I read more than a few threads but could not find the final verdict. Does the valve in the open wired position cause any harm to the engine, cats or any other issues? I know about the cel . If yes, does the capristo remote open valve have any designed features to compensate? tks
As a mechanic, I cannot see how it could cause damage. I discussed this with a few other guys at work and cannot seem to come up with a real reason why it would cause any damage, I have heard people say it'll cause exhaust to go back into the engine - none of the things I have heard are real. That being said, I am all ears if anyone can chime in on the topic.
Start reading at post #25. Clear and documented evidence of the back pressure issue. http://www.thebestemployee.com/forum/showthread.php?t=253387&highlight=355+bypass+valve+capristo&page=2
With the Mille Miglia muffler I have on my car it is impossible for the exhaust to "circulate" as my the main path and bypass path never mix once they split at the Y in the end of the header collector. I have not tested the stock muffler but if it mixes in the can then I entertain the concept of circulation but I will not subscribe to it. My conclusion: If the exhaust remains separated after being divided exiting the header you have nothing to fear. This assumes all 02s and other sensors along with fuel pressure regulators/pumps/injectors etc. are functioning as they should. Rob
I am not convinced, there are factory "log" style manifolds (the early NSX is one) that mix and swirl the exhaust and have all kinds of back pressure and the engines do not fail. I would sooner believe that an incorrect AFR would cause the damage described here.
Totally an individual choice so go for it if you choose. We'll all know in a few years whether we were playing chicken little or those of us that believe it causes engine problems will be proven correct. Having said that, the gamble is an expensive one for those that choose to wire the bypass open. If we're right, you're looking at a $20K+ engine rebuild, if we're wrong then you got to to be loud for the low price of a little wire.
Gents, I am only seeking your experienced knowledge and appreciate your help. I do not claim to be an expert. I am just trying to evaluate if in deed there could be damage. I copied the below from Capristo's web site and If I read this correctly, in case of valve failure, their design claims to protect the engine since it fails in the open position ! I just copied and pasted from capristos web site the below: ============================================= This remote controller and key fob set gives you the option of opening your exhaust valves at the touch of a button. The reason to have exhaust back pressure control is to obtain a better engine torque band and to maintain drivabillity in a wide range of conditions. Todays high performance engines prefer a free flowing exhaust at wide throttle openings and high rpm. At smaller throttle openings and low rpm encountered in traffic, a slight increase in exhaust backpressure, results in better low end torque and a more user friendly engine. This pressure is controlled by one or a set of butterfly valves in the exhaust system. These valves are in turn controlled by the engine ecu which would open and close the valves according to a preset set of rules. When using the vehicle on a track or in a sporty environment where it is desirable to keep the valves in an open position, a push of a button on the remote controller makes this possible. This controller interfaces perfectly with your exhaust valve equipped Capristo or OEM exhaust for Ferrari and Lamborghini. An added safety feature is a fail safe condition which allows the exhaust valves to go to the open position in case of electrical or vacuum failure. This prevents engine and or header damage from excessive heat build up. The supplied wiring harness comes with both a long and short reach option. It can also be used for single or dual exhaust valve operation ====================================================
Different problem. The stock bypass defaults to a closed position if it's not functioning which can create another set of issues if you're revving the engine in the 4K+ range. The Capristo defaults to open to prevent damage in the case of a vacuum or bypass failure.
Any one else has experience to explain how capristo allows to have open valve if it is bad for the engine! I emailed them and waiting for their answer too .
You may be misinterpreting why the Capristo valve works the way it does. It has two positions just like the factory valve: Open (exhaust flows through upper Y pipe) and closed (exhaust flows through lower catalysts.) If the Capristo valve fails, it defaults to the open position and bypasses the large, lower catalysts to avoid overheating the catalysts and triggering the slow down light. The valve has still failed and needs to be replaced, but at least you can operate the car normally until you can get it serviced. The factory valve defaults to the closed position so that the slow down light and corresponding reduction in max revs is triggered. This is a done purposely so that the owner will know something has failed and needs to be serviced immediately, and high RPM engine operation is restricted. Basically, the factory took the more conservative approach in their design.
I got back answer from Capristo see below. In summary, it seems that the Capristo muffler is designed differently so as not to reach these critical temperatures/back flow, hence running an open valve will not damage. This is how they are able to supply the user option of the remote control open valve design. Do you read the below the same as I am ? ================================================== That brings us to your second question. the Capristo exhaust you already own eliminates this problem. The flow path through the Capristo does not allow the reverse flow that causes the damage to the exhaust system. On the OEM exhaust the exhaust gases could ,with the valve open, flow back through the catalytic converters and remix this hot gas with new exhaust gas. This cycle would repeat through the Y-pipe and exhaust until temperatures rose to damaging levels. This only occurred in a narrow range of parameters, but the damage is nasty. ===================================================
The thread linked to already by Monteman contains a more detailed explanation by Capristo of this very topic, along with a diagram depicting the exhaust flow. Here is a direct link to that post: http://www.ferrarichat.com/forum/showpost.php?p=139100560&postcount=25 Would you mind posting Capristo's entire response to you?
So to summarize; Leave your bypass valve functioning with a stock muffler or with any muffler that allows bypass and main paths to mix. It sounds as though even when functioning properly the 'circulation' is still a possibility in the high revs. Hmmm.
As I have already said I do not necessarily buy into the theory of the open bypass valve causing engine damage - what specific damage are we even talking about anyway? From what I have read, the recirculation issue exists even on factory cars without mods. If what I am beginning to think is in fact true, it is the AFR and not the exhaust path, or recirculation as it is called that is causing all the troubles here. How does broken or cracked header runners cause cylinder liner wear or damage? I am looking at this from a mechanical standpoint and it just seems that the damage is not consistent with the causes here.
I would recommend reading through some old threads. Search is your friend. There are tons of threads on these topics since they literally come up about every two months (or more). The other ones that come up frequently are do we change the timing belts at 3 years or 5 years and what years or serial numbers are the bad valve guides in. The right thing to do is for us to create a sticky so the frequently asked questions are in one place. Totally your right to disagree with some or all of the issues but I would ask that you read the threads since some very knowledgable and credible people have weighed in on all of these topics and have tons of data and experience to back them up. In a nutshell, the cracked header causes the fuel injection system to overcompensate causing cylinder wash which wears our the liner very quickly. The bypass valve issue causes things to flow upstream and back into the engine. The belt change is a personal choice but most agree to never go beyond 5 years not so much due to the timing belt but due to other issues. There doesn't appear to be any year or VIN number for the valve guides. I would recommend doing search on threads that include input from enginefxr, Dave Helms, Brian Crall and a few others that make a living from Ferrari's. In many cases, they've also developed fixes for many of the problems. As an example, Dave Helms is the man behind the gold connector kit, the hose kit and others that address known issues. All solid experts and I would encourage you to read their threads since they are rock solid. Hope this helps.
^^ Thanks Monteman, that makes a little more sense ( I have used the search feature with mixed results) - the overfueling washing out the rings is a good explanation - all the more reason to have a wideband on the car. The exhaust valve causing exhaust to go back into the engine is particularly not settled for me as I cannot see this - as I said before, there is no difference between that and any engine that uses a "log" style manifold where all the cylinders are mixed anyhow. The timing belt issue I agree, not over 5 years - although people have done it...
