Greetings,

 

I'm probably about to prove that I haven't paid any attention to any of the intake construction threads, but here goes...  I know there's special length that will tune the intake to make more power.  Ed knows what this is, but if he tells us, he has to kill us (a slow painful death, involving 60 slides)  :-) 

 power band, so I started wondering if I could "tune" it with individual pipes on the inlet side of the TB.  

 

Thanks,

Rusty (Scotty, I need more power!) 

 

Hi, Rusty.....I purchased the short intake manifold from Dave Atkins. He claims he has more than adequate power with his, and that idle is also good.  Look at all the race cars and racing motorcycles that have the carbs or throttle bodies right next to the engine.  They seem to generate a lot of power that way. For what it's worth.

 

 Paul Conner

 

 

 

Paul is correct. There are any number of intake configurations that will produce adequate power for the RV-6. I am told that Dave Atkin's intake permits him to generate approx 160HP which is certainly adequate for an RV and could even provide thrilling performance in a low weight RV

 

I'll have to say I've flow an RV with adequate (whatever that means) performance while producing as little as 120HP.  The cruise was around 180 TAS which was adequate because even today I generally elected to cruise at 170 TAS to conserve fuel, but take off and climb with 120 HP in my somewhat heavy bird were agony!

 

 Paul, not disputing what you say at all, but you have to consider the different application.  you are making the same assumption that  I made with my first intake.  Yes, I listened to the Racing guys and I'm certain that their advice was just peachy for racing - if you are turning over 7000-8000 rpm.  Than rpm range means short runners and large diameter inlets are the cats meaow. 

 

But, I can tell you from personal experience that if you think you are going to put a curise prop on your RV-6 with that set up and think you are going to turn 7000-8000 rpm with a 2.17:1 PSRU you are going to be sadly disappointed. Tracy Crook turns as high an RPM with that set up as anyone I know (has hit 214 mph TAS) and maxs out at around 6400 rpm.  His tubes are 1.25 and 1.5" in diameter as best I recall and wrap over the top of his engine so that is air intake sits on the top middle of his cowl.  So the tubes are not short.  

 

 The auto and motor cycle guys have one advantage - they have gear boxes which permit them to wind the engine up into those higher rpm ranges with a lighter load (lower gear) before shifting to the next ratio (where you do indeed generate more power), but we can't wind our engine and then shift gears (at least not yet).

 

Bill Eslick initially use a very short induction system which provided very disappointing performance results.  His report (earlier on the list this week) indicates that once he went with a different (read - longer intake, copied after Tracy's as was mine) his performance improved so that he now keeps up with the 160 HP Lycoming powered RV-6s.

 

You have to select the induction system parameters that is realistic for your application!  What sucks for us - works for the race guys, what works for us -would suck for the race guys.  Its like apples and oranges (so to speak) {:>)

 

Now, I will be the first to say, if you want to experiment or if you find for cost, configuration or convience reasons you want to try some particular intake configuration, please do so.  I've been wrong before and I am certain will be in the future - but, do it with your eyes open and understanding of what performance might reasonably be expected.

 

Best Regards

 

Ed Anderon

 

 

 

Hi, Ed.....thanks for the post and education. I guess I was kinda thinking that if Dave Atkins's RV performs that well with his short intake manifold, my aerodynamically cleaner canard should perform equally to, or hopefully better?  The primary reason I liked his intake was because it is truly "bolt on" and go.  I tried to buy the wrap-over manifold from Powersport, but their reply was...."sorry, we can't help you".  I'm sure that experimenters such as yourself, who know and understand intake systems better than I, can tweak more power out of these engines.  The latest effort I am going to attempt is a wrap-over system similar to Paul Lamar's, but with only two intake runners. The intake manifold I ordered is cast so that the four intakes go into two almost immediately, and from there I will make my aluminum tubing wrap over the top of the engine (as close as possible for cowling clearance) and then terminate with my TWM throttlebody with the built-in injectors. )(Also purchased from Dave Atkins, because it was another "bolt on").   Did I mention that I like bolt-ons?  I truly appreciate the time and effort you invest into improving these rotary installations for aircraft.  Thanks again.  Paul Conner