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Topic: de-CAT or not de-CAT? (Read 1052 times) |
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OHC
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de-CAT or not de-CAT?
« on: Sep 29th, 2004, 6:43am » |
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Hello!
I need your advise! My Scorp 95 2.0 DOHC 16V has its catalyst on its way out!  The replacement is too expensive for me! I would rather de-cat my car, because MOT is not a problem here in Russia, but, naturally, my car has a downstream HOS! As far as I know it doesn’t take much part in fuelling but if anything wrong it generates DTC! So can I remove the catalyst without affecting performance and MPG?
Best regards
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Snoopy
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Very old.BAD tempered and missing friends.
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Re: de-CAT or not de-CAT?
« Reply #1 on: Sep 29th, 2004, 7:28am » |
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I think you will find that the car will run ok without the cat..... The first sensor on the system is the one that is used really so go ahead and try it.. I know some of the guys who run on LPG have had the cats taken off as the emmissions are better.....and do not have problems but I am sure others will advise you better than me.
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Thunderchild
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My other car's an Aprilia
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Re: de-CAT or not de-CAT?
« Reply #2 on: Sep 29th, 2004, 1:33pm » |
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Got to agree with Snoopy on this one. No problem when the cats are removed, just a bit more power. I've converted to LPG as well and the emissions are down but the car passed MOT before the conversion was done. Good lamda sensors take care of the fueling and thus the emissions (at least that was my experience)
Thunderchild
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OHC
Junior Member
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Re: de-CAT or not de-CAT?
« Reply #3 on: Sep 29th, 2004, 2:13pm » |
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Hallo!
Thanks for replies! But what about downstream HOS! Will it generate a DTC and go to sleep without invoking LOS? Or will PCM be constantly trying to 'shock' it making mi[ture reach or lean, eating fuel like hell?
Best regards
OHC
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phuturephantasy
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Re: de-CAT or not de-CAT?
« Reply #4 on: Sep 29th, 2004, 6:59pm » |
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As I understand it the downstream sensor has No control over fuelling and does NOT affect the running in any way.
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OHC
Junior Member
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Re: de-CAT or not de-CAT?
« Reply #5 on: Sep 30th, 2004, 6:01am » |
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I wonder what HOS12 is for? Only to control if the cat is working? If it fails does anythig happen besides a DTC?
Best regards
OHC
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SaveTheNight
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I can resist anything ...except temptation !!
 
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Re: de-CAT or not de-CAT?
« Reply #6 on: Sep 30th, 2004, 7:46am » |
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as the guys have already said ..the pre-cat sensor affects/changes the fuelling .. the post cat sensor merely reports to the eec and does not affect fuelling at all .. when the de-cat pipes are made then you should have the original sensor bosses welded back into the same place on the pipes and the post cat sensors refitted ..all will be ok .. there will be a small power increase and the fuel consumption will also improve.. regards ...STN
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ChrisB
Junior Member
Without a scorp !
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Re: de-CAT or not de-CAT?
« Reply #7 on: Jan 12th, 2006, 2:53pm » |
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Hi , this is dragging a post from the past up 
But I was wondering about your comment STN about
Quote:| and the fuel consumption will also improve |
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My understanding of exhaust systems were that the more you un-restricted them the more fuel the engine will require due to the fact it can now breath much better
Yep you get more power but to make this extra power available you can only do this by adding more fuel. All to do with back preasures etc
I am remembering back to my younger days of big bore exhausts on my escort  , yep it would now sound faster but actually made the poor thing go a little slower due to it now running too lean. It wasnt until I spoke to a chap who knew about engines etc and he said had I increased the jet size in the carb............
I fitted larger jets to the carb so the engine was now being fuelled correctly rather than the lean mix it was getting with the big bore exhaust. This not only improved the performance but now that I'd up'd the jet size to get the mixture correct she was now using more fuel
Of course with modern scorpio engines all the mixture side of things is done via the sensor in the down pipes but I would have thought the principle would have remained the same, i.e. Increasing the exhaust flow ( by say de-cat-ing ) would mean a increase in fuel used as the sensors would see a leaner output from the engine
Hence my queery about "better fuel consumption"
If anyone else has ideas regarding this, I would be interested as I might have been wrong for all these years  but from my early experainces and chat to a senior mech from years ago seems to make me think that it would have an oppersite effect and increase fuel consumption slightly
Cheers
ChrisB
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scorpio_man
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Ford Kuga awd
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Re: de-CAT or not de-CAT?
« Reply #8 on: Jan 12th, 2006, 3:24pm » |
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hi there
i know what you are saying with regards to back pressure etc, but from my own experience, fuel consumption will go down very slightly. around town i stay @ 19-22mpg and on the m/way, i can get up to 30mpg. this is all on lpg (38p/p/l).
power does increase by a good wee bit as an extra
i should add, my mpg on the m/way before was 27mpg.
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ChrisB
Junior Member
Without a scorp !
Posts: 58
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Re: de-CAT or not de-CAT?
« Reply #10 on: Jan 12th, 2006, 4:07pm » |
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Interesting but it does look like the proof is in the pudding
Quote from invernessguy
Quote:ohc, I have not yet replaced the cat... and after a couple of weeks running, i dont really recommend removing it, fuel economy is WORSE, and the car is a bit noisier... Yes, the car has more power, it feels more responsive, but as a trade off, i would prefer to have my economy back, and nice and quiet again
hope this helps,
donnie |
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Of course the poor fuel enconomy could be because it sounds throater and makes you drive it harder or it could be that the ECU is supplying the engine with more fuel now that it can breath easier
The plot thickens 
So it looks like my thought is correct, that mpg does get worse........well until anyone can say otherwise.
I must admit that the theory states it should .
ChrisB
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ChrisB
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Re: de-CAT or not de-CAT?
« Reply #11 on: Jan 12th, 2006, 4:10pm » |
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on Jan 12th, 2006, 3:24pm, scorpio_man wrote:hi there
i know what you are saying with regards to back pressure etc, but from my own experience, fuel consumption will go down very slightly. around town i stay @ 19-22mpg and on the m/way, i can get up to 30mpg. this is all on lpg (38p/p/l).
power does increase by a good wee bit as an extra
i should add, my mpg on the m/way before was 27mpg. |
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So from this your saying that it does improve , so on one side we have people saying it gets worse and on the other it gets slightly better
As before the plot thickens
ChrisB
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Octavian_P
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Re: de-CAT or not de-CAT?
« Reply #12 on: Jan 12th, 2006, 4:55pm » |
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OK i say the folowing
If the engine can breath easier, has more power. Power is achieved by more gas, which is needed when more air is inserted into the cylinders. So if you don't throttle like a maniac, then you don't use the extra brake horse power so you don't burn so much fuel. Now to continue if you drive the car in the same maner that you drive it before (same speed and similar acceleration) it will consume less because the engine doesn't work more to get the gases out.
So eaven if the mpg does go down, how down could it go, anyway in the spring when it will be warmer outside i'll try to get my cat out.
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2.0 16V Ultima|2.3 16V Ghia|2.9 24V Cosworth Ghia
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ChrisB
Junior Member
Without a scorp !
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Re: de-CAT or not de-CAT?
« Reply #13 on: Jan 13th, 2006, 8:54am » |
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I can see what your saying but regardless of throttle position the engine is now getting a better air flow and so recieving more oxygen, more oxygen equates to more fuel required to keep the burn correct.
AKA worse MPG
The debate rages on 
ChrisB
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Octavian_P
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Re: de-CAT or not de-CAT?
« Reply #14 on: Jan 13th, 2006, 9:01am » |
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Hihihihihi....this will never end
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2.0 16V Ultima|2.3 16V Ghia|2.9 24V Cosworth Ghia
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OHC
Junior Member
I love YaBB 1G - SP1!
Posts: 97
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Re: de-CAT or not de-CAT?
« Reply #15 on: Jan 13th, 2006, 9:13am » |
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Hello!
At last I dismantled the exhaust! It turned out my car had no cat for a long while. I bought the car without cat! I didn't even notice it! Noise was OK! No DTC! as for bad MPG some electrics are playing tricks, because earlier I saw better figures!  Time to get it sorted!
Best regards,
OHC
P.S. My car is 1995 2.0 16V - it may have forgiving earlier version of OBD II software.
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ChrisB
Junior Member
Without a scorp !
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Re: de-CAT or not de-CAT?
« Reply #16 on: Jan 13th, 2006, 1:47pm » |
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But someone must have the definitive answer that can be backed up somewhere
ChrisB
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scorpio_man
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Ford Kuga awd
Posts: 5654
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Re: de-CAT or not de-CAT?
« Reply #17 on: Jan 13th, 2006, 2:49pm » |
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hi there
i've just noticed from donnie's reply, that he removed the the cat (better flow), but never did anything to the intake side of things. i, on the other hand, cleaned the MAF, the throttle body and fittted an induction air filter kit.
another point is my car is an auto. maybe this mod suits the auto bettter
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david_molloy
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Re: de-CAT or not de-CAT?
« Reply #18 on: Jan 13th, 2006, 7:05pm » |
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Hello scorpio man
what induction air filter kit did you fit?
K&N ??
thinking of K&N for 24V
assume better air flow compensated for by CPU
just theory but seems reasonable
david
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i've got a s/steel heat shield for it as well and use extractor fan ducting to direct cold air to it.