ddnspider

iTrader: (26)

NP man, hope you get it fixed and boosting again soon.

Game ova

It's possible he did. But it's also possible the motor was in a flex fuel vehicle, and the owner always used E85 which keeps pistons clean.

80/TA/LT1

iTrader: (2)

Update, i have a 06 5.3 with low oil pressure when it gets warmed up. Talked to my local engine builder whos been around like 50 yrs, he's gonna do all the bearings and give it a once over for me. Also spoke with my tuner who saw the pics of the pistons / plugs and agreed it was definately a lean condition, thinks an injector got stuck. I just had them flowed and cleaned, but who knows its possible. Probably gonna buy a new injector for that hole before i run it again just to be safe.

Game ova

Be very careful with those old head engine builders. They come from an era where they believe everything had to have 14:1 compression, and usually just have a mindset in general. And while it's true there could be a bad injector, I'm giving this tuner and the injector theory the side eye.

ElQueFør

Spider, what part of lean AFR are you talking about from his tune? You're talking about the 12.78 AFR from his PE table rather than 11.76 AFR from his boost enrichment table right?

As far as the engine being clean looking... When I first laid hands on my first LS engine, the 6.0 that's in my truck now, I went into it with the old mentality. Having come from SBCs and flathead Fords I started tearing the LS down..... I got the heads and pan off and was amazed that a 200k+ mile work truck engine looked as perfect as it did.. No carbon buildup, no sludge. Still crosshatch pattern in the bores...... I didn't touch anything on it, just put it back together with LS9 gaskets and ARP bolts and it's now happily rip-snortin around to the tune of 8 PSI from the huffer.


And I agree with Game ova and share his general skepticism...... Too many people messing with these LS engines that are WAY too entrenched in their overall though process of yesteryear.

If theres any doubt on your injectors a simple visual confirmation you can do at home is pull the rail up from the intake and hit each injector with 12 volts and you can see if there is a problem injector that way. A flow bench is the best way obviously but if an injector is bad enough to cause a problem like suggested you'd likely see it there.

80/TA/LT1

iTrader: (2)

Game ova

Quit putting faith in the guy. For what he's charging you, you can probably buy the software and do it yourself ( now and in the future). No one will EVER care about your equipment the way that you do.

ElQueFør

^^^^ Truth ^^^^

ddnspider

iTrader: (26)

No I'm talking about 11.76. No way I would run that much boost at 11.76 AFR on pump. Its funny to me that your tuner said its definitely from it being lean.....I agree, because of the commanded AFR in the tune lol.

ElQueFør

Almost like he ran it lean on purpose so he'd have to come back for more "tuning services"


Spider: On 91 pump gas, what AFR would you like to see on say 5 PSI? and then 10 PSI, and then 15 PSI??

I've been looking around for like a chart showing ideal AFR vs boost PSI using 91 pump gas. Can't find any such thing.

stevieturbo

There is no generic answer....it will depend what each engine wants...or is limited by. ie CR, charge temp ( even at 5psi ) etc


At low boost you could easily run it into the 12's, but as always the correct answer would be whatever it makes the best power/torque with that keeps you safely away from knock or excessive EGT's etc which requires testing on a dyno.

As we all do not have access to that, it's fairly hard to go wrong around 11.5:1 or so, but you could easily run down into the 10's if you wanted, just a case of trying and seeing what the engine likes

ddnspider

iTrader: (26)

I can't imagine the guy would intentionally put a tune in it that would blow it up. Don't know the tuner from Adam (can pm me if you want). Seen more than a couple tunes from "pro's" that all lacked in some area.

****WARNING- These are my opinions. People can argue until the cows come home. Something different may work for you, but this is what works for me*********

On 91 octane no meth I'd be a little concerned about running 15 psi period, but if you're going to do it you need to keep timing down. You may only be able to run 10-12* on your setup period. I typically tune for 11.2-11.4 AFR on 93 octane between 5-15psi and drop the timing depending on how much boost is going to be ran. 8 psi, sure put 15* in it and read the plugs. 15 psi and I would start at 10* and read the plugs, especially on 91 octane. All setups are different, but usually the power gain on pump gas from 11.2-11.7 isn't a huge change but cools the cc more with the extra fuel. The low timing is what keeps them alive.

We accidentally hit 19 psi a couple weeks ago in a ~9.4:1, 5.3 with T76 93 octane only and no damage. That setup maxes out at 14* and starts pulling timing at any IAT above 122*F. Conservative? Probably. But I haven't hurt a motor yet.

BCNUL8R

iTrader: (2)

ElQueFør

Right on thanks for the info on boost vs AFR guys. Been targeting high 10 AFR under boost with my setup lately just becuase I'd rather waste a little gas, sacrifice a little power and maybe foul some plugs rather than push my setup too hard.

91 is the highest octane pump gas available in my area, at least that I've found.

I'm taking away a lot of good info from this thread myself. Richer AFR may sacrifice a bit of power but helps cool the combustion chambers. And more conservative timing may also sacrifice some power but will keep detonation away.


Yeah man, take the plunge to tune it yourself. You seem like a smart enough guy that you could get the basics figured out pretty easily. Then the nuances of dialing it in for reliable boost we can help you with. Well more so THEM than me lol, I'm forever the pupil. I've been doing ok myself just by trying to err on the side of caution and asking a bunch of questions. There is a lot of first rate talent in this thread and I'm thankful to be a part of the family of LSx turbo nuts.

80/TA/LT1

iTrader: (2)

Ok, more news, i think i found the issue here. Upon teardown inspection i found a cut fuel injector o ring in the #7 cylinder that was leaking onto the intake pretty good. So... I'm thinking under boost as fuel pressure was rising i ( 1:1 regulator ) the leak got worse and caused a lean condition. I swapped my injectors at the shop before tuning and when i initially primed the rails there was a leak, i re seated the rail and the leak stopped, but that was when i cut the oring, as they were new at that time. I'm thinking that was my problem. What are your thoughts? Makes sense doesn't it?

truckdoug

iTrader: (25)

i mean thats as plausible as just running on the edge timing and afr wise. it's hard to do a root cause on a blown motor that isnt shut down immediately.

best practice is to eliminate as much stuff as could have led to it. checking all the orings is a good start

LLLosingit

iTrader: (4)

Hate to break the news to ya, If the old head engine builders were good back then they are likely as good or better now. Absolutely NOTHING has changed with these engines since the 1950's and most concepts used well before that still apply today. The only difference is tuning is done with a computer instead of hand tools and machining and technology in general has made it easier to make better parts.
My uncle is 77 years old and still gets calls from people all over the country asking him questions when they need another opinion and he can still tell you what an engine is doing no matter how it gets fuel or how timing is set. It's still the same. Think about this for a second, You can take a new LS3 and put a distributor on it and mechanical injection and make the same and in some cases more power than you do with modern electronics.

DietCoke

iTrader: (18)

you used a 2 step with a hyper piston? lol.

truckdoug

iTrader: (25)

lots of us using an spark based rpm limiter & timing retard on SBEs to stage and spool on the line

no problems to report here (well except the lingenfelter box is a POS)

i'm sure if you stood on it forever you'd break some ****. but really it isnt increasing cylinder pressure any since most of the energy goes out the exhaust due to the timing retard

80/TA/LT1

iTrader: (2)

Ok fellas update time. The macine shop called me with bad news, said i spun a main bearing, it will need a line hone, among other things to the tune of $1100 and they are still not sure if this will fix my issues. I told them to suck it cuz i can buy 3 of these engines for that money. They then proceeded to tell me i owe them $200 for looking at my engine. Whatever. I called a buddy of mine and promptly picked up an 06 5.3 with under 200k from a rollover van. I spent the last few days stripping this engine down as well as my original to get my sloppy stage 2 cam out ( thank god its fine) everything is looking good so far. So i'm gonna pull the pistons and gap em, pop the cam in and put my heads on while waiting for my converter to come in. We'll see if i get it right this time haha fingers crossed, 4th times a charm right???