Big Cubic inch Cummins

"So you’re willing the trade air flow, as in small base circle cams for cubic inches you can't feed now.

Besides the base circle on the cam is not the place the rod hits, it’s the root of the cam between lobes. this would be a very weak cam "

A small base circle cam doesnt limit airflow in any way that i am aware of (if that were true the gassers woulda quit doin it a loooooong time ago) - it just changes where the lobe sits on the centre axis for clearances, as well as providing the means to do regrinds
It may be hitting between the lobes on a 5.9 but thats not true in most engines

Greg - I have no argument whatsoever with your airflow statements - they are all accurrate, and so are your stroke/ bore statements

However I will always be a proponent of higher lower rpm tq numbers than i will be of high rpm hp gains - if yur tearin up parts - make em stronger

Hp is only a function of torque not the other way around - thats why diesels excell in haulin stuff around.

I think one of my earlier statemnts will hold true - it will nto be in the too far distant future where the only difference in the performance world between a diesel n a gasser is the fuel they use - we are almost there now
 
seeker1056 said:
"So you’re willing the trade air flow, as in small base circle cams for cubic inches you can't feed now.

Besides the base circle on the cam is not the place the rod hits, it’s the root of the cam between lobes. this would be a very weak cam "

A small base circle cam doesnt limit airflow in any way that i am aware of (if that were true the gassers woulda quit doin it a loooooong time ago) - it just changes where the lobe sits on the centre axis for clearances, as well as providing the means to do regrinds
It may be hitting between the lobes on a 5.9 but thats not true in most engines

Greg - I have no argument whatsoever with your airflow statements - they are all accurrate, and so are your stroke/ bore statements

However I will always be a proponent of higher lower rpm tq numbers than i will be of high rpm hp gains - if yur tearin up parts - make em stronger

Hp is only a function of torque not the other way around - thats why diesels excell in haulin stuff around.

I think one of my earlier statemnts will hold true - it will nto be in the too far distant future where the only difference in the performance world between a diesel n a gasser is the fuel they use - we are almost there now
Click to expand...


Oh boy.

:D

Power determines everything you think torque does. Because power is what determines the torque to the ground where it's useful for things like driving the truck forward and dragging heavy loads over mountain tops instead of things like blowing rods through the oilpan and twisting off input shafts like it does when you try and make too much of it at the crankshaft.

If it's lower rpm torque you so desperately desire, go get yourself setup with a steam engine. They make copius amounts of torque. Like 10,000ft/lbs on a bad day kind of torque. Course, even a fairly big steam engine while making all that torque, will only make around 100 or so odd hp because they're spinning so slowly. And whether trying to pull a grade at 50mph or crossing the traps at 150mph it won't put much torque at all to the ground, which is the only place it matters.

What you've confused with torque of a diesel making it so capable, is actually powerband. A diesel will usually have a much broader powerband than a comparably powered gasoline engine.

If you don't make the power you're not going to get it done. Engine torque is a meaningless value. It tells you nothing more than how much stress that poor engine is having to endure. Which is precisely why it breaks sh*t just like was stated above.

You want the torque at the ground, not the crank. We've got gears for that.

If torque was all you wanted, why don't you just stick the truck in low range? That more than doubles your torque. Does it not?
 
Make sure if anyone is building a big cube motor that the cam (even billit cams) don't have a fuel pump lobe on it or when you are rolling the motor over it will hit the fuel pump lobe on the cam. lol
 
seeker1056 said:
So I guess Mr Watt doesnt know jack
Click to expand...


Actually ole James had it down just fine. And being that everything I posted was perfectly inline with his thoughts on the subject it makes your above statement pretty retarded.

Maybe you'd like to visit one of the zillion other threads on the subject as I'm sure they can more than quench your thirst for knowledge.

Lets leave this one for the guys wanting to tie both arms behind their backs by increasing their engine displacement in classes limited by airflow.
 
Do you even know who Mr Watts is Charles.

I do however agree with the limited airflow/bigger cubes issues - doesnt work
 
First with any thoughtful engine program, it’s all about airflow. With diesels the higher the rpm band you achieve maximum air flow the more hp you achieve. Higher RPM also has a benefit in that cylinder pressure and torque is reduced, thereby reducing the load on the drive train, and helping to keep the cylinder head on. Bigger engines draw harder on the cylinder head, and bump up low end power. A bigger engine also maxes out the available air flow to the cylinder head at a proportionally lower RPM. This means you will make less hp up high.

In pulling its about making maximum hp, this hp is translated in to wheel speed, and torque thru gear ratio. Hp is the only measurement of power, it’s how much you have to use. Like the example earlier, a 100 hp steam engine at 100 rpms make 5200 ft lbs of torque . Try using that torque.
A 800 hp 10,000 rpm small block with only 300 cid makes about 500 ft lbs of torque, but with a 3.25 first gear ratio, and a 5.00 rear gear ratio puts 8125 ft lbs of torque to the ground at the axle
The reason for the big bore block is to put bigger valves in the head, this is airflow.


Now is you had a magical cylinder head that would flow twice what the best Cummins head out there makes then bigger displacement would make a difference .

So my goal is the biggest bore, and the stroke that will match the intended rpm range as far as airflow.
 
just to let everyone now it wasnt a 5.9 in shane kellogs truck at the end of last year, it had a few more cubes and that thing was a rocket
 
custom diesel said:
just to let everyone now it wasnt a 5.9 in shane kellogs truck at the end of last year, it had a few more cubes and that thing was a rocket
Click to expand...

Who said any of the super stock trucks had stock 5.9 CI? I'm sure a couple do but definately not all.... Or half....
 
specing out a Cummins drag engine For a light weight chassis.
First let me explain the difference between the engine program that works for most in a 7000 lbs truck, and why is you put it in a light weight dragster, or chassis. Everyone always assumes that if you take a fast truck engine and put in in the frame rails of a dragster and whamo, you could easily go in the 7’s.


Then you see these people work for a long time to even get in the mid 8’s. Everyone is of the opinion that if you take a mid 10 second truck that weighs 7000 lbs and take off 4500 to 5000 lbs you there.

Problem is that in a heavy truck you are not asking then engine to accelerate, REVGAIN. In a light weight chassis, you’re now asking this engine to RevGain at twice to 3 times the rate it once had to in the truck.
Next is airflow, in a 5500 rpm engine the intake valve opens 45 times a second. Now the with one of my biggest cam designs , when the valve opens .615 on a CR engine , the duration at .200 lobe lift , the point where air is really starting to flow is around 120 degrees , that means the valve is only open 1/3 of the intake revolution . You see the math


So you can't feed the displacement you have now, all a bigger engine will do is pull the torque peak down, to a lower rpm. Torque is cylinder pressure, and cylinder pressure is what breaks things, and want to escapes past the combustion containment systems (head gaskets, rings )


Focus all of the money on airflow, don’t spend money of making an engine bigger, spend it on cylinder heads, advanced cam programs, and intake manifolding.


So to a Cummins drag racing engine program
4.310 bore ,
1.470 intake valves
4.25 stroke, Duramax rod journal, Duramax wrist pin, this will take 1200 grams, toss in a GRP aluminum rod , and your at 2000 grams of weight savings .
This motor will have to be a CR , in that the tune has to kill any torque down low, until the engine get up to 4000 rpm’s
 
You must log in or register to reply here.
Back
Top