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FREQUENTLY ASKED QUESTIONS
Frequently asked questions
General
Oh, I love seeing this question pop up on facebook groups. First, a "protune" is a term created by cobb to signify that the tune is created by an authorized Cobb Protuner (someone they have vetted as professional and knowledgeable and trust to calibrate customer cars). I dont recommend talking to anyone that's a part of a different vehicle platform/community if they were "protuned," you will likely be laughed at. What protune is typically misunderstood as, is a DYNO tune. A dyno tune is where the car is strapped to a chassis dynamometer (or hub in some cases) and the tuner completes the tuning process in a safe environment where its easy to put load on the engine/or keep it at a steady state to target certain parts of the map! There are a lot of downsides to dyno-tuning as most dyno cells have floor dryer fans pointed at the car to cool it down (very inefficient and doesn't replicate real world, you would need a multi-million dollar wind tunnel for that), the perfectly smooth and balanced rollers also don't mimic real world roads either. Dyno tuning is safer, yes, but 90% of the time if a car is tuned on the dyno, the customer/tuner will test the vehicle on the street after the tune to verify everything. E-tuning is the EXACT same process, taking logs, adjusting based on logs and repeating the process until tune is complete. The benefits here are plentiful, real world conditions, real aerodynamic drag, you're the one driving in the environment and atmospheric conditions the car will see almost its entire life! The e-tuning process may be a little longer than a few hours on a dyno, but the ending result is the same if not better than dyno tuning. This changes a bit with high powered cars as tuning on the road can be extremely unsafe and high g's can make staring and focusing on a laptop a bit harder, so the dyno is a great tool there. The main downside from e-tuning is if you have a mechanical issue that is hard to find the cause in the logs and the car isn't already sitting in a performance shop equipped to diagnose! This explanation can go on and on, but that's the meat and potatoes!
Yes and no. I am focusing primarily on e-tuning for the next few months due to a recent knee injury requiring some extensive surgeries. I will be upgrading my dyno during this time as well to help provide even higher quality in-person tuning to those that are local! Street tuning can be arranged for vehicles that cannot be e-tuned. Contact us via e-mail for more information!
Essentially the flex fuel kit is just a sensor and module which relays the ethanol content from the sensor (in hertz) and converts to a voltage a connection to the ecu, which the calibration will automatically adjust between the 93 and High Ethanol parts of the tune (that contains high and low ethanol maps) for your measured ethanol content! This is still relatively new technology, before the flex fuel capability you just needed a calibration to run E85. In having separate tunes for gasoline and ethanol, the only difference is you have to manually reflash the correct fuel map on your accessport when you switch fuels, which takes less than a minute at the pump and very easy to do!
For FA powered vehicles this is called Stratified Warm-Up! Stratified warm up is designed by the Subaru engineers to make the car idle like crap (extremely retarded timing and wonky AFRs) in hopes to help break up carbon deposits caused by the direct injection system. It will do it for a minute or two, but throttle input should stop it. The cobb green speed update eliminated the ability to disable that function, but honestly its a good thing just in the chance it does limit carbon build-up, will increase power and reliability!
I only tune EPA and emission ready vehicles. High flow catted pipes throw codes but do not throw the car into limp mode, TGV/EGR/Air Pump deletes can cause issues for tuning - sometimes limp modes. It is your responsibility to know the laws and abide by them. With e-tuning i cannot physically see the car and tune based on what you tell us is on the car! (all aftermarket downpipes/jpipes tune the same way)
We cannot always accurately estimate how long it will take, but how many revisions. E-tuning is great for people to not only save a few dollars but work around hectic schedules. The length of time required to complete a tune varies based on the car, the mods, the type of tune, any issues that may arise, along with how available you are to datalog. E-tunes have generally consisted of anywhere from 4-10 revisions.
No, no part out.. Most of these tune or gauge related instances can be answered with the word document that is sent out before the tuning process. It has useful information from basic questions to maintenance and common issues. Knock is inevitable, dam drops are inevitable as consistent fuel cannot be guaranteed. Read through a recent post i made on Facebook that explains DAM and what it does!
https://www.facebook.com/MIGTUNED/posts/pfbid0249RfVMKswzngpVahaT4UfkZWZDWPjuhKjgVjRENmxRK1dCQok4zwgMerRq4jZBZkl
One of the most common cooling-system mistakes we see on street-driven Subarus is installing a low-temperature aftermarket thermostat because “cooler is better.” On a dedicated race car, there can be situations where a lower opening temperature makes sense as part of a complete cooling strategy. On a daily driver or street car, though, it can create more problems than it solves.The factory Subaru thermostat is designed around the temperature range the engine and ECU are meant to operate in. Coolant temperature affects far more than the gauge on the dash. The ECU uses engine coolant temperature as an input for warm-up enrichment, ignition strategy, idle control, fuel trims, emissions readiness, radiator fan control, and several other compensations. If the thermostat opens too early and the engine struggles to maintain normal operating temperature during light-load cruising, the ECU can spend more time operating in temperature ranges it was never intended to live in continuously.Running unnecessarily cold also isn't ideal for combustion efficiency. Engines are designed to operate with specific cylinder wall, oil, coolant, and combustion chamber temperatures. Lowering coolant temperature too far can increase warm-up time, reduce fuel vaporization, increase fuel consumption, increase deposits, and in some cases contribute to rich operation, poor drivability, or diagnostic trouble codes related to coolant temperature and warm-up performance. A common example across modern vehicles is a thermostat rationality or “coolant temperature below regulating temperature” type fault when the ECU determines the engine isn't warming up as expected.A lower-temperature thermostat also does not automatically give the cooling system more capacity. It simply starts coolant circulation through the radiator sooner. If the car is actually overheating under load, the real issue may be radiator efficiency, airflow, fan operation, coolant flow, trapped air, pressure control, head gasket problems, excessive cylinder pressure, or simply a cooling system that is undersized for the power level. Installing a colder thermostat can sometimes mask the symptom temporarily without addressing the actual cause.For almost every Subaru that spends the majority of its life on the street, we recommend a Subaru Genuine thermostat and OEM-quality gasket. Let the engine reach the temperature it was engineered and calibrated to operate at. If you're building a dedicated competition car where coolant temperature targets, radiator sizing, fan strategy, oil temperature, and ECU compensations are all being addressed together, that's a different conversation.Bottom line: a colder thermostat is not a cooling-system upgrade by itself. For a normal street-driven Subaru, the Genuine Subaru thermostat is generally the correct choice. If your car cannot maintain safe coolant temperatures with the proper thermostat installed, find the reason why instead of trying to make the engine run colder everywhere else.
When upgrading the fuel system on a Subaru WRX or Subaru STI, one of the most common mistakes is focusing only on larger injectors and a higher-flow fuel pump. Those upgrades are important, but the fuel pressure regulator, fuel lines, fuel rails, filter, and return system all have to support the same power and fuel-flow goals. Once a WRX or STI starts making significantly more power—especially on ethanol fuels—the factory fuel system can become a restriction even if the injectors and pump are technically large enough.A quality fuel pressure regulator for a Subaru WRX or STI is especially important on a turbocharged setup because injector flow depends on maintaining the correct pressure differential across the injector. As boost increases, fuel pressure should rise predictably with manifold pressure, typically at a 1:1 rate. If the regulator cannot maintain stable pressure, or the return side of the fuel system is too restrictive, you can see unstable AFR, fuel pressure creep, inconsistent fuel trims, or fuel pressure falling off under boost.Upgraded fuel lines and fuel rails become increasingly important as horsepower and fuel demand increase. A large fuel pump may have excellent advertised flow, but that flow can be reduced significantly by undersized lines, restrictive fittings, small filters, or a return line that cannot move enough fuel. This becomes even more critical on E85 Subaru WRX and STI builds, where substantially more fuel volume is required compared to gasoline.Fuel rails also play an important role in maintaining consistent fuel delivery across all four cylinders. On higher-horsepower Subaru WRX and STI setups, properly sized rails and a well-designed feed system help maintain stable pressure and reduce the chance of uneven fuel distribution. Depending on the setup, parallel fuel rail configurations can also improve consistency at higher fuel-flow levels.It is also important to understand that a larger fuel pump can sometimes expose weaknesses in the factory fuel system. A high-flow pump paired with a restrictive regulator or return line can create excessive base fuel pressure and pressure creep at idle or cruise. On the opposite end, inadequate feed capacity can cause fuel pressure to drop at high RPM and boost. Both situations can create tuning issues and reduce the safety margin of the engine.Bottom line: when building a Subaru WRX or STI fuel system, treat it as a complete system. The injectors, pump, fuel pressure regulator, feed lines, return lines, rails, filters, wiring, and fuel type all need to support the same horsepower target. If the fuel system cannot maintain stable differential fuel pressure from idle to redline, the injectors cannot deliver what the ECU calibration is commanding—no matter how large the injectors or fuel pump are.
When it comes to modifying your Subaru WRX or STI with an EJ-series engine, one of the most overlooked areas is the fuel system. Many owners focus on increasing airflow through upgraded downpipes, intakes, exhaust systems, and turbochargers without considering whether their fuel system can safely support the additional airflow and power. While the factory fuel system is adequate for stock applications, its limitations can become apparent as modifications and power demands increase. For many EJ-powered Subarus, upgrading the fuel pump, injectors, fuel rails, lines, and fuel pressure regulator should be a priority when planning performance modifications—not an afterthought once fueling becomes a problem.One particularly important component is the fuel pressure regulator (FPR). On EJ engines, fuel pressure instability and transient pressure fluctuations can contribute to hesitation, stumbling, and inconsistent air/fuel ratios, especially during throttle transitions and changes in engine load. This is commonly associated with the well-known STI fuel stumble issue. A properly configured aftermarket fuel pressure regulator, paired with appropriately sized fuel lines and rails, can help stabilize fuel pressure and reduce these inconsistencies. The result is potentially smoother throttle response, more consistent fueling, improved drivability, and a more predictable engine under both everyday driving and wide-open-throttle conditions. It's important to understand that not every stumble is caused by fuel pressure, but addressing genuine fuel pressure instability can make a substantial difference.Upgrading the fuel pump and injectors is equally important when increasing horsepower. Larger injectors provide the fuel delivery capacity necessary for higher airflow and boost levels, while an upgraded in-tank fuel pump helps maintain sufficient fuel volume as demand increases. However, bigger isn't automatically better. Injectors and pumps should be selected based on the engine's actual power goals, fuel type, and operating conditions. An oversized or poorly matched setup can introduce unnecessary drivability and calibration challenges. Fuel pressure must also remain stable relative to manifold pressure so that the injectors deliver the fuel quantities expected by the ECU. This is especially important on ethanol blends, which require significantly more fuel volume than gasoline to produce comparable power.At MIGTUNED, we recommend evaluating the entire fuel system when upgrading the downpipe or making other significant airflow modifications on EJ-powered Subaru WRX and STI platforms. Not every basic bolt-on setup requires a complete fuel system replacement, but planning these upgrades early can prevent running into fuel delivery limitations, paying for multiple tuning revisions, or replacing components twice as power goals increase. A properly engineered fuel system, combined with professional ECU calibration, provides the foundation for better drivability, consistent power delivery, and improved engine reliability. Ultimately, making more horsepower is only part of the equation—delivering the correct amount of fuel consistently and safely is what makes that power usable.MIGTUNED | Engineered for Performance. Calibrated for Reliability.www.migtuned.com
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