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Manually Controlling the Exhaust Bypass Valves

Discussion in '360/430' started by bisel, Apr 1, 2014.

  1. bisel

    bisel Formula 3
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    #1 bisel, Apr 1, 2014
    Last edited: Apr 1, 2014
    Was talking with my techs about exhaust systems in general and bypass valves in particular and that prompted me to develop a better understanding of the topic.

    I did a bit of research (the Internet is wonderful thing) and found some useful information that I put together and am posting here. Would enjoy getting some comments and feedback.

    Regards,

    Steve
    http://www.forzacomponenti.com/

    ======================================

    Basic Theory


    An automotive exhaust system is designed to evacuate gases from the combustion chamber quickly and efficiently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. An 8 cylinder engine motor will have 8 distinct pulses per complete engine cycle and a 12 cylinder engine will have 12 pulses. As more pulses are produced, the exhaust flow becomes more continuous.

    Back pressure can be loosely defined as the resistance to positive flow - in this case, the resistance to positive flow of the exhaust stream. With any modern engine, there is inherent back pressure within the exhaust system consisting of the exhaust manifold, the catalytic converter, the system muffler (silencer) and the connecting pipes. While one would think that lower back pressure would be better, that is not always the case when designing an exhaust system for a modern engine.

    Automotive exhaust designers produce systems that balance exhaust flow capacity with velocity. The objective is to evacuate the exhaust gases as fast as possible. At lower engine RPM and lower exhaust gas volume, the velocity of the exiting gases is lower. If one could artificially impose a restrictor in the exhaust system that would increase the back pressure, the velocity of the exiting gases will increase and this will improve the evacuation of the gases from the engine. A simple comparison is water flowing from a garden hose. If you let water trickle from an unrestricted hose, the water flow rate (velocity) will be low. If you cover the hose opening with your finger, you will increase backpressure and the flow rate will increase. But, at some point, if you cover the opening of the hose too much, you will have caused so much backpressure that the velocity then declines … eventually to zero.


    Why is Exhaust Velocity Important?

    The faster an exhaust pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The general idea is a fast moving pulse creates a low pressure area behind it. This low pressure area acts as a vacuum and draws along the gas behind it. A similar example would be a vehicle traveling at a high rate of speed on a dusty road. There is a low pressure area immediately behind the moving vehicle - dust particles get sucked into this low pressure area causing it to collect on the back of the vehicle. This is why I mentioned exhaust pulses above. It is because of these pulses in the exhaust combined with velocity that tend to produce this scavenging effect.

    You may have noticed that turbo charged engines tend to have larger exhaust pipes. The reason is simple. Since the turbo is in the exhaust stream, the gas flow spinning the impeller tends to come out of the turbo with pulses greatly diminished, which tend to negate the scavenging effect. So turbo charged cars typically have larger pipes to accommodate gas volume — leaving the turbo to perform the task of scavenging the spent exhaust gases.


    Dealing with Variable Exhaust Flow Rates in Modern Engines

    Automotive engineers design exhaust system taking into account many factors, including the number of cylinders (pulses), the power curve they are seeking and environmental considerations. The maximum scavenging effect is achieved when the exhaust velocity is high and time between pulses. So, when engine RPM is low and the total volume of gases is correspondingly low, the designers typically utilize smaller diameter pipes to create a bit of back pressure. But as engine RPM increases, the volume of gas increases and the time between pulses decrease, which in turn reduces the scavenging effect. Now, back pressure becomes a bad thing. In these conditions larger diameter pipes are appropriate to reduce the backpressure and accommodate the increased volume of gases.

    These variables present a challenge when designing effective engine exhaust systems. At lower engine RPM, the flow rate is low and we want to induce some backpressure to improve engine efficiency and power. While at higher engine RPM, the engine is producing more exhaust gases (higher volume) and we want to reduce backpressure. The trick is to have an exhaust system that will evacuate the gases as quickly as possible (high velocity) at the RPM range that you want your power band located. As discussed above, smaller exhaust pipe diameters are best suited at lower engine RPM when the volume of gases is small. But at higher engine RPM, a smaller exhaust pipe will then create unacceptably high amounts of backpressure and reduce the exhaust velocity when the engine is producing greater volume of gas. This will have a negative effect on power output and engine efficiency. When backpressure is not optimized in the exhaust system, there is a tendency to reduce engine efficiency resulting in decrease in power output and higher fuel consumption.

    To work around the RPM specific nature of pipe diameters and their effect on backpressure, engineers may use setups that have the effect of changing the pipe diameter on the fly. Advanced exhaust systems (e.g., Ferrari, Maserati) have two exhaust paths after the header - at low RPM only one path is open to maintain exhaust velocity, but as RPM climbs and exhaust volume increases, the second path is opened to curb backpressure and improve flow velocity. Since there is greater exhaust volume, there is no loss in flow capacity.


    Exhaust Bypass Valves

    Ferraris and Maseratis (and other vehicles as well) utilize exhaust bypass valves to achieve two distinct flows for the exhaust gases. Generally, the exhaust bypass valves are positioned behind the catalytic converters and before the silencer.

    With the exhaust bypass valve closed, the gases have only one path … through the silencer. This increases backpressure and improves the velocity of the escaping gases through the system resulting in improved power at lower RPMs

    As RPM increases, the vehicle ECU will open the exhaust bypass valve. This can be a progressive opening that occurs over a range of RPM, but generally the opening of the bypass valves occurs immediately when key parameters are achieved (e.g., engine RPM and throttle position). When the bypass valve opens, it presents a second path for escaping exhaust gases that typically “bypasses” the muffler. This has the net effect of reducing the backpressure in response to the increase in flow rate thereby maintaining (or improving) the velocity. In so doing, the engine is more able to achieve higher efficiencies and power at the elevated RPM.


    Manually Controlling the Exhaust Bypass Valves

    If your vehicle comes equipped with exhaust bypass valves and you want to optimize power and engine efficiency for normal driving, you should not employ manual methods for controlling the bypass valves. Let the vehicle’s ECU manage that for you. So, why would you want to manually control the valves? I can only think of two reasons:

    1. You are racing or tracking the vehicle. In these situations you are likely going to be keeping the engine RPM in the higher ranges and your throttle will likely be positioned more open than closed. You want the least restrictive exhaust so you can maximize exhaust gas velocity.

    2. You want to hear the glorious sound from your engine. The immediate effect of an open exhaust bypass valve is to “bypass” the muffler (at least for a portion of the exhaust gases) with the net result of a louder exhaust note.

    More than likely, the only reason one wants to manually control the bypass valves is the latter. You want to make some noise. By manually controlling the bypass valves, you can make that noise any time. And, you can return control of the bypass valves to the vehicle’s ECU when you want to quiet things down … e.g., coming into your neighborhood you don’t want to disturb the neighbors … or maybe to deny the local constable from having another excuse to have a conversation with you.
     
  2. Teachdocs

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    Great write-up for April Fool's Day.
    Will never believe this without objective data, not just some theory.
     
  3. KILOCHARLIE

    KILOCHARLIE Formula Junior

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    Capristo offer a remote control fob which can be fitted to any exhaust with valves to open and close as you like. Think its around $250.

    I've always wanted to fit switches in the cabin behind the fuel cap and bonnet opener. I read somewhere where someone fitted this using relays in the electrical system but was a but complicated for my liking. I am sure a half decent auto electrician could link up a basic switch for a few dollars which would really appeal to me if anyone could source the necessaries.
     
  4. FerrariDublin

    FerrariDublin F1 Rookie

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    I am one that accomplishes this with two lengths of speaker wire and a six pole switch located in one of the blanks behind the bonnet and fuel cap buttons. Any auto electrician ought to be able to knock this out in a couple of hours. No faults, codes, CELs or otherwise.

    Toggle Switches : 6 Terminal DPDT : ElecDirect.com

    Granted, I had to cut into two wires to achieve this. Some owners might rather not do that but very satisfactory and next-to-impossible-to-detect use of heat shrink made that a non issue for me.

    A word though, I did this when I had OEM exhaust in place. I subsequently changed the back box for an aftermarket unit. With both systems I soon grew tired of the sound of the exhaust with valves open at low revs (just sounds bad, uneven, like a blown exhaust) and I used to just leave them in "auto" mode. The only time I see value in having the switch is when using the car on track.
     
  5. conscom

    conscom Formula Junior

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    Thanks Steve for the detailed explanation of the exhaust system with bypass valves.
    Enjoyed the read. I've already bought the Capristo Remote so will carry on with the install. Good luck on your new cottage industry. Gary
     
  6. bisel

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    Thanks, Gary. How do you like the Capristo unit? I am guessing you're satisfied with it. Do you have their programmable unit or the basic unit?

    How did you secure the control unit to the car? Did you use nylon cable ties? Any problems?

    Thanks,

    Steve
     
  7. KILOCHARLIE

    KILOCHARLIE Formula Junior

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    Hi Greg, I'd be very grateful if you could give any details on how you fitted this or if you have any pictures? Was it a case of cutting into the power cables of each bypass valve and then running a wire through the engine access panel to the centre console?

    Thanks for the offer of the remote control unit as well Steve. Looks like a great alternative to the capristo unit but in all honesty is overkill for my requirement. Personal taste but I always run my car with the valves open but on the rare occasion where I need to be stealthy I would like to close them without having to dig around in the engine bay. Would probably only do this once or twice a year when starting the car early in the morning or when on a long motorway drive.
     
  8. tazandjan

    tazandjan Two Time F1 World Champ
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    Nice thing about Steve's kit is it uses all the factory connectors, so no cutting and splicing required. Steve's is hooked up to a switch he put in the empty position on the 360 and mine on the 575M will use the Euro rear foglight switch, already there and unused in the US.
     
  9. FerrariDublin

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    #9 FerrariDublin, Apr 3, 2014
    Last edited by a moderator: Sep 7, 2017
    The procedure is really very simple.

    There are two wires going to the solenoid for each valve. I cut one of those wires and ran a speaker (twin) wire back to the cabin from each solenoid. The connections to the two ends of wire (now cut) I made off with heat shrink which leaves it nice and tidy.

    Once in the cabin with your two pairs of wires you "make" the circuit to allow the valves operate normally and you "break" the circuit to cut the electrical supply to the solenoid and force the valve to open and stay open.

    The trick is the six pole switch. This is effectively two switches contained within a single housing and operating on a single throw. There are three poles on the left and three on the right. Solder one of the speaker wires to the centre pole and the other to either of the other two. Now do the same for the other speaker wire (but make sure you use the same upper or lower pole as you used on the other side). Now the switch is making the circuit when in one position and breaking the circuit when in the other.

    Using a six pole switch you are ensuring that the right and left circuits do not mix. I'm not sure whether or not damage would occur if one used a three pole switch but it's not worth the risk.

    Insulate the back of the switch carefully to prevent any shorting to ground.
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  10. 308mash

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    I think you could use a DPST switch also so there's no center position. That switch has 6 connections because it's a double throw.
     
  11. FerrariDublin

    FerrariDublin F1 Rookie

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    You could indeed. The six pole is perhaps more commonly found and does the job but.
     
  12. KILOCHARLIE

    KILOCHARLIE Formula Junior

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    Thanks Greg, will undoubtably do this at some point if I have an hour to spare. Did you have to remove the engine access panel to feed the wires through?

    I also suppose I could even fit two SPST switches, one for each side, so in theory I could run one side with the valves closed and therefore a kinda half volume at idle. Its a shame the original ferrari switches are so expensive (such as the rear fog switch) as they would fit the blank switch sockets perfectly.
     
  13. bisel

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    #13 bisel, Apr 3, 2014
    Last edited by a moderator: Sep 7, 2017
    Very nice solution. I actually used relays as I wanted to re-use a Ferrari switch on the dashboard and that switch is a SDST switch.

    For you guys who want to try the DPDT switch option that is described above, I found a DPDT switch that perfectly fits into the Ferrari panel cut-out. For example, the 360 Modena has two black cut-outs in the center console. I think the Spider uses those for the top.

    The switch I found is an NKK switch. Number LW-3122-x4B0-A. the letter x can be F, H, K L or N. It designates voltage rating. The only one you don't want is E as that is 6 volts. The others are 12, 18, 24, 28 and 110. They come with or without lamps and the you can get various colors of lamp covers / filters and bezel. I got a simple black bezel, no lamps. When I tried the switch, I did not try to wire in lamps as I was switching the ground only. But if you are running both positive and negative to the switch, you can illuminate the switch.

    Here is the link for the NKK catalog for this switch ... http://www.nkkswitches.com/pdf/lw.pdf

    This is an ON - ON switch. There is no center position. So you merely toggle between two configurations that will use four of the six contacts.

    Do a Google search and you will find a several sources for this switch and it fits perfectly in the Ferrari panel cut outs ... at least for the 360, 550, 575 and 430.

    Two photos here ... one is the switch. The other shows that switch installed in 360 center console.

    Regards,

    Steve
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  14. burlroad

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    Hi Steve,

    I also just sent a note through your website, however are you aware if the standard exhaust system on the 360 also utilize exhaust bypass valves at programmed RPM ranges? I clearly see the exhaust bypass valves on Ferrari's racing exhaust system, but want to verify that your solution will also work on the standard exhaust system. Thanks a bunch!
    David
     
  15. mikeyr

    mikeyr Formula 3

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    I am not Steve but yes the stock 360 has valves that is what his controller controls. It allows you to bypass the motortronic opening/closing of the valves if you want. Or let it open/close them for you, best of both worlds
     
  16. tazandjan

    tazandjan Two Time F1 World Champ
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    Steve- Send that switch to Robbie at Sticky No More and he could make it match the other switches for very little money. Two Boxster switches similar to that one were less than $100 from Robbie, and that included stencils that looked like the originals.

    Still like the idea of using OEM switches better.
     
  17. bisel

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    Yes, I like OEM better as well. In installed that white switch initially in my car, but my tech found me a nice fog light switch ... for free. So I swapped out that white rocker switch for the Ferrari fog light switch. Looks much better.

    I just put that link on the note in case some one wanted a source for switch that fits in the existing black cut outs for very little money. I think I paid something like $9 for that one.

    Regards,

    Steve
     
  18. bisel

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    Source for Switches ...

    There are many people who for various reasons have made comments about getting Ferrari switches for their cars ... maybe as replacements or maybe because they want to add an accessory and have the switches match the originals.

    On eBay and elsewhere ... these switches can cost from $50 to $150. This is pretty expensive for a simple switch.

    Does anyone know where we could pool our buying power and maybe get a bunch of these switches. They come in two models:

    1. Off - (On) ... Normally Off, momentary On
    2. Off - On ... Simple On / Off switch

    The stencil on the switch differs according to it's function.

    I, for one, would love to obtain a couple of spares.

    Regards,

    Steve
     
  19. RBarbieri

    RBarbieri Karting
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    I have a blank space on my dash for a switch and was thinking of buying one that matches the others to be used for exhaust bypass. The price of the switch is a deterint.
     
  20. bisel

    bisel Formula 3
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    Yes, I hear you. When I installed my exhaust bypass, I first used a switch to fit into the blank in center console (I have the Modena so has two blanks in center console). Later, I was able to get a used fog lamp switch at no cost and I installed in the dash. Very nice there and easy to switch the exhaust valves.

    I was thinking that there are others, like yourself, who would want to get hold of switch but the cost is those simple switches is a deterrent ... as you say.

    Steve
     
  21. bisel

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    I have had some recent inquiries if it is possible to make a controller to have a mode of operation where the valves are always closed. Right now, the my controller kit only has two modes of operation ...

    1. ECU controlled (valves closed at low RPM and open when RPM > 4000 RMP)

    2. Valves always open

    By adding a third option to have the valves always closed would obviously make the car more quiet, especially at higher RPMs. This raises a couple of questions:

    1. Why does one want an always closed option?
    2. What are the potential pitfalls to closed valves at higher engine RPM?

    Besides just making the car quieter, I understand that many tracks have sound restrictions on track days that is disqualifying cars ...even with stock silencers. Having an always closed option may help these cars meet these restrictions.

    Another reason one may want to have the valves always closed, is when touring or cruising in the car. Having the ability to keep the valves closed at all times can lessen the noise inside the car.

    I checked on the potential pitfalls of having the valves always closed. There are some opinions that this could possibly have negative consequences on the engine. I checked with a couple of very knowledgeable technicians about this issue and was told that the only consequence is that there would be a bit less peak horsepower due to the increase in exhaust back pressure. There is even a positive aspect of a slight increase in back pressure ... higher torque. Some people have the perception that the engine might overheat. I am told this is not true.

    I have decided to add the Always Closed function to the controller. I will be introducing a new model with the Always Closed function in the next few weeks. The new function will necessitate adding some additional components and to keep the size small, I have to source some smaller components. When available, the user will have three modes of operation:

    1. ECU controlled (this is default mode)
    2. Always Open
    3. Always Closed

    I fully intend to add this function while maintaining the current price of $375. In the interim, I am reducing the cost of the current model to $350 until I exhaust my current stock of parts.

    You can read more here ...

    http://www.ferrarichat.com/forum/ferrari-parts-collectibles/442322-exhaust-valve-bypass-controller-3.html


    Regards,

    Steve
     
  22. Russell996

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    I believe you have been given bad advice. It was made very clear to me by Antonio Capristo that the exhausts are not designed to run with the valves shut at high revs (Capristo exhausts and OEM) when I was installing the Capristo remote valve control system - I have the earlier version of the system where there is an option to select full manual control but on no account should this be used on a Ferrari. I don't doubt you could design a muffler that would work with valves closed but not OEM.
     
  23. bisel

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    Hi Russel,

    Thanks for your comment. There might be some reason to believe that. Not saying you are wrong, but Capristo is a third party opinion and not necessarily the quintessential source for Ferrari engines. Also, why would this apply to Ferrari and not say ... Audi?

    I talked to two gentlemen who were both associated with and employed by Ferrari during the 360 / 430 development and one who was with Honda F1 Racing back when Honda engines were powering McClaren's. He was Ayrton Senna's engine tuner. Both stated that there should be no issue with fully closed valves with modern Ferrari's ... with the exception of reduced HP at elevated RPM (like 6500 or so). They stated that the amount of reduction will be small and not likely noticed by the casual driver.

    Fabspeed is making an exhaust controller and they posting notice that they will have an option for Always Closed as well.

    In my opinion, I would prefer to not run a car with Always Closed valves. But, how else does the car owner, who occasionally tracks his street car, to comply with rules on tracks that have noise restrictions in place that would otherwise disqualify their car?

    When cruising or touring at say 70 to 80 mph, the engine speed is likely to be right at 3500 RPM or so. At that RPM, the ECU will likely be on the cusp of valves open or valves closed. So, just cruising, I can see a reason why a person may wish to keep them closed for reasons of noise comfort.

    Papers that I have read on this subject state that incorrect back pressure (too high or too low) can have an effect on engine performance ... especially small displacement, high revving engines ... but the only effect I have read has been that of reduced engine efficiency and power at elevated RPM. I have not seen any research which states that there is any damage that may be caused. I have seen a paper where excessive exhaust back pressure could lead to the EGR valve re-cycling too much of the exhaust gas and this could lead to engine knocking. So, I expect there is potential for some detrimental effect in this case, but should this occur the car will log a P0401 code or something on that order and you would likely get the check engine light. But, for the case of merely closing off the bypass valves, I believe there would have to something else wrong to cause this kind of problem (e.g., catalytic converters are messed up).

    There are many opinions and anecdotal statements on this subject, but I do not know of any qualified source where there is evidence that incorrect back pressure can actually cause engine damage. One has to keep in mind that the key purpose of variable exhaust systems (e.g., bypass valves) is to attempt to optimize the exhaust for variable engine parameters. This is done to improve performance and efficiency. The noise factor is only a byproduct of variable exhaust flow. If it were not for the objective of providing a high noise factor, cars like Ferrari's and other high end sports cars could merely provide a variable exhaust system with reduced back pressure using just the silencer ... and maintain low noise levels. But, they chose instead to bypass (or partially bypass) the silencer to give the car that noise that so many of us enjoy.

    I would really like to see credible evidence that would associate excessive exhaust back pressure with anything that could lead to a situation other than reduced engine efficiency. And, of course I mean in the context of opening or closing the bypass valves on the car and not completely obstructing the exhaust flow.

    Thanks for your feedback.

    Regards,

    Steve



     
  24. MaranelloDave

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    Leaving the valves open does decrease back pressure, which reduces torque. This is why I mentioned you may end up with less torque at low revs if you run valves always open. Regardless, it's probably not a very big difference.
     
  25. bisel

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    I agree and that is what all the literature says as well. Including, in most modern cars, that the difference is small.

    Steve

     

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