Data Logger again

[lohring]

As I mentioned before, I have been using the Eagle Tree data logger to test engine modifications. In the graph below the blue lines show the origonal engine rpm and cylinder temperature with improved port timing. The yellow lines show the improvement from reducing the head clearance and head fin area. The purple lines show the improvement from adding holes in the piston skirt and liner into the secondary transfers. All runs were made with the same setup and prop. I could not have told any difference between the runs without the recorder.

Lohring Miller

 

[TimD]

Lohring,

Thats sooooo cool B)

Thanks for sharing that with us - I guess you are happy with that telemetry system then?

 

[GTR]

Lohring

Is that on a Rossi 21 goldhead OB? Very interesting data although I noticed the accentuation of the dips with the piston port modification, possibly not in the ideal position (optimum) given the flatter yellow line.

Still glad you were happy to share this. Really dumb question did it produce a visible difference in speed or lap times?

B)

 

[nitrotoys]

Very Interesting on the changes of things you did.

Alittle extra Rs out of the engine.

Thanks Lohring for testing it for us and shairing.

Tom

 

[Mark]

Lohring,

I really think you should get the exhaust gas temp sensor. The temps of the exhaust gas shows how the mixture is set. You should get the best performance at a particular heat range and use this to tune the engine. I think you can get readings from the settings on the 3rd channel and compare them with the exhaust gas temp.

 

[lohring]

The engine might have been a gold head, but when I got it, it had a car air cooled head. The porting had been changed, and I again altered it to 180 exhaust, 126 transfers, and 68 ATDC intake closing.

The exhaust gas temperature sensor is comming. Some of the variation in runs is because they were from different days. The boat was run on our club course which causes the rpm variation as the engine pulls down in the corners. I promise that I didn't drive in the same lane for every run. Also, the sampling rate was much lower on the first run. I transferred the data to a spread sheet to plot the comparisons. The software that comes with the recorder is more limited and harder to do these comparisons with. A good spreadsheet program can help a lot.

It answered questions about whether piston holes work. I already knew that higher cylinder temperatures and reduced head clearance would help. I reduced the clearance to .003 as measured with Plastigage. After running, the head has a shiny spot that matches one on the piston. The recorder should be a great prop testing and setup tool when I get the beta test water speed sensor.

Lohring Miller

 

[Rules]

Hi Lohring, As you found out, the use of Plastigage gave you collision when you are running the squish real low. You measured the "static clearance" not the "dynamic running clearance". To measure the dynamic, you remove the backplate, then use a nylon rod/stick/Bondus/whatever, placed under the piston crown. Then hold the stick in place and rest the other end of the stick on the table. Use a leather/plastic hammer to carefully tap the top of the liner to insure the piston is at absolute TDC. There will be no movement of the crank at this TDC. Now carefully measure the piston depth with a dial depth gauge with attached shoe. Take readings in several places to inspect if the piston crown is slanted, correct if needed if you wish. I always sanded the crown till I got an even reading all around. Hold the gauge plunger after you take the reading, and place it against the button. Make sure you see daylight under the shoe which double checks for actual positive clearance, not negative if you do not see daylight. Then release the plunger to get the dynamic reading. Hundreds of modelers think the static reading is correct, but the running, which takes all the bearing clearances into account is what you really need to know. Another thing you mentioned, the piston should have a complete ring if a collision exists, not just a single spot, unless the collision is extremely light. You might want to check for something bent, incorrectly machined, or mis-drilled from the factory. Make sure your window ports are very large and fully open from transfer crack open to the bottom of the stroke. Bevel both the liner and the piston to match the gas flow, and insure the top of the piston window bevel starts just a fraction below the seal band, seal ring area. You want to evacuate as much of the trapped fuel mixture from under the piston as possible, hence the high placed piston windows. Round the bottom edge of the top window bevel a few thousandths, if left sharp, then the edge will erode in time. Leave .10 to .125 high band of piston material at the bottom of the skirt below the window. This holds the piston from deforming and adds strength to the skirt area. This area is the only skirt high pressure area left, to resist piston cock, you might consider golfballing .003-.005 random for oil retention in piston/sleeve or both. Good luck... Have fun....John in Huntsville

 

[Tom v.d Brink]

Lohring,

why the change to a water speed sensor instead of the air sensor that comes with the unit now?

did you find it giving bad or inacurate readings?

also can you show how you installed the pickup tube now? i am in the process of putting a system in my boat but can't quiete work out the placement of the air tube yet.

thanks

Tom

 

[izitbrokeyet?]

Rules,

Great post dude.

 

[Mike Hughes]

I promise that I didn't drive in the same lane for every run.

Oooooh You didn't have to tell me that Lohring. I have seen you drive. You couldn't even stay in one lane if you tried. :lol:

Mike

 

[lohring]

Mike, you act worried. I didn't know you were going to run A mod this weekend.

I got very bad data from the air speed pickup until I isolated the recorder with lots of foam. I then got a lot of scatter, but reasonable speeds. I built a pitot/ static probe because I thought I was getting an inaccurate static pressure reading inside the recorder box. It seems that the very low air pressures that the sensor reads are easily swamped by vibration of the recorder. The air pressure at 100 mph is a few inches of water, while the water pressure at the same speed is around 150 pounds per square inch. The sensor will be about the same size, but the huge differences in force measured should overcome most vibration.

Below is a picture of my air pressure pickup. The static pressure dumps into the recorder box through very small holes in the outer tube while the impact pressure is fed to the recorder sensor directly by the inner tube.

Lohring Miller

 

[lohring]

Below is the graph of the speed plot. I didn't confirm the accuracy with a radar gun, but it looks reasonable. The resolution probably isn't good enough to see the cloud of points the average line goes through. Tue sampling rate was low, but that doesn't explain the scatter.

Lohring Miller

 

[Mike Hughes]

OK Now Lohring is going to spear me with that air pressure pickup. This aint a joust Lohring. Come on man, get out of the mid evil days.

 

[lohring]

I'm putting it back on just for Lake Waghup. I call it a duck f....er.

Lohring Miller

 

[nitrotoys]

LOL Lohring, Duck something or other,

Awesome info and great pics of the set ups.

Tom