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"Supreme Subaphile Extraordinairre"
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Discussion Starter #1 (Edited by Moderator)
I've noticed quite a few questions regading the necessity of an Engine Management system (EM), based upon certain upgrades. Rather than searching in 27 different threads to find out, I'm going to try to create an all-inclusive thread.

With that, I'm going to (hopefully) clear up any misconceptions...

1) A catback exhaust (CBE) does almost nothing for your car except make it sound cooler.... you do not need an EM

2) An aftermarket intake "can" cause your car to run lean (too much air, not enough fuel)... so yes, you should be tuned. The exception would be an SPT intake, as Subaru claims they are safe to run on the stock engine/ECU. However, I would get tuned anyway.

3) A Turboback exhaust (TBE) includes a bellmouth Downpipe (DP). The DP allows your turbo to boost higher, and produce more power. With that, if your ECU is not telling your injectors to supply more fuel, and adjust the timing, to compensate for the added boost.... then once again, lean conditions and boost spiking occur. Yes, you need an EM.... period

*** Note, if you have a downpipe with no EM, don't complain when you blow something up.

4) An aftermarket top-mount intercooler (TMIC) with do very little for your performance... it will however, give you greater protection from heatsoak. No, you do not need a tune.

5) An aftermarket front-mount intercooler (FMIC) gives you added protection from heatsoak, but because the forced air has so much further to travel, it has been known to cause a bit of added turbo lag. The general rule of conscensus is that you don't need one unless you are over 350 whp. If you choose to use one anyway, then yes, you should be tuned.

5) a BOV will do NOTHING for you.. at all. In fact, if you don't get a recirculating BOV, you'll probably end up hurting your performance. Either way, you do not need a tune to install one.

6) On pre-06 WRXs, an aftermarket catless uppipe will give you added performance, and in many folks' eyes, is necessary preventative maintenance to ensure the catalytic converter doesn't get sucked up into the turbo. It will allow your turbo to spool up quicker, but generally will not cause lean conditions or boost spiking. For an uppipe only, no, you do not need a tune.

7) lightweight pulleys are the equivilent of removing weight from your car, you do not need a tune.

8) Turbo upgrades..... whatever it is, yes, you need to be tuned.... I can't tell you how many stock WRXs I've seen that bolt on a VF39, an 18G or a 16G turbo and drive off without doing anything else...... then complain about why their car doesn't run right.

Please... if you have anything else to add.... please do. Just seems like we get a lot of the same questions over and over again.... trying to help here and steer people in the right direction.

An EM should be the VERY FIRST item you buy for your car.... and I think just about everyone will agree with me on that one. Yes, they are expensive... but you only have to buy it once, it's infinately upgradeable, and most importantly, it's SAFE.

Hope this helps.
 

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If you edit the first paragraph to be a bit more user friendly and less abrasive, I think this would be worthy of being stickied...

Things I would include

Exhaust manifold/header: No, you do not need EM but you will realize better performance gains if you are custom tuned to account for this mod

Turbo Port/Polish:
No, not necessary. This, much like a catless uppipe, will simply increase the efficiency of the system, not necessarily a huge increase in performance. While this mod will certainly change the dynamics of your turbo system, it will not be outside the safe control of the stock ECU.

TGV deletes:
Yes, you need EM to delete the inevitable CEL that will result from deleting your TGV's and you need some way to tune for the increased airflow across the RPM range

Boost controller, manual or otherwise:
Yes, kind of. Any time you raise boost more than 2 psi on an otherwise mostly stock car, you should add engine management. The argument could be made that 2 psi increase or less is not going to do a whole lot to hurt you. That being said, you should not be increasing boost without aftermarket exhaust, and you should not have aftermarket exhaust without EM, therefore by the transitive property, you should not have a boost controller without EM.

Turbo inlet hose/any pressurized post-turbo piping or hoses: Absolutely not, these do very little to change the performance of the car and really only help making the turbo parts easier to remove/install.

Walbro Fuel pump: No, your fuel pressure regulator prevents a higher volume pump from overpowering the injectors and thereby altering fueling. If you change your fuel pressure regulator in any way, you will need to account for that change via tuning, but an otherwise drop-in Walbro replacement does not need EM.

Larger than stock injectors: Yes, you definitely need to tune for larger than stock injectors. A car will start with over-sized injectors and will likely drive "okay" but will not run properly and will be way too rich to drive aggressively.

Fuel Rails: No. See discussion of Walbro pump. More potential flow to the injectors does not necessarily mean your injector will inject more fuel unless you tell it to. Very minor tweaks may be needed if you do this mod, so minor you would probably never notice them and they would do no damage.


AccessPort vs OpenECU/RomRaider/Enginuity/Tactrix: Yes, AP is the easiest and most reliable way to modify your stock computer. The "DIY reflashes" are also very good and much cheaper. If you think you are going to need engine management, do not immediately discredit the DIY methods. With proper education, patience, and a careful and inquisitive mind, flashing a stage 2 car yourself is reasonably safe and easy to do. Making the choice to do it yourself is basically a measure of how confident you are that you can follow carefully outlined procedures and use good common sense to troubleshoot a problem if something goes wrong. The Cobb AP is basically idiot proof, but you have to pay for this feature, as well as their customer support.
 

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"Supreme Subaphile Extraordinairre"
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Discussion Starter #3
If you edit the first paragraph to be a bit more user friendly and less abrasive, I think this would be worthy of being stickied...
You're right... didn't mean to come across like that at all.

I changed it... I think it sounds more PC :)
 

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Admin - Scooby Hooligan
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how about i put it in the Electronic Engine Management thread

plus i want to delete the AP port , its definitely not the most reliable
 

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how about i put it in the Electronic Engine Management thread
That works, would it be too much to ask for both since they're inter-related?

plus i want to delete the AP port , its definitely not the most reliable
I guess it's a matter of opinion, but it certainly does what it's intended to and has a solid track record. What would be your pick for "most reliable?"
 

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Geriatric Ginger Mod
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I'm actually working on a thread sticky/addition/whatever, offline, that will be posted up soon.
But yeah, I concur on the merge.
 

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sticky this biotch...ill be reading this often...of course when i do get an STI
 

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4) An aftermarket top-mount intercooler (TMIC) with do very little for your performance... it will however, give you greater protection from heatsoak. No, you do not need a tune.
Okay.You replace the stock tube and fin TMIC with a bar and plate TMIC of close to similar size.Now you have gone from a 2psi pressure drop to a .5 psi pressure drop.That means you are now overboosting by 1.5psi or maybe more depending on how the stock temp compensation can correct plus probabaly over running the stock load mapping.A tune would be a good idea for the same reasons as a TBE except now the pressure differential is on the intake side.Plus tuning for a more efficient TMIC allows you to run more boost and more timing advance with leaner AFR's.Also you have 2 #5's:)
 

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Moved over to EM for the time being as it seems more "fitting" in that forum.


Good info in here.
 

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I'll throw one out there, what with fuel prices being what they are..

Higher Than Recommended Octane Fuel: Don't waste your money on higher than recommended octane fuel, as your car cannot take advantage of it unless you are tuned for it. :)
 

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You're right... didn't mean to come across like that at all.

I changed it... I think it sounds more PC :)
lol it was kinda "mean" but screw that......


people need to know whats what. i tell people straight up what they should/should not get, do or buy.

lol. i say Cobb AP is hands down the best bang for the buck. IMHO
 

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Geriatric Ginger Mod
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telling them what they should/shouldn't buy, is opinionated.

your and my opinions differ. you enjoy Cobb, and I prefer RomRaider.

90$ vs. 600$.

$600 buys me EMS and 510$ of other go-fast goodies.

Again, though, opinionated.
 

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"Supreme Subaphile Extraordinairre"
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Discussion Starter #16
An Engine Management system is a crucial upgrade, particularly for the mods listed in this thread.

As far as "which" EM system is best, that is entirely personal opinion. I'm sure the low-cost EM (tatrix, etc) are just as good as the Cobb AP, provided you KNOW WHAT YOU ARE DOING. I've heard horror stories of people opting to buy "self-tuning" software that have no idea what they are doing, and end up blowing something up.

I'm FAR from a computer expert, and quite frankly, when I start thinking about the science of air/fuel ratios, etc, I get frustrated.

I don't think anyone can argue that the COBB AP is by far the most "user friendly", particularly for newbs or computer idiots like myself. I also don't think anyone can argue that Cobb has outstanding customer service.

I'm quite certain that MANY will argue with what cobb charges for the Accessport though :)

Hopefully, the buyer is well educated on the differences, weighs the pros and cons of each, and smart enough to know that he/she needs some kind of EM before bolting on that brand new GT40--LOL :)
 

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Turbo inlet hose/any pressurized post-turbo piping or hoses: Absolutely not, these do very little to change the performance of the car and really only help making the turbo parts easier to remove/install.
I highly disagree.
If you don't get tuned for an aftermarket turbo inlet, you will experience overboosting, fuel cut & a CEL. Don't ask me how I know.
 

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An Engine Management system is a crucial upgrade, particularly for the mods listed in this thread.

As far as "which" EM system is best, that is entirely personal opinion. I'm sure the low-cost EM (tatrix, etc) are just as good as the Cobb AP, provided you KNOW WHAT YOU ARE DOING. I've heard horror stories of people opting to buy "self-tuning" software that have no idea what they are doing, and end up blowing something up.

I'm FAR from a computer expert, and quite frankly, when I start thinking about the science of air/fuel ratios, etc, I get frustrated.

I don't think anyone can argue that the COBB AP is by far the most "user friendly", particularly for newbs or computer idiots like myself. I also don't think anyone can argue that Cobb has outstanding customer service.

I'm quite certain that MANY will argue with what cobb charges for the Accessport though :)

Hopefully, the buyer is well educated on the differences, weighs the pros and cons of each, and smart enough to know that he/she needs some kind of EM before bolting on that brand new GT40--LOL :)
cant stress that fact out enough. i agree completely with u :).

it should also be noted that a skilled tuner (knowledgeable in EFI) should be the only one to get the cheaper, OpenEcu software and go at it. i gave my old tuner/mechanic a crack at reflashing my car, and my car didnt like it. throwing CEL's, fuel cut, etc. i turned it stock, bought a Cobb AP and never looked back. nothing against the programming tho, its just that the "tuner" i went to was a dumbass and put a map on my car that was a lil more aggressive the map on his own suby (an sti turbo swapped, sti injector swapped baja). deff left an impression on me that certain people shouldnt be allowed to do certain sh_t on cars lol. sometimes the thought crosses my mind of selling my AP and going to another veteran tuner down near philly and letting him tune my car with OpenEcu (Turbotek Tuning for those of who know of them). BUT ............i wouldnt be able to switch maps if i chose to (Economy, Valet mode, stock ecu, etc.). so the decision is a tough one. a really tough one.
 

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cant stress that fact out enough. i agree completely with u :).

it should also be noted that a skilled tuner (knowledgeable in EFI) should be the only one to get the cheaper, OpenEcu software and go at it. i gave my old tuner/mechanic a crack at reflashing my car, and my car didnt like it. throwing CEL's, fuel cut, etc. i turned it stock, bought a Cobb AP and never looked back. nothing against the programming tho, its just that the "tuner" i went to was a dumbass and put a map on my car that was a lil more aggressive the map on his own suby (an sti turbo swapped, sti injector swapped baja). deff left an impression on me that certain people shouldnt be allowed to do certain sh_t on cars lol. sometimes the thought crosses my mind of selling my AP and going to another veteran tuner down near philly and letting him tune my car with OpenEcu
You do realize that you can buy premade maps (just like Cobb's OTS maps or better) or custom made maps that can just be flashed to your car using Opensource software.Just because you go the Opensource route,it doesn't mean you are stuck having to tune your own car or pay for custom dyno tuning.
 

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5) a BOV will do NOTHING for you.. at all. In fact, if you don't get a recirculating BOV, you'll probably end up hurting your performance. Either way, you do not need a tune to install one.
I was under the influence that a BOV was efficient with high boost levels (20psi+).
 
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