2015 ZL1 knock? Conclusion @ 4/27/15

[Blueclyde]

Sounds like you're on the right track in understanding your issue. Glad to hear it. My guess is you haven't actually been getting 91 octane out of those pumps.

[angryBits]

Originally Posted by Blueclyde

Sounds like you're on the right track in understanding your issue. Glad to hear it. My guess is you haven't actually been getting 91 octane out of those pumps.

I bet you're right.

I don't know anything about the effects of ethanol in gas, but I'm starting to wonder if 91 w/ ethanol runs significantly worse than 91 w/o ethanol. Time for some internet research

Here in California, it's perfectly okay to put as much as 10% ethanol in the gas.

Sucks for us.

[Six.Two SC]

A quick search said that ethanol can raise octane??? If that's the case, I wonder if us in CA are getting a lower octane gas to start with, then ethanol is added to get it up to 91?


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[Chrispy]

Originally Posted by Six.Two SC

A quick search said that ethanol can raise octane??? If that's the case, I wonder if us in CA are getting a lower octane gas to start with, then ethanol is added to get it up to 91?


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That's what happens with all ethanol gasolines. It's lower octane gas (usually 87) with ethanol added to bring it up to 91.

The problem with ethanol is that it degrades quickly and it also causes the car to run leaner (typically half a point on the wideband in my experience). That's why guys who do full E85 conversion need additional pump and injector capacity for a given RWHP than equivalent RWHP gas counterparts.

Factor that along with the other broader problems ethanol causes (crops that could be used to feed people instead being wasted on gas, increased food prices etc) and I wish the damn stuff was never used.

Cheers
Chris

[Six.Two SC]

Originally Posted by Chrispy

That's what happens with all ethanol gasolines. It's lower octane gas (usually 87) with ethanol added to bring it up to 91.

The problem with ethanol is that it degrades quickly and it also causes the car to run leaner (typically half a point on the wideband in my experience). That's why guys who do full E85 conversion need additional pump and injector capacity for a given RWHP than equivalent RWHP gas counterparts.

Factor that along with the other broader problems ethanol causes (crops that could be used to feed people instead being wasted on gas, increased food prices etc) and I wish the damn stuff was never used.

Cheers
Chris

Thanks, Chris. I had no idea.

Does the 93 octane that's available throughout most of the country contain ethanol, just more of it than CA?


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[Blueclyde]

Ethanol (alcohol) is an oxygenate in the fuel. Its been around for years. The intent is to lessen the amount of crude oil in gasoline. It also provides to US farmer with another outlet for corn. It does not hurt the octane rating. Ethanol actually has higher octane. It does have lower energy content though.

It's not likely the ethanol. All of the fuel here in Detroit is 10% ethanol. Sometimes its just a bad batch of fuel. I purchase my fuel or my ZL1 from 1 station only and 1 specific location. It happens to be a Mobil station. We have 93 octane available here and I'm lucky enough to of never had a problem.

[DrkPhx]

Just for the sake of sanity, I would have the fuel tested to make sure it's really 91 and for moisture. Many years ago when I lived in CA Arco was caught putting regular gas in the high octane pumps after many people complained. But that was in So Cal. I'm not saying that's the case here, but you never know.

[Cybeast]

Originally Posted by Chrispy

That's what happens with all ethanol gasolines. It's lower octane gas (usually 87) with ethanol added to bring it up to 91.

The problem with ethanol is that it degrades quickly and it also causes the car to run leaner (typically half a point on the wideband in my experience). That's why guys who do full E85 conversion need additional pump and injector capacity for a given RWHP than equivalent RWHP gas counterparts.

Factor that along with the other broader problems ethanol causes (crops that could be used to feed people instead being wasted on gas, increased food prices etc) and I wish the damn stuff was never used.

Cheers
Chris

Ethanol is a cleaner burning fuel and causes no broader problems accept for oil companies (corn prices have dropped in half have food prices dropped any no!)

[MTCobra]

As others have said, gasoline is produced at a lower octane because the ethanol actually raises the octane to the finished spec...whatever grade it is. Ethanol has an affinity for water (polar). If a gas station does not manage their tank bottoms (water), the ethanol can settle out of the gasoline and bind with the water on the bottom.

Obviously this creates 2 issues. 1) the remaining gasoline is a lower octane because the ethanol has bound with water and is on the bottom of the tank, and 2) you could get a slug of the ethanol water. Most likely in my mind is you fill up with gasoline that's a lower octane because the ethanol settled out.


2014 ZL1

[Jeb114]

Maybe the wait well be over soon. Maine has passed a bill to eliminate ethanol from gasoline. There are about 20 States that are pushing bills to do the same thing.

[jessrayo]

I've been reading this thread off and on and wanted to make some comments.

First off in Oklahoma we have 91 octane E10 gas at the vast majority of stations. For the little time I drove my car stock on 91 I never noticed knock on pump gas. I have observed knock related to elevated IAT2 on several occasions. I can observe KR on my aeroforce gauges and if I look at the gauge when I hear and feel the knock I can see the digital confirmation of KR. There is no doubt in my mind you are hearing the knock... I hear it when it happens.

I think you have a problem that has not been identified or resolved. Because the car should not knock like that without beating on it. I have put my car on a road course at 100 degrees ambient and ran flat out till the paint on the brake calipers was smoking....and all the supercharger coolant had boiled out. Just hitting the throttle is nothing. I would contact Able Chevrolet and give them a run down of what has passed so far and see if they would be willing and able (pun intended) to bore scope it. Have them look for any sign of head gasket material in the bore. I kind of think changing the head gasket might fix your problem.

If the bore scope gets done and no problems are found I would take the car to a good tuner, add a pulley, headers, whatever else you want to do and tune it so it doesn't knock. I might even port the Heads just so you change out the Head gasket in case that is the problem and no one finds it.

As you said previously, that knocking will probably not affect GM over the life of their warranty but it will reduce the ability of the engine to handle more power in the future. So if they won't fix it I think it is in your best interest to fix it yourself. If you are going to fix the tune you might as well do a complete set of mods before you tune. There are many OK cars that make over 700 wph on 91 octane E10 gas and don't knock at all....and you can beat on them.

If you have a choice between 91 E10 or 91 pure gas, run the pure gas. As someone else pointed out above ethanol raises octane so 91 E10 is really about 87 gas with the ethanol blend...it is crap. But that is what I usually have to run in Oklahoma. Pure gas is more stable and it has more energy per gallon than ethanol.

My last point, in post #213 Z06 Bryan asked you about total ignition advance. It seemed like the answer you gave him was for knock retard. The engine is out of my Camaro again now so I can't look at what parameters you can see on the dashlogic but I think you can see total ignition advance, you may have to compare base spark and PCM spark adjust, I know you can see those two. Anyway, how much total advance you have at WOT is a factor here. That was Bryan's point. I know you are new on here but I have learned that Bryan is pretty darn sharp when it comes to anything concerning the tune in the car. Actually he has been on Camaro 5 longer than I have and doesn't post near as much as I do so if he takes the time to say anything about anything I would pay attention. I'm so radical I don't always agree with him but I've never seen him give bad advice. Good luck.

Okay one more point...if you decide not to tune you really should run torco...it has tested as the best octane booster and in generall it is as effective and cheaper than running race gas.

[angryBits]

Originally Posted by MTCobra

As others have said, gasoline is produced at a lower octane because the ethanol actually raises the octane to the finished spec...whatever grade it is. Ethanol has an affinity for water (polar). If a gas station does not manage their tank bottoms (water), the ethanol can settle out of the gasoline and bind with the water on the bottom.

Obviously this creates 2 issues. 1) the remaining gasoline is a lower octane because the ethanol has bound with water and is on the bottom of the tank, and 2) you could get a slug of the ethanol water. Most likely in my mind is you fill up with gasoline that's a lower octane because the ethanol settled out.


2014 ZL1

+1

This is what my internet research lead me to believe as well.

Ethanol is fine if properly managed, but its often improperly managed. Water gets in side or the ethanol goes bad and gas stations don't care. This causes inconsistent crappy gas.

[angryBits]

Originally Posted by jessrayo

I've been reading this thread off and on and wanted to make some comments.

First off in Oklahoma we have 91 octane E10 gas at the vast majority of stations. For the little time I drove my car stock on 91 I never noticed knock on pump gas. I have observed knock related to elevated IAT2 on several occasions. I can observe KR on my aeroforce gauges and if I look at the gauge when I hear and feel the knock I can see the digital confirmation of KR. There is no doubt in my mind you are hearing the knock... I hear it when it happens.

I think you have a problem that has not been identified or resolved. Because the car should not knock like that without beating on it. I have put my car on a road course at 100 degrees ambient and ran flat out till the paint on the brake calipers was smoking....and all the supercharger coolant had boiled out. Just hitting the throttle is nothing. I would contact Able Chevrolet and give them a run down of what has passed so far and see if they would be willing and able (pun intended) to bore scope it. Have them look for any sign of head gasket material in the bore. I kind of think changing the head gasket might fix your problem.

If the bore scope gets done and no problems are found I would take the car to a good tuner, add a pulley, headers, whatever else you want to do and tune it so it doesn't knock. I might even port the Heads just so you change out the Head gasket in case that is the problem and no one finds it.

As you said previously, that knocking will probably not affect GM over the life of their warranty but it will reduce the ability of the engine to handle more power in the future. So if they won't fix it I think it is in your best interest to fix it yourself. If you are going to fix the tune you might as well do a complete set of mods before you tune. There are many OK cars that make over 700 wph on 91 octane E10 gas and don't knock at all....and you can beat on them.

If you have a choice between 91 E10 or 91 pure gas, run the pure gas. As someone else pointed out above ethanol raises octane so 91 E10 is really about 87 gas with the ethanol blend...it is crap. But that is what I usually have to run in Oklahoma. Pure gas is more stable and it has more energy per gallon than ethanol.

My last point, in post #213 Z06 Bryan asked you about total ignition advance. It seemed like the answer you gave him was for knock retard. The engine is out of my Camaro again now so I can't look at what parameters you can see on the dashlogic but I think you can see total ignition advance, you may have to compare base spark and PCM spark adjust, I know you can see those two. Anyway, how much total advance you have at WOT is a factor here. That was Bryan's point. I know you are new on here but I have learned that Bryan is pretty darn sharp when it comes to anything concerning the tune in the car. Actually he has been on Camaro 5 longer than I have and doesn't post near as much as I do so if he takes the time to say anything about anything I would pay attention. I'm so radical I don't always agree with him but I've never seen him give bad advice. Good luck.

Okay one more point...if you decide not to tune you really should run torco...it has tested as the best octane booster and in generall it is as effective and cheaper than running race gas.

Agreed on all points. Sorry to hear about your car troubles, but glad to hear someone can relate

Regarding Z06 Bryan, everyone seems to be defending him as though I've argued? I'm not sure why -- I don't think I've done any bashing or arguing (at least not intentionally). If it appeared that I did, I apologize. I'm a reasonable person and open to all good advice and can be persuaded away from my own ideas. However if my ideas still hold water, naturally I'm going to try them :P

I agreed with Z06 Bryan regarding the modification to the air intake -- he was right, that area is under vacuum and wouldn't work.

I semi-agreed about the Oil Separator. I think he's probably right, but its worth trying since its cheap and it wont hurt.

Regarding the tune -- it was really a matter of misunderstanding -- I think ultimately we agreed that it can be overwritten but GM won't do it.

That all seems fair to me, not sure why people are playing defense

[Chrispy]

Originally Posted by Cybeast

Ethanol is a cleaner burning fuel and causes no broader problems accept for oil companies (corn prices have dropped in half have food prices dropped any no!)

It's opportunity cost. Wasting acreage to produce ethanol versus other crops.