The Amazing 5.3 L83 V8

Coppertone · February 25, 2016

Any dyno tests or anything other than placebo?

Badass69 · February 25, 2016

Running one tank of 91 on a truck that normally sees 87 won't do much of anything. The truck does learn thanks to adaptives and they will not instantly reset with a change in fuel octane for one tank. If you run 5000 miles of either consistently and then report back you will have a pretty accurate set of feedback. Running 87 for thousands of miles and then one tank of 91 is pretty well meaningless..... The truck has no gauge of fuel change in the tank beyond ethanol content if it has an ethanol sensor and E85.

CH15GMC · February 25, 2016

Running one tank of 91 on a truck that normally sees 87 won't do much of anything. The truck does learn thanks to adaptives and they will not instantly reset with a change in fuel octane for one tank. If you run 5000 miles of either consistently and then report back you will have a pretty accurate set of feedback. Running 87 for thousands of miles and then one tank of 91 is pretty well meaningless..... The truck has no gauge of fuel change in the tank beyond ethanol content if it has an ethanol sensor and E85.

This my be true but I ran 87 and read that it might run better on 89 or 91 so I filled up with a tank of 91 and the truck ran awesome. After that tank I went back to 87 and noticed it didn't run as well. Next fill up I put 89 in (read somebody said they didn't notice a difference between 89 and 91) and it ran awesome so I've stuck with 89 the last few fill ups with great results. No expert but I think it responded quickly in one tank.

tnchevy · February 25, 2016

It will not take thousands of miles it will or would be instantaneous if you run one tank out of 87 and put in a full tank of 91+, that is what the computer does, retards timing based on octane. I don't know where you get the idea that it would take thousands of miles but I say it is not from hard evidence. My motorcycle is air cooled with set timing and requires 91+. You put a tank of 87 in there and you will find know it really fast. Bike will hesitate and ping. Something else people tend to forget is that higher octane does not mean as much in cold temps. I can run 89 in my motorcycle when the temps are below 80 degrees just fine but anything over 80 degrees I have to rune 93. I still do not think there is much of a difference between 87 and 91+ but if it makes you feel better then throw it in there.

Badass69 · February 25, 2016

tnchevy, on 25 Feb 2016 - 05:07 AM, said:tnchevy, on 25 Feb 2016 - 05:07 AM, said:
It will not take thousands of miles it will or would be instantaneous if you run one tank out of 87 and put in a full tank of 91+, that is what the computer does, retards timing based on octane. I don't know where you get the idea that it would take thousands of miles but I say it is not from hard evidence. My motorcycle is air cooled with set timing and requires 91+. You put a tank of 87 in there and you will find know it really fast. Bike will hesitate and ping. Something else people tend to forget is that higher octane does not mean as much in cold temps. I can run 89 in my motorcycle when the temps are below 80 degrees just fine but anything over 80 degrees I have to rune 93. I still do not think there is much of a difference between 87 and 91+ but if it makes you feel better then throw it in there.

Your bike has a simplistic relatively archaic computer attached to it...... about as advanced as a TBI truck from 30 years ago....... If it's new enough it has an O2 sensor..... and that's about as advanced as they get. Have you ever tuned anything yourself on newer GM vehicles? I am just to go ahead and say no you have haven't. It won't take thousands of miles but giving thousands of miles will be an accurate sample of both. GM and many others have these computers designed so they adjust within their set parameters to the nature of how it is driven. They are called adaptives and the newer the computers get the more adaptive learns they use. Look at it this way...... if you ran 87 for all the trucks life and then at 5000 miles decide to swap to 91 for one tank of fuel you really think the computer is going to magically just start adding timing when you drive the same way? It won't...... it's learned in those 5000 miles that it detonates above a certain threshold so it basically just stays there. In time it would try to advance in small increments but if you pulled fuses and reset it to out of box you would have a better gauge on how the truck runs on premium. The adaptives don't just reset when you shut the truck off..... otherwise your transmission as an example would shift like out of box state on every start.

I haven't tuned or logged a 5.3 truck as I don't own one...... but anyone that does tune recommends to run at least midgrade with the stock tune so that is coming from what they see while logging.....

m3n00b · February 25, 2016

87 vs 89 vs 91+ has been discussed in the engine tuning thread. Here's what Jennabear/Justin have brought up in the discussion:

At 11:1 compression ratio (DI or otherwise) the engine *cannot* efficiently run 87 octane under any circumstances. As a result, knock occurs (heard or unheard) and the ECM retards ignition timing both immediately and long term. The result is reduced fuel efficiency (sometimes as high as 3-4mpg) and considerably less power output than would be seen on 89 octane. You won't notice this power loss under light throttle though due to the ECM's method of controlling throttle angle... essentially, the throttle will be opened more for the same power output target on 87 as 89 so that it feels exactly the same to the driver.

In terms of ignition timing, where 18-19 degrees of advance might be the target by GM under the factory tuning, on 87 octane, that timing drops to under 10 degrees of advance to prevent knock from occurring (in response to knock that has already occurred). Anybody that has dealt with ignition timing should see this as a very poor situation. The knock retard occurs early and quickly and then the lasting effects (octane scaler blending the high and low octane tables) will stay in effect for dozens of miles before decaying out.

GM doesn't recommend any higher than 87 because they know that a) they will be vilified for doing so by consumer reports, motor trend, car and driver, etc and b) they know that people won't listen.

http://www.gm-trucks.com/forums/topic/158551-2014-engine-transmission-tuning/page-53?do=findComment&comment=1762274

My truck runs like shit on 87.

What's funny about this is my CX5 2.5L runs great on 87 and has 13:1 compression. Direct injection allows this as the fuel isn't injected until later in the compression stroke keeping detonation at bay. Also the shape of the CX5's cylinders/pistons is said to help. That said, I'll always use 91 or higher in my 6.2 and my M3.

Good read.

http://www.enginebuildermag.com/2013/11/the-skys-the-limit-looking-into-mazdas-skyactiv-engine-technology/

tnchevy · February 25, 2016

Then the people saying their truck is running better and getting better mpg's when running one tank of a higher octane don't know what they are talking about? I don't know, just asking. Does the computer not know enough to retard timing based on octane that the sensors sense? I have not tuned my 2014 but did my 2002. I have also tuned my motorcycle and you are correct in that the computer on it is equal to that of something from the 80's.

bdbake01 · February 25, 2016

My 6.2 consistently drops ~3 mpg on 87 and runs like a dog.

Badass69 · February 25, 2016

Then the people saying their truck is running better and getting better mpg's when running one tank of a higher octane don't know what they are talking about? I don't know, just asking. Does the computer not know enough to retard timing based on octane that the sensors sense? I have not tuned my 2014 but did my 2002. I have also tuned my motorcycle and you are correct in that the computer on it is equal to that of something from the 80's.

Nothing measures octane level. They sense alcohol percentage provided you have the e85 option but that's it. The truck has no idea what fuel grade you put in it.

Sent from my SM-G900W8 using Tapatalk

m3n00b · February 25, 2016

Nothing measures octane level. They sense alcohol percentage provided you have the e85 option but that's it. The truck has no idea what fuel grade you put in it.

Sent from my SM-G900W8 using Tapatalk

All it knows is when it detects detonation, it retards timing.

tnchevy · February 25, 2016

So if it can detect knock then in a sense it is detecting what octane fuel you are using I would think considering that lower octane detonates faster than higher octane.

Badass69 · February 25, 2016

It's a vibration sensor called a knock sensor.... if it you have enough sharp vibration in the front of the truck it will pick that up too. It doesn't sense octane lol. After running with a particular octane just because you increase that thanks to the adaptives it won't just instantly update all the tables to accommodate. A lot of guys get a tune and the tuner will tell you to wait a bit and drive it for a while to see the full benefit...like a couple hundred miles of driving as an example.... this is the same thing.

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Ridersfan · February 26, 2016

Your bike has a simplistic relatively archaic computer attached to it...... about as advanced as a TBI truck from 30 years ago....... If it's new enough it has an O2 sensor..... and that's about as advanced as they get. Have you ever tuned anything yourself on newer GM vehicles? I am just to go ahead and say no you have haven't. It won't take thousands of miles but giving thousands of miles will be an accurate sample of both. GM and many others have these computers designed so they adjust within their set parameters to the nature of how it is driven. They are called adaptives and the newer the computers get the more adaptive learns they use. Look at it this way...... if you ran 87 for all the trucks life and then at 5000 miles decide to swap to 91 for one tank of fuel you really think the computer is going to magically just start adding timing when you drive the same way? It won't...... it's learned in those 5000 miles that it detonates above a certain threshold so it basically just stays there. In time it would try to advance in small increments but if you pulled fuses and reset it to out of box you would have a better gauge on how the truck runs on premium. The adaptives don't just reset when you shut the truck off..... otherwise your transmission as an example would shift like out of box state on every start.

I haven't tuned or logged a 5.3 truck as I don't own one...... but anyone that does tune recommends to run at least midgrade with the stock tune so that is coming from what they see while logging.....

I had a different thread about how long before my truck learns my new exhaust and I caught flack about it saying they don't learn anything... so no matter ones point of view, there's always someone on a forum who will argue it, lol

Badass69 · February 26, 2016

ridersfan, on 26 Feb 2016 - 09:43 AM, said:
I had a different thread about how long before my truck learns my new exhaust and I caught flack about it saying they don't learn anything... so no matter ones point of view, there's always someone on a forum who will argue it, lol

A catback exhaust is a pretty minor change on one of these trucks.... thus there really isn't anything to learn beyond you hammering on the throttle to listen to it.