6nz"d BXS Acert thumping noise

1st hand experience messing around with timing. Slightly retarded timing will pull way better than advanced timing.

Pulling timing away will decrease hp but adds torque and boost. Your egt will run a bit higher but that's better than having excessive cyl pressures.

Adding timing will see an increase in overall HP but torque will actually decrease torque and will lose rpms quicker on a pull. And if your running with bumped up timing do not lug it.

 

Your gonna be pulling it apart again with those 18: 1 packs and that tune.

 

Brettj3876: I hope not. There’s a few things I’d like to try that I’ve applied to other engines I’ve worked on when I want to make more power on.

The tune itself wasn’t the reason for the head cracking which is why I’ve taken it apart.

Besides, I’m always hearing stories as well of people going single turbo and still taking their engines apart.

 

The ACERT engine runs on the Miller operation cycle.

That’s why they use Intake Valve Actuation.

The IVA makes the intake valves stay open just a little longer which forces some pressurized air to go backwards into the intake during the compression stroke. This makes the engine more like a 16 to 1 compression engine for example.

This is Cat’s way of making EGR work without the egr cooler. It’s supposed to make the engine be 15% more efficient while being cleaner.

The high compression compensates for some of the charge being forced back into the intake.

The small turbo prevents the intake charge from going too far by pushing back.

 

If I remember right, the low compression packs are around 15:1.

The 2 Pete’s we have with the 3406b’s are 16:1 and 16.7:1.

So when someone re tunes the computer, turn off the IVA’s, the cylinders are now taking the full force of 18 to 1 compression along with the boost pressures of 40 plus psi of the two turbos or the single.

I think my ACERT is pushing around 45-50 psi with the twins. The boost gauge says 60 but I’m not sure if that’s accurate.

 

I bet they pull some timing out to compensate for higher comp? @Superhauler the guy to ask

 

More than likely when it was a twin turbo the vva's bleeded off the excess cylinder pressure even though it showed better than 40psi on the gauge. Because of the high comp pistons. Now when it was singled the vva's were removed or deleted so they couldn't "bleed off" the excess cylinder pressure. Which causes higher cylinder pressure with the single and high comp pistons. Its not "if" the headgasket will fail. Its "when" it will fail. Either cut the bowel of the pistons or install the low comp pistons.

 

Shafts break from compressor surge. Not overspeed. Barking the turbo . Lifting off the fuel pedal too fast under a heavy pull will do this sorta thing. You can't drive like a cowboy when your pushing some HP. Ease on/off the go pedal and the truck will thank you.