CAT bypass pipes with no CEL's ? (5.2)

No sweat off my balls, Dave. My car is a 95.

It just seems that without cats on an OBD II car the rear O2 sensor is going to be telling the ECU that the car is running too lean. How it reconciles that with the front sensor reading is buried in the ECU. If it does richen out the mixture that would account for the smell and also some increase in HP.

Anyway, I know with my car the exhaust smells more on the rich side when the cats are off. (Car came with hollow OEM cats which I had to replace to get through CT emissions. ) The cats are very effecting at cutting down un-burnt HCs. I guess it depends on your nose and experience as to whether someone can smell the difference. Pretty obvious to me, not just the smell, but eyes burn as well. And if(??) the OBD II car goes even richer.....

 

John,

Even with CAT's (and no muffler), the smell and fumes from my car the first few minutes and not fun. Not sure what happens after the first few minutes where it then goes away...

 

Don't know for sure but I would suspect that until the temp comes up the car is running open loop and on the rich side.

Also, if cats aren't hot they don't work very well in reducing HCs.

 

Yes, I get awesome flames when I shift gears. My mirrors light up at night when I shift, it's so cool! Here is a crappy pic when I had a Tubi muffler, but I have a Capristo Level 2 now and the flames are even bigger!
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Any burns / melting going on with your bumper?

 

No issues at all. The flames only last for a fraction of a second in between gear shifts. Here is the video, you can see the flames at :40 seconds. They're wayyyy brighter/cooler at night.

[ame=http://www.youtube.com/watch?v=TfI5h0IvBCs]Ferrari F355 Loud Acceleration! Exhaust Flames! **1080p HD** - YouTube[/ame]

 

Flames would support the mixture being rich, no?

 

For what it's worth....

I have a 98 GTB. The prior owner had Penske-Wynn upgrade the exhaust system last year as part of the engine-out major. Fabspeed ceramic coated headers were installed along with a Capristo Stage 3 exhaust. Penske-Wynn recommended against cat bypass pipes because of issues with CEL's given that the car is a 98, including issues with how the ECU controls the engine. The person doing the work on the car has 45 years of experience as a Ferrari tech, so there seems to be some credibility to the recommendation....but I am not qualified to comment on how much of that is art vs. science. The prior owner ended up going with Fabspeed cats. Even with this setup I get an occasional CEL and I have read about other owners who see the same problem with the Capristo and hiflo cat setup. I looked at the Capristo O2 Simulator (which interestingly enough is no longer listed on Capristo's US website), but the simulator requires being installed and "trained" with the factory exhaust system before switching over to the new exhaust system so 1) I didn't want to go through the havoc of re-installing the stock system just to train the simulator and 2) I also wondered whether or not this would effect real things going on within the ECU including mixture, etc. I am happy with the system I have, but still haunted when I occasionally have to reset the CEL as I am not completely sure if I am just resetting a warning light...or whether the warning light is a sign that a bigger issue is indeed present which might be causing a mixture issue, etc. I've driven the car 1,000 miles since owning it and had the CEL light come on 3 times...usually after a spirited drive at higher speeds and then slowing down into city traffic. The good news is that the CEL doesn't come right back on after resetting it.

 

Matt, the simulators are now illegal, probably why they no longer have it on the site. I was gonna have my mad scientist buddy make them but now I plan to just get hyper flow cats and stay with the original plan from months back.

 

Weren't they always "illegal"? These fell under the label "For track use only" which is true of many of the goodies that we add to our cars even if we rarely see a track. Or perhaps these were explicitly made illegal, whether for road use or not? Either way, I agree with your approach as I have seen enough facts to make me comfortable with putting bypass pipes on a non-95 car. Also bypass pipes are far from free, but the prior owner for my car spent $1,995 on the Fabspeed cats so those weren't exactly free either.

 

Matt I'm sure as you say they were always illegal. I should have said that they now likely enforce it.

 

Well, if you want to talk legal, it is against federal law to remove the cats in the first place. Anyway, I replace the hollow OEM cats with Nouvalari cats direct from Nouvalari USA for $1100.

[edit] I did a little search and found an article on Import Tuners where they tested a car with OEM cats, hi-flow after market cats and test pipes. Going from OEM to hi-flows yielded a 2% increase in max HP. Going to test pipes yielded only another 0.66%. Frankly, I'm not seeing the point of test pipes on the street.

 

John my motivation have nothing to do with HP, it's all about getting heat out of the car to save my OEM headers and prevent the break down of ceramic media getting into my combustion chamber. My motivation is preventative only.

 

Personally I think the heat in the header is more a function of how you drive than the restriction of the cats. I think of it this way. The heat of combustion is Z BTU/LB of fuel. So the amount of heat released in the engine per unit time is related to the fuel consumption, Y LB/sec x the heat of combustion so you have (Y x Z) BUT/sec released. So the more you are on it the more fuel flows and the greater the BTU/sec released in the engine. Next the question is does the engine generate more HP with test pipes due to better flow or improved efficiency. If it is just better flow, and no change in thermal efficiency then this means that the increase in HP comes form burning more fuel. So when driving at the same HP level the same amount of heat gets dumped into the headers. But if it comes in part from higher efficiency (which I'm sure it does in part) then more heat is extracted as work and less heat is dumped into the headers. But even if all the increase in HP comes form improved efficiency and that is on the order of 2% (which seems a lot) then this reduction in heat into the headers isn't going to amount to squat compared to driving hard or easy.

As for breakup of ceramic cats, get Hyperflow metallic cores if it's a concern.

 

Yes John, Hyperflows are the plan. I've read (don't have any proof) that the CAT's are restrictive and that retains heat over test pipes. But, I've read wrong info before. It's very hard to locate facts.

 

Let me make it easy. Go out and drive you favorate route. Play Marrio Andretti. Be constantly on it. Reving to 8k. Keeping the engine in the power band. Punching it out of turns. Say doing that you burn a tank of fuel in an hour. Now, go out on a Sunday drive with your wife. Drive the same route, but keep the revs at 4-5k or below. Just cruz around. It takes 2 hours but you ony burn 1/2 tank of fuel. That's 1/4 tank per hour compared to 1/tank per hour or a 75% reduction of heat released which has to pass through the exhaust. And that isn't even considering that the exhaust temperature will be higher when you are on it. So yes, cats restrict flow and that results in slightly higher exhaust temp, but it can't be anything near the difference in heat rejected by the engine under the the different driving conditions I discribed.

Remember that thermal efficiency of an engine runs about 30% tops. In terms of heat, the heat in = the work done plus heat out. Qin = W + Qout. Efficiency W/Qin. 70% of the heat released in the engine ends up in the cooling system and or out the exhaust.

So I'll sum up by saying that I agree that removing the cats may reduce exhaust temp slightly but that reduction won't reduce the heat in the headers anywhere near the differences seen under different throttle conditions.

For me, first thing I'm doing next spring is removing the new cats on my car and putting the old OEM hollow cats bach. Not because I am worried about headers or cat breakup, but because I want to save the cats for emissions testing only.

 

Why not just make the car run right and leave the cats on and the air clean? People who are not racing these cars at wide open throttle really should leave the emissions intact. There is nothing to be gained by generating potential horsepower then not using it.

 

FBB, I know you think I don't respect him since I don't believe in the GCK, however, I do respect Dave Helms.

He told me two things about CAT's:

1) The restriction will cause excess heat in the headers

2) Ceramic elements can break down and end up in the combustion chamber causing damage.

So, this is exactly my motivation to remove them and replace with Hyper flow or straight pipes.

PS, Dave also told me that late some model 355's had stainless steel elements and said those are as good or better than Hyperflow. He said, if I have those, I'm fine. To date, I've not heard this from anyone else but I do plan to check with a bore scope in the O2 sensor holes..

 

The car does run right as is evidenced by the exhaust gas analysis pre cats. I just don't know how long the Nouvalari cats will last. So I chose to have them on the car only when needed for emissions. As my car is a 95 cats or no cats has no effect on mixture control.

[edit] Other than that, I pretty much agree with you, particularly your last sentence.

 

Cam overlap is good for cooling

No heat issues for me with a stock rear grill, 200 cel cats even in 100 degree days and heavy LA traffic. Even passes emissions.

Get the entire package working perfectly and its good vibrations. Make sure every ignition signal and fuel injector pulse are accounted for.
If then you want to play you have a valid baseline to go nuts. Then again I am a moran with way too much time on my hands.

 

Anyone have any experience with one of these?

O2 Simulator Mini Cat Cel Fix best oxygen sensor simulator made.

 

FBB, I have to agree with Dave here. While I don't want to harm the environment, and most "normal" cars have no issues with cats, but the 355 suffers from many ills that are either directly or indirectly caused or promoted by stock cats. Or maybe more correctly, removing them may minimize the issues people experience with this particular model.

I know that it can CAUSE a few issues with the 5.2 cars, but without even considering the HP gain, and only if your local laws tolerate it, running a cat-less 355 has a lot of benefits.

And for the tree huggers out there, most 355's are not daily drivers and those few that run without cats are not a global emissions issue.

 

Read post #41 about how Johnk described function. I don't believe there is any evidence of 1 or 2 happening when there is proper mixture control. Futhermore a significant number of 355's are babied and of low miles and never achieve the heat that 355 challenge cars see at race speeds yet the 355c's cats were not burning down. For your proposed function, hyperflows or straight pies are a bandaid for other problems upstream of the cats.

 

I understand your point but if the nouvolari cats were any good they would run at least as good as any OEM cat which is good for maybe 100k miles? Assuming the mixture is right. Why is it that some 355's the cats last forever and some 355's cats are dead in 20k miles? I'm not a greenie. I drive a diesel truck, shoot lead bullets, and my racecar gets 2 laps per gallon! But on a streetcar there is no reason to break the law or pollute because these cars can run right and cats can last 100k miles if the cars are running right.

 

To be honest, it is my intension to put the hollowed out OEM cats back on, but not only am I crumpy, I'm also a lazy SOB and I haven't gottem around to doing so yet. By the time it gets warm again here in NE, I'll only have one season before the car needs emissions testing again, so I may leave the Nouvalaris on. According to Glen Lite at Nouvalari USA, they should last just fine.

As for OEM cats failing, good question. My car was maintained by Ferrari of Huston and Boardwalk Ferrari before I got it and the records show that early on the 1st owner was complaining about the cats rattling. This was at 9k miles. Car had 19k when I got it. Maybe they are like the valve guides? Some just break up, others are fine. But I have also been told that the new OEM replacements are metalic core. Prices really vary on OEM cats. Ricambi wants $4300 for both, T Rutlands wants $7100, and why is the RH cat more than the LH? Perhaps Ricambi still has ceramic OEMs and TR has the metalic cores?

As for emissions, I was actually surprised how clean these cars run when correctly tuned. As I said, my car failed emissions because of hollow cats. But only because it was barely over the limit on CO; 0.50% when the limit was 0.46%. Might have passed on another day.