Hey everyone. Knew to the go fast car scene. Rode motorcycles for a few years then my son came along and I decided to ditch that life for now and get a fun car so I bought a 2018 STI. Trying to learn as much as I can here. Currently stock running the stage 1 tune from Cobb. Plan on doing an intake and maybe some exhaust work and then looking to get it pro tuned. Suggestions on who to look into and what else I can do to make this car reliable would be great. Oh also I have a mishimoto catch can installed and eventually plan on getting the iag aos to replace that.
Subie newbie from MD
- Thread starter Ace
- Start date
Welcome! You've come to the right place. There is lots of information here and a ton of good people that will point you in the right direction.
A catch can or AOS is a great modification for reliability's sake, though they are not quite as necessary on a stock engine as they are on a built engine.
Everyone likes to open up the intake for the increased turbo spooling and bypass valve noises. Most off the shelf tunes (such as Cobb) are not optimized for an aftermarket intake and changing the intake often has a greater than expected effect on engine health due to changes in the way the MAF is reading. Worst case scenario, an intake causes you to run lean, knock and have catastrophic piston damage. Plus, the stock intake is very capable up to around 400whp. Either way, if you must change the intake, you should definitely get a protune.
If you just want the increased turbo sounds, I would suggest removing the intake silencer. This will not effect the tune.
The "Stage II" level of modifications is probably the most common/popular with these cars. At a basic level, it requires a new downpipe and a tune. There are lots of different opinions on what downpipe (or full turboback, that is a downpipe + catback) is best. But first we have to discuss what your lifetime plans are for this car.
If you don't plan on much beyond ~325whp, then a Stage II level is fine. If you foresee wanting more in the future, then I generally recommend a turboback exhaust, upgraded fuel pump, larger injectors, turbo inlet, intake and protune. This can all get expensive really fast, so make sure you have done your homework and drawn up a plan. No one likes to spend extra money to re-do something you modified previously.
That should get you started. Do some thinking and get back to us.
Once again, welcome to IGOTASTI.com!
A catch can or AOS is a great modification for reliability's sake, though they are not quite as necessary on a stock engine as they are on a built engine.
Everyone likes to open up the intake for the increased turbo spooling and bypass valve noises. Most off the shelf tunes (such as Cobb) are not optimized for an aftermarket intake and changing the intake often has a greater than expected effect on engine health due to changes in the way the MAF is reading. Worst case scenario, an intake causes you to run lean, knock and have catastrophic piston damage. Plus, the stock intake is very capable up to around 400whp. Either way, if you must change the intake, you should definitely get a protune.
If you just want the increased turbo sounds, I would suggest removing the intake silencer. This will not effect the tune.
The "Stage II" level of modifications is probably the most common/popular with these cars. At a basic level, it requires a new downpipe and a tune. There are lots of different opinions on what downpipe (or full turboback, that is a downpipe + catback) is best. But first we have to discuss what your lifetime plans are for this car.
If you don't plan on much beyond ~325whp, then a Stage II level is fine. If you foresee wanting more in the future, then I generally recommend a turboback exhaust, upgraded fuel pump, larger injectors, turbo inlet, intake and protune. This can all get expensive really fast, so make sure you have done your homework and drawn up a plan. No one likes to spend extra money to re-do something you modified previously.
That should get you started. Do some thinking and get back to us.
Once again, welcome to IGOTASTI.com!
Grinder34
Track Monkey
Mirroring the above,
Research! And then post, then research some more!
If you know your ultimate goals, you can do some incremental things along the way, but it always stinks to have to replace something you already bought that isnt up to the task later (fuel pump, injectors, etc...).
I'd also strongly recommend looking into a few handling tweaks such as swaybars and endlinks.
And then dont forget about looks! Front lips, difusers, tints, lowering (although definitely do research on this first, or ask questions...or both), new/wider rims, etc...
Have fun with it!
Research! And then post, then research some more!
If you know your ultimate goals, you can do some incremental things along the way, but it always stinks to have to replace something you already bought that isnt up to the task later (fuel pump, injectors, etc...).
I'd also strongly recommend looking into a few handling tweaks such as swaybars and endlinks.
And then dont forget about looks! Front lips, difusers, tints, lowering (although definitely do research on this first, or ask questions...or both), new/wider rims, etc...
Have fun with it!
^ I completely agree. Some of my favorite mods are swaybars, endlinks, swaybar mounts and urethane bushings for all of the above.
Alin
Diehard Car Enthusiast!
Welcome to IGOTASTI!! You're going to absolutely love it here!! Post some pictures of the ride!!
What other cars have you had in the past? How does the STi compare to them? Is there anything you don't like about it? What do you love about it?
What motorcycles have you had? Do you have any pictures of them? (My last one was an '07 CBR 600RR.)
The very first thing that you should've done was read the owner's manual! If you already read it, read it again! The second thing you should be doing, whenever you're not driving, is reading and researching! (Both of these are completely and truly free, and you ONLY have positives to gain from them!) The best bang for the buck is what we call the "driver mod." You need to get accustomed being behind the wheel and learn how the car behaves. You will be the most important aspect of how your car performs!
Next, and this is extremely important, ask ANY AND ALL questions you may have! It's entirely beneficial in your favor to ask before you act! Learning from other people's mistakes is free and a crucial impact on your journey! This is the only Subie forum that I'm on anymore and there is a major reason for that: there is no misinformation on here! If we truly don't know the answer to something, we will point you in the right direction where someone else can help who actually knows!
I also recommend you start a member's journal. You can brainstorm what you want to do before you actually do it and we'll help you along the way so you avoid as many mistakes as possible.
Also, to add to what [MENTION=652]Grinder34[/MENTION] and [MENTION=662]Batmobile_Engage[/MENTION] have said, don't overlook tires! They are the only thing between you and the road! Save the money you would spend (or rather essentially waste) on an intake and put it towards something else that will have a bigger and more meaningful impact.
What other cars have you had in the past? How does the STi compare to them? Is there anything you don't like about it? What do you love about it?
What motorcycles have you had? Do you have any pictures of them? (My last one was an '07 CBR 600RR.)
The very first thing that you should've done was read the owner's manual! If you already read it, read it again! The second thing you should be doing, whenever you're not driving, is reading and researching! (Both of these are completely and truly free, and you ONLY have positives to gain from them!) The best bang for the buck is what we call the "driver mod." You need to get accustomed being behind the wheel and learn how the car behaves. You will be the most important aspect of how your car performs!
Next, and this is extremely important, ask ANY AND ALL questions you may have! It's entirely beneficial in your favor to ask before you act! Learning from other people's mistakes is free and a crucial impact on your journey! This is the only Subie forum that I'm on anymore and there is a major reason for that: there is no misinformation on here! If we truly don't know the answer to something, we will point you in the right direction where someone else can help who actually knows!
I also recommend you start a member's journal. You can brainstorm what you want to do before you actually do it and we'll help you along the way so you avoid as many mistakes as possible.
Also, to add to what [MENTION=652]Grinder34[/MENTION] and [MENTION=662]Batmobile_Engage[/MENTION] have said, don't overlook tires! They are the only thing between you and the road! Save the money you would spend (or rather essentially waste) on an intake and put it towards something else that will have a bigger and more meaningful impact.
Thanks everyone for the advice! What are the best parameters to monitor on the AP and what are normal values I should be seeing on stage 1 Cobb tune. I?ve been trying to search around on forums for the answers but a lot of threads seem to jump around a lot and it?s hard to follow what is actually being said.
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Alin
Diehard Car Enthusiast!
I think the 2015+ models all have the V3 AP, so you have the 6 slot screen.
I would monitor:
-Short Term Fuel Trims
-Long Term Fuel Trims
-Feedback Knock
-Fine Knock Learning
-Air Intake Temperature
-Dynamic Advanced Multiplier
(If I recall correctly, the AP always measures the AFR (air to fuel ratio) correctly no matter what. This is the reason why a dedicated wideband/AFR sensor/gauge is required for tuning and also to monitor the correct ratio.)
I'm sure someone else will correct me if needed and also chime in. :tup:
I would monitor:
-Short Term Fuel Trims
-Long Term Fuel Trims
-Feedback Knock
-Fine Knock Learning
-Air Intake Temperature
-Dynamic Advanced Multiplier
(If I recall correctly, the AP always measures the AFR (air to fuel ratio) correctly no matter what. This is the reason why a dedicated wideband/AFR sensor/gauge is required for tuning and also to monitor the correct ratio.)
I'm sure someone else will correct me if needed and also chime in. :tup:
Eagleye
Tinkerer
This is why we encourage questions here. Who cares if it has been asked before. If we have a really good master thread on something we will point you toward it, otherwise, ask away.
With that out of the way, welcome! I echo what others have said so far. Skip the intake for now unless you reallllly want more whooooshy sounds. If that is the case go with the Cobb intake that way you can run the stage 1 + tune from them until you get protuned later. Yes every car is different and therefore benefit from individual tuning, but Cobb does extensive testing for their maps and if you follow their mods specifically, you can run their OTS maps. Sure you will make less power than you could with a protune, but you will be safe until getting a more specialized tune.
As others said, look at the suspension, exterior bits, wheels/tires, shifter, etc. Some of those mods are significantly cheaper than performance mods while making the car substantially more fun to drive. I'm personally Cobb stage 1 on my 15 STi with Whiteline and Super Pro suspension, short shifter, Enkei wheels & summer tires, muffler deletes, and a few exterior parts. It has all added up to a car that I love driving, hearing, and staring at as I walk away. Just the sounds and looks make me smile with this car. I had a built 06, it was fun as hell. But honestly this car has been more enjoyable so far.
What kind of information is the fuel trims giving me and what should I be looking for?
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I?ve had a few cars in the past 2009 charger, 2009 VW rabbit, 1986 firebird transam, 2016 Jetta, 1991 wrangler.
As far as bike do I?ve had a 2006 R6 and 2016 FZ09
I love the car as a whole fun to drive decent gas mileage. I just wish I could actually hear the turbo and exhaust was a bit louder. Oh and the stock radio sucks wish the 2018 had apple play. Also rev hang on stock tune was terrible.
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I monitor different things depending on what I'm doing but then again I also tune my own car with Cobb AccessTuner.
As far as fuel trims the information it is giving you is the percentage of correction to obtain a stoichiometric air:fuel ratio based on O2 sensor feedback in comparison to the calculated value it expected to use.
What's the expected value? Final Injector Pulse Width.
Final IPW (Injector Pulse Width) (microseconds) = Final Fuel Multiplier ? Fuel Injector Scale ? Load ? (A/F Corr. #1 + A/F Learn #1 ) ? Per Cylinder IPW Comp. ? Small IPW Comp.
Final Fuel Multiplier = 1 lamda in closed loop operation or is an interpolated value looked up in the Primary Open Loop Fuel Table. (You can monitor "Closed Loop Switch" to see when it is in closed or open loop...closed loop mean it corrects fuel based on sensor feedback, open loop is solely calculated and it doesn't matter how much it deviates from the value you want to obtain as no correction is applied)
Fuel Injector Scale = IPW (in microseconds) for stoichiometric fueling per gram of calculated load. This is a single value and comes from a table, it would basically only be changed if you change injectors or fuel type.
Load (in grams/revolution) = Calculated load and can be monitored via access port. It is calculated, and equals Final Mass Air Flow (MAF Voltage converted to interpolated value air value in grams per second + load compensation. Load compensation = % looked up in 2 tables based whether TGV's are open or closed and uses Manifold Absolute pressure and RPM as the Axis) ? RPM ? 60 (To convert RPM to RPS..rev per second)
Per Cylinder IPW Comp. = Small correction from lookup table to fix injector flow difference or fuel flow characteristics, harmonics, etc.
Small IPW Comp. = From lookup table and is a flow correction provided by injector manufacturer generally to correct injector not linear behavior when IPW is small (generally under 3 milliseconds)
A/F Correction = Short term or immediate correction, ECU wants this to be 0
A/F Learn = Long Term Correction and are based on the average A/F Correction to an extent and there are a few different areas of load these apply. You can also monitor these values on the AccessPort under A/F Learn A, A/F Learn B, etc.
What you would be looking for is a large value or percentage as that can be an indicator of a problem ie bad gas, sensor, vacuum leak, boost leak, PCV oil blow by, etc.
Feedback Knock is immediate correction if knock is detected / heard (when certain conditions are met) and is equivalent to A/F correction as the ECU wants this to stay 0
Fine Knock Learn is long term correction if Feedback knock is continually detected within certain table value based on calculated load and rpm to preemptively retard timing to prevent Feedback Knock from occurring and then slowly adds timing back over time testing to see if it is safe again in case of bad gas for example.
Air Intake temp is measured at the MAF sensor and it will indicate air flow problems for example if it is 40deg out but it is reading 140 while cruising there might be a problem or something you might want to upgrade to correct or explain why the car feels sluggish if you were to mash the gas, though it can get higher after idling on a hot day for a while, etc. In general I find it mostly useless, much more useful if placed after intercooler which is where mine is and not recommended to do so unless you change to speed density tune like my car is setup to be on, reason being is it isn't there to correct for the air temp as MAF measures air mass directly, the point is as a correction to the MAF sensors calibration due to temperature.
Dynamic Advance Multiplier - It should always be at 1 and is used to calculate additional timing as specified in the dynamic advance (2 tables depending if TGV's are open or closed) table that is added to the Primary Ignition Value. Dynamic Advance Timing (4 tables TGV open, normal and AVCS Warm-Up, TGV Closed, normal and TGV Warm-Up) and is calculated as such dynamic advance table value * DAM (Dynamic Advance Multiplier). Generally regarded as bad if it drops below 1, I rarely if ever monitor this.
Last edited:
Grinder34
Track Monkey
Wanted a fun car and it needed to be 4 doors. dad mobile status!
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