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Not sure if this is what you were asking, but there are several configurations where there are no lifters (or at least, no push-rods) in an engine, where the valves are driven either through rocker arms or directly by the camshaft(s). Such a configuration is an OHC (overhead cam) configuration. SOHC are higher performance and lighter (and so typically have a ...
7
In addition to Zaid's answer.
VTEC - Variable Valve Timing and Lift Electronic Control)
In essence, it selects between two different cam profiles depending on the RPM.
Here's an animation -
This is how a cam controls poppet valves. Read about cam profile here
For volumetric efficiency we want the intake stroke to fill the cylinder with the max - air-...
6
I'm assuming you have a 4 cylinder.
You need to remove the valve cover. If the valves are adjustable then unadjust them until all the valves are free. Remove the spark plugs. Use a leakdown tester to induce compressed air into the cylinders. The tester will shows the amount of leak down and where it is coming from. If it's coming out of the tail pipe then ...
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Surely, to get a Subaru (or any true boxer engine) to run in this kind of configuration is relatively easy. Bear in mind that you are talking about an engine with two horizontally opposed cylinder heads and a four stroke so for each revolution of the camshaft, there are two revolutions of the crankshaft. Each piston hits it's "top" of it's travel twice, ...
6
This diagram does a decent job of explaining VTEC:
In a nutshell (paraphrasing the Wikipedia article), you have two cam profiles, one designed for low-RPM operation and fuel efficiency, the second (taller cam) for performance. The ECU decides when to select which profile based on several engine parameters by actuating the locking pin that runs through the ...
5
Do any of the four cylinder car guys out there run this configuration?
Not that I can find, with the simulated exception of some "scatter cams" referenced by @Steve Matthews, and given a great answer by @Paulster2. Although these are not really "Big Bang" by strict definition.
Here is a link to a really good read even though it's only marginally appropos!
...
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First, remember that we are talking about four different engine cycles here: Intake; Compression; Ignition/Combustion; Exhaust. Top dead center (TDC) happens between two of these cycles: between Compression and Combustion, then again between Exhaust and Intake. The reason the piston and valve do not come into contact is because either the piston is following ...
4
If the inlet valve opens 20 deg before TDC, will fresh mixture be going in or not? As there is still pressure in the cylinder - the exhaust leaving is helping to "draw" the fresh mixture into the cylinder, so a wasted spark has no "new" or very little mixture to fire so it doesn't happen.
Also, the engines designed with wasted spark ignition may not have ...
4
The best way to test to see if your engine is timed correctly is to rotate the crank shaft through 720° of rotation then check your timing marks again. Since you (supposedly) have a non-interference motor, you will have no worries. If the marks line up again, then you're golden. You'll want to do this with a crank snout socket or put the harmonic balancer ...
4
The P0018 code is related to your cam and crank showing incorrect timing
There are two sensors involved in this error.
Cam Position Sensor
Crank Position Sensor
These two sensors detect the angle of rotation of each shaft and when they fall out of tolerance in timing, you get this error.
There are multiple reasons why your crank and your cam(s) may be ...
4
Most probably the sound is from a loose TAPPET in the cylinder block, usually it goes away after a few thousand kilometres but if it still persists then you need to open up the header and tighten the tappets with the help of the mechanic.
Its not advisable to DIY.
And No this is not a very serious issue. My personal bike had the same issue from day 1 and ...
3
The wasted spark will likely be 30 degrees or so before TDC. There would be no fresh fuel charge at this point.
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Bottom line is: It's been done.
Here's one for a small block Chevrolet engine:
Just as you describe, there's an idler gear (well, maybe two) which keeps things in time.
These gears are used mostly in racing applications. They aren't usually used in street applications for two reasons:
Cost - These cost anywhere from four to ten times the amount of a ...
3
As Brian commented, your question and the information we have is a little vague.
Not repaired already:
It won't drive at all if the timing chain is broken. No amount of cranking the engine will start it. For this year/make/model it would probably be cheaper to either purchase another vehicle or swap in a low mileage engine than repair the current one.
If ...
3
Tick Tick Sound you here during Idling is from Auto De-compressor. This Auto Decomp starts functioning below 350RPM. If RPM is raised this sound should vanish (This is applicable for new UCE engines).
In these Engines you also here some time Tick Tick sound after running the bike for few kilometers / engine warms up. This is basically maybe coming from the ...
3
Question 1: This depends on engine design.
In an interference engine, the valves can collide with the pistons, so you need to design the timing diagram to prevent that.
In non-interference engines, there is sufficient room in the combustion chamber that the valves will never collide with the piston.
Question 2:
As @Paulster2 says, we're talking about a ...
3
In 1987 vehicle manufacturers were struggling to meet the emissions standards
Valve overlap, while a performance gain, is not necessary for an ICE to run properly. Valve overlap will allow un-burned fuel to scavenge the combustion chamber of carbon dioxide to ensure a well oxygenated air/fuel charge.
Emissions standards drive much of the engine and ...
2
While I don't have an answer regarding blocking or stopping the cam, You can work around it without too much trouble.
With the chain still in place, You can mark on the crank and cam gear teeth and mark the chain around those teeth. This way you will know how many links should be between the marked parts of the pulley when you are done. Taking lots of ...
2
I know this question is old, but I thought I'd provide some feedback for future.
Cam phasers make noise due to a lack of oil pressure in two cases:
The inner rotating piece connected to the cam shaft contacts the static* outer piece connected to the sprocket/pulley. This will be loud especially at high engine speeds. This means the phaser is getting no oil,...
2
I think I'd first be doing a compression test here just to help perhaps rule out an internal engine problem like a burnt valve etc. Assuming pressures are good though... I'd then be considering pulling the cylinder head to properly see what's going on in that area.
Not only does the lifter looked gummed-up but that rear cam bearing housing looks like it's ...
2
Short answer: follow the money.
Long answer. Cutting gears and ensuring the mesh correctly is incredibly expensive. You've got to rough form, final form, heat treat then final form again. Then you have to emplacement the mating gears to extraordinary tolerance. Add extra bearings for the idler... never mind the real estate inside the engine for the ...
1
There may be a position where the chain can slip and there will be no damage, but will it have happened there?
So possibilities:
Use a camera through the plug hole to investigate for contact
You can take the head off to see if there is any evidence of contact
Conduct a pressure test on each cylinder - any leaking valves become evident usually
Or just ...
1
On a 4-stroke engine, when #1 is at TDC, it's at TDC. It doesn't matter at that point if the cam(s) are not connected. Once you align the cam timing mark(s), then you'll set which stroke you are on.
Caveat:
Be careful when you're setting the timing and moving the crank without the cams connected. You run the distinct risk of damaging something if it is an ...
1
What I have found with some OHC interference engines is that there are special dealer tools to hold the cam. They usually bolt to the head and have pins that slide into holes on the cam gear. I usually just build a tool that does the same thing when needed. If you post a pic of the front of your engine, we might be able to point out ways to attach such a ...
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How about substituting one quart of motor oil with Marvel Mystery Oil? You may have a little varnish somewhere on a valve lifter, valve stem, oil pump, etc.
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