RhyanO

Hello all,
I have a question about my Saito .82a, engine.
The problem seems to be that this engine does not seem to be turning the RPMs that it should (only 8700) with a given size prop (14x6).
I broke the engine in as specified about 3/4 gallon.
I have run about another gallon through it since the breaking in stage.
I have checked the valve gap clearance at TDC and it is within spec.
Im running Byrons 15% fuel wiht 18% oil content (Castor)
Glow plug is a new OSF type plug
The engine seems to have plenty of compression, and runs very smoothly with no misses.
Transition is terriffic.
RPMs stay constant when glow plug igniter is removed.

From posts I have read on here this engine should be able to turn this prop at least 9500 RPM, and im only getting 8700 RPM max.

Im curious as to what insight others who are more experienced that I am, as to their thoughts on this?

Thanks much,
Ryan

bckyrdbshr

My Feedback: (35)

A bunch of people use the 30% nitro heli fuel in the Saito's, maybe try a little more nitro..maybe you need to try to re-tune it better, or maybe it just needs a little more break in time..

wcmorrison

My Feedback: (2)

Me thinks you have too much prop. Try a 13 X 6 or 12 X 8. I use 14 X 6s on .91, Saito .91 and Magnum .91.

You did not say how new or old your Saito was. A big prop on a very new engine will not turn up til the engine is broken in.

As I said, I would step down my expectations on RPM for such a big prop on a smaller sized engine.

I bet it does not accelerate very fast either.

Cheers,

Chip

Jack Hyde

My Feedback: (1)

I made a plot of rpm reported in the Tach Readings area of RCU. I use "Prop Select" to compute HP vs RPM for various props then plot reported measured rpms on the curves. The HP values are used in relative comparisons. Like a 14x6 requires 34% more power to run at 10,000 rpm than a 13x6 at 10,000 rpm.The 2 props need the same power for 10,000 rpm for the 14x6 and 11,000 for the 13x6. I found 7 reports of rpm tached for the Saito 82 with a 14x6 prop. The lowest was 9200 rpm , the highest 10,200. This was running 15% nitro.No one reported taching a 13x6 but the curves indicate it should turn more than 11,000 rpm on the ground, which is more than I want to run.. Most people get a little less than 10,000 with the Saito 82 on a 14x6.
At 8700 rpm you are getting about 30 % less power than most Saito 82's produce at 10,000 rpm.

SO your Saito is not running up to norm. You can get 10% more power by jacking up the nitro but you will at best be getting what everyone else gets on 15%. I don't know why you are getting low power - too rich, valve lash, glow plug, bad fuel???

speedster 1919

My Feedback: (3)

First off RYAN. Some people fudge their numbers and most are peak RPM and not rich 300-500 to make flyable. Not all 14x6 props are equal and can vary many hundreds of RPM. Plus it sounds like your not quit broke in for true numbers.

rc-sport

My Feedback: (12)

14x6 is to much prop. Go to a 13x6 APC.

Jack Hyde

My Feedback: (1)

OK guys lets have some numbers. How many RPM are you getting with a 13x6 on a Saito 82? I figure you will be pushing 11,000 rpm. I can't find one measured rpm for a Saito 82 with a 13x6. Plenty of guys report tach numbers for a 14x6.

RhyanO

Thank you all for the feedback so far.... keep it comming I appreciate it.

I adjusted the valve gap clearance and found the intake clearance was abit wide (no resistance on feeler gauge that is supplied with the Saito 82). I re-adjusted this gap so it is back in spec.
Can the intake valve having .004" too much gap have this much of an effect on engine power? Just curious as I havent tried runnign the engine again yet.

I beleive the plug is in good shape since the engine does not loose any RPM when I remove the glow plug igniter.
I also believe the fuel is okay since it is fresh and I take care to store it properly.

Im still puzzled as to why this is happening as the last time I ran the engine last year I got 9200 RPM richened up from peak, and now this year the engine struggles to reach 8700.

Im going to try and take the needle valve out and clean out the carb. just to make sure nothing is plugged in there restricting the fuel flow.

Any other ideas?

Ryan

blw

My Feedback: (3)

Is the engine running smoothly without sags, surges, or deadsticks?

Did you peak the high speed needle valve before you set your low speed needle valve? The low speed is tricky to set the first time you try it on a Saito, and is the cause of many problems.

Probably the easiest and cheapest thing to do is replace the glow plug and see what happens.

RhyanO

The engine runs very nicely no misses, sags, surges or deadsticks etc.

I did set the High speed needle valve with my tach and richened it out 400 rpm.
The low end has also been adjusted correctly, for a strong smooth transition.

The problem seems to be that the engine just does not turn the RPM that it should.

Ryan

RhyanO

The engine runs very nicely no misses, sags, surges or deadsticks etc.

I did set the High speed needle valve with my tach and richened it out 400 rpm.
The low end has also been adjusted correctly, for a strong smooth transition.

The problem seems to be that the engine just does not turn the RPM that it should.

Ryan

Hobbsy

My Feedback: (102)

Ryan, I'll run my .82 sometime today using an APC 14x6 and PowerMaster 15% fuel and see what I get.

speedster 1919

My Feedback: (3)

[quote]ORIGINAL: RhyanO

Can the intake valve having .004" too much gap have this much of an effect on engine power? Just curious as I havent tried runnign the engine again yet.

I beleive the plug is in good shape since the engine does not loose any RPM when I remove the glow plug igniter.

RHYAN Did you switch brand and type of prop from last tear? More power is result in minimum valve clearence as opposed to the widest in spec clearence. A weak glow plug will affect top end performance even though you don't see a problem on the low end.

RhyanO

Torque Wrench,
Let me know what you get for RPM with your 14x6 on 15% fuel. That will at least give me something to compare my engine to. Please provide peak RPM then what RPM you richened it out to for flying.

Im currently using a 14x6 prop that I believe is a wooden "Zinger" prop.

I will try a new glow plug also just to rule that out.

Thanks all,
Ryan

Hobbsy

My Feedback: (102)

Ryan, here are my unfudged numbers

APC 14x6
PM 15%
RPM==peaked=9,570, richened to 9,400, this was the rpm at the beginnig of a 16oz tank, it would still make the same rpm at the end of the tank. The plug was a new GloDevil 4s.

MyWay

Nothing wrong with your engine. As stated previously, your prop is to big. A wood 14x6 will run as much as 1000 rpm less than a apc or master airscrew 14x6. If you want to use a wooden prop try a 13x6.

Ernie Misner

The tighter the better on the valves, while still maintaining some clearance. These glow 4-strokes do not loose the clearance as they heat up like large gasoline engines do. Not that this is your problem, but try .0015 or so for maximum duration.

Ernie

RhyanO

Torque Wrench,
What type of prop were you using... just curious. Iam using a wooden Zinger type prop.

Ernie, thanks for the tip on the valve gap clearances, I will have to pick up a set of feeler gauges so I have one that is the thickness that you specified.

Ryan

Ernie Misner

Ryan, I just use the stock, supplied guage, but set it so that there is a tiny bit of drag on it. Double check that there IS clearance once it is removed though. Bill R. reverts to the old cigarette pack celophane trick which is about .001.

Ernie

Hobbsy

My Feedback: (102)

It is an APC

blw

My Feedback: (3)

Changing from the Zinger to an APC 14x6 is a good idea.

Sport_Pilot

If a prop is turning 1000 RPM less, then most likely it is doing more work, that is pushing more air. They can slow down if they have more tip drag or poorly shaped airfoils, but I doubt that is 1000 RPM. My experiance with Zinger and MAS wooden props is that you often get the same or better performance if you pitch them 1" less or use 1" less diameter.

There was an article in MA, Joe Wagner's article I think, where he smoothed out the leading edge and the airfoil near the hub, and got several hundred less RPM out of it. However, the engine performed better with it. He explained it by comparing it to a vacume cleaner. When you cut off the airflow the vacume motor and fan speeds up because you took the load of the motor.

AHPowelson

My Feedback: (37)

That's your problem right there! My .82 HATES wood 14x6's for some reason. It would never turn one over 9k. I currently run a Master Airscrew K-Series 14x6 and it turns it at 10,500 RPM on 30% nitro. I'm not a fan of the APC 14x6 as it's very heavy and spools slowly. The APC 14x5N is an awesome prop for the .82 as well - instant spool and upper 10k RPM.

Get rid of that Zinger!!!

Hobbsy

My Feedback: (102)

AH, I'm not an APC fan either, I only have a few for testing purposes.

AHPowelson

My Feedback: (37)

I prefer APC props for a lot of applications; their 14x6 is just too heavy, though. I've had really good results with the MA 14x6 so I tried a MA 16x6 on my 1.25 and was disappointed. The APC 16x6 was much better, albeit heavier..