Ok, I admit it. I'm a bit of a tree-hugger. So I'm feeling a little guilty about gutting the cat. And ditching the smog pump. And the EGR. But I'm trying to convince myself that a healthy, well-balanced engine will run cleaner than normal. For example, I had all the injectors flow-matched. Before their flow rates varied about 8%, now they're all within 2% of each other. So I'm thinking that my air-fuel ratio will be 14.7 in all cylinders, rather than having the computer find some happy medium between too rich in one cylinder and too lean in another. Also I was kinda hoping this would help with gas mileage. I had the engine balanced during the rebuild too. So what do you guys think? Please tell me I'm not as polluting as I think I am.

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91 Z28
Come see The Vicious...

 

It'll run pretty good... people have passed emissions without any smog crap on, I'm one of them... (with the new NJ dyno emissions check w/no smog pump)

Do yourself a favor, and mother earth, and invest in a high flowing cat, it won't hurt performance much, if at all, and it'll be healthier for your nose, ever smell a car without a cat? YEah... blech.

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1985 Camaro SC - 2.8L, auto.

C'mon, spin 'em for papa...
http://www.xenodrgn.f2s.com/Frontright.jpg

 

Boooooooo......

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

I'll second that Boooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

 

If only it were that easy....... You really won't be able to remedy the ECM doing the 'rough estimate' thing with the air fuel ratio. The factory ECM system is a batch fire system with one switching style O2 sensor.... It just isn't going to be able to tune the engine as well as newer style EFI systems.... No meeting LEV standards for us....

The mileage and performance of an engine with the kind of mods that you have is completely dependant on the tuning in the PROM. You can have all of the emissions equipment on there and working perfectly but, with a less-than-ideal PROM in the car, it will be slayin trees left and right. So make sure you either get the equipment to burn your own PROMs and get it right yourself, or have somebody reliable and proven get one tuned to your package. It's all in the PROM, baby........

But rest assured, if/when you get the PROM tuned perfectly to your combo, the engine will run clean enough to keep you from losing sleep over all of those poor trees......

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

Matt87GTA is right-on with what he said in his reply. when you say healthy, i asume that means you included a bigger cam along with whatever else you did? at idle and without a cat, the hydrocarbons are killing more of your brain cells than good green bud will. if your more stock, then it"s o.k. but on a stock setup, you need a small amount of backpressure for peak low-end performance so gutting the cat was a bad idea

 

Birds are falling out of the sky because of me! Ahh, the guilt!! I only gutted the cat because it was clogged and making a bunch of ratteling noises. And I just don't have the cash to spring for a new high-flow converter right now. As for the EGR, I couldn't figure out how to make it work with vette heads and my Edelbrock TES. And the smog pump, well, it was in the way. I had Ed at Fastchip burn me a PROM for my combo. About the cat, since I deleted the air pump, I've heard that the converter will get clogged easier since I don't have that air going to it. Is this true?

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91 Z28
Come see The Vicious...

 

Rofl.....

Sure...... I believe you..............

Well, sort of. The A.I.R system is designed to provide fresh air to the exhaust manifolds and the catalytic converter to induce more oxygen that will aid in burning any excess hydrocarbons that are left over from incomplete burning of the air/fuel mixture into the engine (this is primarily for emissions concerns on cold starts - which is when harmful exhuast emissions are the worst - but also aids in warming up the O2 sensor faster with all of the extra burning of fuel going on in the manifolds, which gets the ECM into closed loop faster which runs the car much 'cleaner' than it does in open loop... also aiding in emissions, and performance and driveability). So by removing the 'smog' (A.I.R. - Air Injection Reaction system) pump, you are not going to have that added oxygen for 'reburning' of excess fuel supplied to the manifolds or the middle of the catalytic converter.

The factory style catalytic converter is a three chamber design. It has an initial chamber of catalyst material that aids in the burning of the excess hydrocarbons (fuel) and lowering of NOx emissions. Then it has a middle chamber where it receives the fresh air from the A.I.R pump. This chamber basically dilutes the exhaust and allows the final chamber to be much mre effective at finishing off the 'cleaning' of the emissions. That last chamber has a slightly different type of catalyst material in it that is more sensitive to being overloaded with hydrocarbons, but is more effective at burning them and lowering NOx emissions. So the overall system is designed to do the best job possible at getting 'clean' emissions.

So removing the fresh air from the equation could cause the catalytic converter to fail since it is being slightly overloaded with hydrocarbons compared to what it was designed to handle. But if the engine is running well, it should not ruin the converter just by removing the A.I.R system. The problems with the catalytic converter breaking up and melting would be when/if some sort of excessively rich mixture condition was present that completely overwhelmed the abilities of the converter to do it's job and pushes it to the point that it overheats, melts, and eventually clogs up with it's own internals. So it is true that removing the A.I.R pump (basically the pump is the entire system...) can cause the catalytic converter fail prematurely - but it is likely not going to directly cause the failure...

Now, for those of you that followed all of that information well, I have this to point out. GM never got our cars to run 'clean'. They slapped a band aid on the cars in the form of the A.I.R system. This system basically 'dilutes' the emissions of our cars and makes it seem like they are running 'cleaner' than they really are. The cost in all of this band aid slapping: power. This system of pumping air into the exhaust is all powered by the engine in the first place, costing power and therefore requiring us to use more rpm and fuel to get what we want for performance, at any given time, from our cars.... So did the 'emissions equipment' really lower the emissions of our cars? I say no...... not that it really matters anymore... just funstuff to think about....

Hope that helps a bit,
Laterzzzzz

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

[This message has been edited by Matt87GTA (edited November 05, 2001).]