my capristo bypass valve turn blue | FerrariChat

my capristo bypass valve turn blue

Discussion in '348/355' started by darrenliu, Aug 9, 2009.

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  1. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
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    Darren Liu
    #1 darrenliu, Aug 9, 2009
    Last edited by a moderator: Sep 7, 2017
    I had to take out my capristo bypass valve because the diaphragm fail (does'nt hold vacuum). I noticed the valve body had turned blue. The valve was still hot to touch after an hour. This part must get extremely hot!
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  2. 285ferrari

    285ferrari Two Time F1 World Champ
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    Sep 11, 2004
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    Does Capristo warranty the valve? Exhaust gases do get very hot..
     
  3. Llenroc

    Llenroc F1 Rookie
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    Jun 9, 2004
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    Are they making those out of Ti, almost looks as if it is. Turns blue like that after it gets hot. IIRC stainless will do the same.
     
  4. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
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    I sent the valve back to my supplier in Sydney Australia for a warranty claim. The valve itself is fine, just the diaphragm part which can be very easily separated from the valve body.
     
  5. bcwawright

    bcwawright F1 Veteran

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    #5 bcwawright, Aug 10, 2009
    Last edited: Aug 10, 2009
    Just a guess but based on the price of these capristo valves is they are not titanium...way too high tech for these aftermarket regulars..lol

    If I were a betting person I would say for sure it is a ss alloy.......the problem I see is that if it is high grade alloy I would guess somewhere @1000 degress F or higher to get it to turn blue...I am puzzled by that high a temp that far from the exh port....it may have some sort of coating that is explainable for the color I see

    It also appears that the color change was not uniform...???

    Another puzzler is that the capristo valve fails in the open position as opposed to the factory failing in the closed position.....


    Over fueling problem???
     
  6. f355spider

    f355spider F1 World Champ
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    #6 f355spider, Aug 10, 2009
    Last edited: Aug 10, 2009
    Made from stainless steel, too heavy to be Ti. Hard to see the left side of it with the heatshield in place, but no discoloring on the right side of my Capristo valve, they rest that I can see has taken on a more golden hue. Mine has been on my car for over one year and about 4k or 5k miles with no problems.

    I wonder if the failure of the vacuum piece is caused by the lack of an insulator between it and the valve? The factory set up has a thin peice of insulating material between the two...almost looks like paper.
     
  7. AceMaster

    AceMaster Three Time F1 World Champ

    Feb 6, 2009
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    looks like a rainbow!
     
  8. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
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    D, see if you can look from underneath the car to see whether yours has turned blue.
     
  9. eulk328

    eulk328 F1 Rookie

    Feb 18, 2005
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    Hi Darren,

    Did you remove the thermocouple at some point (the small capped bung to the right of the bypass valve in your photo)? Perhaps it never had one for your version or your market.

    By the way, I see some conflict/irony in your public profile: "acoustics, noise control, all things ferrari Occupation: Acoustic Engineer" (specifically, noise control and all things Ferrari ;-)



     
  10. f355spider

    f355spider F1 World Champ
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  11. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
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    my 355 spider doesn't have the 3rd thermocouple or ecu. That's why I can run with the bypass open with no problems. In fact, when I get my bypass valve back from repair, I will install the capristo wireless remote control kit so that i can switch between factory bypass operation and bypass open full time. I already have the remote kit - its really quite simple, you get a wireless receiver, a solenoid valve and remote control fob. The solenoid valve gets plumbed in series with the existing capristo solenoid valve. When I hit the switch, a 12v signal is sent to the 2nd solenoid which cuts off vacuum supply and renders the capristo bypass open full time. You could even use this kit with the stock OEM bypass valve, but if you do so, the valve remains either closed full time or open full time depending on the setting.
     
  12. f355spider

    f355spider F1 World Champ
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    Just checked Darren, it is goldish in color, all they way around. Wasn't that way when I got it. I don't think you should be concerned...all metals change color from heat.
     
  13. darrenliu

    darrenliu Formula Junior

    Jun 24, 2008
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    Thanks D,

    Mine went from silver to gold within a couple of drives. Whilst the outside of the flange turned blue, the inside of the collar looked normal. My OEM valve looks normal also, which I had to put back so I could drive the car in the meantime.
     
  14. cinquevalvole

    cinquevalvole Formula 3

    Feb 6, 2004
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    #14 cinquevalvole, Aug 11, 2009
    Last edited: Aug 11, 2009
    http://upload.wikimedia.org/wikipedia/commons/0/0d/Anlassfarben.JPG

    Here you can see the table. We call it Anlassfarben (colours) for steel. Around 300 Celsius the steel turns blue.
    Some manufacturers use the effect for finishing & hardening bolts and other parts they sell.
    Recall all the motobike pipes in rainbow colours after first ride?
     
  15. bcwawright

    bcwawright F1 Veteran

    Jul 8, 2006
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    The color formed when stainless steel is heated, either in a furnace application or in the heat affected zone of welds(OR IN THIS CASE EXHAUST SYSTEMS), is dependent on several factors that are related to the oxidation resistance of the steel. The heat tint or temper color formed is caused by the progressive thickening of the surface oxide layer and so, as temperature is increased, the colors change. Oxidation resistance of stainless steels varies according to it's compostion as designated by the various main classifications(i.e. 304,306,321 etc.) and even the sub-classifications(e.g. 304L)

    However, there are several factors that affect the degree of color change and so there is NOT a single table of color and temperature that represents all cases. The colors formed can only be used as an indication of the temperature to which the steel has been heated.

    Factors affecting the heat tint colors formed:

    1.Steel composition

    The chromium content is the MOST IMPORTANT single factor affecting oxidation resistance. The higher the chromium, the more heat resistant the steel and so the development of the heat tint colors is delayed.

    2.Atmosphere

    The level of oxygen available for the oxidation process also affects the colors formed. Normally heating in air (ie approx. 20% oxygen) is assumed. In welding, the effectiveness of the shielding gas or electrode coating and other weld parameters such as welding speed can affect the degree of heat tint color formed around the weld bead.

    3.Time

    Laboratory tests done to establish the published heat tint color charts have usually been based on heating for one hour. As exposure time is increased, the temper colors can be expected to deepen ie make it appear that a higher exposure temperature may have been used.


    The original surface finish on the steel can affect the rate of oxidation and the appearance of the color formed. Rougher surfaces may oxidize at a higher rate and so could appear as deeper colors for any given set of conditions. As the colors formed are by light interference, then the smoothness of the surface can also affect the appearance of the colors formed. There is no specific data published that compares the effect of surface finish, but it is worth noting that surface finish can influence the conclusion on heating temperature, from the colors seen.

    The table below represents the temper colors that are LIKELY to form on stainless steel type 1.4301 (AISI 304) if heated in air.

    THIS INFORMATION MUST BE USED WITH CARE WHEN INTREPETING THE HINT TINT COLORS OBSERVED ON STAINLESS STEEL SURFACES AS THE HEATING CONDITIONS ARE NOT SPECIFIED(This is very important!!!!!)


    Color Formed Approx Temperature C:

    pale yellow 290
    straw yellow 340
    dark yellow 370
    brown 390
    purple brown 420
    dark purple 450
    blue 540
    dark blue 600

    (Please note this color temp indication list is different than the wikimedia.org chart that was posted)

    The OEM valve body appears to be the same material as is used for the header flanges....out of all the headers and by-pass valves(both good and bad) that I have here in the shop not 1 of them has turned blue.

    Hugh has used his capristo valve for some time now without any problems....I am also pretty sure that Hugh's car is well maintained. I doubt seriously that there is any mfg defect in the capristo main valve body that turned blue.

    My conclusion(which is just a guess) is that this valve malfunctioned due to other causes. It would be nice if some of the sponsors that sell this product or even capristo would chime in on this issue.

    I would like to know when the valve was pulled off was the butterfly in the full open position?

    I would have also like to have cut open the diaphram to see exactly what the condition was of the internals.
     
  16. darrenliu

    darrenliu Formula Junior

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    BCWAWRIGHT, thanks for the technical explanation.

    The diaphragm had failed in the open position as this is the 'natural' spring back position. When i moved the diaphragm arm up (to closed the valve), I noticed it didn't spring back down with the normal force. If the diaphragm 'melted', I'm concerned that it will happen again. I've asked my supplier to give me a spare diaphragm just in case.
     
  17. darrenliu

    darrenliu Formula Junior

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    #17 darrenliu, Oct 7, 2009
    Last edited by a moderator: Sep 7, 2017
    finally got my bypass valve back from my supplier. Capristo supplied me with a new vacuum diaphragm modified with an aluminium heat shield. I will be fitting this back into my car next week along with the capristo remote control kit to operate the bypass valve on/off.
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  18. sambomydog

    sambomydog Guest

    May 23, 2009
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    #18 sambomydog, Oct 7, 2009
    Last edited: Oct 7, 2009
    That looks very nice:) Very nice heat shield to, looks great. By providing the heat shield clearly capristo must have known the diaphragm was vulnerable.
    Out of interest what is the fundamental reason for anyone using a capristo valve compared to a standard 355 unit? Is it price or better exhaust performance?
     
  19. darrenliu

    darrenliu Formula Junior

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    reasons for using the capristo valve over the factory one are:

    Lower price
    Better design in respect to the rattling problem
    defaults to open position
     
  20. sambomydog

    sambomydog Guest

    May 23, 2009
    1,380
    Great thanks:)
     
  21. johan6504

    johan6504 Formula 3

    Jun 28, 2005
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    Is this new heat shield and vacuum diaphragm standard when you buy these valves today?

    One reason for buying capristo is to be done with the problematic valve once and for all, but if you get new problems I am not sure it is really worth it. I can live with the ratteling but a broken vacuum diaphragm every now and then sound worse. I know it will be in open mode when failing so it is safe but I dont feel like going from one problem to another...
     
  22. eulk328

    eulk328 F1 Rookie

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    #22 eulk328, Oct 10, 2009
    Last edited: Oct 10, 2009
    I bought one about a month ago. It came with the heat shield. I have not installed it yet as I'm still looking for some non-OEM O-rings that go on both sides of the valves (mine are stuck on the old valve).

    Maybe it is not perfectly safe to fail in the open mode either. There are some knowledgeable people that say you can get some excess fuel in the cylinders because of, I believe, reversion due to lack of back pressure. Yes, I know there are folks that have run with no valve for a long time and that the Challenge cars did not have them (although they probably did virtually no running at the rpm range where problems might be caused so, I would remove them from the equation).

    anyway... my understanding is valve failed closed can = high temp causing manifold damage which may (or may not) cause valve guide problems.

    Valve failed open = possible excess fuel delivery at some rpm range causing high cylinder wear because of oil dilution by fuel.

    This is just what I've read. Don't want to start a new debate about deleting the valve or not or the superiority of failing open or closed.

    I would GUESS that you would notice a valve that has failed closed (no increase in the "scream" at the usual rpm) before you would notice one that has failed open.

    No idea if the diaphragm material was in any way improved.


     
  23. gcthree

    gcthree Formula Junior

    Jul 18, 2008
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    Williamsburg, Va.
    Where do you get one, and how much? I see there's a used valve on the 'parts for sale' thread, and it's (gulp!) $600?
     
  24. Capristo Exhaust

    Dec 20, 2007
    152
    Sundern/Germany
    Hello Together,

    The reason for this is the superheated exhaust, I did not know who built it, but I can already say that generates much heat.

    nich, it is easy to explain, I'll have to explain by Martin, he may be better English.
    Incidentally, the valve is made of T309 stainless steel and ball bearings made of silicon carbide, which is the best thing to take.
    to this system, we have a patent
    Ciao Antonio
     
  25. Capristo Exhaust

    Dec 20, 2007
    152
    Sundern/Germany
    #25 Capristo Exhaust, Nov 5, 2009
    Last edited by a moderator: Sep 7, 2017
    Hello together,

    At first I excuse for my typing errors but my English is not so good. Martin has made a
    translation. He is working as correspondent for Capristo Exhaust Systems.

    I had promised to explain how the problem of overheating occurs with the F355
    and results into a damage of the manifolds.

    The problem begins once the exhaust gas valve opens. For this reason it is important
    that such a valve works smoothly. Once the exhaust gas valve, the exhaust gases do not
    flow through the main catalytic converter but completely through the bypass. The exhaust
    gases flow off the exit which leads to the main catalytic converter and generate there a
    vacuum. Thus the hot exhaust gases being in the muffler are aspirated backwards
    through the main CAT which additionally heat up the gases. Then the gases are guided though the bypass and radiated by the exhaust gas valve into the muffler again.

    When the exhaust gas valve is open, this gas flow is circulating ceaselessly generating more and more heat. We are of the opinion that this problem is known to Ferrari. For this reason the F360 was changed since 1996 from engine 2.7 to 5.2 and the manifolds were modified exactly
    in the place where the vacuum is generated. But the problem was not eliminated by this measure.

    Now you can imagine that an extreme back pressure is generating in a case when the complete exhaust gases coming from the engine and those which are aspirated backwards have to flow through 1 exhaust gas valve. That’s the reason why the F355 does not provide
    the power as indicated. I try to attach a picture where this fact is displayed.

    We have dealt with this problem of the F355 for a 6 months’ period. We made many tests.
    We have installed probes on the complete exhaust system and have run the car on the Dynojet. We have analyzed the complete exhaust gas flow and then we found the reason for
    the problems in the main catalytic converter.

    To find out the exact reason we had manufactured a complete F355 exhaust system, however,
    without the bypass and we had installed two exhaust gas valves. That’s our Capristo 355 Racing exhaust system. Then we have tested this exhaust system on the Dynojet. We have
    tested about 15 different cars. The increase in power was found to be between 22 up to 31 HP.

    So it was obvious for us that our theory was right and that the bypass causes this problem and that 1 exhaust gas valve is not sufficient and thus leading to extensive heat due to the back
    pressure.

    Our exhaust systems, irrespective of the racing or the usual model, are so designed that the ways from the main catalytic converter to the outer end pipes guide and those from the bypass
    to the inner end pipes. These ways do not lead to each other. Consequently it is not possible
    when the vacuum in the main cat is generated that hot exhaust gases are aspirated but it
    aspirated cold air through the outer end pipe backwards through the catalytic converter and the bypass and the valve. Once cold air is mixed up with hot exhaust gases, the temperature
    of the exhaust gases is decreasing and also the temperature of the complete system.

    For this reason we advise against the installation of sports catalytic converter or spare tube
    on the 355 because they can simply not provide any performance. A sports catalytic converter
    or spare tube shall allow the flow of exhaust gases at higher temperatures. But it makes no sense to do this with a 355, because the exhaust gases do not flow through these parts but
    through the bypass.

    It is quite the opposite. The larger the flow the more is aspirated. This means more loss in power.

    I hope that you do understand what I mean. There is a video on YouTube where the exhaust gas streaming of the 355 has been analyzed by us.

    Should you have any questions please contact either us or the company Taurino being our USA distributor for our products.
    Antonio
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