snip.....


   When you enter an actual displacement of 2.6 L equivalent
   displacement becomes wrong.
   Your formula for equivalent displacement is obviously wrong.

   The volumetric shown efficiency is also too low. It should be at
   least 100% for a side
   port and 120% for a P-port.

   Here is what you get with a VE of 115% on gasoline which correlates
   well with what people are getting out of turbocharged 13Bs.

   Also a BSFC of .42 is pretty good at sea level for the turbo compound
   with a TIT of 1750 F.

   Congratulations. Other than the minor problem with the equivalent
   displacement :)

   -----------------------------------------------------

   Op's I just realized that is at zero boost.
   There is a serious mistake in there somewhere. That is probably what is
   fooling you on the displacement.

   Paul Lamar ...No rotor no motor.

   Paul,

   There is no mistake. Everything calculates perfectly.

   What exactly is confusing you? The fact that there is turbine work
   and hp even without boost.

   Of course there is. Even when the compressor is not called upon to
   make boost, there is still flow through the turbine, unless you open
   a wastegate.

   The spreadsheet treats the turbine and compressor as separate
   entities. The compressor is only called upon to make boost when you
   increase manifold pressure above ambient.

   The turbine always has flow through it because the exhaust keeps
   flowing -- even without boost, no?

   There is nothing wrong with displacement. Equivalent displacement is
   double actual displacement.

   You entered 2600 cc into actual displacement, for an equivalent
   displacement of 5200 cc. This would be a 4-rotor engine. Engine
   power, mass flow, etc. are shown accordingly.

   As for VE, I've suggested more conservative numbers. I've seen .94
   quoted in the literature for a side port, and 1.15 seems to be a
   conservative suggestion for p-port.

   Anyway, I've increased the range that can be entered, from .8 to
   1.2, so you can do as you please.

   I've also changed the inlet depression feature to take into account
   ram air, if it is present. So now the user can enter values of -2 to
   +2. I've also increased the mixture range for ethanol to 9 at full
   rich. This is realistic for ethanol.

   Please go ahead and verify with your own flow numbers nad charts.
   Enter the displacement, VE, etc. and check against your charts.

   I've entered the values from your chart in the attached
   spreadsheet, version 3.9. Flow comes out to 220 cfm, which is
   exactly what your chart shows.

   Regards,

   Gordon.


   This spread sheet should work with any displacement engine you put
   in it.
   Piston or rotary. It does not. It doubles the displacement. That is
   wrong.
   This spread sheet is useless until that is fixed. It should not be
   specific to
   a Mazda rotary. The only difference between a rotary and any other
   engine is
   VE and RPM. I put in a 2.6L piston engine normally aspirated at 6000 RPM
   with a VE of 80% and it gave me 285 HP. NO WAY!!!!!!!!!!!!!!!!!!!!

   BTW why limit the engines to 2.6L???

   Paul Lamar


   Okay, Paul.

   I agree the spreadsheet should be usable with piston engines too --
   even though we are primarily concerned with the rotary.

   Anyway here is v. 3.9.2, which lets you work with piston and rotary
   engines on the same footing.

   You can see I've added a field for choosing the type of engine. The
   input for engine displacement is still based on the "official"
   numbers, so that means 1300cc for a 13B. This is how the engine is
   officially known and this is the official displacement.

   The equivalent displacement is shown and all calculations are based
   on that figure. Notice that when you choose piston engine, the
   equivalent displacement is the same as actual displacement.

   You can see in the example I've entered that this describes an
   IO-550 at 2700 rpm. It shows max power of 287 hp, below the 310 hp
   at which Continental rates this engine (in fact that is a minimum
   individual engines can put out as much as 325 hp).

   So this shows my calculations are conservative. I would rather be on
   the conservative side than too optimistic.

   A couple of other changes:

   I switched the SI (System International, or metric) units to
   "consistent" units, for example mass flow in kilograms rather than
   grams, etc. This is more in keeping with standard practice. (the
   actual quantities are still the same of course, just denominated
   differently.)

   I also made a change to the way exhaust pressure is computed. I now
   use a ratio of specific heats that is more accurate for the
   temperatures involved. (I had actually done this in an earlier
   version, but was running out of space, so I decided to drop a
   separate calculation of specific heats).

   You can see in the top right side there are three different
   calculations for specific heats. This is very realistic because at
   any given point in the engine process, temperatures vary widely, and
   as a result so do specific heats.

   The upshot of this is significant for exhaust flow and turbine
   power. Using the actual specific heats has bumped up the amount of
   power we see coming out of the exhaust. This is very realistic now,
   I believe.

   Anyway, I appreciate your feedback and I hope anyone else that tries
   the spreadsheet gives me their thoughts.


   Regards,

   Gordon.

   OK here is what I am going to do. I will build a 2000 cubic inch piston
   engine and call it "1000 CI". I will then go to the Reno race organizers
   and show them the engine. Their rules are 1000 cubic inches max
   displacement.
   I will then insist it is only 1000 cubic inches and demand they let
   me race it. What do you think they would say?

   There is no need for a type of engine. All engines are the same.

   I got to hand it to you Gordon. You are ingenious and relentless
   when it comes to
   avoiding the reality of the situation. I will not publish a spread
   sheet that
   requires the "type of engine." We only need one spread sheet that
   does both
   engines with out specifying which "type" it is.

   Mazda needed you around when they were arguing with
   the tax collectors :)

   I am beginning to think you are jacking me around. I don't think you
   honestly
   believe a 13B is really 1300 cc.

   Show me another 1300 cc (79.33 ci) engine that will make 200 HP at
   6500 RPM.


   Paul Lamar ...No rotor no motor.

   ------------------------------------------------------

   Okay Paul.

   I give up.

   Here's the spreadsheet the way you want it, showing only the
   equivalent displacement.

   It doesn't change the results one iota, of course. It just means
   that now you are
   forcing everyone to enter this ridiculous 2600cc displacement for a
   13B engine.

   I hope we can move on now and discuss the actual merits of this
   spreadsheet.


   Regards,

   Gordon.

   I am going to ignore the "ridiculous" remark.

   OK now we are getting down to it. Thermal eff. is lower for the rotary
   than it is for a piston engine due to combustion chamber shape.
   About the best
   BSFC you will see for a leaned 13B NA is .47. You show .42. Mazda
   claims the RX8
   engine is about .43. I don't think that is leaned. I think it is
   stoech(s?) (14.7).
   At least the RX8 never runs lean in the car. Continental claims the
   Voyager series
   is .38 but I am not sure if that is at sea level or at altitude,
   leaned or what.
   I'll have to look that tech paper up when I get home. Most gasoline
   A/C engines
   are between .42 and .45.

   Therefore you will need some input for thermal eff.

   I assume a Bell PSRU is really a 3:1 Belt PSRU.

   There is also a mistake in cell 12,D It thinks it is looking for a type.

   Other than that this is looking pretty good. This is over estimating
   the HP we got
   for Mark Suspinski's P-port engine on the dyno by about 18 HP.

   Paul Lamar ...No rotor no motor.

   Paul,

   About the thermal efficiency. I know it is lower for the rotary than
   for piston engines and the formula in the spreadsheet reflects that.

   The thermal efficiency is calculated based on what you enter for
   compression ratio, air fuel ratio, and type of fuel.

   For compression ratio, I used the best data I could find for piston
   engines and then decreased that range by a small percentage in order
   to better reflect the rotary characteristics.

   For mixture, I assumed that the highest efficiency is at leanest
   possible settings, just before knock. This is correct, no?

   Both compression and mixture use simple linear equations to
   calculate thermal efficiency. You can see the formulas used.

   Anyway, when you enter compression ratio of 9 and mixture of 17, you
   get bsfc of .46. I think this is pretty close to actual.

   I could restrict the input for mixture to a maximum of 17, but I
   would guess that it is indeed possible to run at 18 in the rotary.

   Ethanol has a higher thermal efficiency by about 10 percent because
   it burns cooler and more slowly. That is reflected in the
   spreadsheet too -- but since you don't care for ethanol I would
   guess you aren't going to worry about it.

   As for the RX8 having a bsfc of 0.43, at stoich, I don't see how
   that is possible. The spreadsheet shows bsfc of 0.52 at 14.6 mixture.

   About the horsepower comparison to the dyno engine you mentioned.
   What did you enter into the spreadsheet for compression ratio? What
   about atmospheric condidtions. A few degrees warmer than 59 F, will
   lower the hp. Also there is the inlet depression. Was there an air
   filter? If so then there is some pressure drop.

   All of these things will lower hp. So let's first try to input data
   as close as possible to the real-world example and see where that
   gets us.

   Now about piston engines. Yes, this spreadsheet is now a
   one-size-fits all calculator -- just like you wanted. The only way
   we could accurately reflect the higher thermal efficiency of piston
   engines is to have a choice of engine type. Right now the
   spreadsheet understates power for the piston engine.

   Regards,

   Gordon.



How does it know the thermal eff. is lower for a rotary? It is now the same
spread sheet for piston or rotary. It has to due with the combustion heat lost to
the coolant. Perhaps you need to add the heat balance diagram to the spraed sheet.