I've noticed that I'm not entirely liking the bypass valve operation at moderate part throttle driving. There's a significant sound change when the valve opens on the Capristo (especially with no secondary cats). Sooo, it's roll on the throttle, valve opens but as you grab the next gear there's a moment when the valve closes and opens back up again so it goes quiet for a split second on gear change. Again, I'm not talking about banging gears at wide open throttle but just spirited driving without super fast shifts. I think the way I'm going to try to "fix" this is by putting a time delay relay between the factory bypass valve wiring and solenoid, so if activated there would be a minimum time the valve stayed open. I'm thinking even 1-2 seconds would be good. This way, at moderate throttle, the valve would just stay open on gear changes instead of going through that quick close/re-open stage. Anyone else notice this/feel the same or do you like it as-is?
Yes. I've commented on this before. http://www.ferrarichat.com/forum/348-355-sponsored-bradan/459361-bypass-valve-removal-4.html "The Capristo 3 has a Jekyll and Hyde personality with the bypass valve functioning. Very quiet and Mercedes like when the valve is closed. And then it turns into full-on F1 Honda McLaren status when the valve opens. Because the valve opened based on a certain set of parameters, there was too much stuttering between sound and feel because the exhaust didn't know what personality to take. With the bypass wired open, the F1 sound can now be smoothly modulated and you can still drive it a quiet manner."
Yes, the bypass can seem to open unnecessarily ...... at one point I was going to put a tiny flow restriction in the vacuum line .... this would cause the action to be more gradual on open and close ........ or ....... you can get a twin bypass exhaust ..... then the same vacuum line has to open two actuators ... so it takes about half a second longer to open .......
I was thinking about putting 2 electronic bypass valve's on my 348 Tubi, wondering how it would sound. Have searched for it, but haven't found anything about it, so not sure if it has been done before.
That is a good idea. I was just talking to one of the great 348 owners on here about something very similar ....... basically the same twin bypass "Dr.Jeckle & Mr. Hyde" exhaust I have created for the 355 ...... but designed to fit the 348 ......
Bah, more plumbing and more heat in the 348 engine bay. CV boot heat death is a 355 ailment. Stop trying to make in ours too!
Too late Vince, your 348 already has 355 wheels ..... you have now reached the slippery slope ..... no use in stopping now ......
Time delay relay sounds like a good idea in your case. Wonder if this will throw on any check engine lights on a 5.2 car. I think the Motronic knows at what parameters the valve is supposed to be open and it will know if it's not open during the time it is supposed to be open.
I thought about that on a 5.2. Don't think it would be a problem if the delay was only a second or 2 but only one way to find out.
On a 5.2 Motronic, that will throw a CE light for sure. The Motronic monitors the bypass valve operation via the thermoprobe just past it. It is expecting a certain temperature range to confirm the valve is open when required, and closed when required. If forced open constantly, then you get a CE light. There is a way to spoof the Motronic, and get around this...Ferrari of Seattle did it as an experiment...but they found other issues. When on constant bypass, so little exhaust is going through the main catalysts, and pre cat O2 sensors, it messes with the short and long term fuel trims. The solution would be to move the pre catalyst O2 sensors to the merge collector on the exhaust manifolds. FoS ended up stopping and just put things back.
I would agree, I really doubt a couple second delay would amount to anything significant to trip a CE light...but only one way to know for sure Great idea, please post the results.
I really tend to think this is not a good idea. Once you start confusing the Motronic, who know if it will train itself to recognize parameters that are out of proper range. Who knows what engine damage could result long term. Naturally if you're experience problems down the road, a mechanic will blame the problems on the experiment and thereby justify any significant repairs. Mr. Capristo himself might be able to best answer this question. Seriously. He did extensive research on the bypass valve situation.
There are guys who have the bypass deleted/wired open. I highly doubt delaying valve closing by one second is going to confuse anything but I will find out.
I run with it permanently open. Sounds amazing and have had zero issues in 6 months. Put the challenge car valve delete coupler in and problem permanently solved.
1999 355 F1 with 13K miles. Has been COMPLETELY restored mechanically including F1 System upgrade. I started running with exhaust by pass valve wired open because it rattled otherwise. Ferrari tech that works on my car built 355 challenge cars and they had the delete bypass valve adapter. I have one I am waiting to put in when I upgrade my headers.
How are you dealing with the fuel trim issue and "check engine" lights they will cause? Understand the emissions system is completely different on a street 355 versus on a Challenge 355. The Motronic will throw a CE light, unless someone simply disabled the light, or you are ignoring it. Regardless, unless you move the pre catalyst O2 sensors to the exhaust manifold merge collectors those fuel trim issues will likely cause problems long term...to what extent is unknown, but you will be the one to tell us. See my previous post in this thread on the research Ferrari of Seattle did with my car to see what was happening with the 5.2 Motronic on constant bypass.
I have had NO fuel trim issues. The car idles and runs great. I have had the engine parameters checked about every 3-4 months and all are normal. Compression since major service is spot on in every cylinder. You are correct. Running with the exhaust bypass valve open causes the Check Engine Light to come on ... I have the car registered where I do not need emission inspections, so I simply ignore it. I have seen a fair amount of debate on this subject. All info I have received from Ferrari techs and other owners indicates no long term issues running with the valve open, or deleted..... no question the car sounds better at start up and low RPMs with it open. The stock bypass valves are known to develop a rattle you simply cannot get rid of. In my case the rattle was the motivating factor to wire it open.
Capristo makes a reliable replacement that does not rattle. I used it on my car, worked great for many years. Sold the car last year, I assume it continues to give good service. A friend of mine knows how to repair the stock bypass valve to remove the rattle. It takes some trial and error, but he did it on his own car successfully. Helps that he is an engineer with a manufacturing concern, so he has several CNC machines, mills and lathes at his disposal... If you are not having fuel trim issues, good for you. I would continue to scan for codes periodically, just to be certain it does not crop up. In fact I highly recommend you purchase a code scanner of your own (they are very inexpensive) and check them yourself, just to be absolutely certain your technician is not hiding something from you. As I stated, Ferrari of Seattle did extensive testing of my car with the valve open constantly and found fuel trim issues. I drove with the valve open for one afternoon and confirmed I had short term fuel trim codes pending...along with the code for the valve being open.
Was aware of alternative By Pass Valve. Ferrari checks codes for me regularly as they have done all work for me on this car. I typically read the codes with the Tech, but good suggestion to get my own code scanner.... Am going to do.
