Cat removal with JSM style dp

[bender]

I got a dp flange from Renz, and my brother welded it up for me JSM style. My question is, Would I be ok to remove the cat while the truck is on jackstands torn apart. I would rather do all this stuff at once verse climbing under there again with the sawzall. My exhaust was welded at every joint, so I have to cut it out. Just wondering if with the high flowing DP, will I be ok without a cat.

 

[It's just a six]

Re: Cat removal with JSM style dp

Depends on how you are going to drive it. Cruise it, race it?

What muffler do you have on the car?

Stock wastegate? Ported?

I say do it all @ once & port the wastegate.

 

[bender]

Re: Cat removal with JSM style dp

Depends on how you are going to drive it. Cruise it, race it?

What muffler do you have on the car?

Stock wastegate? Ported?

I say do it all @ once & port the wastegate.

It is a cruiser, no track time. I am going to put ultimate bins in my g3 and want to be able to try the street bins up to 18-20lbs. I cut the back of the exhaust housing out so it is one big opening and the flange is done the same way. The waste gate is stock, I did take a grinder to the turbo side of the wastegate port to round off the hard leading edge. I wasnt really sure how much material to remove based off the pics I had seen. The wast gate flapper can open considerably more now with the material removed from the DP side of the turbo. The whole reason I did this dp mod was to be able to have good solid boost control, I just dont know if removing the cat will take it all away.

Here is a pic of my exhaust, I did not put it in, so I dont know what brands anything is. The cat looks pretty standard, the muffler is a small diameter straight through style.

pic of modified flange and down pipe

 

[elorejas]

Re: Cat removal with JSM style dp

sorry for budding in but to remove a cat what has to be done since i have heard of people saying if you remove the cat it means bye bye engine

 

[sy538]

Re: Cat removal with JSM style dp

The problem is the wastegate doesn't flow enough. Remove the cat and the wastegate really doesn't flow enough. It will open all the way and the turbo will still make too much boost, maybe way to much like mine would have.

You can get an external wastegate, get a bigger turbo, get a bigger exhaust housing for your stock turbo*, or get a JSM style downpipe.

Some people have been ok with removing the cat. As far as I remember, those guys are at very high elevation.

* This is the route that I took. I got a 10cm exhaust housing to replace the stock 8cm. It's right on the edge of being big enough. Too close for me to recomend to anyone. If I had it to do again, I'd get a 12cm. If I ever come across a great deal on a 12, I'll buy it.

http://www.syty.net/forums/showthread.php?t=58329
http://www.syty.net/forums/showthread.php?t=81915
http://www.syty.net/forums/showthread.php?t=81989

 

[HAMMERHEAD]

Re: Cat removal with JSM style dp

I am running the JSM 3 inch with a 20g,12 cm, ported exhuaust housing,38mm waste gate,3 inch exhaust with a gutted cat and Borla XR 1 muffler. The turbo spools up real quick with the stock converter and I have never had any boost spikes. The boost control is rock solid with this set up and my truck still looks pretty much stock.

 

[JSM]

Re: Cat removal with JSM style dp

If you fully gut the exhaust housing side wastegate flow really is no longer a problem. In testing we did this along with a larger WG puck inside and it started to flow TOO much in the higher boost ranges.

Chances are you will be fine, worse case you will need to do some tuning and tweaking to the chip boost settings to totally dial it in.

Again because I can NOT say this enough, and people tend to ignore this fact. The stock boost control logic inside our ECM is superior to most aftermarket controllers. With that said it was tweaked and tuned by GM for 14.7 PSI of boost on a STOCK truck. Once you change things like bigger exhaust, different muffler, etc etc. naturally the settings just may need changed also. Changine them involves tuning with the chip. This should be common sense but so often gets blamed on a "crappy" stock boost control, when it is nothing more than an owner changing some but NOT everything that controls a system.

Same thing with fuel, or anything else you change there is a whole system to it.

 

[It's just a six]

Re: Cat removal with JSM style dp

Right now I use 12 cm turbine housing w/stock flapper valve.

I did remove the valve so I could enlarge the hole & made nice smooth tansitions (radius) entry to the flapper valve.
I have solid boost control w/the ultimate chip, I just installed a AEM TRU boost controller so I can change the boost level quickly & easily.:tup:

Still trying to figure out TP5 & my Autoprom from Moates.

 

[bender]

Re: Cat removal with JSM style dp

I think I am going to try the 15 lb chip out with the cat still installed and see what the boost profile looks like. If it looks nice and solid, I am going to cut out the cat and go from there. Im doing a lot of "while im in there", and I need to make sure this thing is running right before I add any more variables.