100+ octane fuel, review

[4-tified]

Last week I was down to about 1 gallon of 93 octane. One of the gas stations I use started selling "race fuel" again. They sold it a couple of years back, but then stopped until recently.

The octane rating was not listed, but "for off-road use only" was marked on the pump. Also, you can't use a credit/debit card on it, you gotta pay first.
So, I went inside and asked the cashier how much the race fuel is.
It's $6.49/gallon. I asked if she knew the octane and she replied, "I think it's 105 or 106." Well, I can't verify that, but it seems like an odd number.
At least it's 100 or over cuase last time they sold "race fuel" it was listed as "100 octane".

93 was selling for $4.25 so I figured I'd go ahead and splurge and try out the race fuel just to see what would happen with APR 93 software. I don't have the 100 program, but I was curious to see if having a higher octane fuel would better allow the 93 software to fully maximize itself, and if I could actually detect something. It did, and I did.

I wanted to let the last of the current fuel in the lines work it's way out so I made no assessment for the first 25 miles, as I average about 22-24mpg.
Soon after that I noticed a MUCH smoother engine, especially when in high boost mode at mid to full throttle. I was quite surprised how strong the engine felt, and especially how SMOOTH the power felt across the rev band. It was noticeable improved over any 93 octane I had used be it from Shell, Amoco, BP, Speedway, etc...

I wouldn't say that there was any "more" power, but what was there and felt was maximized performance as the power band felt incredibly smooth and FULL. It's an eye opener and it made start to question what the "problem" could be with using regular 93 with 93 software.
With regular 93 and 93 software the power is definitely better than stock.
Still, at times the power feels uneven. Sometimes the power feels strong and linear and other times it's strong but uneven, and at approaching high rpm it feels flat. The race fuel felt smooth and strong all over, especially mid-rpm part throttle was very strong and smooth.
The 93 software could be asking for too much boost resulting in knock in certain conditions. It works well in general, but using the 100+ octane made a big difference showing that an erratic power feel, with slight on/off power, may not be due to fuel pump problems. With the race fuel there was never a feeling that there wasn't enough fuel resulting in lean running with likely detonation knock events pulling timing.

I'm starting now to wonder if the knock sensors in these cars may be a bit sensitive, or if the 93 program is asking/giving too much boost, and along with variable and questionable 93 fuel all combine to make for a not so linear power band. I've had turbo engines in the past and I'm familiar with increasing boost and the resulting fuel cut and knock sensor timing retard that can pull power and make for non linear and even erratic power delivery. Fuel cut can be very dramatic. But, my A4 doesn't have fuel cut.
It just feels like power fluctuates from time to time more like knock with subsequent timing retard. The higher octane fuel is allowing the software to reach it's full potential without the resulting knock pulling timing, thus allowing the engine to produce it's full power along the whole rev band.

I wonder if anyone has graphed knock events with their stock, APR/Revo, and high octane programs? Also, I wonder how much lack of "headroom" is tuned into our knock sensors to err on the side of caution, and can the knock sensor be "tuned" by the software to alter when it triggers a signal, or alter the ECU programming to allow for higher level of knock signal before intervening?

As another quite noticeable benefit, my MPG INCREASED by at least
2/2.5 mpg and a bit better on longer steady highway runs. A good indication that the engine was running at a greater efficiency.

I'm now back to the typical 92/93 fuel and the previous "performance" has returned. I already miss the race fuel.
The one odd thing is that back when gas was like $2.50 per gallon, this station was selling race fuel at about $5.50 per gallon.
Now, high octane gas is selling for $4.25 and race gas is "only" $6.49 per gallon. Race octane is now a better buy than before the prices went through the roof, and I get BETTER mpg.

At 22mpg average with 92/92 octane, with 10 gallons I get 220 miles.
10 gallons X $4.25 per gallon= $42.50
The race gas gives me about 24.5mpg. To go 220 miles I would need
about 9 gallons of race fuel, at $6.49 per gallon= $58.41
So, it still costs about $16 more for the race gas vs 93 for 10 gallons.
That would be about $24 more per tank.
You get a bit better mpg with the race fuel, but at about $2.25 more per gallon, it doesn't pay. I wouldn't say it's worth it for day to day driving.
But, if you're planning a trip to the track-road or 1/4 mile, or a cool driving trip, I think the race fuel would be fun to use.

BTW, I didn't try the race fuel with the stock programming. It just occurred to me to try that, but I didn't. I'll try the race fuel again and I'll try 5 gallons with the stock software just to see what happens.

Overall: TRY SOME!
Post what you feel in performance change, if anything.

[bhvrdr]

The knock retard on my APR 93 program was about 6 degrees or less. This is what APR specs so I wouldnt be too worried it has anyting to do with that. For reference, there is a company out there that has no problem with cars retarding 10 to 12 degrees due to knock. Six degrees seems to be a generally accepted conservative number.

Did you make sure it wasnt leaded race fuel BTW?

If you want to get a program that will take full advantage of race fuel, many companies allow this. It will allow for more timing advance. You can't really "tune" the knock sensors. Their job is just to detect knock. You either add or remove timing. The knock sensors will do their job of monitoring the changes you made and the computer's IKC (ignition knock control) programming will safely retard in the summer months as long as your car is not overtimed or has a mechanical problem.

cheers! Mike

[chrislane31]

I run 100 every few months, but are you sure that it was unleaded?

[4-tified]

I run 100 every few months, but are you sure that it was unleaded?

Yes.
Well...at least they said it was.
I thought I saw a sticker, but now I'm questioning myself...hmmm?
I just them called and they said unleaded, but then...

[M Style S]

Fuck...I wish i could find some 100+ around here or even 93...

[4-tified]

If you want to get a program that will take full advantage of race fuel, many companies allow this. It will allow for more timing advance. You can't really "tune" the knock sensors. Their job is just to detect knock. You either add or remove timing. The knock sensors will do their job of monitoring the changes you made and the computer's IKC (ignition knock control) programming will safely retard in the summer months as long as your car is not overtimed or has a mechanical problem.

cheers! Mike

Knock sensors work when certain frequencies are detected. It's a type of sonic sensor. Knock tends to create certain frequencies that the sensor can detect. As with any sensor it's sensitivity can be adjusted, given that the sensor is designed that way. Also, the sensor might be able to be adjusted to detect not just the frequency but also the sound
amplitude level (db), that could result in sending variant signal info to the ECU. The ECU can also then be tuned to interpret the severity of the knock event in order to decide how much retard should be tried, and/or if it should be applied at all.

What you're indicating is that the system is still the old style of of knock is on or off, just send the same signal no matter the severity or duration.
My point/question is how much added benefit might be gained by having a more tunable knock detection circuit, if any.
With the higher octane fuel the knock threshold is higher and the 2.0T with APR93 really loved having a higher threshold to work with as it was butter smooth.

BTW, I don't know why you wrote "in the summer months"?
Knock can occur even in winter depending on all the variables that can lead to knock including internal engine operating temperature, load, and variant fuel quality. Generally speaking, in cooler weather the engine heat is more readily removed so there is less chance for detonation to occur, but it can still happen in the colder and winter weather.

I'm sure the circuit isn't programmed to come on starting June 20/21.
I know you didn't mean that. I'm just teasing.

[Josh_877]

i have apr 93 and 100. i usually run 93 and once i tried 100 (with the 100 program) and yes theres a difference. i noticed that i got A LOT of fuel cut. but i could still feel a pretty big difference, not like stock to 93 but still quite a difference.

[bhvrdr]

Knock sensors work when certain frequencies are detected. It's a type of sonic sensor. Knock tends to create certain frequencies that the sensor can detect. As with any sensor it's sensitivity can be adjusted, given that the sensor is designed that way. Also, the sensor might be able to be adjusted to detect not just the frequency but also the sound
amplitude level (db), that could result in sending variant signal info to the ECU. The ECU can also then be tuned to interpret the severity of the knock event in order to decide how much retard should be tried, and/or if it should be applied at all.

What you're indicating is that the system is still the old style of of knock is on or off, just send the same signal no matter the severity or duration.
My point/question is how much added benefit might be gained by having a more tunable knock detection circuit, if any.
With the higher octane fuel the knock threshold is higher and the 2.0T with APR93 really loved having a higher threshold to work with as it was butter smooth.

BTW, I don't know why you wrote "in the summer months"?
Knock can occur even in winter depending on all the variables that can lead to knock including internal engine operating temperature, load, and variant fuel quality. Generally speaking, in cooler weather the engine heat is more readily removed so there is less chance for detonation to occur, but it can still happen in the colder and winter weather.

I'm sure the circuit isn't programmed to come on starting June 20/21.
I know you didn't mean that. I'm just teasing.

What I'm saying is that the knock sensors themselves are not in need of "tuning". Our IKC is an extremely sophisticated system. We have the knock sensors which simply have to do their job of picking up the knock. The computer can then sense these voltage levels and can detect the true knock from background noise using a reference signal. You would not want to alter that. The IKC system will then retard timing based on knock detected. We can do this for each cylinder individually. I'm not sure what your hoping for beyond that. To take full advantage of race fuel you'd simply want to tune in for more timing and the IKC will retard timing just as it always does. Additionally we have an overall timing value that depends on not just ignition retard but also multiple 3D maps that are based off of such variables as engine speed and load, coolant temps, and on and on. Thats seperate from the IKC functions though. There is no need to mess with the knock sensors though. The 100 octane programs from tuners do things the correct way by keeping all factory safeguards in place and tuning for their preferred increase in timing and any ancilary adjustments to boost and afr to take advantage of the added octane.

[slingblade]

....

Did you make sure it wasnt leaded race fuel BTW?
...

I'd also be concerned about this. There is no reason to list unleaded fuel as 'off road use only'

What brand was it? Saw this online:
Sunoco: http://www.racegas.com/
VP: http://www.vpracingfuels.com/
Turbo Blue: http://www.turboblue.com/

GAS
Sunoco GT100 Unleaded : 100 Octane : MON=95, RON=105, (R+M)/2=100 octane
CAM2 is GT100 (link)
Sunoco GTPlus Unleaded : 104 Octane : MON=99, RON=109, (R+M)/2=104 octane
VP Performance Unleaded : 100 Octane : (R+M)/2=100 octane
VP Motorsport 103 : 103 Octane : MON=99, RON=107, (R+M)/2=103 octane
VP Motorsport 109 : 105 octane : MON=101, RON=109, (R+M)/2=105 octane
Turbo Blue Unleaded : 100 Octane : MON=95, RON=105, (R+M)/2=100 octane

[RedS-line]

no surprise that you got better gas mileage. try putting 89 in your tank and i am sure your mileage will go down. sometimes i wonder if any inconsistencies i notice are due to the engine or the brand of fuel used. dont forget that audi recommends top tier gas.

[Unleaded20T]

I did try this "Race Fuel" once on a previous car that i had, and i had to replace a couple of broken valves. I did put some also on a 06 Z06 and the Check Engine light came on , so in conclusion I will NOT/NEVER try 100 oct fuel on my new a4.

[Phatt_Audi]

Fuck...I wish i could find some 100+ around here or even 93...

There's a 76 near the 110 entrance on Arroyo that sells racing fuel. 100 octane IIRC. It's not $6.49/gal though more like $7.50 or more.

[acidrome]

Fuck...I wish i could find some 100+ around here or even 93...

There is also a 76 in my town that sells 100+, im between Diamond Bar n Chino Hills if ur ever around the area.

[swoardrider]

Run it all the time with my 100 oct APR program on the track. Makes a pretty noticable difference when your already under powered.

[4-tified]

I'd also be concerned about this. There is no reason to list unleaded fuel as 'off road use only'

Actually, nearly all "race" fuels seem to be listed as "off road" use only, even when they are leaded or unleaded.

Leaded race fuel seems to be more common in places that carry more than one type of race fuel. This was a Gas City station, a big one that services truckers. They only carry 1 type of race fuel and it's carried only during the summer for what ever reason.
As I said, I called to double check and they said it was unleaded, but I can't verify it, yet.

If you can, please post. I definitely don't want leaded fuel in there.

[4-tified]

What I'm saying is that the knock sensors themselves are not in need of "tuning". Our IKC is an extremely sophisticated system. We have the knock sensors which simply have to do their job of picking up the knock. The computer can then sense these voltage levels and can detect the true knock from background noise using a reference signal. You would not want to alter that. The IKC system will then retard timing based on knock detected. We can do this for each cylinder individually. I'm not sure what your hoping for beyond that. To take full advantage of race fuel you'd simply want to tune in for more timing and the IKC will retard timing just as it always does. Additionally we have an overall timing value that depends on not just ignition retard but also multiple 3D maps that are based off of such variables as engine speed and load, coolant temps, and on and on. Thats seperate from the IKC functions though. There is no need to mess with the knock sensors though. The 100 octane programs from tuners do things the correct way by keeping all factory safeguards in place and tuning for their preferred increase in timing and any ancilary adjustments to boost and afr to take advantage of the added octane.

I think you missed my attempt at hoping to have a discussion on knock sensors and how they could work.
At one point carburators were seen as not needing to be messed with, or valve timing, etc... I was bringing up a point that knock sensors could also be a potential area for tuning as not all knock is the same. But, when you have a simple knock sensor that only detects one thing and one parameter of it, then it's a very simplified system, thus not allowing or having the ability to tune it. That does not mean it "can't" be done.

In the Mits Eclipse turbo there were knock sensors that were overly sensitive. Some were even detecting valve clatter due to poorly functioning hydraulic valve lash adjusters. I like to think that Audi is using better more finely tuned knock sensors, but that doesn't mean they are, nor does it mean that there can be faulty ones that are easily overly excited to trigger a signal to the ECU. That can cause erratic power delivery even when you are using the "correct" octane with the given octane program. If the sensor's trigger threshold is too low the ECU will think it needs to pull timing more than it should resulting in erratic power delivery.

My point is that by using a very high octane fuel my engines power was much smoother, and that means there is a reason for that.
Higher octane doesn't provide more power. So, something else is at play.
My speculation is that perhaps the knock sensor is overly active and even though I have a 93 octane program and am using 93 octane fuel, there might be knock events still occurring even when driving moderately.
In contrast, the higher octane is allowing full potential from the 93 program, where the higher octane fuel is keeping even minor knock from occurring. Well, in that case, the question of how well the knock sensor is working is certainly a good thing to discuss.

As I said, I was bringing it up for a discussion, not for lecture.

[4-tified]

no surprise that you got better gas mileage. try putting 89 in your tank and i am sure your mileage will go down. sometimes i wonder if any inconsistencies i notice are due to the engine or the brand of fuel used. dont forget that audi recommends top tier gas.

High octane fuel is not "top tier" gas.
Octane is merely a number to indicate the fuels formulation, specifically it's ability to not auto-ignite, or "explode" due to high temperature and/or
high pressure.

You could have a higher octane "premium" fuel that may not be as finely blended for proper burn and cleaning as a lower octane fuel, from a different refinery, that is.

"Premium" or "higher octane" is not any indication of fuel "quality", in regards to thinking one is "top tier" and the other isn't.

[bhvrdr]

I think you missed my attempt at hoping to have a discussion on knock sensors and how they could work.
At one point carburators were seen as not needing to be messed with, or valve timing, etc... I was bringing up a point that knock sensors could also be a potential area for tuning as not all knock is the same. But, when you have a simple knock sensor that only detects one thing and one parameter of it, then it's a very simplified system, thus not allowing or having the ability to tune it. That does not mean it "can't" be done.

In the Mits Eclipse turbo there were knock sensors that were overly sensitive. Some were even detecting valve clatter due to poorly functioning hydraulic valve lash adjusters. I like to think that Audi is using better more finely tuned knock sensors, but that doesn't mean they are, nor does it mean that there can be faulty ones that are easily overly excited to trigger a signal to the ECU. That can cause erratic power delivery even when you are using the "correct" octane with the given octane program. If the sensor's trigger threshold is too low the ECU will think it needs to pull timing more than it should resulting in erratic power delivery.

My point is that by using a very high octane fuel my engines power was much smoother, and that means there is a reason for that.
Higher octane doesn't provide more power. So, something else is at play.
My speculation is that perhaps the knock sensor is overly active and even though I have a 93 octane program and am using 93 octane fuel, there might be knock events still occurring even when driving moderately.
In contrast, the higher octane is allowing full potential from the 93 program, where the higher octane fuel is keeping even minor knock from occurring. Well, in that case, the question of how well the knock sensor is working is certainly a good thing to discuss.

As I said, I was bringing it up for a discussion, not for lecture.

I hear ya. It's a good discussion. Just pointing out that the knock sensors, assuming they are of operational quality, tend to work well or not. They're more of a sensor like an o2 sensor rather then a tunable part like a carburetor.

You can log the voltages and see a car that is more noisy such as a car with a single mass aluminum flywheel, semi-solid motor mounts, and a testpipe with full exhaust and the voltages will be very high but yet the IKC system may not be retarding a degree of timing. THis is because the ignition system knock control function (IKC) runs the engine at the knock limit for optimum efficiency, but prevents potentially damaging engine knock (pinking). The combustion process in all cylinders is monitored by means of knock sensors. The structure-borne noise signal detected by the sensors is compared with a reference level that is obtained for individual cylinders via a low-pass filter from previous combustion strokes. The reference level therefore represents background engine noise when the engine is running free of engine knock. The comparison analyzes how much louder current combustion is than the background level. Above a certain threshold, engine knock is assumed to occur. Both calculation of the reference level and detection of engine knock can take account of changes in operating conditions. The IKC function generates an ignition timing adjustment for each individual cylinder. This is taken into account when calculating the current ignition angle (ignition retard). When engine knock is detected, that ignition timing adjustment is increased by a specified amount. The ignition timing retard is then reduced in small increments if, over a spedified time period, engine knock does not occur.

It occurs so quickly even a vag-com tool in turbo mode cant really accurately depict this activity which is why the top level tuners actually develop their own diagnostics software prior to even attempting to develop tuning software (not all tuners have this sophisticated of equipment, however). Conversely you can have a car with a stock exhaust and a cushy ride such as an A6 2.7t that is tuned to all hell with overadvanced timing and it will show very low overall knock voltages but may pull back 12 or more degrees of timing. That is the IKC system doing it's job.

What I suspect may occur with folks trying out higher performance programs on the B7 is simply hitting the fuel limitations of this platform. The injectors are sitting at well over 100% of the specced window for injection with just a chip on the B7 and we all know the fuel pump is the primary limit prior to that. Maybe some tuners can chime in on this.

[Phrost]

I dumped 4 gallons of 109 octane into my car (running APR100) for a weekend, and it was great. I didn't run APR93 because I wanted it to adjust as soon as possible, but I noticed the same change in "engine smoothness".

Here's what I ran. Came in a sweet barrel that's almost like a trophy as soon as I empty it all out haha:


VP Motorsports "ms109" obviously.