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Old 03-01-2006, 12:30 AM   #1
ScotS
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Default Is the Cobb AP Stage 1 safer than stock?

In reference to the second graph in this thread:

http://forums.nasioc.com/forums/showthread.php?t=862531

Can someone explain why the stock ECU's A/F ratio graph looks the way it does? Is this safe? I'm kinda assuming it's not the greatest so is there a safe way to drive the car? No full throttle until past 3500 rpm?
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Old 03-01-2006, 08:37 PM   #2
Hawke
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I'm guessing you are talking about why the AFR is at 14.7. It's because of the open loop / closed loop fueling delay that subaru implemented in 2004 for emissions.
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Old 03-01-2006, 08:42 PM   #3
KingOfSiam
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Of course stock is safe.
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Old 03-02-2006, 03:00 AM   #4
ScotS
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Quote:
Originally Posted by Hawke
I'm guessing you are talking about why the AFR is at 14.7. It's because of the open loop / closed loop fueling delay that subaru implemented in 2004 for emissions.
Yes, I was wondering about that. Why is it like that? From what I've read in the above mentioned thread, boost and too lean of a mixture is not good.

So, does this mean if you go full throttle below ~3500 rpm, you risk detonation? I ask because I've heard mild? knocking on my stock '06.

Changing the subject, does the dyno load increase with rpm? I'm assuming the load increases to simulate aerodynamic drag?

Perhaps I'm not phrasing my question the right way...sorry, I am trying. What I am trying to figure out is in reference to this from Christian at Cobb:

"This vehicle is leaner at lower RPM then richens up as RPM increases. You can also clearly see the closed-loop to open-loop delay. This vehicle had generated approximately 8 lbs. of boost by 3000 RPM where it was still running in CL at a 14.5-14.7 A/F ratio. I could feel this while driving on the street. Below 3000 RPM the vehicle feels like it has turbo lag and it also feels inconsistent. Torque tended to move more below 3000 RPM on the dyno as well. I could feel the car stumble trying to burn that lean on the dyno and on the street. At 3000 RPM the vehicle picks up then takes off at 3500 RPM."

I've personally noticed weird, for lack of a better descriptor, glitch in the throttle around 3500 rpm. It's not always there and I haven't yet figured out how to duplicate it, but it definately does not "feel" right.
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Old 03-02-2006, 03:05 AM   #5
nhluhr
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I would say no.

Cobb Stage1 increases the boost level over stock and is meant to be used on a totally stock vehicle. There is every reason to believe that EGTs in a totally stock exhaust setup are very high (not to mention unevenly hot on the 2/4 bank). To increase boost pressures from stock level is to increase the EGTs even more.

I am not saying Cobb Stage1 cars are failure-prone (they certainly aren't) but you are definitely pushing closer to the limits.
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Old 03-02-2006, 07:36 AM   #6
crazymikie
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Here's something to consider, though-

On my 04 WRX when it was completely stock, I saw EGT temperatures of close to 1700 in the uppipe. This CL/OL delay seems to be worse on the 04/05, however, I haven't had a chance to play with an 06 WRX so I really can't say for sure.

In any case, by fixing the CL/OL delay, I would guess EGTs could go down (depending on how the delay logic works).

Adding boost could raise EGTs, but fixing the delay could lower them.
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