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Old 11-03-2006, 01:51 PM   #1
Mach V Dan
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Member#: 12029
Join Date: Nov 2001
Chapter/Region: MAIC
Location: Sterling, VA
Default Tuning by Mach V Dan: Case #249 (graphs inside)

Second in an ongoing series. My goal is to share some of the Subarus we tune and discuss them a little bit, hopefully educating. Maybe learning some, too.

This customer has an '06 STI with a turbo-back exhaust (with cat) and an SPT intake. Engine management is Cobb AccessPort. The downpipe is a style that has a wastegate tube that bypasses the downpipe cat.

The first odd thing about this car was the surprisingly low power level with the off-the-shelf Stage 2 map. It was off by about 20 hp compared to the last Stage 2 STI we tuned. Then I looked at the air/fuel trace -- completely rich, past 10.0:1! It appears that the SPT intake is throwing the MAF calibration out of whack. (I think there's a thread about this that the Cobb guys wrote. My experience matches with at least some of that.)

The customer mentioned that he'd been getting terrible mileage; I guess that explains it. I spent some time recalibrating the MAF transfer function, then proceeded dialing in the fuel/boost/timing.

The car ended up making very good power, almost 307 at the wheels. Very impressive for a car with a cat on it. The injector duty cycle was showing completely pegged out at anything past 5000 rpms, though. Any further power mods will require larger fuel injectors (and, from experience, a fuel pump).

Horsepower and torque:



Horsepower vs. wheel speed:


Notice how the power level actually goes down and then back up in the lower trace! Definitely not optimal.

--Dan
Mach V
FastWRX.com
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Old 11-03-2006, 02:02 PM   #2
xcntrk75
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Member#: 60224
Join Date: Apr 2004
Chapter/Region: MAIC
Location: NOVA
Vehicle:
2008 FXT Sports 2.5
Dark Grey Metallic

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You got to love how that 2.5l can spin a VF39 so quickly, looks like full torque by 3200 RPM!

What’s with the unusual hump in the torque curve?
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Old 11-03-2006, 02:20 PM   #3
TurbojonLS
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2 Cars, No Bling

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Wow - that car should really tear up the course now!

What AFR did you target? Can you post it up?
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Old 11-03-2006, 03:09 PM   #4
Mach V Dan
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Quote:
Originally Posted by xcntrk75 View Post
What’s with the unusual hump in the torque curve?
The turbo was basically overshooting its target by a bit when the boost first came on. It wasn't that dramatic on some of the other runs.

Quote:
What AFR did you target? Can you post it up?
Mid-11 tapering down towards 11.0:1 near redline. Here's the graph.



Note the blue curve is all the way to the floor, as rich as it can read. It goes up at the end because the probe kept blowing out of the tailpipe. We had to double-up the safety wire holding it in.

--Dan
Mach V
FastWRX.com
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Old 11-03-2006, 04:05 PM   #5
Butt Dyno
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Location: NoVA
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2016 FoST ST3
2006 Evo #17 STU

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Ahh the SPT intake. 4 years too late and apparently kind of a disaster.

WTG, SOA.

john
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Old 11-03-2006, 05:09 PM   #6
mav1c
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Location: Woodbridge, VA
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2006 STi, 16 Outback
Crystal Gray, Silver

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This graph explains the hesitation I was feeling on the straights.

Quote:
Originally Posted by Mach V Dan View Post

Horsepower vs. wheel speed:


Notice how the power level actually goes down and then back up in the lower trace! Definitely not optimal.

--Dan
Mach V
FastWRX.com
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Old 11-03-2006, 05:11 PM   #7
mav1c
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Crystal Gray, Silver

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Yeah. I got suckered in. I figured SOA knew what they were doing. IT sure looks and sounds good, but obviously doesn't work so well, at least not on the STI. Now that the car is tuned for it, it will stay on.

Quote:
Originally Posted by ButtDyno View Post
Ahh the SPT intake. 4 years too late and apparently kind of a disaster.

WTG, SOA.

john
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Old 11-03-2006, 05:47 PM   #8
AcquaCow
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Location: Reston VA
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2011 DGM WRX hatch

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I'll be by Mach V for a tune shortly I hope.

Wanna get this AP 2.0 =)

-- Dave
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Old 11-03-2006, 07:01 PM   #9
Imprezive_04
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WRB

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I'd like to see if the typhoon has similar results
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Old 11-03-2006, 07:39 PM   #10
spazegun2213
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very nice Tim!

Dan, you may have another customer here in a short few weeks (aka, as soon as someone buys my utec).
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Old 11-03-2006, 07:57 PM   #11
AcquaCow
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Quote:
Originally Posted by Imprezive_04 View Post
I'd like to see if the typhoon has similar results
No, we did that test already:



-- Dave
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Old 11-03-2006, 08:23 PM   #12
Imprezive_04
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that test with the K&N is stock. The car in this post had the intake, DP, and AP and was 20 hp off and runnning way rich. How does the graph of a stock car say anything about if the K&N would have similar results or not.
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Old 11-03-2006, 08:30 PM   #13
AcquaCow
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2011 DGM WRX hatch

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Quote:
Originally Posted by Imprezive_04 View Post
that test with the K&N is stock. The car in this post had the intake, DP, and AP and was 20 hp off and runnning way rich. How does the graph of a stock car say anything about if the K&N would have similar results or not.
It's the only one of those things that would affect the MAF?

Dan has seen Aaron's car several times.

Aaron is quite vocal about anything that would cause him issue.

If the K&N were ever an issue throughout his build, Aaron would have said something.

I have Aaron's K&N on my car now, I'll put a DP on and go dyno for you

-- Dave
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