Balancing a motor

PULLINGTRUCKER?Just look at liner protrusion. This setting can be all over the board and not just vary from the front to back of a black, but also side to side. There are a couple of guys on this very message board that are fighting CAT over this problem. I think the deck will be checked if this engine gets overhauled. Cat did have some liner problems when the liner flange were checked they were all over the board. With over a million miles the block will surly need to be cut.

 

With the sort of rotating/reciprocating weight a class 8 diesel has I can't really see that working. That and the astronomical piston speeds due to rod ratio I don't understand how one could survive much more than 6,000 running without a cylinder head being spun by an electric motor perfectly balanced or not.

Rod ratio is not the same as bore/stroke ratio. Rod ratio is the ratio of crank stroke and rod length. The lower the ratio the higher the piston speed and the longer the piston sits at TDC and the better the torque output but you can't rev as high vs a high rod ratio. Not only that but because the piston speed is so high at higher rpm's the piston can actually outrun the combustion. It literally outruns the combustion flame after a certain point. On the other side of things this is often why you can't get power from a gas engine that revs to 7000rpm. Why? Because high reving engines have higher rod ratios. The piston is moving too slow at lower rpms and the flame smashes into the piston almost like detonation (or pre-ignition) and puts a lot of load on the engine. This is the lugging/shuddering feeling you get in a small car with a manual transmission when trying to climb a hill or accelerate at 1400 rpm. With high pistons speeds comes high forces on the piston from changing direction very fast, combine that with the weight of a Class 8 piston and you're asking a lot from a rotating assembly being spun at over 4 times what it was designed for.

I'm not saying I don't believe you I'm just saying I would be really impressed with a class 8 or any production diesel engine that could spin to 10,000rpm. Even the Audi TDI LMP1 race car that uses a 5.5L V10 Turbo Diesel only spins to around 5 or 6,000rpm.

I would love to be wrong about it and hear all about it it's just that I can't imagine it. I'm not being sarcastic about that either.

 

Most high performance diesel pulling motor spin around 5-6000rpms with really minor problems (until something goes a little out of whack, then a big problem follows).

 

Those would be highly modified rotating assemblies I assume and 5-6,000 is not 10,000. Maybe 10,000 is a hypothetical number that the assembly would be balanced to run to IF it could run that high? Any info to those truck pulling motors? I find them to be #### interesting.

 

Pittsburgh power has a balancer made by centramatic that goes behind the damper

 

PP balancer is made by Balance Masters, not Centrimatic. The balancer is a good product though. I installed it last Saturday with no trouble at all (besides the motor being hot...not my brightest moment...). So far I have put about 1000 miles on the truck and have noticed a difference. First thing I noticed was at idle my mirrors didn't vibrate, next was when I went from idle to high idle (900-1000rpm). Usually I have a little shudder around 700rpm...its gone. Also the motor is smoother all the way through the rpm range. So far I am very pleased with the balancer.

 

I think it is made by Balance Masters. Centramatic uses the little ball bearings in oil and Balance Masters uses mercury. Not sure if one actually better than the other. Either way, the balancer is a good idea. This fall I am going to replace the crankshaft dampner and also install the crankshaft balancer when I have the overhead run. Should go a long ways to making the engine real smooth.