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RCTS Twin charged Lotus Elise

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News Flash from RCTS!


I'm so excited about this project, that I had to share some of this technical stuff under the hood...errr clamshell of this Lotus. :)


The Supercharged and Turbocharged - AKA Twin Charged Lotus Elise is one of the nuttiest cars we've ever built! We have been working on the final touches on this project, as well as we could see Emmanuel Crouvisier and RCTS taking a run at the One Lap of America 2012.


From my research only four groups of Engineers have ever done any project like this in the past automotive history. Lancia, with the Delta S4, Audi with the new four cylinder 1.4 twin charge four banger, Nissan's March super turbo, HKS's MR2, and last but not least RCTS Canada R&D Inc. I think our's is the coolest one :D


Look at this dyno partial test run where we now have 5 outputs from the F-con Vpro 3.3 controlling the Supercharger to Turbocharger phasing. The two data log vertical lines, (one solid, and one dotted) show how much boost the car will make right away at low RPM via the supercharger. The dotted line shows how high the boost went after fuel cut point.


See this log file below, it shows how the supercharger removes all the turbo lag at any point in the power curve. When the turbocharger pressure becomes higher than the peak pressure of the supercharger we turn off the supercharger and go to turbocharger pressure only, using the RCTS developed turbo phase inverter valve system. We control this with the HKS V-Pro engine control stand alone ECU, using most of the available HKS F-Con V-Pro output switches and output map control functions. This is the best ECU available for this type of work.


Run shows how fast the engine will hit a 1.1 bar fuel cut! Pink line is boost pressure, red is RPM.




The following pictures show some of our HKS F-Con V-Pro control outputs for the supercharger to turbocharger phase control.


HKS F-Con Vpro output switches are used # 1, 6, 7, 8 and 9 are for supercharger boost inverter valve control, map control supercharger off control and intercooler fan control.


What controls we are using and why;


#1 is SC off via {vpro NVCS control output} used to shut off the supercharger based on upper RPM limit with Injection Pulse Width threshold control

#6 is SC on via {vpro pump 2 control output} used to keep supercharger off at idling, on capability only between 1100 rpm up to redline with throttle percentage threshold set at 30%

#7 is Intercooler fan on off via {vpro temp fan 2 control output} used to turn on intercooler fans based on engine temps (because its still cold here I have them set to not come on, so I can hear engine)

#8 is SC - turbo, phase actuator valve via [vpro duty cycle map-rpm axis] using (Supra TT pressure tank & solenoid) used to open phase inverter valve with a map pressure versus RPM map allowing turbocharger only flow to engine. Anywhere a 0 is located in the map below, the SC can run, where 100 is located SC can't run and boost inverter valve is open to allow Turbo only operation.

#9 is SC clutch off via [vpro duty cycle map-rpm axis] used to turn off supercharger based on rpm and manifold pressure map axis below where




In the map below you can see that the axis is manifold pressure and rpm, anywhere there is a 0 in the map the supercharger can operate as long as throttle, injection and rpm limits set on other output's are met.





Example of the switches used for option switch 1






This run log and next picture of the dyno data, are an early low boost turbocharger only (no supercharger running) test run with reduced timing and rich air fuel shows how much power the engine makes on the turbo alone, 265 RWHP, notice the turbo lag below indicated by the solid vertical data point showing 3812 rpm before the turbo spooled up






The red line in the graph below is the actual dyno run data represented in the HKS V-pro log data in the above graph. As the red run is only via turbocharger boost with no supercharger turned on it demonstrates the actual turbo lag when no supercharger is utilized. Apparent in this red run is the nice 265 RWHP low boost run on Shell 91 octane fuel. Notice that the run in blue below the red run, is done at the same boost setting and tuning, but we allowed the TTE supercharger to run the entire way to redline keeping the TTE Supercharger's magnetic clutch turn on the entire way. You will notice why we will not do this, you can see how much horse power is wasted driving the supercharger when the turbo has taken the boost pressure above the peak SC only pressure of .4 bar boost] The belt drive TTE SC robs the engine due to its pumping losses when the turbocharger pressure is higher than the base SC pressure, causing a loss of more than 30 RWHP because the supercharger is dragging along under the turbo.







Now this run shows what happens when we shut the supercharger off when the turbo has lit up based on the thresholds listed earlier. We are still not really tuning for peak power, the tune at this point has timing well retarded and much richer than the final tunes that we'll be doing on the next morning on the dyno. The little jags in the run are cause by a pressure wave in the waste gate control, we have fixed this on the runs this morning shown in the first log run in this email.


Even so this car is going to be the fastest car we have ever built, look at the torque and hp in this little 1700lb Lotus. It's looking like 350 RWHP will be easy to attain with this setup with low boost pressures, and remember with no turbo lag simply.... Insane!


With the supercharger phased off electronically using the HKS Fcon Vpro, we now have all the power recovered and an amazing result for a 1.8 toyota engine in a lotus Elise, keeping in mind we are not really tuning the engine yet for peak power output, our concentration at this point in the tuning area of the cars development is for the supercharger to turbocharger phasing control. Final HP numbers to follow this summer after we have proven that the engine will handle all the low end boost, into track testing days. We want to run the car at One Lap of America next year.


Spark was much reduced in this run around 4 deg from where we would be ending up with on 91 octane fuel, this was 22 deg's, and I have even better runs at 27 deg timing, so we have at least 5 degrees of timing left before any sweet spots arrive at this boost pressure. It's a low compression engine, so it's interesting that peak power is very close to 27 deg's timing on 91 octane at 12 psi boost. Thats nearly the average NA engines timing level but this is a turbo engine.


Updates to follow.




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Cool project, and I appreciate the technical detail... But seriously no pics? I'm really hoping it's an S1.

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Here are some more pics, and a partial throttle dyno pull:



Wiring Diagram:






















And last but not least, the partial throttle pull to demonstrate response. We're using 30-50% throttle here.



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are they using a centrifical supercharger or a roots style supercharger?

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