i bought a turbo prelude that has a test pipe and was tuned professionally (by previous owner). if i put a high flow cat on it is it going to throw off the tuning? is the back pressure going to destroy the engine? WILL THE SKY ESPLODE

ive also read that turbo runs too hot and will destroy the cat, is this true?

it has a wideband, im assuming the second o2 sensor is disabled in the ECU for the test pipe so is there even any point in plugging the o2 sensor into a cat?

too much to learn, im trying to piece together a puzzle on how all of this stuff works. any advice is appreciated

 

the wide band is to tell you your air to fuel ratio so that you dont run it to rich or lean. the cat wont be bad, you will get more back pressure, more heat and less power. and yes the sky will explode haha


hope this helps!

 

more heat as in it could overheat the engine? and what kind of affects will the added back pressure on the engine be?

basically, is having a test pipe normal for a boosted honda and cat a bad idea... obviously, test pipe gives you better performance but im really wondering is that the only reason people do it or is having a cat actually bad for the turbo?

also, the wideband is before the cat correct, i know thats the important thing for tuning the air/fuel so its not too rich or too lean or whatever. but isnt there a second o2 sensor in the cat, im assuming it isnt there to adjust the ratio but only to say if the cat is working or not... because if theres a test pipe in the exhaust the second o2 sensor is just unplugged and not doing anything...

 

More than likely the car is OBD1 which case it'll only have 1 O2 sensor.

 

a hi-flow cat will be fine, shouldn't be enough restriction to completely destroy your motor. just keep an eye on your EGT, boost, and wideband gauges. I would personally run the hi-flow cat just because no-cat is begging for trouble from LEO's when it probably doesn't add enough power to make it worth it.

 

running no cat is a little better, but if you have to worry about emissions then just get a high flow cat, or make a friend that will pass you.

Id leave it the way it is with the test pipe.

 

i dont have to do any kind of emissions/inspections on the car. and i have other perks that i dont have to worry too much about law enforcement. i just dont like the idea of not using the cat just for the sake of better performance.

but saying the back pressure is not enough to completely destroy the motor, thats like saying having a dogs jaws around your ankle isnt enough to completely rip off your foot... but its still going to cause damage. the question is will the cat be causing serious/measurable damage to the engine and how much? i cant tell if people are over estimating one way or the other. they make cars out of the factory turbocharged so there has to be some kind of cat on those

 

adding a cat will not hurt your engine in any way. it will just decrease horsepower and help keep the environment cleaner. you most likely will need to have the tune cleaned up as adding/removing any restrictions from the exhaust can change A/F ratios

if it makes you feel better i ran a 2.5" exhaust w/cat for over two years on my stock gsr engine. the sky didnt explode

 

hahaha the sky exploding comment made me laugh!

 

yea the cat isint gona blow it up you just gona lose power, the set up you have now sounds pretty good and like dagle said keep an eye on the wideband and you should be fine.

 

im not exactly understanding how the air/fuel ratio will be effected by the cat. i just learned today while i was reading the chilton in the bathroom that the o2 sensor in the cat does absolutely no adjustment to your air fuel ratio. so the wideband is before the cat, and it measures the o2 in the exhaust and sends lean/rich to ecu and it adjusts or whatever it does magically, its reading the exhaust BEFORE it gets to the cat. i guess i dont know very much about this stuff but im not grasping how a cat or muffler or any other part of the exhaust past the wideband is going to change the air/fuel ratio inside of your engine

 

A test pipe would be a lot better because there will be no restriction and it would be all free flowing air. i think the car would perform much better with it.

 

your right it has nothing to do with the o2 in the exhaust, the hi-flow is just better for the set up for power and economical reasons. its just important to watch your wideband.

 

you are correct, the secodary o2 has nothing to do with a/f ratio. it simply monitors that the cat is working effeciently. since you have converted to obd1, the ecu doesnt even look for it.

now the cat can still affect a/f ratio. adding a restriction to your exhaust means you are flowing less exhaust, meaning you should run more rich under the same tune. get the tune cleaned up if you add a cat, but if i were you i would leave it like it is. especially since you have no emissions restrictions

 

I am looking at a 95 civic with a boosted d16z6. It has no exhaust and is tuned with e85. If I add an exhaust system will it mess it up? Will I still use e85? I have to be able to pass inspection so I need to make sure that it will work if I buy it.

Any advice is appreciated.

 

If you need to add an exhaust to pass inspection, make sure of any requirements for that exhaust, and if you need to pass emissions, you will need to put a good quality high flow cat on the exhaust.

It would be good to have the tune checked after installing the exhaust, and if it currently has an open downpipe, I would have the tune checked before driving the car at all.

You should be just fine to run E85, and it will make emmisions numbers look great if you do have to pass a sniffer test.

 

this. why would you want a cat? If you need to get it smogged just pay the shop a little extra, it's cheaper than buying cats.

 

Thanks for the advice. I ended up going NA. I bought a 99 civic si, but it has no cat either DOH! I would rather run no cat but emissions will be a problem in North Texas.

 

I have no cat in my lude and the car runs perfect my previous 01 lude had a straight pipe no o2 sensors and no cat and still passed emissions in illinois. Different states different requirements im guessing

 

open downpipe FTW

 

Just leave on the test pipe if you don't have to worry about inspections. I am running one, but I also have a 3" high flow cat I swap out when I need to get it inspected (the car is mostly track driven)

There is a very noticeable loss in mid-high end power with the cat installed.