I have the LE 3 cam which is 24X/25X specs on a 109LSA, Lloyd doens't grind this cam anymore so partial specs are OK to give out since his new cams are much different.

Anywho, my problem is this, this set up with everything in my SIG like FLP long tubes, I put on the FLP cats and when left idling the driver's side cat start to develop a red spot in the middle, so starting to glow, I don't know if it did this before and may I should try swapping cats around from one side to the other because the other side does not glow, I know the set up is pretty wild, I'm idling at 1000rpm, I have the timing at 34* at idle so the only thing I can think of is the thing is dumping too much fuel down one side?

Thing is, I limited the BLM's to 130blm and took fuel out in the maf table so t he thing does not compensate fuel at idle, so I go the o2 readings really low (sometimes the left o2 lean comes on now) because I took out fuel there and the pcm can not compensate, did it to both sides, all seems fine on the right side and the left side I though though this fixed it but it did not but it did help I think, so I took out more fuel just on the left side (driver's) and I swear it now takes even longer to start glowing.

I drove around for 10 mins and stopped both cats were fine, let her idle and then I start seeing a red spot developing on the left cat again, do you guys think its a misfire? the car runs really smooth and pulls hard to 7k rpm and I use LS1 coils so I doubt its misfiring but who knows, may change the wires on the side? I have no idea I am lost, is it just cuz its too much set up for cats?

Any help would be appreciated cuz I'm lost.

 

I don't understand why you are running cats with a setup like that. I wouldn't think that camshaft could even pass a sniffer...

 

Not on its best day with any tune.

 

LOL its always nice to try, and it doesn't smell out the back, plus I swear it drives better with cats on and has a different sound, so what you guys think, am I too lean that it is misfiring on that side because its so lean causing unburnt gas to burn in the CAT? I'm going to try giving her more fuel but I dunno weird, is it normal for a big cam set up to burn up cats ?

 

I have almost that same cam but with a 110 lsa. With a 4 gas analyzer, I think it can be done. I am going to get an O2 bung welded into the exhaust pipe right before the axle to let more air in, and tune the car with the gas analyzer. With denatured alcohol, tuning with the 4 gas, and introducing fresh air after the cats, I think it can be done. Hopefully I will have the 4 gas soon.

My cats don't glow at idle, I think you are running lean, you can't really trust the stock O2 sensor with lots of overlap anyway.

 

So do you just let your o2's do their job at idle? I'm making her run lean on purpose, i thought I was running rich to have them glow no? How is your tune, do you just let the o2's control your air at idle? If so then you are running a lot richer then I am at idle.

 

One Fast GTA brought up a good point. Put your are pump back on and use it to add air to the Exhaust. before the cats. With the cam you are running alot of un-used fuel is going to the cats at idle. I am sure your AFR is good but it is the Un-burned fuel that collects there that will get you.

I have a freind who almost lost his eye cutting out a cat on a big cam car. It had raw fuel inside of it and exploded in his face.

Good luck man!

 

I'd guess the cat is glowing because with all that overlap, its getting healthy amounts of unburned fuel AND air passing through the cylinders at idle, and its burning on the cats = heat. Can't rely on the O2's because they're just going to see the excess air and tell the PCM to pour more fuel in.

 

Yes Injuneer, thats exactly what I thought, putting back the air pump will not do anything, its all that extra air and unburnt fuel through it so the end result is the cat is doing too much work, so in the end the cat is doing it's job but its asking too much from it, its like putting a big bomb inside a small room.

Here is the thing though, I backed out the fuel quite a bit and it's still doing it, I limited the o2s and the o2's started to read "4" so basically a lot of oxygen meaning a lot less fuel then when they read 4-800 or whatever when they do their job, but the darn things still try to glow, so now I'm thinking that when I back off all that fuel perhaps I'm still getting the same amount of uburnt fuel past the valves because of the overlap but now the engine doesn't have much to burn, its hard to tell but in the most likely case the engine is happy because I'm not dumping a ton of fuel like I would if I let the o2's control the fuel at idle, but I am still no matter what, getting the unburnt fuel past the valves, thus by leaning her out the difference is great to the engine but not to the cat because in the end its the over lap that kills it.

The other thing is if I start pulling even more fuel out I think I might run into a problem where the engine might get a lean misfire causing even more fuel to go to the cat LOL.

So I think there is only one thing that will help keep the cats protected, pull the fuel back at idle like I did before so the o2's read very little, not "4" but I had her at about "60" that is where the engine seemed to run the best and when coming to a stop didn't want to die, basically ran real nice, so get the fuel back to that point but at the same time bring the idle up from 1000 to about 1300 rpm, the higher the RPM the less fuel may start to go past the valves because with more RPM the less the overlap affects fuel getting past because it's more efficient.

So I'll try that, and I have another theory, for now I have about 34* at idle with this cam (closed throttle), and in the normal world the higher the timing the more heat in the chamber but the cooler the exhaust, I used to have 32* at idle but brought her up by 2* and I don't think it helped at all. This got me thinking, the more timing on a big cammed engine, the cooler exhaust as well BUT! That unburnt fuel getting past the valves has now an even less chance of burning in the header because of the temperature so all that nice fuel and nice air goes to the cat and it's now overloading the cat, so if I back off the timing, this will make the exhaust run hotter, now I can't back off too much because the cam wants the high timing, but I'll be running higher idle too so I may not need all that timing, so if I back the timing up say to 24*, the exhaust will get hotter, hotter exhaust may = the unburnt gas coming past the valves pay now start to burn in the header, back it off too much and I may get a glowing header like any time you back off the timing, but this amount may not affect the header glowing at all but burn up some of that extra fuel that got past the valves because when the exhaust valve opens it may introduce fire to the exhaust because the combustion process is still taking place, that fire may ingnite the excess fuel, it will burn in the exhaust, so by the time it reaches the cat there will be less fuel for the cat to burn !

All these idead in my head are starting to make sense so I'll be trying it all, this will most likely withought doing anything to the fuel, say it was reading 60mv on the o2's will bring it up to prolly 300 if not more because the less timing and all that burning will burn up that excess air in the exhaust as it will be used up in the burning process.

 

damb it that didn't work, next try will be upping the temp the car is running at from 180*F to say 210*F see what happens,

Ok I tried 1300rpm idle, low fuel reading 60mv on each side with only 2.3 BPW at that RPM and 23* of timing, darn it still glow LOL, the header primaries only read like 110-130*C so they are cool with this but the cats read 500*C LOL after idling for a while, then I tried all the same except 25* timing and normal fuel so let the o2's do their job, I didn't measure the temps on the headers/cats but they cats didn't start glowing so fast and were only glowing in the middle/bottom portion instead of quickly and spreading throughout the cat with low fuel, so either the extra air from the less fuel is just helping the fuel getting by the exhaust burn even nice then say more fuel so the cat doesn't burn it as nicely or I'm misfiring with lower fuel letting even more fuel get by.

Next try will be hmm.... 1400rpm using both ways, low/high fuel. Then maybe try all the same but bring the timing to 33* and see what happens.

But honestly with the low fuel/1300 rpm cat starting to glow business, the car doesn't stink at all maybe she will actually pass the sniffer that way, they don't let them idle too long on the IM240 LOL I hope not that would suck, thing is now I need the latest version of tunercat to turn off the SES light because she goes into open loop which is still LEAN as I altered it but the SES light may make them end the test.

 

You will have to use a wideband and a gas analyzer to pass the sniffer. I use almost 50* of timing when cold and warming up, because that's what gives the best vacuum. As the car warms up, timing is slowly pulled out thru the startup spark advance table. My car likes the most timing to get decent vacuum to work the power brakes, and I still have a vacuum canister. No matter how much fuel I pull out, mine still smells rich, although it may not be. Most emissions stations have an idle rpm limit, usually 1100 rpm, so you may have to check your local laws.

I think the only way to pass is by tuning with a gas analyzer, denatured alcohol, the computer and maybe welding in an O2 bung after the cat to put in some fresh oxygen if needed. The biggest problem that I have is finding someone local who will let me tune with their gas analyzer, most shops won't let me for liability reasons, so I have to find a way to buy my own, but they aren't cheap.

 

Yeah I already knew that, making it leaner won't get rid of gas smell well not as much because no matter what you do, you still have the same cam and you will still will let fuel go by the valves. I will work on it, I already know what to do to make the car run great, already have that tune and love it, yes I have A TON of timing and big cams love it down stairs, no I've been tunning this set up atleast 50 times, about 50 times on my setup before this, I've spent my whole life LOL making her run as good as I can for now, I have a few more ideas in some areas but thats it.

Now this emissions tune is a whole different ball game, I'm cool with how the engine works, and what needs to be done when tunning, heck when you've uploaded over 300 tunes if not more LOL between your car and others you start to come up with new ideas when doing them, otherwise I would stop on tune number 2 but no. basically anything new that pops into my head I experiment with cuz thats the only way, sometimes I come here for advise but pretty determined on my own thing, this emissions tune is fun though, something totally new all together,so my weekends will be spent with my car.

 

Would it help to move the cats back, if it is possible? They're still going to get the same amount of A/F, but may not be as hot to burn the entire mass.

 

No it wouldn't I don't think, reason being is this, it is not that the exhaust pipes are too hot, the trouble is that there is too much fuel getting by, unburnt fuel can destroy a cat, unburnt fuel will make a cat reach upwards of 2200* where operating range is around 1200* or so, so no matter where it is placed, as soon as it gets hot enough to light the unburnt fuel then the heat just escalates, the only thing that would help I think is bigger cats, the bigger the cat the more unburnt fuel it can handle.