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cat removal 89 740

K

katluke

Member
Joined
Apr 21, 2010
Location
England
Can I remove the cat from a 89 b234 740 and replace with a straight pipe ? I know there is a sensor in the cat but is there a way I can bypass this ? I am hoping to fit a full 3" system and as the cat is not reqd by law (England) I would prefer to remove it. Thanks for any replys.
 
Hi!


While I can understand your motivations, I also know that there is little performance to be gained by the total elimination of the cat / vs. some of the high flow catalysts available. Just so you know that I’m not trying to influence your decision one way or the other, I want you to know that you can sell your old converter on eBay for over $100. Do you have any emissions requirements where you are? It’s much cooler to run a clean engine, then a dirty one. I laugh at people (ricers) who think that their cars are so cool, when the back end is just covered in soot from rich and dirty burning. It really is a disgrace to not only the owner, but the entire community of Honda / Volvo / whatever, when one represents themselves badly.


Good Luck!
 
katluke said:
I know there is a sensor in the cat but is there a way I can bypass this ?
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It is an oxygen sensor. Your car will not run (well) without it. It will get 10 miles per gallon.

You could run a straight pipe, but the sensor should be located there in the cat where it gets the hottest to work properly, You could mount the sensor in the downpipe closer to the exhaust manifold, but it would be much simpler (and environmentally conciencious) to get a 3" aftermarket free-flow cat with the port for the O2 sensor. They are not that much, I just got one for $70 USD from Magneflow. Also, I wanted to use a cat that didn't have the sensor port, and the shop wanted $80 to weld the port somewhere else in the pipe, just not worth it.
Also, a bigger perfomance cat will act as a mini-resonator, and help with exhaust gas expansion, improve torque more than a straight pipe, especially if it's located near the downpipe.
 
Aside from weight reduction you will very rarely get any performance gains by removing components from your car. If you want your engine to flow better, start with a bigger downpipe and hi-flow cat.
 
If it has just the single O2, relocate it to pre-cat (have an exhaust shop weld on a new bung) and put a bit of straight pipe on there.

IF it has two O2 sensors for whatever reason, then the one in/after the cat is meant to measure how effeciently the cat is operating and will wig out if you remove it, and also cause problems if you just put that in the normal exhaust stream.

But if it's a single O2 I see no harm in just moving it upstream a little bit.
 
Thanks for the replys,I have been in touch with a company regarding having a full 3" system and sport cat made and they were very helpful so this is were I will go when I am ready to order.
 
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I’m not trying to influence your decision one way or the other, I want you to know that you can sell your old converter on eBay for over $100
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FWIW, I imagine an 1989 cat that came on the car new,as original equipment(if it is) is well beyond being much good, and probably burnt out. Theefore I doubt it's worth 100 bux on ebay. I have yet to get over 27 bux for a Volvo cat at the scrap metal yard.
 
smokeyfan1000 said:
FWIW, I imagine an 1989 cat that came on the car new,as original equipment(if it is) is well beyond being much good, and probably burnt out. Theefore I doubt it's worth 100 bux on ebay. I have yet to get over 27 bux for a Volvo cat at the scrap metal yard.
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You got robbed smokey! I sold 3 cats from my 945's this summer for $120 each.
A cat converter will last for many years in most cases, mine came from 91 & 94 940's and they looked like new inside when I cut the ends off for shipping.

Volvo cat's have a high content of platinum & rhodium. $$$

http://www.sellyourcatsdirect.com/

^^ I sold mine to this place ^^
 
these were old 79-87 240 cats. Mostly burnt out, wouldn't even take 2 of 'em. Sound like you're running across replacement/recently/ newly installed cats. My 1991 240's cat was empty, and all stuff was in the muffler,( till it fell off). Had 99,000 on it when i got the car. Replaced cat arounf 110,,000 IIRC.
 
smokeyfan1000 said:
these were old 79-87 240 cats. Mostly burnt out, wouldn't even take 2 of 'em. Sound like you're running across replacement/recently/ newly installed cats. My 1991 240's cat was empty, and all stuff was i the muffler, till it fell off. Had 99,000 oi when i got the car.
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That means the car was running poorly, dumping fuel perhaps. mine were stock, never replaced. A cat converter rarely goes bad unless the car is not running correctly!
 
Nothing lasts forver on a car. cats need replacing too. All aftermarket ones are only warranteed for 50,000 miles.

Never seen many of them on Volvos make it past 110,000 myself.
 
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