Since its introduction on the world arms market in the late 20th century, FN Herstal's P90 has had a number of enhancements made to it, which set it apart from all other small arms. This compact but full-powered weapon was designed primarily for military personnel including communications specialists, drivers, medical workers and others who function in closed quarters that do not lend themselves to even abbreviated rifles.

In the world of AEG, we have P90 replicas primarily from TM. The TM P90s are V6 mechbox based and are having highly similar architectures.

This title focuses on the TM implementation of P90. Based on the contents of our highly successful Practical AEG Upgrade title, this e-book goes one step further by covering P90 specific performance and maintenance issues. 

P90 Upgrade & Maintenance is organized based on the primary objectives of pre-upgrade considerations, high FPS upgrade, high ROF upgrade and high accuracy upgrade. In addition, a section on troubleshooting is included.

We tell you what to do and what to avoid so you can achieve the best possible performance without spending all your savings. Rather than going the cumbersome step-by-step way, we teach you the essentials through an easy-to-read Q&A format backed up with annotated photographs and diagrams whenever necessary.

With over 120 pages of text and illustrations, this e-book is a MUST READ if you want to master the art of P90 AEG upgrade and optimization!

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DISASSEMBLING THE P90

ADDRESSING SEVERAL P90 SPECIFIC PROBLEMS
 

HIGH FPS UPGRADE
What is proper usage?
What are the key elements of a high FPS setup?
FPS increase in meter readings VS performance increase in a practical sense: the law of diminishing marginal gain in performance.
0.20g BBs versus 0.25g BBs versus 0.30g BBs: the heavier the better?
Does FPS always go hand in hand with Joule?
What is the difference between the FPS system and the Joule system?
How do you use FPS to measure Joule?
How do you use FPS to give an estimate of the range?
Higher FPS = lower ROF?
Softer spring = Higher ROF?
Harder spring = Lower ROF?
Is 8.4V insufficient for an upgraded mechbox?
Does battery size matter?
Is battery power important for semi-auto firing?
EG-1000 and other alternatives
Why (and why not) should I buy the high torque gear set?
Why (and why not) should I use helical gears?
Why (and why not) should I keep the stock plastic bushings?
Why (and why not) should I replace the stock plastic bushings with metal bushings?
What is an easy way to (more accurately) shim?
How do I tell if shimming has been done correctly?
What is the recommended order of gear insertion?
Longer spring versus shorter spring: the longer the better?
What are the major parameters of a spring?
Is a harder spring more harmful for the internals?
Installing a long spring: tricks and potential danger.
Installing a short spring: tricks and potential danger.
Why (and why not) should the spring be ground?
How to facilitate spring spinning?
What is a variable pitch spring? Is it always better for AEG?
Use of spacers for spring compression: tricks and potential danger.
What is wrong with a custom made spring?
Systema Springs versus PDI Springs
Can stainless steel spring offer better FPS?
Can Telfon Coated spring offer better FPS?
What can I do to reduce stress on the gears?
Can an EG1000 increase FPS (through higher torgue) over an EG700?
Why (and why not) should I use a Bore-Up Cylinder?
Why should I replace the stock cylinder on my P90?
Different guns use different cylinders that have different number and position of openings. Why’s that?
Is it useful to block the cylinder opening altogether?
Why is it useful to put holes on the piston head? Any alternative?
Why (and why not) should I use a metallic piston head?
How about a silent head set?
Is aluminum piston more durable?
Is the stock mechbox too fragile for M130 or above?
How do I effectively reduce heat on the motor?
Why (and why not) is the one o’clock gear timing an issue?
Can I still use the smaller batteries to power my upgraded mechbox?
I want to hide my battery inside the grip and the stock but the battery cells are too big. What should I do?
Chaining up your batteries: Parallel VS Serial configurations.
Should I use Sanyo battery cells for maximum performance?
How safe is it to remove the fuse? Any alternative?
Why (and why not) is it necessary to replace the stock wires?
Why is it necessary to shorten the wires?
Why (and why not) is it necessary to replace the stock Tamiya connector?
Are NiCd batteries superior to NiMH batteries for driving upgraded AEG?
How do I optimize the overall performance of the stock motor?
Is it possible to increase the torque of the stock motor? If so, how?
What else should I buy for a high FPS configuration?
What is wrong with the soda can test?
What is right with the soda can test?
What is the most accurate way to measure FPS?
 

HIGH ROF UPGRADE
What are the key elements of a high ROF setup?
Can I increase the ROF while keeping the FPS at the stock level by using 9.6V battery?
Voltage VS mah – which one matters the most?
Can I increase the ROF by replacing the mechanical contact switch with a solid state switching mechanism based on MOSFET?
Can I increase the ROF by using capacitors at the power source?
Is high ROF a major cause of tappet plate breakage?
ROF-wise, why (and why not) should I replace the stock plastic bushings with ball bearings?
ROF-wise, why (and why not) should I replace the stock plastic bushings with metal bushings?
How about oil channel bushings?
Why (and why not) should I buy the high speed gear set?
Should I upgrade to a Teflon Cylinder?
How about a high speed cylinder set?
What makes a ball bearing spring guide meaningless for a stock TM gun? How to work around?
Is there any cheaper alternative to ball bearing spring guide?
Why a ball bearing spring guide alone may not increase the ROF?
Can I use a Version 2 spring guide in a Version 6 mechbox?
Should I upgrade to a Systema high speed motor for higher ROF?
How do I optimize the stock motor’s RPM without spending major $?
How can I increase the ROF while keeping the FPS at near-the-stock-level?
What is the right type of spring and battery to use for this purpose?
Is ROF over 30/sec possible?
What is the major ROF bottleneck?
Is aluminum piston better off for a high ROF configuration?
Are lighter gears better off for a high ROF configuration?
What else should I buy for a high ROF configuration?

HIGH ACCURACY UPGRADE
What are the key elements of a high accuracy setup?
How to improve accuracy with short barrel?
Can a long barrel deliver higher accuracy and range?
Why (and why not) should I replace the stock cylinder when using a longer inner barrel?
What is good about a high precision barrel?
How to maximize the effectiveness of a high precision barrel?
What is the drawback of using a high precision barrel?
How do I hide the longer inner barrel?

TROUBLESHOOTING
My stock P90 is dead after approximately 3000 shots. Why?
What will happen with improper shimming?
And what should I do to remedy the problem?
How do I prolong the life of the mechbox?
When the mechbox is running, the nozzle does not move at all. What is wrong?
My mechbox got stalled after replacing the tappet plate. What’s wrong?
What cause the piston gear to break prematurely?
My stock motor was overheated. What should I do?
What should I do for proper motor maintenance?
What causes gear stripping?
What can cause the hopup rubber to break?
How to prolong the life of my battery?
Is slow charging always good for my battery?
How to safely charge a battery?
Is NiMH battery free from the memory effect problem?
Should I fully discharge the battery every time after use?
How do I fix the battery memory effect problem?
My gun keeps mis-firing. How do I tell if this is a magazine problem or a mechbox problem?
I suspect that the hi-cap magazine is not working. What should I do to fix it?
What causes double feeding?
What needs to be regularly replaced to keep my gun in good shape?
 

Technical Appendix Guide also included FREE OF CHARGE.  Updated on July 11, 2006. Contents: Safety precaution Cutting wires Tools you don’t absolutely need Handling of screws Better trigger squeeze for accuracy improvement Ball bearings: how they work and why they break Soldering techniques More on battery configurations Parallel configuration Battery chargers Steps needed for successful motor break in Motor bushing break in How does heat hurt the motor? Adding torque to the motor Barrel length / FPS correlation and performance compensation The mechbox runs noisily on a new setup The switch plate has been burnt... Cleaning of electrical contacts Choosing wire: Stranded wire VS solid wire AEG water resistance Troubleshooting mechbox electronics Troubleshooting a weak Hi-Cap mag Making your AEG quieter Do-It-Yourself Electric Motor Driven Hi-Cap Mag Achieving ultra high ROF Achieving ultra high ROF through piston teeth removal The sector gear delay loading chip Misfeed when using heavier BBs Why is One Way Piston Head preferable?

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