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Old 03-18-2018, 02:42 PM   #1
TURBOTOD
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OMGHi2U Let's Talk Adjustable Cam Gears!!

Pre-curser statement: Yes, I have used the search button. Yes I have done quite a bit of reading. Yes, I have researched other high power builds.

There are SEVERAL High Horsepower builds that have been pushing in excess of 25psi (sometimes daily). My question is this: What Camshaft Gears are people utilizing on their builds? Is everyone utilizing the OEM Plastic Gears?

I of course realize that builds vary greatly from displacement, sleeves, port work on heads, fuel use, build clearances, turbo selection, compression ratio, camshaft selection, etc, etc. What I HAVEN'T seen covered, nearly at all, is the use of aftermarket adjustable camshaft gears. It seems to be something that is simply not covered and I'm really curious as to why. Offerings for the EJ207 through EJ257 seem to be available from Richard Clark Motorsports, Brian Crower Racing, JUN Auto, Tomioka Racing and little known others.

So what is everyone out there using, and why? That's what I'd like to know, and I'm sure I can't be the only one either! Let's hear what you've got, and why you decided to include them on your build. Anyone that is over 500whp, your inputs are welcomed, please and thank you.

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Old 03-18-2018, 08:09 PM   #2
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generally people prefer to keep avcs

adjustable sprockets usually come in place when you are tuning for a certain powerband, as it fixes the cam timing offset

another reason I see using adjustable exhaust sprockets on single avcs application (along with eccentric timing belt pulleys), is if you are incredibly anal and intend to degree your cams
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Old 03-18-2018, 08:40 PM   #3
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For most, they just run what they get and don't care. Most engine builds these days are just worried about lowest price.

As pointed out above, AVCS guys have limited gains and cams are usually only optimized on those with a particular powerband target. S-AVCS guys can get just exhaust gears from Brian Crower and use eccentric pulleys to keep the intake cams 'square'.

D-AVCS guys just use eccentric pulleys and let the ECU adjust timing.
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Old 03-18-2018, 09:56 PM   #4
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^ Thank you for the feedback, I appreciate it! I don't doubt for a second that as of lately the final price of the build is a major point of contention (and I understand that whole heartedly). In my case (S-AVCS), I am wondering exactly that point.... At the power level I intend to be aiming for (6466 @ 40psi on Ignite 114 and 35 PSI on E85), the conversation about Adjustable Cam Gears is a significant one. Especially when I take into account how much money I now have invested into my engine setup. For a street car, it's a quite a lot of money.

Eventually, I'd like to make a switch down the road to a dry sump setup, change out my suspension, and take it to the track to see what she can really do. I feel like asking these questions NOW, before my build is complete and in the car is valid. I realize racing teams and circuit racers with large funding aren't so concerned about these items, but for the guy that wasn't to build it correctly and not worry, it most certainly is.

So you mean to tell me that each of these guys we see with 600whp, 700whp and 800whp and above (S-AFCS) are utilizing the OEM Plastic units?!? I feel like if I can afford a $2.5K EMS (Elite 2500), I can afford to run a set of Cam Shaft Gears that aren't going to fall apart on me when it's less than convenient. Like... Ever.

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Old 03-19-2018, 01:42 AM   #5
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I'd imagine the MooreSport (MSI) gears are pretty solid, but I have not personally used them.
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Old 03-19-2018, 06:45 AM   #6
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I personally run a single avcs head and kelford 272/268's and run the factory exhaust gears. My motor is taking a healthy 28-29 psi on 93 from a pte 6062 and 36+ on e60.
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Old 03-19-2018, 10:29 AM   #7
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No matter what you spend for your build, if adjustable cam gears only net you a 2% gain the return on investment once you factor in install and dyno tuning may not be worth it for those not seeking ultimate power from they're setups.
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Old 03-19-2018, 10:37 AM   #8
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Not that I know a whole lot about them, but just thinking if the plastic units are good for insane amounts of hp without many/any reported failures, then the "plastic" units are probably good enough. Any draw backs to using the oem units would be all in your head, if that's the case.
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Old 03-19-2018, 01:17 PM   #9
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Quote:
Originally Posted by kellygnsd View Post
No matter what you spend for your build, if adjustable cam gears only net you a 2% gain the return on investment once you factor in install and dyno tuning may not be worth it for those not seeking ultimate power from they're setups.
I'd say 2% is a lot for a single part!

I'd consider them a necessity if you have aftermarket camshafts for the ability to accurately degree your cams on an AVCS motor... not that anyone bothers with that (important) step anymore.
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Old 03-19-2018, 02:33 PM   #10
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My STi had BC adjustable cam gears on gsc s2's with DAVCS deleted when i bought it.

When I was building my replacement motor, I specifically went back to DAVCS as it netted better driveability on the street (my tuner said I would see better low end/low rpm driving with adjustable cam gears, which would result in higher torque on that part of the map.) My current setup is 29psi on e85 and making 600whp.

If I were building a drag specific setup, I would use adjustable cam gears. As your "working" rpm range is going to be very specific, and having correctly degree'd cams at those rpm ranges (i believe, but have no data to back up) would have a greater benefit then AVCS cam gears over the entire power spectrum.
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Old 03-19-2018, 03:13 PM   #11
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I had a plastic exhaust gear fail, so I use adjustable exhaust gears since they are more resilient and less likely to shatter or fail. We tried playing with the timing on the dyno and got a few more hp out of it, but nothing major. I'm likely going to dual avcs now though so no reason not to take advantage of it.
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Old 03-19-2018, 04:51 PM   #12
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Quote:
Originally Posted by mrsaturn7085 View Post
I'd imagine the MooreSport (MSI) gears are pretty solid, but I have not personally used them.
Didn't know they made a set.... **Checks Website**.... Holy SH_T! In stereotypical MSI fashion no less... For a danty $1,995.

Quote:
Originally Posted by danbolsom View Post
I personally run a single avcs head and kelford 272/268's and run the factory exhaust gears. My motor is taking a healthy 28-29 psi on 93 from a pte 6062 and 36+ on e60.
^ Awesome. Thank you for letting me know!! How has it been acting? Any issues? Drivability is good? No hiccups? What whp/wtq is it putting down?

Quote:
Originally Posted by kellygnsd View Post
No matter what you spend for your build, if adjustable cam gears only net you a 2% gain the return on investment once you factor in install and dyno tuning may not be worth it for those not seeking ultimate power from they're setups.
^ The ROI "power wise" I'm sure is not that big in comparison to other parts. I'm much more concerned with reliability (within reason) and not failing at that power level.

Quote:
Originally Posted by viper_crazy View Post
Not that I know a whole lot about them, but just thinking if the plastic units are good for insane amounts of hp without many/any reported failures, then the "plastic" units are probably good enough. Any draw backs to using the oem units would be all in your head, if that's the case.
^ True. And if that's what it ends up being, I'll gladly admit it!!

Quote:
Originally Posted by mrsaturn7085 View Post
I'd say 2% is a lot for a single part!

I'd consider them a necessity if you have aftermarket camshafts for the ability to accurately degree your cams on an AVCS motor... not that anyone bothers with that (important) step anymore.
Which I will be while running the Kelford 199-C (272/268)...

Quote:
Originally Posted by fatalman View Post
My STi had BC adjustable cam gears on gsc s2's with DAVCS deleted when i bought it.

When I was building my replacement motor, I specifically went back to DAVCS as it netted better driveability on the street (my tuner said I would see better low end/low rpm driving with adjustable cam gears, which would result in higher torque on that part of the map.) My current setup is 29psi on e85 and making 600whp.

If I were building a drag specific setup, I would use adjustable cam gears. As your "working" rpm range is going to be very specific, and having correctly degree'd cams at those rpm ranges (i believe, but have no data to back up) would have a greater benefit then AVCS cam gears over the entire power spectrum.
^ Better torque with a broad powerband that is useable sounds like something that would be AWESOME to have on the street. Trying to have the best of both worlds.

Quote:
Originally Posted by subydude View Post
I had a plastic exhaust gear fail, so I use adjustable exhaust gears since they are more resilient and less likely to shatter or fail. We tried playing with the timing on the dyno and got a few more hp out of it, but nothing major. I'm likely going to dual avcs now though so no reason not to take advantage of it.
^ Aaaaaaaaaaaaaaand THAT's what I would be so very scared of happening. I could only imagine the amount of internal carnage from having a failed Cam Gear. Please God No!!!

Thank you so much for the feedback guys... I appreciate it. Keep it coming!!

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Old 03-19-2018, 05:31 PM   #13
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Quote:
Originally Posted by kellygnsd View Post
No matter what you spend for your build, if adjustable cam gears only net you a 2% gain the return on investment once you factor in install and dyno tuning may not be worth it for those not seeking ultimate power from they're setups.
Could be the difference between a win and a loss. Seriously, if money is no object, then squeezing every ounce of power out of a build can have a drastic outcome. And when you net that win, or take a loss for that matter, you'll be looking back on that moment you decided for or against getting that one part.
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Old 03-19-2018, 11:20 PM   #14
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Here’s the main cost I don’t think your factoring in...the tuning and constant adjusting. I can see the price varying a lot from shops by how much time they spend but i’d guess an additional 500-2k on top of your normal tune cost

Look around and you’ll see most people making a lot of power 600-1000hp+ are using stock gears or after markets ran at zero. If this was a time attack car or strictly drag chasing every tenth then it would make more sense since you can shape the power band to your liking. IMO money can be spent elsewhere and see better ROI but it’s your money does as you please
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Old 03-20-2018, 01:19 AM   #15
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There is also a significant wieght saving when removing AVCS gears for either non-AVCS or aftermarket adjustable units. The wieght differences are somewhere around 1/3 to 1/4 of the wieght. (Closer to 1/4 if you consider the wieght of engine oil inside the AVCS units during operation.)

The less wieght probably wont make much difference to power directly. But it does take load off the timing belt system. Which i can only see as a good thing if you want to rev the engines out. Most engines that have more than 2 cams use timing chains. Pretty much the only engines that use belts are inline OHC engines. The Subaru is basically a quad cam engine. And timing belt related failures arent un-common in the subaru world. There have been quite a number of the tensioners pull out of the mounting block and other such horror stories. Not saying this is a result of heavy cam pulleys, as i dont have any way to directly prove it. But it is interesting to wonder if its related


Brian Crower Vernier Cam Sprocket VS OEM AVCS Cam Sprocket. Right Intake. Subaru EJ25 by bram biesiekierski, on Flickr

Brian Crower Vernier Cam Sprocket VS OEM AVCS Cam Sprocket. Left Intake. Subaru EJ25. by bram biesiekierski, on Flickr

Brian Crower Vernier Cam Sprocket VS OEM AVCS Cam Sprocket. Right Exhaust. Suabru EJ25. by bram biesiekierski, on Flickr

Brian Crower Vernier Cam Sprocket VS OEM AVCS Cam Sprocket. Left Exhaust. Suabru EJ25. by bram biesiekierski, on Flickr

Last edited by Bram; 03-20-2018 at 01:25 AM.
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Old 03-20-2018, 01:31 AM   #16
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The tuning is accomplished via AVCS - the adjustable gears are really just for setting the correct zero point when you degree the cams after install. Given the small diameter of the cam itself, manufacturing tolerances are why using adjustable gears is needed to zero them out. On OEM cams for older motors, offset woodruff keys were another option... cams are just a little more complex now.

I would not use a cam gear that could slip - anything held by 5 pinch bolts without actually having detents would be a no-go for me.
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Old 03-20-2018, 02:22 AM   #17
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Quote:
Originally Posted by viper_crazy View Post
Could be the difference between a win and a loss. Seriously, if money is no object, then squeezing every ounce of power out of a build can have a drastic outcome. And when you net that win, or take a loss for that matter, you'll be looking back on that moment you decided for or against getting that one part.

That's my point though. Unless you are in a restricted class where you are restricted to a max compressor wheel size or max boost level and the you are reaching for the last bit of power from a specific setup then cam gears make sense if you're trying to get that last bit of power. For most who just want a bunch of power you have the option to go bigger on your turbo or crank up the boost if you can. Once you factor in tuning to get the most out of the gears its usually cheaper to get power by other means.
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Old 03-20-2018, 09:25 AM   #18
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Quote:
Originally Posted by Homemade WRX View Post
For most, they just run what they get and don't care. Most engine builds these days are just worried about lowest price.

As pointed out above, AVCS guys have limited gains and cams are usually only optimized on those with a particular powerband target. S-AVCS guys can get just exhaust gears from Brian Crower and use eccentric pulleys to keep the intake cams 'square'.

D-AVCS guys just use eccentric pulleys and let the ECU adjust timing.
I would be careful using the eccentric cam belt idler pulleys.

Many years ago, Subaru used to infact supply their timing belt kits with a blue bearing pulley and an orange bearing pulley. (Smooth pulleys.) It was common enough for the orange bearing to wear out and lean over causing timing failures. ( catastrophic failures ) So common infact that subaru stopped selling the orange bearings back around 2011 or so if my memory serves me well.

Now the reason was the orange bearings were a single race and not near as tough as the blue double race bearings.

Now guess what. These eccentric cam pulleys you see from some outlets look like they are using the same style of single race bearing that subaru stopped using because of all the faileures. The bearing is recessed into the hole. If it was a meaty dual race bearing then it wouldnt be recessed, instead it would be sitting flat like the strong bearings do.
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Old 03-21-2018, 08:36 PM   #19
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Quote:
Originally Posted by mrsaturn7085 View Post
The tuning is accomplished via AVCS - the adjustable gears are really just for setting the correct zero point when you degree the cams after install. Given the small diameter of the cam itself, manufacturing tolerances are why using adjustable gears is needed to zero them out. On OEM cams for older motors, offset woodruff keys were another option... cams are just a little more complex now.

I would not use a cam gear that could slip - anything held by 5 pinch bolts without actually having detents would be a no-go for me.
Have you degree'd any aftermarket Suby cams? I'm interested in how close most are to the actual cam card specs. I've honestly never done it but am very interested in the results.
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Old 03-21-2018, 09:05 PM   #20
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I've checked a few sets of Cosworth (1) and Tomei (2) cams and they've all been close but a few degrees of adjustment would have had them spot-on. Neither had adjustable gears - I just had the tools to check them so I did while the motors were out.

The problem is just the inner diameter of the cam is so small that the locating pin only needs to be a hair off to not be zeroed. Also, we don't exactly have the shortest timing pulley in the world on our motors... there's a lot of room for error between the crank and the actual lift of the cam.

A cam might be spot-on when read using V-blocks and a dial indicator but when you factor in the entire system, things get sloppy.
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Old 03-22-2018, 09:10 AM   #21
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Quote:
Originally Posted by mrsaturn7085 View Post
I'd say 2% is a lot for a single part!

I'd consider them a necessity if you have aftermarket camshafts for the ability to accurately degree your cams on an AVCS motor... not that anyone bothers with that (important) step anymore.
I wouldn't say 2% is a big if you consider the area under the curve.

Also, I've found Kelfords to be a bit off. It's pretty much impossible to be spot on, OEM cams too.



To place a dowel pin with it's own slip fit tolerance with such a price location on a small diameter circle (the end of the cam)...yes, even for CNC's. Anyone that uses CNC knows that they all have their limitations.

So adjustment is needed due to simple manufacturing and assembly limitations.
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Old 03-22-2018, 04:16 PM   #22
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Quote:
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...OEM cams too.
This cannot be overstated - OEM cams, regardless of manufacturer, will be off just as bad if not worse than aftermarket.
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