yet another exhaust mod/bypass valve thread ;)

Neil - given your car is OBDII, you will get a CEL if you mess with the bypass operation.

Like my car with no muffler, I still have an operational bypass valve.

As to the removal of CAT's....In general, I'm not a fan (for sake of the drivers behind me) but on the other hand, CAT's can be a source of problems....

 

I'm running Fabspeed test pipes + Fabspeed catted o2 extenders, tubi exhaust with the forza exhaust bypass controller.

No CEL's yet. Sounds great and doesn't smell as awful as I was expecting. I've owned cars that smelt much worse.

 

I removed the cats because of the amount of heat they create in the engine bay. I've toasted engine mounts and since my car is an F1 the less heat hitting the F1 system the better.

If Ferrari had the option of shipping cars without catalytic converters they would take that route to this day.

 

Someone else with a challenge car can correct me if they think I am wrong but even the challenges get super hot without cats. I think both Tim and Robbs cars have no cats and they dont stay any cooler that mine but that is on ththe track. Maybe in town would be differant.

I have never seen a car whose engine bay gets as hot as these. Frankly I am supprised we dont have more problems with components and wiring.

 

Get out at a stop light and ask the car behind you

 

The 95 I sold had test pipes. Engine bay got scorching hot. Never measured temp to compare.

 

Personally I would do it the other way but to each their own. Its your car but again I would rather it be quieter on mains and louder on bypass but thats just me.

 

even when the bypass opens.. exhaust still passes through the primary cats..
at the outlet of the headers.. theres nothing to control where the exhaust goes, up or down..

the bypass is simply meant to open up the exhaust flow at higher rpms..

I can say first hand... as ive already experiment with 6 different exhaust configurations..

empty cats or straight pipes completely changes the sound of car.. in all conditions, bypass closed, open, idle, cruising etc.. even with the stock ypipe..

ive been chasing my preferred exhaust note since ive owned the car.. and have finally settled with:

Fabspeed headers, Fabspeed test pipes +mini cat spacers, Nouvalari SS, stock ypipe.

until I can find a cheap aftermarket y-pipe, I will leave as is for now..

 

I agree, the engine bay gets very hot with or without cats. But I can tell you for certain, it gets significantly less hot without cats. I've had it both ways.

Another reason the engine bay gets hot is because there is no belt driven fan running all the time to push air through the bay to remove the hot air. Granted, when the car is moving, air flows through the bay, how much depends on how fast you are going. But even then, much of it exits through the wheel wells and not the engine bay. Also, when going slow or in stop and go traffic, there's essentially no air movement. Then, 355's rely on convection up through the lid louvers. Helps but nothing like a constantly running fan.

A solution that has occurred to me is some kind of secondary electric fan synced to run whenever the engine is running, one on each side, that pushes air directly up and across the engine / headers and out the top (and challenge grill if you have one).

Would take a bit of engineering but I think this would make a substantial difference in the bay temp.

 

I have a 360 and I am in the process now of trying to find that ideal exhaust set up

What I've done so far is installed Fabspeed headers and pulled the cats out replacing them with Fabspeed cat test pipes. My silencer is a Ferrari racing muffler. This is the same silencer that's on the 360 CS. I too have the Fabspeed O2 mini-cat extenders to avoid the CEL.

When the exhaust bypass valves are closed it all sounds pretty good and is well attenuated because it's passing through the muffler If I open the exhaust bypass valves there's no sound attenuation. And the problem from my perspective is that the exhaust sound is very raspy to the point of being irritating And it is exceedingly loud If it wasn't so raspy I could live with the loudness I have recently purchased a pair of resonators which I am planning to insert into the cat test pipes. Have to a cut a 12" section out of test pipes and weld in the resonators. My hope is that I can eliminate the raspiness and at the same time provide a bit of attenuation of the sound.

Hope to have resonates done next week.

Steve

 

Probably worth my repeating this:
Ferrari of Seattle did a bunch of testing on my car a few years ago with running a remote bypass switch for the exhaust valve (1997 F355 Spider, 5.2 Motronic). They were able to spoof the Motronic not to throw a Check Engine code for the bypass running open all the time. But a new problem came up. With the car running on bypass constantly, there is very little exhaust running across the pre catalyst O2 sensors. This really messed with the short and long term fuel trims and set off Check Engine codes. The only solution we saw would be to move the pre catalyst O2 sensors to the merge collector of the exhaust manifolds...I elected to just put it back and not use the switch. (though I did have the Capristo bypass valve and Capristo exhaust on my car )