SrTelemaster150

1st of all quit calling a CDI fired engine a "Glow Engine" it can run on either gas/oil, methanol/oil, or glow fuel. Even a glow fuel carburetor can be modified to use gasoline, it's just easier/cheaper to switch to a $15 ZAMA. A better term would be "CDI/Methanol" engine. It is NOT a "glow engine", it has more in commoin W/a gas engine. Some might argue that I shouldn't post about my CDI/methanol engines on the "Glow Engine" forums.

I'm not critisizing you for wanting an FG84, just don't expect it to be a powerhouse as it will barely make FA450 power if indeed it does. None of Saitos other FG engines make the same HP as their similar displacememt FA conterparts. The average drop in power is 15%. Saito has started increasing the displacement on their recent gas versions. IE the FG57 & FG84 that are increased in displacement over the FA counterparts. 14% for the FG57, about 12% for the FG84. This will make up for most of the usual 15% drop in power when gas is utilized over glow fuel W/GI.

I wouldn't even consider converting the FG84 to methanol, & here's why. Most likely W/the 180 top end/150 bottom end geometry the CR would be way too low (less than 8:1) to take advantage of the methanol. It would not make the same HP as a CDI/methanol version of the FA450 @ the higher stock 450 CR.

But that does bring me to an interesting idea!

I have had a brainstorm raging in my head since last night & I need to hobble up to the hanger room to check it out.

A Saito FA300T is 4.5mm taller than an FA150 from the crank centerline to the top of the rockers. That means that the distance from the rod jounal C/L to the piston crown will be taller too, albeit maybe not the full 4.5mm if compression ratios for the 300T are lower than the 150.

Since the 300T has a different piston part# than the 150/450R3, (the 150 & 450R3 use the same piston) it would seem that some of the added distance is probably taken up by added "compression hieght" (the distance from the wrist pin C/L to the piston crown) I have an FA150 top end lying on the work bench & there's an FA300T under it. It wouldn't take me long to pop a jug off the 300T & compare compression hieght of the 300T piston W/the 150 piston.

Here's where it gets intereresting.

Hopefully most of the 4.5mm is taken up by a longer C-C distance on the conrod. If the compression hieght of the 300T piston is greater than that of a 150/450R3 piston in the neighborhood of 1mm to 2.5mm, the 300T piston could be used in a 450R3 to raise the compression ratio significantly. The 450R3 uses the same piston ring as the 300T so a 300T piston will fit the 450R3 bore.

Anyone getting interested now?

If I can use 300T pistons in a 450R3, with or without .020" cylinder base shims to raise CR to the 13:1 range like my FA180HC engine., I could significantly raise power output. Raising CR to this level would not be feasable W/pump gas as the octane rating would be too low. Methanol has a comparative octane rating of 114 as far as resistance to detonation.

Converting a high compression FA450R3 to CDI W/induction improvemnt like an 11mm FA180 carburator, (the 450 carb is 9mm) would lead to a significant HP increase. In the FA180, going from the 2.81HP GI version to the CDI high compression version W/the 12mm Big Bore 220 carb that produced 3.45HP on the same 15% Cool Power fuel, resulted in a 23% HP boost while using 20% less fuel.

If the modified 450R3 responded W/a like 23% power boost, that would be 6.8HP. Furthermore, tipping the can W/some 30% nitro/8% oil boosted the high compression BBC version of the 180 another 14% to 4HP & still got better fuel economy than the standard GI FA180. A like increase for the modified 450R3 running 30% nitro would be in the 8HP range.

Dropping back to a straight methanol/8% lube mix would probably not loose much over the 15%/17% nitro/oil mix of the Cool Power but let's just back it off a little to say 6.5HP. Tests done by others W/CDI conversions have seen fuel consumption drop by 50% when straight methanol was used compared to nitro mixes W/GI.

Now I would have a 450R3 methanol engine that would make 6.5 HP W/about double the fuel range (1/2 the operating costs) of a standard FA450 on GI.

If I want to show off, I can tip the bottle to 30% nitro, open up the HSN a bit & make 14% more HP W/45# of static thrust. A 26# warbird W/45# of thrust on hand would be a lot of fun when you want to go vertical.

For me, it's all about the engines & getting the most power out of the smallest/lightest powerplant that is still dependable & easy to live with.

There's a reason that the big boys in drag racing use methanol fuel.

Best of luck W/your FG84. If Saito has ironed out the ignition & carburetor problems that they had in the past, I'm sure you will be very happy with it as long as you aren't expecting a big power increase over an FA450.