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.

 

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

 

Sorry misread about the 40psi, thought you meant boost.

 

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.

 

Good God guys. And I get a bit uncomfortable getting my engine to 2500 rpm
-P

 

I like the way mine sounds at 4K and to see the tack 1k past red line.

 

Brandon, These guys must not know you

 

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

 

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)

 

fully balanced bottom end and a harmonic balancer designed for high rpm use.

 

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...

 

i garuntee you its not valve float he has more money in his head than most people do in there trucks.

 

JKM Sounds like 99% of pullers are running out of balance lower ends! I will not say that it is not valve float Hammer we dont know what is going on inside their but I dont think this is the problem I need these RPM's due to the fact when I start to drag a sled it will pull my RPM's down to around 3800 or so when I leave the line at 4200 or so and as the weight increases I dont know what will happen due to the fact this truck has yet to see a sled since it was just finished being built not long ago and am still playing with options, my S400 also has a nice size housing on it so my main frame of mind is to stay atop this charger if I leave the line at 3500RPM what will this do slip the clutch the whole track to stay atop the charger like I said I have a good size housing mabey their are some that leave the line at this RPM but NOT me yes I have fuel for 4000RPM Yes I have cam for 4000RPM Yes I have air for 4000RPM Yes I have valvetrain for 4000RPM Hammer in no means am I insulting your intelligence but mabey I should have made it clear what this truck was built for and putting it on a dyno was not the intended purpose Kevin as we both know some money has been put into the head yes like I said I will be putting in new injectors and bump the timing up a little more to see what will happen. PS I do not just spin this RPM to say I can and yes it is taking a risk but this is not your truck it is mine and if it is a risk I am willing to take then so be it. There is also alot of guys that take thier trucks this high in the RPM range and as I said they may do as they please as I will do also!
Brandon

 

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?

 

Yes Thank You, I wonder this also I wanted to make sure I was not the only one who thought this!!!!!!
Brandon