Kevinmacd

I disagree, when in stock form they are pushing to get the most out using a designated octane, hence the reason when buying a tune they ask you 91 or 93!

Oak

well we can agree to disagree, sure it's not ideal, imho, but I wouldn't be overly concerned if your just piddling around on the street in normal traffic. like I said, if your going to drive aggressively or on track it's always a good idea to use a mix of 100 oct even if your on 91 or 93. I always do 50/50 blend.

go to 6speed and ask the tuning guys there. even with a stock tune your car will perform noticeably better on the track. albeit if your ecu has have time to adapt to an aggressive driving style. it takes time to adapt.

champignon

Why don't YOU give it a rest?

When you sent me the first PM you sent me weeks ago, I imagined that you might be someone interesting to meet if the opportunity presented itself. I was mistaken.

I don't find you sufficiently interesting to pay much interest to your posts. Why you find me that interesting, so interesting as to comment on about 1/3 of my posts, is a bit of a mystery.

champignon

My guess, and all it is is a guess, is that there is enough variation in gasoline from state to state and pump to pump, that the difference in these two octane levels isn't very great. 91 Octane gas in California has a really bad reputation, presumably because the formulations, due to emissions rules restrict it to being less than it should be.

I'm going to do some datalogged pulls in 3rd gear, first on 91, then with enough Torco Octane boost added to presumably raise it up to 93. I'll also be looking at how the car performs. After that, I will see if I can make an educated decision on whether to flash back to stock, buy a 91 tune, or leave it as is.

6spO has a number of threads on what to datalog with a Durametric. Are there any key data items to log that you think would specifically point to knocking vs. not knocking? Thanks.

T10Chris

Actual timing advance
individual cylinder knocksums (this may not be a reading that is available to monitor in durametric, I don't recall)

I look at those when checking for knock. I'll hook my durametric sometime this weekend and see what parameters are visible if no one else chimes in with things for you to check on.

The thing is with monitoring knock- stock tune, even on 93 oct, there are always going to be some knocksums present.. It's when they occur and frequency and how bad it is that you have to worry. The ecu adapts pretty aggressively to octane and quickly dials back as well.

Even if you aren't getting knock, once you feel the difference with higher octane you may not want to switch back.

I notice you mention using Torco. One full bottle of Torco to a tank of 91 would get you in a good place, probably around 94 octane. You may notice an orange/rust colored residue on your exhaust tips/plugs when running Torco, which is normal.. It is due to the manganese content in the octane booster. Basically instead of black soot, you'll have orange/black soot. Freaks some people out, but it is normal/safe.

champignon

I picked Torco because it was one of 2 or 3 of these products that seem to actually elevate measurable octane. According to the scale on their website, increasing the octane by 2, from 91 to 93, 0n the 16.6 gallon capacity tank in our cars, would take roughly 13.5 oz, which is well less than half a can. Given the cost, I was planning to use that dilution.

http://torcoracefuel.net/pro-accelerator.html

Of course, what they have on their website may be unduly optimistic :-)

I could have done some of this testing today, however the roads are so clogged with 4th of July traffic that I've decided to wait until the middle of next week when I return from a short out of town trip.

champignon

This is sort of an update, if you want to call it that :-)

I read a number of threads on data logging with the Durametric, mostly on 6spO, and proceeded to do a bunch of 2000 rpm to redline runs with the car running on 91 octane "premium" gas as available where I live. I then refilled the car and introduced enough "Torco Accelerator" into the tank to get the octane up from 91 to 93. I spent a lot of time reading on the various supposed octane-boosting additives, and concluded that about 3 of them appear to work and have been verified to do so (Torco, Lucas, and I forget the 3rd one). Torco appeared to have the best ratings of the 3 products, but is also the most expensive.

I then datalogged the car again with the same protocol.

I then looked at the data, which in reality was a bunch of un-interpretable nonsense. If you really want to make your head spin, just go read threads on this topic, data logging your car to look for signs of knocking, detonation, whatever you want to call it. The people posting on the threads appear to be very impressed with what they have to offer and what they have read on the thread, but the more you read the threads and try to add 2+2 and get 4, you realize that you can't :-) There must be someone out there who understands this stuff, but certainly the overwhelming majority of people posting on those data logging threads have absolutely no understanding of the topic. I don't understand the topic, but at least I acknowledge that fact.

Anyway, I really have not noticed any difference in how the car performs on the 91 octane gas I was using, and the 91 octane gas with enough Torco accelerator added to it to supposedly bump the octane up to 93. However, all of this is subjective, and I'm a very skeptical person by nature, so maybe the effect really is obvious and I'm just not willing to accept it? Who knows?

I have done the math and with the amount of miles I am likely to put on the car (perhaps 2500 per year), it will take something like 8 years to amortize a $500 re-tuning of my car to 91 Octane gas, producing supposedly lower performance, than if I just put the Torco stuff in there and leave things as is. I've decided to do this, for now. I've also decided to stop data logging these sorts of runs because it is not a benign, risk-free activity and can be very frustrating. One of my runs, merging onto an onramp on the freeway, had a school bus way in front of me who decided to either stop accelerating or just put the damn thing in neutral, and I came up on him like a rocket even though he must have been 1/2 mile in front of me, then he very slowly pulled off the road onto the side. No signals, nothing, just he drove like that. There are so many unpredictable things that happen on public roads that I'd really rather not do this if it can be avoided.

So, I'm going the Torco route, at least for now.

T10Chris

If you want, post up your data logs. I know what Im looking at and will tell you if there is any difference.

dprantl

If you were logging the right parameters and you made enough proper runs, it should be easy to tell if raising your fuel octane had an effect on the running characteristics of your engine. Post your logs here.

Dan

champignon

Howdy Chris and Dan,

Would you please tell me what parameters you would want to see on such datalogs? I logged the things that were mentioned in the threads I read on 6spO, however other threads I read later mentioned other things. So I can't be sure I logged the right things, because I was following the directions given by people who I don't think really understood what it was important to look for. I got both of the Lambdas, the engine load, one of Mass Oxygen readings, and I forget what else. Likely I didn't get everything that would be necessary.

What would be on your lists to log?

Thanks.

ANJ-911

It's been a while since I've datalogged a car, but I believe the main thing you want to look at when comparing the performance with the two octanes is the timing retard that the computer is applying with one octane vs. the other. Hypothetically speaking, if your tune is mapped to have a 10 degree timing advancement at a certain RPM/load condition but it notices some knock and has to pull back to 6 degrees, your timing retard is 4 degrees ie. your engine is pulling 4 degrees of timing from what it would like to have to perform ideally. So yea your ECU can adjust for the lower octane but ideally your ECU wouldn't be retarding at all if you had high quality fuel, but I believe a few degrees is fine. The issue is that with low octane fuel, your ecu will err on the conservative side and pull more timing than it really needs to and you'll therefore be creating less power than you should, and if you're at the extreme end of the retarding range, you're ECU may not be able to pull as much timing as it needs to eliminate the knock. I'm not sure which parameters you need to set to log this on a durametric though since I've never used one, I'm sure others will chime in.

Edit: Another thought I wanted to add is that whether running 91 octane with your 93 octane tune is OK will depend on how "aggressive" the tune is. If it's an off the shelf tune it likely isn't as aggressive as a custom tune for max performance on 93 octane would be. What I mean by aggressive is the tuner pumping out as much power out of that specific octane fuel as they can. Generally speaking an off the shelf tune will be less aggressive and you may have more head room to run 91 octane long term. My previous car, a b5 s4 which is also a 6-cylinder twin turbo that had upgraded larger turbo's on, had a custom 93 octane dyno tune. When I relocated to a 91 octane area for a 12 months work stint I was able to "adjust" the timing back a few degrees without getting a fully new tune. Later when I almost moved to California, the tuner (EPL) highly suggested that I have the car re-tuned to either their 91 octane off the shelf tune or do a 91 octane custom tune for the long term health of the car, and due to the fact that 91 octane CA gas is especially crappy. Maybe it's worth reaching out to sorftronic to see what their thoughts are?

T10Chris

For the purposes of comparing timing, you'd look at "actual ignition angle" between your pulls and compare the 2. Any variation would indicate 1) timing pull OR 2) ecu's adaptive programming advancing timing because it is not seeing any reason to pull it back.

I don't recall if durametric has knocksums per cylinder or knock sensor output as an available monitor. Comparing the actual ignition angle with the knocksums is how to differentiate between adaptive programming timing advance, and timing retard due to knock sensor activity. Your ignition angle should function roughly inverse to your torque curve. At peak torque, ignition angle should be lowest and it should increase as rpm climbs.

With durametric, I didn't log many things due to the limitations in sample rate. For basic logging, I would use time, rpm, speed, boost pressure of sensor, oxygen sensing bank 1 lambda value, oxygen sensing bank 2 lambda value, injection time and ignition angle. Using those outputs you can calculate boost in bar/psi/etc, your AFR, your injector duty cycle, plot your ignition angle and just get a general idea of acceleration time in gear to compare if changes made any difference in acceleration.

champignon

Thanks very much, Chris. I did not log Ignition Angle, but I got the rest of them. Would those logs be at all interpretable? I could attach some as Excel or PDF Files. The PDFs cut off some values and the headings are hard to follow.

I could try logging again, but right now I have a nearly full tank of 93 (Torco Augmented) gas in the car. I won't be able to drive the car to where I'll be working most of the next 2 weeks, because the employees will conclude that the owners are making too much money off of them, which is not actually true, if I show up in a Porsche with a big fin, albeit an old one :-)

champignon

Howdy,

Reaching out to Softronic results in an immediate request for $500 for "retuning" to 91 Octane, conditioned with a warning that the engine might be damaged if the $500 are not coughed up before the owner's bar tab becomes due :-)

I don't know how specific the Softronic Tune is to any specific vehicle. Obviously, they want you to think the tune is customized to you and your vehicle, however I'm not great at reading binary code, so it is something one has to take on FAITH.

When I went to test drive the car, the owner/seller drove it like a bat out of hell on city streets in the S. Bay of Los Angeles. I certainly didn't notice any knock or hesitation in the car, either when he drove it on crappy CA 91 or I did the same on my way out of town (although rolling along at 17 mph, tops, on the 405 Freeway may not exactly stress the engine or the tune). I did then drive multi-hundred more high speed miles in California, however it was all at elevations at 4 or 5000 ft. or higher. I didn't notice the octane level of the gas being sold in Nevada or Oregon, but I did buy the highest grade they had for sale, almost all of it, Chevron.

My carrying cost for this car is probably going to be less than $1500/year, including insurance, but not counting any major repairs that could come up. Since the last two owners, over a span of 11500 miles and 2.5 years, expended about $25,000 on the car, including 2 engine drops, with nearly everything that breaks having been replaced, I'm assuming that there are no major repair bills in the immediate future, unless I lose an engine that is, on account of the tune and the gas :-) If I just pour $60 or $70 worth of Torco into the gas tank every year, I end up with a powerful car and no need to do an ECU flash, which in some cases can be risky.

Thanks very much for your comments!

T10Chris

Might be able to tell some differences from extrapolating data, depends on what parameters you have available to look at. Might not be able to tell anything.

If you want to post up excel files of the logs I'll give them a look over this weekend and see if anything jumps out if you'd like.