Hey all, I’m attempting to better understand the methodology behind successful ignition tuning procedures. I’ve reviewed a couple UTEC tuning manuals and none really seem to cover in much detail how ignition timing should be configured throughout the RPM range (other then if you experience knock to retard timing). I’m also trying to understand how the following concept is applied to a timing MAP:

Advance Timing:
More Power
Lower EGT’s
More prone to knock

Retard Timing:
More Torque
Higher EGT’s
Less prone to knock

With the above in mind, is it better then to configure timing with minimal advance throughout the spool-up range (3~5k rpm) in order to establish more torque and higher EGT’s (to help spool)? Then start to ramp up an increase of timing advance above spool (5k +) in order to obtain top-end power?

If anybody can help provide an understanding of how to approach ignition timing tuning, please provide your comments…
Thanks in advance :D

Retarding the timing advance doesn't make more torque then advancing it. As far as I know power is a result of torque, and more power at a given rpm would mean more torque. When people say you get more torque by retarding timing, they mean that you might be able to build boost quicker with more retarded timing because of the hotter exhaust gasses, and the higher boost would result in more torque and power quicker. From what I've heard, more people seem to think that it's better to run more timing then less during spool.

peace

Thanks for the response hippy…

That logic seems to make sense. One of the challenges I’m struggling with is identifying what “mich_the_ginge” refers to as Minimum Best Timing (MBT) or in other words, point of diminishing returns. It’s especially tough to identify this point while street tuning as opposed to on the dyno where hp/tq numbers are available. As I research more it appear that too much advance past MBT, yet prior to obvious knock, can still be very harming. Again according to mich “too much timing advance is just like knock, it generates extreme cylinder pressures that end up breaking things”.

In my prior street tuning session, I think I surpassed MBT as I got to the point where adding more timing didn’t cause any change in butt-dyno power, or feel. Additionally adding more timing down low seemed to make the car “pull” less throughout the onset of boost. It used to “pull” very hard, now not so much after increasing timing across the board.

Here’s a snapshot of my timing map. Note that this is Alky injection enabled.


Timing Map
[-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100]
[-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100]
[-100] [39] [36] [33] [30] [28] [28] [28] [28] [28] [28]
[-100] [38] [35] [32] [29] [27] [27] [27] [27] [28] [28]
[-100] [37] [34] [31] [28] [26] [26] [26] [26] [27] [27]
[-100] [36] [33] [30] [27] [25] [25] [25] [25] [26] [26]
[-100] [35] [32] [29] [26] [24] [24] [24] [24] [25] [25]
[-100] [34] [31] [28] [25] [23] [23] [23] [23] [24] [24]
[-100] [33] [30] [27] [24] [22] [22] [22] [22] [23] [23]
[-100] [32] [29] [26] [23] [21] [20] [20] [20] [21] [21]
[-100] [31] [28] [25] [22] [20] [16] [15] [15] [16] [16]
[-100] [30] [27] [24] [21] [19] [16] [15] [15] [16] [16]
[-100] [29] [26] [23] [20] [18] [16] [15] [15] [16] [16]
[-100] [28] [25] [22] [19] [17] [16] [15] [15] [16] [16]
[-100] [27] [24] [21] [18] [17] [16] [15] [15] [16] [16]
[-100] [26] [23] [20] [18] [17] [16] [15] [15] [16] [16]
[-100] [25] [22] [20] [18] [17] [18] [17] [17] [18] [18]
[-100] [24] [21] [20] [19] [18] [17] [17] [17] [18] [18]
[-100] [23] [21] [20] [19] [19] [17] [17] [17] [18] [18]
[-100] [22] [21] [20] [19] [19] [19] [19] [20] [20] [20]
[-100] [23] [23] [23] [23] [22] [23] [21] [22] [23] [23]
[-100] [22] [22] [22] [22] [22] [23] [22] [23] [24] [24]
[-100] [22] [22] [22] [22] [22] [23] [22] [23] [24] [24]
[-100] [22] [22] [22] [22] [22] [23] [22] [23] [24] [24]
[-100] [22] [22] [21] [21] [21] [22] [22] [23] [24] [24]
[-100] [22] [22] [21] [21] [21] [22] [23] [24] [25] [25]
[-100] [24] [24] [23] [23] [22] [23] [23] [24] [25] [25]
[-100] [24] [24] [23] [23] [22] [23] [23] [24] [25] [25]
[-100] [24] [24] [23] [23] [22] [23] [23] [24] [25] [25]
[-100] [24] [24] [23] [23] [22] [23] [23] [24] [25] [25]
[-100] [24] [24] [23] [23] [22] [23] [23] [24] [25] [25]
[-100] [24] [24] [23] [23] [22] [23] [23] [24] [25] [25]
[-100] [24] [24] [23] [23] [22] [23] [23] [24] [24] [24]
[-100] [24] [24] [23] [23] [22] [22] [22] [23] [23] [23]
[-100] [24] [24] [23] [23] [22] [22] [22] [22] [22] [22]
[-100] [24] [24] [23] [23] [22] [22] [22] [22] [22] [22]
[-100] [24] [24] [23] [23] [22] [22] [22] [22] [22] [22]
[-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100]
[-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100]
[-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100] [-100]


And here’s a snapshot of a log from said map. You’ll see that at +36 timing up top, I’m probably well past MBT and in to some serious danger zone, although I never reached knock nor exceeded 1550 EGT.


Load Knock Mod Mod Mod
RPM MAP MAF TPS Site Count AFR Ign#1 Inj#1 Ign Fuel Boost MAF WB
psia V % deg duty deg % (CL) V AFR
2637 -7.3 2.2 7 0 0 W/B 40.2 7.4 ECU. -1.5 ECU. 2 14.42
2637 -7.3 2.2 7 0 0 W/B 40.3 5.4 ECU. -1.5 ECU. 2 14.65
2660 -7.1 2.6 18 0 0 W/B 39.8 32.8 ECU. -1.5 ECU. 2.5 14.83
2656 -5.3 2.7 100 10 0 W/B 34.9 10.5 30.5 -9 237.5 2.3 14.96
2668 -3.4 2.8 100 10 0 W/B 35.2 11 30.3 -9.1 350 2.3 14.92
2679 -1.4 2.8 100 10 0 W/B 35 12.1 29.1 -9.2 325 2.4 14.7
2725 0.6 2.8 100 10 0 W/B 34.2 12.7 27.7 -9.3 350 2.4 14.05
2752 1.3 2.9 99 20 0 W/B 34.1 12.7 27.1 -11.8 350 2.4 13.06
2761 1.9 2.9 100 20 0 W/B 33.8 13.1 26.5 -10.5 350 2.4 12.52
2808 2.3 3 100 20 0 W/B 33.4 13.8 25.9 -10.8 350 2.5 12.46
2824 2.7 2.9 100 20 0 W/B 33.2 13.9 25 -10.8 350 2.4 12.37
2836 2.9 3 100 20 0 W/B 33.1 14.9 24.6 -11.2 350 2.5 12.21
2876 3.3 3.1 100 20 0 W/B 33 14.9 24.1 -11.2 350 2.5 12.11
2901 3.7 3 100 30 0 W/B 33 14.8 23.2 -11.8 350 2.5 12.02
2929 3.9 3.1 100 30 0 W/B 33 15.6 22.5 -11.9 350 2.5 11.98
2957 4.3 3.1 100 30 0 W/B 32.9 15.9 22.3 -12.1 350 2.6 12
2992 4.7 3.2 100 30 0 W/B 32.8 16.2 21.7 -12.2 350 2.6 11.98
3022 5.1 3.2 100 30 0 W/B 32.6 16.2 20.6 -12.4 350 2.6 11.87
3060 5.5 3.2 100 40 0 W/B 32.7 16.3 19.7 -12.8 350 2.6 11.84
3092 5.9 3.2 100 40 0 W/B 32.6 16.8 19.5 -13.2 350 2.6 11.84
3115 6.4 3.3 100 40 0 W/B 32.5 17.4 19 -13.8 350 2.6 11.81
3115 6.6 3.2 100 40 0 W/B 32.4 18.7 18.3 -13.4 350 2.6 11.71
3132 6.8 3.3 101 40 0 W/B 32.5 18.1 18.2 -14 350 2.5 11.65
3165 7.4 3.3 100 40 0 W/B 32.3 19.3 17.5 -14 350 2.6 11.68
3239 7.8 3.4 100 50 0 W/B 32.2 19.9 17 -14 350 2.7 11.67
3245 8.2 3.5 100 50 0 W/B 32.2 21.2 16.8 -14.2 350 2.7 11.62
3333 8.6 3.5 100 50 0 W/B 32 20.6 16.5 -14 325 2.7 11.53
3346 9.2 3.6 100 60 0 W/B 31.9 21.7 16 -14.8 325 2.7 11.49
3346 9.6 3.6 100 60 0 W/B 32 23 15.7 -15.1 350 2.8 11.53
3411 10.4 3.5 100 60 0 W/B 30.5 23.9 15.5 -15.5 350 2.8 11.49
3472 11 3.7 100 60 0 W/B 31.6 24 15.2 -15.8 350 2.9 11.27
3472 11.7 3.8 100 70 0 W/B 31.5 25.2 15 -16.9 350 2.9 11.33
3572 12.7 3.8 100 70 0 W/B 31.7 26.4 15 -16.9 350 2.9 11.49
3580 13.7 3.7 100 80 0 W/B 31.8 27.8 15.5 -17.3 350 2.9 11.49
3595 14.9 3.8 100 90 0 W/B 31.2 29.5 16 -17.3 350 2.9 11.52
3646 16.4 3.8 100 100 0 W/B 31.1 30.1 16 -18.2 350 3 11.52
3766 17.6 4 100 100 0 W/B 30.9 31.2 16 -18.9 350 2.9 11.56
3783 19 4 100 100 0 W/B 30.8 32.7 16.5 -18.6 325 3.1 11.8
3875 20 4.1 99 100 0 W/B 30.8 34.5 16.6 -18.6 350 3 11.98
3853 21 4.1 100 100 0 W/B 30.5 34.5 17.2 -18.7 350 3.2 12.02
3982 21.5 4.3 100 100 0 W/B 30 37.7 18 -18.5 350 3.2 12.05
4025 21.7 4.1 99 100 0 W/B 29.6 38 17.8 -18.5 350 3 12
4025 21.9 4.3 99 100 0 W/B 29.6 35.6 18 -18.9 350 3.2 11.92
4074 21.9 4.3 100 100 0 W/B 29.6 37.1 18 -18.7 350 3.2 11.87
4156 22.5 4.3 99 100 0 W/B 29.5 38.4 18 -18.7 350 3.1 12
4214 22.7 4.3 99 100 0 W/B 28.4 39.7 18 -18.4 350 3.2 12.17
4295 22.5 4.4 100 100 0 W/B 28 42.3 18 -18.4 325 3.2 12.09
4334 22.9 4.3 99 100 0 W/B 27.3 41.9 18 -18.4 325 3.2 12
4385 22.7 4.3 99 100 0 W/B 26.8 44.6 18.1 -18.4 325 3.3 12.11
4516 22.9 4.4 98 100 0 W/B 26.5 45.5 18 -19.4 325 3.2 12.21
4572 23.3 4.4 98 100 0 W/B 27.6 44.2 18.3 -18.7 350 3.3 12.21
4668 23.3 4.4 99 100 0 W/B 27.3 43.3 19.1 -18.5 325 3.3 12.17
4597 23.5 4.4 99 100 0 W/B 27.7 44.5 19.2 -19 325 3.3 12.11
4649 23.7 4.4 99 100 0 W/B 28.1 44 19.5 -20.2 325 3.3 12.09
4714 23.5 4.4 98 100 0 W/B 27.9 44.8 19.7 -19.9 325 3.3 12.17
4789 23.7 4.5 98 100 0 W/B 27.9 45.7 21.1 -19.8 325 3.3 12.21
4844 23.5 4.5 99 100 0 W/B 28.4 46.9 21.5 -20 325 3.3 12.21
4967 23.3 4.4 98 100 0 W/B 29.1 45.2 21.8 -20.1 325 3.3 12.18
4967 23.5 4.5 98 100 0 W/B 30.6 46.5 22.6 -20.1 325 3.3 12.17
5020 23.5 4.4 98 100 0 W/B 29.1 45.6 23 -20.3 325 3.3 12.17
5050 23.3 4.5 98 100 0 W/B 30.7 48.2 23.6 -20.3 325 3.3 12.21
5128 22.9 4.5 98 100 0 W/B 31.6 46.8 23.4 -20.3 325 3.3 12.23
5151 22.5 4.5 99 100 0 W/B 30.8 49.9 23.5 -20.3 325 3.3 12.21
5232 21.9 4.5 99 100 0 W/B 31.5 49.2 23.8 -20.3 325 3.3 12.18
5249 22.1 4.5 98 100 0 W/B 31.4 48.1 24 -20.3 325 3.3 12.17
5316 22.7 4.6 98 100 0 W/B 31.5 49.6 24 -20.3 325 3.3 12.14
5333 23.1 4.5 98 100 0 W/B 31.9 50.8 24 -20.3 325 3.3 12.18
5446 23.1 4.6 98 100 0 W/B 31.8 50.8 24 -20.3 325 3.3 12.25
5464 22.9 4.6 98 100 0 W/B 31.9 50 24 -20.3 325 3.3 12.21
5464 22.1 4.6 99 100 0 W/B 32.1 51.8 24 -20.1 325 3.4 12.21
5509 22.1 4.6 99 100 0 W/B 31.9 52.2 24 -20.3 325 3.4 12.11
5555 22.3 4.6 98 100 0 W/B 32.5 52.9 24 -20.2 325 3.4 12.02
5630 22.7 4.6 98 100 0 W/B 32.5 54.1 24 -20 325 3.4 12.06
5640 22.9 4.6 98 100 0 W/B 32.9 55.5 24 -20.1 325 3.4 11.98
5797 23.1 4.6 98 100 0 W/B 33 53.9 24 -19.4 325 3.4 11.89
5787 23.1 4.6 100 100 0 W/B 33.2 53.7 24 -19.4 350 3.4 11.81
5747 23.3 4.7 98 100 0 W/B 33.3 55 24 -19.5 325 3.4 11.81
5777 23.5 4.7 99 100 0 W/B 33.7 54.5 24 -19.7 325 3.4 11.8
5889 23.5 4.7 98 100 0 W/B 34.7 57.5 24 -19.7 325 3.4 11.81
5868 23.3 4.6 98 100 0 W/B 34 55 24 -19.5 325 3.4 11.81
5931 22.9 4.7 98 100 0 W/B 34.6 56.2 24 -19.5 325 3.5 11.8
5889 22.7 4.7 98 100 0 W/B 34.4 56.7 24 -19.5 325 3.5 11.77
6049 22.7 4.7 100 100 0 W/B 34.9 57.3 24 -19.5 350 3.4 11.71
6049 22.5 4.6 98 100 0 W/B 35.6 58.2 24 -19.3 325 3.5 11.68
6116 22.3 4.7 98 100 0 W/B 35.5 57.4 24 -19.3 325 3.5 11.68
6150 22.1 4.7 98 100 0 W/B 36 57.5 24.2 -19.3 325 3.5 11.65
6060 22.1 4.7 98 100 0 W/B 36.7 55.7 24.3 -19.4 325 3.5 11.62
6172 22.3 4.7 98 100 0 W/B 36.7 57.6 24.5 -19.4 325 3.5 11.62
6161 21.9 4.6 99 100 0 W/B 37.1 56.4 24.6 -19.5 325 3.5 11.62
6195 22.3 4.7 98 100 0 W/B 37 54.7 25 -19.8 325 3.5 11.65
6016 19.6 3.7 0 90 0 W/B 11 29.4 ECU. -15.9 LCM. 2 12.06
5518 12.1 2 0 20 0 W/B 11 5.9 ECU. -16.3 LCM. 1.5 14.53


Is this too much advance up top???? :confused:
Any additional comments appreciated...

MBT is very hard to see unless the car is on a dyno. I expect to gain between 5-10 HP per degree of timing I add. I get the boost and fueling about right then I start working on the timing. As I add timing if I do not see a gain between 5-10 HP then I remove that degree as I know I am at or past MBT.

Another thing to note that as I add timing I usually have to adjust the fuel. Adding timing gives the fuel more time to burn thus you end up going leaner. So as I add timing I add fuel. Same for removing timing, as I remove timing I usually find myself removing fuel.

You are not running 36, you are running 24.6 as I can see from that log. When the UTEC is in control just ignore what the stock ECU wants to run.

The long and the short of it is that timing can not be accurately adjusted without a means by which to measure gains or losses- IE a dyno. I never touch on the street.

You are not running 36, you are running 24.6 as I can see from that log. When the UTEC is in control just ignore what the stock ECU wants to run. Thanks for the clarification. It seems I’m monitoring the wrong UTEC log value for timing advance :lol: Silly noob mistake…

So the “Modified Ignition Degree” is the proper value set to watch then. Anybody else running alky want to chime in with how much advance they commonly run? Granted every setup is different but maybe there’s a general ball-park for alky injection users?

The long and the short of it is that timing can not be accurately adjusted without a means by which to measure gains or losses- IE a dyno. I never touch on the street. Yeah that’s becoming obvious to me now. As I ramp-up timing advance up top it becomes increasingly difficult to “feel” the minor changes on the street. Maybe I should probably quit messing with it before I blow something up :eek:

Your timing looks pretty good to me. Sometimes it's hard to tell where to stop advancing the timing, even on a dyno. What if you could advance the timing 5 more degrees in areas without getting diminished returns or knock? It would make ya wanna try to advance the timing more since that would obviously be the point of what you're trying to accomplish(more safe power). What happens if you constantly run into knock b4 the advance nets diminished returns? Then you're constantly bashing your engine while trying to get the best tune you can(no matter where you tune). At some point you either take the risk or say that's enough.......

One thing to think about is that you might not be getting the most efficient use of your timing because of the a/f ratio you're running(or the boost, but....). Ya might wanna try leaning out the a/f ratio a bit in different areas to see what happens. As always, this is just my opinion from what I've seen/heard, and I'm no expert.

peace

Something else to think about, don't get to caught up with an ideal AFR and especially an IDEAL ignition advance. My car, while not stock, doesn't want much advance at all at higher boost on 93 octane. We're talking 11-14 deg BTDC at 21-22 psi.

what turbo is that?

nice airflow rate.

..My car, while not stock, doesn't want much advance at all at higher boost on 93 octane. We're talking 11-14 deg BTDC at 21-22 psi. I assume your motor doesn’t like to run much advance due to an increase in compression ratio, is that correct?

Your vehicle details seem to indicate you’re running a 2.5l short-block which I imagine is using OEM 2.5 head-gaskets with 2.0l (wrx) heads, thereby increasing the compression ratio which requires less ignition-timing advance to make power :confused:

what turbo is that?
nice airflow rate. Thanxs.. It’s a VF-22 ported, with external wastegate open-dumped… Seems to make great power especially with the combination of EWG and EBC. Very solid boost control with no fussy spiking, creep, or fluctuation. Measures in at about 330whp running a mid-12 second 1/4 mile. Likely is pushing the little EJ205 harder then it should considering stock internals and all. We’ll see how long it lasts under this type of setup…

I assume your motor doesn’t like to run much advance due to an increase in compression ratio, is that correct?

Your vehicle details seem to indicate you’re running a 2.5l short-block which I imagine is using OEM 2.5 head-gaskets with 2.0l (wrx) heads, thereby increasing the compression ratio and requires less ignition-timing advance to make power :confused:



It's a 2.5L STI SB overbore for 100.5mm pistons. The pistons are custom made at 8.4:1CR for the WRX head volumes and stock STI gaskets. I can actually push decent timing down low but at higher boost I've noticed that it doesn't want much advance. My guess is that the combustion process is quite good, hence the lack of advance needed for higher boost psi. FWIW, 8.4:1CR isn't much at all.

Here's a log on 50/50 mix of E85. Don't pay attention to the ECU ignition after UTEC takes over because I've been working on the ECU -> UTEC crossover (re-flashing). Also, don't pay attention to my MAFv since it's in a 3.5" housing.



Load Knock Mod Mod Mod
RPM MAP MAF TPS Site Count AFR Ign#1 Inj#1 Ign Fuel Boost MAF
psig V % deg duty deg % (CL) V
2564 -9.2 1.7 12 00 00 12.7 +21.4 7.9 ECU. +0.0 425.00 1.7
2566 -7.5 1.8 15 00 00 13.8 +23.5 8.6 ECU. +0.0 425.00 1.8
2575 -5.9 1.9 18 00 00 14.2 +23.5 9.9 ECU. +0.0 425.00 1.9
2606 -4.3 1.9 23 00 00 15.0 +23.1 9.8 ECU. +0.0 425.00 2.0
2639 -2.8 1.9 25 00 00 14.6 +22.9 9.9 ECU. +0.0 425.00 2.0
2630 -1.8 2.0 25 00 00 14.6 +22.8 11.5 ECU. +0.0 425.00 1.9
2656 -1.0 2.0 26 00 00 14.5 +22.8 11.7 ECU. +0.0 425.00 2.0
2694 -0.6 2.0 26 00 00 14.6 +23.0 12.9 ECU. +0.0 425.00 2.0
2721 -0.4 2.0 26 00 00 14.1 +22.8 13.2 ECU. +0.0 425.00 2.0
2750 -0.2 2.0 25 00 00 14.9 +23.9 11.5 ECU. +0.0 425.00 2.0
2748 -0.2 2.0 25 00 00 14.8 +23.8 13.4 ECU. +0.0 425.00 2.2
2768 +0.0 2.1 26 00 00 14.4 +23.9 11.5 ECU. +0.0 425.00 2.0
2820 +0.2 2.0 25 00 00 14.8 +24.2 11.8 ECU. +0.0 425.00 2.0
2801 +0.4 2.0 24 00 00 14.7 +24.5 12.0 ECU. +0.0 425.00 2.0
2834 +0.4 2.1 22 00 00 14.7 +24.6 11.9 ECU. +0.0 425.00 2.1
2871 +0.4 2.0 23 00 00 14.7 +24.1 11.8 ECU. +0.0 425.00 2.1
2876 +0.2 2.0 23 00 00 14.8 +24.6 12.6 ECU. +0.0 425.00 2.0
2883 +0.4 2.1 28 00 00 15.0 +24.5 12.4 ECU. +0.0 425.00 2.1
2926 +0.8 2.1 44 10 00 15.8 +24.2 13.7 +22.6 +0.0 425.00 2.3
2994 +1.6 2.2 74 10 00 15.4 +23.6 16.2 +22.2 +0.0 425.00 2.3
3013 +2.5 2.2 98 10 00 14.9 +20.4 16.3 +22.1 +0.0 WGS. 2.3
3033 +2.9 2.3 102 10 00 14.3 +19.0 18.4 +22.3 +0.0 WGS. 2.4
3044 +3.3 2.4 101 10 00 13.3 +16.8 19.0 +22.2 +0.0 WGS. 2.3
3115 +3.7 2.5 102 20 00 13.4 +16.4 20.1 +21.9 +0.0 WGS. 2.5
3132 +4.3 2.4 102 20 00 12.9 +13.2 19.3 +21.8 +0.0 WGS. 2.4
3168 +4.9 2.4 102 20 00 12.7 +13.3 20.5 +21.8 +0.0 WGS. 2.4
3217 +5.5 2.4 101 20 00 12.8 +13.3 22.3 +21.9 +0.0 WGS. 2.6
3239 +6.1 2.6 102 30 00 rich +12.8 22.4 +22.0 +0.0 WGS. 2.5
3350 +6.3 2.6 102 30 00 rich +12.8 23.7 +22.0 +0.0 WGS. 2.8
3363 +6.7 2.5 101 30 00 rich +12.7 24.4 +22.0 +0.0 WGS. 2.7
3394 +6.9 2.7 101 30 00 rich +12.8 24.5 +22.0 +0.0 WGS. 2.7
3422 +7.8 2.7 102 30 00 rich +12.9 26.2 +21.7 +0.0 WGS. 2.8
3483 +8.4 2.8 102 40 00 rich +12.8 26.2 +21.1 +0.0 WGS. 2.9
3501 +9.0 2.9 102 40 00 rich +12.6 27.2 +21.0 +0.0 WGS. 2.8
3588 +9.4 2.8 102 40 00 rich +12.3 25.8 +21.0 +0.0 WGS. 2.7
3595 +9.6 2.8 102 40 00 rich +12.6 25.1 +20.9 +0.0 WGS. 2.8
3695 +10.0 2.9 102 40 00 rich +12.8 29.4 +20.5 +0.0 WGS. 2.9
3720 +10.6 2.9 102 40 00 rich +13.1 28.1 +20.3 +0.0 425.00 3.0
3728 +11.6 3.0 102 50 00 12.1 +13.1 29.6 +19.5 +0.0 425.00 2.9
3840 +12.0 3.1 102 50 00 rich +13.4 35.6 +18.9 +0.0 425.00 3.0
3866 +13.1 3.1 102 50 00 rich +13.8 38.9 +17.9 +0.0 425.00 3.0
3912 +14.3 3.1 93 60 00 rich +13.7 44.1 +16.2 +0.0 425.00 3.2

It's a 2.5L STI SB overbore for 100.5mm pistons. The pistons are custom made at 8.4:1CR for the WRX head volumes and stock STI gaskets. Nice setup! :eek:

I’m in the process of planning my 2.5sb hybrid build as well:
Right now I’m considering used 2.5sb, possibly with mild ring-land or low cylinder pressure (i.e. cheap but not destroyed)
Go with the Weisco 0.5mm overbore forged pistons
Combine with OEM 2.5 headgaskets and 2.0l heads to net a 9:1 compression ratio.
And if enough cash is available, Helix 264 cams…

mmmmm.... :D

Do you have local dyno days? You could also ask your shops to rent a couple of hours of dyno time.

At a dyno day you can usually get 4-5 pulls in for a reasonable price. One warm up throw-away pull,.then have pre-made maps ready to test.

When I go to local dyno days I usualy test my constantly-tweaked-daily-driver base map and a couple experimental maps.