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Anyone noticed this before? I have minimal experience with ATI dampers but I noticed this while setting one up on a customer's motor today. It appears that ATI's crank wheels are keyed half a tooth off of OEM. The TDC marks are correct (verified piston position), but the teeth themselves are 1/2 teeth off, which means that both cams are either advanced or retarded roughly 7 crank degrees from the OEM config, depending on how you time the engine.
ATI damper. TDC mark is lined up with the high point on the teeth:
OEM crank gear, TDC mark is lined up with the low point on the teeth:
Where is the woodruff key aligned on the ATI? The rear belt guide is a separate piece, right? Maybe it's just the mark that's wrong and not the keyway?
I've never actually checked mine (and don't have any photos), but I would have thought that if the motor really was mis-timed by that much then it wouldn't run as well as it does.
OK. I tend to find TDC with a screwdriver rather than by looking at the marks (I don't trust the plastic cover, and once the ATI is installed it's really hard to get that cover off to see the mark on the belt guide.
I did find a photo of me checking the cam timing:
The intake gear is lined up, but it's an adjustable Toda and I don't know how much trust to put in the nominal "zero" on it. The one on the right is an OEM gear and it does not appear to be half a tooth off.
Mine look like that if I retard the crank by 7 degrees. Both marks line up perfectly as they always do with the OEM gear. If I set the motor to TDC, neither mark lines up - they're both in between teeth.
The ATI is definitely "wrong", the question is whether it was intentional to change the power curve or whether it was an oversight.
Yikes. I have two here, I checked the other before posting this. Also checked three different OEM gears just in case I had an oddball there. Both of the ATIs are the same, as are all 3 of the OEMs.
Mines the same as Ted75zcar. So I guess they do have a bit of QC problem.
EDIT: Clearer picture. Mine looks to be about 1-3° off. Flange notch is inline with keyway. This unit is about 1-2 years old and I can't identify anything I would call a lot code.
Wow thanks for pointing that out Savington - I just checked my OEM and my brand new in box ATI, and yes, they are in fact offset from another.
So what are the implications of this? Compensate in megasquirt? Would a timing light help figure it out?
well, I believe the Cam timing will be off. You can't really compensate with MS (well, intake with VVT). You could possibly use adjustable cam gears, but then VVT again on intake side. If I had a new one like that I think I would ask ATI what is up, and if they didn't have a really good answer I would ask for a good one or my money back.
Wow thanks for pointing that out Savington - I just checked my OEM and my brand new in box ATI, and yes, they are in fact offset from another.
So what are the implications of this? Compensate in megasquirt? Would a timing light help figure it out?
You could just adjust the base timing, no? A timing light would not help AFAIK because it would key off of the trigger wheel, which would be aligned to the timing mark. You would need to measure the true geometric offset between the timing mark and the teeth and compensate accordingly.
The amount of high $ aftermarket **** that shows up on this forum that has glaring issues is staggering. There are tons of people running stupid power on OE crank balancers, it gets you thinking.
I just remembered that because a timing light is used to set initial timing, the offset won't hurt the spark timing aspect on the NA6/8 setups. But it could really change the powerband of the cams up or down. 4 degrees advanced or retarded makes a difference so I wonder how much more up to 7 can do. Very interesting.
^ that's assuming that the timing wheel aligns correctly to the keyway on the crank, since spark is timed off the timing wheel.
There are three independent things that must all line up for timing to be correct:
1) the keyway on the cog and crank (true crank position)
2) the teeth for the belt (cam positions)
3) the timing wheel (crank sensor position)
The timing mark doesn't really even matter as long as everything lines up to #1 (keyway). But in post #3, Sav said that he check everything vs. actual TDC, and the teeth are indeed off.
My question- does #3 (timing wheel) line up correctly to the keyway?
Thinking this through, the timing mark doesn't really even matter as long as everything lines up to #1 (keyway). It's possible that the timing mark is off, but everything else is fine.
So question back to Sav- what is the relative position of #2 (teeth) and #3 (timing wheel) relative to #1 (keyway)?
He's already shown that the cam timing issue is relative to the keyway, not just the TDC mark. Also, in the ATI product photo I posted above, you can actually see that the keyway isn't lined up with a cog 'valley' like on the OEM gear.
03-15-2018, 05:32 PM
Incorrect tooth clocking on ATI dampers
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