In-depth Suby tuning Q's
Thread Starter
VIP Member
Joined: Mar 2003
Posts: 2,023
From: Phoenix, AZ
Car Info: Subaru Impreza WRX 2002
In-depth Suby tuning Q's
Now that I have a ECU data monitor for my 02 WRX, I'm really curious as to how to interpret some of the data. Is there a good resource for answering some of the following questions (or does anyone have answers):
1) What is the typical degree of knock correction under WOT with a stock EJ20?
2) What is the ideal/preferred EGT for the car, as measured by the uppipe sensor? In other words, at what heat is the exhaust system most efficient, as heat = energy?
3) What is the ideal spark ignition temperature? Why does this vary so hugely while driving (I have seen it go from 11 degrees to 44 in a few seconds)? Is this related to RPM, or engine loading, or both?
4) Where is the intake temperature measured -- at the MAF?
5) Can I calculate the torque I am generating from the engine load sensor?
That's just for starters, I've got a lot more
In any case, if there is some magic repository of ECU tricks and EJ20 arcana out there, please share.
1) What is the typical degree of knock correction under WOT with a stock EJ20?
2) What is the ideal/preferred EGT for the car, as measured by the uppipe sensor? In other words, at what heat is the exhaust system most efficient, as heat = energy?
3) What is the ideal spark ignition temperature? Why does this vary so hugely while driving (I have seen it go from 11 degrees to 44 in a few seconds)? Is this related to RPM, or engine loading, or both?
4) Where is the intake temperature measured -- at the MAF?
5) Can I calculate the torque I am generating from the engine load sensor?
That's just for starters, I've got a lot more
In any case, if there is some magic repository of ECU tricks and EJ20 arcana out there, please share.
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With a stock ECU, knock correction values generally range from 4-10 degrees depending on RPM and load.
EGT's also vary quite a bit, but generally don't exceed 1500 degrees.
The ignition timing is number of degrees of ignition advance the ECU is running. This varies widely with load and RPM. At WOT, you will generally see ~10* at spoolup and gradually going to about 28* at redline.
The IAT is indeed located at the MAF. This is an inherent problem for Subarus because the ECU has no way of knowing if the TMIC is heatsoaked.
You can't directly get torque from engine load, but there are programs called Road Dynos that can calculate torque and HP from RPM data using other data such as gearing, tire size, weight, etc.
If you have any other questions, feel free to send me a PM or IM me on AIM.
Thanks
EGT's also vary quite a bit, but generally don't exceed 1500 degrees.
The ignition timing is number of degrees of ignition advance the ECU is running. This varies widely with load and RPM. At WOT, you will generally see ~10* at spoolup and gradually going to about 28* at redline.
The IAT is indeed located at the MAF. This is an inherent problem for Subarus because the ECU has no way of knowing if the TMIC is heatsoaked.
You can't directly get torque from engine load, but there are programs called Road Dynos that can calculate torque and HP from RPM data using other data such as gearing, tire size, weight, etc.
If you have any other questions, feel free to send me a PM or IM me on AIM.
Thanks
Thread Starter
VIP Member
Joined: Mar 2003
Posts: 2,023
From: Phoenix, AZ
Car Info: Subaru Impreza WRX 2002
This is great information, thanks. Looks like my EJ20 is pretty healthy; I never go over 5 degrees of knock correction, and my EGTs are in the mid 1300s (low 1400s at or just after WOT). I just want to establish a baseline of engine behavior and stats before I actually begin to tune the engine.
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Actually, higher knock correction values mean that the ECU is happier.
The knock correction value is the number of degrees of ignition advance the ECU is adding in on top of the base ignition map. It will try to add as much as possible untill it senses knock. So lower knock correction numbers generally mean that the ECU has encountered some knock in that region.
The knock correction value is the number of degrees of ignition advance the ECU is adding in on top of the base ignition map. It will try to add as much as possible untill it senses knock. So lower knock correction numbers generally mean that the ECU has encountered some knock in that region.
Thread Starter
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Joined: Mar 2003
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From: Phoenix, AZ
Car Info: Subaru Impreza WRX 2002
Yesterday I had a friend ride along and watch the ECU meter display so I could drive aggressively and not wreck the car -- he noticed that my knock correction actually goes up to 13-15 at WOT right before a shift, too fast for me to have seen before. I also hit 14.7psi on the stock turbo with a stock ECU setting, pretty good for an 02 However, turning on the A/C caps my boost at 13.9, no matter what the conditions or how deep into the RPMs I go 
-- he noticed that my knock correction actually goes up to 13-15 at WOT right before a shift, too fast for me to have seen before. I also hit 14.7psi on the stock turbo with a stock ECU setting, pretty good for an 02 However, turning on the A/C caps my boost at 13.9, no matter what the conditions or how deep into the RPMs I go
iClub Silver Vendor
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It sounds like your car is running fine. If you'd like to make sure, log a WOT pull from 2k RPM to redline in third gear. E-mail me the log and I'll let you know if I see any trouble spots. Make sure to log RPM, total timing, knock correction, Ignition Advance Multiplier, Injector Duty Cycle, TPS, MAF, IAT, and engine load. If you do this pull on a completely flat road, I can even plot your hp and torque in my road dyno software. In this case be sure to include your tires size and any mods in the e-mail.
Thanks
Thanks
iClub Silver Vendor
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Ah.. that's too bad. That sort of information is kinda useless unless you can log it. If you do ever manage to log the data, feel free to contact me for help interpreting it.
Thanks
Thanks
Registered User
Joined: Jan 2003
Posts: 22
From: Florence, Alabama
Car Info: 2002 Blue Wagon
What would you recommend as a data logger. Something that could also log a wideband O2 and EGT would be preferable.
Is the AP datat logger sufficient or should I look elsewhere?
Thanks,
BOB
Is the AP datat logger sufficient or should I look elsewhere?
Thanks,
BOB
iClub Silver Vendor
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Originally Posted by drflowers
What would you recommend as a data logger. Something that could also log a wideband O2 and EGT would be preferable.
Is the AP datat logger sufficient or should I look elsewhere?
Thanks,
BOB
Is the AP datat logger sufficient or should I look elsewhere?
Thanks,
BOB
Thanks
Registered User
Joined: Feb 2007
Posts: 4
From: Redding, CA
Car Info: 03 Outback, 04 WRX, 06 LGT
A few Qs for Ed
Hello Ed,
I had been trying to chase you down for some time and get you to road or dyno tune my WRX.
I have an 04 WRX with a COBB AP, Street tuner, Big FP16G w/EVO III wheel, STi pink injectors, APS top mount, Invidia catless exhaust and a turboxs intake.
From what I have seen, when you first load a map, you typically wont see the boost targets that you have set. Cobb says the computer needs to 'learn' the new setup first, then you will see target boost after a few days (up to a week) of driving. If I am seeing 95% wastegate duty cycle immediately, how is the computer keeping the boost down?
I am shooting for 19psi boost from 4k to 5.6k but I am having trouble getting that. The WG duty cycle is 95%+. I know it isnt a mechanical issue as I had been hitting that boost level with a protune using the exact same mechanical setup (nothing mechanical has been changed).
Under high boost, I seem to be locked into an 11.25:1 A/F ratio. Why is that?
Max boost seems to only be seen in 5th gear. Is this observation correct? It seems that ST has no way to get around that. If this is correct, a manual or electronic external boost controller would be the fix... yes?
I have attached a datalog as well as my ST map.
I see that I can add more timing according to my dynamic advance values. According to Cobb, my temps arent bad.
Can you give a novice any pointers here?
I have my check book in hand if you have the desire to put your tuning hat on!!
Thanks,
Ralph
I had been trying to chase you down for some time and get you to road or dyno tune my WRX.
I have an 04 WRX with a COBB AP, Street tuner, Big FP16G w/EVO III wheel, STi pink injectors, APS top mount, Invidia catless exhaust and a turboxs intake.
From what I have seen, when you first load a map, you typically wont see the boost targets that you have set. Cobb says the computer needs to 'learn' the new setup first, then you will see target boost after a few days (up to a week) of driving. If I am seeing 95% wastegate duty cycle immediately, how is the computer keeping the boost down?
I am shooting for 19psi boost from 4k to 5.6k but I am having trouble getting that. The WG duty cycle is 95%+. I know it isnt a mechanical issue as I had been hitting that boost level with a protune using the exact same mechanical setup (nothing mechanical has been changed).
Under high boost, I seem to be locked into an 11.25:1 A/F ratio. Why is that?
Max boost seems to only be seen in 5th gear. Is this observation correct? It seems that ST has no way to get around that. If this is correct, a manual or electronic external boost controller would be the fix... yes?
I have attached a datalog as well as my ST map.
I see that I can add more timing according to my dynamic advance values. According to Cobb, my temps arent bad.
Can you give a novice any pointers here?
I have my check book in hand if you have the desire to put your tuning hat on!!
Thanks,
Ralph