Chrysler 6.1 Hemi (SRT 8) Tuning

"All you need to know about tuning and performance parts on the Chrysler 6.1 Hemi engine!"

Taking the 5.7 this 6.1 engine had new coolant channels, including oil jets to cool the pistons. The forged crankshaft, lighter pistons and stronger con rods make for a great tuning base.

The Chrysler 6.1 Hemi have loads of potential and with carefully picked sports enhancements like remapping, turbo improvements and camshafts you will really maximize your driving experience.

Our aim here is to examine the options for your 6.1 Hemi tuning and report on the best upgrades.

History, Power & Specs of the Engine

425 bhp (317 kW; 431 PS) at 6,200 rpm and 420 lbft (569 Nm) of torque at 4,800 rpm

  • 2005–2010 Chrysler 300C SRT-8
  • 2006–2008 Dodge Magnum SRT-8
  • 2006–2010 Dodge Charger SRT-8
  • 2006–2010 Jeep Grand Cherokee SRT-8
  • 2008–2010 Dodge Challenger SRT-8

Tuning the Chrysler 6.1 Hemi and best 6.1 Hemi performance parts.

Best 6.1 Hemi modifications

The top 6.1 Hemi tuning mods on an engine are sensibly the ones that give the best value for money.

We won't be swayed by popular 6.1 Hemi tuning mods, they need to be cost effective.

The cam profile plays a big part in the engines power output so cam upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen cam profile, so large power band gains are on offer for cam upgrades.

Fast road camshafts tend to increase the power through the rpm range, you might lose a little low end torque but high end rpm power will be higher.

Motorsport and race camshafts, increase the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Competition cam won't do well if in heavy traffic.

You should ideally match your torque band to your preferences so for a road car stick with a shorter duration 6.1 Hemi cam

Some 6.1 Hemi engines respond better to mild camshaft durations check your engine on a rolling road.

The ecu map and fuelling also have a large bearing on the torque gains you'll make.

Longer valve 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.

Please watch our video which covers the 5 principles of tuning your car. Be sure to keep up with our latest YouTube content and subscribe.

Best Engine Mods for your car

  1. Engine Tunes - engine tuning/remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
  2. Fast road cams are one of the most significant mechanical changes, but they must be installed by someone who knows what they're doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft.
  3. Intake and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
  4. Upgrades to turbochargers and superchargers - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.
  5. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.

Typical stage 1 mods often include:
Sports exhaust header/manifold, Remaps/piggy back ECU, Fast road camshaft, drilled & smoothed airbox, Panel air filters, Intake manifolds.

Typical stage 2 mods often include:
fuel pump upgrades, Sports catalyst & performance exhaust, Fast road cam, Ported and polished head, high flow fuel injectors, induction kit.

Typical stage 3 mods often include:
Adding or Upgrading forced induction (turbo/supercharger), Twin charging conversions, Competition cam, Crank and Piston upgrades to alter compression, Engine balancing & blueprinting, Internal engine upgrades (head flowing porting/bigger valves).

 

The 6.1 Hemi engines are great to work on and we note that there is a lot of mods and performance parts out there.

 

Remaps will help fully realize the full potential of all the tuning parts you've done to your 6.1 Hemi.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but your results will rely on the tuning parts you've carried out and the condition of your engine.

Feeding air into the 6.1 Hemi engine is the aim to any engine modification job.

The intake manifolds flow rates are important because this channels the air from the filter and allow it to be fed into the engine cylinders.

Structure and rate of flow of the Air Intake manifolds can make a substantial improvement to fuel engine efficiency on the 6.1 Hemi.

Commonly we find the plenum chambers are improved through performance upgrades, although a few manufacturers provide decently flowing plenum chambers.

Adding a 6.1 Hemi larger valve kit, doing a bit of port matching and head flowing will also improve torque, and as an added benefit will permit a greater torque increase on other modifications.

Turbo upgrades

NA (naturally aspirated) engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your 6.1 Hemi

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

If the engine is turbocharged, upgrades are going to make more power and most turbo engines are built with uprated components.

There are practical limits for every engine, with some being incredibly solid and some only just able to handle stock power

See where you'll find these limitations and upgrade to more solid crank and pistons to survive the power.

We see many tuners spending a loads on turbocharger upgrades on the 6.1 Hemi only to experience the 6.1 Hemi throw a rod just after it's been finished.

Bigger capacity turbo chargers tend to experience a bottom end lag, and smaller turbo chargers spool up much more quickly but do not have the peak end torque gains.

Thanks to progress the world of turbo chargers is always increasing and we are seeing variable vane turbo chargers, allowing the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust flow into two channels and flow these at differently profiled vanes in the turbocharger. They also help the scavenging effect of the engine.

It is common that there is a limit in the air flow sensor AFM/MAP on the 6.1 Hemi when a lot more air is being sucked into the engine.

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

Adding a supercharger or additional turbo will make large power gains, although more difficult to get working. We have this feature on twinchargers if you want to read more.

Fuelling

When you boost the power you will need to increase to the fuel system.

 

More power needs more fuel. We strongly recommend you to be generous with your injectors flow rate.

As a rule of thumb add another 20% when fitting an injector, which takes into account injector deterioration and gives a bit of spare capacity should the engine require more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Exhaust

Only look to uprate your exhaust if your current exhaust is actually causing a restriction in flow.

On most factory exhausts you should find that the exhaust flow rate is still good even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts can help increase the flow of gases through the engine.

But if the exhaust is too large, ie: it's over 2.5 inches bore, you will lose much of your flow rate and end up losing power and torque.

Typically exhaust restrictions come around the filters installed, so adding a higher flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots, Issues & problem areas on the 6.1 Hemi

The 6.1 Hemi engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the 6.1 Hemi, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your 6.1 Hemi engine please join us in our friendly forum where you can discuss tuning options in more detail with our 6.1 Hemi owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

Please help us improve these tips by sending us your feedback in the comments box below.

We love to hear what our visitors have got up to and which upgrades work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these 6.1 Hemi tuning guides which get regular updates and revisions.

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One Response to “6.1 Hemi (SRT 8) Tuning”

  1. Fernando Boaventura says:

    Good day. I have a normal asperated Grand Jeep Cherokee SRT8 6.1 Liter with a few mods. Need to upgrade my tune as I wiped off back up. Have a Diablo Sport Predator. Can you or someone you know assist me in selling me a new tune I can download. I am from South Africa. Thanks. Fernando

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