The Amazing 5.3 L83 V8

[4x4LJB]

Yup that sounds right.

NORMALLY when a vehicle is properly tuned from factory for say 87 octane, you wouldn't see any difference running a high octane, nothing real noticeable anyway as its tuned to run on 87 and it'll adjust itself.

 

In the case with these trucks it can be noticed that they are not tuned properly, 11:1 shouldn't run 87 octane, my guess is these are either tuned for 89-91 or they just tuned them for a shitty running 87 octane vehicle.

 

I'm home from work in a couple weeks so I intend to hook up my obd 2 scanner and run some real tests, have about 3

/4 tank 87 to burn off so I'll try and log it all, Then I'll fill up with 91 and relog everything and see what I get

 

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Wellll....I dunno about 11:1 not running 87 Octane. The first question I asked was what are the Lift and Duration of the 5.3's camshaft. The reason for the question was that a long duration cam naturally "kills off" compression due to the overlap.

 

When you look at the fact that we're getting 355 SAE Net HP out of 325 Cubic Inches, that would suggest to me a radical cam "tamed" by engine management and VVT.

 

I have a 2006 Chrysler 300C/SRT8, and it's putting out a conservative 425HP SAE Net out of 370 cubic inches. The camshaft is more radical than the one's found in the old 1970-71 426 HEMI, but it idles like a pussycat. Reason? VVT and Engine Management.

[Badass69]

 

I have a 2006 Chrysler 300C/SRT8, and it's putting out a conservative 425HP SAE Net out of 370 cubic inches. The camshaft is more radical than the one's found in the old 1970-71 426 HEMI, but it idles like a pussycat. Reason? VVT and Engine Management.

No VVT ever in any 6.1 car.. that's not the reason for their idle either. 206/211 duration at .050" isn't wild...especially coupled to a 117.5 degree lobe separation angle. Slap a carb on your 6.1.... you can make it idle every bit as smoothe as it does with fuel injection. My Charger needed a cam badly with all else I did to it... but I sold that junk 6 years ago so who cares lol.

 

The L83 has a weak sauce camshaft... it's like 193/199 duration at .050" on a 113 lsa... that's puny by any account. Their octane tolerance at least for what it is comes solely from the direct injection.

 

 

 

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[harveyfamily]

So should we be running 89 in our Traverse since its 3.6 V6 is DI with 11.3 compression?

 

 

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[dave07]

I will kind of echo what scottie is saying. The OEM tune is designed to run on 87 octane fuel. Your truck will most likely run fine on 87. The best advice I received regarding gas is to pump from the busiest station in town and you will most likely get the freshest gas out there. However, You are wasting your money if you put anything higher than mid grade (in these engines).

I've owned a WRX and a 2013 Mustang GT that were both heavily modded and custom tuned. They both used knock sensors as well. Now a little thing about knock, not all of is bad. In fact you will find knock in any data log you do of your car. Knock is bad when it is at WOT or at high load. That is the kind of knock that will blow your engine. You will get knock if you hit a bump, on hard downshifts, and when your car wheel hops.

 

In these 5.3 engines I'm guessing the ecu is constantly reading the knock sensors and adjusting timing accordingly. It does this multiple times a second. You may see a benefit using a higher octane gas as your engine will not be pulling timing at WOT. However, most of the time it will be as waste of money.

 

 

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[Badass69]

You don't just induce spark knock at wide open throttle. .. that's not how this works. Load on the engine will make it knock... that can be at 2500 rpm or 5000 rpm... it doesn't matter. The ignition timing on these is basically non existent too... mid teens at best stock on 6.2 on the high octane table so the 5.3 is probably even less....

 

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[SouthernSilveradoGuy85]

I've only ran my 5.3 with 87 and haven't even tried E85 since I haven't found any E85 stations close to my town. I haven't felt any problems running on 87. But, I also always use top tier gas, no mom and pop stores. I've also used that CRC GDI cleaner a couple times. Maybe I'll try 89, but not in a big rush to.

[scottie350]

Honestly i want to get a look at logs and in different scenarios, i know i can keep an eye on timing advance and everything, not sure if the app i have will record knock tho, so i may have to find one.

 

Still couple weeks before i get home gah killing me. Overly im just curious to run my own tests and see whats going on. It makes sense they couldve say used the puny cam to tame down the requirements, dorect injection does help but, even at 11:1...i dont know, i still want to do some comparisons, and realtime log it myself

 

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[4x4LJB]

Honestly i want to get a look at logs and in different scenarios, i know i can keep an eye on timing advance and everything, not sure if the app i have will record knock tho, so i may have to find one.

 

Still couple weeks before i get home gah killing me. Overly im just curious to run my own tests and see whats going on. It makes sense they couldve say used the puny cam to tame down the requirements, dorect injection does help but, even at 11:1...i dont know, i still want to do some comparisons, and realtime log it myself

 

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Definitely interested in your tests and results.

[4x4LJB]

You don't just induce spark knock at wide open throttle. .. that's not how this works. Load on the engine will make it knock... that can be at 2500 rpm or 5000 rpm... it doesn't matter. The ignition timing on these is basically non existent too... mid teens at best stock on 6.2 on the high octane table so the 5.3 is probably even less....

 

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Yup. It's load. When I last set up the advance curve on my BB Chrysler I ran as much lead and total ignition as I could pile on, headed for the steepest hill in the city, and lugged it at part and full throttle, listening for knock and pinging. Took the best curve I could with very minor pinging under those conditions, backed it off a degree, and she ran, and runs, very strong. Without pinging. Decent gas mileage, considering it displaces 451 C.I. and a 750CFM carb.

 

I tuned mainly for total advance at 2500 rpm. I think I settled for @ 36 degrees BTDC. Lead advance was @15 degrees.

 

In this:

 

[HondaHawkGT]

The I was getting burst knock on the L83 when I'd lift after a WOT run. AC on, running uphill in 90F & humid weather.

 

I had been running the truck without a catch can for the year leading up to it so who knows how dirty my combustion chamber/intake valves could have been.

 

I did noticed that upcoming engine oil standards are setting maximum levels of sulfated ash due to its tendency to induce pre-detonation in DI engines.

[CAtaylor]

http://www.gm-trucks.com/forums/topic/158431-53l-kr-during-data-logging/

 

some more reading on this subject.

[scottie350]

http://www.gm-trucks.com/forums/topic/158431-53l-kr-during-data-logging/

 

some more reading on this subject.

Very interesting read and pretty well what i had found elsewhere and was suspecting.

 

And as i stated tuners are concerned after significant logging and they " tune to 0 knock throughout rpm and load range"

 

So something isnt right, higher octane on some seems to help, but definitely seems a problem in the tuning from factory.

 

Thanks for the link bro

 

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[CAtaylor]

Very interesting read and pretty well what i had found elsewhere and was suspecting.

 

And as i stated tuners are concerned after significant logging and they " tune to 0 knock throughout rpm and load range"

 

So something isnt right, higher octane on some seems to help, but definitely seems a problem in the tuning from factory.

 

Thanks for the link bro

 

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Yea, I don't think this just affects some. They are all tuned the same from the factory, the average consumer would never know the difference.

[scottie350]

No and thats what ive been saying, what the average persom FEELS and what is actually going on is 2 totally different things, you are 100 % correct.

 

I noticed the" off" idling and certain things while driving that didny seem right, but im used to this stuff given the work with my project cars.

 

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[harveyfamily]

I'm nearly empty from the "free" full tank I got at delivery. I am going to fill up with 89 and see if there's any improvement in response and MPG.