High performance RX7 Tuning

"Wankel engines, what goes around comes around."

The RX7 was the car that made the Rotary engine cool.

With a displacement of only 1400cc it matches the power output of engines nearly twice that size.

The beauty of the Rotary engine is that it can enjoy much higher speeds without being subject to the same internal forces as a reciprocating engine.

This means that  you have a lot of scope for increasing the power without having to resort to extensive modifications. The turbo engine gives a lot of scope for tuning with the addition of a larger turbo, a hybrid turbo (uprated internals in a standard case) or a twin turbo setup. A tune/remap will help release more power in all cases.

Because the engine is so light it makes the car feel a lot faster than it should be, this also means you get a massive and noticeable hike in power from most modifications.

Rotary engines are specialist items but there is plenty of experts out there with a wide range of RX7 tuning options.

Weak spots include gearbox issues caused by loose mountings which can be addressed with a reinforcing frame. The issue usually manifests itself as an issue in 2nd-3rd gear changes and will get worse if ignored.

Oil leaks have also been reported but a number of specialist RX7 tuners offer stronger sumps with a better o ring seal.

When buying an RX7 you should ensure that it has been well looked after and properly serviced. These are specialist engines so need the attention of a specialist.

Reports of unreliability and requirements to rebuild are largely unfounded provided the car is properly serviced and looked after.

This is also an engine that requires you to read the manual, particularly with respect to starting and stalling the engine. As the engine is very high revving to many drivers it can feel quite powerless low down and they will generally stall it. If you get it badly wrong you risk flooding the engine and it requires dealer attention.

Best Engine Mods for an RX7

Please watch my video for an introductory overview on tuning the RX7's Wankel Rotary engine. RX7 Engine Mod Guide

  1. Weight reduction - cut weight by replacing body panels with carbon fiber
  2. Intercooler - reducing the intake charge on Turbocharged RX7's is an essential upgrade.
  3. Suspension - much can be done to improve the handling with a decent set of coil overs
  4. Brake upgrades - stopping the car is just as important as making it go
  5. Lighter flywheel - reducing the rotational mass will help throttle response and improve the engine response
  6. Exhaust upgrades - expelling exhaust gases is a big priority and on a high revving engine like this it makes a big difference.
  7. Porting - enlarging and improving the intake port flow is a great rotary mod.
  8. Intake improvements - Removing restrictions on the intake are important but bear in mind the stock RX7 intake actually flows quite well so you'll need to have added a lot more power to make this a viable mod.

Weight reduction mods for the RX7

The car is relatively light but this shouldn't stop you from taking it further with a carbon fiber bonnet and even carbon fiber wings and panels. Lighter cars are faster and handle better.

Obviously, removing the seats, carpets, radio, seat belts, headliner, and air conditioning renders the family vehicle unusable but we bet you didn't buy the RX7 as a family car!

With many current run flat tires, you may limp home without air in your tires, making the spare useless. A light racing seat will further minimize weight.

Lighter cars perform better.

The removal of glass windows and replacement with Lexan or Plexi saves weight, the primary front screen should remain as safety glass.

Many firms provide replacement body panels in aluminum, GRP fiberglass, or carbon fiber for optimal weight reduction and strength. Lifting the hood reveals how heavy the panels are in a vehicle, so removing as much metal as possible may save a lot of weight.

Many panels are not properly made, therefore always check the panel/bonnet/hood on the vehicle for size before drilling and installing bolts etc.

Many other metal elements may be made lighter by drilling holes in them, while retaining most of the structure's stiffness.

In addition to removing the door hinges and locks, the welding process adds strength to the car's body shell. Even when replacing items on the automobile, such as brake pads or discs, it is important weighing them beforehand.

For example, alternators, water pumps, flywheels, even pistons and blocks are needlessly hefty, therefore constantly seek for methods to decrease weight. Saving 200g in 5 different locations lowers weight by 1 KG.

Intercooler upgrades on the RX7

Get an uprated intercooler to save the power lost by heat gains ON A TURBOCHARGED ENGINE - this is not a NASP mod. If you are serious about power gains then lose the air conditioning and fit a larger intercooler mounted at an angle in the engine bay. The intercooler will benefit from a bonnet vent if possible.

Relocating the intercooler and putting a vent in the front bonnet will also help minimize heat soak and push up the power figures.

There is more oxygen taken in the colder the air is, a simple fact we learned about in our chemistry and physics classes.

An intercooler is a radiator that cools the air charge before it goes into the engine. You should put an intercooler in front of the radiator so that it gets a lot of nice, cold air.

Some cars have top-mounted intercoolers that draw air in through the bonnet. This may mean that when the car is at a stop, it is being hit by warm air from the engine but seems well suited to the RX7 design and layout.

A top-mounted intercooler makes it easier for air to get into the engine.

All turbo cars will benefit from having an intercooler, and there are ways to improve the factory-fit intercoolers that come with the cars.

Keep in mind that you want to get as much air into the engine as possible, so if the internal core of the intercooler is in the way, you will lose power.

As a general rule, you would use 3 litres of intercooler capacity for every 100 horsepower. If your car has between 150 and 400bhp, this isn't very good.

Between 5% and 10% of power is gained from a more efficient intercooler design over the factory one. This is based on a temperature drop of 35C-40C. The bigger the difference between intake temperature and ambient temperature, the more cooling effect there will be.

As time goes on, even the most efficient intercoolers will get hot. When you drive for a long time with a lot of high-boost, the intercooler starts to get hot.

In general, the bigger the intercooler, the longer it can withstand heat soak. So if you want to get the most out of an intercooler, you need to get the right size.

RX7 Suspension mods and upgrades

A set of coilovers will stiffen the handling and if this is matched to a rear strut brace you can have a very sharply cornering RX7. Reinforcing the front and rear suspension turrets is beneficial and gives noticeably improved handling on older cars.

Talking with some of our members who own RX7s we find that the rear wing is actually quite important and that without it the back is pretty light at high speed (over 70mph).

People on the track care about how quickly they can take turns. Suspension plays a vital role in this and it's more subtle than just dropping and fitting stiffer springs. There are no bumps or potholes on the track, so it's easy to drive on with the hard low suspension so you don't have to worry about the ride quality because there is very little to upset it.

On the road it's a totally different story! So let's talk about setting a suspension up on your RX7 optimized for the road.

Suspension parts (bushings/bushes) that are made of rubber will break down as the car gets older. You might hear a noise or bump when the suspension moves and you might get grinding all of which are signs of this wear.

Changing to polyurethane bushings is a great way to improve the basic set-up. This is your first step and will tighten up the handling.

There are a lot of things to think about when you set up and choose the suspension for your car.

Engineers must think about speed bumps, uneven surfaces, passenger comfort, and road noise when they make a car's suspension - these are all factors you need to consider as well.

Track cars are set up for the driver's preferences, and the best settings for track times isn't just this personal preference but it also depends on the track.

A good suspension system keeps the tires on the road at the right angle for the most contact with the ground, so they stay on the ground as long as possible thereby maximizing your grip.

To avoid body roll, the car's center of gravity must be low. To drop an RX7 we would look to around 30mm, TorqueCars recommendation should suit most drivers and most road conditions.

Mistakes and myths about the suspension.

  • Buy a non-adjustable suspension package that lowers the car 30mm and think it will be great.
  • Most kits are very generic, and many of them say that they can be used on any or many types of cars.
    You can't just say that one suspension will work with any engine, wheel, or RX7 weight because it doesn't work that way (the diesel engines are pretty heavy).
  • Angles that aren't right for the driveshaft and gearbox could cause them to break down as the wear is accelerated at this extreme angle.
  • Changing the ride height also changes how the suspension moves when it's under a lot of stress, which can cause scrubbing tyres on the arches or at the very least premature tire wear!
  • Another bad idea is to buy reduced springs and use standard dampers or to buy sporty dampers and use standard springs.

Because the whole suspension system should be looked at rather than just one component it needs a little knowledge and insight.

Cars look good slammed low. But you lose ground clearance, your tires rub against the wheel arches, and speed bumps become impediments that are impossible to get over.

Going too low can be catastrophic when the sump of a lowered car gets hit by speed bumps. This will rip off a large part of the engine and the front skirt. Lower doesn't always mean better, and it doesn't always have to be that way.

It's a good idea to drop your car about 35mm for most cars on the road, and 30mm for RX7s that have been upgraded with new suspension (sporty versions which already have lower suspension).

When the car is on regular suspension and has 17" rims, these tolerances may be a lot lower. But lowering the car could cause a lot of problems.

The goal should always be to improve the car's handling, and lowering the car helps this but you also need to look at the brakes, so we'll deal with this topic next for your RX7.

RX7 brake mods

We shouldn't really give attention to making the RX7 go faster without looking at the brakes. There is a nice range of large brakes available such as the KAD 356mm discs mated to 6 pot calipers, but we have to question if the average driver needs such meaty anchors.

It's common for people to think of bigger brake discs first when they talk about brake upgrades. But don't forget about the pads. They're more important than the discs, and bad pads can make your RX7's handling bad.

If you want to be able to stop quickly, you need brakes and brakes that you can rely on.

So this is how a brake works: A friction pad is pressed against the disc, which turns kinetic energy into heat, slowing up the car.

This head dissipates, slowing down the car's forward speed. There is a lot of heat buildup in the brakes when you brake a lot. This is particularly evident at night time, where the brakes glow brightly with heat after they have been used a lot in motorsports events.

When you press the brake pedal, the force is sent to the servo, which uses engine power to make your foot pressure more powerful and make the brake work.

The extra pressure comes from a tube filled with braking fluid that goes to the friction pads and puts more pressure on them (liquids do not compress like air) but if this fluid has water or air bubbles in it, it will create a spongy brake feel.

Brake pads for the RX7

The pad spreads the heat from the brakes over the discs, so the cooler the disc, the better.

Having a vent in the middle of a disc makes it easier and faster for the disc to cool down.

Help keep your pads "clean and sharp" by increasing them in contact with a nice cool brake disc, and vents and grooves or drilled discs help with keeping gas vapor from building up between the pad and the disc under use.

Drilled discs also clean the pads removing uneven wear more than a solid disc would. Bigger discs = better cooling, although they may necessitate a different alloy wheel to get them to fit in some cases.

Brake pad upgrades for the Rx7

It doesn't matter if the high friction brake pads make noise and dust if you are primarily concerned with performance, the stopping power is what counts.

Please note that a high friction compound is used to make racing pads, and it often works best when the temperature is high and are not suitable for road use.

It's not good to use race-grade brake pads on the road when braking is done on cold pads or in short bursts. They only work when they're very hot and they make a lot more noise and greatly wear the discs.

TorqueCars found Pagid and Black Diamond fast road pads to be an excellent balance between braking and wear for daily conditions with the occasional fast road or track day thrown in.

A lot of high-performance brake pads don't make a lot of brake dust and last longer than normal brake pads, even though how you drive will affect the pads and discs.

Benefits of Larger Brake Discs & Calipers

A bigger disc will have more friction and spread out more heat, so you will start to benefit right away with shorter stopping distances.

With a big disc conversion kit, you will be able to feel the brakes better and be able to tell when the car starts to lock up more quickly.

When you're done with upgrading your calipers and pistons, you'll get to investigate the next thing: ( pistons which are employed in pushing the calipers and squishing the pads to the discs).

The more pistons you have, the more clamping force you have, which means you can use bigger pads.

To get the most out of upgrading the discs, you should add better pads, calipers, and pistons and even may need to improve the brake servo and reservoir.

Even the standard brakes can be greatly improved with a high friction performance pad, and there are plenty of vented and upgrades available for the standard size discs making them a straight swap.

Lighter Flywheels on your RX7

The flywheel is between the engine and the gearbox and spins with the engine effectively storing momentum.

When cruising, this helps the car tolerate speed fluctuations, but it hinders fast engine responses.

More power is produced by a lighter wheel since it lessens the engine's strain or effort to rotate the assembly and it reduces the overall weight of the RX7.

An engine optimized for racing revs substantially quicker than a standard engine and this is primarily achieved with a lighter flywheel.

To the driver, this is obvious on slopes with a lighter flywheel where it will bog down, but on a high revving Wankel engine you won't have this problem as much as you would on a conventional car due to the higher rotational speeds which require less weight.

Flywheel weights vary for maximum torque and free-revving ability. Your tick over may suffer if you go too extreme. Discussions concerning your application may be had in the TorqueCars forums where you can get specific pointers and suggestions.

TorqueCars recommends against putting holes in a heavy flywheel or sanding/grinding it to make your own lighter flywheel. Factory flywheels are balanced. A flywheel wobbling might harm the engine and reduce the red line and there is no way a DIY approach can work here.

Intake upgrades on the RX7

The key to power gains on the rotary engines is airflow through the engine, a low resistance high flowing air filter and porting within the engine are well-documented power adders.

Especially if there is a restriction in the existing setup caused by a large power gain.

Porting the Wankel Engine

If backed by extra air and fuel, expanding and flowing the engine ports may make a significant impact.

When tuning a rotary engine, you'll be boosting internal engine speeds, spool up times, and heat produced, which necessitates a new look at oil supply. To do this, we often see dry sump oil systems fitted on them.

If you're serious about enhancing power, the seals surrounding the engine rotors must also be flawless. Instead of using bigger seals, ensure that the rotor is absolutely flat, which needs the services of a professional since most machine shops will not be able to work to the required tolerances.

Seals will fail if they are not installed perfectly level or are not mated with a flat surface. It is a matter of when, not if, and is most likely one of the most significant contributors to engine difficulties.

Exhaust mods and upgrades for the RX7

A better flowing exhaust will further help to improve peak power. The turbochargers on the RX7 can be uprated to larger flowing units and because of the high RPM characteristics of the engine they are well suited to a twin-turbo setup to avoid lag.

Only consider replacing your exhaust if the present exhaust is producing a flow restriction.

The exhaust flow rate on most factory exhausts is good even with minor power improvements, but once you start pushing up the power levels, you'll need to obtain a stronger flowing exhaust.

The Wankel exhaust gets quite hot and has been known to extend in length by a startling amount in certain racing scenarios, so quality is important here. Buying a cheap exhaust is a waste of money since it will not endure.

Choose the narrowest exhaust you can find; this will limit the exhaust flow rate; the optimum exhausts for power improvements are generally 1.5 to 2.5 inches wide. The form and substance are more important than the bore size.

Typically, exhaust restrictions are traced back to the catalyst and filters installed, so adding a freer-flowing race alternative such as a sports catalyst virtually eliminates this restriction due to its larger size and surface area, effectively raising the performance to levels you would expect without a catalyst installed while keeping the car road legal.

Why not join us in our Mazda forum and meet our other resident RX7 owners and swap tuning tips and advice with them. Let us know in the comments below if you've done mods to your RX7 and what you are planning and please share your tips with our readers, we are all here to share our experience.

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