Plasma Ignition

Originally posted by geek Do me a favor, keep this same setup with the NGK plug, boot not used, just like you show in this last picture.    Now, take and hook up that braid for the Nology wire and lets see if this changes things.     It may take some time, to see any change.

I did it several times and there wasn't much difference. Then I did put boot back. Breakdown started at 200 psi. Then I did put quite lot of silicon grease between boot and plug ground. That did help at least until 250 psi.

Originally posted by shmot Originally posted by geek Do me a favor, keep this same setup with the NGK plug, boot not used, just like you show in this last picture.    Now, take and hook up that braid for the Nology wire and lets see if this changes things.     It may take some time, to see any change.  I did it several times and there wasn't much difference. Then I did put boot back. Breakdown started at 200 psi. Then I did put quite lot of silicon grease between boot and plug ground. That did help at least until 250 psi.

Originally posted by geek I assume this was all with the NGK plug and to be clear then, the grease got you to where you were without the boot.  This is very similar results to mine.

Resistor NGK-plug. It started to breakdown at 200 psi without boot, but not at every 500 spark sequence (I could set the number of pulses).  Then I did connect the boot and breakdown glow was there all the time betwwn boot and plug ground. With grease I did went to 250 psi and it didn't breakdown. I did rotate it and I didn't see anything. At the beginning I did have to fix and increase grease-isulation couple of times. It seems that grease will help but it is difficult install grease without air bubbles and tightly to plug insulation. Probably silicone glue would be better.




Edited by shmot - 06 November 2009 at 5:43am

... Well,  now you need some custom made plugs with tall insulators, with more ribs.

Edited by Roland Tamaccio - 06 November 2009 at 8:45am

Originally posted by geek I figured some of the strange spelling and terms are just the difference in country.  It's not a big deal.  I understand your posts.

Probably my spelling is much better after all of these problems are solved This is nice way to parctise it. Sorry of that...

Originally posted by geek Now that's using the grease! Maybe you could mold your own boots?    Is the boots your using long enough that the connector could be placed deeper inside so the boot would extend to the base of the plug?  Or, snip off some silicone tube and slide it over the plug before putting the boot on?

I think problem is small airgap between plug insulation and boot. Breakdown voltage for air is 4.7 kV/ 1mm (0.039") and for insulation materials >20 kV/ 1mm (0.039"). Probably airgap is so small that there isn't "room" for large current flow (look at the arc with or without boot). Distance from plug tip to bottom is 1" but air breakdown voltage to 0.039" doesn't stay constant if distance or pressure are increased. What I did found out from one handbook that for 1" airgap breakdown voltage is 68 kV. That can't be true or coil output voltage is much higher than 100 x coil primary voltage 520 V.
 
One possibility is to glue boots to plugs to prevent airgap or build some barrell over plug insulation and boot and fill it with mineral oil.   


Edited by shmot - 06 November 2009 at 10:09am

You also look at it as a gain problem.   I am not sure this is right.   I pulled a few text books but nothing really dove into the details. 

Looking at the TFX plots, it's hard to say where the ignition took place.  Maybe this is a blown nitro motor.  Maybe they are showing it as the -40 BTDC start point. 

Do you people in Finland rake your leaves?   What a mess this time of year. 


The equations look right but I wonder if this holds true for a two stage pump, i.e. turbo charged?  

Dang, snow already.

I consider my bike a rolling test lab. Smile

Originally posted by shmot Tcompressed / Tinlet = (Pcompressed / Pinlet)(1 - 1/Y) where: Pcompressed / Pinlet is the pressure ratio, Y ("gamma") is the ratio of specific heats of the mixture,    Y=1.4 for typical air fuel mixtures, Txxx are before and after absolute temperatures.

Let's start by checking some of what you presented against my bike.
Let's assume I am using some typical air fuel ratio and use 1.4.
I do use gasoline.

Looking at my last recorded pass:

Ambient Temp:  52 F  =  284 K
Intake Pressure:  101.4 KPa

There really is no steady state condition as the bike makes it's way
down the track.  So I will use the final temperature and pressures.

Outlet Temperature: 284 F  =  413 K
Outlet Pressure:  287.5 KPa

413 K / 284 K = 1.45

287.5 KPa / 101.4 KPa = 2.835
1-1.4^-1 = 0.2857
2.835^0.2857 = 1.347

So, about a 7% error.  Not too bad considering we do not really know what
gamma is.  At least for the first stage (the turbocharger) the numbers
hold true.  We don't really know the source of the error, so let's not
adjust anything (i.e. back calc a new gamma).



The bike will make about 180 PSIG of cranking pressure with the current setup.
The when the bike is down track, the ignition is set to 28 deg BTDC.  If we
assume this is a linear relashionship and the pressure is 0 at BDC. It's about
1 deg / PSIG so maybe 150 PSIG.

Now comes the million dollar question, from this how can we determine the
pressure once the boost is applied?  We really don't know what the temperature
rose to at the point of ignition.

We can use your handbook numbers but I am not sure that makes sense.  We know
the the first stage has already added energy to the charge.

At first stage compressor efficiency will effect to temperature rise
http://www.not2fast.com/turbo/glossary/turbo_glossary.shtml#compressor_efficiency.

                     (PR^0.283 - 1) * Tambient
            Trise = ---------------------------
                            Ec

            Trise    = increase in temperature
            PR       = pressure ratio
            Tambient = ambient temperature (in an absolute scale, Kelvin or Rankine)
            Ec       = Efficiency of the compressor

Nice calculator for that
http://www.not2fast.com/turbo/glossary/turbo_calc.shtml

With your values

Trise= 413 K - 284 K = 140 K

                ((287.5/101.4)^0.283 - 1) * 284 K
Trise = 140 K = ---------------------------         =98.5/Ec 
                         Ec

=> Ec 0.7 = 70 %

Yours compressor should be 70 % efficient with that mass flow and 2.835 pressure ratio.

Second stage is piston compressor and camshafts have large effect to pressure. 
Also time used to compression (engine rpm) should affect to temperature rise and
that isn't in second stage equations. If we put 11:1 compression ratio, 66 mm stroke
117 mm rod, cam duration 291 and temperature 70 F to this calculator
http:///www.not2fast.com/turbo/compression/cranking_pressure.shtml,
then chamber pressure is 180 psi. Now if we set cam duration to 0 (100 % volumetric efficiency), then
chamber pressure is 304 psi. 

I think 2 - pump series tests is different if you are measuring outlet pressure. 
Air will cool down after compression and pressure will drop. You should very rapidly measure 
pressure inside second compressor cylinder. That pressure should be close to those 
equations.

There is still something odd in megamanual equations. I will get different results with 
megamanual equations and not2fast calculator. Need to check those. 

Edited by shmot - 09 November 2009 at 3:06am