Hows my spark advance?

[reactor2]

Could I get a boost expert to do me a favor and look at my spark advance? I'd like to know if it looks like I'm going down the right path.

AFR: Around 11.0 (93 pump, 0 KR)

Car info:
98 A4
Dart Pro 1 205cc (10.8:1 compression)
228/232 .571/.573 112
Fast Intake, 90mm LS2
BBK headers
160* thermostat
A&A/Procharger P1SC - 5PSI
Yank SS3600
3.42 rearend

I've seen several tunes where boosted cars just run flat timing across the RPM range, which doesn't seem to make any sense as it seems it should be starting high and tapering low as boost builds. With what I have now, I have good throttle response.

With my setup, should I be more aggressive with the timing and AFR (lean)? I don't plan on running meth.

Thanks for the advice!

98_A4_HCI_5PSI.hpt

[reactor2]

I've looked at a number of boost tunes, granted they are all > 5psi but the spark advance looks like:

2200 rpm 6000 rpm

.60 g/cyl 20 20 20 20 20 20 19 19 19 19 19 18 18 18 18 18 18 17
.................................................. ..........................................
1.0 g/cyl 20 20 20 20 20 20 19 19 19 19 19 18 18 18 18 18 18 17

Similarly, AFR looks to target 11.5 at anywhere in the RPM range.

Seems to me the timing shouldn't be pulled nor AFR richened up until boost is building and it sure the heck isn't building at 2200 rpm...at least it isn't with my setup....I don't hit 5psi until I'm nearing 6000 rpm and I don't rise above atmospheric until 3200+ or so. Also, it seems that regular spirited driving (not WOT) is occurring under airflow 70 g/cyl. If there isn't boost, why would I want to pull timing? I tried a timing pattern like the above and the result was a sluggish driving experience...which makes sense, I've pulled timing where the car was behaving like a NA setup.

AFR. Why are people targeting 11.5 at any point WOT? Like I said, it seems to make sense to build to this (e.g. 12.5 - 11.0 from 3000 - 6000)...as boost is added fuel is richened up. Why would I want to have the same ARF at 1 PSI that I would at 10 PSI?

So what am I missing? Is a "safe tune" = "lazy tune"?

Also, when I originally installed my SC, I figured I would richen up the AFR to be safe (maxing to 10.0 at 6000) and I would pull timing if I recorded any KR. I ran stock timing, 93 octane and octane boost and recorded 0 KR in all cells. People told me I was "lucky" to now have grenaded my motor. Am I missing something? If I'm logging 0 KR why would I want to pull timing? I have since pulled timing, but only as boost builds...starting at 27* (2000 rpm) decreasing to 16* at 6000 rpm. 0 KR as always.

AFR. Again, start at 12.5 (2200 rpm) and drop to 10.0ish by 6400 rpm...basically all boost levels (1 psi and below) will be < 11.0 afr.

Does this make sense or am I completely missing something? Car drives great. Great throttle response all around. Maybe I'm at an advantage as I'm running a high stall....at WOT I am never less than 3800-4000 RPM is any gear.

[obzidian]

You're not going to make any real power with that rich of an afr. Get it to hover around 11.5 and u should be fine.

However I do remember reading a long time ago where folks would vary their afr for max torque and max hp. Leaner at peak rwhp and richer at peak rwtrq. Best thing to do would be is to strap the car down and see what works best.

I would nail that afr first then see how she likes for timing. Good luck.

[reactor2]

You're not going to make any real power with that rich of an afr. Get it to hover around 11.5 and u should be fine.

However I do remember reading a long time ago where folks would vary their afr for max torque and max hp. Leaner at peak rwhp and richer at peak rwtrq. Best thing to do would be is to strap the car down and see what works best.

I would nail that afr first then see how she likes for timing. Good luck.

I leaned it out to closer to 11.2. I think its time to get to dyno and strap it down. I made 4 runs, the last was a cement freeway entrance ramp with a textured surface. I was unable to successfully get to WOT as the back tires kept braking loose. I have big tires (345/35/18) but they aren't soft tires. I'm starting off in second and trying to slowly roll into full throttle. Last attempt I made it to 60 mph then the tires let loose and it started to go sideways.

Logged timing (0 KR in all cells)
4.0_4.4_4.8_5.2_5.6__6.0
19_18__17__17__17__16

Logged AFR
4.0___4.4___4.8___5.2___5.6___6.0
11.23_10.9__11.22_11.33 _11.10_11.20

questions:
1) I can't obviously safely make a run in 3rd gear on the street. How much richer/leaner can I expect to see the AFR in 3rd, with the converter locked? I'd like to tune that in before getting to the dyno.

2) How reliable are the exhaust mounted wide bands? I'm running the PLX Devices WB. Its cheap ($300), especially compared to the sniffers used by the tuning shops. Am I potentially lean even though HP Tuners is telling me its 11.2-11.3?

BTW: I'm running 6 gallons of 100 octane w/ 93 octane.

[MMGT1]

The "Big Shop Boys" would never use, as you say, the 300 dollar sensors, but for us they are pretty dam good man. I tuned my car to 12.9 AFR using a NTK/AFX set up and when checked with a lab grade, 12 gas O2 I was putting out 12.8... not shabby if you ask me when my little 300 dollar sensor had no problem knocking boots with a ten thousand "Big Shop" dollar set up

[obzidian]

exhaust mounted?? As in clamped down to the tailpipe?

If so then yes your readings are not accurate to what is being displayed in your logs.

I believe the rule of thumb (how many thumbs do we have anyways, geesh?!) is that the output is going to be anywhere from .3 to .5 off. I have never used one so I cant say for certain except for the air-assisted versions you'll use on a dyno. however... you could be as far as 11.8.

I personally would leave it as such, try to get your error percentage tighter (its fine as it is though except for that one spot in the 10's) and move on. Or confirm with another wb.

[reactor2]

exhaust mounted?? As in clamped down to the tailpipe?

If so then yes your readings are not accurate to what is being displayed in your logs.

I believe the rule of thumb (how many thumbs do we have anyways, geesh?!) is that the output is going to be anywhere from .3 to .5 off. I have never used one so I cant say for certain except for the air-assisted versions you'll use on a dyno. however... you could be as far as 11.8.

I personally would leave it as such, try to get your error percentage tighter (its fine as it is though except for that one spot in the 10's) and move on. Or confirm with another wb.

No, not clamped to the tailpipe. Its welded in several inches back from the collector on the driver's side.

[reactor2]

So how does my timing table look in my tune? Since boost doesn't occur at all rpms, well not significant anyway, I'm trying to scale the timing accordingly. That is, as RPM increases, spark advance decreases. What I have in the current tune seems to work well. What I don't know, is if the spark advance I have specified will work equally as well with 3rd gear pulls, which of course I can't do on the street. Keeping in mind that at WOT the minimum RPM my engine will spin is around 4000 rpm (in any gear)...especially 2nd and 3rd.

If any experts could take a look to see if any obvious issues are apparent, I'd greatly appreciate it.

[MMGT1]

You may have been looking at what I would call a full race tune. Ive seen some serious builds use the exact timing right across the g/cyl range. If you look at their timing table in 2-d view, every timing curve perfectly matches the one before it, looks like one curve on the graph! This is a quarter mile tune, not ment for street use at all. Running the boost your running Id be in the 18-20* range at the end of the table that would get carried through, and blend up as you are doing. I think your timing is a bit low. Lean it out though as suggested. Get that thing in the 11.5 range and see if the timing will hold without KR. Ultimately, you need that dyno for MBT and that way you can nail your timing and get that fuel right in WOT. On only 5psi you should be hitting the 20* range bud, even at 11:1 comp. I ran an engine at 10.49 on 14 PSI and made 18* up top. Conversion wise I was really at almost 20 comp under full boost and ran 18* timing just fine. Yours works out to be around 14.75:1 comp by the way at 0 sea level, it would drop as you increase in elevation. Say you raced it at 4500 feet you would be running 13.75:1 and so on...

[reactor2]

You may have been looking at what I would call a full race tune. Ive seen some serious builds use the exact timing right across the g/cyl range. If you look at their timing table in 2-d view, every timing curve perfectly matches the one before it, looks like one curve on the graph! This is a quarter mile tune, not ment for street use at all. Running the boost your running Id be in the 18-20* range at the end of the table that would get carried through, and blend up as you are doing. I think your timing is a bit low. Lean it out though as suggested. Get that thing in the 11.5 range and see if the timing will hold without KR. Ultimately, you need that dyno for MBT and that way you can nail your timing and get that fuel right in WOT. On only 5psi you should be hitting the 20* range bud, even at 11:1 comp. I ran an engine at 10.49 on 14 PSI and made 18* up top. Conversion wise I was really at almost 20 comp under full boost and ran 18* timing just fine. Yours works out to be around 14.75:1 comp by the way at 0 sea level, it would drop as you increase in elevation. Say you raced it at 4500 feet you would be running 13.75:1 and so on...

Thanks for the response! Moving it to 11.5 and testing again the weekend. I'll also increase the timing a bit to see how it likes is.