Dylanplace

So in the past I always played with 4.8s and 5.3s with turbo. I've since turned my 2500 with a 6.0. Running 10psi on the stock motor was good for about 2000 miles and I broke ring lands. So I pulled the pistons and rods and put a set I had the rings gapped to 28 and 30 and stuffed them in it. Had some blow by but no big deal. Was good for 3 days and broke ring lands on cyl 2 and 7 running low 10s on the afr in boost so I really don't think it's a lean issue. The pistons have some black on the center of them but are still pretty clean. Also running on 91 or 93 depending on what I can get. Any thoughts

svslow

What timing? Low 10s AFR could also be the issue. Too rich will break pistons as well.

Dylanplace

Timing around 12 to 14. I will post the log of it breaking the first time when I get home

stevieturbo

If they've broke that soon....you can be fairly sure it's a tuning issue. Although "tuning" does cover a wide range of items

And if you've got blowby, something is fucked, because you can be 100% sure it is not the ring gaps causing it.

What ecu are you running, is there anyone competent tuning it and checking for detonation etc ? And AFR's etc are accurate ?

10psi boost from what ? Under what circumstances did it break each time ?

Dylanplace

ive been tuning it myself so their is no one but people on the forum helping me
blue 10% fuelfix lean spots.hpt blue knocking.hpl this is the log from the first engine. i wasnt logging when the second one blew

Dylanplace

I guess really I didn't have much blow by till I broke so you can disregard that. Because after it happened it blew my valvecover gaskets out but I was an hour from my shop so I fixed them in a parking lot and sent it north

subeone

iTrader: (5)

what plug? br7ef?

Dylanplace

yes. Went from gapped stock to tr6 to br7ef

newschool72

iTrader: (12)

Have you checked for exhaust leaks ? The ECU will lie to you about the AFR if your introducing fresh air before the sensor. Sometimes its the simple things.

Dylanplace

That would make me richer than the wideband says then. So that wouldn't be a terrible thing. But it's tight

coltboostin

Where is the timing right before peak torque? Who cares where it is up top.


I would suggest sending a log to a reputable tuner.

SethU

Which ringlands broke? Top, between the compression rings, between the lower compression ring and the oil ring?.. any damage to the support rail below the oil rings?

If it's not the top land, or not only the top land, it could just be too much timing at the wrong time in the power band.

The quote below... I'm curious too.

truckdoug

iTrader: (25)

i'm pretty sure thats how i broke my piston. focused to much on what my max timing was.

SethU

Pretty sure I'm not saying anything you don't already know. However, for posterity's sake...

Yeah, timing advance is an interesting subject. I've been bit by it too. No detonation, yet stuff starts breaking. Stuff I didn't expect to break. Crank shafts, wrist pins (BBC stuff)... Lessons learned.

The thing I keep in mind now, that I didn't know or acknowledge in my younger years, is that any gain from additional timing advance is a net gain. Meaning, there are losses involved. But the gains outweigh the losses, producing an overall net gain.

The losses... any ignition point prior to TDC is working against the piston moving up in the bore. More advance = more pressure on the piston before it reaches TDC. In many cases, too much will cause detonation. But, it doesn't have to detonate to break stuff.

truckdoug

iTrader: (25)

I've learned that I don't know **** about ignition timing. 20 years of tuning NA carbed motors by plugs, and most of that useless now

Hell, the NA baby cammed 5.3 in my long bed only wants like 23* at peak torque. lol

newschool72

iTrader: (12)

I always back my timing off a couple degrees in what I "think " is my peak TQ area. Does it help acceleration ? who knows, but if an engine wants less timing at its max efficiency point, Im gonna try to give it what it wants . I cant see it hurting anything to do that and the MSD 6012 I use for ignition makes it really easy to do.

Dylanplace

I'm not sure where my peak torque is. It now has a 4.8 I had stuffed in it. The first engine broke all the ring lands and put the oil rings in the pan on 4 cylinders. Second engine just broke tops that I can see. I have not pulled the pistons out yet or the pan. But my ignition didn't change between the 2 engines

subeone

iTrader: (5)

Another thing to consider is timing drift. Just because you are commanding 12*, doesn't mean the engine is seeing 12*.. could be seeing 15*. That's why you :

1. Read plugs.
2. Test and Tune at the track and go solely off MPH.
3. Put it on a dyno, start safe and work your way up.

Dylanplace

I don't know much about what it should be in boost. From my log I was going from 14 in boost down to 11 on my timing.

truckdoug

iTrader: (25)

so i've just started tuning my 4.8/7875 combo but it appears peak torque has moved up from around 3500-4000 rpm with the 6 liter to 5000 with the 4.8.

i'm actually liking the 4.8 quite a bit. it's not a dog down low like I had assumed it would be. just takes another half second to light the turbo up.

where are you located?