Hi Bryan,

 

Welcome.  Here is my experience using a TWM throttle body (a different model than you are looking at).  Back in 1992 there was no one around that I was aware that could provide any answers to what made a good induction configuration for a flying rotary.  So I turned to the only “rotary aware” crowd around and that was those racing with rotary engines.

 

So after discussing my needs, I purchase a TWM throttle body with 4 injector positions.  It was a two throat (Webber style) design with each throat 2” in diameter.  Two injectors per port (I used MSD 32 lb/hr injectors that fit the injector holes) for a total of 4 injectors on the TB.  The TWM throttle body was then bolted to a cast aluminum  “Webber” style rotary intake manifold which then took the two TB channels and divided them into 4 (two primary and two secondary) distribution runners.

 

I estimate that the best HP I ever made with that set up was around 130-140HP.  My static rpm was 4800 swinging a 68x72 two bladed wooden prop using the 2.17:1 gear ratio.

 

I later replaced that arrangement with 4 tubes of smaller diameter (1 ¼” for primary and 1 ½” for secondary), made the runners longer in length and install the stock Mazda 3 port TB which had considerably smaller openings than the TWM arrangement.

 

I immediately picked up over 300 fpm increase in my ROC and top speed moved from 186 MPH TAS to 195 MPH TAS.

 

As I learned over the years, it became apparent that what works great for the racers turning 9000 + rpm may well suck (but may not suck very well – pun intended)  at 5000-6000 and was therefore of questionable use for aircraft.  As best I could figure out the problem, it appears that with the large runner openings and runners that the mixture velocity in the runners was very much lower than optimum.  That meant the air mass had little momentum and did a poor job of filling the combustion chambers during the short time they were open.  By going to smaller runners, the mixture velocity increased considerably and resulted in more mixture in the combustion chamber and more power.   Now if I could of somehow (using a shifting gear box?) have gotten my rpm range up into the 8000 + range, then that intake system might have been the cat’s meow – but, of course, I could never get above 4800 rpm static (and about 5400 once airborne)

 

Now the TWM Throttle body in the photo based on your description may not have the same problems as it does have a considerably smaller throat than the one I used.  I personally do not believe the use of the four throats would give you what you are looking for – however, the use of two of the throats (one module) might work.  You could always place your second injectors else where on the secondary part of the intake. 

 

Just my opinion, of course, if the price is really good, you have little to lose if it doesn’t work out.

 

I now use a $25 65 mm dia Mustang throttle body which is much lighter (and much, much cheaper) than the TWM model I purchased back over 15 years ago.

 

Good luck on your project

 

Ed

 

Hello all, I have a chance to purchase a TWM throttle body(see attch pic) at a very low price.  I have a couple questions for the group.   The inlets are 42mm (appx 1.65 in.).  Is this too big to the point that they would be incompatible with the injectors?  I plan on using 1-1/8 and1-1/4 in runners.   Also, the bosses are sized for Bosch, Rochestor, or Lucas injectors.  Does this necessarily eliminate my using the stock Renesis injectors?   This setup also would allow the use of a lightweight airbox  thus simplifying the intake system from a manufacturing standpoint.   Thanks in advance, Bryan RV7, Renesis,RD-1C,EC3,EM3 (in the pipeline I hear)