Removal of catalytic converter

[akhuntr]

I have a 89 carbed Festy. Recently Anchorage Ak has terminated all emission requirements. My car is consistantly getting 40.8 mpg with a stock B3. I would like to put a header, larger diamenter exhasut pipes, better muffler, and remove the catalytic converter in an effort to pick up a few more mpg's.

My question is, will removing the cat negativly effect the car preformance? Also, does anyone have a line on headers for the little B3s other than FMS. I have called them several times over the past couple of months and even sent emails with no response. I have not been able to find another source anywhere. Any help would be greatly appreciated.

[TominMO]

The cat is a significant restrictor, so yes, removing it will help power and gas mileage. I don't necessarily think it's a good idea to go larger on the pipes tho; you will probably lose torque, and negate some or all of the gain you got by removing the cat.

[Movin]

It might sound a little better but figuring out how to make the o2 work as good
or better might be challenging.

[BigElCat]

The only O2 sensor goes in the e manifold, or one of the primary header tubes.

Dr Dan and I are on this right now!

I'm designing a cat back exhaust system that will work with a cheap high flow muffler in place of the cat, or the stock cat.

Headers are non-existent at this time. One could chop up a motorcycle header, and develop a tri-Y design.

[hotfordcat]

Matt Dickmeyer has a header for the B3. I removed the cat on my 91GL with B6 swap and had no problems. I wish Matt was still on here, but the haters ran him off because he was building a B3. He was developing some really nice pieces for the B3 also.

[loknlode]

ditto

[BigElCat]

I'm B3 till it fries!

Haters can see me in the Arena.

[windy1]

haters

haters are everywhere. so are lovers. just do what u,do best,and ignore the robots. dickmeyers a legend in his own time. life goes on with or without you.

[windy1]

cat

id leave cat alone,or get a new one. my guess,the designers of festy, kept the cat for usable back pressure. if u want more power,try a bigger engine.the b3 needs back pressure,for tork

[BigElCat]

Back pressure is bad. Small diameter tubes for exhaust velocity and cylinder scavenging create torque.

[BigElCat]

Allow me to clarify.

A small diameter primary tube, as compared to a larger diameter primary tube, can maintain exhaust velocity better in some cases.

A cylinder on a 4 stroke motor can not be scavenged by the primary exhaust tube. A properly designed tri-Y header can allow one cylinder to scavenge the primary tube of another cylinder.

[akhuntr]

Thanks

Thanks for all the input and advice.

I thought I read somewhere a few years ago that you would not gain much if anything by going to an exhaust pipe larger than the 2 inch area. My concerns were that removing the cat may casue a problem with the O2 sensor or other areas that would casue the mpgs to go down. My primary goal with this car is to get as many mpg as I can. I have my eye on a 91 for a B6T swap later down the road. Once again, thanks for all your help on this and any future questions.

[windy1]

right

you,d have to have a header made 2 your specs. i agree,back pressure is bad,if its excessive. its a fine line,knowing how much bp. to eliminate. im telling u,the b3,is a small engine,and designers designed it to work,the way it is. i suppose u,keep trying different mods[if thats your goal] till u,get desired effect. just adding a mini turbo,helps a lot. i keeo exhaust exit pipe 1 i/2 in. i tried 1 1/4in,and got more tork. but stuck with 1 1/2in

[blkfordsedan]

If MPG is your primary goal, stick with the stock exhaust manifold and exhaust system. Replace the cat with a piece of straight pipe of same diameter and your golden. Headers and larger exhaust may improve power, but will not improve mpg significantly (probably even reduce it). Even if it would gain another 1-2 MPG, it would take a long time to pay for the cost incurred.

[DrMaxwellEdison]

id leave cat alone,or get a new one. my guess,the designers of festy, kept the cat for usable back pressure. if u want more power,try a bigger engine.the b3 needs back pressure,for tork

the designers used the cat only because it was legally required by the EPA. vehicles ran well for years without them, I don't see the point in having what I removed on my cars...