In Cylinder Pressure Transducer Scope Diagnostics

In Cylinder Pressure Transducer Scope Diagnostics


hi guys Brennan from tap and so I wonder do something a bit different today I want to run through a diagnosis I did recently on a Mazda two and the way that I used the Pico scope to my advantage to do some testing pretty quickly whereas the tests to do physically would have taken quite a long time so what you’re looking at here is a in-cylinder compression waveform so I’m using my scope and I’m using a pressure transducer to get these readings to give you an idea of what you’re looking at if you go to the Pico website they’re really good Pico on that website they’ll run you through a lot of tests this is for the specific tests that I’m showing so I’m using my scope connected to the WPS 500 X pressure transducer it’s a Pico branded one but you could use this on any scope at all it does is output a voltage that correlates to a pressure so you could use it on anything comes with a bunch of adapters so I’ve got the spark plug out and inline it’s just like I’m doing a compression test so it comes with a fitting to go in but the difference with this is I’m able to see pressure while the engine is running so back to our scope capture what you’re seeing on the red trace is the pressure from that transducer and what you’re seeing on the blue trace is just when the coil events happening so I believe I was using a paddle probe and I just wanted to make sure the spark event wasn’t way out somewhere so this video really disregard that and we’re just interested in the red so current question was a master – it’s a Zed why 1.5 litre petrol very common they used it for over a decade or so tell me with the symptoms of poor idle pretty lethargic when you drive it but you know nothing out of for a small engine it didn’t feel too bad you had very low manifold vacuum and if you took the airbox off it it popped a little bit back through the intake so straightaway were starting to think of timing it was what setting a fault code so it was camshaft position sensor performance or something of that sort so you know you could go on a bit of a tangent and start to look into the cam sensor itself but with those just you know real-world symptoms that had I was pretty confident we had a timing issue so first thing you want to do if you’re looking into any kind of timing issue the ideal is to use a scope and get a known good cam and crank pattern killed cam crank correlation and compare it to what you’ve got so I went to the tap website went to the good scan scope data down to Mazda and luckily enough there was a same engine so I said why cam and crank sensors there now if I was to download that opening up in Pico it would show you what I’m talking about but it turned up perfectly good so where do you go from there the the timing seems like it’s out but it’s reading good on my cam crank correlation the reason for that was there’s only one camp sensor on this and it’s reading off the intake cam now this is a double overhead cam engine so the VVT gear is on the intake and always they’re going to put the cam sensor on that so they can monitor what’s going on so I’m perfectly happy that the intake cam timing is good I don’t want to go looking at VVT solenoid Zoar the VT key phases any of that sort I’m happy with it the things running terribly but I am concerned with my exhaust camp now we could tear the thing apart we could take the timing cover off on this one you know depending I didn’t actually get to do the job but there may be a chance of ritual taking the type of cover off and physically looking at it but let’s say it’s a Carlucci Kart you know it’s gonna take several hours to pull this thing apart that’s where the pressure transducer can come in handy so we’ve gone in cylinder and anyone that’s a seasoned user of this we’ll see what the problem is and where it is but for those guys that haven’t used it I’m a cool little tool that we’ve got on the tap website again if we go back to home and I’m gonna go into diagnostic programs this time so there’s so much behind each of these tires if you don’t go looking you’ll you’ll never see all these little programs that have been made and the one that I’m looking for is the compression waveform viewer it’s version 1 and version 2 the compression waveform viewer plus you can’t download it’s only 400 kilobytes I’ve got it sitting just here ready to go now if I put that same picture that we’re just looking at into this little program it’s the same picture we’re looking at so in Pico before I took the snapshot I already had my quadrants put in there but just for the sake of this program we’ll put them on again so it can do its own little calculations so this is just showing 720 degrees two rotations of the crank so that we can go through a full four-stroke cycle now I’m going to click these flag events and what that does is with some theoretical markers that are pretty close to where things should be happening so the exhaust valve should open here intake valve opening exhaust valve closing and the intake valve closing so logically if we run through our four-stroke cycle we’re got all of our valves closed we’re going to make some pressure but you’re gonna have the spark happen and we’re on the power stroke coming down here our exhaust valve will open and pretty close to that we should rise up to atmospheric pressure because there’s a bit of a delay here I’m not liking that we didn’t go through there’s always going to be a bit of overlap modern engine where our intake valve opens our exhaust valve closes but with an intake valve open and an exhaust valve closed we should pretty quickly pull some vacuum it’s quite a gap here and then when we get up to the intake valve closing it does as I would expect react pretty quickly and we’ve got all valves closed so we start to make power again like I said I’m pretty happy with where the intake valve is but this gave me enough evidence to call the customer and say you know what I’ve done two tests to show that the intake valve timing is okay but the exhaust valve timing I’m not happy with that to compare a known good for you just so you guys can see after the repair so if we just look at the quadrants that we’ve got um I might just bring up without having the flags on it I’m going to show you the bad first good so we’re looking at the bad look at the this is bad and look at the quadrants here so had this first quadrant there’s a bit of a delay at the second quadrant a bit of a delay now if I pull up the good things are already happening by the time we’re at that quadrant and then not much to lay it all we’re still and had over that period it can be a difficult one I found as a beginner this this is um something that I’m not massively skilled in I’m looking to use it more because wherever I can use technology to save time I’m all for it but you definitely can see the difference between the good and the bad look at the gap that we’ve got there look at the the time that we’ve got where as we were we were already mid pressure change on the other one so definitely enough evidence there so you know it’s something that just to keep in your bag scopes aren’t for everyone but I just wanted to show you someone a little bit show you guys a little bit more of an advanced thing with it main thing to take from this really is though get onto the TAT website and make sure you’re looking at what’s in behind all of these tabs here so just through that you know without tat I could have struggled to find today no cam crank there’s so many on there or at least if you if there’s not one get onto the technical assistance and we’ll go through all of our little databases or known people that we know that we can get onto things like that to try and help you out and that was pretty nice little look into some of the stuff that a diagnostic program Park can do as well so hopefully you got something from this one guys and I’ll see you next time


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