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10-17-2005, 10:13 AM | #1 |
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Race gas and ignition advance
I leave my tuning to the experts @ KTR, but am curious what a "safe" overall increase in ignition advance (across the board) would be if you were running a high-octane blend (call it 96 octane) on a normal 93 octane map. I understand results will vary from setup to setup, but am curious if there are general conventions when using user tuning features (e.g., DeltaDash) in running higher than normal octane. Thanks,
- scooter
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10-17-2005, 12:13 PM | #2 |
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a bump in 3 octane points isn't that much.
if you're just adjusting advance, i would say about 3*. that's where i'd start anyway. you really have to try it out and see though. for example, i don't think 5* is out of the question, but i certainly wouldn't start there. jm2c ken |
10-17-2005, 01:19 PM | #3 | |
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10-17-2005, 01:39 PM | #4 |
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9* is a bit scary. that's a big window of advance.
remember by bumping advance that much you're opening the "knock window" substantially. that's the amount of time per combustion event that knock CAN pop its head in and ruin the party. extra advance is never guaranteed to buy you power. it MAY just be increasing peak cylinder pressure unnecessarily, without adding appreciably to the average pressure. most of the time we ARE octane limited and therefore the extra advance DOES work to our advantage but that's certainly not set in stone. if you could add 9 degrees, would it make more power than 8? than 7? i'd say almost certainly yes. would 100 octane be enough to support that advance and not knock? that's tougher to say. my engine still has excellent compression on all 4 cylinders because i approach it from the "richer, less boost, less advance" direction and slowly creep up on the limits. personally, when i get some octane, i like cranking the boost... but that's me! to answer your question i would not assume 1* per octane point. that's just what i've seen while playing around with 93 and some doping agents (ie methanol, tolulene, etc). the key is that i personally have not attempted to push 9* more on a 91 map when putting in 100, so i can't give direct known-good advice on it. taken to a logical extension, we don't see c16 maps with 25* of advance on top of the 93 maps. again, you reach a point where the extra advance does nothing beneficial and actually starts hurting. maybe someone with more experience in this direct 91-100 situation can comment. |
10-17-2005, 01:54 PM | #5 |
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Having started this thread... I now have the sinking feelingly that I'm falling into the same trap of someone who wants to strap on an MBC and is asking "how much boost on a stock 2005 is OK?"
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10-17-2005, 02:33 PM | #6 |
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Octane is one of those things that lets you get closer to the optimal timing point where you are making as much power as you can and increasing timing further only increases cylinder pressure while negligibly adding power.
So if starting with 91 octane and increasing, the jump from 91 to 95 will let you add a lot more timing and power than you can when going from 95 to 100. If you want more power, you need to start adding boost and leaning out closer to 12.5:1. A lot of tuners will tune timing last. Usually the tuning process goes something like this: Load up conservative timing map. Tune boost profile as desired/possible on given octane. Tune A/F ratio as desired/possible. Tune timing as desired/possible being careful to not add too much timing. Tweak all 3 as necessary. For a safe tune, most will recommend that if you do hit knock while tuning, to turn down the timing 1-3 degrees to ensure that you've got some safety margin there. |
10-17-2005, 04:47 PM | #7 | |||
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What would be a good place to start with if jumping from 91oct. to 100oct? Maybe +6* more? That would still put me running 30* at redline, which just seems like a LOT of timing... Thanks for the tips though... -jason |
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10-17-2005, 05:23 PM | #8 |
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There is not across the board number to run. That would just be dumb. I'd advance in 2 degree increments and watch det signal. If you are on a dyno you can watch torque too.
Keep in mind you are likely pulling fuel when tuning race gas, and this is going to affect timing as well. |
10-17-2005, 05:28 PM | #9 |
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jason:
put the gas in and just turn up the boost to 20 psi. hold on tight. i'd run ~15* at torque peak, and maybe 27 up top, depending on how much boost it will hold. your lower CR is helping keep things quiet. fwiw, i run those exact #s NOW on 93 octane with a vf23. 20psi and all, 11.5:1 afr. so i know they're realistic. will your turbo run out of air? sure. will it lose efficiency and end up making a hotter charge temp? yep... but that's what the octane is there for! jmho, ymmv, etc ken |
10-17-2005, 11:15 PM | #10 | |
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10-17-2005, 11:59 PM | #11 | |
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10-18-2005, 12:28 AM | #12 | |
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10-18-2005, 02:36 AM | #13 |
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i believe that the 24 is the modified ecu signal...if you've ever used a utec it's what you input in the timing map...when you look at a log it's what comes up in the "mod ign deg" column....
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10-18-2005, 03:48 AM | #14 | |
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10-18-2005, 07:16 AM | #15 | |
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my vf23 has a MUCH smaller compressor than your 1820. i was running almost 30* with the oem turbo at redline. |
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10-18-2005, 10:14 AM | #16 |
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gas is way too expensive
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10-18-2005, 12:21 PM | #17 | |
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Conversely, I'm seeing some of the guys with higher compression like 8.5:1 only being able to run 15-18* up top and even lower at peak torque. I guess if I gonna make a map for 100 oct. I should just bite the bullet and invest $50-$75 in drums of the high octane at the race shops and actually road tune the entire map for it. I just don't know how close I can get my fuel map by road tuning with only a few gallons race gas... considering I've fine tuned my 91oct street map over the course of about a year now, and many many tank fulls of gas. -jason |
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10-18-2005, 12:58 PM | #18 |
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i agree that the static CR is the big variable here. if we have "perfect" turbo setups, running 1 bar of boost on an 8:1 yields a 16:1 effective CR, whereas in your case with 7.5:1 we get 15:1. that could easily be a couple of degrees.
also i should point out again that my 14-15* range is in highest load, or 20+psi. iirc in those areas i might be running a couple degrees more in the 80 column, so maybe 16-17. that rpm point is 4k to 5k btw. have you considered rescaling the MAP load columns? what's your current MAP range? |
10-19-2005, 10:02 AM | #19 | |
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Remember that octane rating does not mean slower burning. Racing fuel does not provide more power becasue it has a higher octane rating, but due to its other qualities which make it burn more slowly and cooler. In a very "reader digested" statement, AFR adjustments increase power by, in effect, making a more explosive mixture, and increase EGT. Timing adjustments make power by making sure all the fuel burns at the flame front. Too much advance, then some fuel explodes just like a diesel, from compression and temperature, not from the spark. |
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10-19-2005, 12:00 PM | #20 | ||
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10-19-2005, 12:30 PM | #21 |
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Here are maps from tuning my STi. As you can see I need to do something with my timing as well. Can I bring up the UTEC map to match the ECU timing in those areas? And this is all on 93 oct in PA. Next year I plan on running 100-105 octane. The boost is pretty much at the limit of the turbo already and I need bigger fuel injectors. Can you guys comment about how much timing you think I can advance?
Thanks, Justin Timing Last edited by crystalhelix; 10-19-2005 at 01:34 PM. |
10-19-2005, 01:14 PM | #22 |
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Maybe you should not run race gas if you are unwilling to dial it in. You can gain 20%+ power by tuning for it, but if safety is your main goal, then why not bump up the octane by point or two and go race. The power difference you'll gain from tuned race gas is probably less than 10% of the racing "skill" you'll need to win. You may be better off spending time on your foot work than fueling.
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10-19-2005, 01:48 PM | #23 | |
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can you post the log that you gathered that data from? ken |
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10-19-2005, 02:19 PM | #24 | |
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Ken,
I am pretty sure this is the log to that data. Quote:
Code:
Load Knock Mod Mod Mod WB RPM MAP MAF TPS Site Count Ign#1 Inj#1 Ign Fuel Boost MAF AFR psia V % deg duty deg % (CL) V 3103 -5.4 2.4 15 00 00 +45.1 12.0 ECU. +0.0 ECU. 2.3 14.65 3121 -5.2 2.4 15 00 00 +45.4 11.8 ECU. +0.0 ECU. 2.4 14.65 3109 -5.2 2.4 15 00 00 +45.2 12.8 ECU. +0.0 ECU. 2.4 14.58 3118 -5.2 2.4 15 00 00 +45.4 10.3 ECU. +0.0 ECU. 2.4 14.58 2970 +1.9 3.2 102 20 00 +22.9 29.0 +17.0 +1.7 450.00 3.3 14.49 3083 +3.9 3.3 102 30 00 +17.8 34.9 +17.0 +2.0 450.00 3.5 14.08 3245 +6.0 3.6 102 50 00 +14.3 44.3 +16.2 +2.5 450.00 3.8 13.42 3397 +8.6 3.8 101 60 00 +11.9 56.3 +16.6 +3.8 450.00 3.9 12.86 3580 +11.9 4.0 102 80 00 +11.5 66.1 +15.0 +3.2 450.00 4.1 12.25 3831 +15.1 4.0 101 100 00 +15.4 72.2 +14.9 +3.2 450.00 4.1 11.62 4070 +17.5 4.0 102 100 00 +19.7 75.5 +16.6 +3.5 450.00 4.2 11.24 4171 +19.2 4.0 101 100 00 +20.4 77.5 +17.3 +4.7 450.00 4.2 11.05 4368 +19.8 4.1 101 100 00 +20.7 83.5 +17.9 +4.5 450.00 4.3 11.01 4559 +19.4 4.2 101 100 00 +21.6 86.8 +18.6 +3.6 450.00 4.3 11.05 4960 +19.0 4.2 101 100 00 +22.3 87.2 +19.5 +2.5 450.00 4.3 11.01 5027 +19.0 4.3 101 100 00 +22.4 93.4 +20.0 +2.5 375.00 4.4 11.01 5265 +17.9 4.3 101 90 00 +22.1 92.9 +21.1 +2.6 325.00 4.4 11.08 5482 +17.7 4.3 101 90 00 +23.1 89.6 +22.0 +2.6 325.00 4.4 11.02 5491 +17.1 4.3 101 90 00 +23.1 92.7 +22.2 +2.9 300.00 4.4 10.93 5847 +16.3 4.3 101 80 00 +23.4 92.0 +22.6 +2.9 300.00 4.4 10.87 5847 +15.9 4.3 102 80 00 +23.6 96.1 +22.6 +2.8 300.00 4.4 10.89 6230 +15.1 4.3 101 80 00 +23.8 ---.- +24.6 +2.8 275.00 4.4 10.80 5973 +14.9 4.3 101 80 00 +24.2 ---.- +24.8 +3.0 275.00 4.5 10.71 6497 +14.5 4.3 102 80 00 +25.0 99.8 +26.2 +3.0 275.00 4.5 10.68 6535 +14.3 4.3 101 80 00 +27.9 ---.- +26.7 +3.0 250.00 4.5 10.78 6548 +14.5 4.3 101 80 00 +28.6 ---.- +26.7 +3.0 250.00 4.5 10.93 6361 +13.5 3.9 1 00 00 +24.5 22.6 ECU. +0.4 325.00 2.1 10.89 6105 +8.0 1.6 0 00 00 +23.2 6.6 ECU. +0.5 ECU. 1.7 11.37 5757 +1.9 1.8 0 00 00 +23.4 7.1 ECU. +0.2 ECU. 1.8 12.78 |
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10-19-2005, 02:53 PM | #25 | ||
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