eliminating cats?

[goldie castaneda]

aloha gang

 

rebuilding my block right now and just wondering if eliminating the cats is worth it. I have heard about them blocking and messing up all the cash just spent on the motors. whats the best way to do this. thanks

[CaliChevyV8]

If they melt they can screw things up. Besides that I have heard it is not worth removing them, where you from?

[Justin Lamanna]

How are you rebuilding your engine? Depending on what level of performance you are looking to get would determine whether you want them or not, IMO.

[KissMySilvSS]

If you in an emissions nazi state, just gut the insides and leave them on.

[misterp]

Ugh this needs to be a sticky... this has been a frequent topic.

 

CAT GUIDELINES:

* Stock cats will slow a Radix-equipped truck 1-tenth of a sec in the 1/4-mile;

* Stock cats will make almost no measurable 1/4-mile difference on a N/A truck;

* Stock cats smooth the exhaust note, meaning that it is a little bit quieter and a lot less 'crisp' - removing the cats will affect exhaust note mostly by allowing you to hear each individual cylinder pulse, you can distinctly hear each cylinder firing (the exhaust will get 'raspier') and actually feel the effect on your hand when held next to the exhaust tip;

* All cats rely on an engine with a correct air/fuel ratio, too much raw/unburnt fuel exiting the engine will eventually clog/foul/kill a cat so make sure your tune is right;

* All cats rely on a fuel of 94 octane or less, high octane fuels will tend to clog/foul/kill a cat so use unleaded pump fuel only;

* All cats rely on an engine with 'realistic' cam and ignition timing - use of a cam with long overlap or over-aggressive scavenging will allow too much raw/unburnt fuel to exit the engine and clog/foul/kill a cat so stick with streetable cams and tunes;

* If you are using NOS you are placing your cats at great risk;

* If your locality requires sniffer testing it is not worth it in money/effort to remove the cats and evade the law;

* If you are making more than 8-lbs of boost (assuming stock cubes) you might consider investigating metal screen (high flow) cats IF your intention is to build a maximum effort sniffer-friendly vehicle.

 

Mr. P.

[thomp62301]

for those of us running nitrous, should we not have cats at all?

[misterp]

for those of us running nitrous, should we not have cats at all?

No, it is not necessary to remove the cats on a typical NOS equipped engine - just make sure your A/F ratio under enrichment is correct. The job of the catalytic converter is to burn any raw/unburnt fuel that has escaped the combustion process, and when you're on the button you're dumping a whole lotta fuel and oxygen into the exhaust system (including more unburnt fuel) and because of the increased oxygen content from NOS injection the converter is guaranteed to combust whatever is left, meaning a spike in converter activity and temperature. Since NOS is usually limited in 10-20 sec doses cat temps normally do not get out of hand.

 

Another factor is wet vs. dry vs. direct port NOS delivery. Dry systems are pretty safe as the NOS and fuel are well mixed and introduced to the combustion chamber in an even fog. The designs of cheaper wet fogger systems are where you can find uneven distribution of NOS and enrichment fuel, and in enough quantity that it can cause serious problems, least of which I guess would be converter failure but I hope you are seeing my point here. If you are going to use NOS get either a dry system or a very professional direct port kit. Whichever system you install make sure you verify proper A/F ratio and reliable system operation.

 

Mr. P.

[detjoe]

good job MrP a mod will make this a sticky!

[goldie castaneda]

aloha gang

 

rebuilding my block right now and just wondering if eliminating the cats is worth it.  I have heard about them blocking and messing up all the cash just spent on the motors.  whats the best way to do this.  thanks

<{POST_SNAPBACK}>

hawaii

[rab986]

for those of us running nitrous, should we not have cats at all?

No, it is not necessary to remove the cats on a typical NOS equipped engine - just make sure your A/F ratio under enrichment is correct. The job of the catalytic converter is to burn any raw/unburnt fuel that has escaped the combustion process, and when you're on the button you're dumping a whole lotta fuel and oxygen into the exhaust system (including more unburnt fuel) and because of the increased oxygen content from NOS injection the converter is guaranteed to combust whatever is left, meaning a spike in converter activity and temperature. Since NOS is usually limited in 10-20 sec doses cat temps normally do not get out of hand.

 

Another factor is wet vs. dry vs. direct port NOS delivery. Dry systems are pretty safe as the NOS and fuel are well mixed and introduced to the combustion chamber in an even fog. The designs of cheaper wet fogger systems are where you can find uneven distribution of NOS and enrichment fuel, and in enough quantity that it can cause serious problems, least of which I guess would be converter failure but I hope you are seeing my point here. If you are going to use NOS get either a dry system or a very professional direct port kit. Whichever system you install make sure you verify proper A/F ratio and reliable system operation.

 

Mr. P.

<{POST_SNAPBACK}>

 

I know that I am new here but I am also a long time veteran of nitrous. DO NOT get a dry system. I think Mr P must have just gotten them mixed up but a dry system is the one which relys on the ECU to compensate for the lack of fuel because it does not supply any with the nitrous. Also a dry system is Raw nitrous sprayed before the actual intake which never is distributed evenly to each port which is also another problem becuase the ECU doesn't know which port needs more fuel. It only knows what the the O2 sensor tells it so in most failures the back cylinders are melted down due to a lean condition. Please do your research before actually buying a kit because although many people run it, few know what they r doing and end up with a $35k grenade in their garage.

 

Good luck with whatever u do and remember to do your research.

 

Steve

[misterp]

Thanks for correcting me You and I are on the same page, I did not explain myself well earlier. I think we can all agree nothing beats direct port for assuring proper NOS mixing and delivery.

 

Mr. P.