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Old 10-02-2012, 06:25 PM   #1
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Another Camshaft devation question

A few questions for the experts about camshaft deviation- I have been through all the forums and found some great information, but none that pins down my specific problem/concern/question.

Car details: 1997 Boxster base- 21,000k miles- 5 speed.
I purchased the car about a month ago and love it! Like a good Boxster/Porsche owner I bought a Durametric, changed the oil and inspected the filter (dealer changed September 2011- with ~ 18500) No metal found on either side-(one tiny sludge looking thing) other than that clean. De-snorked and thatís it for now.

Plugged in the Durametric- No codes Ėand everything checked out great- Checked the camshaft deviation at idle after 5 minutes of warm up.
Cam 1- 0
Cam2- -9
This concerned me immediately, because I expected some major movement upon driving. I took the car out for about a 5 mile drive while attached. I kept the RPM and both cams open during the drive to ensure I was getting a good reading.
Nothing changed the entire time- no deviation from either side?

The car seems to run great- good acceleration although it feels like it could give me more (maybe I just want more)

My question:

Do you think I jumped a tooth? Or was it set like this from the factory or from some recent maintenance- Both things I have read in the forum from the Porsche guruís

Thanks in advance for your input.

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Old 10-02-2012, 06:51 PM   #2
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deviation should stay constant and only change when the cams roll over at 4k rpm, at which point it should jump significantly to say 25. did you reve over 4k rpm and still get no movement?
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Old 10-02-2012, 07:12 PM   #3
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if you think your cams are not rolling over, you can manually trigger them with the durametric. if you go to activations there is an activation button for each bank. you should be able to watch your actual values when you do this, so that you can see the deviation hop when the cams are activated by the durametric (there should also be an audible change in rpm).

if nothing is happening then perhaps your solenoids are shot. regardless, a deviation of 9 at idle is out of spec, where spec is defined as within 4 or within 6 depending on how dr. ing is feeling (initially it was 4, but was expanded to 6; uncertain if this is tied to engine type or just a change in standards).
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Old 10-03-2012, 05:07 PM   #4
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Thanks for the info- I tired a few things today

Thanks for the information...very much appreciated.

After a nice warm up this morning I hooked the car back up- I activated bank 1 and 2 cams- and got a nice pull down from each just at idle. The car did not die but dropped significantly and returned after I stopped.

I then pulled cam 1 and 2 up and got the same deviation as indicated (1 @ "0" and 2 @ "- 9") then I attempted to activate the cam banks while watching the deviation- each time I tried it locked the program up and I had to get completely out of the program and re-start to get any communication??

I took the car for a drive again while monitoring the deviation on both cams- Got it out on the highway and reached the + 4k RPM mark numerous times with no fluctuation whatsoever?

I am going to remove the software from my computer and reload and try again tomorrow? Any suggestions?

Oh...all is not lost- I spent the entire day in the car- 80 degree day......... what deviation? who cares!! Thanks again!
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Old 10-03-2012, 05:19 PM   #5
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yeah, the software can get glitchy. i've found durametric very responsive and if you contact them you can get the durametric software to log the glitch and email the info to them for troubleshooting.

when driving, can you feel a surge of power at around 4k rpm when the cams roll over?
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Old 10-04-2012, 03:13 PM   #6
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Removed and reloaded software

Thanks again for the input Radium- your expertise/advice is appreciated.

Yes, I can certainly feel some changes at/or around 4k rpms. Feels like a power band in a dirt bike.

I removed and re-installed the software- hooked things up this morning. (Deviation: Cam 1- "0" Cam 2- "-8") so I actually seen some movement. I again attempted to activate the cam banks with the only result being software lock-up.

Took the car for a little more aggressive drive after warm up and getting communication going on the software again- Nothing- Rock solid at the above numbers? I pushed 6k rpm through the gears numerous times and got nothing?

This is my plan- Call Durametric tomorrow see if they have any ideas- did not get a chance to today.
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Old 10-05-2012, 04:32 AM   #7
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The durametric has two actual values for the cams. One is deviation which should be rock steady throughout the RPM band. The other measures actual cam position and should vary constantly through the rpm range.
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Old 10-05-2012, 07:00 AM   #8
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are you certain about that, rensho? put your car on the durametric, then tell me if your deviation stays constant throughout the rpm range.
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Old 10-05-2012, 07:19 AM   #9
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Quote:
Originally Posted by The Radium King View Post
are you certain about that, rensho? put your car on the durametric, then tell me if your deviation stays constant throughout the rpm range.
I believe so, my Dur reads 4 cam angle values, 2 for deviation, one for each bank, and 2 for actual cam angle, one for each bank. Deviation stays rock steady when I rev the car, but I can't remember reving it above 5k, so maybe at higher rpms it does change. I'll check it.
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Old 10-05-2012, 10:23 AM   #10
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On a 7.2 car, the 'Actual angle for camshaft' should either be 0 or 25 depending on whether the solenoids are activated or not activated. The cam shaft variation on these early cars is either all or nothing. Only the later cars (7.8DME) had the ability to regulate the actual value of advance which can give values between 0 and 40 depending on condition.

As stated above, 9 degrees base timing means your cam timing is out of spec.

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Old 10-05-2012, 05:37 PM   #11
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Thank you for the input- I got a response from Durametric today regarding the software locking up when trying to view the deviation while rolling the cams.

This was their response:

"Thank you for contacting Durametric. We appreciate your input. We find- as you pointed out- that this option does not work as expected. The activations do not work properly when activated from within the Actual Values screen. Our engineers are aware of the issue and are actively working on the resolution. We hope to have this problem resolved in a near-future release."

Cam 2 is still out of spec. and apparently my software (version 6) is not a complete package "yet". May have to call and see where they are on the fix.

I plan on contacting BHR (Bob Hindson Racing) in KC to see when they can set the timing, install IMS upgrade, check/replace the clutch and RMS if needed- maybe a few other things that sound like good things to do while in there.

I will drive and enjoy until the weather gets bad.
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Old 10-06-2012, 01:22 PM   #12
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dunno if they need to (or if it is even possible to) retime the engine. what they can do is check/repair the usual suspects when it comes to excessive cam deviation. the first indicators are parts that porsche has improved over the evolution of the m96 engine. the first of these are the chain tensioners fpr which there is a new porsche part #. there are three of them at $100 each, they can be serviced without opening the engine, and a worn one can cause the chains to not have the requisite tension and rattle around.

the other parts improved by porsche are the variocam tensioner pads. they are plastic, and if failing will leave chunks or hard greeny-black plastic in your oil filter. these are the pads that control tension on the chains that tie the two cams together and vary the deviation. the new porsche part uses a harder plastic. you have to remove your cam covers to get to these, but the whole engine doesn't have to come apart. the process is detailed here:

Pelican Technical Article: Boxster Camshaft Upgrade / Chain Tensioner Replacement - 986 / 987

there are other chain tensioner paddles that can fail (and ln engineering offer an improved part for this) that require complete disassembly of the engine.

otherwise, the senors that send the deviation information to the computer can go out of spec, or not be in spec from the factory. of course, it is because of the info being provided by these sensors that you are concerned in the first place. aside from replacing them, what is suggested is to monitor your deviation over time and use. if it says steady at 9, it may be that it is a bad sensor. if it continues to worsen, this suggests that the info it is sending is good.

finally is the ims. if it is bad you have already lost the race. signs of a failing ims are deviation values all over the map (due to the death wobble of the failing bearing) and your symptoms do not indicate this. so replace it if you have the trans off to do the clutch, but otherwise i would look at the other culprits above first.
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Old 10-06-2012, 03:14 PM   #13
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9 deg is pretty far out of spec. If you want to adjust the timing, the procedure is pretty easy and doesn't require any special tools,just a torque wrench. See the following.

DIY: Setting Cam Timing on M96
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Old 10-06-2012, 03:50 PM   #14
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here is a great diagram of all the chains, pads, ramps, tensioners and cams:

http://forums.pelicanparts.com/boxster-cayman-forum/685614-question-boxster-camshaft-swap-chain-tensioner.html

so, you can see, the crank drives the ims, the ims drives each bank of cams, and there is a chain tying intake and exhaust cams together on each bank. this chain has the ability to change tension at higher rpm ('variocam') resulting in an overlap between intake and exhaust - more air can flow, less back presure, more power.

*from what i understand*, the deviation values are the deviation between intake and exhaust. this is why they stay steady until 4000 rpm, at which point they change to a new fixed value as the cams 'roll over' to the new cam profile.

as per the attached diagram, what can cause an increase in this deviation is wear of the actuator pads (both items which porsche has updated) or a bad sensor. ims may affect deviation in that a wobble at the ims might introduce a vibration into the variocam assembly and register via the deviation sensor. worn tensioner paddlers, paddle pads or tensioners may also have the same effect.

the timing process in the diy referenced in the previous post, as stated by the author, does not affect the timing between intake and exhaust, but rather the timing of each bank relative to the ims, crank, and the other bank. timing the engine as per the diy should not affect deviation values. performing the timing in the diy will address timing issues caused by worn tensioners, paddle pads, tensioner paddlers or stretched chains, but doesn't address the problem causing the timing issue in the first place.

Last edited by The Radium King; 10-07-2012 at 09:30 AM.
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