Inverted Honda engine

Discussion in 'General Auto Conversion Discussion' started by Brian Clayton, Dec 18, 2013.

  1. Dec 18, 2013 #1

    Brian Clayton

    Brian Clayton

    Brian Clayton

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    Today I picked up a 1.7 honda engine. I have been wanting to see if a late model engine could be inverted for use as a direct drive engine in the 60-80 hp range. The core I found is a D17a1 engine. Its a aluminum block and head non vtec 24valve sohc engine out of a 2005 Civic. About 105 CI, 115hp @ 6100/110tq @ 4500. I will post pictures when I get a chance. For the time being, I have some preliminary stripped weights (before lightening) and some observations I have made along with some information I have found. The block. 42lbs stripped, including main caps/bolts. The block is a interesting piece. All of the oil galleys and water passages (other than around the cylinders) are external castings, making it very easy to access and modify them. There are 4 large oil drain backs from the head to the pan along the perimeter of the block, aligned between cylinders 1&2 and 3&4. The good part about this is that it will be super easy to drain the oil from the base of the cylinders back into the sump. The mains are oiled by directing oil internally thru the one piece main cap girdle. I am not crazy about this setup, but considering I am only shooting for 60-80 hp at 3000 rpm or less, its probably not a issue. The factory water pump is driven off of the timing belt, with only the drive/impeller being removable. The rest of the pump is machined into the front of the block. The factory oil pump is driven off of the crank, right behind the balancer. Whether it will get used will have to be seen as this progresses along. The head. 36lbs stripped externally, but including cam, and all valvetrain. SOHC, 24 valve. Aluminum adjustable rockers, non roller. There might be enough room for a 2nd plug in the head, casual inspection says maybe. Custom grind camshafts seem to be available for this engine or I can just have the stock one reground if needed. Crankshaft. 24lbs. Forged unit, reliable to 600 hp. Seems to be able to lightened about 7 lbs for a race engine, perhaps more this application. I am not opposed to a billet shaft, if modifying a stock one starts to approach the cost of a new one. Rods and pistons. 4lbs set. While the stock rods are supposed to be good to about 220 hp, a set of new aftermarket rods rated to 800 hp are only about 350.00. I look at it this way, by the time you buy aftermarket bolts, floating bushings, check the rods and have them remachined.....75.00 or so each for new rods is cheap. And from looking, I don't think the pin ends have enough material for bushings anyway. Misc parts. 19lbs. I was lazy.... water pump, oil pump, all the bolts, valve cover, oil pan, thermostat housing, timing belt parts..... it was all still nasty in the plastic tote, so I just weighed it all to get a general idea. I was not looking for a finished weight yet, just wanted a idea of what was here. The block will loose a fair amount, once it gets introduced to the bandsaw and mill. There are quite a few mounting bosses that can be removed and a large portion of the bellhousing flange. The head, not too much to loose, but I am sure a pound or so can be found with some constructive pocket milling. Total of the rough weights so far is 125lbs. More to come once everything meets steam cleaner for the first time in a while. I welcome them, but......Please keep comments related to inverted aircraft/automotive engines......
     
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  2. Dec 19, 2013 #2

    deskpilot

    deskpilot

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    Interesting idea Brian but would it not be cheaper, in the long run, to find a purpose built inverted engine and up-grade it to your requirements?
     
  3. Dec 19, 2013 #3

    Brian Clayton

    Brian Clayton

    Brian Clayton

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    Probably.....but there doesn't seem to be a abundant source of inverted 4 cylinder aircraft engines in this power range. If you do find one, it was last made in the mid 30's with parts being rather scarce. Inverting the engine is the easiest problem to overcome. Lightweight power at a low RPM is the challenge. Besides....this is a interesting project....Sort of like building a airplane instead of just buying a used Cessna or Piper or whatever.
     
  4. Dec 19, 2013 #4

    Vipor_GG

    Vipor_GG

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    It's easy to get an engine to run in a particular orientation, have low RPM power, have a favorable power to weight, or be very reliable. The trick is getting them all at the same time.:ponder:
     
  5. Dec 19, 2013 #5

    Dan Thomas

    Dan Thomas

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    Walter Mikron.

    115.jpg

    75 HP, still being built in Czechoslovakia by Parma Technik.

    Dan
     
  6. Dec 19, 2013 #6

    Brian Clayton

    Brian Clayton

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    After spending some quality time with a hot water pressure washer today, I got all of the bits and pieces cleaned up and got ready for a closer inspection. Due to the lack of crank snout length, looks like the prop will have to be driven from the flywheel end. This actually works out well for a few reasons. It will much easier to machine the original front of the block for a proper thrust bearing. I spent a hour or so today looking at different roller thrust bearings and getting some ideas hammered out for what this will need. Once I get some rough dimensions, I can start making phone calls to bearing suppliers to see what they have available. The only problem is that unless I can figure out how to pass the crank thrust load thru the center of the oil pump, then the stock pump will have to go. Not a big problem, but moving the pump will require some amount of work. But considering that a dry sump has not been ruled out yet, this may not be a issue in the end. If needed, flywheel end prop mounting would make using a vibration damper easy. More of the bellhousing flange area can be removed than I originally thought. Draining the cylinder base area should be simple, due to a few things. First, the factory casting already slopes away from the cylinder toward the outside of the engine. The material thickness between the base of the cylinder to the water jacket around the cylinders is roughly 1.250 inches thick, so there appears to be enough material present to use a ball mill cutter to create a raised lip around the cylinder base. This will help control oil draining from the crankshaft from flowing easily into the cylinders, hopefully eliminating the need for resleeving with a longer sleeve to create a lip. The tip of the skirt on the factory pistons protrude from the bottom of the sleeves about 1/8 inch, and it looks like there will be enough room for extra oil control rings on the new pistons. I am going to a local junk yard in the morning to see about a extra core engine, since I would like to have a extra block and head I can run through the bandsaw and see exactly where the internal materials are and figure the angles for the new oil drain holes at the base of the cylinders. I looked at the flywheel end, and it does look possible to mount a roller/ball bearing for external support of the crank/prop flange, but that will have to wait until I start on designing a prop hub. On the cylinder head end..... This head is semi-hemispherical combustion chamber, with the original plug almost in the center, angled toward the exhaust valves. Originally, the head has steel tubes presses into the head, running up thru rubber gaskets snapped into the valve cover. This creates a oil free area for the plug wires to pass thru. Being so, it looks that it will be easier to add a sump to the factory valve cover for the time being. A carbon or new sheetmetal cover would lose some weight, but at this point a modified factory cover will be fine.
     
    Last edited: Dec 19, 2013
  7. Dec 19, 2013 #7

    Brian Clayton

    Brian Clayton

    Brian Clayton

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    I have seen these. Last I knew they were about 12k. Very nice engine.
     
  8. Dec 19, 2013 #8

    raven-rotor

    raven-rotor

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    Dan

    I'm excited to see someone writing about something a little different.

    The cut away demo engine that they had at the Walter Mikron booth at Oshkosh years ago really detailed the basics of what was needed internally to run an inline engine inverted for oil control. We looked into it extensively for our Geo®/Suzuki® engines as an alternative ultralight legal 4-stroke engine but did not get enough interest to justify all the testing and tool up required for a successful product. Biggest downside for us was the question of the stock crankshaft and successfully tying it to a propeller. Attaching it directly to the crank puts a few ??? on long term reliability, gyroscopic loading, and possible torsional resonance issues. Building a dampened coupled prop support with outboard bearing quickly starts to head in the direction of the weight gain and cost/complexity of a reduction drive without the added power of being able to spin the engine at its rated peak HP.

    Based on the displacement of the 1.7L Honda® compared to our little Suzuki® 1.0L 38HP direct drive engine we tested upright, that would put your engine at about 63-65 HP at 3300-3400 RPM based on displacement. Our weight to HP at 95 lbs. dry weight with radiator (no prop and hand started) was the best we could do and it would have been a little lighter if we could have inverted the engine and used the rocker cover as an oil pan. Our experience with dry sumped engines and remote oil pick-up (the Suzuki® pump was already ported for that) showed that we could pull at least 18" from oil pan pickup to oil pump so I think you will be able to go with the stock pump.

    Looking forward to hearing more about your project as it unfolds. A direct drive inverted has always been on the back burner here- just not enough time to do all the possible R & D projects. Wishing you success in your endeavor.

    Jeron Smith
    Raven ReDrives Inc.
    303-440-6234
     
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  9. Dec 19, 2013 #9

    BBerson

    BBerson

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    I agree with Jeron about horsepower. It should be the same as any aviation VW conversion at that same size and rpm.
    Regarding the thrust bearing: I would use the stock thrust bearing and simply bolt to the stock crank flange. The crank output shaft is larger than most VW conversions that use the pulley end.
    Yes, the Honda thrust bearing* is in the middle of the engine... But I don't think it matters. Of course others may disagree, in that case, another internal thrust bearing washer could be fitted at the flywheel end also, if desired.

    I have a Honda engine dismantled and lightened. I wanted to convert it to air cooled in order to get the weight under a 100pounds for an ultralight. This project is now on hold, mostly because it's just too much modification needed to be practical.

    BB

    * I have a Civic 1.6
     
  10. Dec 19, 2013 #10

    cheapracer

    cheapracer

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    The downside of a busy mind!
     
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  11. Dec 19, 2013 #11

    Jan Carlsson

    Jan Carlsson

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    My guess is that the 1,7 L will produce ~60HP at 3300 RPM, installed.
     
  12. Dec 19, 2013 #12

    cheapracer

    cheapracer

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    Probably very close by the time the plane exhausts and suitable tuning is done ....

    4.jpg
     
  13. Dec 19, 2013 #13

    Brian Clayton

    Brian Clayton

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    I don't now if the 1.6 is different, but on the 1.7 the thrust is a 2 half circles on the #4 main, positioned only on the block side. The main bearing itself is identical to the others in the engine. I am not crazy about a 180 deg thrust, that's why I was looking at adding a more substantial bearing between the oil pump and the block. This evening I am going to tear down the stock oil pump and see if it can be modified to allow the thrust load to pass thru. If the pump will pull from the new sump, it would make things much simpler and go much faster. Even just using it as a pressure stage and adding a scavenge stage(s) (like some radial engines) would be a option. I don't think there are any multi stage stock pumps that could be adapted, but I may be wrong. I like the idea of a aircooled version, but to be easy I think it would need to be a cam in block conversion. If you made a new head, it might be difficult (heavy) to get the cylinders stable enough to support the stress of a OHC. I guess you have seen the billet deck support made for Honda engines? I know they use it on the higher output engines, I hope its not needed on this one. The deck design is one of the few things I don't like about this engine. I considered a output support bearing that would also double as a new thrust, but I have not gotten that far along....
     
  14. Dec 19, 2013 #14

    Brian Clayton

    Brian Clayton

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    Jeron, I like your Geo conversions. I almost bought one second hand for another project, I missed it by a day though. I had considered trying to invert a geo engine, but I was concerned about the small displacement reaching my target HP without resorting to forced induction. I am glad to hear that about the pickup distance on the stock pumps. I look at it this way, its great if the stock pump can be used, but its not a deal breaker if it cant. I do thank you for your words of wisdom and interest. Brian
     
  15. Dec 19, 2013 #15

    Brian Clayton

    Brian Clayton

    Brian Clayton

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    I hope so. If it will do that first time running and not destroy the crank in short order, it will be something to work with. I looked at adding some more stroke, but preliminary measurements/inspection indicate not enough room without really high piston side loading at BTDC.... the deck height is just not tall enough.
     
  16. Dec 19, 2013 #16

    Toobuilder

    Toobuilder

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    Curious your initial desire for dual plugs.... Are you thinking for safety, or a performance requirement?
     
  17. Dec 19, 2013 #17

    Brian Clayton

    Brian Clayton

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    More of a safety issue than performance. I don't think modern ignitions need 2 plugs for performance (fuel cars aside). The 4 valves get in the way though... makes things a little tight. I am not married to the idea of dual plugs, just a thought. If it could be done easily, why not?
     
  18. Dec 19, 2013 #18

    Toobuilder

    Toobuilder

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    Well, keep in mind that even back in the days when the unreliable magneto ignition was "state of the art", dual plugs were there for performance - "safety" was an afterthought. I'd say that as the decades have passed and ignition systems are now essentially maintenance free and bulletproof, the idea of two complete ignitions is overkill. I could buy the idea of dual CDI boxes and coils (since that stuff is available right now off the shelf thanks to racing efforts), but not to take it all the way to the combustion chamber. Just my opinion.
     
  19. Dec 19, 2013 #19

    Brian Clayton

    Brian Clayton

    Brian Clayton

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    I agree completely. Dual plugs was something I was just looking at during the initial inspection. Even if I found a easy way to do it, I would not do it in this stage of the game. It would just add complexity, and may create time eating problems with the valvecover/oil pan sealing. I think Rv6guy claims thousands of trouble free hours with the ignition he sells, and considering it requires no mechanical connection to the engine, it would be super easy to do. The factory uses a coil on plug setup. Might be a issue keeping them in the engine inverted. :roll:
     
  20. Dec 19, 2013 #20

    BBerson

    BBerson

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    No. Is this deck support for racing engines?
    I wouldn't need anything from racing engines, I think, at 2500-3000 rpm.
     

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