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Ring Location

 
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Noob
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PostPosted: Thu Nov 10, 2011 3:06 am    Post subject: Ring Location Reply with quote

I am working with an old type1 bug engine. We are making a drag engine. The pistons are free. The ring grooves are very low on the pistons. If we have our machine shop make a new groove higher up on the piston, closer to the top, thus eliminating some of the squish area, will that increase horsepower? I know modern engines due this primarily for emissions, but I am curious what it would mean to horsepower.
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af2
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PostPosted: Thu Nov 10, 2011 7:43 pm    Post subject: Reply with quote

The rings are low because it is air cooled. Do not try and reinvent the wheel on that one, I did and in short time loss'ed a piston.

The squish you seem to be worried about is non existent with the rings and you should be concerned with the head to piston. .010" per inch of bore is a good starting point and will keep you out of trouble using steel rods and N/A. If you desire less squish you need to go until you have no carbon on the piston top then add .010"

Are the heads dual port? If not you need to find some. If you spin it 7000 or more you better get the engine warm/ hot before the burnout to allow for expansion. If the cam you use requires .012" you need to set at .002" cold and may need to go .000" to get what the grinder has in mind.
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PostPosted: Thu Nov 10, 2011 7:50 pm    Post subject: Reply with quote

Thanks for the reply. We've optimized pretty much everything. We're down to splitting hairs, and this is the only area we have not played with.

Lash is set to 0 on this motor (cold)

The heads are kept cool using a BIG electric fan and we have even played around with a water mister believe it or not.

Head temps are very cool. 300 under the spark plug, which is lower than most others.

What caused you to lose a piston moving the ring higher?

I have some high temp coated rings, so I think that won't be an issue. We machine them down to about 1mm and use a spacer to fit them in the stock grooves today. They are similar to air cooled dirt bike rings.

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PostPosted: Thu Nov 10, 2011 8:42 pm    Post subject: Reply with quote

Noob wrote:


What caused you to lose a piston moving the ring higher?

I have some high temp coated rings, so I think that won't be an issue. We machine them down to about 1mm and use a spacer to fit them in the stock grooves today.


What I have found is the spacer is not a good Heat sink and keeps the heat in the piston.

When I moved the ring higher in the piston it killed the ability to lose heat into the wall because the wall must have been pretty close to ring temperature.


I have a hard time putting my thoughts into type so bear with me.

I have a hard time with the coated rings dispersing heat.
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PostPosted: Thu Nov 10, 2011 8:46 pm    Post subject: Reply with quote

Hmmmm. Interesting.

Try Sunoco GT250 E10 race gas. Smile Has quite the cooling effect on the charge. Smile (plus it contains some O2 so you get a little more HP.

So, if i was able to get it to work, theoretically, is it worth any HP?

I think eliminating the spacers with a smaller groove to run the size rings I want to begin with might help with what you are describing.

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PostPosted: Thu Nov 10, 2011 8:47 pm    Post subject: Reply with quote

Just remember that heat goes from hot to cold.
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PostPosted: Thu Nov 10, 2011 9:05 pm    Post subject: Reply with quote

Noob wrote:
Hmmmm. Interesting.

Try Sunoco GT250 E10 race gas. Smile Has quite the cooling effect on the charge. Smile (plus it contains some O2 so you get a little more HP.


Combustion temperature has no merit? The charge and tune are pretty important?

If you are telling me that GT250 cools the combustion temp I give.
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PostPosted: Thu Nov 10, 2011 9:41 pm    Post subject: Reply with quote

If you want to maximize your design look to what Buell and Harley are doing with their new motor designs. The air cooled VW motor is what Dr. Porsche finalized way back in 1936 so it has endured a lot.

You have to keep in mind that the combustion point of aluminum is only 150 degrees below the combustion temp of gasoline. Build too much combustion chamber heat (or get into detonation) and things can get ugly very quickly. This heat build issue up is why the heads and block are machined from magnesium and not aluminum. Transferring that heat out of the chamber and out of the piston is the reason the cylinders are horizontally opposed to get lots of splash lubrication on the cam and under the pistons. It is also why Dr. Porsche abandoned his first idea of making the engine a two cycle super changed two cylinder motor (with the first two large bore cylinders supercharging the last two smaller bored cylinders).

The oil temp is why the cooler is more important than the head fins and blocks the air flow to one side just to get the maximum cooling air on to the oil cooler tubes. Heat in the chamber is also why VW's readily burn exhaust valves as the transfer of heat is difficult if there is no air over the fins or your cam keeps the valve off the seat before it can transfer the heat to the seat.

I burned so many VW pistons that I got to where I could pull and rebuild a motor in under an hour.

Big Dave
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PostPosted: Thu Nov 10, 2011 9:56 pm    Post subject: Reply with quote

We have not had any temp issues to this point. Will moving the rings change this?

Cooling with our setup has been very good.

Since the Harley's and other AC motorcycled motors have the rings towards the top of the piston, am i to think this is a more effecent way to go?

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PostPosted: Thu Nov 10, 2011 10:04 pm    Post subject: Reply with quote

Comparison:

Harley:


VW:

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PostPosted: Thu Nov 10, 2011 10:42 pm    Post subject: Reply with quote

Noob wrote:
We have not had any temp issues to this point. Will moving the rings change this?


I think it will have nothing to do with cooling and have everything to do with keeping the rings happy.
That is all I say.

Stevo, good luck man, The VW's I have tried to help with had way to many experts tuning and no forgiveness. That is the truth.
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PostPosted: Fri Nov 11, 2011 1:48 pm    Post subject: Reply with quote

Big Dave wrote:


You have to keep in mind that the combustion point of aluminum is only 150 degrees below the combustion temp of gasoline.

Big Dave


I think you meant above otherwise we would all be burning up aluminum components. Wink

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PostPosted: Sat Nov 12, 2011 10:59 am    Post subject: Reply with quote

Paul P wrote:
Big Dave wrote:


You have to keep in mind that the combustion point of aluminum is only 150 degrees below the combustion temp of gasoline.

Big Dave


I think you meant above otherwise we would all be burning up aluminum components. Wink


You are correct. Aluminum catches fire before it melts (which is why it was one of the worlds most expensive metals before we learned how to smelt it beneath a blanket of clay in an electric arc furnace).

The rings and the oil on the underside of the piston are the only two things that cool a piston and keep it from being destroyed. You can alloy different elements and either drop forge the raw casting or machine one out of a forged billet to improve the strength of the part. The forged piston can resist deformation as the crystal grains are aligned like pilars in a building.
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