Hyperflow Cats = Slow Down Light on 348?

You may just need to clean the thermo couples. Mine had some warning light issues many years ago...I cleaned them up and never had a problem again.

 

Check if your cat ECU's have a black or green epoxy backing. I'll bet they're cracked and moisture has toasted them.

 

I had the same problem, try this:
http://www.ferrarichat.com/forum/showthread.php?t=161729

 

That happened to me last year.

 

Since you say this problem started happening *only* after having installed the new parts, it sounds to me like the person who installed the Hyper-Flow catalysts and new muffler mishandled the thermocouples.

Since I cannot be anywhere near 100% on that conclusion, I will give you a brief speech regarding this issue as a whole.

Hyper-Flow catalytic converters will *not* CAUSE your Slow-Down lights to come on. The Slow-Down lights come on for other reasons.

The Slow-Down light will either come on because the catalyst is too hot or because a sensor or ECU is defective. But the catalyst being too hot will not be the fault of the Hyper-Flow cat -- something else will be to blame. More ahead on this.

During the installation of the catalysts, care needs to be taken to ensure that the thermocouples are protected. The thermocouples are very delicate items. A little mishandling will break these $400 babies. They are the temperature sensors that plug into the cat, and they communicate the temperature of the cat to the catalyzer ECU (also known as thermocouple ECU or exhaust ECU). If they are mishandled, they can break; and then the catalyzer ECUs will get false information from the thermocouple. In such a case, you could get Slow-Down lights even though your cat is not overheating. The same could occur if the thermocouples are defective due to age, cracking, etc. People have already posted what might cause the thermocouples to become defective.

A defective catalyzer ECU could also cause a Slow-Down light to come on.

Now the case in which you would have a real problem: the catalyst is overheating. Whenever a Slow-Down light comes on, do what the light says and slow down. Check the cats in the back -- just lift the engine decklid and look down. Pray that you will not see the cats glowing red. Obviously they are overheating if they are glowing. (And even if they are not glowing, don't assume everything is okay.) But what will cause them to overheat?

A bad oxygen sensor (which also plugs into the cat) can cause the fuel mixture to become too rich, and this could in turn overwork the cat, causing it to overheat. Interestingly enough, the fuel can be much too rich even if the oxygen sensors are in good shape (I'm actually dealing with that problem myself at the moment). A more qualified expert can give you more details as to what may cause a cat to overheat, but the main point is that Hyper-Flow cats are designed to run cooler than the factory cats and are not going to fail if the car is running properly. They *will* fail if they are overworked, just as most things will fail if they are overworked.

Here's a tip: if the car is cold, and the Slow-Down light comes on, you know the error is fake -- because it takes time for the cats to warm up and overheat.

So Hyper-Flow cats *are* perfectly "compatible" with your car. The car has to be running right in the first place, and all the sensors have to be in good shape, in order to ensure no Slow-Down lights once the Hyper-Flows are installed.

Oh and *never* disconnect any sensors that have to do with the catalysts. Do not disconnect the catalyzer ECUs regardless of what someone might say to the contrary. As a good friend once told me (wink JRR), disconnecting the catlyzer ECUs is like emptying out your fire extinguisher and then putting it back on the wall. Or even better, it's like removing the batteries from your smoke detector and then putting it back up on the ceiling.

 

Hey no problem. Erratic idle could be throttle position sensor, air-flow sensor, oxygen sensor, lambda (oxygen) regulation, stroke senor, etc. I'm sure your tech will figure it out. I don't think the thermocouple, which is a temperature sensor, will affect the idle the way you describe.

 

+1. Check your plugs. A lot of the early issues I had with my car were resolved simply by changing the plugs. Go figure!

 

There are currently 5 x F355s with Tubi-mufflers and some with Hyperflows in the Seattle area that are turning on "Slow-Down" lights and ultimately CELs. I've had two new sets of Hyperflo0ws on my car and shortly after installation, they turned on "Slow-Down" lights because they were overheating the Hyperflows. What happens is the Hyperflow CAT is so efficient at burning unburnt fuel when they are brand new, the temperature in the CAT exceeds the main ECU limits. What we are beginning to conclude is that the effective exhaust area with Hyperflow CATs and with Tubi exhaust, confuses the Main ECU as to the correct airfuel ratio when the main ECU is under the control of the O2 sensors. We believe the Main ECU trys to compensate for the apparent "low fuel-air ratio" and wants to "rich" the mix to compensate for the over area exhaust. This rich mixture is being burned by the Hyperflows and causing the over temp.

Both new sets of Hyperflows have developed purple burned marks over most of their surface. You should check your Hyperflows for purple marks. If they are developing, you have a Main ECU that is being fooled by the exhaust system into thinking the engine is running too lean and is over richening the engine. This primarily occurs at idle and on decel. Its so bad in my car that I get pops in the exhaust. Ferrari of Seattle is currently running a baseline with the factory muffler and exhaust on my car with new rebuilt OEM CATS as a guenea pig - to test this theory. So far they have proven this theory is correct. I am currently developing a set of choke washers to rematch the exhaust of the Hyperflow-Tubi combination to the OEM area. If successful, I'll give of the added low power improvement of the sport exhaust but still retain the sound quality of the Tubi Hyperflow combination.

 

Very, very interesting post.

Actually, a highly respected Ferrari technician from this board told me the following:

"One thing many people do not know is that the motor should run perfectly without the O2's. Their only function is to make MINOR corrections to the fuel mixture, a little leaner or a little richer under various circumstances from the baseline settings. Any more than that and all they are doing is compensating for another problem."

Have you tried running the affected cars without the oxygen sensors?

I must add an asterisk to your post, however: I have had a Tubi and Hyper-Flow catalytic converters on my 348 for almost a year now, and I have had no problems.

Regards,
David

 

The 348 (OBD I) only has the single pre-cat O2 sensor unlike the 355 (OBD II) that has a post cat sensor as well. So you should not have the same problem as mentioned above.

As an aside, I put bypass pipes on and when removing one of the thermocoupler temp sensors I damaged it. I in a sense wired the two ends together and the slow down lights don't come on. The car runs perfectly fine.

If the sensor is damaged the slow down light will come on as soon as you start it. It may be a defective cat if only one side or your old cats may have been used up and not over heating if you are running rich.

 

Another reason I say the '95s are the year to get for a 355. OBD1 baby!

 

+1 (well, the 1997 Challenge models ran M2.7, too)

There was not a great leap in extra computing power from M2.7 (OBDI) to M5.2 (OBD2), but the poor M5.2 has to monitor post-cat O2's and a host of other sensors/parameters (e.g. intake air temp besides MAF) in addition to what the M2.7 OBDI systems measure...


...which suggests to me that the M5.2 can't be as responsively fast, timewise, as can the M2.7 because M5.2 is doing a lot more work than just monitoring basic air/fuel and a couple of temp sensors.

 

Did the 5.2 have faster clock speeds?

 

I drove it 3 times in each case before the Slow Down Light started flashing upon start up the 4th time. Its like the ECU saw it was getting hot but didn't turn on the light right away to avoid a false indication of overheat. I could also turn out the flashing slow down light by driving fast enough so the engine was running clean enough to burn all the fuel that it was fed and no input was being taken from the o2 sensors. Its still a bit of a mistery. Over time the Hyperflows seems to get damaged enough that they no longer generate enough heat to turn on the Slow Down Lights, so there is a Honeymoon period until they get so bad that the O2 sensors being unable to control emissions turn on the CEL for a "Weak CAT" code.

 

Have you tried running the car with the pre- and post-cat oxygen sensors disconnected?

The car should run perfectly fine with the o2 sensors disconnected. If it doesn't, there is another problem causing the problems you are having.

 

How does the car calculate Fuel Air ratio with the O2 sensors disconnected? further with the O2s disconnected doesn't that turn on the CEL? - the Ferrari Dealer may have done this but I haven't. Interested to hear your response.

 

I will paraphrase the words of our expert friend, who frequents the other place. I have a discussion there if you are interested further.

Basically, the o2 sensors serve only to make minor adjustments to the fuel mixture; the engine should run fine without them. It is possible that the o2 sensors themselves are overcompensating for an underlying problem, thereby causing another problem. In other words, the ballpark proper fuel mixture should be in place without the o2 sensors. Analysis of the exhaust should first be done with the o2 sensors disconnected. With the o2 sensors connected, an underlying problem may be masked.

As for Check engine lights, we don't really care about those while we are in the shop doing diagnostics, right?

 

HYPERFLOW Striks again!!!!!!!!!!!!!!!!!!!