Modding uprating the Vauxhall C20LET engine!

Modifying and improving: "C20LET Modifications"

C20LET Modifications Guide

How to modify and upgrade the Vauxhall C20LET

"Comprehensive guide to tuning the Vauxhall C20LET engine!"

Our friends at TorqueCars are regularly getting messages asking about how to improve the C20LET from people wanting to know what are the best C20LET mods that work. So let us look into Vauxhall C20LET upgrades and outline the best modifications on this great engine and point out some potential pitfalls along the way.

Now we shall examine C20LET tuning and provide tips on the greatest mods that work. Vauxhall C20LET are good project engines and with carefully chosen modified parts like remapping, turbo kits and camshafts you will positively maximise your driving pleasure.

Just because particular tuning parts are are common on C20LET it doesn't mean you should fit it, so we'll concentrate on the ultimate tuning parts that will give your C20LET the biggest power gain return for your cash.

Without us subscribing to the mentality of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

C20LET induction kits

Improving air intake on the C20LET

You need air and fuel for an engine to work. If there is too little fuel then it will run lean, if there is not enough air it runs rich resulting in lost power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the whole point to any car tuning job to force more air into your C20LET but this has a knock on effect with the air flow sensor.

It is common that there is a limitation in the air flow sensor MAP/MAF/AFM on the C20LET when considerably more air is being drawn into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited bhp at a much lower level.

Engine intake manifolds take the air during the suck phase from the intake filter and allow it to be drawn into the engine cylinders.

The shape and rate of flow of the Intake headers can make a big change to fuel mixing and power on the C20LET.

On popular production engines plenum chambers are improved through aftermarket parts, although a few manufacturers provide decently flowing plenum chambers.

Increasing the C20LET valve size, doing a bit of port matching and head flowing will also raise performance, and importantly will permit a better performance increase on other tuning parts.

C20LET performance cam tips.

Some C20LET engines respond better to different cam durations so view each engine as unique.

The ecu map and fuel pump and injectors also have a large bearing on the torque gains you'll hit.

Extending exhaust or intake durations can alter the torque band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

Altering your C20LET camshaft will make a dramatic difference to the engine bhp. Choosing a higher performance camshaft profile raises the bhp accordingly.

NB: Fast road camshafts usually push up the bhp and torque throughout the rev range, you may sacrifice a little low down torque but the higher rpm power will be higher.

Motorsport camshafts, push up the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

For a car driven daily you must carefully try to match your power band to your preferences.

I'd be amazed if you find a C20LET Motorsport camshaft is a pleasure to live with when driving in heavy traffic.

Stage 1, 2 and 3 mods for the C20LET

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 C20LET parts:

Panel air filters, Remaps/piggy back ECU, Intake headers, Sports exhaust manifold, Drilled & smoothed airbox, Fast road camshaft.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 2 C20LET parts:

fuel pump upgrades, Sports catalyst & performance exhaust, Fast road cam, induction kit, high flow fuel injectors, Ported and polished head.

Stage 3 C20LET parts:

Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression, Competition cam, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger).

The C20LET units make great tuning projects and we're pleased to see that there is a lot of parts and tuning parts around.

ECU mapping will help unlock the full potential of all the modifications you've done to your C20LET.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your results usually depend much on the modifications you've applied and the condition of your engine.

Turbo modifications on the C20LET

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the C20LET.

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes excellent power gains.

When an engine is turbo charged tuning parts are simpler to install and you will discover turbocharged engines are built with uprated components.

There are weak spots for every engine, with some being very over engineered and some only able to handle stock power

See where you'll find these limitations and install stronger pistons, crank and engine components to utilize the power.

We've seen people spending a lots of money on turbocharger upgrades on the C20LET only to suffer the indignity of watching the motor throw a rod soon after it's been completed.

Big turbos tend to experience a bottom end lag, and smaller turbos spool up more quickly but won't have the peak rpm bhp gains.

Thanks to new tech the selection of turbo chargers is always improving and we now see variable vane turbo chargers, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust flow into 2 channels and flow these at differently designed vanes in the turbo. They also increase the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large bhp and torque gains, although more difficult to setup. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the C20LET

Don't overlook the need to pay attention to the fuelling when you are increasing the bhp - it makes the car more thirsty. It is important to over specify your injectors flow rate.

The rule of thumb is to add 15% capacity when buying an injector, which takes into account injector deterioration and affords a bit of spare capacity should the engine require more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended C20LET performance exhaust upgrades

The only time you should look to increase your exhaust system with an upgraded one is if your exhaust is creating a flow problem.

On most factory exhausts you'll see the flow rate is ok even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Please dont run with the biggest exhaust you can buy you'll slow the exhaust rate - the best for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

Typically exhaust restrictions are in the catalysts installed, so adding a freer flowing sports alternative will help avoid this restriction.

Catalyst removal (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the C20LET

Like most engines an C20LET, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the C20LET, failure to do this will exacerbate engine wear, on a tuned C20LET this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your C20LET why not pop over to the forums at TorqueCars where you can chat about C20LET tuning options and read about others projects who may be planning to do similar modifications on their C20LET.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with modifications on your C20LET, it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...


Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article