Unseen7

Good day all,

Last weekend I finally got around to installing my RB dual resonated midpipe. Went fairly well except I snapped one of the studs off the front of the cat when trying to remove it (those nuts are crazy hard to remove!!) Side question: How hard is it to replace/remove the studs on the front of the cat?

Anyhow my first impressions of the de-catted car were as follows:
1. No change to the sound level, even the tone didn't really change.
2. No change to power (based on butt dyno), MAYBE slightly quicker throttle response.
3. I get a CEL P0420 (I expected this).
4. Smells really bad, much worse than I expected and I had a de-catted turbo FC for many years.
5. Engine seems to run hotter.

NOTE: All temperatures will be in Celsius

Now point #5 is the one I'm really interested in. I have a Scan guage 2 so I can monitor coolant temps and immediately after installing the midpipe I noticed the engine runs quite a bit hotter, heats up faster and cools down slower. We had some hotter days (30C) and some cooler days (16-20C) and regardless of the day, it ran hotter than normal for the given conditions. Typically in those conditions the engine gets into the mid to high 90s in slow traffic but as soon as I'm above 70kmh it gets down pretty fast to 82-84, a bit slower if I'm using A/C (the fans are pretty good at keeping it under 98). However now with the cat delete, even on the 20 degree days, it would get up to 98-100, without A/C even at speeds of 50 or 60 kmh, and while crusing above 100kmh it would take much longer to cool down and would only get down to 85 ish. I monitor the temps every time I drive it and the only thing that has changed is the mid pipe, everything else is constant, my route, driving style, driving conditions. Its running hotter in all conditions, slow speed, high speed, high ambient T, low ambient T.

This is the complete opposite from what I expected as I thought removing the giant heat block of the cat would allow heat to escape more easily from the engine. I know I've heard that the rear O2 sensor plays no role in fuel mapping, but maybe removing the cat messes with the leading O2 sensor since its just in front of the cat? I don't know. And it seriously smells like gas, honestly worse than my de-catted turbo FC with a pig-rich tune.

Regardless, I'm honestly pretty disappointed with the cat delete...I never thought I'd say this but I think I'm going to put the cat back on, especially since it looked pretty clean. Any tips on removing/replacing the studs on the front of the cat?

Thanks!

peloponisios

Hello my friend, from my personal experience going decat from a 100cpsi cat, I noticed immediately a rather good gain on my butt dyno, especially mid range, so it sounds weird you felt no difference.
Regarding the heat, the center console heat due to the the cat, was reduced again noticeably. As for engine heat, maybe you pushed it harder now you 've decatted it? I have some cooling mods and the car runs cooler so I can't help you more on that.
Seems to me there are some other issues generating heat?
I smelled the gasoline smell ok it's crude I agree but after it warms up I smell the premix "mix" I use and I kinda like it, I wouldn't say it would smell worse than an FC.
If you could be more specific, mileage, mods if any, condition, usage maybe the other more knowledgeable members can contribute.
Edit: of course the previous cat I had was old and maybe the gains I noticed were due to that also.

Unseen7

Right I should have mentioned other mods (there aren't many)
-Running a sohn with separate reservoir
-Premixing 300:1 in addition to the sohn, however not on this most recent tank of gas.
-BHR globally compliant ignition coils, MSD wires from BHR
Thats it, everything else is stock

Like I said, I wasn't driving it any differently than I normally would. One or two full throttle hard pulls through first and second gear to redline, otherwise cruising as its my DD.

I do agree its weird that I didn't notice any power gain, even with a perfectly unclogged cat there should be some restriction that would be alleviated with a cat-delete.

wcs

iTrader: (2)

The smell is pretty strong, I've had my eye's watering from the fumes coming out the exhaust.

edit - removed because I can't read

Unseen7

Yes that is the exact one, and yes it is still on the car. When I say de-cat I just mean I replaced the entire stock catted midpipe with the RB pipe.
I'm positive I installed the RB mid pipe exactly right. Sorry for the confusion, it was clear in my head when I wrote it.

wcs

iTrader: (2)

Maybe there is something wrong with the the midpipe?
Perhaps the stainless steel in the resonators is jacked?

peloponisios

I was about to ask that but I got hungry and forgot.
But symptoms would be worse I think.
Maybe try resetting the sensors with the 20 pedal stomp if not done already?

Shaozhou Zhang

I know this is a dumb question but did you remove the undertray while you were working on the midpipe?

Unseen7

There is no undertray under the exhaust area of the car, and if you mean the undertray under the front of the engine and radiator, no I most certainly did not remove that.

peloponisios

I think he means those like in the attached pic. Those are aftermarket but you get the idea, oem are somewhat similar.

Unseen7

Well I wouldn’t call those under trays…more like supports or cross braces, but anyways yes I did remove them as I don’t think it possible to replace the mid pipe without removing them.

peloponisios

Yes, my bad. Those are braces. So, how's it going? Same situation?

Unseen7

Haven’t driven it in a few days (weather was nice so I took the bike), but I’ll test it again this weekend and update.