We created this tool as an alternative to the Porsche's P9201. The P9201 is a handheld tool and can be used to tension both the timing belts and the accessory belts on your 944 or 928. It's real advantage is that it is compact and can be used on a variety of applications.
Our tool, the 920X, is an engine mounted tool and can be used only to tension the cam & balance belt on your 944 or the cam belt of the 928. In a couple of ways, our tool is better. Aside from price, you can dynamically set your belt's tension; e.g. see the tension measurement as throughout the process. With the Porsche tool, you make a guess at the correct tension setting and then use the tool to measure and verify. You may still have to torque the offset rollers or tensioner and do a final check to be sure the tension is within the acceptable boundaries.
With the 920X, the set up is more involved. It starts out with a similar setup to that of the Porsche tool by positioning of the cam/crank. The 920X has to then be mounted to the engine and a reference reading taken (with a reference bar in place). The reference reading is used as a starting point and deflection measurements are made relevant to that reference value. With the reference bar then removed, the tension can be set and made final while looking at the gauge.
That's it. You'll be surprised at how sensitive the tool is and how precisely the belt must be set to be correctly tensioned.
The 920X is steadily being improved and refined. These links are to the most current versions of the instructions.
Version 5.02 of the instructions (for tools made after June 1, 11).
Version 4.03 of the instructions (tools made between January 1, 09 and May 30, 11).
Version 3.13 of the instructions.
See video clips to show how to the 920X works (version 4).
Tensioning a Cam belt Part 1, Part 2, Part 3, All clips combined.
Tensioning a balance belt Part 1, Part 2, Both clips combined.
Note on the video clips: These short clips will walk you through the steps of using the tool, they are based on version 4, our newer version 5 is slightly easier to use. Many more details, photos and information are provided in the printed instructions that come with the tool. The clips are really just to give you an idea of how the tool works. Some numerical values, used in the clips, have changed with updates to the tool.
Version 1.01 of the instructions.
What exactly comes with the 920X tool?
The 920X is sold in two configurations. The 920X-944 contains the basic body, rod assembly and gauge shared by both configurations. It also includes the mounting adapter and reference bars for use on the 944/944S/944S2/944 Turbo/924S. The 920X-928 is identical but includes the needed hardware and reference bar for the 928 (instead of that of the 944).
A tool body and rod assembly.
A machinist's gauge that attaches to the body.
A fixture that also can be used to attach the tool to the engine - for tensioning the 944 balance belt or a similar adapter for use with the 928.
R
Attaching hardware needed for using the tool on the belt(s).
Printed
Which Porsche models will this tool work on?
944 Series - All normally aspirated and turbo 944s, 944S, 944S2 & 924S's. Important note: the 920X-944 attaches to the cam belt separator bar. The early 944 models did not come with the separator bar (a.k.a. guide rail). After 1986, the separator bar was standard equipment but for earlier cars the bar was added by Porsche to updated water pumps. Any time a pump was changed, the new "updated" pump was to be installed. Most of the older water pumps have disappeared but occasionally one still surfaces. If you are not sure what you have on your engine, its best to check your engine before you buy the tool. Here is a link to help you know how to identify an updated versus non-updated water pump.
928 Series - We have only tested and verified this tool on the 16 valve 928 engines. We believe it will work on all 928 engines, but until we have opportunity to test the tool on the later cars, we are limiting the applicability.
How does the 920X compare with the P9201?
First the 920X only works for the cam and balance belt of the models listed above, Porsche's P9201 does all belts and for other cars too.
The 920X costs approximately $165, the P9201 costs over $600.
The 920X comes with a reference bars, the P9201 requires a calibration bar which costs an additional $45.
Overall ease-of-use is about the same. The P9201 is hand held and requires almost no set-up, the P920X must be mounted to the engine and a initial reference reading made.
Consistency of reading is about the same, both are very sensitive and a use specific setup for use.
How does the 920X work?
T he 920X has a small internal spring and an extending rod. When mounted, these parts deflect the belt and a deflection measurement can be made. That measurement represents tension. To get a precise measurement we need the gauge reading at two points. The first is the reference point, shown in this sketch (below). In order to get that point, we must first insert a reference bar. The thickness of the reference bar adds a small amount to the reading but that will be adjusted for. Next, we know the distance from the reference point to the ideal tension point, this distance was found through development tests for the tool. We also have a calibration value for each tool that is determined during fabrication; see the attached 2” x 5” calibration tag. Through some simple math, each of these values come together to find the ideal setting. With a known ideal tension value we then remove the reference bar and adjust the belt’s tension until we read the ideal setting.
Has the 920X changed since it was originally offered?
Yes, a number of improvements have been made:
Spring perches have been improved.
Bearings have been upgraded.
E-clips are now used in all locations making disassembly possible.
A socket head capscrew is now employed to capture the gauge in the body.
A single wooden sled is now used to contact the belt (eliminates need to swap roller and sleds).
Added precision - each tool now comes with a calibration tag that states the unique values to be used.
Increased measurement travel allows for higher deflection pressure and more accurate readings.
Instructions have been improved (several times) and are now available as a downloadable PDF. Please feel free to review these instructions and become familiar with the tool BEFORE YOU BUY.
Can I arrange to have my older version of the 920X updated to the new version 5 specifications?
Can I get the adapter and whatever hardware is needed to extend my 920X-944 for use on the Porsche 928?
When I "snap the gauge" several times in succession, I get slightly different readings each time, some are within the boundaries some are not, what am I doing wrong?
