GM Gen 3 and Gen 4 LSX Tuning Prep

GM Gen 3 and 4 LSX Tuning Preparation

                The GM LS platform is one of the most popular engines of this generation. You can pretty much find out anything you want to know about these engines from forums, Facebook groups and YouTube. With that said, I still see a lot of these cars come in completely unprepared for tuning. It is usually very simple things that the builder or owner could have fixed by taking just a little extra care. Hopefully this guide can help you to be better prepared for your tune appointment.

 

Basic Preparation

  1. Intake and exhaust system should be free of leaks. This is very important and one of the most common issues I see when a car comes in for tuning. If the car has any leaks in the intake manifold after the throttle body it will be nearly impossible for the idle to be tuned properly. In addition to that, if you are still using the MAF (mass air flow) sensor the fuel trims will be way off and the result will be an overly rich condition.

 

Exhaust leaks will also cause major issues for the calibration process. If there are leaks anywhere between the engine and the oxygen sensor(s) they will not read properly. This will wreak havoc on the closed loop fueling because it creates a false lean condition and the ECM will add fuel creating an overly rich condition. In addition to this, if there are exhaust leaks the vehicle cannot be tuned because AFR readings will be inaccurate. To prevent these types of issues ALWAYS USE GM OEM EXHAUST MANIFOLD GASKETS. A lot of header kits will come with gaskets. Don’t bother using them as most are the cheap graphite or foil type that doesn’t last long. OEM gaskets are cheap and will save you a lot of time.

 

  1. Check for fluid leaks and repair them if there are any present. This one is simple. You wouldn’t race your car with a leaking engine, transmission or rear end. Don’t bring it in for tuning this way.

 

  1. Fuel System: If the vehicle is equipped with an external fuel filter (Gen 3 LS vehicles) make sure that it has been replaced recently. In addition, 98-02 F bodies at this point are very old and I see a lot of poorly performing fuel pumps even on bolt on cars. If you are considering modifying one of these cars it’s a good idea to just go ahead and upgrade/replace the fuel pump and the wiring that powers it.

 

  1. Ignition system: If they have not been replaced recently install new spark plugs of the proper heat range and at the proper gap. Plug wires are also an area of concern. Some header kits have very poor clearance between the exhaust runners and the wires can touch and/or burn the stock wires or boots. There are many different options for aftermarket wires with angled boots and/or heat shielding. The point here is that the wires cannot touch the exhaust runners. They will burn and cause misfires.

Upgraded Camshaft Installs

                The most common next step for a LS is an upgraded camshaft. After install the car will of course need to be tuned. Often the installer will overlook mechanical problems because “It just needs a tune”. Please be sure to go over the same things mentioned in the basic preparation section in addition to the tips below.

  1. Check oil pressure: A very common mistake is that the oil pickup tube o-ring can either get pinched or the wrong size o-ring is installed. This can easily be seen when idle oil pressure is very low at idle. Typical hot idle oil pressure for a stock oil pump is between 30-40psi. If you are seeing oil pressure much lower than this it is likely that you have a problem.

 

  1. Pushrod Length: The LS series hydraulic lifter setup doesn’t have any valve adjustment in the traditional since. Pushrod length will determine your lifter preload. Improperly set lifter preload can result in a poorly performing engine and if it is way too loose the valvetrain will also be very noisy. Most cam kits will come with a stock 7.4” length pushrod. This is usually very close, but if you have installed a set of aftermarket heads, rockers or the cam is cut on a smaller base circle that length can change greatly. Sometimes this difference can be nearly ½”!

 

  1. Cam timing: Always double check this. Its super easy to align the cam in a LS engine, but it is not very easy to get down to it if this step is done improperly. After install spin the engine over a full cycle and check it again just to be sure. If the cam is off there is no way to tune around that.

 

 

Nitrous

                Nitrous gets a bad rap sometimes. Mostly because of improper use. It really can be just as reliable as any other power adder as long as it is installed and tuned properly.

 

  1. In addition to your basic nitrous kit there are some essential extra components you will need.
  • Nitrous bottle pressure gauge: It is very important to monitor bottle pressure. The car should always be run at the pressure that the system was tuned to or else it could run too rich or too lean.
  • Bottle heater: Used to regulate bottle pressure
  • Window switch and WOT switch or progressive controller: For both safety and consistency its best to take nitrous activation out of the driver’s hands. At minimum the vehicle should be equipped with a WOT switch in order to prevent the nitrous from being activated while the throttle is closed. For drag racers a progressive controller will be a worthwhile addition. The adjustability for changing track conditions can be very useful. An easy to use product that covers all 3 of these functions is the NOS Mini controller.
  • Nitrous purge kit: This is slightly optional, but for consistency at the track its good to be able to clear the line.
  • Ignition timing retard controller or 2 separate tunes for NA and nitrous: For customers that are running a stock ecu you will need some way of pulling timing when the nitrous is activated. I can just pull the timing out of the tune, but it will make the car a lot slower when nitrous is not being used. If you don’t have your own HP Tuners cable to be able to switch between tunes this can be a problem. A great solution is Lingenfelter’s timing retard controller. It’s nearly plug and play and very easy to use. The car will be wired so that the timing is only pulled out when the nitrous is activated.
  • Colder spark plugs. Heat range will vary based on how much nitrous

 

  1. Plumbing and install tips
  • Nitrous systems use a lot of AN and pipe thread style fittings. It is not recommended to use Teflon tape on these as it can sometimes get into the solenoids and clog them. This could cause major problems with either fuel or nitrous delivery. Instead, I suggest the use of liquid Teflon thread sealant on all pipe thread fittings. AN fittings don’t need any sealant at all.
  • Fuel Delivery: If you are feeding the fuel side of a wet nitrous system off of the stock fuel rail, be sure to remove the schrader valve. If it is not removed your fuel solenoid will not be supplied any fuel.

 

Also, if you are feeding off the rail the fuel system must be able to support the amount of horsepower that the car is making on nitrous. For example, if you have a 255lph fuel pump on a car that is making 450whp NA that is totally fine. The problem arises when you try to support another 150whp from your nitrous kit. The fuel pump cannot keep up, fuel pressure will drop, and the car will run lean. To remedy this problem, I typically suggest a secondary, dedicated fuel system for the nitrous kit. A small cell with its own fuel pump and regulator will supply fuel to the nitrous system. You can also use higher octane fuel in the cell in order to help support a higher-powered shot of nitrous.

Turbo and Supercharger

                In addition to this list of tips for prepping your turbo or supercharged vehicle it is also important to go over the items in the basic preparation list. These items are all the more important when adding boost.

  1. Check your piping for boost leaks: Always check your system for boost leaks. Use of good clamps and silicone couplers is very important. If pipes are constantly blowing off during the tuning process that is going to slow things down a lot and also it will be a great annoyance to you once you start driving the car. ***Intercooler pipes should have bead rolled ends or alternatively you can weld a few beads along the edge. This will give the clamps something to hold on to. Straight cut pipes are a no go. ***
  1. Proper routing of lines to blow off valves, wastegates and boost controller. If you don’t know or need a diagram just ask.
  2. Wastegate: For turbocharged applications this is one of the most important pieces of the system and it is often misunderstood how this operates. At minimum, you will need to know the boost level your wastegate spring is rated for. It must also be of the proper size to vent enough exhaust to slow down the turbine wheel. In addition to proper sizing, the wastegate needs to be installed in the exhaust in the proper location of the exhaust manifold or turbo hot side merge for it to function. Please ask questions or send pictures if you are unsure of any of these things.
  3. Boost control: there are many different types of boost controllers out there. What is right for you will be determined by the use of the car. For any type, diagrams can be provided to show you how to properly set it up to prepare for your tune.
  4. Supercharger belt should be replaced if it has not been replaced recently. A slipping belt will cause boost to build slowly, fall off early, or sometimes not build at all. Tensioner operation and belt alignment must also be checked. Improper alignment of the belt or a failing tensioner will cause the belt to be damaged and/or break. When a belt breaks at high rpm it can take out important and sometimes expensive components around it. If any of these things aren’t right you’re not going to have a successful tune appointment.
  5. Colder spark plugs will need to be installed. Heat range will depend on boost/power level.
  6. Sensors: The stock map sensor on most LS engines cannot read positive manifold pressure. This will have to be upgraded. Sensor type will vary depending on if you are Gen 3 or Gen 4 but there are plug and play 3 bar map sensor options for both. 
  7. In addition to the map sensor the intake air temperature sensor must be addressed. For boosted applications I suggest using a GM screw in type IAT sensor. The sensor requires a 3/8” NPT bung to be welded into the intercooler piping close to the throttle body.