1165 Supercharged Mel Miller engine


                                                                         My latest project.


My goal with this set up is acceleration from 5 to 60 in 3 seconds or less. The new 300 HP Sea Doos can do this  in 4.36 seconds. See the acceleration test on Sea Doo and Yahama  by Jerry and Paul  of Green Hulk Performance  shown below.  Last year I was able to do 5 to 60 in 3.78 seconds at 4 lbs.of boost . So, let's up the boost and see what happens.

How about 8 to 10 lbs??    I recently machined new pulleys to get the 8 to 10 . I contacted Jackson Racing, the US distributor for Rotrex and they calculated the pulley sizes I needed.

   I no longer use my Land and Sea dyno for tuning . I've gained enough experience to tune while riding by using the Motec features of  "on the fly" fuel and timing adjustments as well as data logging.

  Miller says the 1165 engine on his dyno makes 215  to 220 on a single Coffman pipe. So, a good estimate at 4 lbs would be 280 hp., and at 6 to 8 lbs ???

 The Rotrex model is a C38-71 and is capable of 500 hp. This will be my third year of developing and testing this set up. I've had a total of 10 years experience with turbos and superchargers. 


​

                                                                                      performance update


From Jackson Racing's recommendation, I switched to a smaller supercharger pulley to add 10,000 rpms which should have given  me 4 to 6 more pounds of boost. The outcome was that I lost engine power,  rpms and speed. I think that there is 2 reasons for this: First one being that the higher gear ratio of the supercharger robbed some power from the engine. i did notice that there was more air going into the engine, but the boost only increased by one half pound, not enough to overcome the extra load of the supercharger.  Data logging showed more air going in and  the pressure in the pipe increased, as did the fuel consumption, but there was no extra air staying in the cylinder to make power. Sort of like in a 4 stroke that has a cam with too much overlap and  a lot of the boost just blows though the engine.

    Miller and I both agree that we need to restrict the flow through the engine. His porting spects are set up for maximum flow in a normally aspirated engine and is not very suited  for boosting.

  So for next year I'm going  back to the slower supercharger speed , as it ran really well with the old set up,  and I will work on shimming down the RAVE valves to restrict the air through the exhaust. This may cause a loss of rpm from the port height being reduced, but it hopefully shows that we  are going in the proper direction. Miller is designing a  new set of sleeves that will also restrict the air at the exhaust port without loosing port height and rpms.

   The hope is that one or both of these mods will trap more air in the cylinders for more power.

  Stay tuned for updates from water testing next summer.


                                                    2022 update


   The sleeves that Miller set up for boost are here and I'm fitting them to the case. CC's will be 1180 from the larger bore. I expect to be in my test tank in early June and to the lake shortly thereafter. I'll post the performance spects if and when it runs better that before. Actually I'll post whatever happens. I know there are a few of you following this project.


                                                                  2023 update


New 1180 does run stronger. After reviewing the health of the engine , I added more compression and reduced the squish. I went too far and burnt a piston., so,  unfortunately I did not get a data log with performance info. I will be rebuilding the engine this Fall and it will be  for sale along with all the supercharger goods as I want to concentrate on building a clone to the race boat I bought from Miller, the 1194 twin pipe stroker XPL.

​

Click to enlarge and see notes.

Kansas city area                     contact: rwosel@c-rmfg.com