The Game Plan:
When looking at this car I wanted to develop the most efficient system possible. I want to make more HP and TQ than any other forced inducted SRT at the same PSI (6-7psi). Ideally I want this system to function at it best in this level with room to grow. This is the reason for the ginormous turbos. The 60-1 wheels are great air movers @ low PSI levels, specially with the smaller TO4-B compressor housings. I wanted these turbos to be internally wastegated to reduce plumbing and chances of exhaust leaks, so I opted for the Mitsubishi turbine housing with a .55A/R. Combined with a p trim turbine wheel these turbos should be @ full spool easily by 2800-3000 rpm and not have any surge issues. The Chart below is the compressor map for a 60-1. I plotted a small line to represent where one bank of the 6.1L sits. The pressure ratio @ 6psi is 1.4PR (14.7Atmosphere+6PSI/14.7=1.4Pressure Ratio). 3.05liters (half a bank)x 6400 RPMs x 88 (guessed volumetric efficiency) x 1.4PR /5660 = 424CFM. Divide 424CFM/14.2 =29.9lbs/min or round up to 30lbs/min. So half of our engine @ it's highest RPM flows roughly 30lbs/min @ 6psi.
You can look at the compressor map below and see on which island the engine will flow at. You can also use the same math above to increase/decrease boost and RPM to determine different senerios of the engine.
(The plot below is for 8psi)
Well now that I have the turbos down, lets move onto system design. I have always been tought that to acheive peak system efficiency you must reduce system volumes. The factory manifolds on the SRT 6.1 are excellent. I chose to make the shortest jumper tube from these manifolds to the turbos. More or less the turbos are going to be placed where the cats are now. From there I am running a 2" chargepipe from the turbos up the firewall where they will merge above the driver's side valve cover. This is the perfect spot for the Blow Off Valve (BOV). This is some thing that bugs me: Improper placement of the BOV. I was tought that the BOV should be placed as close to the turbo as possible. By doing this you directly divert the reflecting pressure wave away from the compressor and you blow off hot/pre- intercooled air thus stalling the already cooled air in the intercooler. This way when you stomp on the pedal again you get cool air.
Speaking of intercoolers I love Liquid cooled or L/A intercoolers. Did I mention that water has 14x the capacity to remove heat that air does. Also L/A inetcoolers are generally smaller and enable you to place them closer to the throttle body and turbos, thus reducing system volume. The most important factor to remmeber when designing a L/A intercooler system is to size the heat exchanger properly. You want the majority of the coolant in the system to reside in the heat exchanger where the coolant will be cooling. This removes any chance of heat soaking that everyone associates with these systems. For this reason I have chosen a
2' x 1' x 1" heat exchanger
So far that is the game plan and it looks like I might be able to pull it off.:towel:
