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SR20DET spitting oil/ Left Foot Braking problems

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  • SR20DET spitting oil/ Left Foot Braking problems

    Hi there! 2 issues I wanted to tackle in one thread:

    My SR20DET (S13 Blacktop) has been spitting A LOT of oil out of the valve cover breather since the last rebuild. Oil seemed to just shoot out of the breather hose (vented to the floor) when I'd drive it on full boost (5-7k RPMs). After messing about with checks valves and hoses with no success, we decided to send it back to the machine shop to get the cylinders re-done.

    It *seems* to be spitting out less oil now, but I havent had a chance to really test the car on full boost for extended periods of time.

    This all happens around .5-.7 BAR of boost, and the engine still pulls hard.

    Do you guys normally collect a lot of oil in your catch cans? Or could there actually be something wrong with my engine?

    Obviously, I'm not re-routing the breather hose back to the intake. Could this be the source of the problem? The thing is, the amount of oil and blow by seems very abnormal. Ill try testing the car again soon to see if it still spits out an alarming amount of oil.

    Second issue:

    I've been learning how to utilize left foot braking while drifting using sims and a team mate's car, but when I try to use the technique on my car, something weird happens.

    *This happens under boost*
    -First application of left foot braking, OK. I have feedback from the brake pedal and the brakes work.
    -I lift my left foot from the brakes and re-apply, brake pedal is stiffer, less feedback, less braking power
    -I lift my left foot again and re-apply the brakes for a third time, Super stiff pedal and the brakes dont slow down the car at all.

    This makes it impossible to modulate the brakes with my left foot while im accelerating.
    Should this be expected of a turbo car? I dont understand why my team mates car doesnt exprience this, though.

    Thanks for any help!

  • #2
    The left foot braking problem is 100% normal behavior. When you're under boost, you are using up the vacuum in the booster with every application of the brakes.

    Why would you want to LFB a RWD car under acceleration though?



    What valve cover do you have? The S13 ones have less baffling in the VC, so they tend to shoot more oil out. But what you describe sounds like way way too much.

    How is the PCV valve in the VC? Maybe it's failed and letting boost flow into the VC.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
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    • #3
      @Def

      Left foot braking while on the accelerator keeps the boost up, is one way to smoothly tighten your line, and a way to slow down while chasing someone during a tandem run without the risk of losing wheel spin and straightening out.

      I don't have any advanced knowledge on brakes, but could there be a way to keep more "reserved" vacuum in the booster? Bigger booster(?)
      The other thing is, my team mate's car doesn't experience this problem. His vehicle is also fitted with an SR20DET.
      And just to confirm, Im guessing this phenomena doesn't happen with N/A cars right?


      As for the PCV valve, we tried replacing it, and even installed 2 PCV valves at the same time (haha!). I have a feeling the block wasn't machined properly or the piston ring gap wasn't checked very well. Seemed like the rings weren't sealing, causing excessive blow by.

      We reassembled and re-installed the engine a few weeks ago and there was no oil during the break in (4k rev limit, not reaching much boost), but when I tested the brakes, I would have to go into full boost to see if the pedal would stiffen. When I brought it back into the shop, I noticed oil from the breather again. Not as much as before though, but still shooting out an amount of oil.

      Ill try to get a proper catch can so I can monitor how much oil comes out. Smog/ Emission laws are just a suggestion here in the Philippines so the shop just connected a rubber hose from the valve cover that empties out under the engine bay.

      Comment


      • #4
        You can add a vacuum reservoir/canister. It's common in old muscle cars with really lopey idles and weak vacuum. It's basically just a can with fittings to put it on the booster side of the check valve in the brake line. It won't give you infinite braking while under boost, but might give you an extra application or two before it goes really hard.


        I guess the LFB under boost thing is a drifting only thing. I can't see how it'd be faster on a track.



        For the oil out the crankcase, it probably is something with the rings being gapped incorrectly or something mechanically wrong like that.

        You might try a catch can (or two in series), and then put a fitting on the bottom to drain back into the crankcase. So you'd let the crankcase pressure out, but not puke up all your oil immediately under boost.

        Also check the condition of your valve cover. You might pop rivet in an additional baffle plate or something to try to keep the oil down to a minimum going out there, or look into a modded S14 valve cover.
        '18 Chevrolet Volt - Electric fun hatch for DD duty!


        DefSport Koni Sleeve and Spring Perch Buy!!!
        http://www.nissanroadracing.com/showthread.php?t=5902

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        • #5
          Thanks!

          The shop did suggest doing a set up where oil would be re-routed back into the crankcase, but I wanted them to find the problem first, not try to find a way to work around the problem.

          Although, wouldnt the oil coming out of the breather be "dirty oil" or not necessarily?

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          • #6
            As long as you have a filter on the breather so that dirt can't enter the system, any oil spitting out of the breather will be sucked right back into the engine and will be fine.

            Instead of adding an additional line, I suggest routing the breather line to the bottom of the catch can. As soon as you lift off throttle, there's a vacuum in the system now and the engine should suck back up any oil that was spit out in the previous run.

            No, it's not the "right way" to fix your problem as it does sound like you have increased blow-by. But it's an interim fix until the next time you go through the engine.
            you might run a leakdown test on the engine to see if it's your rings or something else having issues. that should be fairly easy to determine.
            Originally posted by SoSideways
            I don't care what color they are as long as they are LONG AND HARD.
            '04 G35 Sedan 6MT- The DD
            '96 240SX- The Track Toy

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            • #7
              Originally posted by Matt93SE View Post
              As long as you have a filter on the breather so that dirt can't enter the system, any oil spitting out of the breather will be sucked right back into the engine and will be fine.

              Instead of adding an additional line, I suggest routing the breather line to the bottom of the catch can. As soon as you lift off throttle, there's a vacuum in the system now and the engine should suck back up any oil that was spit out in the previous run.

              No, it's not the "right way" to fix your problem as it does sound like you have increased blow-by. But it's an interim fix until the next time you go through the engine.
              you might run a leakdown test on the engine to see if it's your rings or something else having issues. that should be fairly easy to determine.
              Hmm so you mean the line from the valve cover breather can actually pull back the oil into the crankcase? If this works, it might be a great idea right now.

              Comment


              • #8
                Yep. I've had my KA set up this way for years. On throttle, it spits oil into the catch can. Off throttle, its turns to vacuum and sucks the oil back into the valve cover.
                Originally posted by SoSideways
                I don't care what color they are as long as they are LONG AND HARD.
                '04 G35 Sedan 6MT- The DD
                '96 240SX- The Track Toy

                Comment


                • #9
                  Originally posted by Matt93SE View Post
                  Yep. I've had my KA set up this way for years. On throttle, it spits oil into the catch can. Off throttle, its turns to vacuum and sucks the oil back into the valve cover.
                  TIL, Matt has an obsessively bulimic KA.
                  '18 Chevrolet Volt - Electric fun hatch for DD duty!


                  DefSport Koni Sleeve and Spring Perch Buy!!!
                  http://www.nissanroadracing.com/showthread.php?t=5902

                  Comment


                  • #10
                    What is your complete breather setup like? An s13 valve cover has 2 ports and the crankcase has one.

                    And it sounds like you have a vacuum issue. Maybe a slightly torn booster diaphragm?

                    While left-foot braking on throttle is definitely a drifting thing, it is also a technique sometimes used especially with turbo cars when you just need to slow down a little to keep the turbo spooled.

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                    • #11
                      Originally posted by Matt93SE View Post
                      Yep. I've had my KA set up this way for years. On throttle, it spits oil into the catch can. Off throttle, its turns to vacuum and sucks the oil back into the valve cover.
                      Thanks so much man! We routed the breather hose on the bottom of the can to try it out. Hopefully i can test it by the end of the week!

                      Comment


                      • #12
                        Originally posted by jfryjfry View Post
                        What is your complete breather setup like? An s13 valve cover has 2 ports and the crankcase has one.

                        And it sounds like you have a vacuum issue. Maybe a slightly torn booster diaphragm?

                        While left-foot braking on throttle is definitely a drifting thing, it is also a technique sometimes used especially with turbo cars when you just need to slow down a little to keep the turbo spooled.
                        That's the thing also. I know for sure left foot braking while on throttle is used by a lot of seasoned rally guys.

                        We just changed the booster and master to a R32 skyline set up to match the brake set up im using, and overhauled the front calipers. It got a little better, but still happens. (Dammit could my new booster be iffy, too? Or maybe I should check the one way valve to the booster again?)

                        Although during one test run, I threshold braked from 100kph and the car wasnt slowing down as one would expect, and if I added a few mm's more of pedal pressure, the fronts would lock up. Apparently the shop found a leak on one of the fittings so I'm hoping that the brakes will work properly now. I've yet to have time to test the car yet though. (Although I dont think the leak would've caused the brakes to stiffen/ lose vacuum)

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