TheLion
Well-Known Member
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For a while I've been preaching for street cars that you run an octane buffer because of varying fuel quality issues. Most of the after market tunes are fairly aggressive with timing. So 91 tunes assume it's absolutely bar none 91 octane minimum and 93 tunes assume absolutely bar none its 93.
The exception is maybe Ford Performance whose tune is a bit more on the conservative side (I might rank the Cobb Stage 1 in this category as well), but I think even Livernois, probably the next most conservative tune beyond those two, assumes the fuel is up to snuff.
I've been doing a little digging to get to the bottom of some of these early engine failures and I've suspected fuel quality to play a part as well as possibly oil contamination and manufacturing variations for some time now but in conjunction with the fact that people are running very hot tunes on pump gas and some engines just will not tolerate as much as others (metallurgical variances in the pistons, rods and even assembly process). I think honestly though these failures could have been avoided if we weren't trying to squeeze every last hp out of a street car. Diminishing returns and lack of safety margins to account of things outside of our control.
Throw into the mix environmental factors (hot ambients), for example yesterday it was 91F outside, even with the oil cooler, PP radiator and ATM inter cooler, no AGS on the FP tune I was seeing higher oil temps and cylinder head temps while cruising on the highway than on a 80F day. It just felt hot out that day even though the ambient wasn't super high and the car felt it too. Mind you nothing was out of control hot by any means, but it was definitely running hotter than typical.
Anyway, I found some testing done on the actual octane of gas coming out of the pump at various stations. I want to note something here, these variations can occur at any station of the same chain, so BP gas here in my state may not be the same as BP gas in your state. Also smaller stations tend to have poorer fuel quality (lots of dirt and water in their tanks) which can increase fouling / contamination.
My dad has been a service tech for over 25 years in the petroleum industry. He does installations of pump control electronics and repairs including inside the underground tanks. His advice to me was to try to get gas at larger higher volume stations that typically maintain their tanks better. The little ma and pa stations run them into the ground due to their low profit margins, so they tend to let maintenance go for much longer intervals and the fuel sits in the tanks longer as well before it's used up and refilled.
Anyway, one of the primary protection methods (along with a few other forum members) I've been preaching has been to run an octane buffer. IF your running a non adaptive tune like Livernois, T+, Unleashed etc. or any other tune that assumes a minimum of XX octane and your car is a daily driver that may fill up at many different stations around your area or when you travel, you would be very well served to run an octane buffer.
The more aggressive the tune, the more sensitive to fuel: http://www.wpxi.com/news/local/target-11-investigates-octane-levels-gasoline/197799439
Note that the margin of safety that is present on a factory tune is not likely present on most of the aftermarket tunes. You have to give up some safety margin at some point to get more power, there's no way around it. Factory 93 tunes are always more conservative than a performance 93 tune, that's PART of where the added power comes from. Some tunes are more aggressive than others, but there are cases where even adaptive factory 91 tunes sometimes will knock on poor fuel quality.
This also explains why the hot tunes running ethanol blends tend to have far fewer failures. Because ethanol is significantly better at preventing knock than gasoline in the LSPI research paper I posted a while back. It's the gold standard of knock prevention and even LSPI prevention interestingly enough. Fuel quality, fuel quality, fuel quality. Since we can't guarantee 93 is 93, the best we can do is assume it's not and run a 91 tune while only using 93.
The lowest scoring station's 93 was tested at 92.3. There's a +/- 0.4 octane margin of error on the tests. So it could be 92.7 but it could also be as low as 91.9! That's more than an entire point lower than the stated value. We can't assume the margin of error is this or that, in order prevent fuel related issues, you must assume the margin of error in the test result is biased high, meaning the worst case is 91.9 when you think your getting 93.
An octane buffer of 2 points would create enough margin of safety to prevent fuel quality variations from being a significant factor. Your only going to give up around 7-10 hp, so unless your competitively racing it's not work the risk and damage to your engine. I have a feeling that the Livernois tuned car that made it to 65k suffered from continual fuel quality issues. He ran a 93 tune on 93 octane, but was getting enough fill ups that were closer to 92 or even high 91 that periodic detonation or knock was occurring and eventually caused the piston failure. A tune that is set up for 93 can't scale back timing fast enough or in large enough increment to run 91 octane without damaging the engine, that's why it requires 93...the program is tuned very specifically to that fuel and assumes a minimum octane rating.
Adaptive tunes like the Ford Performance tune or the OE tune can adapt and scale back, but they don't make as much power. The Ford Performance tune is designed to run on 91 +/- the industry standard margin of error safely. So it assumes 91 might be slightly below 91 and the timing strategy is conservative enough to prevent issues (baring no mechanical defects lurk that might cause a catastrophic failure).
Quite a few failed engines seems to fail very shortly after fill up. I am theorizing that their fuel was on the low end of the allow able tolerance for 93 or 91 for those in cali, as per industry standards, but their tune was very aggressive in it's assumption of 93 being a minimum of 93 or better, not 92.3 or 91.9. It may have lead to frequent detonation or severe detonation or possibly a pre-ignition that triggered an LSPI event or multiple sequentaial LSPI events or even random LSPI events which your PCM is completely blind to. Like getting shot in the head by a .338 Lapua Magnum from 1000 yards, you'd never know what hit you...
Octane buffers should go a really long way in preventing detonation or even pre-ignition which could also lead to LSPI. Also the sum total of cooling system upgrades combined also has a significant impact (also the general consensus in the LSPI research paper).
- 1 Step Colder plugs (Do NOT use non-projected tip plugs unless your running exotic fueling etc., otherwise you'll see heavy fouling like I did, the NGK 6510's seem to be a good quality plug that is semi-projected tip like the OE so it's seating depth is appropriate for pump gas applications, but it's rated at 1 step colder than stock). I believe Denso has a similar plug but has recently been suffering from quality issues. Gap to 0.028 - 0.030 (this gapping range was also recommended by Mike Goodwin at Ford Performance and falls inline with most tuners recommendations as well).
- Inter cooler obviously, this has been preached to death, but it doesn't need to be the biggest one, just a nice stage 1 unit would do the trick, however the inter cooler doesn't help with cooling while cruising at lower RPM's and lighter loads, it requires pressurized air to be efficient so when your running NA or low boost it's not going provide much benefit, it's in the power band at WOT where you will see power benefits and cooling benefits.
- For base model cars, a PP radiator is a must for added heat
- Oil cooler can help a little with cylinder head temps, cooler oil means more thermal capacity is available to cool the cylinder heads, also limits coking, thinning and helps maintain pump pressure and flow during track like usage etc.
- CAI, might be over looked, but cooler air going into the turbo is going to mean cooler air coming out (or possibly the turbo running a bit cooler)
- For those who run Livernois, use their 160F thermostat, there's a REASON they recomend it, that's to control cylinder head temps with their tuning
- Probably one of the most important is the Octane buffer, use a 91 tune with 93 octane and you pretty much never have to worry about fuel quality being the issue as you will always be at a minimum of 91. Octane buffer gives you the ability to run a pure or aggressive 91 tune that does not tolerate significant quality variations as the buffer is large enough based on industry allow able tolerances to insure 91 is actually a minimum of "ideal 91".
- Run a GM Dexos 1 Gen 2 certified oil of your choice, these will not only protect against LSPI, but they reduce oil induced knock, yes some oil will always get into the combustion chamber, it can also induce knock / detonation by lowering the octane even if it doesn't cause LSPI / pre-ignition. This is coming again from the research done on LSPI in that 450 page research paper I posted.
Hope this helps my fellow street car guys, yes, I've done every one of these steps myself except for the oil as the Gen 2 oils are just now making their way to the stores so next change I should be able to switch over. I'm now at 29980 miles and going strong. Run only 93 on the Ford Performance tune. I go WOT all the time, partial throttle etc with full passenger loads and AC on in 80F weather uphill. Not sure you can push the car any more than that! I hit up to 15 psi boost in 6th gear on the highway at times etc. No issues so far. Time will tell how well it holds up, but even if it doesn't, I have a warranty to back me up. There's not much else I can do beyond this to ensure reliability. Once I get the Gen 2 oil in and I hit 36k I am planning on switching back to Livernois 91 but will always run 93.
The exception is maybe Ford Performance whose tune is a bit more on the conservative side (I might rank the Cobb Stage 1 in this category as well), but I think even Livernois, probably the next most conservative tune beyond those two, assumes the fuel is up to snuff.
I've been doing a little digging to get to the bottom of some of these early engine failures and I've suspected fuel quality to play a part as well as possibly oil contamination and manufacturing variations for some time now but in conjunction with the fact that people are running very hot tunes on pump gas and some engines just will not tolerate as much as others (metallurgical variances in the pistons, rods and even assembly process). I think honestly though these failures could have been avoided if we weren't trying to squeeze every last hp out of a street car. Diminishing returns and lack of safety margins to account of things outside of our control.
Throw into the mix environmental factors (hot ambients), for example yesterday it was 91F outside, even with the oil cooler, PP radiator and ATM inter cooler, no AGS on the FP tune I was seeing higher oil temps and cylinder head temps while cruising on the highway than on a 80F day. It just felt hot out that day even though the ambient wasn't super high and the car felt it too. Mind you nothing was out of control hot by any means, but it was definitely running hotter than typical.
Anyway, I found some testing done on the actual octane of gas coming out of the pump at various stations. I want to note something here, these variations can occur at any station of the same chain, so BP gas here in my state may not be the same as BP gas in your state. Also smaller stations tend to have poorer fuel quality (lots of dirt and water in their tanks) which can increase fouling / contamination.
My dad has been a service tech for over 25 years in the petroleum industry. He does installations of pump control electronics and repairs including inside the underground tanks. His advice to me was to try to get gas at larger higher volume stations that typically maintain their tanks better. The little ma and pa stations run them into the ground due to their low profit margins, so they tend to let maintenance go for much longer intervals and the fuel sits in the tanks longer as well before it's used up and refilled.
Anyway, one of the primary protection methods (along with a few other forum members) I've been preaching has been to run an octane buffer. IF your running a non adaptive tune like Livernois, T+, Unleashed etc. or any other tune that assumes a minimum of XX octane and your car is a daily driver that may fill up at many different stations around your area or when you travel, you would be very well served to run an octane buffer.
The more aggressive the tune, the more sensitive to fuel: http://www.wpxi.com/news/local/target-11-investigates-octane-levels-gasoline/197799439
Note that the margin of safety that is present on a factory tune is not likely present on most of the aftermarket tunes. You have to give up some safety margin at some point to get more power, there's no way around it. Factory 93 tunes are always more conservative than a performance 93 tune, that's PART of where the added power comes from. Some tunes are more aggressive than others, but there are cases where even adaptive factory 91 tunes sometimes will knock on poor fuel quality.
This also explains why the hot tunes running ethanol blends tend to have far fewer failures. Because ethanol is significantly better at preventing knock than gasoline in the LSPI research paper I posted a while back. It's the gold standard of knock prevention and even LSPI prevention interestingly enough. Fuel quality, fuel quality, fuel quality. Since we can't guarantee 93 is 93, the best we can do is assume it's not and run a 91 tune while only using 93.
The lowest scoring station's 93 was tested at 92.3. There's a +/- 0.4 octane margin of error on the tests. So it could be 92.7 but it could also be as low as 91.9! That's more than an entire point lower than the stated value. We can't assume the margin of error is this or that, in order prevent fuel related issues, you must assume the margin of error in the test result is biased high, meaning the worst case is 91.9 when you think your getting 93.
An octane buffer of 2 points would create enough margin of safety to prevent fuel quality variations from being a significant factor. Your only going to give up around 7-10 hp, so unless your competitively racing it's not work the risk and damage to your engine. I have a feeling that the Livernois tuned car that made it to 65k suffered from continual fuel quality issues. He ran a 93 tune on 93 octane, but was getting enough fill ups that were closer to 92 or even high 91 that periodic detonation or knock was occurring and eventually caused the piston failure. A tune that is set up for 93 can't scale back timing fast enough or in large enough increment to run 91 octane without damaging the engine, that's why it requires 93...the program is tuned very specifically to that fuel and assumes a minimum octane rating.
Adaptive tunes like the Ford Performance tune or the OE tune can adapt and scale back, but they don't make as much power. The Ford Performance tune is designed to run on 91 +/- the industry standard margin of error safely. So it assumes 91 might be slightly below 91 and the timing strategy is conservative enough to prevent issues (baring no mechanical defects lurk that might cause a catastrophic failure).
Quite a few failed engines seems to fail very shortly after fill up. I am theorizing that their fuel was on the low end of the allow able tolerance for 93 or 91 for those in cali, as per industry standards, but their tune was very aggressive in it's assumption of 93 being a minimum of 93 or better, not 92.3 or 91.9. It may have lead to frequent detonation or severe detonation or possibly a pre-ignition that triggered an LSPI event or multiple sequentaial LSPI events or even random LSPI events which your PCM is completely blind to. Like getting shot in the head by a .338 Lapua Magnum from 1000 yards, you'd never know what hit you...
Octane buffers should go a really long way in preventing detonation or even pre-ignition which could also lead to LSPI. Also the sum total of cooling system upgrades combined also has a significant impact (also the general consensus in the LSPI research paper).
- 1 Step Colder plugs (Do NOT use non-projected tip plugs unless your running exotic fueling etc., otherwise you'll see heavy fouling like I did, the NGK 6510's seem to be a good quality plug that is semi-projected tip like the OE so it's seating depth is appropriate for pump gas applications, but it's rated at 1 step colder than stock). I believe Denso has a similar plug but has recently been suffering from quality issues. Gap to 0.028 - 0.030 (this gapping range was also recommended by Mike Goodwin at Ford Performance and falls inline with most tuners recommendations as well).
- Inter cooler obviously, this has been preached to death, but it doesn't need to be the biggest one, just a nice stage 1 unit would do the trick, however the inter cooler doesn't help with cooling while cruising at lower RPM's and lighter loads, it requires pressurized air to be efficient so when your running NA or low boost it's not going provide much benefit, it's in the power band at WOT where you will see power benefits and cooling benefits.
- For base model cars, a PP radiator is a must for added heat
- Oil cooler can help a little with cylinder head temps, cooler oil means more thermal capacity is available to cool the cylinder heads, also limits coking, thinning and helps maintain pump pressure and flow during track like usage etc.
- CAI, might be over looked, but cooler air going into the turbo is going to mean cooler air coming out (or possibly the turbo running a bit cooler)
- For those who run Livernois, use their 160F thermostat, there's a REASON they recomend it, that's to control cylinder head temps with their tuning
- Probably one of the most important is the Octane buffer, use a 91 tune with 93 octane and you pretty much never have to worry about fuel quality being the issue as you will always be at a minimum of 91. Octane buffer gives you the ability to run a pure or aggressive 91 tune that does not tolerate significant quality variations as the buffer is large enough based on industry allow able tolerances to insure 91 is actually a minimum of "ideal 91".
- Run a GM Dexos 1 Gen 2 certified oil of your choice, these will not only protect against LSPI, but they reduce oil induced knock, yes some oil will always get into the combustion chamber, it can also induce knock / detonation by lowering the octane even if it doesn't cause LSPI / pre-ignition. This is coming again from the research done on LSPI in that 450 page research paper I posted.
Hope this helps my fellow street car guys, yes, I've done every one of these steps myself except for the oil as the Gen 2 oils are just now making their way to the stores so next change I should be able to switch over. I'm now at 29980 miles and going strong. Run only 93 on the Ford Performance tune. I go WOT all the time, partial throttle etc with full passenger loads and AC on in 80F weather uphill. Not sure you can push the car any more than that! I hit up to 15 psi boost in 6th gear on the highway at times etc. No issues so far. Time will tell how well it holds up, but even if it doesn't, I have a warranty to back me up. There's not much else I can do beyond this to ensure reliability. Once I get the Gen 2 oil in and I hit 36k I am planning on switching back to Livernois 91 but will always run 93.
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