10-02-2019, 11:12 PM
pekingduck is making the correct point (in a lot fewer words than I did).
Also, I'm certain the system is not programmed to inject fuel into a closed port--even a carburetor works smarter than that.
Whatever Honda figured out, it's very clever. I'd love to get to the bottom of this. The mechanics at the local Honda shop are also scratching their heads after I mentioned the issue yesterday while buying some oil. Maybe I can get one of them to make a call to a corporate tech guy.
For the sake of being complete, here's what got me thinking about the issue.
When the cams come out, you have to pull at least one of the cam sprockets off as there is not enough slack in the cam chain, even with the tensioner backed all the way out, to remove the cams with the sprockets on. To get a sprocket off, you have to pull one of the two sprocket bolts out (you start with the cam timing marks at #1 TDC on the compression stroke to access the first bolt) then turn the crank by hand one full cycle to expose the second bolt on the opposite half of the sprocket. You are now at #1 TDC exhaust stroke. Once both sprocket bolts are off, you can work the sprocket loose to one side and pull the cam all the way out through the sprocket hole.
Handy tip for first-timers: You only need to remove the sprocket from the intake cam--there is plenty of slack in the chain to get the exhaust cam out with its sprocket still on once the intake cam is out. The intake one has to come off because it's on the slack side of the chain.
The first two times I adjusted valve clearances, I dutifully turned the crank over one full cycle with the cams out (back to what was #1 TDC compression stroke) before reinstalling them with their timing marks in the correct position. You then have to turn the crank one more cycle to get the second sprocket bolt back in.
This time, I got to thinking the ECM can't be counting crank cycles to figure the cam timing--the battery isn't even hooked up! I put the cams in 180 degrees out of phase from how they came out (due to the one full crank turn to get the second sprocket bolt out). I figured as long as #1 was TDC on the crank and the timing marks on the cams were correct, it should work. Sure enough, it fired right up once reassembled.
Again, how the does the ECM determine cam position solely from the CKP? For every turn of the crank, the cams only turn 1/2 cycle. In other words, for every possible crank position, there are two possible cam positions, and the fuel injector timing depends on the cam position.
Also, I'm certain the system is not programmed to inject fuel into a closed port--even a carburetor works smarter than that.
Whatever Honda figured out, it's very clever. I'd love to get to the bottom of this. The mechanics at the local Honda shop are also scratching their heads after I mentioned the issue yesterday while buying some oil. Maybe I can get one of them to make a call to a corporate tech guy.
For the sake of being complete, here's what got me thinking about the issue.
When the cams come out, you have to pull at least one of the cam sprockets off as there is not enough slack in the cam chain, even with the tensioner backed all the way out, to remove the cams with the sprockets on. To get a sprocket off, you have to pull one of the two sprocket bolts out (you start with the cam timing marks at #1 TDC on the compression stroke to access the first bolt) then turn the crank by hand one full cycle to expose the second bolt on the opposite half of the sprocket. You are now at #1 TDC exhaust stroke. Once both sprocket bolts are off, you can work the sprocket loose to one side and pull the cam all the way out through the sprocket hole.
Handy tip for first-timers: You only need to remove the sprocket from the intake cam--there is plenty of slack in the chain to get the exhaust cam out with its sprocket still on once the intake cam is out. The intake one has to come off because it's on the slack side of the chain.
The first two times I adjusted valve clearances, I dutifully turned the crank over one full cycle with the cams out (back to what was #1 TDC compression stroke) before reinstalling them with their timing marks in the correct position. You then have to turn the crank one more cycle to get the second sprocket bolt back in.
This time, I got to thinking the ECM can't be counting crank cycles to figure the cam timing--the battery isn't even hooked up! I put the cams in 180 degrees out of phase from how they came out (due to the one full crank turn to get the second sprocket bolt out). I figured as long as #1 was TDC on the crank and the timing marks on the cams were correct, it should work. Sure enough, it fired right up once reassembled.
Again, how the does the ECM determine cam position solely from the CKP? For every turn of the crank, the cams only turn 1/2 cycle. In other words, for every possible crank position, there are two possible cam positions, and the fuel injector timing depends on the cam position.