High Compression Saito 180 (FA180HC CDI Project)
For Those not familiar W/this project, it entails installing an FA180 cylinder & rotating assembly in the FA150 case. The FA150 case has a deck that is .055" shorter than the FA180. This results in a substantial boost in compression.
The good news is that the 180 crank is dimensionally the same as the 150 crank except for the increased stroke & larger journal diameter & length. It fits right into a 150 case W/the same bearings. No modifications are needed to fit the 180 crank into a 150 case.
I did a bit of dismantling today to take PIX of the machine & hand clearancing work.
I used a "Q" Tip W/Dykem to highlight the places where material had to be removed. The blue highlights are pretty crude & just show the general area where metal had to be machined or hand worked for clearances.
The 1st area of concern is the spigots on the bottom of the cylinders. The FA150 cylinder on the left has a spigot that starts out @ the same diameter as the FA180 cylinder, but it steps down to a smaller diameter. The top of the case has the same step in the opening.
The blue dye shows the general area where the bore in the case deck is machined to the larger diameter. One can set-up on the top of the bore & continue that diameter to a depth that will clear the straight wall of the FA180 cylinder base spigot.
The previous step is the only metal removal that is dimensionaly critical & requires machine shop capabilities. The rest of the clearancing was done by hand as I do not have access to machine tools in my own workshop.
The next step was to clearance the case for the piston skirt. The bore of the cylinder base opening was protected W/.015" wax strip & the clearancing was done W/a large 1/2 round file & emory cloth on both sides of the case in the blue died area.
The (ringless) piston can then be installed on the conrod & inserted into the cylinder bore to check for adequate clearances W/the case.
Now, the real work begins. The longer stroke & larger jourrnal of the FA180 requires the clearance groove in the 150 case to be widened & deepened to a minimum depth of .060". The FA180 has a .070" depth in this area, but the case thickness of the 150 is only .100" while the 180 has a thickness of .140". Since I did not want to make the case any thinner here than absolutely neccessary, I cleaned up the forge parting line on the conrod to allow the shallower groove.
I did not thin the material beyond the minimal amount that needed to be removed to clean up the parting line.
I then did the laborious task of slowly working the groove deeper using a dremal tool W/a drum sander, constantly montoring progress untill I achieved a fairly even .060" depth.
The end result was clearance for a .008" feeler gauge in the groove when the crank was rotated W/the rod on the journal throughout the rotation of the crank.
Merely bolting the 180 top end onto the 150 case would have resulted in an estimated 15.7:1 CR. That would also have resulted in less than .015" quench hieght & interferance W/the intake valve even when the valve remained @ .000" lift on the seat. I opted to add a .020" cylinder base shim from C&H Ignitions to allow better piston/deck clearance.
This should still allow a healthy boost in estimated CR to 12.7:1, a substantial increase from the stock 9.6:1.
Even @ that increased deck clearance, I still had to massage the intake valve pocket outboard a bit to achieve adequate P/V clearance.
The FA150 back cover will have to be milled .045" to clear the longer rod jorrnal of the FA180 crank/rod. The price of e new FA180 back cover is only $10.40 so I opted to just purchase one of those.
In addition, the shorter case deck will cause interferance between the cylinder spigot & back cover.
W/O the C&H .020" spacer plate under the cylinder, the interferance was substantial so I used a safe file to make a small flat on the top of the rear cover.
W/the spacer plate, the interferance is minimal to none, but it probably wouldn't be a bad idea to relieve the top of the rear cover just a little to be safe.
I am going to employ a Saito solid aluminum engine mount to give added support to the modified case.
I can now start the final assembly. Stay tuned for test run results.
I realize that some of my methods might seem crude, but any dimensions that were critical were done via machine shop. After this prototype work, dimensions can be used for more precise machine work if desired, but I wanted to do as much work as possible that could be done in the average hobbyist's shop to keep costs down. Many of us have more time than money.
The same results could be achieved by reducing the deck on an FA180 case by .035" & checking the valve pockets & rear cover for clearance.
I had a clapped out FA150 on hand & was able to re-use a lot of the FA150 parts that were common W/the FA180.
This project would be a very viable option for someone that has a tired 150 that needs a cylinder/piston/valve replacement.
The difference in cost would be minimal for the cylinder/piston/wrist pin/rod/ring/valves. The 150 rear cover could have the depth reduced by .045" if machine shop capabilities were "in house".
The price of a new 180 rear cover was less than the cost of outsourcing milling the cover down. ($10.40)
The rest of the valve train is interchangable.
These components would not normally be replaced in a top end overhaul.
My machiune shop bill for case work not done by hand...$30.00
Cylinder base spacer from C&H..$6.50
Total added cost over a standard 150 top end rebuild...$126.86
Total cost....$346.75 ($113 less than a new FA180, $233 less than a new FA220)
I have both a 180 carburetor/manifold as well as the 150 counterpart. I'll do my initial tests W/the 180 components to get a comparison for the added HP. (if any) I'll then swap the 150 carb/manifold for the 180 & see if there is a significant drop in performance.
After glow ignition tests & will convert to C&H EI & test for added performance. I expect to see the biggest gains W/EI as it will allow me to tailor the ignition advance to maximize HP. GI won't be as versatile in that respect.
I want to also test 40% Nitro R/C car fuel W/the spark ignition for short burst power to be used intermitantly during aerobatics. The engine is slated for my Hanger-9 25% CAP 232. I would not surprise me to see close to 3 1/2 HP on the high nitro fuel. My GI FA180 made 2.91 HP on 15% Cool Power & I expect a boost W/the standard CR 180 to about 3.2HP when converted to EI. The high comprssion version should get se a HP gain from that even on 15% fuel. W/40% nitro it should be a real stump puller albeit only for short intervals.
I will also (eventually) instal my extra FA300TTDP crankcase pump check valves so the fuel tank can be mounted over the CG W/O fuel delivery problems. I am waiting for information on the proper thread for the check valves so I can drill/tap the cam housing for the outlet check before I can start final assembly.
I had only posted a few pages of the RCU High compression 180 thread over on the Club Saito thread.here on RCG.
I am deleting the pages here on the Club Saito thread & linking them to this thread as I post here. I do not want to raise any double posting issues.
Eventually I want to post all of the relevant pages here.
I have done several test runs of the engine including comparisons of the 180 Vs 150 carb/manifold.
I have a big bore 220 carb W/pump on the way from Advantage Hobby. Since the 220 uses the 180 carb stock, & the "big bore" carb utilizes the same manifold, it should be a bolt on modification. I also already have the pump check valves in the crankcase/cam housing for fuel pressurization.
I might experiment W/manifold porting to match the bore of the bigger carburetor.
Right now I'm getting eveyrthing in order to do comparison test runs for:
FA180 (standard compression) glow ignition
FA180HC (high compression) CDI W/180 carburator
FA180HC CDI W/220 big bore carburetor/stock 180 manifold
FA180HC CDI W/220 big bore carbutetor/ported 180 manifold
All during the same test session to minimize DA variations.
I also want to P/U a qt of 30% nitro R/C car & Buggy fuel to explore high nitro performance.
RCU will not allow direct image posting in my threads so I'm going to see if this forum will have issues W/me doing so.
Using attachment imaging disrupts the flow of the illusrtated text.
Last edited by SrTelemaster; Oct 19, 2012 at 09:23 PM.
It's alive! It's alive!
I got the FA180HC fired up & running last night & made a few test runs before it got too dark to use the optical tach.
On glow, it fired right off W/the electric starter. It idled great @ 1400 RPM.
HS was another story. After running it for about 40 minutes @ lower RPM levels, when I tried WOT it would spit, die & loosen the prop. it even threw it across the garage once.
I was able to do a few pulls @ WOT but I was afraid to stand in front of the prop to get an RPM reading. (I have to face the garage door to get an optical tach reading)
Even @ that, WOT was slobberingly rich & unstable.
This morning I tried raising the tank above the needle valve W/O success. Even then I would get backfire. Looks like detonation is a problem. Maybe a colder plug would work better.
Well, the only reason I wanted to run on glow ignition anyway was for a baseline & comparison to the stock (GI) FA180 I have, so I broke down & installed the C&H electronic ignition.
What a difference. Stable idle @ 1200 RPM, far less fuel consumtion/smoke/mess & 8400 RPM W/the 18X8 Dynatrust prop!
By comparison, the stock glow ignition FA180 spun the same prop @ 8000 RPM developing 2.92 HP. The FA180HC on spark ignition made 3.38 HP. A 16% increase in HP, .46 HP!
I expect the fuel consumption to be far less also as higher CR usually equates to better fuel economy. That coupled W/the usual 22%-25% boost in fuel economy W/EI should make abig difference.
Now, to try some 33% Nitro/18% oil R/C car/buggy fuel! I'm already close to the power level of a glow ignition FA220.
33% nitro might push my power above that! All that W/far lower fuel consumpsion.
I love C&H spark ignition!
I'll get some videos up when I get a chance.
The addition of a 12mm FA220 Big Bore Craburetor as well as using 30% nitro, 8% lube glow feul has upper the N/A FA180 performance bar to 3.95HP & 23# static thrust.
Yoi can read about the power improvements in detail here. https://www.rcgroups.com/forums/show....php?t=1769449
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