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YAK- LIST: 94 Octane unleaded avgas
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pfstelwagon(at)earthlink.
Guest

Posted: Tue Feb 10, 2009 5:15 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

The Chinese engines were rated for 70 octane fuel,  that was probably what we call White Gas.  I don't think there was any lead  in it at 70 octane. So the Chinese engines will probably be fine on the unleaded  gas.

  

 Frank  N23021

   [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Tue Feb 10, 2009 5:25 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

Concur, how about if we test that premise on yours first?  



Mark 

N50YK



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mark.bitterlich(at)navy.m
Guest

Posted: Tue Feb 10, 2009 6:03 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

Sorry Frank, I was just messing with you.  



Here's the deal.  It does not matter if the gas is white, green, or yellow.. (Well.. Green would sure be nice, .. Purple even  better) but anyway... If it does not have any lead in it, then you need to have hardened valve seats.  Period.  The question then becomes, "do any of our engines already have hardened valve seats"? I'm not really sure.. Does anyone know FOR SURE?  I have looked at them, and they look stock to me.  It is also highly unlikely that they would have them, since they were never introduced into any car engine until they were absolutely necessary to have.  



As I said, all you have to do is to run a little bit of leaded fuel every once in awhile to prevent valve erosion.  You can run pure unleaded for quite awhile too as long as you just run leaded fuel every couple of tanks fills and even then it does not have to be "pure" unleaded... Even a 50/50 mix every once in awhile will work.  



But if you run unleaded fuel continuously in an engine with valve seats that are not hardened, you WILL pound those valves right into their seats.  It does not happen overnight.  It takes time.  But it WILL happen.  Everyone tends to think that the lead in fuel was there only for the octane.  This is partially correct, but it was also there for the valves.  



If any of our engines were indeed designed to run on unleaded fuel, they WILL have hardened seats.  So if someone comes up and says that our engines have hardened valve seats, then there are no worries at all.  By the way, these kind of seats can be retrofitted, so it is not like it is a MAJOR big deal. 



Respectfully, this is not an opinion, this is hard cold physics.  



Mark Bitterlich

N50YK



P.s.  If you want more, read below.  This was written about car engines.... But fuel is fuel, and a valve is a valve.  



How did Valve Seat Recession come about? 



Most people realize that back in the days when we ran leaded fuel in our cars, the lead was great at improving combustion and raising octane. This high-octane fuel is what enabled cars to run much higher compression ratios than cars do today. Another property of that fuel that contributed to the health of the older motors was that the lead oxides that were formed during combustion would settle on the valve seats and act as a cushion protecting the seats from erosion. 



Once people realized the harmful effects of lead on the environment however, pressure caused leaded fuel to be phased out. In response to this, car manufacturers lowered compression ratios and started using hardened valve seats that did not require the lubricating properties of lead. 



That's fine for newer cars, but those that owned cars that were originally designed to run on leaded fuel (i.e. cars that used non-hardened exhaust valve seats) needed to take certain precautions to prevent valve seat recession. Car enthusiasts soon learned that unleaded fuel required the use of hardened valve seats on the exhaust valves, and that without some precautions, their cars would exhibit valve seat recession. 



Exactly what is Valve Seat Recession and what causes it? 



Simply, VSR is the erosion of the valve seat causing the valve to slowly sink deeper and deeper into its seat. Without the protective lead coating or hardened inserts on the exhaust valve seats, the intense heat (650°C or 1200°F) and the constant hammering effect of the valves opening and closing causes iron deposits from the valve seat to become micro-welded to the valve edge as it closes. When the valve opens again, some small amount of metal from the seat will be ripped from that seat. Left alone, this continual tearing away of metal particles will result in the exhaust valve digging a deeper and deeper hole for itself into the head. Eventually, the engine will break down and require to be overhauled. VSR is only a problem for the exhaust valve seats since they run at much higher temperatures than the intake valves. 



If my heads exhibit VSR how fast can my valve seats erode if I ignore the issue? 



Without hardened seats or some lubricant in the fuel, they can erode quickly under the right conditions! The two worst contributors to this problem are prolonged high engine speeds, and high exhaust gas temperatures. If you baby your engine, it's likely that you may never experience the problem. To give you a better idea of just how fast this can occur, independent testing has shown that for some types of engines, exhaust valve seats can recede by as much as 0.020" when run continuously under both high load and high RPMs for 48 hours. 

--

ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Tue Feb 10, 2009 6:47 pm Post subject: Re: YAK- LIST: 94 Octane unleaded avgas

 	  Quote: 	
		  Without hardened seats or some lubricant in the fuel, they can erode quickly under the right conditions! The two worst contributors to this problem are prolonged high engine speeds, and high exhaust gas temperatures. 	




Mark....this is from the article you posted....isn't this how we run aircraft engines????

n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Wed Feb 11, 2009 5:47 am Post subject: Re: YAK- LIST: 94 Octane unleaded avgas

Mark,



Who is the author of the article you quoted and from what publication?



Thanks,

_________________
Milt

mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 10:29 am Post subject: YAK- LIST: 94 Octane unleaded avgas

I would say so, yes.  The lower the compression ratio, and the lower

the

horsepower, on a given engine design, the slower this effect occurs.

Comparing a Housai to say an M-14PF, the M-14PF is going to see it

happen a

heck of a lot sooner. 



Mark

 



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dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 11, 2009 10:35 am Post subject: YAK- LIST: 94 Octane unleaded avgas

Why do you say that Mark?  The compression ratio on the  PF is the same as the P engine.  The difference is the supercharger gearing  which ='s boost at WOT.  IE: approx 1000 mm vs. 880 mm at sea  level for the stock P at WOT.

 Dennis

  

 [quote]   ---

mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 11:10 am Post subject: YAK- LIST: 94 Octane unleaded avgas

First, I totally concur with the factual data you posted.  Indeed, the

blower speed is really the only difference between the two, unless you

really want to nitpick between first and second generation cylinder

heads, which we will ignore here.    



To answer your question... Basically it's a heat thing.  



Take a given engine design.... An ideal comparison would indeed be the

M-14 series of engine, where you have the 360 horsepower "P" model and

the 400 horsepower "PF" model, but physically speaking they are both

identical (as you pointed out...blower speed aside).  Anytime you make

more horsepower in this given engine, you also make more heat. A 4 cycle

engine is basically just one big heat engine. So the main reason it is

more of a factor in say the PF model versus the P model is that the

combustion temperature is indeed higher.  Of course I am talking about

when the engine is actually developing peak horsepower and not at idle,

or some partial midrange power setting. The whole issue surrounding

valve recession is based on the heat of the valve itself.  The hotter

the valve, the quicker it is going to happen.  



Mark

--

mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 11:21 am Post subject: YAK- LIST: 94 Octane unleaded avgas

http://www.intense-racing.com/VSR/VSR.html



Additional articles:



http://www.geocities.com/ste_griff_2000/Runningonunleaded.htm



http://www.redlineoil.com/whitePaper/12.pdf



http://www.aa1car.com/library/ar1192.htm



http://www.aa1car.com/library/ar993.htm



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dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 11, 2009 11:45 am Post subject: YAK- LIST: 94 Octane unleaded avgas

Ok.  I agree with the heat thing.  What I wasn't  agreeing with was the statement about compression ratio between the  P (Housai too) and the PF with the PF being much higher thus  causing "it to happen a heck of a lot sooner".  In fact, there is only  1/10 of a point difference between the M14 (6.3 to 1) and the Housai  compression ratios with the Housai being 1/10's of a point less at 6.2 to  1.

  

 With regards to the Housai engine developing 285 HP vs the  M14P developing 360 HP at WOT, (as you point out, more heat) if one looks at the  rpm where the Housai's 285 HP is developed (WOT) and then look at the M14P  power chart at the same RPM, (2400 RPM comes to mind or 82%), the M14P chart  says the engine develops 290 HP at 2400 RPM.  Not much horsepower  difference. 

 Dennis

  

 [quote]   ---

mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 11:46 am Post subject: YAK- LIST: 94 Octane unleaded avgas

I forgot to mention something.  



It is a fact that all you need to do is to increase the blower speed to

make a P model M-14 into a PF model and gain 40 horsepower in the

process.  However, it is also a fact that the folks that sell the

package to do this do not recommend that you do it to an M-14P engine

running first generation cylinders.  Why is that?  Because the original

M-14 cylinders heat fins were redesigned to dissipate more heat, hence

the difference between first and second generation cylinders.  When you

increase the blower speed, you put more air and more fuel into the

engine, which means a higher combustion temp., which means more power,

and also more excess heat to get rid of, which is why running first

generation cylinders is not recommended when converting a P model M-14

into a PF model. 



Mark Bitterlich

--

dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 11, 2009 12:00 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

Not according to Termikas, one of the top engine overhauling  companies.

 Dennis

  

 [quote]   ---

mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 12:02 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

I see what you are saying Dennis and "how you got there".  My message

was poorly written.  There was meant to be two different sentences with

two different meanings. What happened was the first sentence combined

with the second, ended up with a meaning I did not intend to imply.  



Better said then:



1.  The lower the compression ratio, and/OR the lower the horsepower, on

a given engine design, the slower this effect

	occurs.



2. 	Comparing a Housai to say an M-14PF, the M-14PF is going to see

it happen a heck of a lot sooner due to combustion heat temperature

differences. 

	

	

I never meant to imply any difference in compression ratios, only a

difference in developed horsepower. 



Thanks for pointing that out... I "get it now" !!!  



Mark

 



 



--

dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 11, 2009 12:07 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

Now we're singing from the same music sheet!   ))

 Dennis

 [quote]   ---

mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 12:39 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

What point that I made are you saying Termikas disagrees with Dennis?  



1. That a 400 horsepower engine develops more heat in the cylinder than

a 360 horsepower engine? 



2. That the second generation cylinders were redesigned to increase heat

dissipation?  



3. Or that it is not recommended to convert a P model to a PF thus

increasing cylinder temperatures further on a first generation cylinder

that the Russians already decided could be improved, and redesigned to

increase?    



Assuming #3: It IS true according to Vladimir Yastremski, Russian

trained Master Mechanic, Sergei Boriak, Russian trained Sukhoi Test

Pilot, and a gent who's name I honestly can not remember from Richard

Goode's shop over in England that does these engine conversions.  



Notice I did not say: "It is impossible to convert first generation

M-14P engines to 400 HP PF models."  What I said was it was not

"RECOMMENDED".  The only difference between the first and second

generation cylinders is increased heat dissipation.  Spinning the blower

harder increases combustion chamber temperature, and increases the

amount of heat that the cylinder has to get rid of. If you want to use a

cylinder design that knowingly dissipates less heat than another when

making a modification that generates more cylinder heat, then be my

guest Dennis. It will run just fine, but will be easier to damage by

over-temping.



This breaks down into a "he said, they said" kind of discussion.  You

say Termikus said it is ok to do this.  My sources and my own logic

dictate otherwise.  To each their own, but remember that Termikus is in

business to make a profit.  



Mark Bitterlich

  



 

  



--

dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 11, 2009 12:47 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

The point I was making was that Termikas does the upgrade to  400 HP to Series 1 engines and Series 1 cylinders.  In fact, I  delivered one on a Yak 52 TD last summer.  It had Series 1  cylinders.

 Dennis

 [quote]   ---

dsavarese0812(at)bellsout
Guest

Posted: Wed Feb 11, 2009 12:48 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

Not to sound argumentative Mark, but who/what  company said it was not recommended?

 Dennis

  

 [quote]   ---

mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 1:03 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

I believe you. 



Mark



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mark.bitterlich(at)navy.m
Guest

Posted: Wed Feb 11, 2009 1:07 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

Not to sound sarcastic Dennis, but I already answered that question.  

Mark



  



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p.goswick(at)cox.net
Guest

Posted: Wed Feb 11, 2009 1:07 pm Post subject: YAK- LIST: 94 Octane unleaded avgas

How can you  identify series 1 cylinders

 Phil

  

   [quote][b]

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