STOPS pulling hard after 3800 RPM????
#16
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if it is still making tons of smoke at 3800 then you have plenty fuel, it may need more timing and or more air. I'm sure you do but you do have the HD springs on intake and exhaust? Valve float will limit your rpm like j-fox said. Also is the 40psi were it is limited to or just all its making at that rpm? Could have an exhaust leak that is keeping it from spooling higher. What turbo and exhaust housing are you running? Your sig is a little vague.
#17
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40 PSI is fuel pressure at idle nothing to do with boost pressure I know that I need to see what it is at the higher RPMS but my truck is tore down now so...., I seen boost in low 50's which is where it should be anything over 60 PSI or so would cause drive pressure issues, my smoke is not all that at 3500 and up, I have no stop for my tach and the otherday had it pointing down almost, I am going to bump timing to 24* put in 5x.018" sticks and hold it to the floor again and see what happens, no exhaust leaks and .9 A/R which is like 17-19 housing, my truck has no rear end in it now due to swapping gears so when I do get it back up and running I will post somemore of what I find out. Yeah the sig is pretty bad but yes I got springs with lots of other goodies also .
Brandon
Brandon
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What turbo are you running? Is it wastegated? or do you have an external wastegate? If not, if you are turning that kind of RPM, i bet your exhaust pressures are crazy. I would get a cheap boost guage and get a copper boost line to put in the exhaust manifold. If you can drop your exhaust pressure it'll help RPMs and EGTs.
#23
Valve float???
Let me start this off this way....
While I do realize that some do run the space orbit RPM's band,a 12v is so far beyond its efficency range at that point its amazing.I have yet to ever see a 12v motor make any power above 3200 and once that line has been crossed it usually just heat made,not power.I have had some strong running 12v's at my dyno shows over the years,but,one thing remains a constant,power above 3200 is falling fast,no matter if its twins or a single.
All the camshaft in the world will not help you up there unless you have the rest of the components to minimize valve float.Once the motor goes into valve float the only way it will stop is to allow the motor to come back to an idle.I feel this is where the people who make camshafts for the 12v crowd fails miserably.Instead of making a camshaft which will pull hard down low into the middle,so max power can be made down low which will elevate the torque numbers greatly,they make them to pull from the middle out.Thats where the 12v motor wants to nose dive and not make power.
When you did all this work did you think of what rpm you wanted and match the cam,fuel mods and injectors?.Because if you didn't all you did was cause yourself to need to spend again to make it right,trust me I can show you the pile of reciepts I have to back that up.......Andy
#24
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How do you make these motors survive running that rpm from what I have read the start to come apart above 4200.
from Dodge Ram .org
* Destructive torsional harmonic resonance occurs at 4100 RPM
* Crank and rods fail at 5400 RPM (if you make it through 4100 RPM)
from Dodge Ram .org
* Destructive torsional harmonic resonance occurs at 4100 RPM
* Crank and rods fail at 5400 RPM (if you make it through 4100 RPM)
#26
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Ya'll oughta be careful , I had a self proclaimed cummins expert tell me just the other day that anything over 3000 rpm, or any performance modifications to increase stock HP numbers would " over torque" the crank , and cause it to go out of balance...
#27
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Ding,Ding,Ding,Ding!!!!!!!...We Have A Winner!!!!!!!
Let me start this off this way....
While I do realize that some do run the space orbit RPM's band,a 12v is so far beyond its efficency range at that point its amazing.I have yet to ever see a 12v motor make any power above 3200 and once that line has been crossed it usually just heat made,not power.I have had some strong running 12v's at my dyno shows over the years,but,one thing remains a constant,power above 3200 is falling fast,no matter if its twins or a single.
All the camshaft in the world will not help you up there unless you have the rest of the components to minimize valve float.Once the motor goes into valve float the only way it will stop is to allow the motor to come back to an idle.I feel this is where the people who make camshafts for the 12v crowd fails miserably.Instead of making a camshaft which will pull hard down low into the middle,so max power can be made down low which will elevate the torque numbers greatly,they make them to pull from the middle out.Thats where the 12v motor wants to nose dive and not make power.
When you did all this work did you think of what rpm you wanted and match the cam,fuel mods and injectors?.Because if you didn't all you did was cause yourself to need to spend again to make it right,trust me I can show you the pile of reciepts I have to back that up.......Andy
Let me start this off this way....
While I do realize that some do run the space orbit RPM's band,a 12v is so far beyond its efficency range at that point its amazing.I have yet to ever see a 12v motor make any power above 3200 and once that line has been crossed it usually just heat made,not power.I have had some strong running 12v's at my dyno shows over the years,but,one thing remains a constant,power above 3200 is falling fast,no matter if its twins or a single.
All the camshaft in the world will not help you up there unless you have the rest of the components to minimize valve float.Once the motor goes into valve float the only way it will stop is to allow the motor to come back to an idle.I feel this is where the people who make camshafts for the 12v crowd fails miserably.Instead of making a camshaft which will pull hard down low into the middle,so max power can be made down low which will elevate the torque numbers greatly,they make them to pull from the middle out.Thats where the 12v motor wants to nose dive and not make power.
When you did all this work did you think of what rpm you wanted and match the cam,fuel mods and injectors?.Because if you didn't all you did was cause yourself to need to spend again to make it right,trust me I can show you the pile of reciepts I have to back that up.......Andy
#28
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Brandon
#29
Would the gear you are trying this in have an effect? It might do fine with the wieght of the sled back there. Maybe because it doesnt hae a load on it cant fuel enough past 3800?
#30
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Brandon