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Intake runner length and balancing intake charge

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Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Tue Feb 24, 2009 11:04 am Post subject: Intake runner length and balancing intake charge

Anyone here ever experiment with trying to balance power output  between cylinders by adjusting the intake runners on an A4K Lycoiming? Any  thoughts? 

I'm wondering if the aft tubes were effectively lengthened would  that make a difference? Lengthened so that the distance from the carb to the  cylinder head would be the same for all 4 cylinders.  

Or would a change in the shape of the pathways in the sump  be more effective? Or both required to get a good balance of power? 

Does the tuned induction on the Continentals work to balance  power? If so why? 

Thanks, 

Ned   [quote][b]

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Tue Feb 24, 2009 12:35 pm Post subject: Intake runner length and balancing intake charge

The IO360M1B is the engine to get for perfect intakes.  It just won't fit in a Tiger

 

 

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Gary
AuCountry Aviation
Home of Team Grumman

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Tue Feb 24, 2009 12:38 pm Post subject: Intake runner length and balancing intake charge

So do you think lengthening the aft intakes  would help balance?

 [quote]   ---

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Tue Feb 24, 2009 12:47 pm Post subject: Intake runner length and balancing intake charge

From SSP204 

IO-360-M1A 180/ 2700/  100/100LL  8.50:1 Same  as –B1E except has a front mounted propeller -51 

160 2400 governor pad and a front  mounted fuel injector 

IO-360-M1B 180 2700 100/100LL  8.50:1 Same as –M1A except propeller governor located  in -51 

the rear, relocated flow divider and impulse  Magneto 

So the M1B has a front facing fuel  injector....why couldn't it fit on a Tiger? Put a ram air induction on it and  have the filtered air come in from elsewhere. Have an intake like a Cheetah but  instead of a NACA put a round pipe extending to the prop... 

I'm thining of doing the Sabertooth that  way...

 [quote]   ---

andy747(at)charter.net
Guest

Posted: Tue Feb 24, 2009 5:35 pm Post subject: Intake runner length and balancing intake charge

why couldn't you take a plain old O360 and put  restrictors in the rich cylinder intakes to balance all cylinders at say 2500  rpm.  Maybe a restrictor like the aperture of a camera with an adjustment  screw that could be mounted in the rubber boot that connects the intake  pieces.  The amount of air coming in should be the same so you are just  redistributing it (and fuel) so power should stay the same, but balanced.   No?

  

 seems like it should work....

  

 Andy Thomas

 [quote]   ---

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Tue Feb 24, 2009 9:39 pm Post subject: Intake runner length and balancing intake charge

OK, so, then, let me see, for the next 10 years you're going to be getting an exhaust system certified to work with an engine also not certified for the plane.

 

 

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Gary
AuCountry Aviation
Home of Team Grumman

GrummanDude

Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA

Posted: Tue Feb 24, 2009 10:26 pm Post subject: Intake runner length and balancing intake charge

Wouldn't it be nice if air flow was one-dimensional?  Then, a simple restrictor would have no effect on turbulence in the intake, the fuel wouldn't separate (i.e., fall out of the air flow) due to the pressure change, and the flow velocity profile wouldn't be affected.   

 

  For what it's worth, the length of the intake affects the amount of kinetic energy in the intake charge.  Short runners are good for high rpm horsepower.  Long ones for low rpm torque.  A difference of a few centimeters can be corrected by porting and polishing, taking the entire assembly into consideration.  

  

 

  Here is something to ponder, regarding flow in a port:  consider a solid propellent rocket motor.  The solid propellent is a cylindrical cross section, let's say, with a cross-section thickness of 1 inch, an outside diameter of 3 inches and internal diameter of 1 inch.  One end is closed.  The other end has a converging/diverging nozzle.  Now, uniformly light the propellent surface.  Question(s):  (1) What do you expect the velocity profile to look like going down the port?  (2) What would you expect the profile to look like going through the nozzle?  (picture the booster engines on the space shuttle)  

  

 

  If your answer to (1) was uniform flow going down the port, what would you think if I told you there are, at times, 4 to to 7 highly rotational flows, rotating as a mass clockwise, then count er-clockwise, then clockwise, etc.  The classical one-dimensional profile you learned when creating a whistle by blowing across the top of a pop bottle, doesn't exist in the real world.  

  

 

  If your answer to (2) is the type of flow you hope is happening in the venturi of your carburetor, you'd be wrong again.  There is, in the highly rotational flow trying to exit the nozzle, a core which is not in the center of the flow, but which rotates around the nozzle like the core of a hurricane trying to get out.

  

 

  Within the intake tubes, every bend and every shape change, changes the fuel density distribution.  Equal length tubes cannot prevent that.  Equal length tubes only affect the amount of energy being stored in the intake charge between each intake valve opening cycle.  Clever manipulation of the rocker arm geometry or cam profile can correct that.  

 

 

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_________________
Gary
AuCountry Aviation
Home of Team Grumman

jamey

Joined: 10 Jan 2006
Posts: 124

Posted: Tue Feb 24, 2009 11:26 pm Post subject: Intake runner length and balancing intake charge

The short answer is no and I don’t know much about the Continentals.  The new IO-550Rs or whatever they are putting in the new Cirrus and Cessna aircraft claim 10 more HP and a 2000 hr. TBO up from 1700.  I suspect the TBO increase has more to do with the metallurgy and manufacturing processes available during certification of this slightly more modern line of engines than the tuned induction but that’s pure conjecture on my part.  I’m assuming most of the power balancing still comes by regulating fuel flow to each cylinder using balanced injectors.  Once LOP where many folks run the big Continentals you have a surplus of air so minor differences in the induction shouldn’t matter much.  ROP maybe the tuned engines are a little smoother?  

   

Jamey  

   

       

From: owner-teamgrumman-list-server(at)matronics.com [mailto:owner-teamgrumman-list-server(at)matronics.com] On Behalf Of 923te

 Sent: Tuesday, February 24, 2009 7:20 AM

 To: teamgrumman-list(at)matronics.com

 Subject: Intake runner length and balancing intake charge  

  

  

   

Anyone here ever experiment with trying to balance power output between cylinders by adjusting the intake runners on an A4K Lycoiming? Any thoughts?  

I'm wondering if the aft tubes were effectively lengthened would that make a difference? Lengthened so that the distance from the carb to the cylinder head would be the same for all 4 cylinders.   

Or would a change in the shape of the pathways in the sump be more effective? Or both required to get a good balance of power?  

Does the tuned induction on the Continentals work to balance power? If so why?  

Thanks,  

Ned   	  Quote: 	
		    http://www.matronics.com/Navigator?TeamGrumman-List 	
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 02/24/09 06:43:00  

       [quote][b]

flyv35b(at)minetfiber.com
Guest

Posted: Wed Feb 25, 2009 6:47 am Post subject: Intake runner length and balancing intake charge

I remember talking to Ken at Lycon once and he told me  he had spent some time trying to do this.  Apparently the charge almost  hits a brick wall (so to speak) when it enters the HA-6 carb sump and doesn't  divide equally from one side to the other, let alone the unequal length  induction tubes.  Gary is right, the best Lycoming engine induction system  is the cold air system with forward facing fuel injector that many of the RV  builders are using.  The air is fed from the baffle plate in front of the  #2 cylinder, through a filter and nice fiberglass duct to the  injector.

  

 It never ceases to amaze me how much people like to  talk about modifying a Grumman or it's engine installation to improve it in some  way and gain better performance (I guess it's fun to dream).  But very few  people actually undertake even getting minor changes approved, Gary, Gene, Fred,  Maynard, Ken, etc. excepted.  It's easy to dream and talk but doing it is  something else.  I'd rather work on getting an STC for a  FI engine that would fit in Gary's cowling and utilize a CS prop and  different exhaust system than trying to band-aid the -A4K.  But if you like  to try all sorts of ideas and want the freedom to do so, why not just build an  RV or Lancair and do what your want.  Even those planes are pretty well  engineered and somewhat  2fixed 2 in what you can do from a practical  standpoint.

  

 In response to Jamey's comments, I don't think that it  matters whether you are LOP or ROP as far as needing to have a balanced air flow  to each cylinder.  If you look at the power developed vs. EGT you see that  the power continues to fall even faster on the lean side of peak the leaner yet  get.  So a cylinder running 10* LOP is developing more HP than one running  50* LOP as I understand it.  GAMI's whole intent was to get all cylinders  to peak at the same time by adjusting the fuel flow thereby keeping one or  more cylinders from falling off in power on the lean side while the others  are still remaining relatively constant on the rich side as the mixture is  leaned.  But they did nothing to change or improve the less than optimum  air flow distribution of the Continental log manifold.  With this induction  system you can still have noticeable power differences from one cylinder to  another even if they all peak at exactly the same time.  The IO-550 used by  Cirrus, etc. attempts to further balance the air flow.  I'm sure that the  cross flow cylinder head (intake in one side, exhaust out the other) doesn't  hurt either.  Once the air flows are equal then you can use the same fuel  injector on each cylinder and the power should be very nearly identical,  resulting in a very smooth running engine.

  

 Cliff

 [quote]   ---

jamey

Joined: 10 Jan 2006
Posts: 124

Posted: Wed Feb 25, 2009 7:50 am Post subject: Intake runner length and balancing intake charge

Hey Cliff,  

   

No great disagreement with you and I certainly agree that 10 LOP is more HP than 50 but my point was WRT GAMIs theory that engine roughness when LOP is due to uneven power production across the cylinders.    This is happening because, just like ROP where minor fuel flow deltas between the cylinders don’t affect engine smoothness as long as all cylinders have a surplus of fuel for the combustion event, I would conjecture that LOP minor differences in induction air flow to each cylinder don’t have as major an effect because the combustion event is throttled by the amount of fuel available.  I do see your point about being leaner or richer having a greater effect on HP produced LOP but I think this is the lesser effect to getting the fuel distribution consistent because the differences in induction air flow are comparatively minor.  

   

To clarify:  

I start with the assumption that a smooth running engine is producing a relatively consistent amount of HP across all cylinders.  This seems to be widely held and agreed upon.  

   

If this is the case then, when ROP the, since the combustion event is controlled by available air then I think the conclusion follows that the air induction system is reasonably well balance even on the older engine designs.  

   

LOP ops depend on this even distribution and are simply fine-tuned with balanced injectors to account for minor inconsistencies in the induction system and presumably the fuel delivery system and even the cylinders themselves.  This (fuel distribution) is the harder nut to crack since the quantities of fuel being delivered are rather small compared to the volume of air and thus, for proper combustion, the metering of the fuel to each cylinder is the more sensitive adjustment.  With truly poor air distribution then smooth LOP (or ROP) operations would be difficult.  

   

That was my point.  I’m sure there are IO-550s that run well LOP down to 14 GPH at 75% where as mine starts getting rough at about 15.5 even with well tuned injectors and this may well be reflective of how well balanced the induction system is but in general I think the air induction systems must be reasonably well balanced.  

   

Anyway, that’s my theory so poke away at itJ  

   

Jamey  

   

       

From: owner-teamgrumman-list-server(at)matronics.com [mailto:owner-teamgrumman-list-server(at)matronics.com] On Behalf Of flyv35b

 Sent: Wednesday, February 25, 2009 6:46 AM

 To: teamgrumman-list(at)matronics.com

 Subject: Re: Intake runner length and balancing intake charge  

  

  

     

I remember talking to Ken at Lycon once and he told me he had spent some time trying to do this.  Apparently the charge almost hits a brick wall (so to speak) when it enters the HA-6 carb sump and doesn't divide equally from one side to the other, let alone the unequal length induction tubes.  Gary is right, the best Lycoming engine induction system is the cold air system with forward facing fuel injector that many of the RV builders are using.  The air is fed from the baffle plate in front of the #2 cylinder, through a filter and nice fiberglass duct to the injector.  

    

   

    

It never ceases to amaze me how much people like to talk about modifying a Grumman or it's engine installation to improve it in some way and gain better performance (I guess it's fun to dream).  But very few people actually undertake even getting minor changes approved, Gary, Gene, Fred, Maynard, Ken, etc. excepted.  It's easy to dream and talk but doing it is something else.  I'd rather work on getting an STC for a FI engine that would fit in Gary's cowling and utilize a CS prop and different exhaust system than trying to band-aid the -A4K.  But if you like to try all sorts of ideas and want the freedom to do so, why not just build an RV or Lancair and do what your want.  Even those planes are pretty well engineered and somewhat "fixed" in what you can do from a practical standpoint.  

    

   

    

In response to Jamey's comments, I don't think that it matters whether you are LOP or ROP as far as needing to have a balanced air flow to each cylinder.  If you look at the power developed vs. EGT you see that the power continues to fall even faster on the lean side of peak the leaner yet get.  So a cylinder running 10* LOP is developing more HP than one running 50* LOP as I understand it.  GAMI's whole intent was to get all cylinders to peak at the same time by adjusting the fuel flow thereby keeping one or more cylinders from falling off in power on the lean side while the others are still remaining relatively constant on the rich side as the mixture is leaned.  But they did nothing to change or improve the less than optimum air flow distribution of the Continental log manifold.  With this induction system you can still have noticeable power differences from one cylinder to another even if they all peak at exactly the same time.  The IO-550 used by Cirrus, etc. attempts to further balance the air flow.  I'm sure that the cross flow cylinder head (intake in one side, exhaust out the other) doesn't hurt either.  Once the air flows are equal then you can use the same fuel injector on each cylinder and the power should be very nearly identical, resulting in a very smooth running engine.  

    

   

    

Cliff  

   	  Quote: 	
		      

----- Original Message -----   

    

From: James Courtney (jamey(at)jamescourtney.net)   

    

To: teamgrumman-list(at)matronics.com (teamgrumman-list(at)matronics.com)   

    

Sent: Tuesday, February 24, 2009 11:24 PM  

    

Subject: RE: Intake runner length and balancing intake charge  

    

   

  

The short answer is no and I don’t know much about the Continentals.  The new IO-550Rs or whatever they are putting in the new Cirrus and Cessna aircraft claim 10 more HP and a 2000 hr. TBO up from 1700.  I suspect the TBO increase has more to do with the metallurgy and manufacturing processes available during certification of this slightly more modern line of engines than the tuned induction but that’s pure conjecture on my part.  I’m assuming most of the power balancing still comes by regulating fuel flow to each cylinder using balanced injectors.  Once LOP where many folks run the big Continentals you have a surplus of air so minor differences in the induction shouldn’t matter much.  ROP maybe the tuned engines are a little smoother?  

   

Jamey  

   

       

From: owner-teamgrumman-list-server(at)matronics.com [mailto:owner-teamgrumman-list-server(at)matronics.com] On Behalf Of 923te

 Sent: Tuesday, February 24, 2009 7:20 AM

 To: teamgrumman-list(at)matronics.com

 Subject: Intake runner length and balancing intake charge  

  

  

   

Anyone here ever experiment with trying to balance power output between cylinders by adjusting the intake runners on an A4K Lycoiming? Any thoughts?  

I'm wondering if the aft tubes were effectively lengthened would that make a difference? Lengthened so that the distance from the carb to the cylinder head would be the same for all 4 cylinders.   

Or would a change in the shape of the pathways in the sump be more effective? Or both required to get a good balance of power?  

Does the tuned induction on the Continentals work to balance power? If so why?  

Thanks,  

Ned   	  Quote: 	
		    http://www.matronics.com/Navigator?TeamGrumman-Listhttp://forums.matronics.comhttp://www.matronics.com/contribution 	
  

No virus found in this incoming message.

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       [quote][b]

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Wed Feb 25, 2009 9:06 am Post subject: Intake runner length and balancing intake charge

I did not say I was going to modify my  grumman A4K. I just ask a question about it. I do have an RV with an O320  and I could modify it without much certification issues. My previous RV 6  had a 4.3liter GM marine engine in it. I had a lot of fun experimenting with it  too. I don't understand why that torques some people so much???

  

 Let me ask, if one cylinder has an  intake leak causing EGT to be a bit higher than the other  cylinders but otherwise functions well why couldn't one put a orfice on an  overly rich cylinder intake to make it run leaner at best power?

 ned 

 [quote]   ---

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Wed Feb 25, 2009 9:15 am Post subject: Intake runner length and balancing intake charge

Very interesting Gary. I did not know  how complicated it was. Sounds like very small changes could have very large  effects.

 On the TIger it would be much better to  slip in a B1E and then start the  fuel mix in the intake part of the cylinder

 [quote]   ---

flyv35b(at)minetfiber.com
Guest

Posted: Wed Feb 25, 2009 10:26 am Post subject: Intake runner length and balancing intake charge

I wasn't referring to you, Ned, just making a general  statement.  Nothing wrong with experimenting and it doesn't bother me at  all.  That's what experimentals are all about, but the FAA has seen fit to  make sure it doesn't happen with certified aircraft, unless you follow their  rules (STC process).  Actually you could surrender your airworthiness  certificate and get an experimental one and do most anything you want (for a  short time) to evaluate a theory, etc. and then convert it back to a  standard airworthiness certificate.

  

 You probably could throttle the intake for an overly  rich cylinder to make it develop less power, but it might not be  leaner.  I've never heard of anyone trying to do something like that.   But it seems to me that every time you change RPM or throttle setting something  changes and now some other cylinder might be the richest  one.

  

 Cliff 

 [quote]   ---

Discover

Joined: 26 Feb 2007
Posts: 429

Posted: Wed Feb 25, 2009 4:25 pm Post subject: Intake runner length and balancing intake charge

Okay thanks Cliff. 

  

 I agree it would all change with every RPM  change...

 I'm just thinking about racing where the  throttle is Wide Open all the time anyway....come to think of it that's pretty  much how my piston plane flies all the time anyway;)

 ned

 [quote]   ---

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