Truckers, lets see your rigs!

Mr.T said:
I haven't seen any pictures of what's under the hood, its 3 hours away from my house and I'm 10 hours away from there right now, my plan was to go look at it next week once I got home, so what does this truck need to have to identify it as a 400? Pictures would also help
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Engine serial would be best, at least that would say what it started life as, and most likely if it were a 400 not too many would change it during a rebuild.
 
RockinRam96 said:
If it looks like this it has an after cooler...

tageqyre.jpg



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Haven't seen one of those in a while. Been almost 7 years.

Squeaky Wheel
 
I'm learning all kinds of new things today! So you mechanical engine gurus, I have an idea here......say you take one of these old rigs with an air/water charge air cooler, and added an air/air on it also.....so you have your turbo, then the air/air, then the air/water......is there any advantage to that or is it just crazy talk?
 
Mr.T said:
I'm learning all kinds of new things today! So you mechanical engine gurus, I have an idea here......say you take one of these old rigs with an air/water charge air cooler, and added an air/air on it also.....so you have your turbo, then the air/air, then the air/water......is there any advantage to that or is it just crazy talk?
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That wouldn't do you any good, unless you ran cold water through the after cooler. An air to air cooler will theoretically cool the charge air to ambient temperature. Where as a an air to water after cooler (runs engine coolant through the cooler) will theoretically only cool the charge air to 180 degrees, operating temperature.


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Mr.T said:
I had no idea those were an A/W charge air cooler. Good to know!
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If you look at the picture closely you can see a dividing line. Above that is the after cooler and below that is the manifold. The after cooler really isn't that big.

I have yet to figure out the reasoning behind retarding the timing on an 855. It goes against everything I know about diesels and everything I've been taught. By retarding the timing you'll send more unburnt fuel out of the exhaust, so the added fuel does nothing but maybe burn up the turbo. I have a hard time belie sing that retarding the timing so much is easier on the pistons. In advancing the timing, the injection event happens further away from top dead center, when the piston is lower in it's stroke. Retarding the timing causes the injection event to happen closer to top dead center, so the piston will be higher in it's stroke. Therefore, retarding the timing will put the piston closer to the nozzle during the injection event than advancing the timing will. I was always lead to believe, and it makes perfect sense to me, that the closer to the nozzle the piston is during injection, the more heat there will be created in the piston. Leading to melt down. Advancing the timing would cause the injection event to happen when the piston is further away from the nozzle. Keeping heat away from the piston.

I personally believe that the scare came from drivers back in the day being uneducated and maybe driving incorrectly. I will say though what I do with the engine is completely different. I will only have that temperature in the cylinder for 15-20 seconds. Where on the road that temperature will be in the cylinder a lot lot longer.

Maybe I'm completely backwards but that's what I know and my $0.02.



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Really the retarded timing idea came from the idea of not wanting raw fuel to be sitting on top of the piston at lower engine speeds and full throttle application, so they retard the timing to help with low rpm usability. It is less than ideal for a higher rpm performance application.

Look at the MVT engines, low rpm they are around .115 and after the advance activates they go to .065 which happens to be the same as a standard 350hp big cam.
 
The reason for PT system timing retard is the way that system works, the more fuel pressure you give to it the more the timing is advanced, leading to too much advance when going too far, but only at lower rpm range. You can cruise at low rpm but when you need max power go up in rpm and you are safe even without retarding it.
 
Leiffi said:
The reason for PT system timing retard is the way that system works, the more fuel pressure you give to it the more the timing is advanced, leading to too much advance when going too far, but only at lower rpm range. You can cruise at low rpm but when you need max power go up in rpm and you are safe even without retarding it.
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Well then I'm not worried about retarding the timing. Anytime the engine is under a load it is running at 2,000+ rpm and having a 15-speed with high gear being direct, I cruise at 60 mph at 1,800 rpm.

How does rail pressure effect timing? From my basic knowledge, doesn't the cam have to be at max lift to create the injection event. Which is total dependent on cam shaft timing.
 
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RockinRam96 said:
If you look at the picture closely you can see a dividing line. Above that is the after cooler and below that is the manifold. The after cooler really isn't that big.

I have yet to figure out the reasoning behind retarding the timing on an 855. It goes against everything I know about diesels and everything I've been taught. By retarding the timing you'll send more unburnt fuel out of the exhaust, so the added fuel does nothing but maybe burn up the turbo. I have a hard time belie sing that retarding the timing so much is easier on the pistons. In advancing the timing, the injection event happens further away from top dead center, when the piston is lower in it's stroke. Retarding the timing causes the injection event to happen closer to top dead center, so the piston will be higher in it's stroke. Therefore, retarding the timing will put the piston closer to the nozzle during the injection event than advancing the timing will. I was always lead to believe, and it makes perfect sense to me, that the closer to the nozzle the piston is during injection, the more heat there will be created in the piston. Leading to melt down. Advancing the timing would cause the injection event to happen when the piston is further away from the nozzle. Keeping heat away from the piston.

I personally believe that the scare came from drivers back in the day being uneducated and maybe driving incorrectly. I will say though what I do with the engine is completely different. I will only have that temperature in the cylinder for 15-20 seconds. Where on the road that temperature will be in the cylinder a lot lot longer.

Maybe I'm completely backwards but that's what I know and my $0.02.



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The only thing i would have you consider is peak cylinder pressure and when it occurs in relation to TDC.
Retarding injection timing gives the piston more leverage over the crank, which ultimately yields lower cylinder pressure. (all other events equal ofcourse) it's easier to push a lever around an axis that is near perpendicular to the direction of force. In our case, it is easier to shove the crank throw at 45 degrees than at vertical. Resistance to expansion is pressure, and pressure in a system is directly proportional to heat/temperature.
So, the higher the timing advance and closer the peak cylinder pressure occurs near TDC, the better chance of a burnt piston.

Could be a total load of BS though :)

And leiffi has it on the PT system advancing itself.

Squeaky Wheel
 
I can say this, and do not know why. On the Dyno a 855/n14 will pull harder with the timing on the retarded. This is with everything else the same


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I do not. This is just well known at work. Some of the old timers have messed with it on the Dyno. It just standard to try to set them a little retarded. I can try getting pictures. We don't get many old engines anymore


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I'd like to see proof that less timing makes more power with an 855. It just doesn't make sense to me. Its too bad it takes so much work to change the timing in one or the cost of going to the dyno, or else I'd prove it, one way or the other.

Not that the old timers are wrong, but an old timer also told me that I'd be melting pistons down with a 0 button in my pump with all the other components being stock. Well almost none of my fuel system components are stock any more and its a struggle to see 600* on the pyrometer.

This could be a function of injectors, we shall hear that verdict today!
 
RockinRam96 said:
How does rail pressure effect timing? From my basic knowledge, doesn't the cam have to be at max lift to create the injection event. Which is total dependent on cam shaft timing.
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PT injector is always only partially filled, the more it is filled the less plunger travel it takes before injection starts = advanced timing. And vice versa. At idle timing is something like 10-15 degrees after tdc, that's why they smoke white. PT system always ends injection at same point but start varies. That is something Bruce M. don't seem to understand when reading his articles.
 
97rada said:
I can say this, and do not know why. On the Dyno a 855/n14 will pull harder with the timing on the retarded. This is with everything else the same


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Possible if too much fuelpressure and not enough rpm. I once drove a racetruck that had maxed out everything, I didn't have right gear when coming out of corners, rpm dropped too low, I had to lift the pedal to get more power because it was too advanced for that rpm and only stuttered if pedal was floored. That's a good way to test timing vs. rpm, if engine feels stronger when lifting pedal then you are too advanced.
 
RockinRam96 said:
I'd like to see proof that less timing makes more power with an 855. It just doesn't make sense to me. Its too bad it takes so much work to change the timing in one or the cost of going to the dyno, or else I'd prove it, one way or the other.

Not that the old timers are wrong, but an old timer also told me that I'd be melting pistons down with a 0 button in my pump with all the other components being stock. Well almost none of my fuel system components are stock any more and its a struggle to see 600* on the pyrometer.

This could be a function of injectors, we shall hear that verdict today!
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Where are you out of?


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