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.
6nz"d BXS Acert thumping noise
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by w9l, Jun 29, 2020.
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Roberts450 Thanks this.
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.
One thing I don't understand is how a basically stock Acert with compounds can make well over 40psi boost with no ill effects and at 18:1. But put a single on it and at 40psi you are gonna have a wreck. It already had excessive blowby before it was singled. I now think the guy that singled it knew it would let go so he could inframe it. Does have 6nz head now and industrial cyl packs. I don't remember what the cr is on those.
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.Last edited: Jul 2, 2020
Reason for edit: More infow9l, Brettj3876 and pushbroom Thank this.
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.
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Brettj3876, AModelCat, w9l and 1 other person Thank this.
- Jan 30, 2010
It now has the low compression pistons. BW 1496988 blows about 40psi. That turbo is supposed to support 750hp. I am not close so how did over speed it and break shaft? I notice boost gauge needle bouncing 2 or 3 psi when in a pull. Seemed to correspond with thumping. My thoughts were if one cylinder is hitting harder than the other 5 it would be likened to 5 ping pong balls hitting the drive side of turbo followed by a baseball on the 6th? Hammer the turbo to catastrophic failure?650cat425 Thanks this.
Brettj3876, spsauerland, Shawn2130 and 4 others Thank this.
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