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GeoB

Joined: 16 Jun 2009
Posts: 207
Location: Fresno, CA

Posted: Wed Dec 29, 2010 2:23 am Post subject: Sonex or GP VW

 	  Quote: 	
		   Direct drive Kolbs do not do well and have never performed well on any

model Kolb.
	




I hear you, but would like a few more details. I have been following this

thread because I have a Kolb FS-1. I read about the Kolb powered by the

Generac, and the struggles Mr. young had. He said his plane (FSII) weighed

in at 435 dry and empty. I *think* mine will come in between 280-300# with

Generac (if I go that way). I have been considering trying out the Generac

direct-drive on there.



 	  Quote: 	
		   When compared to an engine with a reduction drive, there is a marked

performance increase with reduction drives.
	




I understand that this will cost me performance. I am just wondering how

much. I can/probably will get a PSRU, but want to look at direct-drive

before giving up on it. Would any of you care to throw out some guesses as

to how it would perform? I weigh a lil more than 210# but getting lighter as

we speak.



 	  Quote: 	
		   As a direct drive Kolbster,I could not agree with you more.

 G.Aman


	


Mr. Aman! What kind of setup do you have?



 	  Quote: 	
		   Faith is believing what you know ain't so - Mark Twain


	


Mark Twain had a lot of things right, but a man such as himself isn't

qualified to speak on 'faith'. He doesn't know diddly about it.  But I

respect your right to quote him, and would fight to the death to protect my

right to needle you about it a lil bit. 



"Faith is taking the first step even when you don't see the whole

staircase". 

                                         - Martin Luther King, Jr.



And I would add, "particularly when you know who built it"



GeoB

_________________
GeoB

"Members of Congress should be compelled to wear uniforms like NASCAR drivers, so we could identify their corporate sponsors"

neilsenrm(at)gmail.com
Guest

Posted: Wed Dec 29, 2010 8:09 am Post subject: Sonex or GP VW

George

  

 I don't think the direct drive Generac option is a good choice for at least two reasons. First, it doesn't sound like you will be happy with the performance if it will even fly.

  

  Another reason is the ability of that engine to accept a direct drive prop. My experience with the VW conversion indicates that there was a long and checkered development process in getting a reliable engine. The first concern is a prop hub attachment. Does anyone make a prop hub for direct attachment to the Generac? 

   

 Next is how will the Generac handle the gyroscopic and harmonic loads of a direct drive prop? VWs had to change to forged crankshafts with a hardened key way and a custom deep drilled and taped prop mounting bolt hole to handle the harmonic loads and then they require only wood props. Also this is with a engine that has fairly even firing pulses. The Generac has two cylinders in a V configuration. This is not a good choice for driving a prop. I know Valley had to develop a custom one way slipping redrive to handle the Generac's nasty harmonics. To handle the gyroscopic loads most VW engines now use a custom main bearing machined into the prop end of the engine case. It is four or five times the surface area of the original. Oh yes and one final issue is the thrust loading on the crank. 

   

 Besides that no big deal go for it.

  

 Again as always worth what you paid for it.

  

 Rick Neilsen

 1st Redrive VW powered MKIIIC



 

 

 On Wed, Dec 29, 2010 at 5:15 AM, George Bearden <gab16(at)sbcglobal.net (gab16(at)sbcglobal.net)> wrote:

 [quote]--> Kolb-List message posted by: "George Bearden" <gab16(at)sbcglobal.net (gab16(at)sbcglobal.net)>

 

 	  Quote: 	
		   Direct drive Kolbs do not do well and have never performed well on any

model Kolb.
	




I hear you, but would like a few more details. I have been following this

thread because I have a Kolb FS-1. I read about the Kolb powered by the

 Generac, and the struggles Mr. young had. He said his plane (FSII) weighed

in at 435 dry and empty. I *think* mine will come in between 280-300# with

Generac (if I go that way). I have been considering trying out the Generac

 direct-drive on there.



 	  Quote: 	
		   When compared to an engine with a reduction drive, there is a marked

performance increase with reduction drives.
	




I understand that this will cost me performance. I am just wondering how

 much. I can/probably will get a PSRU, but want to look at direct-drive

before giving up on it. Would any of you care to throw out some guesses as

to how it would perform? I weigh a lil more than 210# but getting lighter as

 we speak.



 	  Quote: 	
		   As a direct drive Kolbster,I could not agree with you more.

 G.Aman


	


Mr. Aman! What kind of setup do you have?



 	  Quote: 	
		   Faith is believing what you know ain't so - Mark Twain


	


 Mark Twain had a lot of things right, but a man such as himself isn't

qualified to speak on 'faith'. He doesn't know diddly about it.  But I

respect your right to quote him, and would fight to the death to protect my

 right to needle you about it a lil bit. 



"Faith is taking the first step even when you don't see the whole

staircase".

                                        - Martin Luther King, Jr.



 And I would add, "particularly when you know who built it"

http://www.matronics.com/contribution

                              -Matt Dralle, Li    - The Kolb-List Email Forum -

 :

 b-List" target="_blank">http://www.matronics.com/Navigator?Kolb-List<    - MATRONICS WEB FORUMS -

 =   --> h

 

[b]

zeprep251(at)aol.com
Guest

Posted: Wed Dec 29, 2010 10:04 am Post subject: Sonex or GP VW

George,

 Had a FS2 with 503 which of course is redrive equipped.I now fly a MK3C jabiru 2200a direct drive w/Sensenich wood prop.It is slower than a redrive mk3 912ul although both are 80 hp.I love this engine but it makes a lot of noise.My most desired setup would be Jabiru w/PSRU which Jabiru could do because the case is CNC milled from billet stock,they could put attach surfaces on the case easily IMHO. 

 G.Aman MK-3-C Jabiru 2200A Sensenich 600hrs

 

 

   

 

  

   

 

   

 

  --

ceengland(at)bellsouth.ne
Guest

Posted: Wed Dec 29, 2010 7:35 pm Post subject: Sonex or GP VW

One of the Generac's attractions for me is that it's designed from     the start as an industrial, run all day at rated power,  almost any     kind of load type of engine. While the power pulses are uneven &     may give a reduction drive fits, the engine & in particular the     crank should handle almost anything short of a serious resonance     issue. VW & other auto engines were never designed to take side     loads on the end of the crank, but the Generac crank has a pulley     mounted to it in many applications (exception would be direct drive     generators).

     

     I could be wrong, but I would think that a wood prop on a direct     drive Generac would present less load than the crank sees while     driving 4 feet of steel blades through ant hills, small logs, etc     with the load transferred to the crank through a cantilevered     pulley.

     

     FWIW,

     

     Charlie

     

     On 12/29/2010 10:06 AM, Rick Neilsen wrote:     [quote]       George

        

       I don't think the direct drive Generac option is a good         choice for at least two reasons. First, it doesn't sound like         you will be happy with the performance if it will even fly.

        

        Another reason is the ability of that engine to accept a         direct drive prop. My experience with the VW conversion         indicates that there was a long and checkered development         process in getting a reliable engine. The first concern is a         prop hub attachment. Does anyone make a prop hub for direct         attachment to the Generac? 

        

       Next is how will the Generac handle the gyroscopic and         harmonic loads of a direct drive prop? VWs had to change to         forged crankshafts with a hardened key way and a custom deep         drilled and taped prop mounting bolt hole to handle the harmonic         loads and then they require only wood props. Also this is with a         engine that has fairly even firing pulses. The Generac has two         cylinders in a V configuration. This is not a good choice for         driving a prop. I know Valley had to develop a custom one way         slipping redrive to handle the Generac's nasty harmonics. To         handle the gyroscopic loads most VW engines now use a custom         main bearing machined into the prop end of the engine case. It         is four or five times the surface area of the original. Oh yes         and one final issue is the thrust loading on the crank. 

        

       Besides that no big deal go for it.

        

       Again as always worth what you paid for it.

        

       Rick Neilsen

       1st Redrive VW powered MKIIIC

       

       

          

       On Wed, Dec 29, 2010 at 5:15 AM, George         Bearden <gab16(at)sbcglobal.net (gab16(at)sbcglobal.net)>         wrote:

          	  Quote: 	
		  --> Kolb-List message posted by:           "George Bearden" <gab16(at)sbcglobal.net (gab16(at)sbcglobal.net)>

           

           > Direct drive Kolbs do not do well and have never           performed well on any

           model Kolb.

           

           I hear you, but would like a few more details. I have been           following this

           thread because I have a Kolb FS-1. I read about the Kolb           powered by the

           Generac, and the struggles Mr. young had. He said his plane           (FSII) weighed

           in at 435 dry and empty. I *think* mine will come in between           280-300# with

           Generac (if I go that way). I have been considering trying out           the Generac

           direct-drive on there.

           

           > When compared to an engine with a reduction drive, there           is a marked

           performance increase with reduction drives.

           

           I understand that this will cost me performance. I am just           wondering how

           much. I can/probably will get a PSRU, but want to look at           direct-drive

           before giving up on it. Would any of you care to throw out           some guesses as

           to how it would perform? I weigh a lil more than 210# but           getting lighter as

           we speak.

           

           > As a direct drive Kolbster,I could not agree with you           more.

           > G.Aman

           

           Mr. Aman! What kind of setup do you have?

           

           > Faith is believing what you know ain't so - Mark Twain

           

           Mark Twain had a lot of things right, but a man such as           himself isn't

           qualified to speak on 'faith'. He doesn't know diddly about           it.  But I

           respect your right to quote him, and would fight to the death           to protect my

           right to needle you about it a lil bit. 

           

           "Faith is taking the first step even when you don't see the           whole

           staircase".

                                                   - Martin Luther King,           Jr.

           

           And I would add, "particularly when you know who built it"

           

         	
       

     [b]

neilsenrm(at)gmail.com
Guest

Posted: Thu Dec 30, 2010 8:35 am Post subject: Sonex or GP VW

Charlie/All

  

 Ok.... Lets just assume for a moment that the Generac will handle the harmonic, gyroscopic, and thrust loads. The engine is designed as a industrial engine which is a good thing except for weight and power.

  

 Valley Engineering souped up the Generac engine, lightened it a bit, added their reduction drive and put it on Jimmy Young's Kolb FS. Jimmy even had to opportunity to fly the plane with the engine installed and choose the best prop by flying a selection of props. With all that it was found to be inadequate for Jimmy. Imagine now that a stock Generac with a dirict drive prop is installed on what George feels is a much lighter FS. Lets also assume that George will get the prop selection perfect and will get conservatively as much as 80% of the thrust of a reduction drive Generec. Jimmy or anyone how well would the plane fly? 

   

 I'm not a engineer and I could be way off base. I was only able to get maybe 60-70% of the reduction drive thrust from my direct drive VW engine.

  

  I can't find the rated RPM for the 32-33 HP Generac. Lower RPMs closer to 2000-2200 RPM would make for a better direct drive engine. RPMs in the 3200-3600 range like a VW make much better reduction drive engines. 

   

 Again worth what you paid for it.

  

 Rick Neilsen

 Redrive VW Powered MKIIIC

 On Wed, Dec 29, 2010 at 10:33 PM, Charlie England <ceengland(at)bellsouth.net (ceengland(at)bellsouth.net)> wrote:

 [quote] One of the Generac's attractions for me is that it's designed from the start as an industrial, run all day at rated power,  almost any kind of load type of engine. While the power pulses are uneven & may give a reduction drive fits, the engine & in particular the crank should handle almost anything short of a serious resonance issue. VW & other auto engines were never designed to take side loads on the end of the crank, but the Generac crank has a pulley mounted to it in many applications (exception would be direct drive generators).

 

I could be wrong, but I would think that a wood prop on a direct drive Generac would present less load than the crank sees while driving 4 feet of steel blades through ant hills, small logs, etc with the load transferred to the crank through a cantilevered pulley.

 

FWIW,



Charlie



On 12/29/2010 10:06 AM, Rick Neilsen wrote:   	  Quote: 	
		   George

  

 I don't think the direct drive Generac option is a good choice for at least two reasons. First, it doesn't sound like you will be happy with the performance if it will even fly.

  

	


[b]

jbhart(at)onlyinternet.ne
Guest

Posted: Thu Dec 30, 2010 11:35 am Post subject: Sonex or GP VW

Date: Thu, 30 Dec 2010 11:32:51 -0500

From: Rick Neilsen <neilsenrm(at)gmail.com>

Charlie/All

 	  Quote: 	

.............  

Lets also assume that George will get the prop selection perfect and will 

get conservatively as much as 80% of the thrust of a reduction drive 

Generec. Jimmy or anyone how well would the plane fly? 

..............  

 	  Quote: 	

Rick/All

Propeller selection can be a pain too.  On the FireFly with the MZ34 

mounted, I have run two different IVO propellers.  Both have been cut to 

about the same radius.  

 Med pitch 50" prop (at) 14.0 deg - 5,500 rpm -> 23.0 hp (at) 55 mphi

 Low pitch 54" prop (at) 8.25 deg - 5,800 rpm -> 24.8 hp (at) 40 mphi

 Low pitch 52" prop (at) 8.25 deg - 6,000 rpm -> 26.0 hp (at) 40 mphi

This indicates to me that the low pitch IVO is not a very efficient 

propeller for the MZ34/FireFly combination. It is beating the air like 

crazy, but it is not passing enough air through the propeller arc to produce 

thrust at speed.  I have cut the medium pitch IVO down to the limit, and 

with it set to minimum pitch, I can not get the engine up to speed.  Called 

Compact Engines and they do not offer a larger ratio than 2.34 to 1.  Called 

a propeller fellow and he said he could make a propeller that would do the 

job for $700+.  Thought about it some more and decided to re-work the 

propeller hub and sheave combination to get a 2.60 to one reduction.  I 

figure this ratio may do the trick.  If not, I will go back to the propeller 

carvers.

As it flew very well with the medium IVO, I could have left it the way it 

was, but there is something about leaving the last four horses in the barn.  

Should receive the new sheave next week.

Jack B. Hart FF004

Winchester, IN

Jimmy Young

Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX

Posted: Thu Dec 30, 2010 11:59 am Post subject: Re: Sonex or GP VW

 	  Quote: 	
		  Valley Engineering souped up the Generac engine,ï¿½lightened it a bit, added their reduction driveï¿½and put it on Jimmy Young's Kolb FS. Jimmyï¿½even had to opportunity to fly the plane with the engine installed and choose the best prop by flying a selection of props. With all that it was found to be inadequate for Jimmy. Imagine now that a stock Generac with a dirict drive prop is installed on what George feels is a much lighter FS. Lets also assume that George will get the prop selection perfect and will get conservatively as much as 80% of the thrust of a reduction drive Generec. Jimmy or anyone how well would the plane fly?ï¿½ 	




George/Rick/All;



Here's the way I see it. The Generac (Valley Engineering's version) needs to turn 3600 rpm to develop what was supposedly 38-40 hp. It didn't have enough power to safely fly my FS after 112 hrs of test flying with 4 different props. With the adjustable 72" 3 blade IVO, I pitched it so I was turning over 3800 rpm S&L flight and it was still a dog. It was ok on cool, still, stable early morning air, but heck I fly all the time in all kinds of air and it could not safely cut it at mid-day taking off with a crosswind and 95 degree humid air. It may fly someone else's plane that is much lighter or in a tractor config, but not my 435 lb dry & empty FS, and (at) 750 lbs full fuel/me/& 20 lbs of baggage. 



I now have the 60 hp (at) 6200 rpm HKS. Based on that, I should get 50% better performance with it over the Generac. It's more like 90% to 100% better. I'm not so sure the Generac ever developed 40 hp for me. 



Valley puts it on their tractor-pull 254 lb backyard flyer and apparently it works well for that plane. Tractor-pull aircraft are more efficient than our pusher-type Kolbs. They know more about the Generac & how to adapt it to aircraft than anyone around.



I've done all the experimenting I care to do with aircraft engines and plan to stick only to a proven design from here on out. More power is more better, time tested proven designs trump what-ifs and how-abouts. Hoping you're going to make it over those trees on take off is not my idea of fun. I scraped the left side gear off my FS 2 years ago because I could not get enough climb taking off in a 90 deg. crosswind blowing over the hangars on a hot day. I aborted the take-off and made a perfect landing. As others have said before on this List, the only problem was I was 15 ft over the runway when I made it. Pilot error was the cause, not the engine, but it was a contributing factor.



Do what you wish, but to go Generac-powered direct drive & a 56" prop in a FS could only be a worse scenario than what I tried, & I would highly discourage anyone from attempting it.

_________________
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Thu Dec 30, 2010 2:21 pm Post subject: Sonex or GP VW

Jack, you give rpm at different speeds (level flight I presume).  Did you measure the full throttle rate of climb at Vy for each prop?  For ma y of us, that would be more meaningful than cruise performance.  Rate of climb also directly proportional to power changes.



 -Dana



 At 02:27 PM 12/30/2010, Jack B. Hart wrote:



  	  Quote: 	
		  Propeller selection can be a pain too.  On the FireFly with the MZ34 

 mounted, I have run two different IVO propellers.  Both have been cut to 

 about the same radius.  



  Med pitch 50" prop (at) 14.0 deg - 5,500 rpm -> 23.0 hp (at) 55 mphi

  Low pitch 54" prop (at) 8.25 deg - 5,800 rpm -> 24.8 hp (at) 40 mphi

  Low pitch 52" prop (at) 8.25 deg - 6,000 rpm -> 26.0 hp (at) 40 mphi



 This indicates to me that the low pitch IVO is not a very efficient  

 propeller... 	


 --

 HAL 9000: Dave. Put down those Windows disks, Dave. DAVE!    

    [quote][b]

ceengland(at)bellsouth.ne
Guest

Posted: Thu Dec 30, 2010 3:10 pm Post subject: Sonex or GP VW

Hi Rick,

     

     Most industrial engines have a design rpm of 3600 (works for 60hz     generator). A friend has built up a direct drive 992cc Generac &     IIRC, the all up weight is a little under 80 lbs. That would mean     about the same pwr/wt ratio as a traditional 4 stroke a/c engine.

     

     I wholeheartedly agree that 32-36hp is woefully inadequate for a     700+ lb, very high drag airframe, reduction drive or not. A long,     paved strip might make it doable, but not much fun. I'd also agree     that prop rpm lower than 3200-3600 would be much better for a high     drag, low speed airframe, but I don't see any need to go as low as     2200rpm unless there's room to swing a 6.5-7 foot diameter prop,     like the Valley guys are doing on their psru engines. Regular a/c     engines swing 72"-74" diameter props at 2700 rpm with excellent     efficiency. For efficiency, tip speed is tip speed (determined by     diameter & rpm+minor addition for airspeed), & the variable     for higher/lower hp is blade area. 

     

     A lighter, lower drag airframe is a different story. The Europeans     are flying several different designs with decent performance on 20+     hp industrial engines that aren't any lighter than the 36hp Generac.     

     

     I think that you're absolutely correct in the context of     underpowering particular airframes, but don't see a valid reason for     a general dismissal of the industrial engines.

     

     Congrats on your successful VW install.  Having had my share of     grief with a direct drive VW, I'm glad to see VW's running     successfully with reduction drives.

     

     Charlie 

     

     

     

     On 12/30/2010 10:32 AM, Rick Neilsen wrote:     [quote]       Charlie/All

        

       Ok.... Lets just assume for a moment that the Generac will         handle the harmonic, gyroscopic, and thrust loads. The engine is         designed as a industrial engine which is a good thing except for         weight and power.

        

       Valley Engineering souped up the Generac engine, lightened it         a bit, added their reduction drive and put it on Jimmy Young's         Kolb FS. Jimmy even had to opportunity to fly the plane with the         engine installed and choose the best prop by flying a selection         of props. With all that it was found to be inadequate for Jimmy.         Imagine now that a stock Generac with a dirict drive prop is         installed on what George feels is a much lighter FS. Lets also         assume that George will get the prop selection perfect and will         get conservatively as much as 80% of the thrust of a reduction         drive Generec. Jimmy or anyone how well would the plane fly? 

        

       I'm not a engineer and I could be way off base. I was only         able to get maybe 60-70% of the reduction drive thrust from my         direct drive VW engine.

        

        I can't find the rated RPM for the 32-33 HP Generac. Lower         RPMs closer to 2000-2200 RPM would make for a better direct         drive engine. RPMs in the 3200-3600 range like a VW make much         better reduction drive engines. 

        

       Again worth what you paid for it.

        

       Rick Neilsen

       Redrive VW Powered MKIIIC

         

       

       On Wed, Dec 29, 2010 at 10:33 PM, Charlie         England <ceengland(at)bellsouth.net (ceengland(at)bellsouth.net)>         wrote:

          	  Quote: 	
		             One of the Generac's             attractions for me is that it's designed from the start as             an industrial, run all day at rated power,  almost any kind             of load type of engine. While the power pulses are uneven             & may give a reduction drive fits, the engine & in             particular the crank should handle almost anything short of             a serious resonance issue. VW & other auto engines were             never designed to take side loads on the end of the crank,             but the Generac crank has a pulley mounted to it in many             applications (exception would be direct drive generators).

             

             I could be wrong, but I would think that a wood prop on a             direct drive Generac would present less load than the crank             sees while driving 4 feet of steel blades through ant hills,             small logs, etc with the load transferred to the crank             through a cantilevered pulley.

             

             FWIW,

             

             Charlie

             

             On 12/29/2010 10:06 AM, Rick Neilsen wrote:              	  Quote: 	
		                 George

                

               I don't think the direct drive Generac option is a                 good choice for at least two reasons. First, it doesn't                 sound like you will be happy with the performance if it                 will even fly.

                

             	
           

         	
       

       

     [b]

jbhart(at)onlyinternet.ne
Guest

Posted: Thu Dec 30, 2010 4:16 pm Post subject: Sonex or GP VW

Date: Thu, 30 Dec 2010 17:14:20 -0500

From: Dana Hague <d-m-hague(at)comcast.net>

 	  Quote: 	

Jack, you give rpm at different speeds (level flight I presume).  Did you 

measure the full throttle rate of climb at Vy for each prop?  For many of 

us, that would be more meaningful than cruise performance.  Rate of climb 

also directly proportional to power changes.

 	  Quote: 	

Dana,

An amended data table follows:

                                                          Climb    Rate of

                                                          Speed    Climb

Med pitch 50" (at) 14.0 deg - 5,500 rpm -> 23.0 hp (at) 55 mphi 45 mphi  300 fpm

Low pitch 54" (at) 8.25 deg - 5,800 rpm -> 24.8 hp (at) 40 mphi 40 mphi  ???

Low pitch 52" (at) 8.25 deg - 6,000 rpm -> 26.0 hp (at) 40 mphi 40 mphi  ???

The low pitch propeller flights were very short and the engine speed did not 

vary until the FireFly was once again over the runway.

Jack B. Hart FF004

Winchester, IN

GeoB

Joined: 16 Jun 2009
Posts: 207
Location: Fresno, CA

Posted: Sun Jan 02, 2011 9:40 pm Post subject: Sonex or GP VW

 	  Quote: 	
		   From: "Jimmy Young" <jdy100(at)comcast.net>

 Here's the way I see it. The Generac (Valley Engineering's version) needs

 to turn 3600 rpm to develop what was supposedly 38-40 hp.


	


Thanks for your comments Jimmy. I am thinking you may be right on, but I

lack the aircraft experience to even guess.



I have not heard that VE hopped up the Generac engine. I would really like

to know what mods they performed for you to get the performance that you did

get (if any mods at all).



I originally bought the Generac before I had my Kolb. It isn't the end of

the world if I don't use the Generac on there. I have a new 503 DCDI in the

garage. My experience is in engine building and modifications. I have

enjoyed pleasing results, some surprisingly good, but am NOT saying I am

anybody's idea of a professional. My interest is/was in seeing how close to

a good aircraft engine I could convert the Generac into. With the torque

peak at +/- 2200 rpm I feel that there remains considerable power and torque

potential remaining untouched here. I have no idea what I will decide to do-

but so far I have been investigating high-torque cams, with my desktop Dyno.

More to go on that. I kinda anticipate doing some manifold and head work.

Not sure the carb yet. I may lower compression some, may mod/replace the

ignition. I think 36 degrees is too much advance for my taste. The gasoline

flywheel has a more reasonable advance. Mine is a propane model.



Jimmy, suppose I had your exact engine, PSRU and a good prop match on my

lighter FS1. Do you have any wild guess what the performance might be then?

You think VE folks could give experienced feedback on that?



GeoB

_________________
GeoB

"Members of Congress should be compelled to wear uniforms like NASCAR drivers, so we could identify their corporate sponsors"

zharvey(at)bentoncountyca
Guest

Posted: Sun Jan 02, 2011 10:44 pm Post subject: Sonex or GP VW

Hi George.

Love the sound of the VE Generac!  I have quite a few trouble hours behind 

Rotax 2 strokes (well over 400 hours) but only a few in a Kolb (Firestar 

XKP)and I'm wondering if there seems to be issues with the two?  Are there 

still a lot of folks using the 503 on the Kolb or for some reason is 

everyone searching for something else for a given reason?  I've been away 

from the 2 stroke scene for a goodly number of years,  so things may have 

changed.  Last 2 stroke I had was a 618.  A wonderful engine.  Any info you 

can share with me on the 503 and Kolb Firestar would be much appreciated.

Gene

N71RB  Kolb XKP with 503

zharvey(at)bentoncountyca
Guest

Posted: Sun Jan 02, 2011 11:00 pm Post subject: Sonex or GP VW

Should have read "trouble FREE hours"

Gene



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

From: "Gene & Tammy" <zharvey(at)bentoncountycable.net>

Sent: Monday, January 03, 2011 12:42 AM

To: <kolb-list(at)matronics.com>

Subject: Re: Re: Sonex or GP VW



 	  Quote: 	
		   

 <zharvey(at)bentoncountycable.net>



 Hi George.

 Love the sound of the VE Generac!  I have quite a few trouble hours behind 

 Rotax 2 strokes (well over 400 hours) but only a few in a Kolb (Firestar 

 XKP)and I'm wondering if there seems to be issues with the two?  Are there 

 still a lot of folks using the 503 on the Kolb or for some reason is 

 everyone searching for something else for a given reason?  I've been away 

 from the 2 stroke scene for a goodly number of years,  so things may have 

 changed.  Last 2 stroke I had was a 618.  A wonderful engine.  Any info 

 you can share with me on the 503 and Kolb Firestar would be much 

 appreciated.

 Gene

 N71RB  Kolb XKP with 503

Jimmy Young

Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX

Posted: Mon Jan 03, 2011 10:48 am Post subject: Generac on a FS (was Re: Sonex or GP VW)

 	  Quote: 	
		  I have not heard that VE hopped up the Generac engine. I would really like 

to know what mods they performed for you to get the performance that you did 

get (if any mods at all). 	




GeoB,



The only mods that mine had were an Empi carb, a custom intake manifold, and a custom exhaust. Your best bet would be to call Larry (at) VE & discuss the engine with him regarding what they have done since then. They are very much a customer-service oriented family biz and are great to deal with.



 	  Quote: 	
		  suppose I had your exact engine, PSRU and a good prop match on my 

lighter FS1. Do you have any wild guess what the performance might be then? 

You think VE folks could give experienced feedback on that? 	




I would guess a sustainable climb rate of 300-450 fpm. My cruise was the same as with the 503. What did not work for me was very poor & even negative climb rates in hot summer air while trying to overcome the sinks & downdrafts. On nice cool mornings it flew decent, but in mid-day summer air there just wasn't enough power to safely fly the plane IMO.  



If I had only a choice between a 503 & a Generac on a FS, I'd take the 503 hands down.



Good luck with your project -

_________________
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700

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