Incorrect tooth clocking on ATI dampers
 

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:

Attachment 229365

OEM crank gear, TDC mark is lined up with the low point on the teeth:

Attachment 229366

Buh.

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.

--Ian

I thought the same, first thing I did was throw a dial indicator on #1 piston and verify true TDC, The mark is correct, the teeth are off.

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:

http://www.codrus.com/miata/fm2r/timing-belt-check1.jpg

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.

--Ian

Huh, I guess you can even kind of see that the key isn't lined up with a 'valley' in product pictures...

https://cimg9.ibsrv.net/gimg/www.mia...3bb2915025.jpg

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.

I was also unable to get what I would call "perfect alignment". if they fix it I kind of want a new one now.

No pistons in this motor, so I can't verify TDC, woodruff looks to be vertical by eye...

can quality control be this loose?

https://cimg2.ibsrv.net/gimg/www.mia...2915c932a8.jpg

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.

https://cimg0.ibsrv.net/gimg/www.mia...19ba28a147.jpg

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.

But will effect spark timing on NA's which rely on the CAS.

My ATI is BNIB on the shelf. Time to open the box and eyeball it.

Good thing I have adjustable cam gears waiting on the same shelf.

FML. Taking 10 from work to go snap a picture.

Edit: My sway bar is blocking my crank bolt access.. so I cant turn the motor to check. I'll have to check after working hours..

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?

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.

What about repairing it? That rear plate is removable and installs with a small swage pin. I could drill the hole for the pin in removable plate.

BUT - I'm at work and not looking directly at it, is the woodruff key - to the - gear teeth a permanent thing?