Need Advice: Getting Downpipe to replace Pre-Cat

[skullone]

Loganss: have you seen the DIY o2 sensor mod?
http://www.msprotege.com/forum/showthread.php?t=52498

Ive got the parts to make it, but I havent done so yet. People have had good luck with that.

[marciobusi]

Well.. I think I will have a project for the weekend... Gut the pre cat. Gtech before and after.....

[beetle_orange]

So will this work on a 2nd gen?

[Project Protoge]

Unless the pre cat is going out, I wouldn't touch it. When I gutted my pre cat it caused more turbulence in the exhaust, a lack of power and the exhaust sounded like it was gargling water. The pressure coming out was not at a constant speed. The shape of the pre cat needs the honeycomb inside to keep the exhaust gas flowing in a straight line instead of becoming turbulent.

[loganss]

Loganss: have you seen the DIY o2 sensor mod?
http://www.msprotege.com/forum/showthread.php?t=52498

Ive got the parts to make it, but I havent done so yet. People have had good luck with that.

Yeah I've seen that thread a few times. I'd just like to get exact numbers for the 2nd gen protege than to just throw in a MIL eliminator that was made to work for another car in mine.

I might be on a totaly wrong page but doesn't each car's engine emitt gases differently. Even if the rear o2 sensor is designed exactly the same for each car the reading will still be different with a precat and without on other non-2nd gen protege cars. The P5, MSP, and any other proteges that don't have our engine should make the readings of the 2nd O2 sensor different .... Right????

If a 2nd gen owner has removed the pre-cat and this DIY Mil/Cel eliminator works then I'll use.

Unless the pre cat is going out, I wouldn't touch it. When I gutted my pre cat it caused more turbulence in the exhaust, a lack of power and the exhaust sounded like it was gargling water. The pressure coming out was not at a constant speed. The shape of the pre cat needs the honeycomb inside to keep the exhaust gas flowing in a straight line instead of becoming turbulent.

When I put the pedal to the floor from a cold start I do hear a gargling sound but once the engine is warmed up or I'm already moving above 25mph or so the sound is not noticable. I thought this might be because I don't have a mandrel bent exaust, or my muffler. I def don't have an exhaust leak.

I'm with project protege if your pre-cat is fine don't mess with it.

AND another thing some people in that thread were saying that a pre-cat removal will have your car running pig rich. I really doubt that is the case. As gro_harlem pointed out in another thread the first O2 sensor is the one that would control fuel managment and the second is basically a check to make sure the pre-cat is present for emissions reasons.

I'm getting ~29-30 mpg consistently for mostly city/some highway and between 34-37mpg highway. Our car are rated as 25 mpg / 32 mpg (city/highway). Running rich my ass.

[loganss]

Yeah I've seen that thread a few times. I'd just like to get exact numbers for the 2nd gen protege than to just throw in a MIL eliminator that was made to work for another car in mine.

I might be on a totaly wrong page but doesn't each car's engine emitt gases differently. Even if the rear o2 sensor is designed exactly the same for each car the reading will still be different with a precat and without on other non-2nd gen protege cars. The P5, MSP, and any other proteges that don't have our engine should make the readings of the 2nd O2 sensor different .... Right????

If a 2nd gen owner has removed the pre-cat and this DIY Mil/Cel eliminator works then I'll use.



When I put the pedal to the floor from a cold start I do hear a gargling sound but once the engine is warmed up or I'm already moving above 25mph or so the sound is not noticable. I thought this might be because I don't have a mandrel bent exaust, or my muffler. I def don't have an exhaust leak.

I'm with project protege if your pre-cat is fine don't mess with it.

AND another thing some people in that thread were saying that a pre-cat removal will have your car running pig rich. I really doubt that is the case. As gro_harlem pointed out in another thread the first O2 sensor is the one that would control fuel managment and the second is basically a check to make sure the pre-cat is present for emissions reasons.

I'm getting ~29-30 mpg consistently for mostly city/some highway and between 34-37mpg highway. Our automatic cars are rated as 25 mpg / 32 mpg (city/highway). Running rich my ass.

[skullone]

I believe the running rich part.
My pre-cat has been failing/failed for 2 years now (with CEL) and I see a bit lower MPG lately, 28-31mpg, used to get 32-37mpg (no ****, 1.5L automatic)
Ill probably be giving my Pro to my dad, and buying myself a new 3 sometime this year, so it can be his problem next

[marciobusi]

... from Iowa to Houston I did consistently 44 mpg with my pro. 60 mph. Thats not the case here though. I dont see how a nice downpipe could interfere with flow. This would go against the benefits of a header, that gave to a sentra 1.6L for example, 7 HP. I am expecting that he inserted the pipe all the way through the cat, connecting it in the manifold exit.....

[Project Protoge]

I thought about doing that exact thing when I first noticed that gutting the cat was a bad idea but then I just decided to make a decent downpipe using a header reducer. I never got around to checking the DIY mil eliminator either but from looking at the diagram it basically changes the input voltage to about what the signal voltage would be if the cat were their and sends it back to the computer. This tricks the computer into thinking emissions are fine. The only way that might make the car run rich is if the computer is worried about the emissions more than the fuel air. Possible but not likely.

[TLR5613]

Where did you find your downpipe? I am in search of a new one for my 99 Protege ES.