Author Topic: Treadmill Dyno  (Read 128323 times)

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taylorp035

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Re: Treadmill Dyno
« Reply #90 on: April 16, 2011, 04:29:14 PM »
I just had an excellent idea for my supermileage car, but I need a little help. 

Our special bicycle tires can be run in a tubeless configuration, but we currently only own non- tubeless rims.  I found some products out there that will basically seal over all of the holes.  I was wondering if anyone had some experience with this?

The reason a want to do this is because the tubes substantially increase our rolling resistance.  According to Michelin, it actually goes up by a factor of 3, so this is a rather important issue.


And on a different note, the EFI engine plan has been officially been axed.  After running it a few more times last friday, the efficiency was in the 7-10% range, which is lower than the 13% on the stock engine.  We then pulled the injector off the engine and added a carburetor.  The result was a fireworks show coming from the exhaust and air intake.  We think more gas was blown out the intake than burned in the cylinder....  Next week we are getting an oscilloscope with an attachment to read the spark plug wire to determine if the problem is the spark or the engine.  It is possible that the engine was damaged, especially after taking a temp reading around the spark plug of 415 F  :o  We took the head off after this reading and found nothing wrong, but we don't know very much about engines.


Also, the cup holder and air duct were carbon fibered, so when the car gets back, everything will go in it quickly.

The paint shop was contacted and they reassured us that it would be back by the end of the month. 

Madscientist267

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Re: Treadmill Dyno
« Reply #91 on: April 16, 2011, 05:24:52 PM »
Sounds like at the very least you've got some valve damage of some sort, or a timing issue. Hard to say with a brief description.

Compression check?

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #92 on: April 16, 2011, 06:25:55 PM »
Some of the details that I could put in words...
The engine seemed like it was only firing every other time (every 4 revolutions).  For about 2 seconds, it once fired properly.
Also, when messing with the spark advance, we were able get it to run reliably once we got the spark advance to ~1-3 degrees before TDC when below 1800 rpm and ~4.5 degrees at 2200 rpm.  At full throttle with no load, it would max out at 2400 rpm.
Also, I would rotate the flywheel 1/2 a turn before every start so the starter motor could get past the compression stroke.  When I did this, it would sometime fire.... tried to take my hand off about 3 times.


Madscientist267

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Re: Treadmill Dyno
« Reply #93 on: April 16, 2011, 06:41:24 PM »
Not sure exactly what, but something is definitely wrong.

The fiery ports indicate valve leakage and/or timing, and this may be compounded by additional compression loss from a warped head (415F? ouch)...

Don't forget that there are two timings; valve and spark. They can have similar behaviors sometimes depending on how close to 'dead-on' (but not quite) they are.

Compression check would be the first thing I would go after.

Also check for distortions in the valve stems. B&S as I recall uses a fairly close tolerance, which isn't 'adjustable', but may have grown shorter due to overheating.

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #94 on: April 16, 2011, 07:29:40 PM »
Thanks for the advice.  We will definitely try it on a less abused block.  I will also get the expert opinion from our adviser. 

When running the EFI engine a few weeks/months ago, the temp would only get to ~275 F, even after running it at full throttle for 1/2 hr.

REdiculous

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Re: Treadmill Dyno
« Reply #95 on: April 16, 2011, 08:22:33 PM »
What tires are you running and what size? Steel or aluminum rims? What 'products' did you find?

I think I'd probably try rubber cement to fill the holes since you could glob it on thick and still have enough to go around. If you air up while the glue is still tacky maybe the pressure might push it into the holes a little?..

I'm running a pair of 20x1 3/8 street tires w/ tubes on my bike and with enough pressure I can coast for a looong time. I usually over-inflate by at least 5 psi - harder ride and greater chance of failure but it's worth it. I didn't realize no-tube would be that much better.
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taylorp035

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Re: Treadmill Dyno
« Reply #96 on: April 16, 2011, 08:42:45 PM »
http://www.chainreactioncycles.com/Models.aspx?ModelID=18703

We are running 20" x 1.75" rims, made out of aluminum.  The brand name is Stollen.
I would like to have some carbon fiber rims that are tubeless, but I bet they are super rare in 20" form.

The front two tires are these.  Click on the Michelin link.  We have the expensive tires.
http://www.eshopsem.com/

According to several sources, if you go tubeless and pump them to 6 bar(88 psi), the rolling resistance goes down to a tiny 0.0008 coefficient.  If you have tubes, it goes to about 0.0024, but I have no proof of that.

Last year we ran a paper thin Michelin tires.  We pumped them to 50 psi.  Later we found out that they were good for 73 psi.

For comparison, most normal bike tires have a rolling coefficient of about 0.006.

The problem is that I don't want to ruin tires that are not replaceable.  Also, we have put a lot of work into lacing those rims.

REdiculous

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Re: Treadmill Dyno
« Reply #97 on: April 16, 2011, 11:33:11 PM »
20x1.75..standard size. I kind of expected you to be using 20x1.5 for some reason.
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Re: Treadmill Dyno
« Reply #98 on: April 17, 2011, 12:36:16 AM »
About spoked wheels:

http://www.amazon.com/Bicycle-Wheel-3rd-Jobst-Brandt/dp/0960723668

Just an idea.  It's a great book from the engineering perspective.  May be some tips about spoke arrangement you'll find useful, but not much about tires, though.

I can't tell you much about the tires either.  My understanding is that you put in the work necessary with those tires, because tubes are NOT an alternative.   I had a few old acquaintances raced bikes in provincial finals, and could have answered your question in detail.  Long ago....
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taylorp035

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Re: Treadmill Dyno
« Reply #99 on: April 17, 2011, 12:13:15 PM »
Quote
20x1.75..standard size. I kind of expected you to be using 20x1.5 for some reason.

Wider tires have less rolling resistance.  Air drag is not a concern because we have wheel fairings.



These tires are amazing.  Radial construction (only ones you get get), no tread, and good for 102 psi.



REdiculous

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Re: Treadmill Dyno
« Reply #100 on: April 17, 2011, 02:16:39 PM »
Who told you wider tires have less rolling resistance? I'm pretty sure the opposite is true which is why skinny 10-speed tires rule for racing.

I didn't feel like there was a big difference between 1.75 and 1.5 but the 1 3/8 tires seem to roll forever in comparison. My 1 3/8 tires are about as wide as 2 pencils side by side - comparable to 10-speed tires. The 1.5 tire is about twice as wide, or about 4 pencils side by side.

102psi, wow! That's double what my tires can take and they're rock hard at that point. 8)
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Madscientist267

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Re: Treadmill Dyno
« Reply #101 on: April 17, 2011, 03:42:39 PM »
Quote
pretty sure the opposite is true

Tending to agree here, at least in the logic department. No real world experience to back it up tho.

Rolling friction goes up with the amount of rubber in contact with the road. That's one reason the tire pressure is so high. To keep them from developing the 'flat' spot which would put 'out-of-ratio' rubber scrubbing the road as the tire rolls.

I'd think you'd want to get as close to a laser-cut razor edge as you could possibly get if you want to keep the friction as low as possible.

Sure, at some point it becomes impractical to go too 'sharp'.

Maybe the weight load on the tire comes into play, and PSI (in terms of rubber to road) gets off balance.

... trying to think of a reason to go wider ...  ???

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #102 on: April 17, 2011, 05:02:53 PM »
Quote
Who told you wider tires have less rolling resistance? I'm pretty sure the opposite is true which is why skinny 10-speed tires rule for racing.

Several sources, including Schwable and my supermileage book (the team that got 15,000 mpg equivalent).  At the same pressure, narrow tires are worse because they squish more, which is they absorb more energy.  This is also why people say that larger diameter tires provide less resistance, but my book says this is only true because the ground is too soft (polished concrete is fairly hard).  But narrow tires can be pumped up more.  If you have too high of a pressure, the tire will actually get too bouncy, which can cause a significant amount of rolling friction.

http://www.schwalbetires.com/tech_info/rolling_resistance

Most importantly though, how the tire is constructed changes the resistance.  The tire in my picture is the only "radial" bicycle tire made that we know of.  All other tires for bikes are "cross ply".

We have run narrow tires before at 140 psi, but that's because the wheels stuck outside of the car body.



Here are the paper thin tires:



The tubing on the rear end is 1" square and the sprocket is #35 chain @ 134 teeth  for reference.  The tire is a 1.75" wide tire.  Side wall thickness is about equivalent to about 3 sheets of cheap notebook paper.  The rubber part is less than 1/16" thick.
« Last Edit: April 17, 2011, 06:04:47 PM by taylorp035 »

REdiculous

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Re: Treadmill Dyno
« Reply #103 on: April 17, 2011, 08:23:25 PM »
I kinda get the point they're making but I'm not really sold. It seems like they're saying, "at the same pressure that just so happens to favor a wider tire"...

Look at the pics they show on the right at the bottom. I've never seen a tire that flat, except for when it was actually flat and unridable. ???

edit..incidentally, I checked my 1.5 tire and it's rated for 125psi (I've been running it at 35psi). My 1 3/8 tires are rated for 45psi.
« Last Edit: April 17, 2011, 08:58:10 PM by REdiculous »
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taylorp035

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Re: Treadmill Dyno
« Reply #104 on: April 23, 2011, 05:18:27 PM »
Yesterday was a success in general.  We ended up converting an engine to run on points and a coil, which turned out very good.  It looks like the engine that we will use in the final car.  We will probably transplant the flywheel and coil stuff to our brand new engine with the new head.  The we will port and polish it and do a final dyno run.

The coil set up used a lot of power.  While running, it was pulling 80 watts, , which made the coil really hot.  We had to install a switch so it wouldn't drain our battery pack so fast.

While running the treadmill dyno yesterday, the key that holds the 3" pulley on the treadmill motor came out.  Unfortunately, some of the material stayed inside and jammed the pulley on the shaft.  After about an hour of trying various things (hammer, pipes, hair dryer, C- clamps), we gave up and decided to keep running the dyno.  After a few more minutes, we sprayed some lithium greese inside of it.  Once we got it up to about 4k rpm, she decided to let go and fly off the end of the shaft.  The belt didn't fly too far, but the pulley spun on the table for about 20 seconds ;D  It took about 40 seconds for the treadmill motor to stop, since it had no load at the time.

When we got it all back together, we did a couple more efficiency runs using the brand new engine, which yielded 10.1 % compared to the 9.7% for the points engine.  Both percentages were lower, probably caused by the bent pulley.

Also, we got the solenoid clutch working.  Only about 10 min more work is needed for it to be done.  It does take two 14v packs to run it, but as long as it is reliable.

I also did a careful discharge of our lipo batteries to see if they could hold 14v while under load.  It turns out that the computer actually needs >14 volts to run, but putting 26v to it would cause too much heat in the voltage converter.  I ran the 1350 mah 4s lipo pack at 4 amps.  It finally dipped below 14v after 1183 mah, so I deemed it a success.  The computer will pull less than 1 amp.

The carbon fiber for the cooled seat fan was finished and the cupholder was also worked on.

Sorry for the lack of photos.  My camera was accidentally left on and the battery was dead.  Next week, the car should be back from the paint shop and we will put everything in it --> lots of photos then.


EDIT:

I looked at the data from yesterday's dyno runs and calculated the efficiency.

Once I added the # of lightbulbs in, the numbers came out as follows:

The points engine was 10.0% efficient at 1.4 hp.  Peak power was a new record of 2.36 hp.

The brand new engine was 11.3 % efficient at 1.54 hp.

Both efficiency runs were done with the same mangled pulley, hence the lower numbers when compared to before.  The belt was jumping a quite a bit due to the pulley.


I think next week we should add the coil and points to the new engine and possibly port + pollish the intake and exhaust.  I think there is a good chance that the new engine has some differences that may increase the efficiency.
« Last Edit: April 23, 2011, 06:46:43 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #105 on: April 26, 2011, 05:26:06 PM »
« Last Edit: April 26, 2011, 06:08:52 PM by taylorp035 »

Bruce S

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Re: Treadmill Dyno
« Reply #106 on: April 26, 2011, 06:29:48 PM »
That second one sounded like you have something hitting? Nice response to the governor or throtttle.
 
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taylorp035

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Re: Treadmill Dyno
« Reply #107 on: April 26, 2011, 07:00:32 PM »
We aren't sure yet what the sound is yet.  It has the ringing sounds from the flywheel, which suggests that it is the gap on our cam lobe (you can't see it in my pictures) hitting the point.
All of this is on the brand new block, which makes the engine sound significantly different. Much smoother and quieter.  Probably due to the better muffler (last one was pretty much a straight pipe).

As for speed, it really accelerates.  Much faster than even the EFI engine.  Probably capable of doing 2k to 5k in under a second (almost as if it has no flywheel).  With no clutch on the shaft, the flywheel almost stops during the revolution around 800 rpm.  Our throttle didn't have a return spring, so sometimes while we weren't holding it, it would shoot off to 5k+, which is pretty scary with a homemade flywheel that is held on with essentially 1/16" thick aluminum...  Definitely need get our bicycle speed selector hooked up for the throttle cable.  Top speed is probably near 6k, but the con-rod will break.  B&S says the redline should be 4k.

This friday we should port and pollish it and throw it into the car (I hope it comes).

Unfortunately, we shorted out the Doc Wattson twice in the last week, and it looks like the second time killed it.  While we were running the engine, a wire broke off the kill switch and touched our metal table  :(






Madscientist267

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Re: Treadmill Dyno
« Reply #108 on: April 26, 2011, 09:28:27 PM »
What's your dwell on the points?

Not sure exactly of the 'antics' (lack of a better word) of a doc wattson, but if thats average current, ~5A seems WAY high. Is the coil warming up?

It made me think of a story my parents told me about a trip from connecticut to florida in an old 6V beetle, where during a stop for fuel, the regulator on the generator stuck shut and fried the genny. My dad ripped a wire off the generator (details escape me) to stop the fire, leaving the system with no starting or charging capabilities.

They ran the remainder of the trip off the battery, parking at the top of hills and such to restart the engine, driving only during daylight (it apparently crapped out mid afternoon), and stopping when it rained so they didn't have to run the wipers.

How does this apply? If the average current for them was as high as what I'm seeing here, the battery would have croaked north of DC.

They never mentioned charging the battery throughout the trip (even after the short sucked some juice out of it).

Your points should be open most of the time, only briefly closing just in time to open again to fire the plug. 5 degrees comes to mind as a general rule, IIRC. The less the better, but too small and the contacts get bouncy and firing becomes irratic.

Definitely explains your excessive battery drain.

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #109 on: April 26, 2011, 09:47:43 PM »
Quote
but if thats average current, ~5A seems WAY high. Is the coil warming up?
I would say that is an understatement.  After 5 min of running, the coil was measured at 150F.  Current was 7 amps average.  I can't recall the current draw when using the 4s Lipo instead of the 4s LiFE battery on the coil, but I think I remember the meter reading 140 watts instead of the 80 watts....   When we opened the gap on the points today to about 0.1", it was reading about 62 watts and the engine was running its best.  Obviously, this gap was way too big.

Note:  We have to use the 1350 mah 4s Lipo  (rule says <1400 mah and 12v).

I would guess the point is open closer to 10 degrees.  This may be too long.

Quote
Your points should be open most of the time, only briefly closing just in time to open again to fire the plug.

I see what you are getting at.  Making a lobe that shape would be more difficult.

Since we are only running the engine for a few seconds in the car, this shouldn't be a problem, but things do get toasty on the table.  Quite honestly, the engine will probably overheat before the coil does (limited air cooling).  I am seriously thinking of installing the extra 0.2A 12v box fan in the engine compartment to keep things happier.  The carbon fiber will melt too if things get too hot (the engine plate, the axle mounts,....).  The tire will probably explode too.


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Re: Treadmill Dyno
« Reply #110 on: April 26, 2011, 10:40:52 PM »
Many older vehicles used a ballast resistor in series with the ignition coil to limit the current (sometimes it was bypassed during starting).  I wonder if one could help here.  Since it's a relatively low compression engine it probably doesn't need all the energy that coil can produce to jump the gap.

If you want to try this I'd suggest adding 1-2 ohms (10 to 20 watts) in series with the coil with a switch across the resistor.  That way you can make a simple comparison to engine performance with and without the resistor in circuit.

taylorp035

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Re: Treadmill Dyno
« Reply #111 on: April 26, 2011, 10:49:53 PM »
That's a good idea.  We bought some 50w 1-ohm resistors which would work well for this.  Only issue would be finding a heat sink for it.  Maybe the engine mount rail.  Would have to be careful to not leave it on for too long.  I'm think we will have to buy another Doc Wattson for sure. 

Madscientist267

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Re: Treadmill Dyno
« Reply #112 on: April 26, 2011, 10:54:09 PM »
Good call on the ballast! I totally forgot about that...

Might even be able to get by with even higher resistance. 4R7?

That would bring things into the 2-3A firing current, and if dwell is set low enough, the average current would be in the mA range instead of whole amps.

Go with as little dwell and as high resistance as possible to obtain reliable spark under all conditions (RPM, load, etc). Your power requirements will drop significantly.

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #113 on: April 28, 2011, 02:10:37 PM »
I did another test today with the coil to see how many amps it was pulling with the LiPo battery (~15v under load).  Turns out it was more than 10A, at which point my multimeter wouldn't read any higher.

After running the engine for 2 minutes, the coil was 190 F....  We will definitely have to do something about it.  Based on our engine testing, the LiPo battery should last at least 2 runs.  We have 3 LiPo batteries, so we can swap them out every run.  One of those 3 will have to run the computer and probably the brake light.  Then I will need 1 or 2 LiFe batteries for the cooled seat and the last 2 for the clutch and starter motor....  That make a minimum of 4 separate circuits, 5 to make things happy.  I hope the computer runs on 12v, which then we can have the computer, brake light, the cooled seat, and the starter motor all on one circuit.  If we can get the clutch tuned to the point where we only need 12v, then everything will be perfect.




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Re: Treadmill Dyno
« Reply #114 on: April 28, 2011, 05:08:59 PM »
Would it be possible to replace the two clutch solenoids with a pair of electric lock actuator motors from a car at the salvage yard?  At least they don't require any power to hold, only to switch states.

taylorp035

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Re: Treadmill Dyno
« Reply #115 on: April 28, 2011, 05:30:07 PM »
We have a servo that will is good for 300 in*lbs, which would also work.  Maybe we could actuate the starter motor and solenoid with the same  potentiometer (it has 3 outlet ports....).  Only thing would be that the starter motor would run while the clutch is engaged... it should work.


We also got an update from the paint shop.  They said they wouldn't be done til Saturday (last day of April like the promised...).  Hopefully we can pick it up then.
« Last Edit: April 28, 2011, 05:50:09 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #116 on: April 30, 2011, 03:55:21 PM »
http://www.youtube.com/watch?v=M54zXwjRp_o

http://www.youtube.com/watch?v=jW8IP-6N5Lg

These are the new videos with ported and pollinated intakes and exhaust.  Just from revving them on the table, the performance is much better, especially in the top end.  We must of hit 5-6 k at less than 1/2 throttle.

The intake originally had the cross sectional area a little bigger than a sharpie marker.  Now it is around 3/4" in diameter.

We also found out that our brand new engine was pretty much destroyed, caused by a lack of oil.  We are not sure how long we ran it for with no oil, but it wasn't very long.  After tearing it apart, we would some real nasty grooves in the cylinder wall and on all of the bearing surfaces.  The engine in my two videos probably has parts from 4 other engines at this point.


Last night, we also swiss cheesed all of the components on the rear axle, probably cutting 1/4 - 1/2 pound.  Also, the wheel covers were clear coated and the cooled seat fan was glued to the air duct.

Today, we are making a new axle for the starter motor.  Having a 4-axis mill makes flat spots a breeze ;D  I should have a video up shortly on that.
I have also been hard at work finding software to make g-code out of a 3D file.  Obviously the companies who sell this type of software are very strict about free software...


EDIT:  Milling some flat spots

http://www.youtube.com/watch?v=yyepHG6iGyE
« Last Edit: April 30, 2011, 05:12:29 PM by taylorp035 »

zap

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Re: Treadmill Dyno
« Reply #117 on: April 30, 2011, 05:11:29 PM »
The first video... that engine seems to be smooth as silk!

"Rumble with 14 Robots!" ;D
« Last Edit: April 30, 2011, 05:13:24 PM by zap »

taylorp035

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Re: Treadmill Dyno
« Reply #118 on: April 30, 2011, 05:15:00 PM »
Quote
Insert Quote
The first video... that engine seems to smooth as silk!

"Rumble with 14 Robots!" Grin

Yeah, 14 robots was a new record, the old was 8 I believe.  None of the robots were mine.

As for the smoothness, yes it was very nice.  The videos don't give the rpm levels justice.  Much more impressive in person.

taylorp035

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Re: Treadmill Dyno
« Reply #119 on: May 02, 2011, 08:57:23 PM »
Was able to do 2 efficiency tests with the new ported and polished engine + points.  Came out to 9.4% at full throttle and 3800 rpm @ 2.36 hp (new record!).  At 2/3 hp, we got 8.7% at 2800 rpm.  Not sure yet why the numbers are so low.  I'm going to triple check my excel calculator, but I feel that it is the engine.

If things work out, my brother and I will spend the afternoon messing with the timing and different power levels.

The only variable at this point that has held constant with the lower efficiencies is the extra light flywheel.  I really don't want to give that up, but there is a good chance that this is a significant factor.  Adding mass to the flywheel will be difficult at best.

In a few minutes, I will run the mpg numbers vs. flywheel mass to see if it is worth it to have a lower engine efficiency.

EDIT:  After running looking at the graph, the difference in mpg between the two flywheels is 10 - 15%.  This is not quite as much as the current 20-30% less efficiency than the stock engine.
« Last Edit: May 02, 2011, 09:00:18 PM by taylorp035 »