Boost/pressure leaks will be found in any piping or part that is between the turbocharger compressor\supercharger outlet and the head of the engine. Boost leaks can create false MAF readings and corelating expected manifold pressure altering the expected charge tables having a negative effect to relative cylinder filling.
A leak between the compressor outlet and the throttle body depending on calculated airmass can thus create a poor response to commanded lambda and in a lot of cases cause a global rich condition. If the leak is in the intake manifold respectively it can a negative effect to the idle function and others resulting in a poor operating conditions including fuel millage.
Any effect to the pressure system can affect the compressor efficiency. Generally speaking when there is a leak of some kind this can also cause the compressor to exceed efficiency ratios including temperature which following rule of thumb to isentropic efficiency the result is less efficient power output after combustion event. Basically lowering horsepower and torque levels and placing higher stress on the engine.
It is highly advisable to perform the diagnostic test and any applicable resolutions to thus maximize the performance of the vehicle in general and provide the best calibration results.
Exhaust system leaks can cause back pressure and scavenging issues on a naturally aspirated car and can cause slow spool for a turbocharger and adverse lambda readings. If a leak is persistent in your exhaust anywhere in the manifold or before the O2 sensor, there could be calibration problems that can halt tuning and cost you a lot of unnecessary money and time. As example the O2 sensor pre catalytic is used in a closed loop system for most modern vehicle control units, These readings are crucial for maximizing not only fuel millage but actual cylinder combustion efficiency with a direct affect to performance and all aspects of operations.
Specific to back pressure and to note the aforementioned isentropic compression, Any alteration to the pressure ratio will have a direct affect to the charge efficiency including combustion with direct affect to power output of the engine.
You can check for signs of a leak by inspecting for carbon build up around flanges. A preventative measure here is replacing gaskets when you change out parts like the exhaust manifold, downpipe, or turbo.
We highly advise inspection of the exhaust components prior to any calibration service in order to provide the ideal state to result with the best performance and quality of the BMS dyno tune.
Before going to the dyno it's important to make sure that your car is operating as it should mechanically. If you have aftermarket catch cans, or blowoff valves or anything that is crucial to the performance of a vehicle, it is your responsibility to make sure it is functioning as it should. If a blowoff valve is sticking open, it will cause plenty of issues when it comes to calibrating the control unit/s of the car. If your catch can is plumbed incorrectly or needs to be emptied, this can cause problems as well. Even if you have poorly fitted intercooler piping that bangs and bounces in the engine bay, this can cause the car to pick up false knock making it impossible to dial in spark timing as the vibration of metal on metal can set off the knock sensor. You can check for false knock by running higher octane fuels in your car. If the knock doesn’t go away, it is most likely false, but you will still need to figure out and fix the issue that is causing it before going to the dyno.
Fuel System Components
The fuel system is extremely important on any vehicle. You must be able to supply the necessary amount of relative fuel mass to provide the desired airmass and cylinder filling or cylinder charge to be bridged. If your car can’t supply this fuel, then you are directly limiting the cars power potential. This is especially prevalent on boosted vehicles. If you are upgrading your turbocharged/supercharged with bigger options or higher levels of pressure, then you will also need to make sure the fuel system is upgraded accordingly if needed. This will have a different approach varying platforms so it is important as the customer to consult with the calibrator and find out what they recommend for your power goals. That way, when you show up to the dyno, your fuel system will can keep up with your car's air delivery and won’t get in the way of it making power.
Another thing to watch out for here is if you have recently upgraded your fuel system. Any leaks or issues here will bring an immediate halt to tuning and could cost you a serious amount of money if they are left unchecked.
Spark plugs are a commonly overlooked item when it comes to modifying a car. In a lot of cases when it comes to modifying a car, it will be important to make sure you are running the appropriate heat range and gap on your spark plugs. Running higher boost pressure sometimes necessitates running a colder heat range spark plug and a smaller plug gap.
It is also important, when preparing for a dyno tune, to make sure your plugs are in good working order. If they are old or fouled they will certainly cause problems with the calibration. If they are improperly gapped, you will immediately run into spark blowout upon turning up boost pressure. Don’t let a set of $40 spark plugs cost you a tremendous amount of extra dyno labor or possible re-tune fee.
This one should be a no-brainer. In order to calibrate your car for high performance conditions, you have to simulate high performance conditions. This means repeated wide open throttle pulls on the dyno with much less airflow than what is found in the real world since the fans not being able to fully simulate actual air flow on a dyno. While it is the job of the operator to make sure the car isn’t overheating, it is your responsibility to make sure the car is up to the task of supporting this kind of abuse. This means that you should make sure the oil levels are where they are supposed to be, and you should also make sure the oil is relatively fresh. That means that the oil is closer to being new than it is to being ready for a change. You will be needing the oil to perform at its best in order to get the best results.
Wheels and Tires in Good Condition
While wheels are not often a problem, tires can be a big one. On the dyno, they will be subject to high speeds and loads. Since the car is strapped down, there is more weight applied and they are going to be repeatedly spun up to higher speeds than what they would see under normal driving conditions. It is important to make sure that they have the appropriate amount of air in them, that they are not leaking, and that they have adequate tread as well. If the tire is old or is starting to come apart, it should be replaced before getting on the dyno. If there is a nail in the tire or any other foreign object, it should be removed and the tire repaired as you wouldn’t want it to come out while on the dyno and damage something in the shop. A tire blow out on the dyno can cause damage to both your car and the dyno itself. At worst, anybody standing within several feet of the dyno can potentially be hurt as well. None of this should happen but it does. Being proactive about safety and vehicle health is critical.
Motor mounts are not something that most people pay attention too. If you have upgraded motor mounts, it is important that they are installed correctly and that nothing is loose. If you have OEM mounts, it is important that they are in good working order and not blown out or loose. Running on the dyno is like running on the race track. If something could go wrong there, it can go wrong on the dyno too. It is never a good thing when a motor gets torqued off its mounts as this will cause you some major problems. So make sure they are secure before coming to the dyno.
Compression/Leak Down Test
Knowing that your engine is healthy before getting on the dyno goes a long way towards understanding the numbers you end up with after the calibration process is complete. If your numbers are uncharacteristically low, it could be due to an unhealthy engine. Furthermore, putting an engine that is already hurting through more punishment is not advised as this can cause even more wear and tear.
This may all seem like a lot for a dyno tune, but in the end the peace of mind is worth it. Aside from the dyno, these things should all be paid attention to regularly. Should any of the issues listed above effect you, finding out on the dyno is the most expensive way to learn about them when a little pre-dyno inspection could go a long way to saving you money, time, and heartache.
Borescope cylinder\valve inspection
While performing the compression test we recommend bore-scoping each cylinder to ascertain the status of each. This can provide details as to current condition of cylinder walls or if there is excessive scoring as well as signs of detonation. Seeing condition of the valves can also provide status to detonation and other mechanical issues. Signs of excessive carbon buildup/oil will provide a direction in order to resolve. Buildup of oil or excessive oil content can directly lower octane thus having a negative effect to combustion efficiency which results in lower power output and capabilities
As you can see it is highly advisable to address all of these things when wanting peak performance to your vehicle specifically when wanting more power output. These issues can alter fuel millage and general driving conditions as well.