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Discussion Starter #1
Who is running 87 octane in their Treg?
Just put some in to see if/how much the ECU is reducing timing advance, and if there is a resulting noticeable power loss.
(see some info on the subject in July Car and Driver also).

Mine is 2004 with the 4.2 V8.
 

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You clearly like your cars so why mistreat the V8?
 

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Discussion Starter #3
You clearly like your cars so why mistreat the V8?
Any FACTS to back up your 'mistreat' assumption? Or just based on 'guts feeling'?
 

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Discussion Starter #5
Fact.......
And?
That confirms that the Treg V8 ECU - like all (?) modern engines - is able to adjust the ignition timing using sensor inputs (here: knock sensors).

What do you assume is the effect of 87 octane?

If i find the time, i will check for a logging template, or make one and log on current 87 octane. Will log again when tank is empty so I can compare the 93 log under as close as possible conditions (mainly air temperature). Since misfire counter is still at zero (on likely old coils and plugs; no documentation from previous owners available, and I haven't changed them yet), likely zero effect on mpg or performance.
 

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I think using “Top Tier” gasoline is what is really important. Timing advance will be limited to the octane used, thus reduced upper rpm performance. Steady state drivability should not be majorly affected if it is anything like my GTI Autobahn that has premium fuel as an option. But it does perform better when on 91. The Touareg may be different.
 

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There is a huge difference in mpg with my 2006 V8 AXQ engine. I have documented every tank of gas since new. Date, Mileage, # gallons added. Gas type and octane.

I have tried everything in the AXQ, except for diesel! I even got to run ethanol free in that engine for the first few years.

At this point, I have gave into the demands of the engine and run 93 ethanol. While it will function on 87 ethanol, it keeps activating the anti-knock sensors. I end up with an engine that does not run as well and which gets less mpg at the same time.

Note that I do NOT live in flat area. One of the easiest ways for me to tell is just to take a drive with cruise on. 93 octane on one my my regular drives give me almost zero upshifts on hills. If I switch to midgrade, I get constant upshifts on steep hills. If I go to 87, it upshifts like crazy, often going into upshifts and then shifting back, then upshifting again on moderate hills. The constant upshifting is a real PITA and reminds me of some of GM's better automotive efforts. Argh!

If you live in a flat area, you might not notice these problems.

The ethanol 93 is my new baseline, since ethanol 93 is the best I can get. I lose MPG when I go to midgrade ethanol. I lose even more MPG when I go to 87 ethanol.

Ethanol 93 seems to run about as good as pure mid grade (which I can not source. Only non ethanol in my area is 87 octane). 87 ethanol free runs close to mid grade ethanol which is Yuk!

Now, whatever pure gas we are saving from adding 10% ethanol to gas has to be computed against the 12% mpg loss that I am seeing. Are we even saving anything? I don't know. I end up buying more gas each year to offset my 12% MPG loss.

TLDR: If you live in flat Kansas, you might not notice a difference. If you live around any hills, you WILL notice a difference.
 

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And?
That confirms that the Treg V8 ECU - like all (?) modern engines - is able to adjust the ignition timing using sensor inputs (here: knock sensors).

What do you assume is the effect of 87 octane?
Actually that only confirms that you are not following he recommended fuel grade determined\specified by people who probably have more relevant credentials than you on this subject .....

I don't care what octane you use... you can piss into your tank for all I care.
You're already talking about logs, knock, etc. so clearly you are under the impression that you either don't need optimal engine performance......

Why stop at running lower grade fuel? Have you considered pulling some connectors to induce a CEL and maybe LIMP mode.... image how much better you could make your engine run under those conditions.
 

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I have found through the many years I have of owning VW's is to follow the recommendations, they run the way they are designed to longer with less problems !
 

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Timing advance will be limited to the octane used, thus reduced upper rpm performance. Steady state drivability should not be majorly affected
^^That is a most concise statement of what I actually observe in my engine. Bravo Sir. :wink2:
 

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I've used it the last couple of fill ups and while the mileage has remained the same there slightly less punch. I'll probably try 89 next fill up.
 

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Discussion Starter #12
I first quick log run on 87 octane and 90 degree: as expected, the ECU reduces timing advance under WOT and higher RPM.
In long (high gear) low rpm (2000-3500 rpm) WOT grunts, I see up to 3 degree pull. Ditto during long (high gear) high rpm runs, up to 6 degrees (once) pull (4500 to 5000) rpm.
No cel.

I will keep running this tank of 87, and do a better log (full WOT in gear sweeps from low rpm to fuel cutoff) at the end.
Then repeat with 93.
I don't think 89 will be substantially different from 87 (obviously somewhat less timing pull/slightly more top end power); we don't have much 91 here.

But it is already pretty clear to me: for puttering around (highway, around town, etc), I will run 87 ($0.60 less than 93) to lower my fuel bill by about 20%.
For heavy towing (or recetrack, or mountain climbing), I will feed 93 octane.
 

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Don't discount preignition. That can cause moving parts inside your engine to break--and you're counting on knock sensors and otherwise good engine management to mitigate that. Risk vs. reward.
 

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Discussion Starter #14
Don't discount preignition. That can cause moving parts inside your engine to break--and you're counting on knock sensors and otherwise good engine management to mitigate that. Risk vs. reward.
That is certainly true.
And I would NOT make this recommendation for the novice/unexperienced and without the ability to monitor (log) what is going on in your engine.

Similar to performance tuning (increase boost and timing advance for a given octane, typically 93). If tuned for 93 (and zero to 3 degree timing pull), you can run into additional timing pull on hot days, or poor gas.

Would be interesting to see timing pull on lowest recommended fuel grade at 15,000 ft and 100 degree F (anybody in South America to log one of those magnificent mountain roads?). Or at least
Mount Evans Scenic Byway (14,000ft, but not warm enough; may need to take cold air snout off:wink2:). I have no idea how 'thin air' effects ignition timing though.
 

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I don't understand what you are trying to prove.
Can you run on crappy fuel.... sure, if you have to. The electronic nannies are there to stop you from hurting things just because you think you're a tuner or something...... in order for knock sensors or any other nanny to step in, they need to detect those dangerous conditions first.... so you're still doing harm....
Running lower quality fuel, and having the nannies pull timing, etc. will cause hotter running conditions on top of everything... you're creating hot spots, accelerating wear, etc.... all just because you can.

Your fuel cost savings won't add up to anything once you start having to replace all the other components you're damaging. Hopefully you are also doing all this on a higher milage unit that someone before you neglected previously so that you can really cause yourself some headaches with all this clowning around.

Can't wait to hear what you plan on doing at the "racetrack"..... with a Touareg...... maybe you can race a Prius or something....
 

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A little digression/hijacking here since it is about octane rating:
I used to run RON 95 on my 2004 V6. I know about the degraded perf thing. I run RON 98 on my daily driver, and Audi.
I have two still unresolved issues:
1. Running rich on normal driving, even 20km drive => not related to octane stuff.
2. Marbles rolling in a can when I floor it and try to race the prius :) Marbles stop rolling at around 4500 rpm.
I changed to RON98 to see if the rolling marbles issue is not just the knock sensors or the nannies as TurboABA call them are trying to do their job and I still hear the marbles rolling. My timing is still within spec, checked with vcds even if the timing check procedure is still not accurate according to the internet. I even put in a new tensioner.
So at least I know that putting in RON98 is still causing the rolling marbles. I'm now leaning towards the variable intake valve making that noise. I filmed the arm movement and it changes position around 4200. maybe the normal position (from idle up to 4200rm => arm pulled down) has more play and the vibration is causing this noise. I'm putting in the gruvenparts bushings soon to see.
Maybe the previous owner(s) ran only RON95 and has induced this rolling marbles pinging issue, maybe not. Maybe my chain is on the way out (137.000km). Maybe the knock sensors are on the way out. I'll go on with RON98, upgrade the variable intake rod bushing and see what happens.
 

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If you think it's knock you're hearing, check your timing logs to see if there's pull happening. Also, make sure you run the correct copper plugs with the correct heat range. Once you start running crappy fuel, leaning out or fouling plugs due to whatever, you need to freshen up the plugs and start experimenting with the gap and heat range... Don't run platinum plugs as they are for lazy People who want to not look at them for 60k+.... Not for those who want a properly performing engine.

Have you considered running seafoam though it? Carbon buildup will cause hot spots and sometimes induce problems like you're describing, etc.
 

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Discussion Starter #20
Marbles stop rolling at around 4500 rpm.
Log your cam position, knock sensor voltage and timing pull (VAGcom).
Not sure how VVT works on the V8 (I am used to 22 degrees intake cam at 4200 rpm).

What do you mean by "if the timing check procedure is still not accurate according to the internet."?
 
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