Decay

I've been having some interesting boost issues lately, such as basically not building any boost (< 2psi), to making full boost the next time I WOT, then back to nothing. A few have mentioned that my pre- or main cats may be clogged, but I have a DP so the pre- shouldn't be a problem. Anyway, I read about some members who have hallowed out their stock cat and removed the catalyst...is this safe/not the same as slapping on a MP? My car is damn near stock - DP and catback, no ECU or ported WG or anything - would I run into boost spike issues or lean out badly by hallowing out my cat? And sometimes after I boost, the car makes a strong resonating/vibrating sound from underneath, like the car is "extra muffled" or something . I dunno, I guess my only other option would be to get a new main cat? TIA.

paw140

I think you have issues with your turbo control system, not a clogged cat. You may have a bad check valve, or a popped off vacuum hose.

Cihuuy

how many milleage is the stock cat? did you gutt out the cat? there is another thread about this, click on it...

but about the boost, i assume you have a loose or poped vaccum hose somewhere... Whats your boost pattern?

lastly search more on the 3 mod rule!! Hope that helps...

Street King

My set up is stock ECU, Stock intake(K&N drop in). I have Pettit DP, Greddy Catback, and a gutted mid pipe, with a profec-b. I hit a rock solid 10-8-10. No creep no spikes. I don't think a midpipe is the same aa a gutted cat. The gutted cat still has the enlarging and the closing end on it to allow for the cat. It also has a metel hollow bar tube running right in the middle of it to let teh air inside the cat from the air pump. You can not remove this cause it's formed with the cat and I'am sure this creates a bad flow pattern but anything is better than a clogged main cat. So far guttin the main cat has worked out well.

Decay

I would agree with you as of 2 nights ago . Current boost is about 10-8-8 (maybe a little lower at transition, can't exactly tell). I has the manifold off last week and all hoses are/were attached. I did not, however, examine all of the check valves or TPA/WG soli's, so they could also be a source of the current boost issue.

As far as my original post, that happened way back in the beginning of June. I was at the track, and my first run the car took a ****. I could tell once I shifted into the 2nd that the car wasn't moving at all, and I was making 1-2psi. I crossed the line 18 sec later, downshifted to third, eased into the throttle and it built boost fine. My next run the car made a perfect pattern and I ran a really nice time. On my third and last run, the car behaved just as it did that first run...held 2psi just fine. On the ride home the car was all back to normal

And yes yes, I know about the 3 mod rule. I like my car mostly stock (for now) and that is why I am wondering if I will be OK with hollowing the cat for the time being. I am not ready to buy and ECU that would allow me to safely run a midpipe. However, if hollowing the stock cat is unsafe for boost or AFR reasons, I will not do it. Thanks, again.

paw140

It is my opinion that running a gutted cat or a midpipe is not safe, especially on a stock ECU and no boost control. Others will tell you that you will be ok, but I've seen too many blown engines from people running similar setups to agree.

Decay

That's all I needed to hear