Is your 355 exhaust bypass wired open?..

Yes, mine is open. I replaced it once for a hefty sum, but this time when the brass bushing inside started to wear and rattle, my mechanic just secured it open.

FYI, this does not do any damage to the engine.

 

yes

 

You don't have to remove the bumper at all.

It is an incredibly simple system. use a 3 foot long piece of 7/32 vacuum tubing , and a vacuum pump or local prostitute to check for leaks.

 

It was, but not anymore. I like the more refined sound when the bypass is working properly. Plus the CEL was annoying.

 

Mine is.

Rock n roll . . .

 

I have a switch. It just grounds the solenoid instead if the ECU. I checked, and the ECU didn't care if the switch has a diode or not, so really simple.

 

+1 had mine open CEL 1448 was annoying.

 

Mine is wired open, Love it! Running gutted cats and stock muffler. Sounds awesome!

 

You can wire it open with 'mechanics wire' at the bypass valve itself.

You can use high temperature copper grease to quite a noisy bypass valve.

 

Me too and it sounds (and runs) better than ever, and especially now with 40k on the rebuilt engine, it runs really strong

Wish I knew that earlier, but my modification to the valve is permanent at this point. One day I may just buy a new one, but I kinda like it loud.

 

Why not fix it? Pull back the boots on each of the two connectors to the vacuum solenoid plugs...one is black, the other is blue. Make sure the wires are still attached to the pins. Also, make sure there is no corrosion on the pins. Very likely if the boots are torn, or ripped apart (common problem). The boots and pins are available from Dave Helms at Scuderia Rampante to make a lasting repair.

If that is not it, you may need further diagnostics beyond my ability, but this should not be that big a deal to fix and have working correctly.

 

Dancin' with the devil boys, dancin' with the devil....

There are more than a few threads on here from very well known and respected Ferrari mechanics/manufacturers talking about the issues with wiring the bypass open. I respect these people's opinion/input and it convinced me that it's not a good thing. There's even one thread from Capristo showing the diagram of the backflow it creates.

In my mind it's irrefutable but if you still feel that it's a wise decision after reading those threads then go for it, it's truly your decision!....just make sure you register your car in the 355 registry ;-)

 

I heard one of these fellows mention that a piece of paper can be sucked to the outer tips (main exhaust path) to prove the "back flow". I performed this test and revved through the rpm range slowly and it NEVER tried to 'stick' to either tip, both sides of the engine. I took AFR readings from both sides and both tips on a dyno, the readings were a bit different but not enough to cause a poor running engine, it made exceptional power as well. My car may be the exception but it is running fine with the valve open, no "backflow" here boys.


Pop quiz, what exhaust part is not found on the Ferrari F355 Challenge car? No I'm not talking about catalytic converters.


Rob

 

Um, the exhaust by pass valve...

 

Ding ding ding, we have a winner!

 

funny this thread was started. i just clamped my valve opened for one day and got the 1448 code then the slowdown light. i cleared the code and shut the valve and after a 5 in drive the slowdown light went off. the heat probe must see too much heat open and it gave me the slowdown light. what are you guys doing to keep the slowdown light off? all works good not wired open no cel and no slowdown. the sound was great open. i do agree with that

 

You can't get around the 1448 CEL if you wire open the bypass valve but the slow down light is something else, it could be your thermocouple on top of the exhaust is loose.

 

Go for it boys and let us know how it turns out in the next couple of years! I sincerely hope that the mechanics that work on these cars professionally and the boys at Capristo are all wrong...I really do. BTW, if you want to see what they have to say, search is your friend.

 

Rob, what were the dyno readings with, and without the valve functional? I recall a post here a few years ago from someone at FabSpeed (?) stating they (personally) loved the sound with the valve wired open, but their own testing showed a significant dip in hp and tq below 4000 rpm set up that way. He went back to using the valve. I am unsure if that was with stock or their own headers...I suspect thier headers, if I am recalling the correct poster on the subject.

 

BTW, do a search on that and you'll learn why....

 

I did not run with the valve functioning, just open. We dynoed a '95 with Tubi headers/HF cats, Tubi muffler and functioning bypass on the same night as my '97 with stock exhaust except for Mille Miglia muffler and open bypass. My car made more power throughout with an additional 4 whp on the top end. I will be doing some dyno testing in the future to see whether some new breathing mods (including dual MAFs) are worth producing for the community and I will be sure to do a comparison with and without a functioning valve. I will do some light loads to simulate cruising around since it will give different readings than WOT.

I am not trying to get into an argument with my fellow FChatters so I will rest my case.


Rob

 

Rob, you don't have a Capristo exhaust, right? The backflow test you described should work with a Capristo, but i don't know that any other exhaust system routes the main and bypass exhaust flows to separate tailpipes.

 

Yes, Fabspeed posted here just recently that bypass valve removed resulted in lower torque and power at *all* RPMs on the dyno. I'd find this easier to understand if the power discrepancy were below 4000 RPM only, since the bypass valve should be open above that regardless, but that's what was stated.

 

after the 1 hr drive with it open and the CEL and slowdown light i switched it back to stock for good. if i want it louder cat delete or highflows. BTW there is a thermocoupler on the top exhause after the bypass and i think the only reason the light comes on is if see to much heat not to little heat. so if it was loose that would have no effect. the only thing i was not sure of is that if the top thermo sees to much heat will it throw the slowdown light. does anyone know that answer ? i would think yes because when it cooled down it never came back on. i just wanted to hear the sound if i deleted the cats. i do not think it is a good idea to wire it open all the time.