2015 ZL1 knock? Conclusion @ 4/27/15

[ac223mal]

Originally Posted by angryBits

That PDF you posted was very useful.

When I look up ASTM standard D4814 mentioned in that PDF as the required guideline for gas to be used in our cars, seen HERE in Section 1.8 (D), it clearly says 1-10% ethanol is okay. However the GM Tech is saying its not.

EDIT: btw - this proves that California's crap gas needs to be supported by the ZL1 because the manual says so.



You sir have armed me with a legal contract! Thank you!

Glad I could help. Im not having this problem (at least to my knowledge, I might need to invest in a dashlogic or other device to confirm), but I agree with what you are saying.

On a side note, I loved your read on switching from a Cobra to ZL1. I also enjoyed your read on the road trip in the Cobra. Hopefully after this gets sorted out you'll get to take your Z out for one as well.

[Vroom]

I watched the knock ratio today to see if its normal. Except while cold where it peaked at 7.0, at idle the KR stayed at 0.0. Occasionally I got a tiny spike at idle to 0.2. I changed my plugs and wires recently.
I run 91 from either 76 or Costco.

Take it up to the guys at Abel in Rio Vista. When I had the random ticking noise, they believed me when the other dealers wouldn't, then fixed it. Turned out to be a bad spot on the cam. Also, check your exhaust manifold. The back left bolt has come loose for me twice now and it makes a ticking noise when it gets loose.

[Holliss69]

DAMN .... this is disconcerting all the way around. 91 here in AZ but, no issues as of yet (Roto-fab, catch can (and 5% pulley on order))

Good Luck ...... Curious here too

[ZO6 Bryan]

Originally Posted by angryBits

Thinking about this more as it's a good possibility :(

1. Adding a Oil Separator will reduce oil from getting into the combustion which should help a bit with knock.

2. Trick the computer into running richer as a lean Air Flow Ratio causes knock. How to do this without touching the computer? I'm thinking maybe adding a small valve to the intake AFTER the MAF Sensor. The valve should allow me to fine-tune-reduce ACTUAL air pressure AFTER the sensor has recorded it, which means the computer will think it needs to add fuel for more air than there actually is, causing a richer Air Fuel Ratio. Should totally work, however the result will be a slight reduction in power, maybe 5whp which I could gain back with some non-tune bolt ons.

3. Run with Torco - which I really don't want to NEED to do.

None of these should void my warranty. Well #2 might, but how would they know.

1. Won't help. Not unless the engine is f*cked and blowing a lot of oil into the intake.

2. Won't work. That would be equivalent to a vacuum leak and make you run leaner. Not richer.

3. This will definitely help.

And the dealer can't modify your tune. All they can do is flash it with the same tune that you already have.

[angryBits]

Originally Posted by Chrispy

Well it is supported. The car won't blow up or lose a ringland due to California 91 gas, you'll just have KR and eventually move to the low octane table.

It works exactly as designed for Cali gas or from other bad gas you get at the pump. (When a pump truck puts 87 into the 91-93 tanks for example)

If you want the full performance out of the car use Torco or a race gas blend, otherwise you'll need to suck it up and live with some KR, a shift to the low octane table and less horsepower/torque.

I entirely disagree.

The manual says if you're experiencing knock from 91 octane, you should get it serviced. It does not say knocking is okay. Knocking is never okay except maybe if its one time and then learned away forever.

It was not designed to knock continuously every time I put my pedal to the floor.

[angryBits]

Originally Posted by ac223mal

Glad I could help. Im not having this problem (at least to my knowledge, I might need to invest in a dashlogic or other device to confirm), but I agree with what you are saying.

Worth it as a tool, though I was hoping to just leave it plugged in to augment my car with instant gas mileage and such, however the navigation on my car doesn't work when the DashLogic is plugged in :/

Originally Posted by ac223mal

On a side note, I loved your read on switching from a Cobra to ZL1. I also enjoyed your read on the road trip in the Cobra. Hopefully after this gets sorted out you'll get to take your Z out for one as well.

Sweet! Thanks for reading! I'll definitely do another write up once I get the ZL1 on the open road

[angryBits]

Originally Posted by Vroom

I watched the knock ratio today to see if its normal. Except while cold where it peaked at 7.0, at idle the KR stayed at 0.0. Occasionally I got a tiny spike at idle to 0.2. I changed my plugs and wires recently.
I run 91 from either 76 or Costco.

Take it up to the guys at Abel in Rio Vista. When I had the random ticking noise, they believed me when the other dealers wouldn't, then fixed it. Turned out to be a bad spot on the cam. Also, check your exhaust manifold. The back left bolt has come loose for me twice now and it makes a ticking noise when it gets loose.

Interesting, I'll pass this info onto the dealer next time I'm down there. Thanks!

[angryBits]

Originally Posted by ZO6 Bryan

1. Won't help. Not unless the engine is f*cked and blowing a lot of oil into the intake.

2. Won't work. That would be equivalent to a vacuum leak and make you run leaner. Not richer.

3. This will definitely help.

1. The car does blow a lot of oil into the intake. I've seen threads on this. I saw a thread where someone found a few teaspoons worth in their catch can after only a few hundred miles. Hopefully thats an extreme case, but I may also be an extreme case. Won't know till I try

2. You're right, that is under vacuum, darn. Then I wonder if the MAF sends a voltage to the computer to indicate air volume, or if its a pulse width modulation. If its a voltage I can splice in a variable resistor to scale the voltage. If its pulse width modulation, I'll need to build a small microcontroller to to read in the PWM and scale it slightly and then forward on to the computer, either way it should be pretty easy to do without touching the "tune" and avoid voiding my warranty.

3. Total last resort.

Originally Posted by ZO6 Bryan

And the dealer can't modify your tune. All they can do is flash it with the same tune that you already have.

Are you sure about that? If that's true, then that seems kind of silly. The stock tune has a fuel mapping just line any aftermarket tune.
It's certainly tuneable, maybe more of a question of whether or not they're willing to alter the tune on a case by case basis.
If they're not then I'm stuck trying #1 or #2.

[ZO6 Bryan]

Originally Posted by angryBits

1. The car does blow a lot of oil into the intake. I've seen threads on this. I saw a thread where someone found a few teaspoons worth in their catch can after only a few hundred miles. Hopefully thats an extreme case, but I may also be an extreme case. Won't know till I try

2. You're right, that is under vacuum, darn. Then I wonder if the MAF sends a voltage to the computer to indicate air volume, or if its a pulse width modulation. If its a voltage I can splice in a variable resistor to scale the voltage. If its pulse width modulation, I'll need to build a small microcontroller to to read in the PWM and scale it slightly and then forward on to the computer, either way it should be pretty easy to do without touching the "tune" and avoid voiding my warranty.

3. Total last resort.



Are you sure about that? If that's true, then that seems kind of silly. The stock tune has a fuel mapping just line any aftermarket tune.
It's certainly tuneable, maybe more of a question of whether or not they're willing to alter the tune on a case by case basis.
If they're not then I'm stuck trying #1 or #2.

You have seen a lot of oil in your intake? A new engine should not do that. Mine is always dry inside. And don't believe every thread on the internet. If there is oil in you intake at such low mileage then the you should have the dealer investigate that. Now there is oil vapor and water vapor from the crankcase that pases thru the intake and is burned in the engine without any ill effects. But excess oil pooling in the intake is not normal and will essentially lower the octane.

And yes I am sure about the tune. All they can do is download the newest update to the tune from GM and load it in your car. They can't and are not allowed to modify it. There may be an update for your car, and then there may not. And maybe you all ready have the most current tune file loaded. It's not like microsoft, they only update if they find a problem. Once or twice maybe.

[angryBits]

Originally Posted by ZO6 Bryan

You have seen a lot of oil in your intake? A new engine should not do that. Mine is always dry inside. And don't believe every thread on the internet. If there is oil in you intake at such low mileage then the you should have the dealer investigate that. Now there is oil vapor and water vapor from the crankcase that pases thru the intake and is burned in the engine without any ill effects. But excess oil pooling in the intake is not normal and will essentially lower the octane.

I don't have my car to check my intake. The thread I read that I mentioned, that guy said his car was brand new like mine. Agreed a new engine should not do that -- however if all our engines did only what they should, then we'd all be problem free and happy campers

Originally Posted by ZO6 Bryan

And yes I am sure about the tune. All they can do is download the newest update to the tune from GM and load it in your car. They can't and are not allowed to modify it. There may be an update for your car, and then there may not. And maybe you all ready have the most current tune file loaded. It's not like microsoft, they only update if they find a problem. Once or twice maybe.

I agree a dealer can't do it, but they have a Technician from GM working on this. I'm not clear on whether you're saying GM can't or won't. Won't is believable, but can't isn't true.

[Howdie_]

I have a '13. Lot's of talk about what the manual says, here's what mine says under the ZL1 heading:
If the vehicle has the 6.2L V8 engine (VIN Code P), use premium unleaded gasoline with a posted octane rating of 91 or higher. For best performance, use premium unleaded gasoline with a posted octane rating of 93. You can also use regular unleaded gasoline rated at 87 octane or higher, but the vehicle's acceleration could be slightly reduced, and a slight audible knocking noise, commonly referred to as spark knock, might be heard. If the octane rating is less than 87, a heavy knocking noise might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible.

I don't work for GM, but I think this says, if you use less than 93 octane, you will experience less performance, might hear some pinging, but we got your back, to control it, KR. I know the first mechanic was a dick, but he might have just been stating what he found, they all knock in Cali (or at least cause KR). Is it possible this fits "normal" operation. No disrespect, I feel for you guys there...

[Howdie_]

As in formation, we have 94 widely available in this province.

[angryBits]

Originally Posted by Howdie_

I have a '13. Lot's of talk about what the manual says, here's what mine says under the ZL1 heading:
If the vehicle has the 6.2L V8 engine (VIN Code P), use premium unleaded gasoline with a posted octane rating of 91 or higher. For best performance, use premium unleaded gasoline with a posted octane rating of 93. You can also use regular unleaded gasoline rated at 87 octane or higher, but the vehicle's acceleration could be slightly reduced, and a slight audible knocking noise, commonly referred to as spark knock, might be heard. If the octane rating is less than 87, a heavy knocking noise might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible.

I don't work for GM, but I think this says, if you use less than 93 octane, you will experience less performance, might hear some pinging, but we got your back, to control it, KR. I know the first mechanic was a dick, but he might have just been stating what he found, they all knock in Cali (or at least cause KR). Is it possible this fits "normal" operation. No disrespect, I feel for you guys there...

That's not what my manual says.

Mine says literally:

"If the vehicle has an LS7 or LSA high performance V8 engine, Use premium unleaded gasoline meeting ASTM specification D4814 with a posted octane rating of 91 or higher. If the octane is less than 91, damage to the engine may occur and may void the vehicle warranty. If heavy knocking is heard when using gasoline rated at 91 octane or higher, the engine needs service."

[Russell James]

Originally Posted by Howdie_

I have a '13. Lot's of talk about what the manual says, here's what mine says under the ZL1 heading:
If the vehicle has the 6.2L V8 engine (VIN Code P), use premium unleaded gasoline with a posted octane rating of 91 or higher. For best performance, use premium unleaded gasoline with a posted octane rating of 93. You can also use regular unleaded gasoline rated at 87 octane or higher, but the vehicle's acceleration could be slightly reduced, and a slight audible knocking noise, commonly referred to as spark knock, might be heard. If the octane rating is less than 87, a heavy knocking noise might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible.

I don't work for GM, but I think this says, if you use less than 93 octane, you will experience less performance, might hear some pinging, but we got your back, to control it, KR. I know the first mechanic was a dick, but he might have just been stating what he found, they all knock in Cali (or at least cause KR). Is it possible this fits "normal" operation. No disrespect, I feel for you guys there...

Exactly. 93 is going to run a whole lot better than 91.

A dealer cannot alter a calibration. Not possible. They can load whatever calibration is available for that VIN through GM. Sometimes updates come through for a specific reason, and it would be labeled on the file list what it addresses.

Drive car and enjoy. Want more power, increase the octane.

Unless you're going to road course it really hard where you are flooding the valve covers on long sweepers... doesn't need a catch can. Doesn't need the MAF messed with. Green engines do burn a little oil, and will put more up into the intake through the pcv than a broken in engine.

Stop looking for oil and knock and engine the car. I've seen tons of new cars with oil in the intake. Pre break in, engines have a lot of blow by. The oil burn usually calms down after a couple thousand miles.