I was just wondering. Down here in Louisiana we have no emissions testing at all. Hell, the only thing they do is look at the odometer and change the sticker, lol. My friend took the cat off his 84' vette. It sounds better, and he says he noticed a slight increase in power. I have a 91' Firebird with the LO3 and the only part not stock on my exhaust is a dynomax muffler. Would taking off the cat make it sound better or give it a very slight boost in power, or would it hurt due to a lack of backpressure? Just wanted some input. Thanks.

 

Took the cat off of my 91 Firebird LO3 and it was mildly louder and there was a definite increase in power. The most noticeable range was low end. I did not have to get into the accelerator as much to maintain speed.

------------------
84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

I did this as well on my 90 Formula with LO3 and it was worth it. Sounds good and runs better. Only problem is SES light comes on for code 32(EGR failure)due to low backpressure.

------------------
Mongoose-NCTGA-1990 Pontiac Formula/305 TBI-700R4 with Edelbrock Performer TBI intake,TES headers,and STB,K&N,MSD-6AL,Holley laser shot coil,Accel Extreme 9000 wires,Jet Stage 2 chip,TCI shift kit with corvette servo,Richmond 3.73 gear with Auburn 3 series posi,no cat,SLP 3" cat back,Eibach sportline springs,Energy Suspension poly throughout,Lakewood LCA and adjustable panhard bar package,SSM subframe connectors,IROC wonder bar,Tokico 5 way adjustable struts and shocks,Autometer electric fuel pressure gauge,Alpine,JL Audio,MB Quart,92 GTA taillights,92 GTA aero wing and hatch,Steve Spohn LCA relocater kit,MacEwen White face gauges,84 T/A cold air induction air cleaner,Grant Formula GT wheel.

 

Mongoose, this happens to almost all LO3's with higher mileage. My brothers 89 LO3 with working cat had a code 32 and so did my Firebird before the cat removal. The EGR valves just take a ****. Replace the EGR and no more codes, period. If lower backpressure caused a code 32 then performance exhausts would'nt be worth mutch then would they and yes I know about positive and negative pressure EGR valves.

------------------
84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

mongoose, i'd like to know where you get your car inspected.

 

I guess that I'm the only one that has had a negative experience w/ taking the CAT off. I took it off last year and ran a glasspack in it's place. I'll tell you what, I sure lost a heck of a lot of torque by taking off the CAT. When it came time to get my car to go through emissions I decided to put it back on & boy did I really notice a difference in power. I suggest leaving it on. It also depends as well as to what type of EGR you have. If you have a pack pressured EGR valve then you can possibly cause the car to not run right. Just my input on it.

------------------
- Mike Harvey -
1986 Firebird S/E

 

MIKE! Think about it. That glass pack was probably more restrictive than the converter. Put in a piece of straight pipe and then post your results.

------------------
84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

I'm running the straight pipe until my next inspection in March. I'll get a new one,get inspected,pass and put the straight pipe back on. As for the EGR valve,if the light comes on and the car's performance doesn't fall off or the car doesn't act any different then it's not the valve. LO3/TBI systems require a certain amount of backpressure that the ECM reads to allow it to open the valve at or above 50mph. I've been through replacing the valve,solenoid,cat and such and it still happens from time to time. The only cure I've found is in a Jet stage 2 chip. And the high flow exhaust is worth it. My code 32 started happening at around 40K,shortly after the exhaust swap.

------------------
Mongoose-NCTGA-1990 Pontiac Formula/305 TBI-700R4 with Edelbrock Performer TBI intake,TES headers,and STB,K&N,MSD-6AL,Holley laser shot coil,Accel Extreme 9000 wires,Jet Stage 2 chip,TCI shift kit with corvette servo,Richmond 3.73 gear with Auburn 3 series posi,no cat,SLP 3" cat back,Eibach sportline springs,Energy Suspension poly throughout,Lakewood LCA and adjustable panhard bar package,SSM subframe connectors,IROC wonder bar,Tokico 5 way adjustable struts and shocks,Autometer electric fuel pressure gauge,Alpine,JL Audio,MB Quart,92 GTA taillights,92 GTA aero wing and hatch,Steve Spohn LCA relocater kit,MacEwen White face gauges,84 T/A cold air induction air cleaner,Grant Formula GT wheel.

 

I am running a straight 3" pipe as well. with Edelbrock TES Headers and a custom 3" exaust w/ Flowmaster 80 series and I don't throw any codes. Of course, my previous owner removed AIR and the Smog pump and did some rewiring I noticed so that might be why I don't throw any codes. Maybe I outa give him a call....

------------------
Eric Natzke
91 Firebird 305 TBI

ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-MSD Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone-Free TBI mods
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

Mongoose, the computer opens the EGR valve while cruising and monitors the MAP sensors signal. If the MAP sensors signal changes then there is a manifold pressure change and the EGR is opening correctly. If you have changed all other components of the EGR system then I would look at replacing the MAP sensor. Know the system before you blame the part that registers a code.

------------------
84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

Parts were only replaced when they were found to be defective. The cat was replaced when I went to larger pipes and the solenoid was replaced when it was found to be faulty as well. The EGR valve has never failed as it still holds vacuum when tested. As for "blaming the part that registers the codes",I'll assume you mean the ECM. I've never blamed the ECM for the problem even though I have had to replace it twice for unrelated problems. My statement about the cure I've found being the Jet chip was to let people who are having the same problem know that this is what worked in MY situation and that's all.
And for the record,I did check the MAP sensor and it wasn't the problem either.Imagine that.

 

I bet none of you have ever heard of twin turbo mufflers on a third gen have you? Well thats what i have and when i first got then they scraped like H*** (big suprise)so I put HighJacker air shocks on. But dealing with the cat when i took mine off along with the rest of the single exaust i noticed a pretty significant increase in power and it sounds awsome. The pipes come out under the door.

------------------
Mustangs Suck!
(Especially when they beat you!)

 

Mike Harvey, your car has a v6, I haven't checked yet, but I think the L03 probably has a cam that will allow the engine to benefit from free flowing exhaust in the low end.

[This message has been edited by Keith5 (edited January 04, 2001).]

 

Hey Keith are you talking about a Crane Cam or something like that or maybe a Wolverine cam for my V6? I'm planning on running a cut out after the collectors on my headers when they get installed. So I can run straight headered. I hate having restrictions.
Also CamaroMike thanx for that input. I never did think of it that way about it being more restrictive, good point.
Hopefully by the end of this month my exhaust should be just mean as hell.

------------------
- Mike Harvey -
1986 Firebird S/E

 

No, I was talking about the stock cam of a L03.