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increasing compression on Saito 4S..!?

Old 05-18-2007, 04:50 AM
  #51  
canardlover
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Default RE: increasing compression on Saito 4S..!?

ORIGINAL: RVM

Why is everyone thinking I'm going to do this to a brand new engine?



RVM, I´m truly sorry if I have I have embarrassed you by my remarks that was certainly NOT my intention...SORRY..!
RVM, is there any chance you could measure the CR of your Saito.82 engine.?..I have not access to a Saito.82 but have seriously considered to buy one second hand. So if you could measure CR and give me a description (or even photo) of the combustion chamber shape I would be most grateful. Used Saito engines are plentiful here at present since most people are converting to electric flying now.
Attach pics of the syringe graduated in mL that I use for filling ATF oil in the "head space"...Cheers/Harald
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Old 05-18-2007, 10:09 AM
  #52  
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Default RE: increasing compression on Saito 4S..!?

Nah I'm not embarrassed or anything. I was just wondering more than anything else.

My .82 dropped a valve so it is in the shop at Horizon. I should hopefully get my replacement next week some time. I'll see if I can get you some measurements when I get it in.


ORIGINAL: canardlover

RVM, I´m truly sorry if I have I have embarrassed you by my remarks that was certainly NOT my intention...SORRY..!
RVM, is there any chance you could measure the CR of your Saito.82 engine.?..I have not access to a Saito.82 but have seriously considered to buy one second hand. So if you could measure CR and give me a description (or even photo) of the combustion chamber shape I would be most grateful. Used Saito engines are plentiful here at present since most people are converting to electric flying now.
Attach pics of the syringe graduated in mL that I use for filling ATF oil in the "head space"...Cheers/Harald
Old 01-20-2011, 05:12 AM
  #53  
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Default RE: increasing compression on Saito 4S..!?

Hi again all engine tinkerers..!
I think I owe you all an update on how my modded engines do perform:
Finally last summer I took six Saito engines and placed them in my test stand using the same reference propeller (Ishipla 11 x 7½), same fuel 12% synthetic + 6% castor + 5% nitro, the same brand new OS F plug and attached you will see the results.

Special notes:
1)I chose to run all engines on 5% nitro as a compromise to have them all run acceptably well.

2)Overall it seems that milling the crankcase does not increase power much but the engine certainly runs better on 0% nitro which was my goal from the outset.

3)The .50 GK(HB) engine fitted with the longer conrod is so far a failure but I do NOT know why.

4)The .56 (LJ) engine with the “swiss-cheesed” piston is still running strong after 5 seasons use in my Sig Cougar airplane. This is a pleasant surprise to myself and probably some of you too…=)..! Admittedly it does spit out more oil from the crankcase nipple than normal and it has developed a slight bearing noise so I guess it is a bit “over the hill” by now. Will dismantle soon.

5)I cannot explain why the .56(AL) engine has a CR of 10.7 after only 1.0mm milling but that is the case after two separate measurements.

The Enya.60 engine (post # 19) was also tested here but that is another story to be told later…Cheers/Harald
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Old 01-20-2011, 01:05 PM
  #54  
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Default RE: increasing compression on Saito 4S..!?

Hello Canardlover,
Great and EDUCATIONAL to read this thread from the beginning. Thanks!

I have worked much with 2-strokes over the years, but my experience with 4-strokes is limited to YS.91. Oh, yes, I also flew an RCV 120 for a brief time but that is another story... My reason for buying YS was mainly that it takes in the fuel mix with fresh oil through the crankcase to provide good lubrication to bearings and camshaft. It's just a pity that it requires so much nitro, 10-20%.

So I appreciate that your Saito.56(LJ) with "Swiss cheesed" piston spits out more oil. I'm looking forward to see what you find after dismantling.
Old 01-20-2011, 05:45 PM
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Default RE: increasing compression on Saito 4S..!?

Good to see canardlover keeping us updated. I haven't really flown anything in a few years. Finances got real tough so I had to sell all my R/C equipment. I am now about to start rebuilding and stroking a 4.0L I6 Jeep engine though.
Old 01-30-2011, 02:50 AM
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Default RE: increasing compression on Saito 4S..!?

To any tinkerer it may concern: in case you tinker with a Saito AAC engine I will hereby issue a warning. If you push the piston/ring/conrod assembly to far into the cylinder bore while assembling an engine you may hear a distinct click..
If that happens the piston ring has snapped open into a sharp recess at the top of the cylinder bore and you are TOTALLY STUCK....[:@]......!(see pic)
It happened to me and the only solution appears to be brute force, in my case destroying both piston crown and ring in the process. So be warned about this but I hope it will not stop you from tinkering. ABC engines I have dismantled do NOT have this sharp recess.
Also attach a pic of a most useful book for you tinkerers to study. Still hope to be able to compare notes with other "Saito-tinkereres" out there....Cheers/Harald
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Old 03-24-2012, 02:34 PM
  #57  
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Default RE: increasing compression on Saito 4S..!?

Hello again, another update on the Saito CR increase and some more "swiss cheesing".. Recently bought a Saito .72 GK in good shape and as usual I could not resist to take it apart for a closer inspection. Everything was in good order except that it was equipped with the early plastic rear crankcase cover which is rather flimsy. So I bought a new reinforced cover and gave my usual "swiss cheese" treatment and milling of the crankcase to take off 0.8mm for an increase in CR.
This time I went a bit further in my lightening of the conrod. I drilled four holes each 4.2mm dia. which is more than ever before..[X(]....!! See pic of the setup and wish me luck, testing it very soon...Thank you..!
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Old 03-24-2012, 06:25 PM
  #58  
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Default RE: increasing compression on Saito 4S..!?

ORIGINAL: canardlover

To any tinkerer it may concern: in case you tinker with a Saito AAC engine I will hereby issue a warning. If you push the piston/ring/conrod assembly to far into the cylinder bore while assembling an engine you may hear a distinct click..
If that happens the piston ring has snapped open into a sharp recess at the top of the cylinder bore and you are TOTALLY STUCK....[:@]......!(see pic)
It happened to me and the only solution appears to be brute force, in my case destroying both piston crown and ring in the process. So be warned about this but I hope it will not stop you from tinkering. ABC engines I have dismantled do NOT have this sharp recess.
Also attach a pic of a most useful book for you tinkerers to study. Still hope to be able to compare notes with other ''Saito-tinkereres'' out there....Cheers/Harald

I just ordered a copy of "A Guide to Saito Model 4 Strokes".

I am in the process of converting a neglected FA 150 into a "Super 180".

I plan to re-use the FA 150 case opened up to accept a new FA 180 jug, the FA 150 back plate milled down to the proper depth, the FA 150 cam, rocker brackets, cam housing, rocker arms, pushrods, pushrod covers, rocker covers & screws.

The case will be clearanced for the longer stroke, the intake manifold will be opened up to match the bigger FA 180 carb & an aluminum "stroker plate" will be fabricated to raise the cylinder base on the shorter FA 150 case. The stroker plate should yield stock CR @ about .045". I plan to reduce the thckness of the stroker plate to yield .008" (or less) head deck to piston crown clearance to increase CR.

What would be the minimal head deck to piston crown clearance?

On a 4" bore/stroke automobile engine, it's about .035" I figure W/1/4 the bore/stroke, 1/4 the miniumal clearance (.008") would be sufficient.

The engine will be run on RCEXL Electronic ignition so detonation should not be a problem.

I am ordering a new FA180 crank, conrod, piston, ring, bearings, BK cylinder, valves, valve springs/keeppers, tappets & carburetor.

It's going to cost me nearly as much as a new FA 180, about $400, but I beleve that I can make a lot more HP W/the increased CR running on EI.
Old 03-24-2012, 06:49 PM
  #59  
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Default RE: increasing compression on Saito 4S..!?

.020"
Old 03-24-2012, 09:47 PM
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Default RE: increasing compression on Saito 4S..!?

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.
Old 03-25-2012, 12:57 AM
  #61  
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Default RE: increasing compression on Saito 4S..!?

ORIGINAL: canardlover
Hello again, another update on the Saito CR increase and some more ''swiss cheesing''.. Recently bought a Saito .72 GK in good shape and as usual I could not resist to take it apart for a closer inspection. Everything was in good order except that it was equipped with the early plastic rear crankcase cover which is rather flimsy. So I bought a new reinforced cover and gave my usual ''swiss cheese'' treatment and milling of the crankcase to take off 0.8mm for an increase in CR.
This time I went a bit further in my lightening of the conrod. I drilled four holes each 4.2mm dia. which is more than ever before..[X(]....!! See pic of the setup and wish me luck, testing it very soon...Thank you..!
As far as the conrod holes are concerned,
don't you think that you threw away some of the stifness and rigidity;
Old 03-25-2012, 06:10 AM
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Default RE: increasing compression on Saito 4S..!?

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.

Old 03-25-2012, 06:29 AM
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Default RE: increasing compression on Saito 4S..!?

ORIGINAL: w8ye

.020''

That sounds like a lot for such small dimensions & the tight tolerances of these engines.Remember we are talking about cold clearances here & the case/cylinder assembly will expand a lot more than the rod/piston increasing clearance as the engine warms up. I could see .020" for VTP, but quench hieght?

I ran a Gen II 5.7 Hemi in a 2006 Dodge Daytona on 93 octane unleaded @ .035 quench hieght & .050 PTV clearance on the intake valve. The head decks were milled .030" ti increase CR from 9.7:1 to 10.4:1. The Saito combustion chamber shape is very similar to the Gen III Chrysler Hemi. i would think that similar characteristics would apply, to a point.

The car was very reliable & got 2 MPG better fuel ecomomy on the hi-way making about 50% more HP than stock. (426 RWHP cvompared to about 280 RWHP average stock)

The passes in the following clip were run @ 4250# all up weight.

[youtube]http://www.youtube.com/watch?v=T-Sbz2Etl_A[/youtube]

The closer you can run the piston crown to the head deck, the more CR that can be used W/O detonation. It's called "quench". The air being squeezed across the top of the piston/bottom of the head deck as it is forced into the central combustion chamber cools the head/piston crown surfaces reducing detonation.

Old 03-25-2012, 06:36 AM
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Default RE: increasing compression on Saito 4S..!?


ORIGINAL: canardlover

Hi again all engine tinkerers..!

2)Overall it seems that milling the crankcase does not increase power much but the engine certainly runs better on 0% nitro which was my goal from the outset.


Introduce a timed spark ignition event to allow additional tuning parametres & I think you would see more benefit.
Old 03-25-2012, 11:13 AM
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Default RE: increasing compression on Saito 4S..!?

ORIGINAL: SrTelemaster150


ORIGINAL: canardlover

Hi again all engine tinkerers..!

2)Overall it seems that milling the crankcase does not increase power much but the engine certainly runs better on 0% nitro which was my goal from the outset.


Introduce a timed spark ignition event to allow additional tuning parametres & I think you would see more benefit.
Hi again folks and here are some good news for you:
1) The newly treated .72 engine runs very nicely and I have found out how to measure vibration - see pic - by sitting on the test stand I have found out that my butt is indeed a very good vibration sensor...
2) For the first time I have achieved a really marked increase in power with this modification. We(HB and NL) just ran three engines in a row in my "vibration metering test rig" using 7% nitro, a 13 x 8 prop and an OS F plug. Highest steady full bore rpm and lowest stable idle rpm were recorded and the results were as follows:

a)Saito.82 stock(NL) 9,400/2,400
b)Saito.82 GK stock(HB) 9,500/2,700
c)Saito.72 GK modded as above 9,900/2,700

and I can tell you that the modded .72 runs so much nicer....than the two stock engines. Much less vibration and we both agreed that the modded engine also had a snappier throttle response.
Remains to be seen if the holed conrod will hold together over time.....it is now mounted into my Kelly F1 Racer to prove its "punch" and durability....
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Old 03-25-2012, 11:54 AM
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Default RE: increasing compression on Saito 4S..!?

Hi SrTelemaster......I am so pleased to get respons from another "tinkerer"..Please keep us posted on more progress.Thank you..!
Regarding the use of E85 I have tried that also but discontinued for two reasons: SMELL and SAFETY:
http://www.rcuniverse.com/forum/m_32...tm.htm#3219478

..if you chose to continue with E85 make sure you have a good amout of lubricating oil in the fuel - including some castor - since you will screw in the carb needle quite a lot as compared to methanol fuel and also your engine will run hotter.
One brazilian guy commented in the link above (post #15) that going to pure ethanol would be an alternative to E85 and that would also get rid of both the smell and safety issues.
Could you please give more details on your spark setup..Thanks..
Good luck and keep us posted...Cheers..
Old 03-25-2012, 12:32 PM
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Default RE: increasing compression on Saito 4S..!?


ORIGINAL: canardlover


Hi again folks and here are some good news for you:
1) The newly treated .72 engine runs very nicely and I have found out how to measure vibration - see pic - by sitting on the test stand I have found out that my butt is indeed a very good vibration sensor...
That's by the seat of your pants for sure
Old 03-25-2012, 03:56 PM
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Default RE: increasing compression on Saito 4S..!?


ORIGINAL: canardlover

To any tinkerer it may concern: in case you tinker with a Saito AAC engine I will hereby issue a warning. If you push the piston/ring/conrod assembly to far into the cylinder bore while assembling an engine you may hear a distinct click..
If that happens the piston ring has snapped open into a sharp recess at the top of the cylinder bore and you are TOTALLY STUCK....[:@]......!(see pic)
It happened to me and the only solution appears to be brute force, in my case destroying both piston crown and ring in the process. So be warned about this but I hope it will not stop you from tinkering. ABC engines I have dismantled do NOT have this sharp recess.
Also attach a pic of a most useful book for you tinkerers to study. Still hope to be able to compare notes with other "Saito-tinkereres" out there....Cheers/Harald
canardlover, thanks for a very interesting thread.

ref the dreaded click, as a young man I did this with a full size Lycoming piston/cylinder assy, took me a few hours to drill the piston out and save the cylinder, and a few months to get over the embarressment!.

Keep up the good work.

John

Old 03-26-2012, 07:32 AM
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ORIGINAL: Kostas1

ORIGINAL: canardlover
Hello again, another update on the Saito CR increase and some more ''swiss cheesing''.. Recently bought a Saito .72 GK in good shape and as usual I could not resist to take it apart for a closer inspection. Everything was in good order except that it was equipped with the early plastic rear crankcase cover which is rather flimsy. So I bought a new reinforced cover and gave my usual ''swiss cheese'' treatment and milling of the crankcase to take off 0.8mm for an increase in CR.
This time I went a bit further in my lightening of the conrod. I drilled four holes each 4.2mm dia. which is more than ever before..[X(]....!! See pic of the setup and wish me luck, testing it very soon...Thank you..!
As far as the conrod holes are concerned,
don't you think that you threw away some of the stifness and rigidity;
Kostas, you are absolutely correct that both stiffness and rigidity must suffer when you take away material from the conrod like this. However, I think the gains in power and sweet running is worth the risk of a potential failure. The more "classical" way of lightening a conrod is to make it into an I-beam by milling rather than drilling. See three examples where the original weight is reduced to 90%(Enya.60 4S) and 85%(Saito.56) and then the Saito.72 GK conrod at 83% after the much simpler drilling excersize. The material in these conrods is so very hard that my simple milling equipment can hardly cope with it - thus my risktaking to just drill them out.
I can honestly say that I was a bit nervous when I first fired up this Saito.72 GK and gave it full bore....[X(]...! Well, worst case would be that the broken conrod would poke a hole in the crankcase...[:@]..but second hand glow engines are cheap these days.... OK, a dead stick landing may be added to this scenario....[:'(]...but then at least I will know for sure that 4 x 4.2mm is too much and back off a bit next time(or buy a better milling machine..)
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Old 03-26-2012, 11:56 AM
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Default RE: increasing compression on Saito 4S..!?

Sr tele are you telling us you gained 146 RWHP just by raising your compression by .7 tenths of a point. I DO NOT believe that. I bet you changed the cam, rocker ratio, air intake, filter and exhaust to get that.

426 RWHP is about 500 at the flywheel.


Old 03-26-2012, 03:51 PM
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Default RE: increasing compression on Saito 4S..!?

ORIGINAL: airraptor

Sr tele are you telling us you gained 146 RWHP just by raising your compression by .7 tenths of a point. I DO NOT believe that. I bet you changed the cam, rocker ratio, air intake, filter and exhaust to get that.

426 RWHP is about 500 at the flywheel.



Engine mods (stock rotating assembly): 5.7 Mopar Performance (2.55" IN/1.60" EX, 330 CFM @ .600 lift) Heads milled .030", stock rocker arms, custom grind 1 off Crower cam (later offered as available grind) Mopar Performance long tube headers/high flow cats, 6.1 intake manifold port matched W/phenolic spacers, stock TB, AFE Stage II CAI, Billy Boat 3" SS cat-back, Predator CMR tune by Hemi Tuner.

Mods to put HP to the ground: M&H Racemaster 325 45R X 17" drag radials, Pro-Torque 2800 stall convertor, 8.8" Ford IRS center section W/Detroit Tru-Trac 3.23 ratio. (4.55 FDR in 3rdb gear)

The cam grind still allowed MDS (4-cylinder operation @ light load) & the car was very well mannered. Cranking cylinder pressure was 235 psi.

Here the car a little later that day W/a 125HP shot of nitrous that ran out @ the traps costing me .1-.2 ET & 1-2 MPH trap speed.

Ran 11.306 @ 121.87 MPH

[youtube]http://www.youtube.com/watch?v=KhG0KlXEOnU[/youtube]
Old 03-29-2012, 02:48 PM
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Default RE: increasing compression on Saito 4S..!?

Nice work on that .72!
Old 03-30-2012, 02:15 AM
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Default RE: increasing compression on Saito 4S..!?


ORIGINAL: RVM

Nice work on that .72!
YES, and next in line is my .82 for a similar treatment. RVM, how are you doing with your .82..??
BTW, I can tell you all that I have measured the CR of this .72 GK and with a headspace of 0.95mL it has a calculated CR=13.4.......! Hey downunder are you still with us..??!!..close enough to what you recommend is it not..?..
Old 03-30-2012, 06:18 AM
  #74  
SrTelemaster150
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Default RE: increasing compression on Saito 4S..!?


ORIGINAL: canardlover


ORIGINAL: RVM

Nice work on that .72!
YES, and next in line is my .82 for a similar treatment. RVM, how are you doing with your .82..??
BTW, I can tell you all that I have measured the CR of this .72 GK and with a headspace of 0.95mL it has a calculated CR=13.4.......! Hey downunder are you still with us..??!!..close enough to what you recommend is it not..?..

Do you have an opinion on what the minimal "quench hieght" (piston to head deck clearance) would be an a Saito FA 180 single?

I'm thinking about .009" since .035" is the acceptable minimum on a 3.5" stroke automotive V8 engine.
Old 04-01-2012, 07:26 AM
  #75  
canardlover
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Default RE: increasing compression on Saito 4S..!?

ORIGINAL: SrTelemaster150


ORIGINAL: canardlover


ORIGINAL: RVM

Nice work on that .72!
YES, and next in line is my .82 for a similar treatment. RVM, how are you doing with your .82..??
BTW, I can tell you all that I have measured the CR of this .72 GK and with a headspace of 0.95mL it has a calculated CR=13.4.......! Hey downunder are you still with us..??!!..close enough to what you recommend is it not..?..

Do you have an opinion on what the minimal ''quench hieght'' (piston to head deck clearance) would be an a Saito FA 180 single?

I'm thinking about .009'' since .035'' is the acceptable minimum on a 3.5'' stroke automotive V8 engine.
Hi SrTele, interesting that you bring up the "quench height" issue - and now I assume you refer to the "squish band" functionality more commonly used for glow engines. I have so far concentrated on getting the CR right but when you lower the cylinder/head assy the "squish band" in the Saito engines will narrow from well over 1mm down to zero when the glow plug will hit the piston crown.(see attached pic of Saito .56 with OS F plug mounted)
At > 1mm the squish band effect is certainly negligible but taking off from 0.8 up to 1.3mm on the small/mid block Saitos the squish band should now really come into effect......GREAT..!
Extrapolating from the 2s arena where "squish bands" are standard procedure I believe our Saitos 4S should fall in the same bracket. So I think w8ye is within our ball park when he suggests 0.020" but I agree with you that on these smaller engines we could probably go down further to say 0.010" or 0.25mm.
I have not seen much written about 4S glow engine "squish band" heights but the term is mentioned in the Saito book by G.C.Rise but no heights are given. Same thing with Bill Robisons "sticky" Saito notes, no mention of "squish bands" that I could find.
Hey downunder (or others out there)....are you still around..??...I know you have been tinkering a lot with these things - please share your knowledge...THANK YOU..!
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