 16.2 -20.0. Also redline went from a brickwall 4k rpm to 5200 rpm. Almost there , but not quite....

Tomorrow i will pull the second precat out . One thing i notice the car pull extremely hard to 5200, then chokes.
So i think the removal of the precats will definitely help in overall performance when totally removed. Also engine sounds beefy...

bgates1654

I would have just gotten headers 2 birds with one stone!

sloppymax

iTrader: (8)

mine was never clogged but i developed a pretty large leak right before the precat and it showed a pretty decent loss on the dyno. after the headers went on, it felt much better as all the precats were removed as opposed to just one with the cattman y pipe. if it was clogged then you should definetely notice some power difference and increase in mpg if you can restrain from feeling the difference all the time. i would definetely check the main cat for damage from the parts of the precats.

Daily Driver2k2

Yeah i will be under there tomorrow. I want to do headers, but i am going to lay low now , as my money has to go to more important things at this moment. I was amazed how huge the honeycomb fillmet is, it really is a huge restrictor in exhaust flow. Amazing how the VQ3.5 can produce so much power and flow so well with these restrictive road blocks in the way. I definitely think the mid to top end power should increase dramatically, although the low end response is very responsive then stock as i took it out for a little WOT romp. Although i can't push it to hard because fear of blowing a head gasket or worse, so much pressure with a clogged cat. Seen it happen to my friends honda prelude....pushed it to hard with a clogged cat then boom!

dirtydirk

Daily Driver, I spoke to Dallas at Warpspeed after reading your post and he said that the precats are made of metallic substrate. I was thinking of punching the radiator side precat but he said since it is metallic substrate it may not be worth it. Are you sure it's honeycomb?

BlackBIRDVQ

iTrader: (15)

My main cat did that at around 50K miles, and my precat did the same bout 70K miles. It was deff honeycomb inside as I punched the precat out and had it like that for a long time. Watch out for a check engine light now- for catalyst efficiency below threshold. It will take sometime for it to detect it and throw a check engine lite. U will need a 02 simulator to take care of the light.

mingo

iTrader: (4)

do you know where i may be able to get an 02 simulator black bird?

Daily Driver2k2

But you had no problems with driving like that for a while? Also did you notice gains in the low to mid, or mid to high when you took out the pre-cats? Also where could i find a 02 sensor simulator?

BlackBIRDVQ

iTrader: (15)

www.o2simulator.com. I noticed some gains from removing the cats, as they where melted and restricting the exhaust flow. I have no cats on my car, havent had any for the last year or so, no check engine lights for me. For 01-up you need the dual output version of the simulator.

Daily Driver2k2

Thanks....for your response...also thanks for the link too. Nice max ... love those wheels , your car is very stealth looking.