1/10 Scale Electric Rally/Touring Car:

HPI RS4 - Porsche Turbo 911 - # 121 (Radio Controlled Model Review)

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History and Info:

Introduced by HPI (Hobby Products International) circa 1996, the Porsche Turbo 911 - # 121 - based on the entry level RS4 Touring Car chassis, came as an unassembled kit, requiring a Motor, ESC, Battery, Charger and Radio System. An ideal RC beginners model, it could be improved as the owners skill levels grew, with many hop-ups and upgrades readily available. A number of other bodyshell options were available (Check out our HPI Archive).

The 4WD model is belt driven, on an FRP double deck chassis, with ball differentials, coil spring over oil filled dampers, universal joint drive-shafts and bushings.

HPI RS4 - Porsche Turbo 911 - # 121

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To get the best from the HPI RS4, it needs to be fine tuned, to provide precise steering response and improve grip when cornering, so you don't slide off the track. Small changes can make huge advancements and our easy to understand guide will help you to the optimum Set-up for your individual driving style.

RS4
Manual

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Radio Controlled Model Accessories:

★ HPI RS4 Chassis ★

Buying a Used HPI RS4
Touring Car (and What to look for)

There are essentially three reasons you might want to buy a used HPI RS4 Electric 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 HPI 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 HPI 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 HPI 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 HPI RS4 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 RS4 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 RS4 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 Electric Motor 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 Electric Motor 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 Electric 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 RS4 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 HPI RS4 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 HPI 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 RS4 model and good racing.

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Or, check out our RC Model Car Setup Guide

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Manufacturers and Brands Catalogued and Listed 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

Bearing Seals

   If you were to ask anyone with a modicum of experience in RC, they will tell you that the best modification you can make to a basic RC model, is to add a set of ball bearings.

   Quite a few of the entrance level models at the time this article was written, come with plastic and sintered brass ring type bearings. If these bearings are installed in the model and coated with grease as advised in the car manual, dust and grit can be caught in that grease and be dragged into the bearing where it can abrade the shaft that spins in it and it won't be long before it becomes a very sloppy fit, causing all kinds of problems.

   But what should you look for when buying bearings? There are a number of types of seal used on ball bearings, and there is much debate concerning which is the best for RC.

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Hints, Tips and Information

Look after your Gears

   In RC there are a number of different gear teeth sizes we tend to use, based on two systems. Imperial and metric.

   The imperial system has sizes 24dp, 32dp, 48dp and 64dp. DP stands for Diametral Pitch and the number refers to the number of teeth per inch.

   The metric system has sizes 0.4m, 0.5m, 0.6m, 0.7m, 0.8m and 1m. M stands for Module and is the ratio of the reference diameter of the gear divided by the number of teeth.

   The different sizes are used basically for strength. 32dp gear teeth are larger than 64dp gear teeth, therefore the 32dp gears are by design stronger and for this reason are more commonly used on a number of entry level buggys, to help them withstand the knocks and crashes by drivers new to RC, and nitro models because of the higher torque levels involved. Also, the bigger the scale of the model, the stronger the teeth need to be.

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