How to tweak an Engine to get max torque at set rpm

[Nashx]

I have been using the Lotus Engine simulation software to run my engine simulations.i have been getting the maximum value of torque between 2000 t0 3000 rpm.I want the maximum torque to be occur between 3000 to 4000 rpm.How can this be achieved?Do I need to change the dimensions of the port,valve,connecting pipes or is there another option?

 

[BrianPetersen]

In short ... Yes.

I'm not going to do your work for you, but add cam timing and lift to your list of things to experiment with.

Be careful if you have intake ducts that converge to a smaller area and then diverge to a larger area, particularly right at the intake port. My experience has been that the Lotus software is far too optimistic about the amount of velocity that gets recovered as pressure.

 

[Tmoose]

http://img.photobucket.com/albums/v628/BigBlockMopar/1960ChryslerNewYorker/RamInduction.jpg

 

[Nashx]

Thanks I will definitely try out your suggestions.

 

[EDickman]

Nashx,

Are you still working on this project? If so, lets get to the definition of torque and maybe you can answer your own question. (lets work in indicated so we don't have to worry about friction)

Tq= (η[sub]c[/sub]*η[sub]t[/sub]*η[sub]vol[/sub]*Q[sub]LHV[/sub]*ρ[sub]a,i[/sub]*(F/A))/4Π

Where
η[sub]c[/sub] : Combustion efficiency ( this can be affected by timing and side wall temperatures, we can say this is as good as it can get )
η[sub]t[/sub] : Thermal efficiency ( Limited by compression ratio and coolant temps)
η[sub]vol[/sub] : Volumetric efficiency ( self explanatory)
Q[sub]LHV[/sub] : Lower heating value (fixed with gasoline)
ρ[sub]a,i[/sub] : density of inlet air ( mostly fixed with NA engines)
(F/A) : Fuel/Air ratio (self explanatory but remember, a mixture over 1.1 will have a cooling effect durring compression due to the evaporation of fuel, and other reasons, keeping compression temps down. This increases induction period and reduces end-gas temperatures at the wall causing less of a tendency to knock but also leaves unburt fuel just soaking up combustion energy.)

Peak torque is where all of these combined are the highest, makes sense with math and all. Of all the efficiencies, by far the easiest to manipulate is the η[sub]vol[/sub]. What you need to do is balance your wave energy in your intake tract with your timing of intake valve opening by playing cam timing, runner diameter ( bigger allows more air in but wave energy is sacrificed), length of runner to the plenum( longer and shorter runner lengths are going to change peak torque locations, higher engine speeds are going to need a shorter runner where lower engine speeds need a longer runner). There have also been studies about the size of the plenum, my apologies for not citing them, but as I remember they should be several times engine disparagement, 8-20x?. Also remember that while the pressure waves running around don't mind bends in the intake system, these are indeed minor losses due to friction in the flow thus increasing pumping losses, increasing the fluids speed will give similar problems so it is a delicate balance.

I hope this brief description helps you, if more detail is needed or I mis-spoke at all, just let me know. REMEMBER, this is just one efficiency, there are so many other things to be investigated.

ED