SrTelemaster150

Over the last few days I had the opportunity to test performance of 4 different versions of FA-180 engines, all burning 15% Cool Power fuel lit off with CDI. The initial advance setting for the spark was 35* BTDC. A Dynathrust 18X8 propeller was used for all tests.

The base version was an otherwise stock FA-180 with CH-Ignitions CDI.

A few days ago I did a baseline pull of 7800 RPM. This was off about 200 RPM from the best previous performance of this engine. Cold damp weather was obviously putting a damper on performance. I also did a control pull with my 12.7:1 high compression version FA-180 with the 12mm Big Bore carburetor, ported intake manifold & Bowman ring set up with .002" end gap. That engine pulled 8400 RPM with the same propeller.

Since those test runs, in the stock engine, I installed a Bowman ring on an FG-57T piston with the end gap set up at .002" just like the high compression engine.The FG-57T piston has a .016" taller compression height to maintain the same 3.4cc combustion chamber as an FA-180 in the FG-57T engine that utilizes the bore of the FA-180 on the FA-150 based stroke of the gas twin.

The taller FG-57T piston in an otherwise unmodified FA-180 results in a compression increase to 10.7:1 from the stock CR of 9.6:1.

Here are the results:

Stock FA-180 CDI---7800 RPM

FA-180/FG57T piston 10.7:1 CR---8050 RPM

FA-180/FG57T piston with 12mm carburetor/manifold--- no performance gain

FA-180/.035" case deck reduction 12.7:1 CR---8200 RPM

FA-180/.035" case deck reduction 12.7:1 CR with 12mm carburetor/manifold---8400 RPM

The fact that the 12.7:1 CR engine pulled the same RPM as it did on the day that the baseline test with the stock FA-180 CDI validates the comparison of the data from the 2 different test sessions.

Conclusions:

The CR boost to 10:7:1 using the FG-57T piston with the Bowman ring was good for a 250 RPM power gain.

Although the 12mm carburetor/manifold is good for 200 RPM withe the 12.7:1 CR engine, the breathing ability of the modest 10.7:1 CR was not improved enough to benefit from the improved induction.

Increasing CR from 10.7:1 to 12.7:1 resulted in another 150 RPM gain.

The 12.7:1 CR improved breathing to a point where the 12mm carburetor/manifold induction improvement resulted in another 200 RPM.

The FG-57 piston is an easy "plug & play" modification that is a simple bolt on modification that does not require any clearance checks.

I will tear down the engine with the FG-57T piston to have the case deck reduced by .020". This will have the same result as reducing the deck by .035" with the stock FA-180 piston. The CR will be increased to 12.7:1 but valve notches will have to be checked & most likely clearanced. I will also port the manifold & employ a 12mm carburetor.

Hobbsy

My Feedback: (102)

Those are solid gains, some day I'd like to buy a MicroMark lathe and play like that.

SrTelemaster150

The only part that needs a "machine shop" is the deck reduction. Every thing else can be done W/a Dremel tool & drill press.

The Dremel to relieve the valve pocket, the drill press to port the manifold if you are clever enough. I use an 11mm bit to locate the center of the FA-180 manifold, then switch to a 12mm bit to ream the updraft portion only.

Milling the case deck shouldn't cost over $20.

blw

My Feedback: (3)

Good info, Dan. The ring gap results are interesting. This would be priceless if running Saitos in the SPA, especially around the OS bunch.

SrTelemaster150

When I built my prototype high compression FA-180, I found that bolting the FA-180 top end onto the .055" shorter FA-150 case resulted in a compression height that was too tall for adequate cylinder head clearance. A .020" cylinder base shim resulted in a net deck reduction of .035 which still required minor valve pocket relief for adequate valve/piston clearance.

Some other interesting facts came to light. Not only is the FA-150 case .055" shorter than the FA-180 counterpart, the FA-180 conrod is longer by a similar amount. This brings another interesting combination to light.

Since the stroke of the FA-150 is 1.1mm shorter than the FA-180, utilizing an FA-180 conrod & top end on an FA-150 case would result in a net compression height increase of .033" compared to stock FA-180 specification. This would result in a 12:1 CR engine of 1.71 cu. in. or 28cc.

The FA-180 isn't 1.80 cu. in. nor is it really 30cc. The actual displacement is 1.77 cu. in. or 29.1cc.

An FA-171 W/12:1 CR should make considerably more power than either an otherwise stock FA-150 or FA-180. The more efficient breathing of the smaller 2.55cc combustion chamber would also most likely benefit from the 12mm carburetor/manifold modification.

In fact, I would think that power output with the larger carburetor would be very close to that of the 12.7:1 high compression, 12mm carburetor/manifold version & significantly better than the 10.7:1 medium compression version of the FA-180.

Looks like it's time to tear down the Stock FA-150.

captinjohn

I have a question or two. When a person sets up a 1.5 Saito to produce more power, how will that effect how long the engine may last? If you are using glow fuel, is high nitro in the fuel really needed? The spark should set off the right time of ignition. I would like to get away from nitro because of its corrosive properties & the possibility of pre ignition from heat or a hot plug electrode. May be thinking wrong. That is why it is a question. Thanks John

SrTelemaster150

Utilizing the FA-180 top end in itself should not reduce durability. However, the FA-150 does have an 8mm rod journal compared to the 9mm journal of the FA-180. That & the added cylinder pressure of the higher CR would, in theory, reduce engine life. The other components, crank bearings, valve train, etc. will be the same as those of the FA-180.

If you ran the engine @ constant WOT, engine life might be reduced somewhat, but most likely there would not be a significant difference under normal use. This is not like changing cam specs to make HP through a higher RPM TQ envelope. In this particular case, HP is increased by increasing TQ throughout the RPM range, not raising the power curve. The extra power will be available throughout the power band.

The only machining that would be required would be to bush the FA-180 rod for the 8mm rod journal. Some minor clearance work would need to be performed such as cleaning up the forge parting line in the big end of the conrod to clear the case as well as working the valve pocket on the piston crown W/large sanding drum on a Dremel tool for valve clearance on the intake side.

I am going to have 2 or 3 FA-180 rods bushed. If you are interested I could supply you W/a modified rod.

The other parts you would need would be the FA-180 piston, ring, cylinder & valves. The stock FA-150 manifold can be modified to accept I either a stock 11mm FA-180 carburetor or the 12mm FA-220 big bore carburetor.

The stock 10mm FA-150 carburetor/manifold could be utilized if you want to swing a big prop @ lower RPM as it would still make a lot more TQ than the stock FA-150.

Bear in mind that CDI will be needed to make these modifications practical. You will also be able to totally eliminate nitro although power will be diminished somewhat. High nitro will not lead to pre-ignition W/CDI. The fixed timing event of CDI does not change W/nitro content. I have run tests W/both 15% & 30% nitro @ the same 35* BTDC spark timing. The 30% nitro increased power output by an additional 400 RPM.

EDIT: It just occurred to me that the bore for the cylinder spigot in the case will have to be relieved to accept the straight walled spigot of the FA-180 cylinder. This is a machine shop operation. The case will also need to be clearanced for the skirt of the larger diameter FA-180 piston skirt. This can be done by hand W/a half found file & Emory cloth.

blw

My Feedback: (3)

I wouldn't worry too much about the nitro. At one time, maybe not now, some synthetic oils were acidic.

SrTelemaster150

Post #7 edited.

Hobbsy

My Feedback: (102)

Thanks to Dan I'm setting up my 1.50 S with C&H Ignition. I have it set at 35 degrees BTDC and will go from there. It is difficult to tke pictures of Photo Paper, plus I had to be very careful holding the camera or it would appear the I had the timing off a degree or two. Picture #1 shows the Hall Effect sensor inverted and on the wrong side. Don't know how that happened.

bob62

My Feedback: (28)

To heavy for my shallow mine

rafeeki

My Feedback: (11)

Can i run the FA180 inverted?
Can I turn the carb intake tube sideways or even pointing down in an inverted installation?
What should be the position of the fuel tank relative to the carb?

SrTelemaster150

Yes you can run the FA-180 inverted. I ran an FA-150 as well as an FA-91S inverted, both W/CDI. The only issue is that you must watch your starting technique to avoid flooding the engine as hydro lock can occur. It never happened to me though. I do cant the engine to the starboard side so that the exhaust valve is located @ 6 o'clock to allow any accumulated oil to drain.

Leave the carburetor/manifold location alone as twisting it to the side or down will drastically change the centerline relationship of the needle/fuel tank.

Joespeeder

Hey SrTelemaster,

Did you ever build a Saito 150 as you discussed here?

A good friend is currently building the FG-57 pistoned 180 and is having a great time with that project.

Joe

SrTelemaster150

I have had the case machined to accept the FA-180 cylinder & it is bolted to my engine assembly stand on my bench. I also had an FA-180 case deck reduced by .052" so I can explore various geometry.

I'll be getting to clearancing things shortly. I can build several versions of FA-150 stroke/FA-180 bore. (FA-171)

Prototype-1) FA-150 rod/FA-180 piston (low compression single cylinder FG-57)
Prototype-2) FA-150 rod/FG-57 piston (single cylinder FG-57 geometry)
Prototype-3) FA-180 rod/FA-180 piston (about 12:1 compression)
Prototype-4) FA-180 rod/FG-57 piston (about 14:1 compression)

One of the last 2 prototypes will be the basis of my FA-512R3 methanol radial.

As for the FA-180 case, I want to try the FG-57 piston on the .052" deck reduction. If it can clear the valves it will be very, very high compression. The stock FA-180 piston in that case will be over 14:1. & should clear if the 4th prototype FA-171 does.

Joespeeder

Thanks SrTelemaster,

Will you start a new thread when you get to the the point of assembling and running the various combinations ?

Joe

SrTelemaster150

Yes I plan on doing a "Big Block Saito Hybrid" thread that will outline all of the various geometry version W/performance tests.

Hobbsy

My Feedback: (102)

Looking forward to it, thanks for going off the beaten path, so to speak, good stuff.

Joespeeder

Terrific !! Thanks.

I'm looking forward to it. My friend, John, was running your 180/FG-57 piston combo at our field last Tuesday. He's really happy with it and it was running perfectly on glow. Next he'll be doing the CDI set up and then it goes in his Dr1 to replace a DLE 30. It's his first engine tear down and rebuild of any kind so he's just enjoying the process.

Thanks for all the great info.

Joe

aviation421

My Feedback: (68)

Hello SrTelemaster,

Well, after you convinced me to go CDI glow instead of Gas, I modified my Saito 180 with the FG57 piston....at first...I was only getting 6900 rpm with a 18x8 master airscrew and 20/20 cool power...I tried to time it at 35 btdc and I timed it incorrectly...my friend JoeSpeeder helped me time it and now I get 8100 rpm still with 20/20...I will try it with 15% next...my friend JoeSpeeder calls it....FrankenSaito....I guess I am in the right track with the frankensaito?
Thanks for all your information....we are having fun with this mod.
I know that it is probably overkill, but it will go into a 1/4 scale BUSA Fokker DR1.

John

SrTelemaster150

The higher flash point & slower flame front of methanol requires more ignition advance to get the most power/efficiency.

8100 W/an 18 x 8 sounds about right. You may gain a little more W/some more break in. There is no need for 20% lube W/CDI.

the Wasp

My Feedback: (1)

what we need is some one that will grind us some custom Cams, and or High Ratio Rocker Arms, and of course larger Valves

Jim

SrTelemaster150

The cams would be of little benefit as our engines can run at near peak HP with the correct propeller. It's not like we are trying to pull a 4000# car out of the hole and still have enough top end power for speed. The engines already have big enough valves and aggressive cam grinds to begin with.

Increasing compression, unlike cam grinds & valve size does not rob Peter to pay Paul. Increased compression make more torque across the entire RPM range. More aggressive cam grinds and larger valves will shift the torque curve up RPM range but degrade low end torque & idle..

The high compression FA-180 already makes nearly 2 HP per cubic inch with mild nitro percentages & it can exceed that benchmark with more nitro.

Hobbsy

My Feedback: (102)

Dan, I'm sure you have calculated your compression ratio, how does it compare to my old .80 with 15.5 to 1 and my old 1.50 with 11.24. Thanks, Dave

Sorry, I see it just above, not enough coffee yet.

the Wasp

My Feedback: (1)

to each his own I guess, besides, I was not suggesting that we all start ordering cams that are ground 50, 60 or 70 degrees over stock numbers.

if you back up your statement about "cam aggressiveness" by posting duration numbers at .006" Lift and .050" Lift you would then have told me something


BTW, unless these stock cams are more aggressive than I believe they are, increasing the intake's rocker arm ratio by 1.00 will only change the intake valve's duration by 2 or 3 degrees IF that, hardly much to boast or complain about, yet will increase the idle's smoothness without raising the idle's RPM much at all, as well as producing more power throughout the powerband.. increasing the exhaust's rocker arm ratio will suffer low end torque some

like I said, to each his own