common guys, lets hear some responses to this. This concerns everyone with stock y-pipe setup.
No responce from anyone, strange... This is something new at least to me, doesnt anyone have anything to say. Maybe you are all in you garage putting original cats back and reconnecting your bypass valves ;-)
Well so far thats two of you asking for responses and yet you have not given an opinion your self regarding what the Capristo team have said. As far as i am concerned there's not much that can be said after what Capristo team have said. Or may be no ones attempting to give any opinions because the forum experts will be along to knock them down. Dont flame me that's mostly what i read on FC.
Gas flows in exhaust systems must be an extremely complicated subject; throw in a by-pass system (which can be anywhere in the range between fully open and fully shut) and it must get even more so. I have a computer and I am no expert, but in the hope that more knowledgeable people will give their opinion on this very interesting subject, I'll chance a remark: If I understand the capristo post correctly, their case rests on the premise that negative pressure is created in the main cat converter by the exhaust gases being diverted to the by-pass route. My remark is hugely simplistic because all pressures are relative to pressure somewhere else. However, the main cat converter is open to the atmosphere all the time (through the muffler)...............Someone just has to say the words "back pressure" to have us thinking that our engines are getting strangled and overheated. So, is sufficient (relative) negative pressure developed in the main cat? One would hope that the designers of the stock muffler looked at operational gas flows in their design at least as attentively as capristo. Right, let's see if these amateur remarks stir some action.
Has anyone seen the details on the new Tubi F355 Evolution exhaust? It appears to solve this issue by allowing the bypassed exhaust to take a seperate route through the muffler and directly out through the inner set of tail pipes, thus not suffering from this reversion process. http://www.scuderiasystems.com/prod-special-tubi355evo.html
Ciao f355spider, this system, we have since 2002 in all of our exhaust from the 355, and we have never built a system like the others, to protect the Headers Today is a new exhaust system on the market, why so late? it is a system which we have since 2002. I must say: that is the back pressure problem is not eliminated, this system only helps that everything is cool. the back pressure problem is eliminated with our racing exhaust, because two exhaust valves are installed. I think in future there are more manufacturers, the bivalve version offering, perhaps the name is then "bivalve evolution" . I hope you understand my English! I no! Ciao Antonio
True i know that, i have had one of your systems on my 355 for 7 years since 2003. Its still perfect and the best money i have spent on my Ferrari. Heres the Capristo open day video. It shows some of the manufacturing proses that you will find interesting. http://www.youtube.com/watch?v=Yngq0bOfm4I love Capristo
One of the best threads I've read and definitely convinced me of the "open bypass" valve issue. I'll be keeping mine installed and operational going forward.
One of the things holding me back from geting a twin valve system is that I am under the impression that it will take away the F1 screem. I have heard the Tubi system and I dont like that sound at all. The standard capristo is the sound I want in my next system. Anyone that can confirm or deny that the twin-valve system kills the screem?
You're not alone. I too feel that the twin-valve system lacks the trade mark high rpm F1 screams of the original Capristo.
Ciao a tutti! that's right! the 355 has the most beautiful Ferrari Sound! Unfortunately .... This beautiful F1 sound is produced by the high back pressure in the bypass, with racing exhaust you have the high back pressure any more, and for that reason sounds like a CS. But performance has been much more, but I think that the F1 sound is more emotion than 22 hp more. This sound from the standard Capristo, has had a big success. I'm looking for pictures that we have made where the gas flow was analyzed, and then I let Martin or Andrea Taurino what to write so you can understand better .. Ciao Antonio
Hi there if there is any more information needed there is Capristo USA that can be contacted in the us that stocks and distributes the Capristo range of products on www.capristoexhaust.us
Thank you Antonio, I understand you completely, so the Capristo designs for the F355 have had this design concept all along, and Tubi is only now responding....Got it! And you have further refined the design with the bi-valve design.
Hello all together, I promised you to send some pictures, Apart from the pictures we put a video on YouTube where a 355 is displayed with a sports exhaust of another manufacturer. Then we introduced the prototype of the 355 Racing at that time. Both were tested and compared. Those which were regularly manufactured later on had been improved. Between our racing system and the sports exhaust systems of other manufacturer there has been a difference of 20 HP. Please carefully watch the video. It is displayed how the back pressure is increasing from zero and then suddenly reaches the minus range. That means from neutral to positive and then again to negative. http://www.youtube.com/watch?v=WAbSBDeOrYA I have made a picture of the chart where we have aggressively accelerated the 355 on the Dynojet. On the picture you can see how the pressure is increasing and the it goes into the negative range once the exhaust gas valve opens. That's something I did several times in a row and you can always see that it reaches the positive range and then again in the negative range. As a comparison I have enclosed a picture of the 360 Modena which does not have the bypass problem. Please pay attention to the flow and you can recognize every gear. All the values remain in the positive range and the back pressure is not so high like the one of the 355. When we develop an exhaust system we always make probes on the complete exhaust system and we analyze how the exhaust gas flow is. It may be that the exhaus gases flow different than one supposes. We have also tested headers of other companies because it was told that they should provide additional power but the results were a disappointment for us. It is sad that there have been customers having built in sports headers and they noticed that the torque was lower in the lower range. Then it was told to them that these headers would provide additional performance at higher rpm, but not at lower rpm. It is a matter of fact if the header does not work in the lower rpm range, that it will also not work at higher rpm. The best headers which I tested have been the original headers. Just as often as sports catalytic converters were sold to 355 owners because they should allegibly provide more power. But as it is obvious to us in the meantime that they cannot provide more power, because there is no exhaust gas flow apart from the exhaust gases being aspirated. I believe that I have now mixed up some theories. We hope that some comments are made by some people. Ciao Antonio. Image Unavailable, Please Login Image Unavailable, Please Login
Andrea, Antonio- You have proven what at least one of the pros here, Brian Crall, has been saying all along. Running a stock 355 exhaust with the bypass valve open all the time can result in damage to the combustion chamber components. Great job. The exhaust systems you build are not only beautiful, but well engineered and innovative, especially so the available remote controls . Taz Terry Phillips
Here are some interesting pics of my y-pipe. This pipe was removed and replaced with a used one. The main reason for replacing it was the broken flange. Please note the scalding on the LHS of the y-pipe. I believe my car has had the bypass valve wired open for a long time, possibly more than 5 years. I have now fitted a capristo bypass valve with a remote control kit to keep the valve open. I prefer the valve open full time because it sounds better and goes better. Also, when the valve is open fulltime, i hear this wonderful 'popping' sound when i back off the throttle at around 2500 rpm. Sounds beautiful, especially with the spider top down. I've driven the car with the valve closed (full time) and open full time, and i can certainly say the car goes much faster with the valve open full time. Therefore, the backpressure must be less with the bypass valve open than closed - don't have to be Einsten to work that out. It follows that some exhaust gas must still be passing out the main cats when the bypass valve opens, otherwise the backpressure would be more with the bypass valve open. Anyway, now that i have a remote control bypass valve, i will continue to drive my car with the valve fully open, most of the time, because it simply sounds and goes better. BTW, i have a tubi muffler (old style one). Image Unavailable, Please Login Image Unavailable, Please Login
OMG........now that makes alot of sense...buy a $1000 bypass valve so you can run it open???????????????????? A $5 piece of pipe will accomplish the same thing!!!! For alot of you guys I guess you think Ferrari had a bunch of bypass valves they needed to get rid of so they tossed a coin and decided to put it on the 355...and your fix is to wire it open???... Maybe Ferrari needed to have included a coat-hanger in the tool box
Ciao I think that you destroy your header, if your exhaust valve is open then you suck back the hot gases and they are always hot. with our exhaust system, since you have a separate chamber, cold air is mixed with hot exhaust gases, and everything stays cooler. at 355, I would advise against a remote control, I would only be used with two-chamber Exhaust. Antonio
OK, so now i've been told - i will run my bypass in OEM mode so that i preserve the Ferrari headers. But every now and then, on cool days, i will run the bypass open full time when the 'boy racer' in me comes out!
So does this remote controlled bypass valve has only two positions? Either full open or full closed? Or does it work like the OEM valve which opens at about 4000rpm also?
the remote control bypass incorporates another solenoid valve which shuts off vacuum when its switched on. This keeps the bypass valve open full time. When switched off, the bypass reverts back to OEM setting, i.e. opens after 2800 rpm. However, if the vacuum tubes to the solenoid valves are not installed correctly, you can inadvertently have the bypass valve either fully closed (all the time) or fully open (all the time). I have done this!
