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Old 07-04-2005, 02:34 PM   #1
Kevin Thomas
Street Racing Instructor
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Member#: 110
Join Date: Jul 1999
Location: 1997 OBS, 1996 SVX, 1988 RX
Vehicle:
1989 1989 XT6

Default Advancing Ignition Timing Dyno Results

Car: 1989 AWD/Autotranny XT6
Mods: JC Sports Intake, ProECM Pulley, Custom-made Rallispec Header, 2.5" aftermarket cat and exhaust, 2.5" Dynomax Ultraflow SS muffler.
Extras: Using 93 Octane today and bumped up ignition timing
Car nickname: Redrum

Took the XT6 to the dynoshop today to see how ignition timing affects horsepower and torque. I'll be posting a few dyno plots to show what you can expect.

Since this car is an auto, I always dyno from the bottom of first gear all the way to the top of 3rd gear. This is to simulate full throttle runs like on a dragstrip to get real world numbers. Also, I dyno the XT6 in FWD mode. I did this previously because my tranny was bad and it would not shift into the next gear in AWD. Plus all the wheels would not move at the same time. Now that the tranny is fixed, I try to stay consistant with dynoing in FWD mode. Drivetrain losses in FWD mode is still 33%.

Also, for some reason the car would not stay in gear that long as it used to do. It shifts a little earlier coming out of 3rd gear. Oh well!

The first dyno plot is comparing HP figures of 20 degree timing (stock/base timing ) vs a ignition timing brought up to about 26-27 degrees. I had to use the Flexplate since my pulley does not have a 'nick' in it for me to see timing with the timing light. This plot shows a hp increase in all gears that seem pretty even throughout. Look at the point I chose on the dyno chart. At base timing, I made 117.24hp while with ignition timing at about 26-27 degrees the car made 124.20hp. About a 7hp increase.



The 2nd graph is a torque comparison of the base 20 degree timing vs 26-27 degrees of timing advance (on 93 octane). The point I chose to show an example is in 3rd gear. Stock 20 degree timing shows 118.61lb-ft of torque while the 26-27 degree run shows 125.38lb-ft. 6.77lbs of torque gained. Not too bad!

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Last edited by Kevin Thomas; 10-14-2005 at 01:01 PM.
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Old 07-04-2005, 06:00 PM   #2
Diz
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Chapter/Region: RMIC
Location: Colorado Mountains
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2004 Porsche 911
2004 Mazdaspeed MX-5

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Good results for a simple change. How did you advance the timing? Are you running the advance across the rev range?
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Old 07-04-2005, 08:18 PM   #3
Patrick Olsen
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Location: Where the Navy sends me...
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1997 Legacy 2.5GT
QuickSilver Metallic

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Good stuff, Kevin. I can't wait to get back to the mainland so I have access to an AWD dyno again and can "play" like this.

Pat Olsen
'97 Legacy 2.5GT sedan
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Old 07-04-2005, 09:47 PM   #4
Kevin Thomas
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Join Date: Jul 1999
Location: 1997 OBS, 1996 SVX, 1988 RX
Vehicle:
1989 1989 XT6

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Quote:
Originally Posted by Diz
Good results for a simple change. How did you advance the timing? Are you running the advance across the rev range?
Old school scoobies like the XT6 have a distributor cap. A simple twist from the stock base timing to 26 degrees is all it takes. It's now set at 32 degrees advanced since I tested that as well. No noticable power gain from 26 to 32, however the dyno lines seemed a little smoother. So 32 degrees it is.
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Old 07-05-2005, 11:12 AM   #5
Diz
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2004 Mazdaspeed MX-5

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Quote:
Originally Posted by Kevin Thomas
Old school scoobies like the XT6 have a distributor cap.
I was wondering about that. Old school kicks arse.
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Old 07-05-2005, 02:42 PM   #6
Chav
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RSTi

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Quote:
Originally Posted by Kevin Thomas
Old school scoobies like the XT6 have a distributor cap. A simple twist from the stock base timing to 26 degrees is all it takes. It's now set at 32 degrees advanced since I tested that as well. No noticable power gain from 26 to 32, however the dyno lines seemed a little smoother. So 32 degrees it is.
Hey Kevin,
Great results, but I do have one thing to ask. You are probably close to MBT at 28 degrees since you don't see any improvement when advancing past that, but why advance it further when you are dramatically increasing cylinder pressure and the risk of predet for a smoother power curve?

-Chav
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Old 07-05-2005, 07:33 PM   #7
Kevin Thomas
Street Racing Instructor
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Member#: 110
Join Date: Jul 1999
Location: 1997 OBS, 1996 SVX, 1988 RX
Vehicle:
1989 1989 XT6

Default

Quote:
Originally Posted by Chav
Hey Kevin,
Great results, but I do have one thing to ask. You are probably close to MBT at 28 degrees since you don't see any improvement when advancing past that, but why advance it further when you are dramatically increasing cylinder pressure and the risk of predet for a smoother power curve?

-Chav
I wasn't thinking about the dramatically increased cylinder pressure. This is interesting! I kept it at 32 degrees because I felt that a smoother curve without detonation was ideal rather than a wavy one. I'll show you what I mean with a little closer look.

Here's a horsepower graph with the 26 degree timing run above vs my 32 degree advanced timing in 3rd gear. I could show all the gears but figured this one may be best.


Now, I'm by no means a tuner. I simply try to run my EGTs close to stock but I have no EGT gauge on this car. So I just ran these tests and if I got no detonation, it must be 'good'. I figured the smoother line was an indication of a better all-around running condition with all else being equal. The graph is really expanded and the difference at the point I picked (5400rpm) is only as little as 1hp but when you look at it closely, this is what the powerband is doing. I just noticed that hey, it's smoother when I do this vs that so if I got no det, it must be better. Average power across the whole range should be a tiny bit better than the 26 degree run but hey, when we are N/A, we take what we can get right?

Here's the torque graph of the 26 degree advance vs 32.

At about the same rpm range, it's only a difference of 2lb-ft of torque but overall, it just looks smoother. Perhaps if someone else that played with timing on another Subaru like the 2.5RS could post up, maybe they'll notice a difference in the waves with ignition timing as well.
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