I recently took the cats out of my car and replaced with Kline catless pipes. The car sounds better however in traffic and slow speeds I can smell the exhaust so badly that I can't drive with the windows open. I called my tuner as thought my map might be running too rich. He said the map is perfect all catless cars stink. The tuner is known for being one of the best in the UK but is this really the case?

Also since he changed the cats every time I go over a speed bump or cobbled roads there is a very loud constant rattle which was not there before, it is definitely not the heat shields. I can also now hear a loud clunk when I am putting the car in reverse or drive(tiptronic) Any ideas on what this could be?

Lastly not sure if related to the above, however when I sometimes floor it, the car hesitates in between gears as if the gearbox is struggling. However I am only running around 560hp?

Last month I changed the turbo actuators, sparks and coils after they failed after a very short time. I'm getting to a point where I want to change for a warrantied 991 turbo s for peace of mind but have spent £15k mods in the last year Any info much appreciated.

 

Sorry to hear about these issues Alan. Did you have 200 cats before or 100? If you had the 200's then 100cel HJS may be the sweet spot. Tips lare under a little more load and I don't so it smells more. Are you running at Cobb access port by chance? I'd be glad to take a look at logs. Sounds like you've been through some stuff with this car. The thumping does not make any sense. Reach out if you like and I would gladly see if I can help in any way.

 

Hi Sambo, I had 100 HJS Cats before. I'm afraid the tune isn't COBB. If I am too keep the car I will probably put the cats back on.

 

Yeah it's more stinky on a tip unfortunately.

 

Catless will always stink of exhaust fumes and toxic at that.. Did you not expect that when going catless? They convert toxic gases to less pollutants to safer levels.

If you race or trying to shave time by maximizing hp, then catless. As for the street not worth it

 

My car is cat-less (Tubi),.. and has been since it left the selling dealer new,.. and it doesn't smell at all. Not even when I start the car from cold and back out of the garage with the windows down.

My last car did a little bit (not a Porsche).

It's all in the tune. My car had stock tune when I got it (with the catless exhaust),.. then I was on a Cobb Stage 2 OTS tune last Fall,.. and now it's on a custom tune from Dzenno with bigger injectors, IC's, a methanol system etc, and it hasn't smelled with any of those tunes.

If you get that eye-watering stink,.. that's simply because it's running WAY too rich. Cat's will go a long way to mask the problem (by re-buring the fuel),.. at least they will after they warm up,... but realistically there shouldn't be that much unburnt fuel in the exhaust to start with.

Both O2 sensors and MAF's get old and tired. The resolution on a MAF get's slow by 60,000 miles.

O2's have a lifespan as well, and gain in error as they age. High power outputs, rich mixtures, leaded race gas, etc will all shorten their life even further.

 

^^ Interesting. Maybe it's also depends on the exhaust. I remember my catless supra 20 years ago, it was bad.

Do you have a tune ?

 

Hi Alan,

Any catless exhaust will have a more accentuated smell. The difference between some smell and unbearable smell is usually the remap or a faulty part on the car. I have driven endless decat TT s, never felt like it s too much. Please email me with more details, maybe we can see whats going on - Felix@kline-innovation.com

 

I doubt it's the tune. It's just the realities of being catless. With only 560hp there is no need to be catless. Even with higher hp there are great free flowing cats available. With a good 200 cell cat I bet you can't tell the difference in power.

 

I'm running a catless kline with cobb stage 2 and don't smell a thing.

 

Same here.

Got the car with a Tubi catless and stock tune. No smell.

Put a stage 2 OTS Cobb map on it,.. still no smell.

Then 1,000cc injectors, inter-coolers, DO88's, colder plugs, new coils and a Cobb Stage 3 OTS map,... = no smell.

Then Aquamist methanol system, Dzenno PTF tune (He guesses low 620 ish at the wheels based on the MAF numbers). Still no smell.


Should be noted that with any tune,.. the areas of the map that deal with idle and light throttle aren't usually touched,... so a stage 3 tune and a stock tune should smell about the same.

Poor engine running can mess things up.

Tired O2's, old MAF's,... cracked ignition coils,.. bad plugs, or an exhaust that's too big can all make an engine run too rich at idle and have a smell.

 

Two of the four concerns (1st and 3rd paragraph) point to the tune. I'd say get a second opinion on the tune.

 

Could it be a boost leak?

If air that has already gone past the MAF's is then leaking out somewhere (like near the throttle),.. then you'd have over-fueling.

Not sure the mods to the car. I'm guessing it is more than just exhaust, tune and clutch? Does he perhaps have a GT3 throttle and 83mm IPD Plenum that's prone to leaking?

 

If you go catless you dont need the cold start procedure, if you still have it its the reason for the smell on startup, retune will take care or it ...

 

Guys...for those that are saying you don't have any smell after going catless, it really is not the case. Your tolerance to smells may be much higher, that's all.
I agree with a lot of what is being said though - if you are not running high hp (500awhp+), there is probably no reason to go catless. Yes, you will make more power, but potentially loose a little on the bottom. Catless WILL make more power if tuned accordingly, but you will have to deal with louder sounds, a bit of smell and quicker acceleration...this last one is a pain in the butt and the nonsense of burning tires more often can get on someone's nerves very quickly (this last part is sarcasm).