Okay, so I got a custom Dynoflash two years ago by big Al. The tune is awesome! I was tuned on 94 octane and have the same exact mods on the car. Nothing has changed except for the octane. Sunoco 94 was removed from the market forcing me to use 93. Everyone told me that 1 octane point is not a big deal. I think that it is. Look at the huge difference in tuning for 91 versus 93. That's only 2 octane points difference. Anyhow, I hopped into the car with a local guy who does the ECU Flash thing and wanted him to log some third gear pulls. We encountered a knock sum of 6 at the most, right where full boost comes in. (I'm boosting to around a 22 spike then taper to about 20 by redline.) Boost have been left the same. After doing some research, a knock sum of 6 is not considered acceptable. The only thing I could think of without detuning a great tune was to mix up my own 94 octane. So I got some 104 and mixed it in the ratio of 1/7 gallons. That winds up with a 94.5 or so octane. After resetting the ECU and one third gear pull, the butt dyno says I've just gained quite a bit of HP! It feels like the day Al tuned the car! Anyhow, we're going to go out tonight and see what the new logs say. Can any of you guys tell me if my tune is off because of switching to 93? Any experience in the same boat? I hate to start messing with the tune to compensate for 93. I'd rather just keep using the 93 mixed with a small amount of 104. Any suggestions on how to proceed? I will post up the new log numbers tonight.

(I could have posted this in the Dynoflash thread, but since we're using the Mitsulogger and Evoscan, I think it was justified here. Thanks for any help and suggestions.)

 

It could well be the change from 94 to 93. Its possible that you had a few knock counts even on 94, and then the switch to 93 added a few more. If you want to keep the power, seems that you're going to have to make your custom mix.

 

Here is a question ... did you ever do a log on the 94 to verify that there was no knock to start with? I'm not saying it's true, but you could have had that knock all along.

I do agree that dropping a full point COULD have a big difference. But, remember, the octane rating at the pump is a minimum number and that 93 you're pumping could have a little more if you're using quality fuel. Your 94 could have been 95 and the current 93 could be 94.

Let us know how the logs go with the 94.5 mix.

 

Okay, I just got home from doing a good number of pulls with my friends. All legally on a closed course! I will post up all of the logs when my friend emails them to me. The very first third gear pull showed mostly 0's and one 2 at the most. (knock sum) The second was very similar. We did some 2-3-4 pulls, a 5th, a couple more 3rds, and a 4th. The worst knock I got was a 3. Like someone posted, you never can really compare one day to the next, or one gas to the next, but I saw Al's log of my car whenever he finished tuning it. And it did not pull any timing. So it couldn't have been having a knock sum of 6 at certain points, right? My conclusion has to be the 94 to 93 change that was forced upon me. I might have to look into the homemade octane booster thread to make my own!

Anyhow, an expert, or even a person with moderate knowledge should look at the two different logs. One was on 93 and the next was on 94. (Same boost, same mods, similar weather conditions and temperature. And remember, I was tuned on 94. Thanks for the help guys. Hopefully I can get them on here soon!

 

Hey man, it's chad with the black evo from the meet last night. I am kinda interested in where you purchased the fuel from. I have noticed serious power loss when I purchased gas from a few particular stations. I am wondering if you got your 93 from one of the stations that I had a bad experience with. PS f you need to do any more logging I could meet up with you cable & laptop in hand. I would really like to look at your maps along with logs to see what is going on. L8R

 

That's very interesting... I get always get gas from BP now, usually in Monroeville, the one on 22. But from what I've heard, a lot of the stations usually are filled up by the same trucks anyhow. Who knows. could be an issue though.

 

Hmm BP wasn't one of the ones that I had a problem with. GetGo was definitely one of them. I made the mistake of filling up with 93 from GetGo & my car felt sluggish & I ended up getting somewhere in the area of 13mpg & at that time I did 50% highway driving. Switched back to Sunoco & mpg went back up over 20.

Another to steer clear of is Sheetz. They actually get the leftover & bottom of the barrel from the other gas stations. That is why they are usually cheaper than other places.

 

I'm having a real tough time putting up the logs.

 

TPS RPM TimingAdv Speed LoadCalc KnockSum

37.2549 1843.75 23 21.12662 106.45 0
100 1906.25 20 21.12662 101.59 0
100 1937.5 20 22.36936 101.07 0
100 1937.5 19 22.36936 100.31 0
100 1937.5 19 22.36936 100.31 0
100 2000 20 22.36936 104.44 0
100 2031.25 20 22.36936 100.44 0
100 2031.25 19 23.61211 104.57 0
100 2062.5 19 23.61211 104.32 0
100 2093.75 19 23.61211 104.57 0
100 2125 19 23.61211 104.32 0
100 2156.25 18 23.61211 104.57 0
100 2218.75 18 24.85485 108.7 0
100 2250 18 24.85485 108.7 0
100 2250 18 24.85485 109.26 0
100 2281.25 18 24.85485 109.38 0
100 2343.75 17 24.85485 112.7 0
100 2375 17 24.85485 116.96 0
100 2406.25 17 27.34033 117.57 0
100 2437.5 16 27.34033 121.73 1
100 2468.75 15 27.34033 138.26 1
100 2531.25 15 27.34033 124.58 1
100 2562.5 14 27.34033 128.11 3
100 2593.75 12 28.58308 131.73 3
100 2656.25 11 28.58308 134.26 3
100 2687.5 11 28.58308 141.35 2
100 2750 10 28.58308 141.82 2
100 2812.5 10 28.58308 146.66 2
100 2843.75 10 32.3113 156.36 2
100 2906.25 9 32.3113 161.45 2
100 2937.5 9 32.3113 170.66 2
100 3000 8 32.3113 178.82 1
100 3093.75 8 32.3113 193.54 1
100 3125 7 36.03953 210.24 1
100 3218.75 7 36.03953 224.45 1
100 3312.5 7 36.03953 233.58 1
100 3406.25 7 36.03953 230.11 1
100 3500 7 36.03953 224.35 5
100 3562.5 5 36.03953 225.55 5
100 3656.25 5 39.76776 225.55 6
100 3718.75 5 39.76776 225.55 6
100 3875 5 39.76776 223.23 6
100 3937.5 5 39.76776 219.7 6
100 4000 5 39.76776 219.7 5
100 4093.75 5 45.98147 218.52 5
100 4187.5 5 45.98147 215.01 5
100 4250 5 45.98147 211.5 5
100 4281.25 5 45.98147 207.89 5
100 4406.25 5 45.98147 213.77 5
100 4500 5 45.98147 213.77 4
100 4562.5 5 49.7097 213.87 4
100 4625 5 49.7097 213.87 4
100 4718.75 5 49.7097 213.77 4
100 4812.5 7 49.7097 213.87 4
100 4875 7 49.7097 212.74 4
100 5000 7 55.92341 212.63 3
100 5062.5 7 55.92341 209.26 3
99.60784 5093.75 7 55.92341 209.11 3
99.60784 5156.25 7 55.92341 211.27 3
98.43137 5218.75 7 55.92341 209.99 3
98.03922 5312.5 8 60.89438 207.52 3
97.2549 5375 8 60.89438 207.44 2
97.2549 5500 8 60.89438 207.33 2
96.86275 5531.25 8 60.89438 207.33 2
96.47059 5562.5 9 60.89438 203.42 2
96.07843 5625 10 64.6226 202.61 2
96.07843 5718.75 10 64.6226 202.5 2
96.47059 5781.25 11 64.6226 203.79 1
94.90196 5937.5 12 64.6226 203.89 1
83.92157 5906.25 12 64.6226 202.77 1
84.70588 5968.75 12 64.6226 200.27 4
88.23529 6031.25 11 69.59357 195.66 4
89.41176 6125 11 69.59357 199.16 4
89.01961 6187.5 12 69.59357 199.16 4
89.41176 6218.75 12 69.59357 198.08 4
91.37255 6250 14 69.59357 194.49 4
91.76471 6312.5 14 73.3218 197 4
91.37255 6375 14 73.3218 193.43 4

 

That was my third gear log on 93 with a custom 94 tune. Kind of hard to read, but it's the best I could do. Basically instead of postin up more hard to read stuff, I did 4-5 pulls in many gears on my 94 blend and all of the knock went down considerably. The most I could get was 3 counts in one area a few 2's after heat soaking the **** out of the car. Are 2's and an occational 3 acceptable for a custom tune?

 

That's probably real knock at 3500 rpm where the knock sum goes from 1 -> 5. The latter part of your log looks mostly like real knock. Looks like 2 deg of timing is being pulled at that transition from 1 -> 5. Its not bad, but I'd either use better gas or tune it out.

Your load calc numbers aren't really that great. If you got that tune a few years ago, you may want to consider getting a retune. There's been quite a bit learned in the last year about how to make a safe yet powerful tune.

 

2-3 counts of knock is perfectly fine as long as your not pulling timing....whenever i get 2-3 counts of knock, i compare the the logged timing advance with the timing advance that are in the ecuflash maps and they are the same, therefore, i don't pull timing at 2-3 counts of knock....you should be fine

 

I dunno, maybe I am a tad bit on the conservative side, but his log show that he is showing very consistent knock, and therefore I would want to tune it out.

The fact that it stays there is enough to cause me to be at least a little concerned. If it was just across a few hundred RPM, then it would be a different story.. his goes from 2,400 to 6,300, which I would not find acceptable on my ride.. But, to each his own I guess...

 

Thanks for the responses. If you didn't read the whole the thread, the log I posted was on 93 octane. I was tuned on 94. So I'm sure it's a little off.

 

You need to fix your tune. Just pull 2 degrees of timing in the affected areas and more than likely your knock will go away. Running 7* of timing @ 3300 rpm is too high anyway.