would you gain or lose performance? this has prolly already been discussed on here and if so sorry for bringin it up again. anybody felt any gains like 12 hp?
test pipes on na??
- Thread starter big idealist
- Start date
maybe going to a test pipe from a completely plugged up cat. It's an easy upgrade, I made my own from an old cat. Cut the cat. from between the flanges, and welded a piece of 3" in. Cost a whole $20.
AJ'S 88NA said:
It certainly did for me.
My "Test pipe" was constructed by taking it off, turning it sideways, and letting the rotten chunks fall out. Bolt back in and VIOLA!!
How would running a test pipe cause the ECU to start adding any significant amount of more fuel to the mix?
Not as far as I know. Here I was expecting a good explanation as to why people keep saying that too. 
It may *smell* richer since the cat isn't helping to break down excess hydrocarbons, but I can't think of any reason why it would actually cause the mixture to change.
It may *smell* richer since the cat isn't helping to break down excess hydrocarbons, but I can't think of any reason why it would actually cause the mixture to change.
I guess you gave the best explanation. Maybe if you had a cat that was fairly pluged up, is why people feel that it makes a difference?CRE said:Not as far as I know. Here I was expecting a good explanation as to why people keep saying that too.
It may *smell* richer since the cat isn't helping to break down excess hydrocarbons, but I can't think of any reason why it would actually cause the mixture to change.
Well, even a good high flow cat will create some restriction... I'm not debating that a test pipe may or may not free up some power, just pointing out that it's unlikely that it'll change your fuel mixture (I've seen that posted a lot lately).
On a Cali. spec car it could effect the fuel mixture as there is another O2 sensor between the two cats, but the rest of them I don't see it happening.
On a Cali. spec car it could effect the fuel mixture as there is another O2 sensor between the two cats, but the rest of them I don't see it happening.
Hmm... Would a larger diameter exhaust cause it to run richer? I dunno it certainly seemed to me like it was running a bit richer afterwards... Of course the thing idles like crap most of the time too...
I dunno...
I dunno...
Unless you added an exhaust leak, you shouldn't be running any richer... at least not for any reason I can think of. If someone knows why more volume of the same gas (with the same levels) would cause your O2 sensor to think you're running lean I'd like to know.
The idle could be effected since your exhaust gas is cooling sooner and may be cooling too much while you're in the lower RPM range for the system to effectively clear itself via inertia. If this is the case, at low RPM you may be running richer when in open loop if for no other reason then the fact that less exhaust gas is exiting the cylinder so less oxygen than expected enters on the intake stroke. It would take a fairly big jump in exhaust size to do that much damage to the exhaust flow, probably 3" or bigger for you to really notice it. Larger pipe, more room for the gas to cool, cooler gas is denser and at a point has to be pushed out by the engine. Besides, in that situation you're not running any richer (same fuel map as before), you've hurt your low end efficiency and you're actually whitnessing it.
There's actually more reasoning for the stock sizing than just sound.
How did you determine you're running richer?
The idle could be effected since your exhaust gas is cooling sooner and may be cooling too much while you're in the lower RPM range for the system to effectively clear itself via inertia. If this is the case, at low RPM you may be running richer when in open loop if for no other reason then the fact that less exhaust gas is exiting the cylinder so less oxygen than expected enters on the intake stroke. It would take a fairly big jump in exhaust size to do that much damage to the exhaust flow, probably 3" or bigger for you to really notice it. Larger pipe, more room for the gas to cool, cooler gas is denser and at a point has to be pushed out by the engine. Besides, in that situation you're not running any richer (same fuel map as before), you've hurt your low end efficiency and you're actually whitnessing it.
There's actually more reasoning for the stock sizing than just sound.
How did you determine you're running richer?
im running a test pipe and i feel no difference in running rich or anything like that. I do shoot some bad a$$ fireballs though!!!:evil2:
on an na? i shot flames before... with 2.5 inch custom cat back... with stock filter on car... couldnt with my cold air... and it rarely happend. but that was in some high ass rpms like 6,500 or 7,300
yeah on an na i have an safc2 which i just sold(like an idiot) it was awesome id get them at wilol whenever i wanted them. i love it when it does it near soemone they get all scared and shit and freak out like WTF?!?!?!?!
On an n/a there isn't any real noticeable difference in performance. My test-pipe just changed the exhaust note slightly. Let's face it, n/a's are just slow, but I still love them regardless
I had a test pipe on my N/A and didn't notice much of a difference other than the smell and the exhaust getting louder. I took it off not too long ago and put the stock cat back on.
CRE said:
CALI SPEC!? crap....
ok so how can i determine if mine IS or is NOT cali spec'd? because my car is from Washington and i think the previous seller pulled some strings on smog. from what i remember i only have one cat...
and how do you know if a cat is clogged? thanks.
On the Cali specification MKIII's there is another cat before the exhaust bends under the fire wall and heads back toward the rear of the car. There's also a second O2 sensor right before the 2nd cat. The second cat is in the same place as the cat on the other (non-CA) MKIII's.
A clogged cat will usually choke the engine in the higher RPM.
A clogged cat will usually choke the engine in the higher RPM.