OK I see what you're asking. The intake air pressure sensor tells the ECU that the engine is on the intake stroke.Fatallybitten said:
Another valve check problem
- Thread starter Fatallybitten
- Start date
Fatallybitten
Member
Great! That means I can put it back together now. It will be a few days before I have the time to do it, but I will report back once I have it all done. Cheers.
I think others have covered it, but I'll take a shot to help clarify.
Without the camshafts connected, there isn't a after-compresion-stroke TDC and after-exhaust-stroke TDC. There is just 360-deg of crankshaft rotation that brings each piston to a single TDC. It is the process of timing the camshafts (which run at half crankshaft speed) that establishes the two TDC's . So put the crankshaft in the position it is supposed to be and then time the cams correctly and you should be good to go. Once you've timed the carms, then yes, there are two TDC's for each cylinder and you need to pay attention to which one you're on when doing things like checking valve clearances.
Most engines have a camshaft position sensor in addition to a crankshaft position sensor which helps the ECU know which TDC the engine is at for each cylinder to optimize spark and fueling. I can't find one for the S10, so I'd guess that each cylinder receives fuel and spark on both strokes. It is common to have a wasted spark on many engines and I understand that fuel injection timing is mostly a duration thing rather than a precise instant thing, but this still surprises me a bit. Someone mentioned that maybe they can detect the two TDC's by intake tract pressure. I've never heard of this being done, but don't really know.
- Mark
Without the camshafts connected, there isn't a after-compresion-stroke TDC and after-exhaust-stroke TDC. There is just 360-deg of crankshaft rotation that brings each piston to a single TDC. It is the process of timing the camshafts (which run at half crankshaft speed) that establishes the two TDC's . So put the crankshaft in the position it is supposed to be and then time the cams correctly and you should be good to go. Once you've timed the carms, then yes, there are two TDC's for each cylinder and you need to pay attention to which one you're on when doing things like checking valve clearances.
Most engines have a camshaft position sensor in addition to a crankshaft position sensor which helps the ECU know which TDC the engine is at for each cylinder to optimize spark and fueling. I can't find one for the S10, so I'd guess that each cylinder receives fuel and spark on both strokes. It is common to have a wasted spark on many engines and I understand that fuel injection timing is mostly a duration thing rather than a precise instant thing, but this still surprises me a bit. Someone mentioned that maybe they can detect the two TDC's by intake tract pressure. I've never heard of this being done, but don't really know.
- Mark
RIVA
Well-Known Member
Putting in my 2 cent. I think the real question is Is there a wasted spark at TDC. If there is a wasted spark then the original question is not relevant but if there is not a wasted spark then the question is very relevant. As to the answer I do not know. ::010::
I don't know specifically about the S10, but most motorcycles use wasted spark systems that fire the plugs even on the after-exhaust-stroke TDC where the spark does essentially nothing. There is no downsiide and it makes things simpler.RIVA said:
But I'm less sure of whether injecting fuel continuously without respect to the timing of what stroke the cylinder is on is commonly done. Again, camshaft position sensors are common and provide the extra piece of information that tells the computer what stroke the cylinder is on, removing the ambiguity that you have with only a crankshaft position sensor. I thought the S10 probably had one, but I can't find any reference to it in the service manual.
- Mark
There should be no wasted spark or fuel injected.The ECU knows when the cylinder is on the exhaust stroke.
Take an old bike with points like a 750 Honda or 900 Kawasaki, cylinders 1&4 hit TDC at the same time, one on compression stroke and the other on exhaust stroke. The points ran off the crankshaft with one set of points running both cylinders, you had spark every 360* turn of the crank. Same with 2&3. When they moved on to CDI ignitions you had two spark units on a four cylinder engine. The spark units took the place of a set of points and sent a signal to the CDI box to fire that coil, one cylinder on compression and still having a wasted spark on exhaust. An engine like a Honda 350 twin had two sets of points running off the cam shaft so they only fired on TDC of the compression stroke. All the singles like the Honda 50, 80 and 100 XR's have the points/spark unit on the crank and waste a spark on the exhaust.
Take an old bike with points like a 750 Honda or 900 Kawasaki, cylinders 1&4 hit TDC at the same time, one on compression stroke and the other on exhaust stroke. The points ran off the crankshaft with one set of points running both cylinders, you had spark every 360* turn of the crank. Same with 2&3. When they moved on to CDI ignitions you had two spark units on a four cylinder engine. The spark units took the place of a set of points and sent a signal to the CDI box to fire that coil, one cylinder on compression and still having a wasted spark on exhaust. An engine like a Honda 350 twin had two sets of points running off the cam shaft so they only fired on TDC of the compression stroke. All the singles like the Honda 50, 80 and 100 XR's have the points/spark unit on the crank and waste a spark on the exhaust.
I just looked at the mx manual.
The crankshaft position sensor is very straightforward and everything the ECU knows about crank and cam position is derived from it. I say derived because an assumption is that the cams have been set to the timing marks on installation while the #1 piston is set to TDC.
The book does not say whether or not there is a lost spark or not. But since the ECU works on the assumption that the cams have been properly timed to the crank, there does not need to be a lost spark. While I wouldn't rule out a lost spark, my own guess is that OldRider is right in that there is none. After all, it's a capacitive discharge system and this allows better charging of the capacitor for the discharge.
The injection system is fairly simple, as in nearly all motorcycles these days. The injectors are in the intakes, not directly at the ports, and the manual says the fuel is controlled very similar to a carbureted system with the timing of the injectors is in relation to the throttle body positions. This all means that as with a carb, the injector for each cylinder does not deliver only when the valve is opening. It makes sense from a business stand-point of mass production too, as it takes a little more engineering but is cheaper to manufacture.
There is no cam or other position sensor and the decompression is purely mechanical.
Fatalybitten can turn it through, do his checks, and button it up.
::003::
The crankshaft position sensor is very straightforward and everything the ECU knows about crank and cam position is derived from it. I say derived because an assumption is that the cams have been set to the timing marks on installation while the #1 piston is set to TDC.
The book does not say whether or not there is a lost spark or not. But since the ECU works on the assumption that the cams have been properly timed to the crank, there does not need to be a lost spark. While I wouldn't rule out a lost spark, my own guess is that OldRider is right in that there is none. After all, it's a capacitive discharge system and this allows better charging of the capacitor for the discharge.
The injection system is fairly simple, as in nearly all motorcycles these days. The injectors are in the intakes, not directly at the ports, and the manual says the fuel is controlled very similar to a carbureted system with the timing of the injectors is in relation to the throttle body positions. This all means that as with a carb, the injector for each cylinder does not deliver only when the valve is opening. It makes sense from a business stand-point of mass production too, as it takes a little more engineering but is cheaper to manufacture.
There is no cam or other position sensor and the decompression is purely mechanical.
Fatalybitten can turn it through, do his checks, and button it up.
::003::
Fatallybitten
Member
Checkswreck, your comment:
"The crankshaft position sensor is very straightforward and everything the ECU knows about crank and cam position is derived from it. I say derived because an assumption is that the cams have been set to the timing marks on installation while the #1 piston is set to TDC."
I believe you meant the cams are timed with the crank at the K mark, 71 degrees before TDC on cylinder 1.
"The crankshaft position sensor is very straightforward and everything the ECU knows about crank and cam position is derived from it. I say derived because an assumption is that the cams have been set to the timing marks on installation while the #1 piston is set to TDC."
I believe you meant the cams are timed with the crank at the K mark, 71 degrees before TDC on cylinder 1.
WJBertrand
Ventura Highway
The use of a lost spark is done on engines that have an even firing order so that they can use fewer coils. On a conventional flat crank four, the cylinders are paired to use a single coil. Two of the four pistons reach TDC at the same time, one on the power stroke and the other on the exhaust stroke. Since these are neatly 360 degrees apart, the manufacturer can just make the coil fire every 360 degrees. Similarly the other set of pistons are paired to fire every 360 degrees, 180 degrees out of phase with the first pair (again assuming a flat crank four). This saves the expense of coil for every cylinder. This works for a conventional I4 or V4 engine (with the sets of coils firing 90 and 270 degrees apart), but I don't think that works for cross-plane crank like the Super Tenere or the R1 for that matter. Since our bikes actually have four coils, there would not seem to be the need for a waste spark in one cylinder while the other was firing. Seems like that might actually cause some problems as the other cylinder might not be on an "inert" exhaust stroke.
Fatallybitten said:
True because the crank sensor is also set to a "K"
As for releasing the cct... per the manual I used a screwdriver but no way to do it my just pushing on it like in the illustration.. I had to pop the screw driver with the palm of my hand to get the cct to pop and tighten the chain.
Attachments
If the only info the ECU has about the rotational state of the engine is the crank position sensor then the ignition system has to be wasted spark and the fuel injection must work without respect to valve timing. There is really no other way to do it.Checkswrecks said:
- Mark
There is nothing about a 270-deg crank or separate coils that discourages (or encourages) wasted spark. The ECU knows exactly what position the crank is in at all times, so it can be programmed to fire the individual coils for each cylinder at whatever time is optimal. But, as we have been discussing, while the ECU may know the position of the crankshaft and piston, it doesn't know the position of the valve train so it would need to fire on every crank revolution, twice per four-stroke cycle, to be sure it fired at the beginning of the power stroke.WJBertrand said:
- Mark
FYI, here is an interesting article about an engine design that senses what stroke the engine is on by electrical characteristics of the ignition system. I doubt the S10 uses such a system, but perhaps there is something going on here we don't know about.
https://www.motor.com/magazinepdfs/112004_11.pdf
- Mark
https://www.motor.com/magazinepdfs/112004_11.pdf
- Mark
What about the injectors spitting a load of gas in on the exhaust stroke? If it knows when to and when not to fire the injectors, it also know when to fire the plug. :question:markjenn said:
Wasted spark is essentially no consequence with respect to ignition (other than wear/tear on the spark plugs and coils due to the extra firing cycle), but there are advantages to knowing the valve timing with respect to when to inject fuel so as to time it so the fuel arrives at the intake port about the time when the valve opens. But from what I've read, it is not critical for a non-direct-injected (e.g., throttle body) engine as there is a lot of fuel/air mixing occurring throughout the inlet tract and precise timing of the fuel injection event with respect to the valve timing is a matter of optimization rather than necessity. In any event, we still have no plausible explanation of how the S10 figures out the positions of its valves, so it appears to me that it must be a wasted-spark system with fuel injection which is untimed with respect to the valvetrain position.OldRider said:
- Mark
What about the "intake air pressure sensor"? It can sense when the intake valve opens.markjenn said:
"An engine control apparatus is disclosed for determining crankshaft position and engine phase of an internal combustion engine through monitoring intake air pressure fluctuations. The opening of the intake valve is mechanically linked to the crankshaft position of an engine. When the intake valve opens it creates air pressure fluctuations in the air induction system of the engine. The control apparatus is configured to determine intake air pressure fluctuations indicative of an intake air event and thus a particular crankshaft position, and their corresponding period of the engine cycle. The controller then uses this information to determine crankshaft speed and position for the purpose of fuel injection and ignition timing of the internal combustion engine. Engine phase is also determined on four-stroke engines. The engine may also include a crankshaft position sensor in combination with monitoring intake air pressure fluctuations to increase resolution in determination of crankshaft position. A circuit is provided for simultaneously measuring intake temperature using a single bridge type pressure sensor in order to calculate air mass flow rate."
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WJBertrand
Ventura Highway
It would be surprising to me if Yamaha were using a "waste squirt" from the injectors similarly to a waste spark. Any kind of wast squirt would seem to have quite negative effect on both fuel mileage and emissions.
Sounds like the quote is from a patent application.OldRider said:
While it is certainly possible Yamaha is using something like this, I doubt the sensor provided in the S10 would be suitable - you'd probably need to have a sensor in the actual inlet tract of each cylinder, not something in the airbox. I think the S10's sensor is mainly to trim the fuel injection settings for air density and has nothing to do with trying to figure out the timing of intake valve opening. Could be wrong.
- Mark