My FYI Thread.





Page 1 of 3 1 2 3 LastLast
Results 1 to 20 of 50

Thread: My FYI Thread.

  1. #1
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default My FYI Thread.

    I thought I would do a thread where I can give some basic understanding to those who do not know. This is NOT land rover specific and will be for any type of vehicle. I will post new items to this thread as I get time, so I honestly hope it can help some people with understanding certain things, as well as help them with fault finding and some DIY fixes..

    So I decided I would do a quick write-up on some basic turbo principals as well as why certain servicing of the vehicle components are important.

    We all know what the purpose of a turbo is, but some might not, so let me just note some of the obvious items regardless.


    a Turbo's turbine shaft is driven by the exhaust gasses which allows the compressor wheel to suck in air and compress it and push compressed air into your engine, thus making it forced induction.
    There are 2 ways to controll the amount of boost a turbo produces.
    1. Wastegate
    2. VNT (Variable Nozzle Technology)
    a Wastegate turbo opens a valve before the turbine which relieves some of the pressure which were to be sent through the turbo's turbine and instead redirects the gasses to the exhaust.
    This simply allows the turbo to not completely overspin and either blows the engine by overboosting.
    Wastegate turbos work on boost pressure which opens the valve at certain boost levels usually controlled by a solenoid.
    a VNT turbo works differently to wastegate turbod. inside the housing is a set of vaned nozzles which is arranged on a circular plate which rotates and allows the air to be directed to the inward/ourward surface of the turbo turbine shaft.


    When directed inwards, it allows the turbo to run at lower RPM, and as it is directed to the outer surface the turbine RPM will increase. This system works with vacuum which is controlled by a solenoid and are only used on Diesel engines.


    One very important thing to note about a VNT turbo is that is has to have a maximum flow setting. This is controlled by setting a stop point using a small grub screw on the turbo core. to obtain this setting, you need use a flow bench, It is important to know that this screw should not be fiddled with.


    So, some things to note about VNT turbos. The vanes in the housing can build up alot of carbon, this can get the system to get stuck in an open, closed or inbetween position. This will typlically let your diesel engine run into limp mode and if rigged up to an OBDII scanner, you will get an errorcode stating underboost/overboost.
    To rectify the problem, it is best to have a preofessional open the turbo and either clean the VNT system, or if damaged replace it. The VNT vanes can get damaged and deform if it sees extreme exhaust gas tempratures, so if this is the case, you need to determine the cause of it.

    Other method to clean the system is to spray oven cleaner into the system and allow it to pass through the VNT nozzles which will release the carbon buildup and in most cases cleans the VNT enough so it can run properly again. It is however important to understand the system before spraying stuff down your engine. In some cases, it is possible to remove the EGR pipe if it is located above the turbo's inlet of the exhaust system, this will allow you to get the stuff sprayed in. If however your EGR is located on the oposite end of the manifold, you need to be caseful in spraying stuff in there in large quantities as it might find its way into the exhaust valves before it gets to the turbo. In these cases it is best to spray little at a time instead.
    This is for all turbos, not just VNT turbos. Oil, oil filters and Airfilters needs to be serviced regularly on turbo engines. My rule of thumb is every 7500km's you need to replace "oil", "oil filter" and "airfilter".
    Oil contaminants cause 80% of turbo failures.


    Why Airfilter?? Well it is simple. One of the second largest causes of failed turbos are caused by dirty air filters or exhaust blockage (i.e catalytic converters) The reason for this is a little difficult to explain, but let me give it a try. The turbo is designed to suck in air fron the front side of the compressor wheel, and compress the air on the vertical side of the compressor wheel. Every action has an reaction and if the turbo needs to fight against a dirty air filter, it causes the compressor wheel to be pulled hard towards the inlet, which sadly gives immense load on the thrust bearing. Once the thrust bearing gets worn, even by a quarter of a milimeter, it allows the turbo's exhaust seal to also start damaging the bearing housing and the shaft which will first have oil seep into the exhaust and intake and eventually damage the turbo to such an extend where it cannot be repaired and you have to replace the entire core. The principal is exactly the same for blocked exhaust, but instead the turbine attempts to force out the air and pushes against the shaft, but in the same direction as the blocked airfilter would. So the mor open the intake and exhaust system, the better for the turbo, so keep those filters clean.


    The other cause of failure to turbo's are due to oil coking or carbon build up.. So Carbon build up can be lessened by simply replacing the oil and oil filter regularly, which helps to keep the oil channels to the turbo free from buildup, if carbon builds up, it will restrict the oil flow to the turbo, a turbo typically runs are between 40 000rpm to 140 000rpm, so less oil is bad!!
    Oil coking occurs when the turbo has been working hard with loads of heat retained in the turbo, as the engine runs the oil is flowing as supplied by the oil pump. Once you switch of the engine, the oil stops flowing and the oil that gets stuck at the turbo inlet and inside the turbo itself gets so much heat from the extremely host turbo and manifold that it starts cooking, if oil cooks it becomes a solid and each time this happens it builds up another layer until it is blocked completely which will lead to complete turbo failure. To overcome this, simply drive at lower rpm for the last few minutes when reaching your destination and let the engine idle for 2 to 4 minutes before switching of (or fit a turbo timer) This allows the system to cool down by the oil passing through as well as the water cooling and the temprature of the manifold and turbo decreases, this will now prevent the oil from getting to a point of boiling.


    Remember that if well maintained, any turbo can outlast the engine by double the lifetime.

    EDIT.

    Final thought, though I have never seen it on this forum in the short time being here, but some mechanics have told people that they should fit oil restrictors to the turbo for turbos that lighty burns oil due to the reason that the vehicle oil pressure is too high for the turbo! Please do NOT do this!! if a turbo still smokes, even after repairs, it is not oil pressure related, I promise you. That is simply because the turbo was incorrectly repaired. Either the clearances in the housing is too large or the turbo was repaired using cheap chinese kits with rings that are too small for the bearing housing. NEVER restrict oil to your turbo.. you won't restrict oil to you engine, would you?
    Last edited by Splint; 2019/08/16 at 08:31 AM. Reason: fixed some spelling here and there..

  2. The Following 17 Users Say Thank You to Splint For This Useful Post:


  3. #2
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Engine Oil and Oil pumps

    Oil and Oil pressure.

    I got a comment the other day from someone, that their new oil pump they fitted had made lower oil pressure than the standard and for that very reason he had to fit a washer to the oil relieve valve's spring to increase oil pressure.

    For that very reason I am writing about oil and oil pumps.


    To get back to the comment I received, Oil pumps do not create pressure at all, the exit points in your engine is what creates the pressure. In other words, oil pumps creates flow and your bigends, mains and cam journals being exit points, will require the correct clearances on the parts like the bearings. So a worn engine will likely have lower oil pressure not related to the oil pump. On the other hand, If the pump is worn, it will not be able to flow enough oil to allow pressure to build up and finally oil viscocity also contributes to oil pressure related issues. Adding washers to the relieve valve is not recommended, though it will allow more pressure to the system before it is being allowed to bypass.


    The reason why high mileage oil is used on high mileage engines is simply because they will give a thicker (higher viscocity) oil to compensate for the wear on the exit points.
    To understand viscocity of oil and why it is important. Oil viscocity is how a fluid is measured for its resistance to deformation. In other words, it is important to understand that your oil should be able to pass through the ports without any difficulty and create a barrier under certain pressures and temprature ranges between 2 surfaces. To demonstrate this, given 2 flat pieces of metal. if we pour water through a pipe onto the one surface and put the other one on top of it, the water does not have the resistance to keep the two pieces apart as the water is thing and can deform quickly and will therefore be push away from the surfaces easily allowing the surfaces to touch. If we do the same with oil, it has a higher viscocity rating and the oil will keep the surfaces from touching each other while under a certain amout of pressure. (It is actually a little more complicated than this when it gets to clearances, but if anyone wants me to elaborate I will happily do so).


    There is however a bit more to this and that is where oil ratings come into play. We need to also consider the temperatures that different oils can keep up viscocity without thinning down to a level that will cause damage.

    Let's use the following oil rating example. 5W-40


    W stands for Winter.. yes it does . The number before is the W is the flow rate of the oil at 0 degrees farenheit, or -17 degrees celcius, where the number after the W represents the viscosity flow rate at 100 degrees celcius. So 5W-40 has a viscocity flow rate of 5 at -17 Degrees celcius and will increase to 40 at 100 degrees celcius... So the area you live in should be considered when using oil as that can make a difference to engine noise, wear and ease of startups.


    Note. I did not cover monograde oils as it is seldomly used these days in cars.
    Last edited by Splint; 2019/08/15 at 02:20 PM.

  4. The Following 6 Users Say Thank You to Splint For This Useful Post:


  5. #3
    Join Date
    Oct 2016
    Location
    Polokwane
    Age
    53
    Posts
    641
    Thanked: 455

    Default Re: My FYI Thread.

    "W stands for Winter.. yes it does . The number before is the W is the flow rate of the oil at 0 degrees farenheit, or -17 degrees celcius, where the number after the W represents the viscosity flow rate at 100 degrees celcius. So 5W-40 has a viscocity flow rate of 5 at -17 Degrees celcius and will increase to 40 at 100 degrees celcius... So the area you live in should be considered when using oil as that can make a difference to engine noise, wear and ease of startups."

    If I drive a vehicle and the temperature is always between 0 and 45 degrees Celsius, which oil should I use?

    PS. What is a good flow rate?
    Last edited by DC Polokwane; 2019/08/15 at 02:52 PM.
    Jeep Grand Cherokee 2002 4.7 V8

  6. #4
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Re: My FYI Thread.

    Quote Originally Posted by DC Polokwane View Post
    "W stands for Winter.. yes it does . The number before is the W is the flow rate of the oil at 0 degrees farenheit, or -17 degrees celcius, where the number after the W represents the viscosity flow rate at 100 degrees celcius. So 5W-40 has a viscocity flow rate of 5 at -17 Degrees celcius and will increase to 40 at 100 degrees celcius... So the area you live in should be considered when using oil as that can make a difference to engine noise, wear and ease of startups."

    If I drive a vehicle and the temperature is always between 0 and 45 degrees Celsius, which oil should I use?

    PS. What is a good flow rate?

    Are you refering to your climate temperatures of 0 to 45 or your engine temp? If you are refering to climate temps, I would say stick between 10W40 and 15W-50.. also consider the mileage on the engine because of the wear. There is also not really a good flow rate, it depends on what the engine specs require, but that also again depends on the engine wear.
    Last edited by Splint; 2019/08/15 at 03:02 PM.

  7. The Following 2 Users Say Thank You to Splint For This Useful Post:


  8. #5
    Join Date
    Oct 2016
    Location
    Polokwane
    Age
    53
    Posts
    641
    Thanked: 455

    Default Re: My FYI Thread.

    Quote Originally Posted by Splint View Post
    Are you refering to your climate temperatures of 0 to 45 or your engine temp?
    The climate temp. How does it affect ones choice?

    Engine operating temp is 95
    Jeep Grand Cherokee 2002 4.7 V8

  9. #6
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Re: My FYI Thread.

    Quote Originally Posted by DC Polokwane View Post
    The climate temp. How does it affect ones choice?

    Engine operating temp is 95
    Ok, in short, the hotter the environment, the higher you want the rating, so in your case 10 to 15W cold range and 40 to 50 hot range. If temps will be well below the 0 degree range in evenings or mornings, I would rather remain in the 10W or 5W range.
    Last edited by Splint; 2019/08/15 at 03:26 PM.

  10. The Following 2 Users Say Thank You to Splint For This Useful Post:


  11. #7
    Join Date
    Oct 2016
    Location
    Polokwane
    Age
    53
    Posts
    641
    Thanked: 455

    Default Re: My FYI Thread.

    Quote Originally Posted by Splint View Post
    Ok, in short, the hotter the environment, the higher you want the rating, so in your case 10 to 15W cold range and 40 to 50 hot range. If temps will be well below the 0 degree range in evenings or mornings, I would rather remain in the 10W or 5W range.
    The manufacturer spec is 5w30

    Considering my environment (we hardly ever see temps as low as 5 degrees and then only for like two or three days, high temps between 30 and 45).

    I should then use 15w50?
    Jeep Grand Cherokee 2002 4.7 V8

  12. #8
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Re: My FYI Thread.

    Quote Originally Posted by DC Polokwane View Post
    The manufacturer spec is 5w30

    Considering my environment (we hardly ever see temps as low as 5 degrees and then only for like two or three days, high temps between 30 and 45).

    I should then use 15w50?
    If the manufacturer spec is 5W-30, I would also consider the engine wear and just settle for 10W-40

  13. The Following User Says Thank You to Splint For This Useful Post:


  14. #9
    Join Date
    Sep 2007
    Location
    Johannesburg
    Age
    61
    Posts
    5,321
    Thanked: 1699

    Default Re: My FYI Thread.

    Oil is rated at SAE *W **, what this means is that the Spec of this oil is in compliance to the Society of American Engineer's standard and that it is * viscosity in Winter and ** when at operating temperature or hot so the 5W40 is a 5 viscosity when cold and that of a hot 40 viscosity at operating temperature so you get the best of both worlds. Lower viscosity for easy starting and better lubrication when needed most with higher viscosity when at operating temperature and high performance. I don't know what temperature they use as their Winter mark but most cars run at about 90- 110 operating temperature regardless of outside or ambient temperatures. The numbers have nothing to do with temperatures but indicate the viscosity (thickness) of the oil

    Oil's purpose is not only lubrication but a whole lot more than that, it has to be an excellent thermal conductor, Things like your crankshaft or camshafts that do not have water cooling relies on oil alone to cool it. A lot of engines have oil sprayers under the pistons to help cool the pistons as well as lubricate the bore.
    Another critical purpose of oil is detergent properties, it is supposed to keep gunk and carbon from accumulating and depositing in the enige. More expensive oils have better detergent properties than the cheaper stuff and this has often lead to oil like Castrol GTX 20W50 getting a bad name.

    Put yourself in this scenario, young student buys his first little golf but as with all students money is scarce, he runs regular petrol and does not do the most maintenance and services on the golfie 15k - 20k oil change with filters and plugs every second service. Oil is the cheap stuff from the supermarket and as fa as he can tell this works as good as the expensive stuff......
    A couple of years later and he has graduated with the golfie still going strong and he now earns a reasonable salary. He feels sorry for the hard time he has given the golf and decides to make up for the rubbish oil he has used and buys a bottle of GTX. This is where things go wrong, within 6k km the engine seizes vas, beyond, fubar. GTX is blamed and rightly so, see the years of cheap oil without good detergent properties has left a lot of gunk and carbon buildup in the engine. Along comes GTX and it has good detergent properties and from the first start it starts cleaning the gunk in the engine, the poor oil filter has to work overtime to keep the rubbish out of the bearings and mating surfaces and it does such a good job that after only 6000 km it is blocked, so much so that the engine does not get adequate oil. With the oil pressure sensor sitting between the oil pump and the filter the little red idiot light never comes on to warn the youngster.

    As for the turbos........it is a combination of witchcraft and science
    . I agree with most of your theory's but as far as main failure causes is boost leaks, if the system has a leak the turbo will over spool to try and get to the reqired setting with a unit running at 200,000 rpm you don't want it to spin faster if not needed. There are a reasonable safety built in regarding the speed that they can spin but in most cases over spooling is catastrophic. I have seen many turbos disregard a choked air cleaner and just suck pieces out of the filter element with total disregard. I have also seen what little bits of debris to an impeller, not nice.

    I cringe when I see the recommendation of spraying oven cleaner in the system It is made for ovens hence the name oven cleaner. If you love your turbo never let anything strange near it. If it is dirty only let an expert clean it, he knows how to treat it. If you are confident in your own ability then take it off and then do it on the workbench under clean and controlled conditions

    Modern turbos do not need to be run down.....or so the sales folk would like us to believe, proper run up and run down will save a lot of heart ache. Few people understand the term coking and what it does, it is real and it kills turbos believe me. I have more turbo bits and pieces lying in my workshop than most commercial places, racing engines have taught me a lot about keeping a daily from breaking.


    Henk
    Adventure is out there go find it

    Fitment and trailer service. Agent for SnoMaster & Tentco
    Follow us on Facebook

  15. The Following 4 Users Say Thank You to hbannink For This Useful Post:


  16. #10
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Re: My FYI Thread.

    Quote Originally Posted by hbannink View Post

    As for the turbos........it is a combination of witchcraft and science
    . I agree with most of your theory's but as far as main failure causes is boost leaks, if the system has a leak the turbo will over spool to try and get to the reqired setting with a unit running at 200,000 rpm you don't want it to spin faster if not needed. There are a reasonable safety built in regarding the speed that they can spin but in most cases over spooling is catastrophic. I have seen many turbos disregard a choked air cleaner and just suck pieces out of the filter element with total disregard. I have also seen what little bits of debris to an impeller, not nice.

    I cringe when I see the recommendation of spraying oven cleaner in the system It is made for ovens hence the name oven cleaner. If you love your turbo never let anything strange near it. If it is dirty only let an expert clean it, he knows how to treat it. If you are confident in your own ability then take it off and then do it on the workbench under clean and controlled conditions
    Well, as harsh as it might seem, over cleaner is a degreaser and breaks down carbon, similarly to the engine cleaners we use in the shops. With VNT Turbos the cleaner's foam builds up before the VNT vanes and it then runs down through them losening the carbon and residue. It never reaches the turbo parts that can cause harm like the CHRA bits. I am in the turbo industry and to have a turbo removed can become expensive to some people. Like I said it is recommended to remove the turbo and have a specialist clean the VNT as it is not a job for the average person, but it can be expensive. Typically if I remove a turbo to clean the VNT I am already halfway through the job and might as well just recon the turbo, but that does not come free

    As for the main reason for turbo failure being overspooling, This does happen, but there are clear signs to this, one of them being Orange peel effect. Orange peel effect happens when the turbo spools way above its rpm range and the extreme forces expands and contracts the compressor wheel. Orange peel can be seen on the back of the turbo compressor wheel and looks like tiny little cracks in a clear coat. The deformation and vibration can then destroy the turbo. This usually will result in a broken shaft. but most factory fitted turbo vehicles have failsafe built in to ensure this does not happen, unless you start tampering with boost pressures.

    Speaking of boost pressures, something I completely forgot to mention in my original post. Loads of people are refering to to boost pressure as if it is the main thing. 1 bar boost can be achieved with a siringe, but you would need to pump that siringe at a million pumps per minute to give the volume required to boost a car engine through its RPM range. Point being that for those who do software on their vehicles to get better performance needs to consider that one of the factors are that to increase performance on a turbo vehicle, they usually push up boost as well, this makes the turbo work harder to maintain the higher boost pressure, however in most cases the turbo is a little larger than the engine really needs so upping "some" boost does not cause turbo harm. I would however recommend that where possible, upgrades to the turbo is done (not all turbos allows for upgrades to internals and requires undesirable aftermarket repalcements and modifications) as the larger components will flow the same amount of air at lower turbo RPM than the smaller components before it was upgraded.

    Modern turbos do not need to be run down.....or so the sales folk would like us to believe, proper run up and run down will save a lot of heart ache. Few people understand the term coking and what it does, it is real and it kills turbos believe me. I have more turbo bits and pieces lying in my workshop than most commercial places, racing engines have taught me a lot about keeping a daily from breaking.
    a Salesmen will be beaten like a stepchild, he is not technically skilled to make such assumptions and unless the turbo is made from diamond material from the planet urgorh in the 9th galaxy from here, the turbo WILL fail due to oil coking if you do not allow it to cool down.

    The numbers have nothing to do with temperatures but indicate the viscosity (thickness) of the oil


    It actually does. the number *W is the viscosity at 0 degrees farenheit (-17 degree Celcius) and the W-** number is the viscosity at 100 degrees celcius, So typically the standard average running temp of all engines.
    Last edited by Splint; 2019/08/16 at 09:13 AM.

  17. The Following 5 Users Say Thank You to Splint For This Useful Post:


  18. #11
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Re: My FYI Thread.

    Not sure if anyone would be interested in a "sensor" post... not PG16... Engine sensors. If I see interest I will gladly post.

  19. The Following 5 Users Say Thank You to Splint For This Useful Post:


  20. #12
    Join Date
    Apr 2019
    Location
    Midrand
    Posts
    110
    Thanked: 175

    Default Re: My FYI Thread.

    These are great posts - thank you!!

  21. The Following User Says Thank You to heyyahhey For This Useful Post:


  22. #13
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Sensors

    In order to get your car ECU to understand the environment it needs to know certain values to ensure that it fuels the correct amount, fires the sparkplug at the right time (petrol engines) or when exactly to inject the diesel. it is all about when and how much.

    The most common sensors used to achieve the above on modern engines are:
    Mass Airflow Sensors
    Manifold Absolute pressure sensors
    Throttle position sensors
    Crank angle sensors
    cam position sensors
    air temperature sensors
    water temperature sensors
    Knock sensors


    Mass Airflow Sensors or MAF Sensors are used to measure the amount of air that passes by it to determine the ratio of fuel needed to run a clean combustion. Too lean and you will cause detonation, and high EGT too rich and you will overfuel. So it is important that the MAF is in perfect order to ensure it measures the correct amount of air intake.

    So how does it work? There are a few different types of MAF sensors, but the most common used today is the hotwire mass airflow sensor. This has a wire that is heated to a certain temperature. This temperature is measured by the ecu. As air flows over the wire, it is cooled down and the ecu will increase the current in order to maintain the heat. This current therefore goes higher as more air flows over the wire. The current is converted to digital form which the ECU can interpret. The ECU now uses these values to determine how much air is flowed into the intake system and it will then fuel accordingly.
    MAF sensors are extemely delicate items though, so it is important to understand how these can affect the performance of an engine. Typically a MAF sensor will not completely fail, it will depreciate its values. These are quite a few things that can cause this, one being dirt that passes through the unit can build up residue on the hotwire. When this happens the air that flows over the wire does not affect the cooling of it as it should and therefore the wire will remain warm even if higher airflow is present and your ecu will not fuel the correct amount simply because it does not get the correct values. Other issues can be degrading electronics, particles that passes through the system and damaging the MAF etc. Can you test if your MAF is working correctly? Yes, there are loads of OBDII tools that can show you the values of your MAF sensor. These are usually tested at 3 different RPM levels, 1000, 2000, 3000rpm. Keep in mind different engines have different air intake values.
    However the principal is simple. airflow is measured at g/s or Grams per second. So here is an example (note these are made up values and are purely used as an example)
    if your engine at 1000rpm and produces 2.0g/s airflow. this means at 2000rpm it should produce about double that amount and at 3000rpm it should produce the amount 3 times. So using this example, the values for this dummy engine should be as follows:
    1000rpm = +-2.0g/s
    2000rpm = +-4.0g/s
    3000rpm = +-6.0g/s

    a faulty MAF sensor on the otherhand can produce less than half at each rpm range or even remain at around the same g/s as it were at 1000rpm.

    MAP sensors or Manifold absolute pressure sensors can be used as a standalone sensor, but it is mostly used to even more verify the air intake. MAP sensors are used to determine the pressure inside the intake manifold. By pressure we obviously mean both positive pressure and negative pressure (Boost and vacuum) These readings are measure in psi or bar and the ecu determines how much to fuel accordingly. The map sensor can also determine if there is underboost or overboost occuring in the system. Map sensors can also depreciate in value so it is important to keep them clean and if any faults occur it is best to replace them with the same part. MAP sensors all serve the same purpose, but they are designed differently, so do not swop out MAP sensors with parts that will fit but not made for your vehicle. Though it can in some instances improve performance if a replacement part is a better version of it, but in most cases it will decrease performance, so do your research before you swop interchangeble parts.

    TPS or Throttle positioning sensors are used with a map in the ecu that will determine the position of the throttle. In some instances this can be the only sensor used to determine how much to fuel, but it is not a really good standalone sensor as we do not measure the airflow, it is simply based on the position of the throttle. Therefore it is better to use another sensor along with it, like MAP or MAF or both. Keep in mind, Diesel engines do not have throttle positioning sensors because they do not have throttles. Throttle positioning sensors can depreciate in value as they have moving parts, they can be tested with OBDII tools and you can even calibrate some of them by giving it the closed throttle position or WOT (wide open throttle) position.

    Crank angle sensors as used to determine the angle of the crank. Typically you will have the crank angle at the same position twice in a cycle. So to explain on a 4 cylinder motor. you will have TDC on cylinder 1 and 4 twice. The first rotation is when cylinder 1 is on the end of its firing stroke, where the next cycle will be where cylinder 4 is on its fireing stroke. The purpose of the crank angle sensor is purely to determine this position, no matter which one of the 2 cycles it is in, as long as it knows when top dead center will occur, the reason for this is simple. To get from top dead center to top dead center only occurs in a single crank rotation, it is the cam cycle which is at half the engine speed where 2 cycles would need to occur in order to allow the entire 4 strokes to occur.

    intake stroke (from tdc to bdc)
    compression stroke (from bdc to tdc)
    firing stroke (from tdc to bdc)
    exhaust stroke (from bdc to to tdc)

    Cam sensors fine tunes this a little more. The are now used to determine the position of the cam. So if 1 cycle completes for the crank the crank angle sensor tells the ECU it's postition but only half a revolution ocurred for cams, so now the cam sensor can tell the ECU the position of the cam. This allows the ecu to know exactly when it is going to be on TDC for any cylinder, but not only that, it now also knows which stroke that cylinder is at. Cam sensors are mostly used with more modern engines where they no longer use a waste spark or wasted fuel system and each cylinder can receive fuel and spark at the correct time. It is important to understand that both crank angle and cam position sensors needs to know its correct positions. This is the reason why so many of today's vehicles requires a timing tool set to ensure that each cam and the crank are exactly where they should be. If this is wrong, the engine will not start, or misfire or just perform horrible and even worse, you can make roof nails our of your valves.

    Air temperature sensors.. Because ambient air temperatures differ and this makes a big difference to the way your car fuels, some cars use air temp sensors in the intake system. Some of these are built into the MAF sensor, where others are on its own in the system. The reason for these sensors are to test the temperature of the air in the intake system, hotter air will expand less when it enters the cylinder and requires less fuel where colder air expands more and requires more fuel. It is important for the ECU to know these temperatures as this makes a difference to the performance of the engine and it can also prevent engine killing detonation. These sensors again degrade in value over time as residue built up. This can cause some overfueling as the ecu gets the incorrect values from the sensor. They can often be cleaned, but are not usually expensive and can be replaced.

    Water temperature sensors. These sensors are usually situated on the head somewhere and they perform a very important role as well. They do not tell the fan to come on, but they also measure the temperature of the water to determine how much fuel are required, similarly to the air intake temperature sensor. If these sensors are faulty, they can tell the ECU that the engine is still cold and the ECU might overfuel. This happens more often than people think. Some very common reasons these sensors fail is because of people not maintaining their antifreeze and the water causes rust in the engine and this builds up on the sensors.

    Knock sensors performs a very important role. When detonation occurs on the engine it means you are either underfueling or your timing is incorrect as some of the symptoms. These symptoms are not only caused by issues on the vehicle's sensors or injectors etc, but also by ambient temperature changes, type of fuel etc. What this sensor does is to detect detonation or knocking also known as pinging. When knock is detected, it will send a signal to the ecu, the ecu will then retart some timing and fuel a little more until the knock is no longer detected.

    Keep in mind that with todays vehicles failsafe is usually built into the ecu. This is where limp mode is very important, it might be irritating, but it saves your engine. Limp mode includes, but not limited to retarding timing, overfueling and rev limiting. These features allows you to drive, really slowly, but you can get somewhere safe without damaging the engine.

  23. The Following 14 Users Say Thank You to Splint For This Useful Post:


  24. #14
    Join Date
    Aug 2013
    Location
    Tesselaarsdal (dis inni Kaap!)
    Age
    59
    Posts
    948
    Thanked: 533

    Default Re: My FYI Thread.

    Very informative to an old-school bush mechanic like me... Subscribed!
    ENJOY!!!
    Ettienne

    196? S2B FC "Over Lander" Camper
    1975 Land Rover Air-Portable Lightweight
    1980 Range Rover
    2002 Defender Td5 D/C
    2004 Disco Td5

  25. The Following 2 Users Say Thank You to EttiennedK For This Useful Post:


  26. #15
    Join Date
    Feb 2012
    Location
    Bloubergrant
    Age
    54
    Posts
    408
    Thanked: 110

    Default Re: My FYI Thread.

    Really informative thread, thank you for sharing your wealth of knowledge.

    I would love to hear your comments on the functionality of the EGR valve. I know it is good for the emissions control, but is it good advice to blank off?
    Then can a Suction Control Valve be "cleaned". Saw a video of a person cleaning the SCV with water paper at the end of a drill (the round valve part)

    My old school 3.2 Triton surges sometimes, apparently SCV trouble.
    Mitsubishi Triton DC 3.2 A/T 4X4
    2007 Hilux 2.5 D4D SOLD

  27. #16
    Join Date
    Feb 2009
    Location
    Pretoria
    Age
    58
    Posts
    66
    Thanked: 5

    Default Re: My FYI Thread.

    Great information, thank you.

  28. The Following User Says Thank You to ColinStier For This Useful Post:


  29. #17
    Join Date
    Mar 2008
    Location
    De Wildt
    Age
    56
    Posts
    34,512
    Thanked: 9670

    Default Re: My FYI Thread.

    @Splint: Can I suggest that you maybe explore the different effects on diesel and petrol engines when it comes to rich and lean conditions?

    Many members do not know the difference.

    And then maybe later do a post on turbo aspect ratios, and the effect on the lag time and air flow limits.
    2012 Jeep Sahara Unlimited 3.6 V6
    Percivamus

  30. #18
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Re: My FYI Thread.

    Quote Originally Posted by Johan Engelbrecht View Post
    Really informative thread, thank you for sharing your wealth of knowledge.

    I would love to hear your comments on the functionality of the EGR valve. I know it is good for the emissions control, but is it good advice to blank off?
    Then can a Suction Control Valve be "cleaned". Saw a video of a person cleaning the SCV with water paper at the end of a drill (the round valve part)

    My old school 3.2 Triton surges sometimes, apparently SCV trouble.
    Sure thing. I will post about EGR valves as well. There is a bit of misperception around them so it is a good idea. As for the SCV, yes they can be cleaned, but I am a little sceptic going in the with a drill and sand paper as the clearances are very tight. The unit gets lubricated quite well with diesel so the chances it will stuck is little, it might have high resistance accross the connections though which would require you to replace it.

    I would however just take it off, pray some carb cleaner in and shake, do this a few times, then just rinse with some diesel. If the engine still has surges or weak acceleration, or rough idle I would just replace it. they are relatively cheap.

  31. #19
    Join Date
    Aug 2019
    Location
    Cape Town
    Age
    42
    Posts
    70
    Thanked: 88

    Default Re: My FYI Thread.

    Quote Originally Posted by jelo View Post
    @Splint: Can I suggest that you maybe explore the different effects on diesel and petrol engines when it comes to rich and lean conditions?

    Many members do not know the difference.

    And then maybe later do a post on turbo aspect ratios, and the effect on the lag time and air flow limits.
    Sure thing bud. I will do a post on fueling as well as fuel quality. I just need to finalise a post around carbon buildup as per another request.

    I was planning on doing a more extensive post initially on turbo sizing, housings, compressor wheels, flow maps etc but I was not sure if it was going to be too much information, but seeing as you request it, I will surely do so.

  32. #20
    Join Date
    Jan 2014
    Location
    Pretoria
    Age
    43
    Posts
    28
    Thanked: 15

    Default Re: My FYI Thread.

    Very informative, thanks for sharing- Subbed

    Opinion on a MAP sensor please? The vehicle doesn't have a MAF only a MAP - When plugged in the motor behaves badly, rough idling, lack of power, etc. but runs smooth unplugged. I have replaced the MAP with OEM but still the same behavior. OBD points to MAP error.

    We now just run with MAP unplugged - could there be risk of damage?

    Thanks Again
    Shaun
    See it - Plan it - Believe it - Do it

Page 1 of 3 1 2 3 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •