I think you are correct. If you want a better octane booster, put a gallon of xylene in a gas tank that is about 5/8ths full of 91 octane fuel. If your car is GM Stage 3, it will feel much faster. You may be able to get away with adding less xylene, or having more fuel in your tank, but I haven't tried that yet.

 

Well, I didn't have time to put my logs into an excel file (I wanted to show a graphical representation), but here they are straight from my log book.

Note: This is while running CAM2 (Sunoco 260GT100) in high octane mode (GMR Stage 3) WOT (1st - 3rd gear).

1st Gear:

Timing RPM
21.5 5769
23.0 6128
26.5 6168

2nd Gear:

Timing RPM
27.0 4130
26.5 4148
27.5 4280
27.5 4443
28.0 4607
28.0 4746
28.0 4896
28.5 5067
27.5 5208
27.0 5359
28.5 5515
28.5 5648
29.0 5805
29.0 5952
29.0 6068
28.5 6209
27.0 6356
28.5 6488
27.0 6625
26.0 6744
26.0 6868
26.5 7023

3rd Gear:

Timing RPM
28.0 4947
28.0 5013
27.5 5067
27.5 5137
27.5 5208
27.0 5252
27.5 5312
27.0 5388
28.5 5450
28.0 5498
28.5 5564
28.5 5631
28.5 5682
28.5 5734
28.5 5805
28.5 5859
28.5 5915
28.5 5952
28.0 6029
28.5 6068
28.0 6147
27.5 6168
27.5 6250
27.5 6292
27.0 6356
26.0 6400
27.5 6443
27.5 6488
26.5 6533
26.5 6602
26.0 6649
25.5 6697
24.5 6769
25.0 6818
25.0 6843
25.0 6918
25.5 6944
25.5 6996
23.5 7023
23.5 7049
23.5 7130

 

Here is the graph from your data:

 

Thanks man

 

Why the dip in timing between 5,000 and 5,500? Not so interested in third because of the first sample occurring at 4945 and it may be affected by the shift but it does a similar thing in second.
Is it pulling timing there or is that what is commanded by the PCM.

 

It's what is commanded by the PCM.

I have no trace of knock during any of my pulls.

I've repeated the pulls over and over again, with very similar results.

I feel the graph slightly exaggerates the timing fluctuations due to how it was setup.

Also, my shift from 1st-2nd could have affected the results due to my traction issues when I enter 2nd gear.

My 1st gear data is funny. 1st gear is so short, and ends so fast the interceptor did not record all of the data. I forget what I have my data rate set at, but I know it is one of the faster settings.

 

interesting

 

Do you have similar data for 93 octane and 91 octane? I would love to see those as a comparison.

 

I only run 93 octane or 100 octane

I do have timing data for my 93 octane runs though.

I'll post it for you later.

 

Would you make an exception to run a small amount of 91 octane for a few pulls on an almost empty tank? It would really help us to explain to others (and ourselves) what is going on with the timing on these different octane fuels. I'm almost begging you.

 

lol...hurt motor with kr

 

That's because the SS/SC has the slower obdii port. The newer can-bus can do everything in real time. I think the older style is the PT gauges and the new are CN.

 

You could always get a small 5 gallon drum of VP100 or Motorsport 109 and mix it down to a 93 octane with your 91 so you get more and can see if you think it is worth the extra $$. But it would only make sense if you have an HP tuner so you can mod your tune for a tank or however much it would make to give you an idea.

 

Sorry man.... she is tucked away for the winter.

I will post the 93 octane logs this weekend, I do not feel comfortable running 91 octane.

The default GMR S3 tune commands some pretty aggressive timing for pump gas (max of 23*).

Yep. SS/SC's have the PT gauges.

 

so that's why the lnf logs are always so rough/jagged looking compared to the lsj

 

Just got a question, so you guys are using a GMS3 tune or a GMS3 PCM? Wondering if your AC turns off if using the GMS3 PCM. I think that's what I have read.

 

you can get the trifecta version which reenables the ac

 

Ahh, I see. Thanks for the info man!

 

https://www.cobaltss.net/forums/2-0l...-3-faq-214518/

 

I am running the GMR Stage 3 PCM from GM.

I had Vince at Trifecta upload the GMR Stage 3 tune w/ A/C unlocked (was sick of sweating to death in the summer).

Both tunes are the same unless you request other wise.

 

Can I switched to a Stage 3 PCM (trifecta tune) with my current mods? Mods are on my sig.

 

Absolutely! I have almost the same mods and I have the GM Stage 3.

 

This.

 

By any chance, can I put the GM Stage 3 (trifecta) tune on a GM Stage 2 PCM? Just wondering about it. Not sure if both PCM's use the same circuit architecture.

 

you can get it loaded on any lsj pcm