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Potential engine damage with De-CAT?

10K views 35 replies 11 participants last post by  Firebladder 
#1 ·
Hi guys! Just replaced the CAT with Danmoto link pipe and I also have a short slip-on (SC Project) while keeping the stock headers. Engine runs fine except weird timing just at idle. Once I twist the throttle, is smooth as silk. Question: I'm worried of potential engine damage long term if I don't use a fuel/air manager like the PCV, although as it is I would rather keep the current setting. Anybody better informed on potential engine damage with this setup? Thanks for well-informed (not guessing) answers.
 
#3 ·
Could you kindly elaborate? The weight savings, louder engine rumble and freer-breathing acceleration makes it a worth modification in my view. Besides, many people do it, including replacing the entire exhaust system, with no drama that I can recall. The only concern is a lean mix down low may create some engine issue, or so I hear. Thanks for your views.
 
#4 · (Edited)
friend of mine did the same on a new bike (not a BMW). Decat, new exhaust, no tune.

5-6 months later its in the shop sounding like a bucket of rusty bolts in the back of a pickup truck.

You're gonna spend a lot on a new zorst, spend the extra and get a tune as well. Its either cry now ($$), laugh later, or laugh now and cry later ($$$$)
 
#8 ·
I just talked to a couple of dealerships about K67 availability, and warranty the other day. BMW approves of having a full system, no flash/tune, as long o2 sensors are used on full exhaust to keep warranty.
 
#16 ·
Seat-of-the-pants tell me there are no flat spots in the RPM band so far. A flat spot is quite noticeable while riding ... I initially feared possible low RPM weakness due to thin mix, which did not happen racing the bike over straights and all sorts of slow and fast curves at speed. I may not be optimizing its potential, but runs great and the real concern is eventual engine damage, if that is the case. I mostly race it on roads not tracks. Of course, the full exhaust is better but it also conveys the same PC and tuning approach, with a setup cost much higher for the full exhaust. I also believe the German-engineered headers are quite competent. But I hear you, and will re-think your suggestion. Thanks!
 
#17 ·
If you're worried about the bike, relax. Many others have gotten rid of the environmental restrictors with no damage occurring to the bike. leave the O2 sensors, leave the wires and valve for initial warm-up and free up the breathing by cutting off the cat. use the DanMoto pipe, it works. the bike will "learn" the new "flo". If that's not enough, send the ECU to Bren, then you'll have a fire-breather! Go for IT!
 
#18 ·
Thanks so much for the encouragement. I have been hoping that was the case. I have already made those mods exactly as you suggest, and ridden the bike with no issues. I sincerely hope you are right. The money would be better spent in overhauling the front forks, with new oil and seals, as that oil is already 7 years old. Once done, measuring SAG and adjusting the suspension for my physical characteristics will ensure optimal front suspension along with complementary rear shock adjustment. That is my immediate next project combined with inverting the rear suspension's eccentric for more relaxed riding posture and better leaning leverage in curves. Thanks again!
 
#22 ·
Sorry, still not working.

It's true that the bike will adapt to a certain extent as long as you keep the O2 sensors. The more you ride it the smoother it will get. The cold engine idle will be lumpy, but you'll notice as soon as the engine gets to 50 degrees C it will smooth out. If you're happy with it, just move on to other things. The BMW is not like the Aprilia, it will be fine.
 
#23 · (Edited)
Sorry, still not working.

That's weird! I have used the image uploader with no success and apparently the link by itself is not working either ... Don't know how to proceed, sorry.

It's true that the bike will adapt to a certain extent as long as you keep the O2 sensors. The more you ride it the smoother it will get. The cold engine idle will be lumpy, but you'll notice as soon as the engine gets to 50 degrees C it will smooth out. If you're happy with it, just move on to other things. The BMW is not like the Aprilia, it will be fine.
Thanks for that. The burble it makes in idle is similar to those highly tuned race cars with plenty of power and racing mods. Once they start accelerating, everything goes smoothly. I know I can squeeze out two or three more rear tire ponies with a PCV and a dyno tune (two runs, one for O2 diagnostics, the other to confirm optimal O2 map settings), but as it is, I'm enjoying it in the meanwhile.





 
#24 ·
i can only see the middle of the 3 pics but looks great... enjoy it.

and yeah def get a tune when you can, or order one from Bren or something if theres no good shops nearby... im gonna take a trip to BKK where theres a really good shop and have my bike done soon when i have the time... im due for a plug check on mine anyway, and probably good to test compression while were in there.

i know some people get tired of the shorty exhaust because of how loud they are... but ive been riding it daily like this for a year and i still smile everytime it starts up... even on long trips (12hrs in 1 day) i never get tired of that noise ;)
 
#25 ·
Thanks! If you are using a mobile device, the images are definitely too large. I also like the deep rumble when it starts, but I could use a db killer when I ride for more than 30 minutes. In fact, I always use ear plugs when I'm riding for longer, which is the usual case. How can a Bren tune work so well when atmospheric conditions are so dissimilar? I need to learn about this, as I am intrigued.
 
#34 ·
Thanks for the feedback. I did exact;y what you suggest with the Google-hosted images to no avail. I could not tell, because in every post of mine the pictures showed up fine each time. Anyway, if there are no further comments in terms of the exhaust mods, I'll keep things as they are without concerns about possible engine damage, and concentrate on the suspension overhaul.
 
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