Just put 3 gallons of 109 Octane in the beast :)
10-15-2011, 12:27 PM
#27
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96 and 08 911 turbos
What is bold is true...but 99% of all E55's will see SOME knock activity unless it is dyno tuned or EXTREMELY conservative and even then it tends to happen. Even 100% bone stock E55's have knock retard.
In this case, adding higher octane fuel WILL make more power due to the knock activity going away and it should be near instant ( maybe 2-5 minutes into it as the fuel system will take a while to exchange the old fuel with the new one ).
However, if you car is one of those cars with no knock retard due to your tune being conservative...it will not make more power. I've done the test before on my Ex-GTI 1.8T. If your engine makes a perfect combustion on 93oct fuel, 109oct will not make the combustion any better/powerful.
I think a lot of people don't realize WHY their cars make more power on race gas. It's not because the fuel it's self makes a more powerful combustion or because the ECU will advance timing all by it's self when it "sees" the race gas. It because most vehicles have SOME kind of knock retardation and when you put race gas that retardation will generally go away.
For example, your car at any given moment may see 18* of timing advance but the knock control is removing 2* due to knock activity at that moment so you end up with 16* total timing. With race gas, you'd get the whole 18*.
But this is not guaranteed, because if my car sees ZERO degrees of knock retard, then the car will continue to put out the same 18* regardless of octane ( 93 or above ).
Now, if your car is SWITCHING to a low octane map because of knock retard, then you will feel a HUGE difference after a while of driving with the race gas when it switches back to the high octane map...but this should not happen as your vehicle should be operating 100% of the time in the high octane map...if not then it needs a tune badly.
In this case, adding higher octane fuel WILL make more power due to the knock activity going away and it should be near instant ( maybe 2-5 minutes into it as the fuel system will take a while to exchange the old fuel with the new one ).
However, if you car is one of those cars with no knock retard due to your tune being conservative...it will not make more power. I've done the test before on my Ex-GTI 1.8T. If your engine makes a perfect combustion on 93oct fuel, 109oct will not make the combustion any better/powerful.
I think a lot of people don't realize WHY their cars make more power on race gas. It's not because the fuel it's self makes a more powerful combustion or because the ECU will advance timing all by it's self when it "sees" the race gas. It because most vehicles have SOME kind of knock retardation and when you put race gas that retardation will generally go away.
For example, your car at any given moment may see 18* of timing advance but the knock control is removing 2* due to knock activity at that moment so you end up with 16* total timing. With race gas, you'd get the whole 18*.
But this is not guaranteed, because if my car sees ZERO degrees of knock retard, then the car will continue to put out the same 18* regardless of octane ( 93 or above ).
Now, if your car is SWITCHING to a low octane map because of knock retard, then you will feel a HUGE difference after a while of driving with the race gas when it switches back to the high octane map...but this should not happen as your vehicle should be operating 100% of the time in the high octane map...if not then it needs a tune badly.
But yes, what you are saying is correct.
This is not true. A car can not be tuned for optimal ignition timing for every weather therefore a vehicle with any kind of ignition advance will always have some sort of timing correction from either higher intake air temps on a warmer day or from inaudible knock picked up by knock sensors. That is completely normal even on a stock vehicle and is the reason the engine management system has the ability to adjust for over 10*.
It is quite logical to think about. If a car is tuned to show optimal ignition advance in 70 degree weather then the same car when running in 80 degree weather while experiencing less dense air and higher intake air temps will adjust for it and pull timing accordingly or on the flip side in cold weather will have all it's parameters met to allow for full advance and have zero correction.
The properties of race gas help to aid in retaining power based on what it does for the engine.
It is quite logical to think about. If a car is tuned to show optimal ignition advance in 70 degree weather then the same car when running in 80 degree weather while experiencing less dense air and higher intake air temps will adjust for it and pull timing accordingly or on the flip side in cold weather will have all it's parameters met to allow for full advance and have zero correction.
The properties of race gas help to aid in retaining power based on what it does for the engine.
Beyond what the knock sensors are doing, the car has no idea what fuel you are running.
Furthermore, race fuel, especially leaded race fuel (which is horrific for 02 sensors), has a different stoich a/f ratio. Just dumping that in with no consideration to how the appropriate a/f may have changed, can again result in damage.
10-15-2011, 01:35 PM
#28
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05 White Pano E55, Cadillac CTS-V
Thats disappointing for mb then. In my opinion, a stock vehicle should see very little knock sensor activity. If you are going to be pulling the timing from detonation anyway, why not just run lower timing in the first place. Knock Sensors are not perfect and any detonation is bad.
But yes, what you are saying is correct.
NO, see below
not really. As IAT's rise, the computer will pull timing based on IATs. If it also sees knock, then you get more timing reduction. But if the IATs rise, and the car pulls some timing, but the knock sensors are not active, race gas will not "return" that additional timing advance.
Beyond what the knock sensors are doing, the car has no idea what fuel you are running.
Furthermore, race fuel, especially leaded race fuel (which is horrific for 02 sensors), has a different stoich a/f ratio. Just dumping that in with no consideration to how the appropriate a/f may have changed, can again result in damage.
But yes, what you are saying is correct.
NO, see below
not really. As IAT's rise, the computer will pull timing based on IATs. If it also sees knock, then you get more timing reduction. But if the IATs rise, and the car pulls some timing, but the knock sensors are not active, race gas will not "return" that additional timing advance.
Beyond what the knock sensors are doing, the car has no idea what fuel you are running.
Furthermore, race fuel, especially leaded race fuel (which is horrific for 02 sensors), has a different stoich a/f ratio. Just dumping that in with no consideration to how the appropriate a/f may have changed, can again result in damage.
Most people who get serious about the race fuel run VP MS109 which is pretty much the best unleaded race fuel you can get and is highly oxygenated. I talked about this in another thread yesterday explaining how race fuel has alcohol in it to oxygenate the fuel and alcohol pulls heat out of the air making the intake mixture cooler which results in cooler cylinder temperatures and that resists detonation better.
A car uses more than one parameter to reduce ignition advance, there are multiple things that work together to decide what to do. You are explaining that when intake air temps rise the car will pull timing but that is because generally when the intake air temps are high then the engine is more prone to have detonation from increased cylinder temps and volatile air/fuel mixtures and ignite at the wrong time (detonation).
Knock sensors pick up changes in the frequency the are programmed on, and then pull timing from increased knock voltages (spikes). Race fuel changes all this so a high ambient temperature won't affect cylinder temperatures which higher temperatures can cause detonation. And use the word detonation loosly because there is inaudible knock which is still "detonation" but is very minor and nothing to worry about. That is what the knock sensors pick up with the changes in frequency they listen for and then adjust the timing in small amounts accordingly.
10-28-2011, 07:20 PM
#29
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2014 E63s amg 4matic, 2009 C63, 2006 E55 AMG , 2001.5 AUDI S4 stg 3+ w/meth
that "highly oxygenated" part you speak of on race fuels changes the stoichiometric air/fuel point vs regular fuel that the car and any non-race gas tune was designed to run its computations off of... but you knew this already right master tuner?
remember that your afr gauge is calibrated to a lambda 1.0 = 14.2-14.7 for stoichiometric air/fuel point pump gas. Race fuels especially those that are oxygenated have lower afr ratings...VP 109 unleaded race fuel is 13.65.
so under wot you may be tuned to say .8 or 11.2 but because the calibration based on pump stoichiometric is off you can run lean on race gas and we know what happens from there..
cars ecus do no adjust for stoichiometric air/fuel points.. thats why there have to be seperate octane files and switchable tunes for different octanes
and to the point of timing being pulled based upon knock, yes race fuel would help prevent that, but that dooes not give you any extra power above and beyond when the car is running healthy without knock... so if you dyno best at 500hp with no timing retarding due to knock and then put in race fuel, your not going to have any more HP over that 500
remember that your afr gauge is calibrated to a lambda 1.0 = 14.2-14.7 for stoichiometric air/fuel point pump gas. Race fuels especially those that are oxygenated have lower afr ratings...VP 109 unleaded race fuel is 13.65.
so under wot you may be tuned to say .8 or 11.2 but because the calibration based on pump stoichiometric is off you can run lean on race gas and we know what happens from there..
cars ecus do no adjust for stoichiometric air/fuel points.. thats why there have to be seperate octane files and switchable tunes for different octanes
and to the point of timing being pulled based upon knock, yes race fuel would help prevent that, but that dooes not give you any extra power above and beyond when the car is running healthy without knock... so if you dyno best at 500hp with no timing retarding due to knock and then put in race fuel, your not going to have any more HP over that 500
Last edited by gaspam; 10-28-2011 at 08:50 PM.
10-29-2011, 01:42 PM
#32
that "highly oxygenated" part you speak of on race fuels changes the stoichiometric air/fuel point vs regular fuel that the car and any non-race gas tune was designed to run its computations off of... but you knew this already right master tuner?
remember that your afr gauge is calibrated to a lambda 1.0 = 14.2-14.7 for stoichiometric air/fuel point pump gas. Race fuels especially those that are oxygenated have lower afr ratings...VP 109 unleaded race fuel is 13.65.
so under wot you may be tuned to say .8 or 11.2 but because the calibration based on pump stoichiometric is off you can run lean on race gas and we know what happens from there..
cars ecus do no adjust for stoichiometric air/fuel points.. thats why there have to be seperate octane files and switchable tunes for different octanes
and to the point of timing being pulled based upon knock, yes race fuel would help prevent that, but that dooes not give you any extra power above and beyond when the car is running healthy without knock... so if you dyno best at 500hp with no timing retarding due to knock and then put in race fuel, your not going to have any more HP over that 500
remember that your afr gauge is calibrated to a lambda 1.0 = 14.2-14.7 for stoichiometric air/fuel point pump gas. Race fuels especially those that are oxygenated have lower afr ratings...VP 109 unleaded race fuel is 13.65.
so under wot you may be tuned to say .8 or 11.2 but because the calibration based on pump stoichiometric is off you can run lean on race gas and we know what happens from there..
cars ecus do no adjust for stoichiometric air/fuel points.. thats why there have to be seperate octane files and switchable tunes for different octanes
and to the point of timing being pulled based upon knock, yes race fuel would help prevent that, but that dooes not give you any extra power above and beyond when the car is running healthy without knock... so if you dyno best at 500hp with no timing retarding due to knock and then put in race fuel, your not going to have any more HP over that 500
