P9201 tool theory of operation

[Steiner944]

Hey gang,

I just got my new P9201 in the mail today. Props to Sunset Imports for not marking up the price on this tool to ridiculous levels.

I was a little surprised at the way it appears that this tool determines the tension of the belt. I was prepared for the range on the dial face and have read all the tech posts. It is hard for me to conceptualize the operation of the tool without being able to actually install it. I left my old belts on just to get a reference point prior to doing the swap.

My question is aimed at the tech gurus. AFJuvat, SoCal driver, Razorback1980, Shikzachaser, and others, just to name a few.

Does this tool measure the tension that is placed on the belt by adjusting the idlers? Or does it test the tension of the belt in relation to its age and elasticity? If it measures the former and not the latter, I don't see how, unless I'm not using it correctly.

Basically, I'm nervous as hell about chucking a belt and trashing my valve train or worse. I want to make darn sure that after I spent the bucks for the tool that I use it properly. Thanks in advance.

[yellowline]

I'm no expert, but I do have and use a 9201 on my car.

It measures the deflection between the two idle rollers and flat plate on the back of the tool. It's like pushing in on the belt with your thumb-the tighter you make it, the less it deflects. On the tool, you see this through a higher reading.

Because the tool only calculates upwards and doesn't reset itself, you can only give yourself an inaccurately high reading. You can't get a low reading. If you end up taking two different readings of 2.4 and 2.7, assume it's 2.4 and act accordingly.

I don't recommend this, but you can leave the tool attached to the belt and adjust the tension, just to see how it works. I wouldn't consider that your reading, though.

My 0.02, value it accordingly.

[Steiner944]

Thanks, that makes sense. Also helps to see the proper terminology. Now to hope the rain stays away tomorrow, maybe I can have some fun. I got a 2.4 on the balance and a 5.0 on the cambelt. My krikit was reading 50 pounds each time, but I thought I might be using it wrong. I was too worried that if I adjusted the tension using the krikit, that it would be too loose and skip teeth...........you know the rest of the story.


Frank

[Eldorado]

5.0 on the timing belt is rather high, isn't it?

[Steiner944]

Yeah, according to the manual, 4.0 on a newb and 2.7 on a used. Since I know that my belt has been there for a while, this was a snap, crackle, pop waiting to happen, in my opinion. I've read that guys say you can run the 15,000 miles no matter how tight they are, but I sure don't wanna go there.

[mscromer]

Hey Steiner944, how much did you pay for the tool, if you dont mind me asking.

[Eldorado]

funny you mention that..
I called my mechanic today to ask him to take an hour and test the tension on my timing belt, and correct if necessary and he said not to worry about it.. i installed new belts in august, and it's just rounded it's 2k mark after sitting all winter... they need to be done..

I'll be taking it elsewhere..

[yellowline]

Originally posted by Steiner944
Yeah, according to the manual, 4.0 on a newb and 2.7 on a used.

Aim for 4.0, 5 is too high.

I've read that guys say you can run the 15,000 miles no matter how tight they are, but I sure don't wanna go there.

The belt that is on my car was audibly slapping the covers after 1300 miles and had a tension reading of about 0.7. I would retension after breaking the belt in. After that, it's good for 15k.

They can be driven to 30k without issue. I have no record of a belt replacement between 25k and 93k on my car, but don't try that. A belt a year is a little wasteful, unless you put 30k a year on it.

[Steiner944]

This is real interesting about the price. Last Tueday, I got the quote for 439 plus 11 for S&H from Jeff at Sunset imports. There was one for 200 on eBay with 5 days left. I thought, well, what the heck, at least this way, I know I'm getting the tool. Since the IRS just gave me back my money that they made interest income from during 2005, I splurged.

Know what, that thing went for $480 on eBay. One of the few times I had good foresight. Not trying to circumvent Pelican on the tool, heaven knows I'm thankful for this board and the great folks on it.

Hope this helps. Ain't cheap, but it is piece of mind. My car is going to get a belt every spring. I don't want a failure. Now that I have the tool, replacement and checks are not a problem.

Frank

[Steiner944]

Oh.........those aren't the belts that I put on, those are the belts that came with the car when I bought it three months ago. They were making noise on the insider of the cover. I took it to a dealer, they quoted me $3300 for the belt job, so I parked it.

Have been buying parts and tools ever since to do the job myself.
I'm a fine mechanic, just always worked on american iron with forgiving tolerances. "PORSCHE" has me scared. Epecially when my machine shop just looked at me and said, "What do you mean do we know anything about Porsches, an engine is an engine." Just a little nervous. In the Army we sometimes say discretion is the better part of valor.

Frank

[Steiner944]

"A belt a year is a little wasteful, unless you put 30k a year on it"

I'm not so sure about that. I have read a multitude of horror stories about newer belts snapping, how old is the new belt, belt shelf life, etc.

Kinda like Spring maintenance on the motorcyle, in my mind. Probably could get let it go longer, but for the low price of a belt, versus the high cost of belt failure, why? This job doesn't seem anywhere as bad as I thought it was going to be. The Army kills us with preventive maintenance, so I may just be a product of my environment.

Frank

[Eldorado]

to me, the more belts you go through, the more you increase your odds of finding a bad belt..... it's just the law of probability..

I'm sticking to the regular intervals on mine.

[Steiner944]

Eldorado,

Good point. Probably a crap shoot no matter how you go. Until they put "born on dating" stamps in the belts, we're just rolling the dice.

[ae1969]

That is one of the best investments any water pumper can make.

As has been mentioned the tool does not take into account age/wear and tear...........so it is a good idea to always mark the date and mileage of when it was last done.

What is interesting is that the markings on the dial really have no direct correlation to a measureable value.

[yellowline]

I do think the belt is fairly reliable, but the system is only as strong as its weakest link. Check the rollers and eccentric tensioners. Make sure the belt doesn't rub- that will make a belt prematurely fail. I regularly spool up the engine quickly through double clutching, etc., and the belt isn't an issue. Run a good name belt (Gates or Conti, though I've heard bad things about Conti, still what's on my car) and you'll be fine for 2 or 3 years. Army stuff sees far more severe service than your car, no doubt.

I should also note that the needle does return to 0 when you release tension-I wrote that wrong. You can read the telltale, though.

[SoCal Driver]

Timing belt is checked on the long run between the crank and cam pulleys. This is the tensioned run when the engine is running.

You have to turn the engine over clock wise (normal rotation) then back the crank pulley enough to tension the water pump side of the belt (usually the slack side or run). This will put all of the slack between the cam and crank pulleys.

On the early 944's that have not had the water pump update with the metal divider between the opposing belt runs, when properly tensioned you can just push the slackened timing belt into the opposing belt coming around the water pump pulley.

It's suprising how tight the belts become when the engine is hot. Just leave the top cover off and check the belts.

A replacement balance shaft belt had grooves along the tops of the teeth. This was to subdue the noise (whining) by venting the air out of the meshing teeth and pulley grooves.

[Porsche-O-Phile]

You do have the 9202 calibration bar as well, doncha? Careful recalibration of the 9201 between readings is your friend.

5.0 is very tight - you'll probably be stressing the water pump pulley with that much tension on it, as well as compromising belt life.

[AFJuvat]

9201\2 calibration bar, and 5.0 is not excessively tight., but still not recommended.

With the bar loaded, the tool should read 4.0. If it does not, you need to adjust the tool - you use a 1.5mm allen wrench through the hole on the bottom of the tool.

The tool measures the actual tension of the belt. The tool is actually a dial gauge. One complete rotation of the gauge = 1mm of deflection. From zero on the tool with the correct preload on the gauge; a new belt should read 4.0 scale units +\- 0.3 scale units. For the timing belt, the tool is installed upside down. If you install it right side up, you will get erroneous readings. If you have the updated waterpump with the guide bar, you need to remove the bar to measure the tension accurately.

Procedure:

Ensure that all pullies, rollers and idlers are free spinning without excessive bearing noise.

wiggle the waterpump pulley, there should be no significant movement.

Spin the motor to TDC #1. then rotate backwards 1.5 teeth on the camshaft pulley.

You will need to remove the guide bar and it may make it easier to remove the idler wheel above the timing belt.

Set the tool on the long run between the crankshaft and camshaft pulley, upside down. lock the sliding bar in the closed position. then rotate the drag needle counter clockwise so it is set to the indicator needle. Now, without twisting the belt, unlock the bar and remove the tool Read the results on the drag needle.

4.0 scale units +\- 0.3 scale units.

Replace the tool on the timing belt/ Then set the tension with the rensioner pulley. rotate COUNTER CLOCKWISE to set tension. Torque nut on tensioner pulley to 50 NM (33 ftlbs)

If you have the auto tensioner, you DO NOT need the tool for the timing belt. Unlock the tensioner and let it swing out until it stops. then tighten the lock nuts to 25 NM (17ftlbs)

After you have set the tension, rotate the engine one full revolution and repeat the process.

Quick hints:

In practice, the tension usually drops after you complete the rotation. if you set the initial tension to 4.3 - 4.5 and then rotate, you will find that the belt usually winds up around 3.8 - 4.2

Set a used belt to 3.5 and you will find it will not loosen up as much.

Replace all idlers and guide bars.

Balance shaft:

Set motor to TDC #1 DO NOT rotate backwards

Ensure that the notches on the balance shaft pulleys line up with the marks on the rear belt housing. Upper notch is at 12 o'clock it is at 7 o'clock on the lower pulley.

Set tension by rotation tensioner CLOCKWISE. Ensure that the balance shafts DO NOT rotate during tensioning.

3.0 scale units +\- 0.3

Set a used belt to 3.0 as well.

AFJ

[Steiner944]

Yellowline - thanks, appreciate the advice. I did buy 3 rollers and two tensioners. Preventive maintenance taking control.

So Cal Driver - thanks for your insight

Porsche-O-Phile - thanks, I was under the impression that the tool would only need to be calibrated periodically, not every use. Am I mistaken? Good thoughts on the water pump. The 5.0 reading is the existing belt that I am getting ready to pull and replace, so my current pump, although recently replaced, may have internal bearing stress. Guess I will put on a new one.

Here is the real kicker. I went out tonite and did a couple more readings. I got some crazy readings all over the dial, so I did ten more. Still all over the place, so I decided to perform 20 readings and then chart them and share the results. Please keep in mind that I am measuring the old belt, before I start on the real deal. I want to master useage of the tool before I do it for keeps. Also, I have located TDC, backed up 1.5 teeth on cam gear (roughly 10 degrees) and then installed Arnnworx flywheel lock to ensure no movement. Tool was placed at same location as in photo on Clark's garage website, oriented upside down as in photo. Tool was pulled and re-zeroed between every reading. Method of read was to grasp body of tool, rotate gently clockwise until pin locked in body. The dial would then slowly reduce pressure on gauge and I would get a resting spot on the gauge needle less than the drag needle. Does that sound right? Basically, I charted two readings every time.

Here is the analysis of the readings: 14 readings were 2.3 to 2.8 on the gauge needle, while the drag needle read from 2.8 to 4.1.
The other 6 readings were way higher, perhaps from over-rotating body of tool. 4.7 gauge to 6.5 drag.

Perhaps there is a flaw in my technique. Any advice on technique is respectfully requested and sincerely appreciated.

Regards,

Frank

M

[Porsche-O-Phile]

Don't know about you, but I find that the rotatable dial on the 9201 tends to get bumped out of whack easily. Not super-easy, but it does happen. As such, I throw the calibration bar on it between readings unless I'm certain that I haven't bumped it or anything. Doesn't hurt.

Also, do this:

Calibrate the 9201 tool. Put it on your belt, take a reading. Take the tool off the belt. Release the tension on the 9201. Re-install right away, same place on the belt you just had it. Bet the reading is a little bit different.

This is why I believe in careful calibration. I find I get consistent readings this way.