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By Shahin Fard
In this article we cover ways to improve your cars performance, and by performance we mean more power and more torque. If you are scared of single figure MPG’s & have a Prius as your bedroom wallpaper, this isn’t for you.
There are so many options to improve your cars performance from air filters, panel filters, exhaust system, ECU remapping, engine upgrades and to the more extreme engine swaps. In this article we go through popular performance modifications for your car.
Introduction
Ever since I bought my first car, I’ve been obsessed with improving cars performance. When I was under 25 , the mods I chose had to be insurance friendly. The performance modifications were limited to cams, exhaust, air filter, suspension, and a big in car entertainment install. After I was insurance friendly and turned 25, I bought a Skyline GTR and learned a hell of a lot about performance tuning.
Firstly, let’s start with OEM or stock cars, they are designed to meet a wide range of criteria including fuel efficiency, comfort, drive-ability to an extent, and performance. Since price remains a cars key selling factor, manufacturers design and produce cars that fit the bill for what most car owners want, so often reliability is prioritised over all out performance.
When cars roll off the production line, most are de-tuned to what their true potential is. Car manufacturers do this for better fuel economy and to prolong the car’s lifespan. This gives consumers the impression that their vehicles are reliable when in reality, it is the true potential of the car that has been throttled. For example the new Audi RS3’s are hitting 10 second quarter mile times with very basic modifications.
At Compare Parts our ethos is that cars are a blank canvas, and we as enthusiasts can apply our own creativity to individualise them. There is no shortage of performance parts for car enthusiasts, on Compare.Parts we already have over 50,000 performance products listed Compare.Parts and we’ve only just started!
Tuning just one single component in isolation may improve performance somewhat, but combined with other performance parts, you will inevitably get much better results.
Generally speaking, improving a cars performance is dependent on the following three rules:
Modern automotive engines are controlled by an engine control unit (ECU) or engine management unit (EMU). The ECU is a digital processor that controls various parameters of the engine including fuel flow, ignition timing, power, fuel emissions, torque, and reliability. Manufacturers often set these parameters to meet design compromises between performance, market and legislative specifications, particularly with regard to emissions. Consequently, factory ECU firmwares fail to use the full potential of the engine, leaving car owners with an under-tuned engine.
Cobb Accessport Tuning device
ECU Flashing
Also known as remapping or chipping, allows you to reprogram your car’s computer to unlock more potential from your engine. You can read and edit the factory firmware from the ECU using a Laptop plugged into the onboard diagnostics (OBD) port.
Tuners can change the parameters such as Ignition Timing, Fuel tables, Target Boost to match your desired level of power, efficiency, engine, driving style and fuel choice.
A DIY option for flashing is to install a programmer or standard plugin chip that’s designed specifically for your engine.
For example the Cobb Accessport plugins into your OBD port and allows you to select different maps.
Syvecs S8 Standalone ECU
Standalone / Replacement ECUs
Dependant on the car you have, flashing your existing ECU may not be an option. In that case you need to completely replace your factory ECU with a Standalone ECU. Companies such as Link, Syvecs, AEM Motec, and Pro-Tune to name a few, all offer Stand alone ECU’s solutions for cars.
Standalone ECU’s offer far greater control and flexibility, with additional inputs, outputs, and safety strategies. Ryan (from Syvecs) demonstrated to me how quickly my ECU reacted to engine detonation, pulling igntion timing to save my engine. The Syvecs ECU is far more sophisticated than the ECU that came with my car when it was built in the 90’s! A good ECU will have safety strategies in place to protect your investment, and a must for anyone who is really pushing the boundaries of their car.
With any tune, the car will be running in a slightly more stressed state. This means more attention needs to be made to regular servicing such as fluid changes. It’s also important to remember that you must run your the car on fuel it was tuned with, quite often this is higher octane fuel.
Theory
The main objective of porting a cylinder head is to increase the amount of air with atomised fuel that enters the engine. Both the amount of atomised fuel and air, and the velocity of this fuel/air mix is important. The more air+fuel that can be fed to an engine during the engines combustion cycle, the more power the car will produce.
Inlet ports typically sit on the intake side of the engine, their job is to allow the flow of fuel/air mix from the fuel injectors to the inlet valves. This needs to be as straight as possible and free from obstacles. Obstacles can disturb the airflow, and upset the fuel/air mixture.
While standard cylinder heads work well, they are usually suboptimal due to manufacturing cost and design, particularly in port shape and surface finish.
Having a the cylinder head ‘gas flowed’ means reprofiling the exhaust and inlet ports in the cylinder heads to allow for more efficient flow of the fuel/air mixture in and exhaust gases out. If there are any materials in the valve guide that poke through the ports like valve stems these may be removed to avoid interrupting gas flow.
The Diy’er
This kind of work is often undertaken by professionals, and whilst it may be tempting to get a Dremel out and watch a Youtube video whilst you are grinding away at your inlet ports, you may actually make your head worse!
Polishing Ports
You may have heard the phrase “Polishing” or “Port and Polishing”, This means along side clearing the obstacles on the inlet and exhaust ports, they were polished. This was often for aesthetics, but with a more modern understanding of aerodynamics this was found to be counter-productive. In fact polishing your inlet / outlet actually decreases the performance of your engine. This is due to something in aerodynamics called the boundary layer effect, which causes drag. A slightly rough surface reduces drag and aids a better air/fuel mix.
Stroker Kits
A Stroker kit increases an engine’s displacement by lengthening the stroke of the piston. A Stroker kit will compromise of a forged crankshaft, forged I or H beam Con Rods, Forged Pistons, Gudjeon Pins and Piston Rings . Together in unison, they allow the piston to travel further up and down the cylinder, increasing the engines stroke. This increase distance the piston travels increases the amount of fuel and air contained within the cylinder, increasing the engines displacement.
To avoid the piston from hitting the cylinder head, adjustments are made to whether the piston connects to the Conrod, and the length of the Conrod maybe shortened.
There are lots of different stroker kits available from companies like HKS, Nitto, JUN, Manley, Ross Sport, Tomei.
This is an example using an RB26DETT comparing Standard Engine Specs vs a Stroked Engine
Standard
Stroker Kit
Oversized pistons
Continuous mechanical, thermal and chemical loading on the piston and cylinder causes the cylinder to change its shape (becomes oval) and the piston-to-bore clearance to become large. A worn out cylinder loses its compression ratio for effective compression stroke. This results in lost power and higher fuel consumption reducing the engine’s performance drastically. To correct the situation, the cylinder is rebored and a new piston or piston rings are fitted. Typically these are oversized in 0.5mm increments.
Drilling out the cylinder to a wider diameter will create more space in the cylinders for air and fuel. The increase in swept volume of the fuel/air mixture drawn into the cylinder increases the torque and power produced by the engine. Before you attempt this, be sure to take a stress test or have a mechanic measure the ovality of the cylinder liner and the piston to bore clearance (the running clearance). This will help you get the compression ratio right when removing any unnecessary material. It’ll also make it easier to find pistons that match the cylinder dimensions.
It is important to mention that not all engines are suitable for reboring. A good example is engines made from aluminium with liners in the cylinders. Most cast iron blocks can be rebored to a large size.
This is an example using an RB26DETT comparing Standard Engine Specs vs an engine with oversized Pistons
Over-sized Pistons
Whilst oversized Pistons does increase the displacement of an engine, the overall increase in capacity is very little vs a Stroker Kit.
Forced induction systems push more air into the cylinders. This can increase torque and horsepower by more than 50%. More air entering the cylinders enables the engine to mix in more fuel consequently producing more power.
There are several forced induction systems available to car enthusiasts including:
Turbochargers
These are air pumps that are powered by the exhaust gas leaving the engine. Turbochargers force more air to flow into the engine enabling it to produce more torque that naturally aspirated engine wouldn’t otherwise produce. There are a few downsides to this application though.
Superchargers
Turbochargers and superchargers work in a very similar way. However, while turbochargers force air into the engine by drawing power from the exhaust gasses, superchargers are belt-driven. Therefore, the supercharger’s effectiveness increases as the RPM increases. Additionally, this force induction system does not change the trajectory of the torque curve so it’s like driving a naturally aspirated vehicle but with more power.
Superchargers cause parasitic loss, which means they “suck power” from the engine to produce more power. The trade off is positive, as they generate more than they use.
They are not as efficient as turbochargers and do not provide consistent power distribution.
There are two main types of Superchargers:
Rotrex Superchargers are Centrifugal superchargers, they are very much like a Turbo, except they are belt driven. You often see Rotrex type supercharges on Honda engines. They provide a huge amount of power low down the rev range.
There are several different types of positive displacement superchargers such as the Harrop Supercharger pictured above.
It’s beyond the scope of this article to write above them all.
Other names you may have come across is Eaton, which is found in Mini’s, Jaguars and Mercedes Benz. They make a slightly whiney sound which sounds like a bit like a strangled car.
You often find these type of Superchargers on Big V8’s such as the Mustang, they effectively increase the displacement of the engine through compression of the air.
Nitrous Kit
While this isn’t a forced induction system per se, it serves a similar purpose of forcing more air to flow into the engine. Nitrous oxide has more oxygen than air in the atmosphere. Consequently, installing a nitrous kit helps to increase air entering the engine.
There are three types of Nitrous Kits
Dry Kit
A dry kit injects just Nitrous, its up to the configuration of the ECU (engine calibration) to increase the amount of fuel added in proportion to the amount of Nitrous added to the engine. It is also necessary to retard the ignition and in some cases use special spark plugs. This very much depends on the vehicle.
Wet Kit
A Wet Nitrous kit injects both Nitrous and Fuel into the inlet chamber. This is in addition to the Air/Fuel already added by the existing system. Again similar to a Dry Kit, ignition needs to be retarded to compensate for the additional air/fuel provided by the Nitrous system.
Direct Port
A Wet/Dry kit typically has a single nozzle that is around 6 inches away from your throttle. Direct Port has individual nozzles per cylinder and often sits on the inlet. Direct Port is used when a Single Wet Nozzle isn’t enough, and having an even distribution of Nitrous Oxide to each cylinder is important.
Crank polishing/grinding removes materials from the journals and reduces microscopic grooves and indentions. This ensures the oil and bearing have less resistance and also helps to maintain proper clearances for oil flow.
Another benefit of grinding the crankshaft is that it reduces the surface area of the crankshaft. A reduced surface area reduces the friction imposed by the journal faces. The polishing process also creates the journal corners which are invaluable in making the crankshaft stronger – they reduce the stress concentration at the corners.
Reducing friction in the oil flow increases air/fuel mixture enabling the engine to release more power.
Port matching the intake manifold to the intake port opening on the cylinder head is another great way to improve the performance of your car. When the ports are aligned, air transition from the intake to the cylinder heads is smoothened allowing for consistent airspeed and flow free from interruption.
Standard inlet manifolds are usually bigger than the cylinder head. This tends to slow down the airspeed and air/fuel mixture. This can also cause tuning problems and more importantly, a relatively low peak torque.
Fitting an intake manifold that matches the cylinder heads can increase airflow and increase the power produced by the engine.
Breathing modifications improve the “breathing” of the engine in naturally aspirated and forced induction cars.
They include changes made to the intake, exhaust and anything in between. Each modification helps a little bit in helping the car take in more air and expel it more efficiently.
However, if you make several breathing modifications, you’ll get quite big gains.
Increasing the valve opening height can also help improve the performance of your car. You can do this by changing the lever ratio of the valve rockers in the overhead valve engines, the profiles of the cams on the camshaft or the cam followers in overhead cam engines.
You can also consider installing a differently timed profiled camshaft to optimize the valve timing. This will improve burning efficiency as it will increase power at one range of operating RPM while reducing it at others.
Engine swaps are becoming increasingly more common from RX7’s running LS engines, Honda EG’s with K series Turbos, S15’s with VR38DETT GT-R engines, M3’s with M10 V10 engines, the list goes on.
This is one of the most expensive ways of improving your cars performance, and is totally dependent on your ultimate power goals. If you just want a little more power, then an engine swap is probably quite extreme!
Our experience
We put the heart of a Skyline GTR the RB26DETT into an Altezza, this upset the Lexus community who wanted to lynch us for not using a 2JZ!
In our Altezza the 1G-FE engine was toilet with 135bhp / 150PS from a 2 litre Straight 6. In stock form it produced 350bhp, which is a lot more than the measily 135bhp from its last engine.
For our Altezza, we converted the RB26DETT engine to Rear Wheel drive only, by removing the front differential, and bolted the engine to an RB25DET gearbox via a twin plate clutch. The RB25DET gearbox is rear wheel drive only. It’s mounted to the chassis with a custom made gearbox mounts, and a custom propshaft, connected to the existing welded rear differential.
Engine Swap Kits
These kits allow you to drop a new beating heart into your car without all of the custom fabrication work. This really makes life easier, and it pays to do research into your chassis and what engine swap options are available. Some of the kits go beyond the physical mounting and provide plug and play looms as well, this makes it even simpler to swap engines.
With any engine conversion, you have to remove the old engine, so you will get some money back selling that. Next you have to decide whether you are using your existing gearbox/transmission or using the one that comes with the engine with custom props/shafts and mounts. Some companies have manufactured adaptor plates which convert engines to a new trasmission / gearbox setup. For example on the 2JZ you can get an adaptor plate to a BMW N54 gearbox, meaning 2JZ goodness in your BMW.
Diff’s is another consideration. If you are putting a mighty LS engine with Twin Turbo’s on your RX7, the existing Factory diff may crap itself at the tremendous amount of torque generated by the V8 godness. If you are changing the diff, then you may need to change driveshafts, hubs etc, so it quickly gets expensive.
Aside from Engine, Gearbox/Trasminssions, Prop/Drive Shafts – Engine management will need to be changed. Luckily there are companies out there that make wiring loom conversions for popular conversions, or you can find a specialist who can make a wiring loom up for your car for an engine conversion.
These performance upgrades are just some of the ways you can improve the performance of your car.
Using one technique independently won’t make as much difference to your car, compared to using many together.
The choice of “power mod” depends on your budget, the power goal, and the limitations and flexibility for your engine and drivetrain.
We recommend starting with modifications that are cheap and make reasonable changes then working your way up to expensive and labour-intensive mods.
Shah is the founder of Compare.Parts, a pioneering marketplace dedicated to performance car parts. With a lifelong passion for automotive engineering and customisation, Shah's expertise spans decades, from hands-on builds to innovative solutions for enthusiasts and professionals. A recognised authority in the performance car community, he has built and owned some of the most iconic high-performance vehicles, including a 660bhp R35 GT-R, a 950bhp R33 Skyline GT-R, and a meticulously crafted HKS-inspired RB26-powered Altezza. Shah's deep technical knowledge and commitment to excellence drive Compare.Parts’ mission to empower car enthusiasts worldwide.