What Is The Most Boost These Engines Can Handle??

[Woody35]

1800-2000 rpm is where peak torque is. i always accerlate the fastest when the tq converter is locked up at 2000 rpm. then by the time 2800 rpm has hit the turbo is out of efficency and it just makes a bunch of noise and stops accerlating as fast

 

[buddy]

With 3.42 gears Im down around 1500rpms a lot 45-55mph. It seemed like there was a bogging feeling and what seemed like a small battle to maintain the right fuel rate to stay in OD, cutting then adding fuel. I advanced the timing a bit in that rpm and fuel range and it got much better. I manage to maintain OD at 55mph going up hills below 2000rpm at like 5psi boost.

 

[Woody35]

yeah for me i have to downshift all the time at that range. i just usually slow down without downshifting and gain back the speed at the top of the hill

 

[buddy]

I dont like slowing down, but the truck and my wallet would probably appreciate it. It hums right along really well under load though.

 

[Woody35]

i just worry about the tranny always downshifting since it has 150k miles on it. cant be very good for it

 

[buddy]

I programmed my PCM so it wont downshift when I dont want it to. That way I maintain OD all the time on the highway pretty much.

 

[schiker]

Bogging or lugging which is the problem????

Right or wrong ??? I've always kinda thought ....

Lugging I consider around or under idle with load and fuel near matched lower fuel low rpm chugging like launching a manual or just enough fuel to pull the load where light fuel and load is worse. And or when power strokes of cylinders is just a bit stronger than compression stroke of other cylinders. I think this causes the worst harmonic because the load on the crank are almost closer to equal but kinda opposite or at for a brief time it approaches back to zero load/power/compression pulse and it alternates worse. The twist torque amplitude varies and the frequency is low.

Bogging lower rpm but with heavy fuel. The power stroke is doing work and the alternating load on the crank is not equal or compression vs power stroke is not equal. So I think the crank is more steadily loaded constantly twisted. Not as harmful ????? Its just the frequency of power pulse is less but but amplitude of torque is same.

 

[schiker]

Let me try to say that again slightly different.

Bad is lugging: Where there is near equal compression - power - (light load near stalling) psi in cylinder varies considerably. The pop from combustion peaks and accelerates the piston. The amount of pressure on the piston crown lessens significantly as crank rotates down and almost free wheel decelerates for a bit as too compression near stops it on another cylinder then bang the combustion pops peak loads another cylinder and other cylinders the pressure is low. You'll feel a lot of engine vibration/rotation variation.

Not so bad Bogging: is where you are loaded and giving it plenty of fuel but rpm's are just low say anything over 1300-1400 less than 1700 rpm. Here there is plenty enough fuel burn to still have significant positive pressure on the piston down force through the stroke. This is diesel torque and feels slightly different as diesel burns a bit slower and is fuel metered in the cylinder such that pressure lasts longer than a gassers pop and done from spark and much more dependant air/fuel ratio. As gassers don't have the high compression they don't get the same piston heavy "over cam" sensation and piston pressure power spike to keep the low load rotation going.

 

[Matt Bachand]

You can drop it into 3rd from OD. I just take foot off the throttle for a split second, drop it, and TC in unengaged, then enganges. I'll shift into OD without removing foot off throttle.

I'm pretty sure I've dropped it from OD to 3rd without foot off the app. It seems its more of a computer commanded shift than a physical shift.

I do this all the time. 30k on the rebuild tranny. I always drive in 3rd until doing 55-60. Then drop OD.