1/8 Scale Nitro Rally/Touring Car:

Mugen MRX-4 - H0070 - Radio Controlled Model

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History and Info for the Mugen MRX-4:

Introduced by Mugen Seiki circa 2005, the 4WD MRX-4 Racing Car - H0070 - is belt driven, on an alloy plate chassis, coil spring over oil filled dampers, rear dogbones, with front universal joint drive-shafts, 2-speed transmission and a full set of ball bearings.

Mugen MRX-4

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To race the Mugen MRX-4, it needs to be tuned to perfection for better stability, precise steering and provide enough grip to keep you on the track when going around tight bends at high speed. Even the smallest adjustment can change the feel of a car and our simple to follow instructions will guide you to the best Set-up to get you to the front and keep you there.

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Radio Controlled Model Accessories:

★ Mugen MRX4 Chassis ★

Buying a Used Mugen MRX-4
Touring Car (and What to look for)

There are essentially three reasons you might want to buy a used Mugen MRX-4 Nitro Touring Car; you may be a collector, looking to restore and display it; restore and sell for a profit; or simply restore and race an iconic vintage model. Personally, I used to get a buzz out of restoring an old clapped-out model, installing modern day electrics and maybe a few hop-ups, then showing the gang at our local club, just how competitive those old models could still be.

Cheap, pre-loved bargain models, parts and spares are always coming up for sale, but once you have made your purchase, the one thing you will always need, is an instruction manual. If not supplied with your purchase, they can often be downloaded from the Mugen website, or purchased separately on eBay. With an instruction manual, any problems with your model Touring Car you may discover, can easily be fixed.

Make a General Visual Inspection

Dampers
When you receive your used Mugen Touring Car, make a general visual inspection of the chassis, front and rear wishbones, suspension shock towers etc, for any broken parts that may need to be replaced. Then, take a screwdriver and box spanner and check each self tapping screw and nut for security, taking care not to over tighten.

Next, for those Mugen models with oil filled shock absorbers, remove them from the chassis and dismantle the coil springs. The damper shafts should push in and pull out with a smooth action. If you feel a jolt as you change direction, this means the oil has leaked out and must be topped up. At the same time, change the O-Ring seals to prevent more leakage. Also check the damper shafts for damage. If they are scratched, change them as soon as possible.

Check the Body-Shell

If the body shell of your Mugen MRX-4 is broken, ripped or damaged in any way, this can be easily repaired with rubber solution glue. Also, for added protection and if available for your MRX-4 model, fit an under guard to stop dirt and gravel entering the chassis.

Drive Shafts and Turnbuckles

Titanium Turnbuckles
Examine the drive shafts for wear and replace as required. If possible, change them for titanium. The steel shafts wear and bend too easily.

If you intend to race your MRX-4 Touring Car model at a competitive level, I would also recommend you obtain and fit titanium pivot shafts, turnbuckles, tie rods and steering rods.

Examine the Drive System

Drive Belts need checking at regular intervals for wear, tension and damage. If deemed necessary, adjust the tensioning pulley until the belt can be depressed in the centre by no more than around 5mm. If the belt was slack, also examine the drive pulleys for wear. The teeth should provide a well seated fit for the belt teeth and not be rounded on the corners. If the belt teeth do not fit snugly, change the pulleys as soon as possible. For top level racing it may be prudent to replace all belts and pulleys after each race meeting.

Pinions and Spur Gears

Gears are a weakness on all Touring Car RC models. Head on collisions can easily damage the gear teeth on nylon and plastic spur gears. Heavy impacts can also loosen the nuts or self tapping screws that hold the Nitro Engine in Position, allowing the pinion gear to pull out of mesh slightly and rip the tops off the teeth on your spur gear. To minimise this possibility, fit bolts with locking nuts to the Nitro Engine mount and remember to check them for security after every two or three runs.

Don't Neglect the Ball-Joints

Ball joints always cause problems. For top level Nitro Touring Car racing, the plastic ball connectors should be checked and if deemed necessary changed after every meeting. A simple thing like a loose fitting connector popping off could easily end your race, so better safe than sorry.

Steering Servo and Servo-Saver

Servo Gears
The MRX-4 steering servo is also prone to damage. In high speed crash situations, the fragile gear teeth of the servo can be broken off, rendering your expensive servo useless, so be sure to obtain a good quality "Servo Saver". Check out my Servo Information article.

Stabilizers

If body roll on your Mugen MRX-4 is a problem, handling can be improved with the use of stabilizers, anti roll or sway bars, stiffer tuning springs and, or, thicker silicone oil in the dampers.

Don't Forget those Bearings

If your used Mugen Touring Car comes with plastic and sintered brass bushings (ring type bearings), check the shafts that run in them for wear. Dust and grit can get into these bearings and abrade the shafts. Therefore, you should replace them all with shielded ball bearings. If the model has been run with ring type bearings, you may have to change all the axles and driveshafts. For more information, take a look at my article, How to get the best from your Bearings.

Finally, good luck with your MRX-4 model and good racing.

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Manufacturers and Brands Catalogued, Listed and Reviewed by RC-Scrapyard.

At present, the RC Model Manufacturers, Brands and Distributors covered by us are: ABC Hobby, Academy, Acme Racing, Agama Racing, Amewi, Ansmann Racing, ARRMA, Team Associated, Atomic RC, Axial, AYK, Bolink, BSD Racing, Capricorn, Carisma, Carson, Caster Racing, Cen, Corally, Custom Works, Durango, Duratrax, ECX - Electrix, Exceed RC, FG Modellsport, FS-Racing, FTX, Fujimi, Gmade, GS-Racing, Harm, HBX, Helion, Heng Long, Himoto Racing, Hirobo, Hitari, Hobao, Hong-Nor, Hot Bodies, HPI, HSP, Intech, Integy, Jamara, JQ Products, Kawada, Kyosho, Losi, LRP, Maisto, Mardave, Marui, Maverick, MCD Racing, Megatech, Mugen, New Bright, Nichimo, Nikko, Nkok, Ofna, Pro-Pulse, Protech, PTI, RC4WD, Redcat Racing, RJ-Speed, Robitronic, Schumacher, Seben, Serpent, Smartech, Sportwerks, Step-Up, Tamiya, Team-C Racing, Team Magic, Thunder Tiger, Tomy, Top Racing, Traxxas, Trinity, Tyco, Vaterra RC, Venom, VRX Racing, WLToys, X-Factory, Xmods, Xpress, Xray, XTM, Yankee RC, Yokomo, ZD Racing and Zipzaps.

This is an ongoing project, with new and "lost in time" RC Models and Brands being added as they are found and although most of those listed above have been covered in relative detail, some are still being researched and will be completed in the near future.

RC Information and Advice:

Hints, Tips and Information

Dampers

   Dampers, Shock Absorbers, Shocks - call them what you will, they are one of the least understood, but most important tools you have for adjusting the handling characteristics of your RC model.

   In this article, I will endeavour to explain just what you can achieve by making simple tweaks to your shocks, and how these tweaks can keep you ahead of your opposition on the track.

   In dictionary terms "Damper" is described as - "A mechanical device to absorb the energy of sudden impulses." - In plain language, they stop your car from bouncing all over the track.

So how do Dampers work?

Basically what you have is a small amount of silicone oil contained in a sealed cylinder. Through the centre of that cylinder is a metal rod, and on the end of that rod, a piston with a number of small holes in it. Pulling, or pushing the rod in and out of the cylinder, your will notice a certain amount of resistance as the oil is forced through the holes in the piston.

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Hints, Tips and Information

The Importance of Balancing your Model Car Wheels

   The day I passed my driving test at the young age of 17, the first thing I did was to drive over to my girlfriends house and take her out to a long straight stretch of road close by, where the boy racers would often congregate. No one was around that day, so the road was relatively quiet. I slowly went through the gears and we were soon up to 65 with no problems, but as we got closer to 70, my hands began to sense a small vibration on the steering wheel. By the time we hit 75, the steering wheel and the whole car was vibrating wildly. My girlfriend was hysterical, screaming for me to "slow down!" I did of course and tried to calm her down.

   Back home I told my dad what had happened. He then reminded me that just the week before we had put on a new set of front tires and suggested the wheels were probably out of balance. Sure enough, after the wheels were re-balanced, at 85, 90, the car was steady as a rock and drove perfectly.

   As I got deeper into RC, that memory returned and I realised to be more competitive I would have to balance all my wheels.

How I Balanced my Model Car Wheels

Wheel balancing equipment for RC cars is now available on line and from most RC model shops, but back then I had to make my own using the rear end of an old Tamiya F1 car.

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