ORIGINAL: Old Fart
I understand the fun tinkering can be but why not just run more nitro and be done with it? 400 bucks can buy you a lot of it.No offence intended.
I would have to spend $$$ to rebuild the FA 150. Some of that $400 would have been spent anyway (tappets, bearings, valves, springs) I will also have "spares" for my other FA 150.
As far as the nitro goes, I am experimenting W/E85 & have gotten within 200 RPM of what I got on 15% Cool Power @ a cost of $6.75 a gallon. 15% Cool Power costs me $22.99 ($24.60 W/tax) when I buy it by the case in the rural area where I live. $26.99 + tax if I buy it by the gallon. More nitro would really up the ante.
Even @ the current 15% content, $400 would only buy me $16 gallons of fuel. That's about 1 season's worth.
You must also consider that all but one of my Engines (FA 91) are 150 or larger including another FA 150, an FA 180, a 300 TTDP & I plan to purchase a 200Ti & 450 R3 soon, so upping the nitro would be very cost prohibitive due to my rate of consumption.
Testing on the new FA 150 running on glow plug, then C&M Electronic Ignition showed these results.
15% Cool Power running on glow ignition:
7700 RPM, 18X8 Dynathrust prop, minimum reliable idle @ 1700 RPM, 9m 45s run time on 16 oz @ WOT, 231*F head temperature after full run @ WOT
15% Cool Power on C&M spark ignition:
7800 RPM, 18X8 Dynathrust prop, minimum reliable idle @ 1400 RPM, 12m 00s run time on 16oz @ WOT, 271*F head temperature after full run @ WOT
E85/KLOTZ 15:1 mix running on C&M spark ignition:
7500 RPM, 18X8 Dynathrust prop, minimum reliable idle 1400 RPM, shut down after 15m W/about 1/2 of the 16oz tank left, 291*F head temperture after 15min run A WOT
I have experienced erratic tuning issues W/the E85 using the glow carburetor. I am going to test a pump/regulator for ST Engines that should aleviate those issues W/O the expense/weight & space penalties of switching to a Walbro carburetor.
I realize that the big prop is a bit oversized & is contributing to higher cylinder head temperatures.
The E85/KLOTZ 15:1 mix costs me $6.75 a gallon. If I can extract a bit more HP from the E85 by utilizing higher compression (E85 has a much higher octane rating than gasoline) then I will be way ahead cost wise.
Fuel consumption on the E85 on spark is less than 1/3 of what it is on glow ignition running nitro. W/the cost of the E85 being about 27% of the 15% Cool Power, given 3X more run time, that's about 9% of the cost of running glow fuel on glow ignition.
Even W/glow fuel, when running on spark, I get almost 25% more run time from a given amount of fuel.