kroy

Depends on what you use. Stuff like Race Gas is like 2oz per gallon to raise 4 octane numbers (40 octane).

slartibartfast

iTrader: (7)

Very confusing post. 4 octane is 4 octane. How do you get 40?

4doorfury

iTrader: (1)

Race fuel is not sold as an octane booster at your local auto parts store. The reason I suggested e85 is because it's equivalent to 116 octane gas roughly. If you put it in a fuel calculator you can see what it will raise your octane to. Should be close to like 95-96 and because it's alcohol it will cool your cylinders further decreasing knock chance. It will slightly lean your mix out but since the tuner added some fuel I would be willing to bet it's totally safe.

kroy

My local Z expert told me he trusted 3 brands to not damage. Torco, Race Gas and boostane. I think you can find torco pretty widely.

Isn't e85 flex fuel? Thought you needed to have conversion done to use it.

4doorfury

iTrader: (1)

A single gallon to a mostly full tank won't hurt anything. The conversion is so the ECU can monitor the blend and adjust fuel trims and tables properly. You are simply going to use it as a test to see if knock stops or not with one tank. We all run flex fuel daily, look and you will see it is rated at 10% ethanol typically. I ran a 40% mix in my old car for over a year with no issues at all and switched back to regular gas and ran it another year.

kroy

I know our fuel is technically flex but thought it wouldn't work if ratio was a lot different. Or it would damage engine somehow. This is just bro science in my head. Good to know I won't screw up my engine tho.

BTW what did that old 40% mix do to your car? Both maintenance wise and performance. Also a tiny bit curious about gas economy. What happens when you flex fuel a regular car?

4doorfury

iTrader: (1)

Economy goes way down. I went from 26mpg to 21ish on a 40% mix. It was a turbo car so gains are way higher than naturally aspirated. I was able to gain about 70whp just swapping to a 40% mix.

kroy

^ that makes me miss my old turbo cars so much.

21mpg ain't half bad.

My 335i with just tune was doing something like 18.6.

Slatey

iTrader: (1)

I've been hearing Torco a lot, I think that is my next stop.

I got mixed answers from the interwebs saying that it worked or it didn't, yada yada yada. My take away is that it did SOMETHING with a full tank of gas, so I figured double the concentration would help. Even ~96 octane should keep knocking to a minimum if there is knocking, right?

Noted

Slatey

iTrader: (1)

Another update.

Ran a set of logs with the mystery octane. According to my tuner, he said that the ignition correction did look better. So he thinks we are dealing with some real knock and pulled some timing across the map, up to 4 degrees. Since the AFR looks perfect, we are gonna see what that does.

Initial thoughts after driving for about 60 miles is I've only seen the CEL flash twice. I think we are close to the threshold, so I may have him add a degree or 2 back in with a hair more fuel and I think we will be on the money.

I do wonder how much power is left on the table v. the timing advanced maps. You could also make the argument that the engine constantly detecting knock and pulling timing hurts the power just as much, but 4 degrees of timing pulled from the initial map seems like a lot. IDK how far it was advanced to begin with though.

Ape Factory

iTrader: (3)

Toluene or Xylene works as well. I used to run that in my single turbo RX7 when I couldn't get race gas easily. You can find it in any paint store or home improvement store. It's carcinogenic on a massive level so handle with caution. Not really good for the air we breathe either but...

As for knock, you should be able to log and see if the car is pulling timing. If it is, you're encountering knock and running into the ECU's safety check. I'd rather have a safe tune day in, day out, with the best gas that's readily available everywhere.

It's not quite as hot in Kentucky (I went to school there) but I have two maps (well, actually four), one for temps below 95 degrees and one for temps above. We're supposed to hit 105 in a few days.

I'm amazed at how slow the car feels in 100 degree temps. If I'm out late, after the sun goes down, or first thing in the morning, even with temps in the mid 80's, the car is much faster, even on the hot weather map. And the ECU isn't pulling timing so I know I'm safe. Quite frankly, when it's that hot out, I rarely get on the gas anyway. Mileage is way up in hot temps. Less air in means less gas gets injected.

slartibartfast

iTrader: (7)

Neither Toluene or xylene are recognized as a carcinogen according to their MSDS sheets. It can still kill you if swim in them or chug a glass or two.

Xylene is the better of the two for octane equivalent. About 145 vs 124.

Ape Factory

iTrader: (3)

Both are aromatic hydrocarbons and what researchers say is there hasn't been enough data gathered to rule it out as a carcinogen. Both can be extremely hazardous to your health if you're not careful in how you handle them and both change your car's emissions composition and not to the betterment of clean air.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2996004/
https://www.osha.gov/SLTC/toluene/health_hazards.html

But they will raise your octane level considerably using the right ratio. Xylene I believe is 117 or 118 and Toluene is 114.

slartibartfast

iTrader: (7)

Neither toluene or xylene are KNOWN to cause cancer. Your citation says that, Material Safety Data Sheets say that. Not saying they can't but no one has documented it.

My octane equivalent numbers were from ASTM Research method, yours were Motor method. Pump octane equivalent number is 118 for toluene, xylene is about 130. When discussing fuel octane, we normally use pump octane number which is average of Research and Motor methods. I say "about" for xylene because it has three isomers which each have different octane equivalent values.

Ape Factory

iTrader: (3)

It was off the top of my head and I think I was quoting the (R+M)/2 rating.

My point is be careful handling it. You're obviously in the petrochemical industry as was my father who was a chemical engineer and ran the chemical division of a major international conglomerate. He cautioned me about exposure to both and to take proper precautions. Just a fair warning, be smart when dealing with both or any aromatic.