Anyone heard of S/C 5.0 letting go?

[nicksender]

You shouldnt see and extra boost from going with O/R X.

I agree; if you saw any change in boost pressure it would be a loss of boost if anything when the exhaust is opened up. IMHO.

 

[Riptide]

/agree. Melted cats are a sign up way too rich, which means it shouldnt have blown up then, unless it was way to much timing. The two cant be related any way that i can rationalize in my head.

IIRC it is exactly the opposite. Rich running cars produce cooler exhaust temps. Running lean is more likely to melt it.

 

[Ray Lucca]

What are the odds that the Cat protection was turned off in the Custom Tune??? I know the FRPP and Roush Tuned set-ups keep it on. Ck with Justin at VMP but I thought he said he also keeps it on in his Tunes...

 

[kevinp]

IIRC it is exactly the opposite. Rich running cars produce cooler exhaust temps. Running lean is more likely to melt it.

no

Exhaust temp has nothing to do with it. unburned fuel (rich) lights off the converters and melts them. Why do you think all newer cars have such sophisticated misfire detection? So raw fuel doesnt hit the cats.

Here it is straight from a converter manufacture:

http://www.car-sound.com/04basics/04failures02.asp

 

[Riptide]

Understood. So even if exhaust temps are cooler with the richer mixture the chances of an ignition post engine are higher which is what (typically) cause the destruction of the converters.

 

[kevinp]

Understood. So even if exhaust temps are cooler with the richer mixture the chances of an ignition post engine are higher which is what (typically) cause the destruction of the converters.

Correct, converters are pretty far from the exhaust port usually and can easily handle even a lean running supercharged car's exhaust temps that far away.

But throw some unburned fuel in there and they just start melting themselves down. The tune is very critical, most 'safe' blower tunes I have seen can get down to 10:1 A/F and that will wreck converters in short time. IMO if you want to retain the cats back the boost down and run it around 11.5:1 A/F, more boost and 10:1 a/f will probably net around the same power anyhow.

Dont forget that GT500s, ZR1 corvettes and CTS-V caddies all make 500+ supercharged HP from the factory and have cats. Like anything else its all in the tune, if you plan on keeping it rich its best to take the converters off.

 

[Riptide]

I concur. Kenne Bell and Whipple sell kits that include tunes which work and work well with the stock cats. Very few failures that I'm aware of at this point. It's typically a custom tune with an aftermarket converter that 'splodes.

 

[kevinp]

I concur. Kenne Bell and Whipple sell kits that include tunes which work and work well with the stock cats. Very few failures that I'm aware of at this point. It's typically a custom tune with an aftermarket converter that 'splodes.

Yep, I have the stock cats on mine with the TVS (I hate stinky cars, unless it has C16 or something in it) and have no issues. I can see keeping the a/f a little rich if you are pushing it really hard though, so ditching the stock cats may be best, little more exhaust flow cant hurt either.

 

[Riptide]

The smell is a negative IMO as is the sulphur dioxide and other crap the car spews into the air without cats. It's just my personal preference but I'm not taking mine off unless I'm forced. It's a street car. A race car would be a whole other story.

 

[kevinp]

The smell is a negative IMO as is the sulphur dioxide and other crap the car spews into the air without cats. It's just my personal preference but I'm not taking mine off unless I'm forced. It's a street car. A race car would be a whole other story.

I'm far from a greenie but I have to agree there is really no reason to ditch the cats unless you are making some serious power on a daily driven street car.

Years ago with carbs and early fuel injection cats were bad juju since it was hard to control the a/f at WOT, plus early cats didnt flow worth a crap. But these days with excellent fuel control and decent flowing converters I dont see a problem leaving them on unless it cost me a lot of power.

 

[SC2011GT]

I have completely stock exhaust (cats, mufflers)
5K miles w/ KB 2.8 and the KB supplied tune, no problems and I run this thing pretty damn hard in the 100 degree heat.

 

[zilla8]

I thought I should come on in and clear a few things up.I'm one of the early KB owners who had the problem with my cats.

although the cats failed and contributed to my ultimate engine problem it may not have been the only thing involved.

It was not tune related as my dyno tune was pretty conservative and my tuner is one of the best in the country.

It's no secret that running cats on a FI car is not the best thing to do if you don't have to run them.I don't want to dwell on my issues as they are behind me now.

I had my motor rebuilt with all the good stuff Diamond forged pistons 10:1 comp and Manley pro series rods and I also have ARH 1 7/8 longtubes with offroad X and Gibson axleback exhaust.

I have around 4K on the new motor and I'm loving life.I'm making 580rwhp at 9# and I may go to 11# but we are limited to 91 octane here in California.

I can tell anyone who is considering a blower that this KB 2.8 is a monster and very well built.They are local for me and have been great with customer service and support.

I have not been to the track yet with the blower but when I get some numbers I will be sure to post em for you.I hope this helps and don't worry if you have cats just make sure the tune is spot on and not dumping fuel to cool the cats.

I had Magnaflow HF cats that failed but I also saw 2 others with stock cats melt on supercharged cars.

 

[JDV]

Thanks for posting. I would like to know exactly what caused your cats to melt though. Has that ever been discovered for ya?

 

[TBuick87]

I thought I should come on in and clear a few things up.I'm one of the early KB owners who had the problem with my cats.

although the cats failed and contributed to my ultimate engine problem it may not have been the only thing involved.

It was not tune related as my dyno tune was pretty conservative and my tuner is one of the best in the country.

It's no secret that running cats on a FI car is not the best thing to do if you don't have to run them.I don't want to dwell on my issues as they are behind me now.

I had my motor rebuilt with all the good stuff Diamond forged pistons 10:1 comp and Manley pro series rods and I also have ARH 1 7/8 longtubes with offroad X and Gibson axleback exhaust.

I have around 4K on the new motor and I'm loving life.I'm making 580rwhp at 9# and I may go to 11# but we are limited to 91 octane here in California.

I can tell anyone who is considering a blower that this KB 2.8 is a monster and very well built.They are local for me and have been great with customer service and support.

I have not been to the track yet with the blower but when I get some numbers I will be sure to post em for you.I hope this helps and don't worry if you have cats just make sure the tune is spot on and not dumping fuel to cool the cats.

I had Magnaflow HF cats that failed but I also saw 2 others with stock cats melt on supercharged cars.

Since I HAVE my cats with a Roush TVS and a Lund tune, what exactly should I ask him in order to Protect this 7K Motor??!! Cat Protection On??
btw, I posted this on S197 and they basically thought I was Nuts!!

 

[TBuick87]

btw, can a Dashhawk gauge confirm this safe A/F: "around 11.5:1 A/F"

 

[TBuick87]

Thanks for posting. I would like to know exactly what caused your cats to melt though. Has that ever been discovered for ya?

Ditto!

 

[zilla8]

The cats will start to come apart from the high exhaust temps combined with the raw fuel.Both Metal and ceramic cats can basically meltdown and fail on a car with forced induction.

If you do a search of melted cats you will see lots of cases of this happening with supercharged/Turbo cars it's nothing new.

I don't want to cause a panic and have everyone with cats and a blower think they will have a problem lol

that's not the case at all because there are plenty of factory supercharged cars that run cats.I'm sure Jon Lund would make the best adjustments to your tune if you are running cats as long as he was aware of it before writing the tune.

 

[JDV]

So yours gottoo rich then at some point? A good tuner should be able to ensure it's safely rich without being cat-killing rich.

 

[kevinp]

The cats will start to come apart from the high exhaust temps combined with the raw fuel.Both Metal and ceramic cats can basically meltdown and fail on a car with forced induction.

If you do a search of melted cats you will see lots of cases of this happening with supercharged/Turbo cars it's nothing new.

I don't want to cause a panic and have everyone with cats and a blower think they will have a problem lol

that's not the case at all because there are plenty of factory supercharged cars that run cats.I'm sure Jon Lund would make the best adjustments to your tune if you are running cats as long as he was aware of it before writing the tune.

Cats can also melt down on a naturally aspirated car, like I said earlier exhaust temp has little to do with it. A properly lit off converter is hotter than than the exhaust gasses coming out of the ports. Thats why the misfire detection is there, they didnt do that thinking you were going to put a blower on the car.

Its pretty simple, if you run cats dont go too rich whether you have a blower or not. Same with using a two step, those will melt cats in no time as well.. If your tuner calls it a 'safe' or 'conservative' tune with rich WOT a/f take the cats off, an off road pipe is cheap.

 

[zilla8]

This is really not that big of a deal and I have offroad x and no cats now so problem solved.If you look at most blower set up's the A/F will allways be considerably richer then a N/A car for obvious reasons.

I just wanted to shed a little light on what happened with my car,To the OP sorry for the semi thread jack