Yes.  As you may recall, I also run with the TWM TB, and I also see lower MAP than the local atmospheric pressure.  That is quite likely as it should be, or if not; it doesn’t matter.  The MAP reading depends on where you measure it.   

 

Hi Al,   Yes, I recall that we've had this conversation before :-)

 

I certainly agree that it matters where you measure the MAP, and it would be nice if we were all measuring it in the same place for comparison.  I'm thinking of trying to put a port at the intake flange, but I'm not sure if I have room to drill and tap a hole there yet.  I'm also not sure it will give an accurate reading.  Still, it won't give an apples to apples comparison to anyone else.     

 

On the dyno at WOT at 5300 rpm with a local barometric pressure of 29.5”, the MAP reading was 27.5”.  At 6000 rpm, WOT, MAP had dropped to about 26.5”, and it was putting out close to 85 hp/rotor (SAE corrected, which means actual measured of just over 80) with 9.0 rotors.  At 7000 rpm the MAP reading was 23.5” and the power was still climbing at 95 hp/rotor.   

 

Reading these numbers sounds like the definition of "restriction" to me.  The more air you try to pull through the TB, the lower the pressure drops.  Velocity makes up for some of this, but I'm not sure where the tradeoff is.   If you've got 95 hp/rotor now, imagine what it could be with less restriction.  

 

Didn't Lynn say they have to run chokes, or restrictor plates per the rules of their racing class?  He's producing lots of power, but don't you think he'd love to take those restrictors out :-) 

 

Whatever that MAP reading is, I don’t think that there is a significant power penalty that goes with it. 

 

Sorry, but I can't see how you can say this.  It seems to me that MAP is probably the number one factor in power production.  

 

Hoping this makes you feel better, 

 

I'm afraid not, just the opposite in fact, but thanks for trying :-)

 

Cheers,

Rusty (dealing with the Ebay single rotor guy)