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Old 10-23-2006, 12:43 PM   #16
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Quote:
Originally Posted by MugenDrew
The motec deal is that system open or closed loop?
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What I got is an Motec M48 Pro and could work in open and closed loop modes, quite puzzling and overhelming at first moments, but I'm just digesting all the you can do with the ECU and the info can throw it.
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Old 10-23-2006, 08:32 PM   #17
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I like running #7 plugs unless ambient temps go much below 60F. In high humidity I don't think a #8 would be all that beneficial to control timing and have the engine maintain it's performance. I like to run the #7 plug and just take 0.1mm shim out in real high humidity.

Low altitude AND high humidity/temp (FL) is real fun for a guy who is from NY and normally races in Canada. The altitude at sea level is the predominating factor in my decision making. More air= adding a shim to prevent detonation and keeping the #7 plug to keep the flame lit on the low end with the humidity. There are really three facors to consider in this condition...... altitude= add a shim, humidity= remove a shim, temp= lean the mixture. The best thing I have come up with during a lot of hot laps is to add a shim while keeping the #7 plug. My needles are usually with 1/4 turn based on temps.

ask some guys that travel up north to run what they do..... probably the opposite of what I do as far as shimming.
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Old 10-23-2006, 09:20 PM   #18
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I'll add a few factoids that I have had experience with...

Closest clearance (piston to head) on a .12 engine is .4mm
Maximum effective clearance for .12 engine is .8mm

Closest clearance for .21-.32 engine .5-.55mm
Maximum effective clearance for .21-.32 engine 1.1-1.3mm

Lowering head clearance WILL raise combustion pressure and combustion temperature respectively. (Thermal efficiency may go up but negligibly)

Raising Nitro % will also have similar effect (more pressure and more heat)

Raising Nitro % requires more alcohol to keep similar burn ratios (this explains why we need to set carb richer when changine to more nitro) (Also this explains why miliage suffers when going to higher nitro)

Raising ex port will cause higher rpm effective tq peak

Widening ex port will have similar effect without losses on midrange

Water vapor DOES NOT convert itself to hydrogen and oxygen in the combustion process. (A. if it did there would be little use for fuel cell engines) (B. the combustion temp. is far too low in our engines for this to even begin to take place) (C. Water vapor in internal combustion engines only turns to steam during combustion)

The Combustion temps of our engines are much lower than that of gasoline or petrol engines. (Ex temps of gasoline engines in the 1200 deg range and Glow engines in the 400-500 deg range)

Hotter air = leaner Colder air = richer

More humidity = leaner Less humidity = richer (this is due to water vapor displacing useable fuel molecules in the intake charge requiring less fuel due to less oxygen)

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Old 10-24-2006, 05:52 AM   #19
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mx... seems like we are on the same page

I did not convert your metric units of clearance to what I measure in..... thousandths. I do know that every 0.1mm is .004", so your .55mm (0.022") is a bit lower than I shoot for on my standard set-up of 0.028". My 0.028" standard falls right in the middle of your band at 0.70mm. In FL I may add 0.1mm shim and occasionally I may remove one.

We are very close on .12 engines as well. Again, I fall right in the middle of your band at 0.022"- 0.024" (about 0.6mm) on my starting point.

I agree with all your other tuning points on humidity and temps as well. Usually there is one over-riding factor that makes the determination on how to best tune the engine at a given set of conditions. The determining factor could be different with each new set of variables, but good to see someone who is on the same page.
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Old 10-24-2006, 06:49 AM   #20
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Quote:
Originally Posted by cdelong
mx... seems like we are on the same page

I did not convert your metric units of clearance to what I measure in..... thousandths. I do know that every 0.1mm is .004", so your .55mm (0.022") is a bit lower than I shoot for on my standard set-up of 0.028". My 0.028" standard falls right in the middle of your band at 0.70mm. In FL I may add 0.1mm shim and occasionally I may remove one.

We are very close on .12 engines as well. Again, I fall right in the middle of your band at 0.022"- 0.024" (about 0.6mm) on my starting point.

I agree with all your other tuning points on humidity and temps as well. Usually there is one over-riding factor that makes the determination on how to best tune the engine at a given set of conditions. The determining factor could be different with each new set of variables, but good to see someone who is on the same page.
Yes, my lowest values are what I consider to be the absolute minimum clearance before the piston makes contact with the head. This value may be runnable on some engines and not runnable on others depending on combustion chamber dome volumes. Moreso these values are just a guide on what is a mechanical possibility, before you have angry parts.

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Old 10-24-2006, 07:07 AM   #21
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Nitro 2 to 1. Methanol 6.45 to 1. Fuel to air ratio is what your speaking of in regards to burn ratio or are you talking about the speed the flame kernel reaches the cylinder wall? The temps you listed are these from an E.G.T. located in the header? I'm curious, based on known temps to reform Castor into large molecules and that the synthetics generally burn off some where above 800 degrees. we should not see the deposits on the piston if the temps are this low. Nice Dyno! Good conversation fellas...
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Old 10-28-2006, 10:01 AM   #22
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Since I didn't find OS TZ thread I will post here regarding head clearance in this engine eheh
I own a TZ12-T3 with T-1040 52 pipe and I need more power to beat a Sirio Evo3
I have thought change to a fuel that contains 30% of nitro, in the moment I'm using Byron 20%, but I had seen some people talking that I must change the Head Clearance, and I would like to know how many shims I should add
I've got excellent settings, good temp and my glow plug lasts hours.. I really want to keep this while with a 30% nitro fuel

Any extra advice is welcome

thanks a lot
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Old 10-29-2006, 10:24 AM   #23
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Hi

Firstly addingmore nitro only slightly increases the power and has the effect of lowering the revs as it burns slower. I would not go higher than 25%

For 25% Notro you need a head clarance of around 0.4-0.5mm. Measure the head clearance by inserting a length of solder into the glow plug hole and turning the piston over so it crimps the solder on the head. Measire the flat spot.
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Old 10-29-2006, 11:24 AM   #24
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Quote:
Originally Posted by ziggy12345
Hi

For 25% Notro you need a head clarance of around 0.4-0.5mm. Measure the head clearance by inserting a length of solder into the glow plug hole and turning the piston over so it crimps the solder on the head. Measire the flat spot.
Maybe for a .12cc engine 0.4- 0.5mm would be OK, but for a .21 you need about 0.7mm of clearance. 0.4- 0.5mm is far to little here in the states for a .21 and beyond most anyones margin of comfort for clearance at RPM issues. Remember.... the rod is stretching under racing conditions.
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Old 10-29-2006, 12:09 PM   #25
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Quote:
Originally Posted by cdelong
Maybe for a .12cc engine 0.4- 0.5mm would be OK, but for a .21 you need about 0.7mm of clearance. 0.4- 0.5mm is far to little here in the states for a .21 and beyond most anyones margin of comfort for clearance at RPM issues. Remember.... the rod is stretching under racing conditions.
.. we are talking about 12 engines..
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Old 10-29-2006, 05:35 PM   #26
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Quote:
Originally Posted by cdelong
rule of thumb I've always gone by is:

0.026"- 0.028" on a .21 running 30% and a #7 plug

0.020"- 0.022" on a .12 running 30% and a #6 plug

I check with modeling clay just as I do when checking valve clearance on my real car stuff

*note- I'm on the east coast and generally conditions are 400- 1000ft above sea level. Only once or twice a year do I need to re-shim for a particular set of conditions.

This is the most straight forward answer.
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