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Old 06-25-2011, 07:33 PM   #1
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Default Adjustable cam gears, Worth the trouble?

So I have been given a set of adjustable cam gears as payment for helping a guy set up his megasquirt. I never seem to hear much about them on this forum and searching reveals they just don't get discussed. Is there any power to be had using these with a turbo? I am on Megasquirt, but what is going to happen to the cas if I start dicking with the exhaust timing? I presume I will just have to correct it with the trigger angle?

These are cheap eBay gears, however they have 6 bolts per pulley, and I know a couple of N/A guys who have been running them with no problems. I am daily driven, but drive like an adult most of the time (wife is usually with me, she has NO IDEA how fast this car is). I keep telling myself I will do a couple of track days per year but have not yet, and I do make a nurburgring trip at least once a year (leaving this friday!). But for the most part calmly driven.

I don't have the undertray anymore, and would of course be cutting the end off of the cam cover. I am also tempted to leave the rest of the timing belt covers off. Anyone been down this road? I know 944 guys do it, but I have to admit it does make4 me a bit nervous. On the other hand there is just as much chance a stone will get caught in the fanbelts and I have never heard of that happening (and I have been a pro mechanic for 15 years).

So what I am really asking is, are these worth the trouble? Will it make any more power? anyone else have any experience playing with the cam timing under boost? These being non interference engines and me being a Mechanic, the worst case scenario is little more that a tow bill, but if there is nothing to be gained then I wont bother.
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Old 06-25-2011, 07:40 PM   #2
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Most on here don't bother and just run 1 psi more. I have run them for quite some time and was able to pick up some midrange torque by playing around with them. This took some time on a dyno though. The gears are only 3 bolts, but haven't slipped at all. You can see the markings on the bolts.
I cut the valvecover but I didn't bother with the beltcovers or the metal plate behind the gears. The lower ones are still on.

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Old 06-25-2011, 08:20 PM   #3
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The only dyno's of timing gears I've seen have been unimpressive. A little one way and you'll gain a little top end and lose a little midrange, a little the other way and you lose a little midrange and gain a little topend. I don't have any personal experience though, so maybe someone will have something more to contribute. As for the timing covers, I've been running with mine off and the timing cover cut for a few years with no ill affects.
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Old 06-25-2011, 09:05 PM   #4
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Adjustable timing gears are part of my big turbo strategy. My plan is to advance the exhaust gear to help spool my 800hp turbo.

For a street car with a stock block I wouldn't bother.
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Old 06-25-2011, 10:53 PM   #5
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They're useful if your power band isn't where you want it.
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Old 06-26-2011, 12:39 AM   #6
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...and it should be if you buy the right turbo.
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Old 06-26-2011, 10:44 AM   #7
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Quote:
Originally Posted by Faeflora View Post
...and it should be if you buy the right turbo.
and the right cams.

but also the adj cam gears can fine tune the last few percent in some cases.

or say you want 400 hp and can retard cam timing to get there. there isn't a real case of "right turbo" that compliments a miata's power curve at 400 hp is there.
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Old 06-26-2011, 01:52 PM   #8
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Well I'll probably use them as they do look pretty bad ***. I have never done the timing belt on this car, so it won't be a waste of time taking it all apart. I'll just set them to standard timing until I get the EBC working properly and go to the dyno.
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Old 06-26-2011, 02:51 PM   #9
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advance for low end
retard for upper end

If you want to F around with them for fun, set the intake to 3-5 degrees advanced.

then set it to max retard.

and enjoy the difference.
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Old 06-26-2011, 08:57 PM   #10
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If they are the cheapo 50 set off Ebay, you may have a little problem. Saw a set at CDF Racing when I popped in to have a couple of problems sorted with my Group Buy. On this particular pair, the inner section on the inlet wobbled. The back of it has a machined radius but the other part didn't, so it wouldn't sit flat. Take out all the bolts and check. If it wobbles, it can be machined to fit better.
Everything else has pretty much been said. Can't recommend taking off the covers on a DD with the amount of crap on our roads.
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Old 06-27-2011, 01:10 AM   #11
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Loctite the bolts.
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