F355 with no cats..

Anyone running a 5.2 with no cats?

Just curious..

 

I'd prefer to run 100 cell cats. Minimal interference, still legal, and your car won't smell terrible.

 

no cats.. I assume you mean test pipes..

there are guys running test pipes on their 5.2 cars..
but requires for sure O2 spacers..

hopefully the new O2 spacers by Fabspeed with mini-cats built in can finally offer a real solution for 5.2 owners to run tests pipes without CELs..

and it is something that I am considering now..

 

I am

 

The 97 I just ran for 4 years had factory cats that were hollowed out with the cores removed. No O2 spacers and never once had a CEL, but from what I gathered on the car and CAT codes had been tuned out of the ECU.

 

I am. Test pipes. I have a constant CEL and I just live with it. Yesterday I put in 90 degree angled 02 sensor spacers (with steel wool inserted). Haven't yet cleared codes and taken it out for drives to see if the spacers/wool keep the CEL at bay. Some people have had luck with this setup so I figured it was worth $30 to give it a shot.

Very interested in the Fabspeed 02 spacers with mini cats built in (I started the other thread on that topic).

Love the sound of straight pipes (and not worrying about heat as much) but I've been having to swap out to cats once a year to pass inspection. PITA. So I want a solution that keeps the CEL away yet keeps the straight pipes in year round.

 

report back please if the steel wool works to keep the cel off.

looking back at the new fabspeed mini cat spacers.
I naturally assumed it was $161 a pair.
but now realize it's Each! so that's pretty pricy!

given you can get a pair of spacers for $50
and just stuff with steel wool.

which to my understand EricC has done and hasn't had any Cel triggers since installing test pipes.

the mystery is how the effectiveness seems random??
some 5.2 cars run fine with test pipes + spacers, while others still get codes.
even moreover some 5.2 cars are still tripping codes even with high flow cats with and without spacers.

This is what puzzles me.

 

Look at the link I posted in that thread for big daddies mini cats. $49 each.

Those were suggested to me by well respected tech.

 

I have the 90's with wool. I've never had a CEL come on. Just a random SDL that always turns itself off.

 

yes I saw those and they look good. and well priced.
only concern is they are straight.
hopefully doesn't cause a clearence issue.
i read in another post you're running evoflow cats.
are you getting cel even with those without spacers?

 

you're random SDL is a flashing?
it's interesting the sdl would trip given the probes should be seeing less heat with the test pipes.

I used to get a random flashing SDL when I had my bypass valve temporarily wired opened.
even with stock cats on.
at random it would flash and then eventually turn off.
this was done for testing purposes.
once we got the bp valve functional I have not had flashing sdl since.

 

I have hyperflows and a cel I've ignored since last year that I want to try and eliminate. I've cleared it twice and its come back after awhile.

I checked for fitment and there is room for the straight design. I may have to rotate one of the cats a tad to ckear a frame member but it's not an issue c

 

only 2 times seems reasonable. but still a high flow cat in general should not trip any codes.

while on the subject and because i am seriously considering putting test pipes on my 5.2 car with mini cat spacers.

I might try to undertake the swap myself.
can it be done without removing bumper?
I assume the diffusers need to be removed.
also is anything different needed, or are all existing parts reused?

 

They are cat inefficiency codes and by altering the cats as in aftermarket versions you are potentially changing what the post cat sensors are telling the motronics. The values it is looking for are not bring met and thus the CEL.

I didn't have it for awhile and then it popped up. For $100 total I'm willing to try and fake out the Ecu.

 

I have a 1996 Spider and have had OEM cats for a while, a resonator type test pipe and currently Fabspeed straight test pipes on my car. In all cases, I have had a right angle empty pipe extender to keep the secondary O2 sensor out of the exhaust stream. One was home made and the other currently is Fabspeed's original empty bent pipe. I have never had a CEL in any scenario. However, I have no thermocouples either. Instead, all have been replaced by new circuits that send a normal temperature range signal to the ECU, I emphasize the word "normal".

Test pipes are not going to overheat but they will certainly be cooler than a cat. My understanding is the thermocouple ECU has to receive a signal WITHIN a normal range. Not too hot but also not too cool. If too hot, you get an SDL indicating an overheating cat. Too cool? I don't think you get an SDL but you may get a CEL since this would normally indicate an underperforming cat. Could this be what some of you are experiencing?

 

In my case Jerry, not a sdl issue. But a post cat o2 sensor issue.

As far as sdl is concerned, the motronics is looking for a voltage range in order to stay happy. I currently have installed three after market sdecu that I modified to fit our inputs and outputs. I can monitor the voltage outputs on these real time and they start out cold with a .2v signal that triggers a sdl. As the cats warm up it goes away above .5v. The OEM sdecu starts out at .5v which makes the motronics happy. The OEM sdecu puts out a line voltage of .5v when it is working properly.

If you have a cold cat and a working sdecu, you shouldn't get a sdl. In monitoring my sdecu s real time while driving, with OEM sdecu installed and a sdl issue, the sdl was triggered by a voltage spike over 3v as a result of a defective thermocouple. I would imagine that a defective OEM sdecu could do the same thing. An intermittent sdl is most likely a short somewhere.

 

for those who are running test pipes.

is the smell really that bad etc?

 

It can be in traffic. Though that's usually for folks behind you more than you in the car.

 

I had my 5.2 running with empty cats and no cel, and no horrible exhaust smell.
it smells as a car is supposed to smell.
all o2 sensors connected. I only had once that the engine management cut off a complete cylinder bank. probably because the o2 sensor voltages where jumping up and down permanently

 

^^^^ This ^^^^

I was behind a P car with test pipes on a fall drive and my eyes were burning and I was getting sick from the fumes. But ,I will say, when I got my 3rd 355 last summer (95 with test pipes) it is not as bad as the P car was but I've also not been the guy behind me

 

Bob, When you use the term "sdecu", what does the sd stand for? Is this for the thermocouples?

Correct me if I'm wrong but my understanding is the post cat O2 sensor's purpose is to monitor the condition of the cat. Whether the cat is conditioning the exhaust properly or not, unless it overheats (which is the thermocouple's issue to monitor, not the O2 sensor), there is no danger. Its merely a below par poorly functioning cat (CEL) or its working as it should (no CEL). The post cat O2 sensor will not cause the motronics to generate an SDL, only CEL's since there is no eminent danger. However, if the cat should overheat, there could be danger and this is sensed by the thermocouple and an SDL is generated. If the overheat persists or gets worse, the thermocouple will not only generate the SDL but could shut down the offending engine bank to prevent a possible fire (so called limp mode).

So, if I understand this correctly, SDL's (or an actual limp mode) are generated by the thermocouples, not by the post cat O2 sensors. Am I missing something?

 

Hey Jerry,

"SDECU" = Slow Down Electronic Control Unit. I tend to call them TCU's

O2 sensors have nothing to do with the CAT protection system, which generates SDL's to warn of excessive CAT temps.

 

That is correct. My 5.2 has straight (test) pipes and a Capristo without the third bung (post bypass valve).

It has all 3 thermocouples installed, but the one that should go into the exhaust bung post bypass is simply tied down off to one side since I have no bung for it to go in.
I used to get a CEL before I put in the 3rd thermocouple because the system expected it to at least be there. I got one from DrBob and mounted it off to the side and that CEL went away.

I never get SDLs.

When I have the OEM cats in place of the straight pipes (for inspections each year) I get no CELs (and no SDLs).
When I have the test pipes in, I get no thermocouple-related CELs, only one for each cat (below efficiency threshold... can't remember the number, you can look it up), but never any SDLs.

So essentially, the system does not seem to care about TC temps with test pipes since the only CELs I get with them are cat-related. I never get any CELs that are TC-related whether I'm running cats or test pipes... and again, I never get SDLs either way. As long as the TCs are in place and functioning properly, test pipes or cats makes no difference... at least on my car.

And the exhaust smell is slightly more pungent when I'm running test pipes, but not enough to negate the better howl from the Capristo and the comfort of knowing the bay is running cooler. I only notice it when I first back out of the garage... the rest of the time it's way behind me. I never really notice it when sitting in traffic, at lights, etc. After a while it's kind of nice... because it means I'm in the red car.

 

You've got it Jerry.

SDECU ( slow down Ecu) refers to the Viscovini voltage transmitters . The little black boxes for the thermocouples . I believe was an acronym FBB coined. Works for me.

To Jeffs point about getting an sdl with no TC in place is understood because from what I saw on bench testing, unplugging the TC made the sdecu send a 5v signal. Having the TC in place allows voltages that are in range.

PS. Got a radio ��

 

If you can do basic wrench turning, you can swap them yourself. I do it solo every year, and then go back again after inspection... so I've done it half a dozen times.

Yes, the bottom 2 diffuser panels have to be removed. I also remove the rear wheels to allow more access. You do not have to remove the bumper. I do not have to remove my muffler either, but I have a Capristo... I can't speak to OEM or other brands of exhaust for sure, but I assume they can stay in place as well. I just have to loosen the bolts on my Cappy at the top to allow it a little play for getting pipe ends in and out of it at the bottom.

I remove the air box (I have a 5.2 with a Gruppe M) and heat shield to allow access to the exhaust system from the top. All easily done with standard wrenches/screwdrivers.

It also seems easier to unplug the O2 sensors from the opposite end (where they plug into the ECUs) instead of trying to unscrew them directly from the cats before removal. It's easier to get them out with the entire cat removed and twisting the wires when they are still plugged in at the ECU end can stress break them at the O2 sensor end.

I reuse just about everything, but you'll probably want to swap out your exhaust gaskets with a fresh pair (#22 in this diagram):
EXHAUST SYSTEM - Ricambi America, Inc.

You might also need to swap out the bolts/nuts/springs that attach the cat/test pipe to the header (#23-#27 on the diagram above.. plus #29, #30, #32 and #33 for where the cat meets the muffler) as they become corroded over time from the heat. People sometimes break them trying to get them apart if they haven't been removed in years or weren't prepared properly during the last install.

Which brings the last bit of advice... get some Anti-seize:Amazon.com: Permatex 77134 Nickel Anti-Seize Lubricant, .5 oz Tube: Automotive
It'll make life easier down the road if you have to pull the pieces apart again (they *will* have to come apart again some day... even for other work being done on other parts of the engine). The reason people often break exhaust hardware is because it wasn't prepped with anti-seize the last time it was installed, so do yourself a favor and put it on as you put things back together.

That may seem like a lot of info, but it's really an easy swap. I actually have a set of steps/tools written out that I keep meaning to type up "Dave Rocks" style ... I just haven't gotten to it.