ESE's works engine tuner

[dinamik2t]

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Got to this http://www.datasheetcatalog.org/data...cs/mXyzryy.pdf and this http://www.freescale.com/files/micro...ote/AN4006.pdf , which are very informative for a beginner.
About the spark duration on CDI's.. If two capacitors were to be discharged together, the second with a slight delay? To your knowlegde is this an already solved 'problem'?

p.s. TZ excuse me for intruding, eh..

[TZ350]

http://www.freescale.com/files/micro...ote/AN4006.pdf

About the spark duration on CDI's.. If two capacitors were to be discharged together, the second with a slight delay?

The freescale schematic is very interesting.

How does the two capacitor thing work extending the spark duration??, I am not sure but I don't think you would have to delay the discharge of the second capacitor.

This is what I think I understand, but would be interested in hearing more about it.

Its the flux change of the magnetic field in the coil as the CDI discharges into the coils primary windings that builds up the spark voltage but once the spark jumps the gap its duration is the length of time it takes to discharge the capacitors and the magnetic field to collapse.

There can only be spark voltage while the magnetic field is in a state of flux, either building up or falling down it doesn't matter, there just has to be change going on in the coils magnetic field for energy to be present at the spark plug gap.

The old 6-12V battery coils Flux was to slow building up (lack of driving voltage) to make a spark but when the points opened the change in Flux was fast enough for the collapsing (Fluxing) magnetic field to make 200 to 400V in the primary and that induced a high enough voltage in the secondary for a spark at the plug.

CDI's hit the coil hard with 200 to 400V driving a lot of current through the primary side of the coil and the magnetic field builds up so fast it induces a massive voltage in the secondary and the resultant spark and energy keeps flowing across the plug gap until the field has collapsed again.

The strength of a magnetic field is proportional to the current in the coil and its the CDI's voltage that drives the current. But the capacitors voltage fades away as the current is drained.

So maybe the current capacity of more or bigger capacitors could actually allow the CDI's voltage to drive the magnetic field even higher after the spark has jumped the gap. Unlike the poor old 6-12V battery coil where when the points opened and the current stopped there was only one way for the magnetic field to go, and that was down.

I would be interested in knowing more about this.

[Muciek]

For a good CDI spark you need to match the capacitor in the CDI module and coil. Here's my DC CDI https://www.youtube.com/watch?v=zNcA0oYLj1s using 12V source (battery was dead , so power was from stator) output 360V. I have also bulid 400v ( https://www.youtube.com/watch?v=OhG4M2WEM9w ) and 600v version but there was problem with cooling and coils were dying like flies. That one one video need about max 2A it's very high efficiency (over 90%) and compact it looks like a cigarette box.

[dinamik2t]

TZ, I was thinking of sending a second ignition pulse, say at about 1/2nd of the duration of the first, from a second capacitor.
Would it be possible coil wise though, as you say?

[TZ350]

I was thinking of sending a second ignition pulse, say at about 1/2nd of the duration of the first, from a second capacitor. Would it be possible coil wise though, as you say?

My understanding is limited to thinking in terms of coil flux, and nothing happening at the plug gap unless the magnetic field inside the coil is in a state of flux.

Are you looking for two spark events? its possible but you have to wait until the first spark is extinguished, ie the magnetic field has collapsed in which case the crank may have moved well beyond TDC.

You need to look at the time lines, I would be interested in how long a spark lasts and how many degrees of crank rotation that represents.

More research is required ... Google is our friend. try "spark burn time"

http://www.globaldenso.com/en/produc...ark/index.html

http://spdispark.com/pages/frequentl...spark-duration

http://www.auroraelectronics.com/ign...basics_to_high performance.htm

Multi spark only effective at low RPM http://www.dtec.net.au/Multi Spark Ignition.htm

http://www.daytona-twintec.com/tech_ignition.html

Testing Plug Wires http://www.mr2.com/TEXT/DavidKucharczyk/ignition.html

http://www.acuravigorclub.com/Timely...mely1104-2.htm

http://forums.turbobricks.com/archiv...p/t-50682.html

http://www.not2fast.com/ignition/cap-dis-ignit-cdi.pdf

Plasma Spark ..... http://spdispark.com/pages/about-spdi-spark

Plasma ignition, now that looks interesting, by the look of it, its a real mans ignition that can weld 1/2" plate.

[TZ350]

Why???? ....... your making good power, why resurrect the old plenum idea again.

This is a back to back test with a 24mm carb vis a 30, the 30 gave better over rev.



Although I have been able to get 31 rwhp (35ish at the crank) it was hard work and finniky. So I am starting to feel hampered by the 24mm carb restriction.

In the past the plenum made about as much power as a carb could and I don't really expect things to be much different this time.

But now that I have an EFI kit to try I can run the plenum again without the fuel drop out problems of before and maybe this time I can get 31-32 rwhp consistently. One of the things I would like to try is an air chiller inside the plenum so the motor ingests really cold air.

[TZ350]

Posted because someone was asking me about it ....

Page 500 .....
No need to have a peaky engine. Here are Two Very useful Tools. EngMod2T a 2-Stroke simulation package and a handy (and cheep) Porting Calculator from:- http://www.porting-programs.com/ which is based on Blairs work.

Buckets post has links to detailed pictures of how we built the early engine.

Yep, hand drills are good, you can do some quite good work with basic hand tools.

We got most of our improvement by opening up the rear transfer ports. Nothing fancy, a 13mm drill or ball end long series milling cutter will do the trick. These two posts are worth a look to see how rough you can be and still get a good result.

Got me a nice new 10mm ball end milling cutter today. Its great for digging holes and leaves a nice radius on the back of the newly excavated transfer ducts

STA's for the triple port show that with a bit of work reasonable numbers are possible from the old Suzuki cylinder.



STA's for a single port Suzuki GP125 cylinder.

Avs bike is a single port with the Exhaust opening 80 degrees ATDC 72% wide, Transfers 114 ATDC and Inlet opening 145 BTDC and closing 80 ATDC. Its a very easy bike to ride with a smooth flat torque curve. The carb is a taper bored 24mm OKO and is 30mm at the engine end and the rotary valve port window area has an effective diameter of 36mm.

If we were doing it again we would probably pay more attention to widening the rear "B" transfers and opening them a little later, like in the EngMod2T data sheets above.

Remember to get those transfers low and wide to maximize specific blow down time area of the exhaust port.

[Frits Overmars]

One of the things I would like to try is an air chiller inside the plenum so the motor ingests really cold air.

A fridge in that plenum won't do your total mass and your cornering clearance any good, TeeZee. And anything smaller will probably not have sufficient cooling capacity to make a difference. We're talking about 1300 liters of air per minute....

[TZ350]

.... probably not have sufficient cooling capacity to make a difference. We're talking about 1300 liters of air per minute....

I have a dinky little alluminium radiator that I had thought of running ice water through. The radiator could sit inside the plenum with a fan circulating plenum air through it while the radiator is being chilled by the ice water. Another option is an air/air inter cooler with dry ice or in a bath of ice water or an air/water intercooler with ice water pumped through it. The whole thing was to hinge around the latent heat of fusion of ice.

Yes I will have to run the numbers to see what the thermal requirements would be.

[Yow Ling]

I have a dinky little alluminium radiator that I had thought of running ice water through. The radiator could sit inside the plenum with a fan circulating plenum air through it while the radiator is being chilled by the ice water. Another option is an air/air inter cooler with dry ice or in a bath of ice water or an air/water intercooler with ice water pumped through it. The whole thing was to hinge around the latent heat of fusion of ice.

Yes I will have to run the numbers to see what the thermal requirements would be.

If you go down that route you may as well put the 36mm carb on it as it could be argued that you would be limiting yourself to 100cc.

[husaberg]

I have a dinky little alluminium radiator that I had thought of running ice water through. The radiator could sit inside the plenum with a fan circulating plenum air through it while the radiator is being chilled by the ice water. Another option is an air/air inter cooler with dry ice or in a bath of ice water or an air/water intercooler with ice water pumped through it. The whole thing was to hinge around the latent heat of fusion of ice.

Yes I will have to run the numbers to see what the thermal requirements would be.

At the risk of sounding like an industry insider, i are just not getting it Rob.

The Vehicles that i am aware of that run inter-cooling pressurize the intake, Thereby greatly heating the charge, prior to induction. I can't see how you could achieve a large drop in intake temp, with ambilent air temp without a lot of restriction or over complication.
Beer i mind, I am often wrong though. just mussing.

[chrisc]

Posted because someone was asking me about it ....

Avs bike is a single port with the Exhaust opening 80 degrees ATDC 72% wide, Transfers 114 ATDC and Inlet opening 145 BTDC and closing 80 ATDC. Its a very easy bike to ride with a smooth flat torque curve. The carb is a taper bored 24mm OKO and is 30mm at the engine end and the rotary valve port window area has an effective diameter of 36mm.

If we were doing it again we would probably pay more attention to widening the rear "B" transfers and opening them a little later, like in the EngMod2T data sheets above.

Remember to get those transfers low and wide to maximize specific blow down time area of the exhaust port.

Nice one Rob! I was looking through old posts and I came up with a new forum signature, thanks wob! you got a laugh out of me.

Time to hit the engineering shop for some new tools

[TZ350]

OK I looked at some numbers.

Air 1300 L/min

Race duration 15 min

15 * 1300 L = 19500 L of air or lets say 20 cubic meters of air for a race.

At 300K the specific heat of air is nominally 1 kJ/kg K

So at 300 Kelvin (or 27 deg C) it takes 1 kJ of energy to heat (or cool) 1 kg of air 1 deg K (or C as C's are the same size as K's, its just that the K scale starts at absolute zero. The point where all thermal activity ceases and the C scale starts at the freezing point of water).

Now I want to cool the air by 25 degrees so its only 2 degrees C going into the engine. That means I have to have 25 times 1 kJ of energy per kg of air or 25 kJ per kg of air to drop the air temperature 25 deg C.

Now dry air is nominally 1.2 kg a cubic meter at standard temperature and pressure.

So we have 20 m3 of air times 1.2 kg or 24 kg of air consumed in a race.

24 kg of air times 25 kJ = 600 kJ of cooling energy (energy absorption if you like) required for a race.

Heat of fusion of ice is nominally 334 kJ/kg.

It looks like 600 kJ is required and I can get that from 2 kg of ice or two and a bit liters of ice water.

So long as I have not made any real mistakes and I am happy with the weight penalty then it looks possible and the result depends on the effectiveness of the radiator and fan inside the plenum.

[husaberg]

O

Now dry air is nominally 1.2 kg a cubic meter at standard temperature and pressure.

So we have 20 M3 of air times 1.2 kg or 24 kg of air consumed in a race.

24 kg of air times 25 kJ = 600 kJ of cooling energy (energy absorption if you like) required for a race.

Heat of fusion of ice is nominally 334 kJ/kg.

OK but those 24 liters of air what is the contact time the air would have with you medium?

Anyway my all time favourite dubious use of cooling intakes.

Peter Brock won pole position after the top 10 run-off but he had to face the stewards on Saturday afternoon. His team was charged with using an on-board fire-extinguishing system to direct super-cooled halon gas over the intercooler, thus boosting power for qualifying. The stewards found the charge unproven, but the Entrants Association imposed a $5000 fine on Brock for a moral infringement of the rules.

[TZ350]

Brock .... good thinking, deserved a medal.

OK but those 24 liters of air what is the contact time the air would have with you medium?

Unsure, but the plenum at 2.5L is 10 times the size of the engine and with a fan inside the plenum circulating the plenum air and blowing it through the radiator I expect that a lot of the air will get several passes through the radiator (heat absorber) before being inducted by the engine.

Anyway, whatever happens the air will be cooler and denser than it would have been.