Ask a tuner...

[P3Auto]

Originally Posted by Marlons101

why is my cel on for misfire but no codes show? why does it flassh atl low rpms but not at high rpms?

I have changed plugs, fuel filter, checked lines, cleaned MAF, ....what else should i do? car runs normal just this flashing cel? my gas mileage is **** so does that point to my front O2 sensor?

Misfire codes are temp codes but they are stored. Depending on how your reading them your reader may only be looking at active codes. Basically a misfire code will clear itself after time and become a stored code in history.Misfires can be detected due to an actual misfire you cannot feel or falsely for many reasons. Do you have any lightened pulleys, flywheel? Crank angle sensor could be going bad. Coil pack, injector issue, etc. Timing problem. Need a little more info.

Again were getting into diags not tune specific from what I can tell.

The car is more likely to misfire or detect misfire in lower rpms because the load is higher on the motor and the sensitivity of the detection circuit is better. Some code will actually not even try to detect a misfire at higher rpms. Not sure on yours would have to research but its not really important at this stage.

As for the O2 sensor(front one anyway) the car uses this to fine tune closed loop mode. So when your idle or just cruising the ECU will read the from the front wideband and adjust the trims to match 14.7:1 AFR. Usually when they go bad you get a check engine light, or surging while cruising, hunting idle, smells rich, black smoke, etc. It could be possible that yours has skewed somehow to give off readings making your car richen up the mix thinking its hitting 14.7:1. I would say this is very unlikely but a very rich idle would cause misfires. You could figure it out by logging or using learningview.exe. The learned trims will be positive numbers over 6-8%.

I seem to remember you had the misfire issues on your old motor as well. I would suspect a part you swaped.

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[P3Auto]

So it was brought to my attention that some Cobb tunes for 90-91 octane run the injectors at 100% . I just got done doing some checking on this and also looking at some logs from when I tried one of these tunes in one of my cars.

It does seem in fact that specifically Stage 2 90-91 octane pre-2009 STI tunes do run the injectors to 99% or more. So is this really bad you may wonder, well let me walk you through the steps of what happens when there is trouble.

So when the car is completly happy your running 18lbs or so of boost and maxxing the injectors out at or close to redline. In the event of severe enough knock or very cold conditions the car will switch to different fuel maps or add fuel. Seems like a no brainer right? You must need bigger injectors! Well let see...

A big piece of Subarus "fail safe" technology is based on something called IAM (ignition adavance multiplier) or the same DAM (dynamic advance multiplier). On an STI when all is happy and there is no knock this number is at 1.0 got it? 1.0 is best and 0.1 is worst.

Now when there is a knock event for any reason if its bad enough the car will drop the IAM down a certain amount depending on various factors. So lets just say the IAM has dropped, here is a chart for what happens on an 05 STI with Cobb Stage 2 90-91 octane:

1.00 Very happy car.
0.75 Global timing reduced.
0.50 Global timing reduced.
0.35 Switch to failsafe fuel maps, Global timing reduced
0.20 Boost control shut down (min boost), Global timing reduced

So when we switch to failsafe maps we see the car wants to add in some fuel with a failsafe map, it adds as much as 5% more fuel for an STI. But here is the catch.

The Cobb tune doesn't max out injectors until close to redline. The failsafe tables only add fuel in the peak tq regions and look the same as the normal fuel maps towards redline. There is JUST enough room to add the fuel needed.

The other part is the fuel tables are calling for 10.6:1 at redline, the reality we see on the wideband is close to 10:1 which is VERY rich at redline. You actually don't need near that amount of fuel past peak TQ. Peak TQ ranges is where the knock tends to be not at peak HP range. So leaning out at redline as long as it doesn't exceed 11.5:1 *should* be ok.

More catch, if the knock is bad enough and your using the factory boost control then the car also pulls the boost out which means......Yep less fuel needed.



So if I have completly confused you now the original question was does my STI need bigger injectors to be safe?

Yes and no:

No -- If you run stock boost control, don't go below sea level and redline it, will never run over 18.5PSI, and feel your car will never blow a hose or loose boost control.

Yes -- If you run after market boost control, and if you want to be absolutely sure to be safe. The possibility for spikes in air flow due to boost control failure or other condition are real!

All it takes is one good pull in a lean condition and your piston is done in most cases due to severe knock. Some injector overhead would be nice to have but won't solve all problems, at least it would be one thing less to worry about.

[Phaedron]

Heres a question for you. What would be two of the most beneficial books to someone wanting to learn about tuning on modern engines, but lacking much of a background on the subject? Where is a good place to start?

[rack]

Originally Posted by P3Auto

So it was brought to my attention that some Cobb tunes for 90-91 octane run the injectors at 100% .....

Nice write up, thank you =)

[P3Auto]

Originally Posted by Phaedron

Heres a question for you. What would be two of the most beneficial books to someone wanting to learn about tuning on modern engines, but lacking much of a background on the subject? Where is a good place to start?

Good question...

First read should be:

http://www.amazon.com/Engine-Management-Advanced-Greg-Banish/dp/1932494421/ref=sr_1_2?ie=UTF8&s=books&qid=1269915658&sr=8-2
This book even has Subaru WRX/STI pics in it with some talk about them.

I think you have an 07 STI. If you already have a tune you should take a look at it and start to examine the tables one at a time and learn what they all do. If you have a Cobb AP2 you can download free software from Cobb to actually view and change your own tune. If you want to use OpenECU thats a great choice as well to view and edit your tune.

The forums have great information if you can pick over the noise and they also go over the tools needed to start going.

If you can get a handle on the fundamentals and how the engine works then understand timing and fuel you can start to tune anything.

Every ECU has its own specilized logic that you have to learn but the more you do it the easier it is to learn new or different ECUs.

The other part of course is understanding the limits of what your tuning and this part is where it gets tricky. Lots of reading and research must be done on the specific model of car to understand things like drivetrain weakness, common points of failure, fuel and timing limits, etc.

The bad part about this for any tuner is doing something new. We have to learn by trial and error of the weakness of the systems if they are not already known. Usually someone else has broken it first and wrote about it some where!

Finally you have to be able to identify existing issues not related to the tune. This is the biggest headache for any tuner.

Its common for some one to call me and say some thing like "My car isn't hitting boost any more, I need it to be retuned.", or "My car has a rough idle and feels slower, I need you to retune it.". 9 times out of 10 there is a mechanical issue like a hose is loose, internals are failing, the list goes on and on. Problems like that should not be tuned out but rather identified and fixed prior to a tune.

An easy example would be a person with a stock tune that claims issues and wants them fixed via a tune. Bad plan. You should never tune a car that you can't verify is properly working from the start. This all requires knowlege of whats normal and whats not. Something I have to repeat to customers all the time is that a tune doesn't change over time, the car and the enviroment do.

I personally will turn away work if the car does not meet my standards or is a "hack job". I would offer to fix mechanical issues but not band-aid them. I simply won't participate in blowing their car up any faster.

I have started to produce some videos for tuning Subarus but have failed in terms of time to get them done. I think others have some stuff out there if you search youtube.

[Brando5185]

Asking my tuner :-)

What type Big MAF should I get? Which do you think would work best with my set-up or you are more experienced dealing with?

[P3Auto]

Originally Posted by Brando5185

Asking my tuner :-)

What type Big MAF should I get? Which do you think would work best with my set-up or you are more experienced dealing with?

Perrin BigMAF with a true cold air intake extension or box that pulls air from the fender. I have tuned a few of these and have the MAF transforms basically done.

There are some small downfalls to a bigger MAF but nothing major, if you don't need it don't do it though. If your planning on moving that much more air your going to need a bigger intercooler if you don't already have one.

Sounds like your on the road to a built motor eventually, welcome to the rabbit hole. As soon as you start pushing those stock internals (pistons mainly) its just a matter of time.

I'm going to be running specials on built motors this season with a core or your own block.

[Brando5185]

See below....

[Brando5185]

Originally Posted by P3Auto

Perrin BigMAF with a true cold air intake extension or box that pulls air from the fender. I have tuned a few of these and have the MAF transforms basically done.

There are some small downfalls to a bigger MAF but nothing major, if you don't need it don't do it though. If your planning on moving that much more air your going to need a bigger intercooler if you don't already have one.

Sounds like your on the road to a built motor eventually, welcome to the rabbit hole. As soon as you start pushing those stock internals (pistons mainly) its just a matter of time.

I'm going to be running specials on built motors this season with a core or your own block.

We were already maxing the stock MAF with 19.8 PSI. Going to run meth and possibly a bit more boost this summer. I am running the Perrin FMIC now which I think should be big enough. Deploying in Sep and should be getting my block built while I am away.

[Nomadgene]

Originally Posted by Phaedron

Heres a question for you. What would be two of the most beneficial books to someone wanting to learn about tuning on modern engines, but lacking much of a background on the subject? Where is a good place to start?

This is what I have used. http://store.autospeed.com/Items/156...dition)%20Book

Probably a bit dated now but it really helps promote the idea of keeping the natural balance of the car. Of course, it is specific to the WRX/STI .

[Phaedron]

Thank you for the advice and the convenient links. I am currently on a AP V2 but am looking at converting over to open source. Haven't had much of a chance to play with the AP yet but it is pretty high up on my list now. Just want to start to get used to data logging and what not. I don't know near enough and would not be comfortable even thinking about messing with the actual tune just yet.

Looks like I'll have a couple of books to kill my flight time with now.

[jimspliff]

P1448 Fuel Tank Sensor Control Valve Range/Performance. Thats the code I got when I took it to Schuck's/O'Reillys I asked you about it before and I think you said it has to do with the evap system and/or emissions system. What could I do to fix that?

[P3Auto]

Originally Posted by jimspliff

P1448 Fuel Tank Sensor Control Valve Range/Performance. Thats the code I got when I took it to Schuck's/O'Reillys I asked you about it before and I think you said it has to do with the evap system and/or emissions system. What could I do to fix that?

This would be something I would have to take a look at on the car. We can make an appointment to look at it.

Could be a lot of things that would lead up to the code. You could also open a thread or search the forums to see if others have had this issue. I just couldn't really say off the top of my head.

[rivman05]

Do you touch emanages? I got a blue, that I just need my maf and injectors scaled on. Im not too confident I can do it, and I dont have a pc anymore...

[nathan.d.kim]

Seth,

Glad to have found this thread. =P Thanks for volunteering to help others.

I have a 2007 STI with the following engine upgrades:
- Cobb downpipe and catted TBE
- Custom tuning on a Mustang Dyno using Cobb AP2
- Rallispec short block with stock-sized forged Wiseco pistons (approx. 2k miles)
- intake snorkel delete

Minimal modifications, really, besides the new shortblock. I had a cracked ringland at 46k miles and replaced the SB rather than rebuilding the old block. It has been great since.

I never considered getting a CAI because I knew it was not that much bang for the buck. I was also advised that the stock STI intake is very similar to a CAI in design, especially with the silencer ("snorkel") delete. It draws air from the front grill, takes it through the fender, and feeds it through the MAF.

This past weekend, I had a chance to ride in my friend's '10 STI with an AEM CAI - very nice looking with the wrinkled red coating. Anyway, I don't know if the CAI made it run THAT much faster than stock, but... as stupid as it sounds... it sure sounded great. I'm just not sure if the performance increase is really great enough to put down some more funds.

My questions:
(1) What kinds of gains have you seen with just a CAI added to a DP+TBE setup?
(2) Do YOU think it's worth the money to do just the CAI with a follow-up tune (total price of $480)?
(3) If not, what other relatively low-cost mods do you recommend to do at the same time as the CAI in order to maximize the cost of a follow-up tuning session?
(4) If not going to a CAI at all, what other mods do you think are better at this point based on the mods I've listed above?

Thanks in advance!

[P3Auto]

Originally Posted by rivman05

Do you touch emanages? I got a blue, that I just need my maf and injectors scaled on. Im not too confident I can do it, and I dont have a pc anymore...

Yes but rarely. I could tune it. The end result is the same, finding the software again now that could be fun...We need to do injectors first then MAF or MAF then injectors. Doing them both at the same time is much more work.

[rivman05]

Ok, either or it doesnt matter a whole lot to me. I just need to get it to the point of being snappy again...doubling injector size, and a bigger maf dont help gettin around.

[P3Auto]

Originally Posted by nathan.d.kim

Seth,

Glad to have found this thread. =P Thanks for volunteering to help others.

I have a 2007 STI with the following engine upgrades:
- Cobb downpipe and catted TBE
- Custom tuning on a Mustang Dyno using Cobb AP2
- Rallispec short block with stock-sized forged Wiseco pistons (approx. 2k miles)
- intake snorkel delete

Minimal modifications, really, besides the new shortblock. I had a cracked ringland at 46k miles and replaced the SB rather than rebuilding the old block. It has been great since.

I never considered getting a CAI because I knew it was not that much bang for the buck. I was also advised that the stock STI intake is very similar to a CAI in design, especially with the silencer ("snorkel") delete. It draws air from the front grill, takes it through the fender, and feeds it through the MAF.

This past weekend, I had a chance to ride in my friend's '10 STI with an AEM CAI - very nice looking with the wrinkled red coating. Anyway, I don't know if the CAI made it run THAT much faster than stock, but... as stupid as it sounds... it sure sounded great. I'm just not sure if the performance increase is really great enough to put down some more funds.

My questions:
(1) What kinds of gains have you seen with just a CAI added to a DP+TBE setup?
(2) Do YOU think it's worth the money to do just the CAI with a follow-up tune (total price of $480)?
(3) If not, what other relatively low-cost mods do you recommend to do at the same time as the CAI in order to maximize the cost of a follow-up tuning session?
(4) If not going to a CAI at all, what other mods do you think are better at this point based on the mods I've listed above?

Thanks in advance!

Answers are really car and application specific and will vary...

1. None if the existing intake is flowing properly which it would be with the stock turbo. The stock intake is a CAI and I actually find gains by using it instead of the short rams. The idea is to not pull air from under the hood where its hot. The stock STI air box with a K&N panel filter is good for over 300WHP.

2. No. No tune would be required unless you change the MAF tube size or your new intake creates some sort of turbulence or flat spots.

3. Water injection with a safety. Best bang for you buck at under $500 you can run race tunes all day long with just -40 washer fluid. Also steam cleans valves, plugs, pistons. This prevents carbon build up. Lowers EGT's. Very low maint on these systems, fill the washer tank and forget about it the way I set them up. I can wire it so if fluid runs out or system fails it will cut boost control and drop you to safe levels.

4. Larger injectors. Even a stage 2 cobb OTS tune maxes out stock injectors, fuel pump upgrade. You have forged pistons why are you wasting them, lol. Time for a 20g or a DOM3XT. You could easilly have a 400WHP+ daily driver that would be as reliable as stock at those levels.

Setup an appointment with me to bring you car down to the shop one day and we can sit down and write out your options. For the $500 your talking about on a CAI you could upgrade the turbo for a little more and really open the flow up. You want to get rid of the sleepy turbo over 5400rpm don't you? lol. I couldn't stand the stock STI turbo personally once it was running above stock pressure.

[P3Auto]

Originally Posted by rivman05

Ok, either or it doesnt matter a whole lot to me. I just need to get it to the point of being snappy again...doubling injector size, and a bigger maf dont help gettin around.

What ever you want. Call me so we can go over a plan. If you car has cats still installed we will need to find a good way to put my wideband kit on your car to do the work. I have bungs we can weld in if need be.

[rack]

Originally Posted by P3Auto

Setup an appointment with me to bring you car down to the shop one day and

His signature shows "Tri-State Area' ?
Specifically NJ

[P3Auto]

Haha guess that will be a tough one.

[nathan.d.kim]

Hey, thanks a lot for the information. You're right about the intake in terms of minimal gains.
I definitely had an interest in the water/alcohol injection kit for quite some time. If anything, I was looking at the HFS-6 from Aquamist because of its quality fittings, fail-safes, and clean set-up. However, the unit costs approx. $900, plus installation, and another tune. Easily takes the budget to the mid-1000's. I noticed that my clutch springs are starting to pop at "spirited" driving and quick shifts, so that will be the next upgrade - clutch kit and light weight flywheel. That also will cost about $1600 (tri-state area cost). =P
I feel as if I am married to a high maintenance garage queen.
Yes, Wasilla, AK is a bit far for me to travel to for some car work. I've never been to AK before, but have heard a lot about the Subaru community there. Maybe one day.
Thanks again.

[P3Auto]

Look into snowperformance.net the kit they sell is very nice. The support is very good and you can get what you want for around $500 . Good luck to you.

[AKSubieDubie]

What's your take on the per cylinder timing compensation? I've seen different model years apply different retard values for different cylinders. I'm thinking it's in the header design, short vs long (inefficient). I'll have to dig around to find out what year/model does what here in a bit.
My ECU is 04 sti

[P3Auto]

Originally Posted by AKSubieDubie

What's your take on the per cylinder timing compensation? I've seen different model years apply different retard values for different cylinders. I'm thinking it's in the header design, short vs long (inefficient). I'll have to dig around to find out what year/model does what here in a bit.
My ECU is 04 sti

Ok are you ready for this?

The reason that I at least feel Subaru runs slightly more advanced timing on the back pistons is because of the position of the knock sensor. The engineers wanted slight knock to be heard the best. By advancing the cyls closest to the knock sensor it will hear and detect knock where it might miss slight knock from a front piston.

Ever wonder why the back pistons seem to be the winner for piston damage...If we look at an 05 STI tune we will find the front cyl timing is retarded as much as -3 degrees at certain rpms while the rear cyls are not retarding timing at all.This may not seem like a lot of timing difference but even slight knock can turn severe quickly. In other words 20 degrees may not knock at all, where as 21 degrees may start to knock. Iit might take 3-8 degrees of timing reduction to quiet the knock started by the 1 degree of advance.

This is why many Subarus I have had to tune had "flat spots" around 5000RPM or so. The car was detecting knock but having a knee jerk reaction pulling timing out to stop it. By reducing timing a little in the hot spots the end result is more power and timing since the ECU won't be having to pull gross amounts to stop the knock event.

Sorry got off on a bit of a rant.

To summarzie, I see no reason to mess with the per cyl timing compensation tables. I'm sure there is some optimization that could be done but it would require special equipment to monitor each cyl for temp, pressure, etc.