camshaft deviation analysis
 

I hooked up my Durametric today to look at camshaft deviation specs. Do these look good? Is there anything else I should check?
2000 Boxster S, 167,000 miles, original IMS:
Bank 1: -5.63
Bank 2: -6.5
remained unchanged regardless of RPM

1999 Carrera 4, 77,000 miles, just replaced IMS w/LNE:
Bank 1: -6.56
Bank 2: - 4.39
remained unchanged regardless of RPM

I was looking to get air-fuel ratios, but couldn't find that function in Durametric... am I missing something?

Cam deviations are ok & @ max deviation. If you have not replaced the VarioCam chain wear pads you should do it soon!

If I remember correctly, click on the Engine folder to expand the options, then click on the Actual Values tab and then select the data you're interested in. It will provide a graph.

The Durametric does not list a read out for air fuel rations per se, but uses Porsche's technique of measuring fuel trims under the "actual values":

http://i19.photobucket.com/albums/b1...tricapril9.jpg

In Porsche terminology, you want to look at "adaption values, and it works this way:

System description
The adaptation values can be read out with the PIWIS or Durametric system.
The key to the adaptation values is as follows:

RKAT = Adaptation in range close to idle
Cylinders 1 - 3

RKAT2 = Adaptation in range close to idle
Cylinders 4 - 6

FRAU = Adaptation in lower load range
Cylinders 1 - 3

FRAU2 = Adaptation in lower load range
Cylinders 4 - 6

FRAO = Adaptation in upper load range
Cylinders 1 - 3

FRAO2 = Adaptation in upper load range
Cylinders 4 - 6

FR = Oxygen sensor for cylinders 1 - 3
FR2 = Oxygen sensor for cylinders 4 - 6

My understanding of range 1 and range 2 is that range 1 is the reading before the DME adapts the mixture and range 2 is after adaption.

Sounds to me like both engines need need wear pads on the cam adjusters. We see these worn at as little as 35K. These had 30K on them with a female driver, which is the catalyst for this wear in so many cases.
These were resulting in cam deviations of 9 degrees. Of the last 20 IMSR procedures we have done on 5 chain engines, 75% of the engines did not pass my pre-qualification due to excessive cam deviations that were created by these components being worn. We will not carry out an IMSR if cam deviations are in excess of 3 degrees, because the car will set a CEL after our work is done and then we have to explain that the issue was not a result of our work.
The 3 chain engine omitted these completely.

http://986forum.com/forums/uploads01...1395266819.jpg

Jake, do you replace them with the superseded OEM part, or do you have a better replacement part?

Jake,

When you say female drivers are the "catalyst" for wear, to what are you referring exactly? What is it that females do wrong? So I can be sure I'm not doing the same thing :cheers:

Funny, I just opened mine up to find the culprit of my -9 on one bank and was puzzled to see the first pad looking just fine. The I turned the tensioner over to see the 2nd pad and whoa! Looked just like that sucker in the picture!

This is what happens when people drive a Porsche like a Honda, or Toyota or Buick Skylark.. Easy driving keeps the VVT arrangement in the "loaded" position at all times and increases the forces these wear pads see.

Men can also drive like females, and they wear these components out way early as well. We have actually seen these wear so thin that they break in half.

Thanks for all the info. Time to start looking for tensioner pads...

Oh yeah, just hit 800 posts in 9 years of membership and P-car ownership. Woo-hoo!!:cheers:

Ha ha! That explains a lot! When I bought this car in the spring, the p o almost had a fit when I punched it on the test drive!

Mine is at the -6 limit as well.

How big a DIY job is it to replace the tensioner pads?

Can it be done with the engine in place or do you need to drop the engine?

I think mine are both at around -5.something, rock steady. 2000S, 110K miles. I will bust out the durametric this weekend and get a screen capture, and now that I know how to check my fuel trim I will do that as well, thanks JFP.

It's certainly easier when you have room to move around, but dropping the engine is quite a job in itself for a first timer ( like me). Mine's a tip so I dropped the engine with the transmission. You need a bit of space to do this.. ( I didn't). You can do the tensioner rails in the car if you are flexible and patient. Wayne Dempsey's book is good for the tensioner procedure.
Now if I can only get the motor back in the car...

Has anyone replace these tensioner pads w/ the engine in there?

My bank 1 values vary greatly from hot to cold. Dead cold, its at about - 6.5, fully hot engine (after running for more than an hour) it comes down to under 5.5. I'm not digging into the motor until it gets substantially worse, and it been about the same in the 25k miles I've had my car.

Just wondering what kind of camshaft deviation you should see over time?

I have logged the following numbers at full operating temp. over the last month with very little millage put on the car.


Bank 1 deviation Bank 2 deviation

March 5th -2.0 3.0
March 18th -2.0 2.0
March 21st 0.0 2.0

I guess the question is does anyone know if this is normal? Thanks !

Those numbers all fall within normal range. Why the variation? Maybe someone else can chime in.

Those values aren't horrible and I'd say these are normal for a 5 chain engine of 55K miles.

Once cam deviations reach 3.5* I will not touch an engine for any reason in regard to mechanical updates, like the IMSB and etc. This is mainly because once our hands touch something we assume responsibility for a lot more than we should have to, and if the CEL illuminates for ANY REASON with a fault for anything to do with camshafts or positioning then the finger flies this way. That doesn't happen, because we don't give it the opportunity.

We either don't do the work and disqualify the engine, or the work to restore the camshaft deviations is carried out along with the preventive work.

Cam deviations impact MPG after they reach only 2* or so and we start seeing added fuel trim after 4* as the ECU tries to mask the issue.

Your values can change based upon engine temperature, oil temperature and environmental conditions. When carrying out any sort of comparative analysis its imperative that the variables be reduced to a minimum and that the tests be done at the same temperatures and etc. If they are not the results will be all over the place.