[AwBoostedCR]

I deleted my cats and now i have dp. there is no 02 sensor so i get engine malfunctions, power reduced. so i told terry and he suggested his dp fix. so i bought it and installed and the engine malfunctions keep coming. Any ideas? anything else i can do besides putting my cats back on.

[SfValley335i]

scan the codes to make sure its 02 faults.

[REDSKY]

Originally Posted by AwBoostedCR

I deleted my cats and now i have dp. there is no 02 sensor so i get engine malfunctions, power reduced. so i told terry and he suggested his dp fix. so i bought it and installed and the engine malfunctions keep coming. Any ideas? anything else i can do besides putting my cats back on.

OP (horhey), I think your question is rather ridiculous, the answer is very clear...put your cats back on and stop crying HAHAHA !
RING RING...ENGINE MALFUNCTION REDUCED POWER! LOLOLOL

[scottp999]

Give it some time for the codes to clear themselves. Optimally you would have a BavTec cable and clear the codes immediatley.

[645Nm]

I read your post a few times and could not decide if I should respond or not but I gather from your post that you could be new to the tuning game - if not then excuse my ignorance.

I am not a tuning expert either but am an enthusiast like you and have a lot of personal experience on the issue you are raising.

The answer is simple. Your car (never mind the engine) will not function properly when you remove the catalytic converters, whether it is only the primary or just the secondary cats or both (all 4). I assume you have the catless DPs.

You can buy the best 02 sim currently on the market (I have a few of them including the BMS) but there is no gaurantee that it will work on YOUR car. An 02 sim is not an exact science...when it works it certainly works well.

Look, by decatting your car you have just created endless problems for yourself. A decatted car has less backpressure; breathes better; releases restricted HP;reduces stress on the turbos (remember the primary cats come straight off the two small turbos). I read the e90 posts about the great gains on especially the catless exhaust, some even remove all cats with straight pipes. I have been there and done that. My complete catless 335i ran fantastic dyno and street numbers from December 2007 for almost two years with the RR DPs. I could pull 30-45HP on catless DPs with a tune. And of course the sound is amazing and addictive. When I removed ALL four cats with straight pipes and kept only the stock rear mufflers the power unleashed was incredible even without a tune. I cannot recall losing street drag battles during that time. The fastest and heavily modded 335 on the block taking on some big guns. But shit no one realised that the car had to be checked everyday or after a race - codes cleared 3 times a day - spark plugs changed every 1 000 kilometres - dead lumbda sensors - bad fumes - CELs with the 02 sim in - early morning shakes - all in the name of the pursuit of power - and the fact that the car is no more reliable as a family car to go on long holidays - expect anything and mostly bad to happen while travelling.

You need to clarify what your goal is with your car. If you plan to race/drag and track it often then there is good gains to be made with the DPs and if you know an independant bmw specialist that can support you in your race endevours and check your car if problems arise.

But here's the thing: My other 335 has most of the popular mods except for meth and DPs.
I have the BMW performance exhaust, JB3, FMIC, BMS DCI,Bilstein coilovers, super light forged wheels, race fuel (when needed), forge valves and ALL cats still in place and it pulls VERY strong.
I think I can get very fast times with the JB3 dailed in on map 8 or a custom map with the JB3 gauge - without removing the cats. Fair enough it is not as quick as the catless car but damn fast enough and without any problems to date.

Long story, short: my suggestion is leave the original cats in place. Reconsider all your other tuning options. You can achieve great run times without removing the original cats. But if you must - consider the catted high flow race DPs, which does not require an 02 sim and hopefully/maybe none of the problems I had.

If I can be more helpful in my reply let me know...

[scottp999]

^
|

This is why I went with Hi Flow catted DP's, they don't throw a CEL, are considered EPA ODBII compliant, don't smell, aren't real loud, and allow about twice the airflow as the stock cats.

[cstavaru]

From what I read until now, there are no race-catted downpipes that do not throw O2 codes. Does someone know a company producing catted downpipes which do not throw codes ?