Author Topic: Treadmill Dyno  (Read 164104 times)

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Frank S

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Re: Treadmill Dyno
« Reply #462 on: January 14, 2014, 01:02:11 AM »

i see one port in the head
i see one diagonal  port in the rotating valve.
does this one angled port do both intake and exhaust?
looking forward to seeing the intake /exhaust manifold perhaps that will enplane

 If you look at the pic where he is holding the valve you will see that it has 2 ports . the way a rotoray valve of this design functions would be for  the intake on one end and the exhaust the other.
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electrondady1

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Re: Treadmill Dyno
« Reply #463 on: January 14, 2014, 08:45:41 AM »
oh. ok. so the gasses enter/exit through the ends of that rotating shaft.

Frank S

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Re: Treadmill Dyno
« Reply #464 on: January 14, 2014, 01:01:55 PM »
oh. ok. so the gasses enter/exit through the ends of that rotating shaft.
  That would be how it is done works fine for a single cyl engine on an engine with more cylinders it would require a separate
 rotary shaft for intake & exhaust or a combination valve shaft per cylinder.
 Or that is how I see it.
   
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taylorp035

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Re: Treadmill Dyno
« Reply #465 on: January 15, 2014, 10:21:42 PM »
That's correct Frank.  For multi-cylinder engines, the rotary valves would have to be perpendicular to the row of pistons/crankshaft.  Or, you can do two long valves, one being the intake and one being the exhaust.  I have seen both and they both have major advantages and disadvantages.  Obviously I haven't tried to take on such a challenge.


I finally got the last of the half links and two master links to finish off the chain drive tonight, along with a new spark plug.  Minus the carb, here is the finished product:




We tried getting it to fire by spraying some gasoline into the intake, but it didn't do anything.  After a bit of inspection, we couldn't seem to get the spark plug to fire, even though it would shock you if you touched it.  Then I broke my pull cord.


Quote
Any thoughts about a lubrication system?
For right now, we just drip a bit of 5W-30 on the valve to get it wet.  If it needs more, then we might bevel the leading edge in the aluminum head a bit to hold more oil.  We could also essentially have an oily brush that gets dragged on top of the valve (slightly dangerous with the possible exhaust flames being present....).  My senior design project just had a graphite block with some tiny cross drilled holes and an oil reservoir.  That actually worked really well.   If all of that fails, then some tiny grooves in the surface of the half pipe or even pressurized oil could be done.  I don't think it will a huge problem given our experience with the first design.  Then again, we used 6061 for this head instead of the QC-10 aluminum, so it's a lot softer.

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Re: Treadmill Dyno
« Reply #466 on: January 17, 2014, 12:42:52 AM »
Quote
...we couldn't seem to get the spark plug to fire, even though it would shock you if you touched it.

Checked the electrical conductivity across interfaces - plug - head - cylinder body?
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Bruce S

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Re: Treadmill Dyno
« Reply #467 on: January 17, 2014, 08:19:45 PM »
AND grounding!Aluminum always was an issue with spark plus even on 351 Cleveland "wedge: engines.
Try holding the spark plug on the iron part of the casting then see if you get a spark.
 
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Frank S

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Re: Treadmill Dyno
« Reply #468 on: January 18, 2014, 02:00:08 AM »
I don't know what you are using for your ign system but if you are using the old contact points & condenser type the spark has always been tenacious at best on Briggs engines. I started using an EI  on all small engines after it came on the market . A far more powerful spark and reliable
 the link is a similar unit to the ones I've used in the past and I am sure there are better on the market
http://www.ebay.com/itm/Briggs-Stratton-394970-OEM-Magnetron-Electronic-Ignition-Conversion-Kit-/181294409276?pt=LH_DefaultDomain_0&hash=item2a35fd263c
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taylorp035

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Re: Treadmill Dyno
« Reply #469 on: January 26, 2014, 07:17:42 PM »
It turns out the wires that I thought were to short out the ignition as a kill switch actually needed to be connected together.

So, once the carburetor was bolted, here are the results  ;D

http://www.youtube.com/watch?v=BUgktsKAOeM&feature=youtu.be

http://www.youtube.com/watch?v=oR26T07tPwM&feature=youtu.be


We broke a plastic elbow in the fuel line and the carburetor probably was getting too cold for it to run any more, so it never ran after this.  The 80 seconds in the 2nd video doubles our record for run time over our senior design engine.

taylorp035

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Re: Treadmill Dyno
« Reply #470 on: January 26, 2014, 09:48:01 PM »
Some photos of the test rig.






Quote
Any thoughts about a lubrication system?  I know that it's meant to run sporadically, but if wear starts to show up (presumably on the half-pipe channel first) do you have a plan to lubricate?
After the initial runs today, just having the valve wet was enough for it to run for the 80 seconds without any signs of things getting dry.  I'm thinking a slightly heavier oil than 5W-30 will improve sealing.  Maybe some 80W-90 gear oil would be more appropriate as we get the engine up to temperature (what ever that turns out to be).  After 80 seconds, the exhaust and center of the valve was only 105-110F according to my IR temp gun.  Granted, it was probably 40-50 F when it started, so.....

« Last Edit: January 26, 2014, 09:53:55 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #471 on: January 30, 2014, 09:34:48 PM »
A video of the exhaust flames and a new record run of ~2:40.

http://youtu.be/f30jm4fZ64M
http://youtu.be/XmS5Y7dMQ1o

After the long run, we disassembled the head and performed an inspection.  There were some burrs that had smeared around the valve in two places, but nothing too bad.  We shall see how it looks after a bit more running and if we need to make any changes to the oiling pattern.

We also re-balanced the flywheel by knocking off a fin since it was missing one.  In the long video, we tried to make it go faster, but the vibration went from almost nothing to quite bad in just a few hundred rpm's as we accelerated.  And then if you gave to much gas, it would 'pop' and loose it's combustion pressure.  On later runs, we cranked the springs down all of the way, but by then, the carburetor was too cold and it wouldn't start.  The exhaust was 200F after the long run.

Here is a frame from the exhaust video highlighting the flame inside the valve.  You can see the jet of fire shooting out 8)



If I can get my hands on a camera that does ~240 FPS or better, then I could actually see what's going on halfway decently.
« Last Edit: January 30, 2014, 09:44:39 PM by taylorp035 »

SparWeb

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Re: Treadmill Dyno
« Reply #472 on: January 30, 2014, 10:44:29 PM »
Taylor,
I've been looking at the hinge arrangement you have on the head for a while.  Just mulling it over...

If I was to make a diagram of the valve tube, as if it is a beam (warning this is gonna sound like school again) I think it would look like this:

\/                              \/               -Bearing
------------o------------              -Tube
    /\^^             ^^/\                   -Head Journal


The bearing pillow blocks push down on the extreme ends when the screws are tightened, while the journal provides support inward from the ends.  The journal support is rather widely distributed, but I think you'd agree that the maximum concentration of the journal's force is just beside the bearings.  So that leaves the center portion unsupported, except for the stiffness of the valve tube.  And if you tighten the bearings down, doesn't the center of the valve tube move up?  That would increase the clearance, not tighten it.

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taylorp035

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Re: Treadmill Dyno
« Reply #473 on: February 01, 2014, 07:13:21 PM »
Yes, I agree 100%.  But I don't think the problem with it leaking has to do with deflection of the valve or head.  The problem is that the force caused by the cylinder pressure is actually greater than the springs.  I need springs that are 2-3X stiffer at least.... with the springs cranked down 50% of their length, it is only providing ~300-400lbf for an area of .77 in^2.  I have a feeling that the cylinder is actually very well sealed, so the 9.5:1 C.R. is actually happening.  This also doesn't account for any force caused by the oil between the sliding surfaces.

The 1" diameter valve has 1/8" walls and is exceedingly stiff since it's only spanning 4.5".  Deflection I believe should be less than 0.001".  The head is also very stiff, one of the reasons why I made it so thick.  The first version of the head was not very stiff and it was deflecting 0.010-0.020" once the head bolts were tightened down.  I believe the cylinder pressure and the springs made it deflect another 0.004".  The spark plug location for this head is much better too for stiffness.
« Last Edit: February 01, 2014, 07:19:10 PM by taylorp035 »

SparWeb

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Re: Treadmill Dyno
« Reply #474 on: February 01, 2014, 11:21:32 PM »
OK
So a 10:1 CR will give 147 psi in the cylinder, without combustion, and the valve opening is (I guess) 2" x 1" rectangular area, then the force pushing up on the valve body (when not open) is 147*2*1= 294 Lb or roughly 300 pounds.  Springs are doing fine, then.  But when the engine is running, I thought combustion would cause a significant rise in pressure - about 5-10 times higher momentarily.  Memory fuzzy on details.  You must have factored that in, right?

What would happen if you weren't using springs? 
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taylorp035

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Re: Treadmill Dyno
« Reply #475 on: February 02, 2014, 01:35:22 PM »
To start with, no-heat added pressure at 10:1 C.R. is not air pressure x 10.  It's much closer to an exponential equation using PV=nRT.  With no heat, it should be 342 psi @9.5:1.  With the fuel, it should be 441 psi.  The area for the valve opening is .77 in^2, so that works out to 441*.77 = 340 lbf on the valve.  With a richer air fuel ratio and depending on the spark timing, that pressure could be much higher.  Hence the reason engines knock when you get the spark timing too early.  For low speed and small diameter pistons with high compression ratios, advancing the timing from 5 deg BTDC to 10 deg could increase the pressure by 50-100% since the flame covers the whole piston area so quickly (relative to crank rotation).

We could skip the springs, but it would probably be harder to get a consistent force on the valve.

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Re: Treadmill Dyno
« Reply #476 on: February 04, 2014, 12:27:34 AM »
Right. It's been a long time since I've used "adiabatic" in a sentence.    :-[

Any risk to the engine if you do remove the springs?
Have you been adjusting the spark timing?

Now you're going to need a dynamometer!
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taylorp035

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Re: Treadmill Dyno
« Reply #477 on: March 01, 2014, 08:54:38 PM »
Made it back to see the mini OHC engine run, after it experiencing poor performance right before competition last year due to an improperly sized carburetor and leaking poppet valves.  Now with all of that was fixed, a bunch of dyno runs were made and the results were pretty amazing.  The specs on it are 53 cc's, 14:1 C.R., nickel-chrome bore, and dual spark plugs with a SOHC.  Peak power recorded was 1.4 hp at 3,900 rpm.  With no load, it was able to idle down to ~550 rpm, which is pretty amazing for an engine that small.  At power levels above 1 hp, we were able to record efficiencies of 18-19%, with a peak of 19.7%, which is a record for us. Some more runs at the RPM's that it will see at competition need to be completed, but an average of possibly 11-13% seems to be where it's at right now.  Last year's engine averaged about 5% for comparison.  So far, we have not hooked up an O2 sensor for AFR measurements, so maybe there is a bit more efficiency to be found.  Adding an exhaust will probably help too.

Here is a video of it with no load.  Closer to the end of the video, we turn down the idle until it finally stalls out at ~500 rpm.  We really liked the sound that it makes.
http://youtu.be/hU5pT8_dWGY



« Last Edit: March 01, 2014, 09:04:11 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #478 on: June 15, 2014, 06:08:16 PM »
The results from this year's competition was 1020 mpg and 5th place.  The car was rolling very well based on our calculations, which meant we finally have validated Michelin's rolling resistance numbers and our drag coefficient.  Unfortunately, the engine was running super rich, most likely due to the increased engine bay temperature when compared to our testing.  Our calculations figure a 5% average engine efficiency, which is way lower than we were hoping for.  Peak efficiency on the dyno maxed out at 21.7% before competition.  Our estimated engine efficiency should of been 11-15% for the race, but the carburetor wasn't tuned very well for the conditions.  Two blown tires halfway into the afternoon hampered the efforts to adjust the AFR.  For the last run of the day, the team gambled on putting the best tires on the car and it unfortunately didn't yield a better result (the engine was probably even hotter by that time).  Interestingly, it seemed like all of the other teams were having similar issues, as the best score was 1211 mpg... a very, very close set of scores by the top teams.

Penn State Behrend's car is the white one on the far right.  76.5 lbs weight, ready to run with fuel.

 

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Re: Treadmill Dyno
« Reply #479 on: June 16, 2014, 12:41:54 AM »
A good result even though not close to last year's high point.  Were there attempts to adjust A/F ratio by "shot in the dark" or did you stick to a gradual adjustment plan?
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taylorp035

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Re: Treadmill Dyno
« Reply #480 on: June 16, 2014, 07:04:44 AM »
Adjusting the AFR is difficult, because during a burn, it varies widely, from super rich to super lean.  This causes the engine not to want to start.  Also, it's impossible to tune the AFR without the correct load.  The carb has an AFR screw for the low end and the main needle for the high end.  The carb needed the needle moved a bit, but once you do that, the AFR and idle screws need tuned a lot, making this a risky decision in the middle of a race day.  You can only drive the car on the track, so you wouldn't get many chances to tune the engine if you messed it up.   Also, the low end AFR screw is super sensitive, so it's hard to play with.  Varying air temperature for the intake also makes things a challenge, as the car heats up once the lid is put on.... this year, the nose of the car got so hot under where the front window was, that it was getting soft.  Some teams put aluminum foil under the driver's feet... I can't imagine that helps visibility out of the already sketchy windows.

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Re: Treadmill Dyno
« Reply #481 on: June 16, 2014, 12:55:11 PM »
So... next year's race will be in Nome Alaska?  ;)
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taylorp035

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Re: Treadmill Dyno
« Reply #482 on: June 16, 2014, 09:34:10 PM »
It's interesting, because every year, the weather conditions are different, from windy to calm and then from cold to hot and sunny to stormy.  Yet most teams aren't prepared for varying situations.  Being able to have your car run at it's best in any weather condition is important.  In the 5 years I've been there, I bet the insides of the cars has varied from the coldest to the hottest by 100F+.  Just goes to show, learning how to make the best supermileage car takes more than a year or two...  it really takes several generations of students to pass on the knowledge of all of the lessons learned.

And another thing that is so great is that there is no perfect answer for a car and that there is always room for improvement.  A perfect car in the perfect conditions could achieve 6-10,000 mpg... yet only two teams in SAE history have cracked the 3,000 mpg barrier and only a handful to break 2k mpg. 

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Re: Treadmill Dyno
« Reply #483 on: June 17, 2014, 01:28:48 AM »
Did you install any sensors to help set it - oxygen / air flow / throttle position, etc.?

Did the unique valve system perform well?
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taylorp035

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Re: Treadmill Dyno
« Reply #484 on: June 17, 2014, 07:15:04 AM »
No, No, No, and No.  We had an external O2 sensor that we could clamp to the end of the exhaust pipe, but that's it.  Throttle position was up to the driver.  On our EFI test engines, we have MAF's, but not on the carbureted engines.  I have seen teams who have attempted a servo controlled throttle to vary the throttle % during a burn... fairly complex to effectively do so.

The engine in the car this year was the 53 cc SOHC ~14-15:1 CR custom head with dual spark plugs.  It ran very well and experienced no problems that we know of, just that the AFR was way too rich. 

The rotary valve for the SAE car has not been tried again.  It needs to be re-sealed and glued to be run again.  The only reason to do this is for the satisfaction to see it run, since no one would risk running it at competition.  My homemade rotary valve still needs some attention and probably a bit of tuning on the AFR front..... which is hard to do with no O2 sensor and a coil wrap pull start.

taylorp035

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Re: Treadmill Dyno
« Reply #485 on: January 05, 2015, 08:29:23 PM »
Here is a video of my personal rotary valve 3.0 design running.  Probably my best engine video yet.  Completed the whole thing over Christmas break.  This version of the engine already has more run time on it than all of the previous versions combined.  I can't wait to make a dyno for it.


https://www.youtube.com/watch?v=iW7MRZB7Ris&feature=youtu.be


Version 3 has a floating bronze seal in the center that gets pushed up by the combustion pressure.  The springs are there to lightly pull up so it doesn't fall down during the intake stroke and cause a vacuum leak.  The engine was designed to be a 10.2:1 compression ratio, but currently is about 8:1 since the seal is up in the air a bit.  A compression test revealed a healthy 135 psi.




In other news, we also found the reason(s) why our mini 53 cc engine wasn't very efficient at competition.  Basically, it was severely worn out, with the valves, valve guides, and valve seats pretty much past their usable lifespans.  A new set of valves, seats and some sleeves for the guides will get it back to new again.  This explains the halfway decent efficiency at high rpm's and very low efficiency at lower rpms.

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Re: Treadmill Dyno
« Reply #486 on: January 10, 2015, 11:25:02 PM »
Hey thanks for the update Taylor.
Gotta love the brass for journal bearings and the like.
But is it exposed to the combustion side of the chamber?
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taylorp035

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Re: Treadmill Dyno
« Reply #487 on: January 13, 2015, 07:16:17 AM »
The brass piece is a cylinder that goes all the way to the combustion chamber.  It has the sparkplug, half-pipe journal surface, the port and the combustion chamber milled into it.  On the outside, there is an o-ring and some teflon backers for sealing.

The brass piece floats and is pushed up by the combustion pressure.  The springs prevent it from dropping back down.


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Re: Treadmill Dyno
« Reply #488 on: January 15, 2015, 12:46:58 AM »
The pipe is more complicated than I thought.  How hard is it to make?
Is it machined as one piece?  Can the machining of each path be completed from the port side, or do you have to do some tricky things at the bottom of the hole bored into the bar?  Now that I see the way the passages are separated, I wonder if maybe an insert that pushes in from one end would be easier to make.

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SparWeb

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Re: Treadmill Dyno
« Reply #489 on: January 15, 2015, 12:48:06 AM »
You have too many files open Taylor.
If I did that on my computer, Inventor would crash!
:)
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taylorp035

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Re: Treadmill Dyno
« Reply #490 on: January 20, 2015, 05:36:25 PM »
Last Friday, we clamped the engine to a table and let it run for 73 minutes straight!  The previous record was 6 & 1/2 minutes.  It was idling at 1100 rpm with a few minutes of goosing the throttle (up to 4k) and low as ~800 rpm.  For the last 10 minutes, we upped it to ~2k rpm... it finally got a bit hot on the exhaust end and I think burned the oil off the edge of the seal, which then greatly increased the friction and lead the end of the valve to turn blue (measured at 400F).  You could hear the #25 chain start to groan under load, so I shut it off.  The head/ block were about 260F, which isn't too bad considering the complete lack of cooling.  There were some bubbles in increasing intensity coming around the seal near the end, which leads me to question how well the o-ring held up.  I can't wait to tear it apart.  Next step is to put it on my friend's go-kart.

The pipe is more complicated than I thought.  How hard is it to make?
Is it machined as one piece?  Can the machining of each path be completed from the port side, or do you have to do some tricky things at the bottom of the hole bored into the bar?  Now that I see the way the passages are separated, I wonder if maybe an insert that pushes in from one end would be easier to make.

We've made two valves at this point.  Both started with precision ground steel, which takes care of the OD.  It is machined as once piece, drilled from both ends and then each of the openings in the center get milled on a mill or 4-axis lathe.  Generally, you can't mill the transition between the drill operation and the mill operation to be very smooth, so some dremmel work is required.  You can make the path better for air flow, but it increases the machining complexity.  A nice multi-axis lathe could do a better job... kind of like how custom intake runners are machined in normal engine heads for race cars.

Here is a video of my mini 4-axis mill cutting the valve.  The rest was done with a 3/4" drill bit.
https://www.youtube.com/watch?v=qBgn5FxVOYs


You have too many files open Taylor.
If I did that on my computer, Inventor would crash!
:)
That's nothing.  Running CFD, I pushed my laptop to 59 Gb of RAM used (16 Gb actual ram).  A solid state disk drive helps in that endeavor.  At work, at times I have had 40+ applications open at once (I do a lot of data mining across different programs) and it only has 4 Gb of ram and the motherboard tends to only allow me to use 2.2 Gb of it... the rest of it gets swapped to an encrypted  disk drive, which is really slow.
« Last Edit: January 20, 2015, 05:44:59 PM by taylorp035 »

SparWeb

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Re: Treadmill Dyno
« Reply #491 on: January 21, 2015, 11:11:15 PM »
I fear you'll find a mess where the o-ring once was.  Hope the insert isn't too hard to get out.
Maybe a piston ring would work?


No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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taylorp035

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Re: Treadmill Dyno
« Reply #492 on: January 22, 2015, 07:03:29 AM »
I tore the head apart last night and everything looked just fine.  O-rings were good and the sealing surface wasn't too worn or had any major scratches.  There was some gooey tar in the combustion chamber and smeared around the valve, so we are going to advance the "cam" timing by a few degrees and see if that helps.  On the plus side, any carbon or tar build up helps seal it better.  While we had it apart, we machined the spark plug countersink so it's now flat, which should stop some of the leaking.  The exhaust was nice and clean, but the intake had some of the tar, so we believe some of the charge is going back into the intake while running.

SparWeb

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Re: Treadmill Dyno
« Reply #493 on: January 23, 2015, 08:40:58 PM »
Again, I'm impressed!  I really didn't think the o-ring would survive.

Have you given any thought to the air exchange process and how complete the burning may be?  Air/fuel mix swirling about the chamber - you seem to be equipped to do CFD analysis, so have you done any for this subject?  Have you done any exhaust gas analysis?  (Maybe you've mentioned it before...  this thread is getting really long!)
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taylorp035

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Re: Treadmill Dyno
« Reply #494 on: February 08, 2015, 06:06:48 PM »
https://www.youtube.com/watch?v=8P_YTQQUN3A&feature=youtu.be
Today's run.  Now about 2.5 hours of run time total, and approximately 1/4 gallon of gas total.

I haven't hooked an AFR gauge to any of my rotary valve engines yet.  I have done some CFD on version 1.0.  This afternoon, I just set up version 3.0 in CFD, so I shall see what it looks like, especially with a computer that is 3X faster and 4X more RAM to play with.

Mixing of the fuel and the air should be very good compared to a poppet valve configuration.

Version 1.0 theoretically had a volumetric efficiency of 107% at 3,000 rpm based on my basic simulation.  Here is a screen shot from it and a video of some particles from the end view.
https://www.youtube.com/watch?v=uG0dRqNiBQk