The Official Work Pictures Thread

[woodworkingboy]

Yes, that's it, Cory. The base ideally needs to be square to the bore. The lathe is a pretty straight forward way to do it. Of course by doing that, it changes the timing numbers with regards to the exhaust, intake, and transfer openings in relation to the piston top dead center and bottom dead center in it's movement. In other words, the intake will be opening at a different point in the piston's travel, for example, and everything else opening and closing at a different point as well, which affects performance. Compression is only one part of the picture.

 

[cory]

And with the oak mandrel that should be possible, true?

 

[mastermind7864]

Good pics, all.

Mastermind, uh, what is a mandrel, what are you doing in those pics? Sorry, I'm not real engiine savvy.

I'll take the liberty of answering. The mandrel is turned to fit the cylinder bore. That enables you to chuck the cylinder up in the lathe with centers, and turn down the base to lower the cylinder over the piston to reduce the volume of space in the combustion chamber to raise compression.

Right on.

But I first cut the squish area to make the combustion chamber smaller......then the base to set the squish clearance.



This was part of the setup for that operation.....

 

[woodworkingboy]

Randy should best answer, he's the expert for sure. Just about lathe operation, since the mandrel is parallel to the bore and follows the lathe centers, the base will be square to it as well when you cut it down. That's how lathes work, basically, cutting parallel or square to the centers, unless you don't want to do that and set them up not to.

 

[cory]

I'm learning a lot here, thank you. Doing that to the squish area makes the metal thinner on top of cylinder, if I am understanding you? Is that an issue at all, like with strength etc? If not then I guess you could say the original cylinder is overbuilt?

 

[mastermind7864]

On the 090 I just removed .032".......really just enough the flatten the area around the combustion chamber. On some engines I take out as much as .080, and have not had any cylinder failures from that.

This 090 is making 200psi now.

 

[woodworkingboy]

Often mss production things tend to be overbuilt to compensate for degrees of differing tolerances during production, including engine parts. When you start cutting away, for sure you have to be careful about removing too much metal and can weaken. On the base as well, you can't cut it down too much for a few reasons, including blowing the cylinder through the top of your saw. Theoretically, I
guess.

 

[cory]

Raising the compression is an understandable thing to increase performance. Does changing those other parameters (the timing numbers) that Jay mentioned also help improve performance or do some of the changes detract from performance, though the net change is positive?

If all the changes help performance, why don't the OM's set the saws up this way from the start? Cuz of emissions? Longevity?

 

[mastermind7864]

As Jay mentioned, these units are mass produced. They are built in "the middle of the road" so to speak......what I do is tweak what the designers built, looking for the gains that they left on the table.

The saws I build are built for work......and will work all day without issues. They do require a closer eye on tune, fuel, oil quality, and mix ratio.

 

[mastermind7864]

I feel like I've derailed this thread a bit.....and apologize.

 

[cory]

The saws I build are built for work......and will work all day without issues. They do require a closer eye on tune, fuel, oil quality, and mix ratio.

That is awesome.

Stock is 50 to 1, what do your saws favor?

Re tuning, is it possible to tweak up a modern ''computer'' saw which has no H or L needles, like a 576, or would the tweaking freak out the 'puter totally?

 

[woodworkingboy]

If I might add... It depends on what you are after, Cory. I have one old 028 where all i did was drop the cylinder to raise compression. It has better torque, but in terms of increasing overall performance including rpms, once again, to what degree you want to, dropping the cylinder often means also doing changes to the ports. Randy would certainly know best, but my guess is that simply lowering the cylinder, can be a negative performance factor, depending on the original engineering of the model saw. Changing the ports can compensate for that and bring the whole thing back to better than it was when stock.

 

[mastermind7864]

I suggest that all our saws be used at 32:1

I do a bunch of M-Tronic and Autotune saws Cory.

Here's a 562XP I did a couple of years ago....

<iframe width="420" height="315" src="//www.youtube.com/embed/qtqIqkR00Jw" frameborder="0" allowfullscreen></iframe>

 

[pantheraba]

Derails are fine...some of our best info exchanges comes in derails--or maybe we should call them sidetracks. We eventually get back on the mainline track...but sidetracks are good, too.

 

[mastermind7864]

I sorta hang out here with you guys to get away from the saw talk.......and damn if I didn't get it going.

I do about 220 ported saws a year....it's a 60 - 70 hour a week gig for me.

 

[cory]

Yes, sorry for the derail. I for one am learning a lot quickly though. Ah, the House.

Jay, what do you have to do to the ports?

That 562 looks pretty eager! Mastermind, after you lathe-up the auto tune saws, their computer just adjusts the fuel air mixture as necessary? I woulda guessed that fairly major changes would be too much for the supplied 'puter to deal with.

 

[mastermind7864]

Naw.....those AT saw like being molested.

 

[cory]

Hahaha! They are probably like, "free at last, free at laaaaast."

Are tweaked saws automatically louder than stock saws, or not necessarily?

 

[woodworkingboy]

That is both a deep and controversial question, Cory. Widening and or raising ports, sometimes polishing, I think covers a lot of territory, and each port is looked at differently as a rule. Also doing nothing. If you think about it a bit, saying that the saw ran good when stock, what would you basically have to do if you lowered the cylinder? Wanting to bring the timing back to stock for the opening of the exhaust and transfers, means raising them back up to where they were in relation to the top dead center and bottom dead center during the piston stroke. I think that then you are basically back to stock timing with raised compression, but with longer opening durations (transfers). I have often read of that being a sort of basic approach to modifying. Randy will hopefully correct me if I am wrong.

 

[cory]

but with longer opening durations (transfers).

Is that because the port is physically larger, taller, than it was before modification? Probably yes, dumb question, but Im trying to understand this stuff, its all brand new to me. thanks.

 

[mastermind7864]

When lowering the jug, you will gain intake (and strato) timing, that is great on some, not so great on others. Then on many engines (like the MS660) not raising the exhaust back up is what you want. In the case of the 660, less exhaust is a fine thing. The transfer timing is where the big gains are, and where they need to be (for me) has been the result of a shit load of trial and error. I've been doing this awhile, and do a bunch of units. For each model I have a spec sheet that I've but together over the last few years. That sheet or "recipe" tells me exactly how much to remove from the squish area, where to set EX timing, transfer height, etc.

This is the sheet for the MS660.


MS660

Stock:
Compression: 150psi
Squish: With Base Gasket .024
Ex: 94°
Tr: 123°
In: 80°

Ported:
Cut .060 from squish band and .045 from base.
Compression: 200psi
Squish: .023
Ex: 98°
Tr: 120°
In: 83°

Notes: 118° on the transfers seems stronger, but may not pull a long bar as well.

Cutting .080 from squish and .065 from base gets the exhaust port to 100

 

[cory]

Damn, there's a shitload of hard won knowledge right there in black and white.

When you say "Ex:94*", what does the * mean, is that an angle?

 

[woodworkingboy]

It's degrees in relation to the piston stroke. Top dead center and bottom dead center are given opposing numerical values. You have to hook up something that tells you that, a wheel type graph that you read with a fixed pointer, i guess you could call it. As the piston moves, the wheel turns, connected to the crank shaft. Everything opens and closes in relation to those diametrically opposed positions, the piston going up or down or briefly stopped at tdc or bdc

Widening transfers and exhaust is sometimes done as well, Cory. Probably exhaust is the more common. One of the objectives of saw building can be increasing the flow of gases, both in and out of the cylinder. Some guys work on pistons to do that as well.

 

[cory]

Cool. Uh, last question: are tweaked saws always louder than stock, or not necessarily?

 

[mastermind7864]

Damn, there's a shitload of hard won knowledge right there in black and white.

When you say "Ex:94*", what does the * mean, is that an angle?

Ex: 94° means that the exhaust port opens at 94 degrees of crankshaft rotation from top dead center or TDC.

Widening transfers and exhaust is sometimes done as well, Cory. Probably exhaust is the more common. One of the objectives of saw building can be increasing the flow of gases, both in and out of the cylinder. Some guys work on pistons to do that as well.

I don't do anything to the piston because I don't want to do anything that could cause the piston to fail over time. I also don't widen the ports much, I just open them to the edge of the factory bevels. A wide exhaust port makes the rings wear too quickly. On a upper transfer port, overly wide ports don't scavenge well, and can hurt performance.

What really makes an engine perform well is a combination of compression increases, and well planned port timing numbers. Widening the ports nets a very small gain in the overall porting plan.