canardlover

Hi guys and thanks for encouraging comments.
Runtime?- the piston you see served in my Sig Cougar for the entire last season=several hours and still runs fine.
Lifters:..yes indeed I wish I could hollow out the tiny Saito lifter but that is beyond my ability. The Enya lifter has 6mm dia. but Saito lifters are only 4mm dia. - way too small to hollow for me..
[]
Money:...not expensive at all since I rarely buy a new engine but rather buy second hand engines and fix them up.Have a box of spare parts from broken engines sometimes given for free to me..
Takes some time - yes but that is my way of relaxing rather than playing golf...[:@]
Vibration?...yep, sure thing they purr like kittens but that of course is very subjective and I have no means to measure vibration objectively.
Performance?...good point but the problem is to make a relevant comparison since they run on different fuels. Maybe running std. engine on 10% nitro and modified engine on 0% nitro...??....or both on 5%...?? Will try to make a comparison since I have Saito.56 engines with no mods (0mm) and with 1.0mm, 1.2mm and 1.3mm shaved from crankcase. Even so they differ by being more or less worn but I will try later.

Sold one of my old Saito.65 engines to a guy in the club and he has run it for three entire seasons without mishap but last week it was returned to me for fitting a new main bearing. See pics on that one attached......Cheers/Harald

RVM

I wish you lived in the US. I'd come to whereever you fly, check out your engines, see how they run, and if I liked them I'd be willing to pay to have these mods done.

RVM

Canardlover, any updates to your testing with the increased compression?

canardlover

RVM - nope not yet I´m just re-assembling some engines at the moment and there is still snow covering my test stand...BRRRRR.....bu by mid April it should happen....Cheers/Harald

RVM

Which engine is that on the stand and what prop is that?

canardlover

Hi RVM - the engine with the yellow prop is one of my .56 engines - not sure which one. The one with the red wide blade Robbe Dynamic 12x6 prop is the same old faithful .65 engine from which you see the internals in post #26 photos above. The cardboard box contains a receiver and servo for remote throttle control, an IGS onboard glow unit and Blå Mocca is a swedish coffee brand of excellent quality...=))...!
Attach a pic of a more exotic RCV.60 engine which I have not yet tampered with but probably will later when it is time for an overhaul of it....Cheers/Harald

RVM

I'm not sure if you'll hav an answer for this, but I'm thinking about milling down the crankcase on my Saito .82a to increase the compression. I want to maximize power output with 15%-25% nitro. About how much should I take it down? How well would a shim work if it was too much?

canardlover

RVM - before doing anything please try to measure CR first on the engine by filling the "head-space" with oil holding the piston at TDC and both valves closed. Fill to the lower part of the glow plug thread and then make your calculation.
My guess is that your engine is already optimised for the nitro contents you mention - generally products are made primarily for the US market and you are "nitro thirsty" over there....
I have no experience with a shim or gasket under the cylinder/head unit but assume it should be no problem to add one if need be....Cheers/Harald

RVM

Yeah I would definitely measure first.

I know this engine can run 40% nitro safely, so I figure there is room to increase compression a bit to work with 15%-25% fuel.

Sport_Pilot

IMO the chart on this link has the compression ratio listed a bit high all the way up and down for our engines, but the rate or differance should be about the same, if you have a starting point.

http://www.turbofast.com.au/racefuel5.html

RVM

According to that chart I should be able to increase to compression ratio to almost 14:1. Of course, the oil in the fuel will contribute to the compression, so that should be taken into account.

Great link!

downunder

The volume of the oil carried in with the fuel is totally negligible and far smaller than any accuracy you can measure the combustion chamber volume to. With your Saito the oil volume will be somewhere close to .001cc per compression stroke.

Flyer95

My Feedback: (1)

I have always felt like adding oil and specially castor oil to the fuel increases the compresion a whole lot. One example was the big Super Tiger G4500 made to run on 8-10% castor oil and according to the European distributor when run on FAI 80/20 castor oil and methanol there was a few wrist pin failures due to to high compression.
When running high oil fuel in my Super tigre G3250 adding 2-3 head shims made the detonation go away and the engine ran like using 10% oil without the extra head gaskets but now it did smoke a whole lot more [sm=thumbs_up.gif][sm=lol.gif]

canardlover

Howdy Saito lovers, here is another update from Sweden. After fitting the new main bearing in the Saito.65 (post#26 above) it was assembled and tested. It was clear that the engine by now had become a bit "loose" in the conrod big end but it still ran nicely without excessive noise. My friend who owns the engine mounted it in his UltraSport and up it went the other day with myself at the sticks. All went well for a while but then suddenly....SKRUNKK...!...the engine came to a sudden stop and I(we) thought:...OK, that´s it now we have at last reached the limit for "swiss-cheesing" and the owner muttered something unprintable with a clear address to me........!
Taking it apart revealed that - sure thing - it was the conrod that broke as we both expected but not exactly where we(he) thought....[]....!...which restored some of my battered ego.
Flyer95, do you think we could cooperate to produce a new conrod to thÃ*s engine being about 1mm longer than stock...??...will call you later about this since that would take CR up from current 11.1/1.........sack time here now.....Cheers/Harald

RVM

How high do you intend to take the compression?

Funny that the places you lightened the part didn't fail, but rather a part you had not modified. I imagine that most likely the failure was due to the "looseness" of the conrod, and thus a stress failure on that part.

canardlover

RVM, yes it was good to see that it broke at the big end and not along one of the "cheese holes"...!
I still intend to reach CR 13.5 as proposed by downunder et al. but have so far only obtained CR=12.5 on my most modified engine. This .56 has the "skeleton" piston and other "guts" as shown in post #22 above and has been milled -1.3mm from the case. I have flown it twice in my Sig Cougar just recently and this engine runs better than ever before so I intend to continue in incremental steps towards 13.5 as time permits.
I´m still not sure if CR 13.5 is possible in a Saito.56 without parts hitting each other....downunder, can you chip in here from your experience/sources..??
As an example we modified an old Saito.40 by arbitrarily milling -1.0mm and that turned out to be exactly what was possible with its piston just about hitting the glow plug. CR on that .40 increased from 7.1 to 9.3 in the process but we have not yet had the time to run it.
....anyway CR research continues.........RVM, how are you doing with your .82...??....Cheers/Harald

Hobbsy

My Feedback: (102)

Robert, rather than destroying .82s seeking more power, why not just get a 1.00.

RVM

I'm not destroying my .82s lol. I haven't done a thing to any of them. This was for a future idea to do for fun. The last one had plenty of power for the plane it was in. I wasn't even really leaning it all that much.

That said, the reason why is simple and applies to any engine. The higher the power:weight, the better. Therefore, the more power you can get out of a smaller engine, the better. Why get a V8 when you can do the same thing with an I4 and have less weight? This is especially important in the smaller models that I fly. In a 40% plane, a few ounces here or there won't matter. In a .60 size plane, 3 or 4 ounces can have a noticeable effect on flight performance.

Besides, I love tinkering with things. I would actually like to build my own engines one day. I just gotta get those damned milling machines and a lathe...

RVM

According to a link above, I think you can use a 13.5 CR and still run 25% nitro or so. That means if you use less nitro, you can get an even higher CR. I don't know that the engine itself will allow it due to the valves. 13.5 would still be very nice.

I bet you can really feel it when turning the engine over by hand.

downunder

The limiting thing with any 4 stroke will be the valve clearance from the head and this is going to vary with different engines depending on design so some careful measuring will need to be done first. The critical part is the overlap period and in full size engines I believe around .060" is considered a minimum clearance. With model 4 strokes it would be much smaller than that and if I were to guess I'd say .010" would be my limit. Allowance has to be made for the fact that as the piston slows coming into the overlap period then the rod is doing all the work of slowing the piston to a stop at TDC so all the bearing clearances stack up plus the rod will stretch slightly (after all, the piston has to slow down at a rate of 2000G's or so). This decelleration can rip off the ends from a rod sometimes. Now where have I seen a photo of a rod like that?

canardlover

downunder - very good points about 4S clearance and this also means that you can only approximately measure the true clearance by rotating the engine by hand with clay dimples on top of the piston.My crude method so far.
I must admit that I was a bit surprised to find the piston crown hitting the glow plug in the Saito.40 well before I could sense any contact between piston and valve(s)..[X(]
Well, Saito heads differ in shape with the .40, .50 and .56 engines being true "hemis" while the .65 and .72 engines have a more complicated shape with valves recessed. So maybe different Saitos have also different limitations on what will hit what if you mill too much....?
Eventually it turns out that Saitos are NOT the most suitable engines to achieve higher CR but rather the wedge shaped heads as used on OS, Enya, ASP and Magnum engines. This is also what the diesel guys work on in another thread.

RVM - yes indeed tinkering is fun and sometimes helpful but I think Hobbsy has a good point regarding your .82. I doubt that CR=13.5 can be combined with 20% nitro without detonation so unless you have a very clear objective on what to achieve leave it alone.
Buy yourself a couple of dirt cheap worn out or crashed engines, take them all apart and try to assemble one functioning engine incorporating simple mods you can perform with a press drill, a Dremel and a grinder. Leave the lathe and the milling machine till later.
This is the way I do it and makes it all much more relaxed if there is a mishap. Also try to obtain the booklet (by Mr.Rice?) on Saito engine maintenance which is really helpful.
RVM I do NOT say this to discourage you from tinkering - just the opposite......but do not start out with a well functioning engine which you need for flying.
.....sack time again....Cheers/Harald

RVM

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

downunder

One way to check valve clearances at different piston heights is to simply push the valve down against the spring and see how much it moves. With an angled valve you'd have to work out the geometry to get an accurate figure though and a DTI would be rather helpful too . Or thinking about it, push the valve down by the spring cap and use feeler guages to measure the tappet clearance.

Using 20% nitro with a 13.5:1 compression is a recipe for disaster. Nitro doesn't tolerate much compression before it detonates and probably around 10:1 would be the limit for 20% nitro. Pure nitro is limited to 6:1. Theoretically methanol will tolerate up to 17:1 but you'd need a very cold plug to keep the ignition timing in check and then it might not like to idle. The ideal would be 17:1 and spark ignition .

RVM

I could have sworn I saw where you could run 20% nitro in methanol fuel at 13.5:1. I could be wrong though. Let me go double check.

Hobbsy

My Feedback: (102)

I have an old Saito .80 with 15.6 to 1 compression and an early 1.50 with 14.4 to 1, both are capable of removing a chicken stick from your hand and sending it to the neighbors. They both command due respect and rattle at peak on 15% nitro.