RE: GAS Saito

RE: GAS Saito
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RE: GAS Saito - 7/17/2008 10:07:19 PM

kiosk

Posts: 146
Joined: 2/12/2008
From: , FL, USA
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well I be darn man, I think you are right on, it has to be backwards one tooth because it has tons of torque but lost RPM, which is what an article says i googled, no wonder RPM didnt change when going from 18x10 to 19x8!!

Your Saito engine will tollerate a slight mis-timing of PLUS or MINUS one tooth on the camshaft without adverse effects. If it's minus one tooth, you'll get a little more torque. If it's plus one tooth you'll see a little more RPM but you'll have to lower your prop pitch since you will loose some torque. It's BEST to have the cam timed properly!

< Message edited by kiosk -- 7/17/2008 10:40:39 PM >

(in reply to Jezmo)

Post #: 301

RE: GAS Saito - 7/18/2008 8:05:54 AM

Ed Cregger

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Joined: 1/31/2002
From: Ringgold, GA, USA
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quote:

ORIGINAL: kiosk

yes thats first thing I ran to and I am way off. with an 18x10 am suppose be running like 7550 and 19x8 around 8000, and i clearly remember when I first got it running 8500 on an APC 18x8. Right now I cant get higher than 6700!!!

-

Ouch! Now I understand your concern. I hope you get it figured out.

If you haven't done so as yet, I would check the valves for proper clearance. It can make a big difference when they are loose.

Ed Cregger

_____________________________

Artisan

"Flying models since the Fifties - I'll get the hang of this yet!!!"

(in reply to kiosk)

Post #: 302

RE: GAS Saito - 7/18/2008 6:27:47 PM

kiosk

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From: , FL, USA
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ok now am p1ssed off.....I flew it this AM like this and after 1min of flight it dead sticked on me, managed to put it down ok but took out the prop. Put another prop on and no ignition, no spark.....either the sensor or ignition module went bad, which sucks so this baby is back to Horizon ASAP.

(in reply to Ed Cregger)

Post #: 303

RE: GAS Saito - 7/24/2008 4:25:42 AM

rv8pilot

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Joined: 8/23/2004
From: Boca Raton, FL, USA
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Recently bought one of these having thought for years that the idea of a quality four-stroke gasser would be great. Over the last couple days I ran it in for a total of about 40 minutes or so. Difficult to start by hand without choking, but starts ok after its wet. Hot starts are fine. Seems to run fairly smooth for a big single. Today I finally had what I felt was enough running time to go to full power. I'm using a Master Airscrew 18x8 and the engine could get no more than 7100 rpm regardless of needle settings. Max rpm occurred at about 3/4 throttle, and more throttle did nothing. Having read the posts about cam timing affecting torque and rpm, I tried an old Dynathrust (remember them?) 20x8, close enough to a Master Airscrew in shape to be comparable. It turned 7000rpm. According to the horsepower calculator on the net by Barry Hobson, an 18x8 at 7100 is using about 2hp, and a 20x8 at 7000 is using about 3hp. So what is going on here? I suspected that the cam gear timing might have been off and called Horizon and spoke to Nathan. Got his ok to tear down the top end and check/reset the cam gear (I've done this a lot as I repair these things as sideline), to make a long story short, no change in running-still 7100 on the 18x8. Now I'm thinking that it may be a fuel delivery problem in the carb. Nothing else in the fuel system is restrictive, so I'm at a loss here. Anybody want to take a shot at this. Its beginning to sound a little like the guy who got 8500 originally and now only gets 6700. (Sorry, I forgot the fellows name.)

(in reply to kiosk)

Post #: 304

RE: GAS Saito - 7/24/2008 3:27:18 PM

laryboy

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From: wilmington, MA, USA
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i too had problems starting w/o choking. had to stick my thumb into carb. i cured problem by first setting carb barrel to its fully closed position. (throttle against throttle stop ). using starter motor, gas was immediately sucked into carb. moved throttle stick to high idle, turn ignition on and bingo she starts.try switching to an apc 18/8 and see if it makes any difference. it has woked for me on other saito's but i dont know why.

(in reply to rv8pilot)

Post #: 305

RE: GAS Saito - 7/24/2008 3:35:45 PM

rv8pilot

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From: Boca Raton, FL, USA
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Laryboy, thanks for the feedback. What starter are you using to crank this bugger over? I've not had great luck with my Dynatron. Maybe I need to use a spinner instead of the prop shaft and nuts as it slips a lot. I'll try the 18x8 APC, but can't imagine it would make that much of a difference. We're talking 1500 rpm after all.

(in reply to laryboy)

Post #: 306

RE: GAS Saito - 7/24/2008 4:07:55 PM

laryboy

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From: wilmington, MA, USA
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USING A DYNATRON. trick is to make sure that throttle barrel is fully closed, not just at idle. i had a 3 cylinder saito that would only run on an apc prop. sent it back to horizon where they verified problem but had no answer except to use prop that worked best ?

(in reply to rv8pilot)

Post #: 307

RE: GAS Saito - 7/24/2008 5:50:34 PM

rv8pilot

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From: Boca Raton, FL, USA
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Laryboy,

It gets more interesting all the time, eh? Talked to Horizon this AM and the upshot is they are sending me an RA and they'll check it out. I'm holding my breath. The prop issue is odd. I have never noticed any great differences in rpms from one make to another in a given size as long as the prop is similar in blade area. A few hundred rpm one way or the other, but not an inability to run. Weird. I have the 450 radial also and have bench run it on several props, mostly in the 22x10 range, up to 24x8 and it did fine. These were all wood Zingers, I think. Well, as they say, "your mileage may vary", thanks for the info 'tho, it all adds something to the knowledge base.

(in reply to laryboy)

Post #: 308

RE: GAS Saito - 7/24/2008 5:53:48 PM

rv8pilot

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From: Boca Raton, FL, USA
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Laryboy, is your Dynatron on 12v or 24v?

(in reply to rv8pilot)

Post #: 309

RE: GAS Saito - 7/24/2008 6:51:10 PM

Ed Cregger

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From: Ringgold, GA, USA
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You, I and everyone else knows that there is no logical reason for any prop within the proper size range to cause the engine not to run, UNLESS, something about its particular size/construction cause the crankshaft to move so that the magnet and sensor are misaligned.

Ed Cregger

_____________________________

Artisan

"Flying models since the Fifties - I'll get the hang of this yet!!!"

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Post #: 310

RE: GAS Saito - 7/24/2008 8:13:57 PM

laryboy

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From: wilmington, MA, USA
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12 volt

(in reply to rv8pilot)

Post #: 311

RE: GAS Saito - 7/24/2008 11:02:01 PM

rv8pilot

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From: Boca Raton, FL, USA
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Ed,

Of course you are correct, you could probably get a .049 to turn a 24" prop once you got it going fast enough. I am stymied by these comments regarding only certain props running. (As was the guy I spoke to at Horizon) I'm quite sure I could turn a 3ft 2x4 with the FG-36, at least until it overheated. The engine doesn't care what the load is, and a spark ignition engine will keep banging away at the piston as long as the spark is being created, since it is not speed dependent as is a magneto. Obviously there are rpm ranges where the engine will run best due to cam and spark timing, and other design factors, but any prop in the range of sizes the engine likes best will run with varying degrees of efficiency.

(in reply to laryboy)

Post #: 312

RE: GAS Saito - 7/25/2008 1:03:49 AM

laryboy

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From: wilmington, MA, USA
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here is the letter i got from H.H

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(in reply to rv8pilot)

Post #: 313

RE: GAS Saito - 7/25/2008 4:52:36 AM

rv8pilot

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From: Boca Raton, FL, USA
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Laryboy, thanks for taking the trouble to post your notes from Horizon. I hope it didn't sound like I didn't believe you earlier, but it sure doesn't make any sense. I'm assuming these props were all the typical APC planform, not some oddball wide blade on the slow turner. Its interesting, I think, that he mentions getting info from Saito, but doesn't say what that may have been. They probably think were nuts over here. It might be interesting to run this information by APC and see what they have to say. They seem to know what they are doing when it comes to props (unlike some others that used to shed blades now and then). The only wild thing I can think of is some kind of harmonic vibration between that engine and that particular prop that is shutting down fuel flow. Full-scale aircraft go through very rigorous testing of propellers to rule out damaging harmonic vibration, particularly with metal props. Some certified engine/prop combinations are placarded to advise against running at a particular rpm to avoid damage. For what its worth, your mileage may vary.

(in reply to laryboy)

Post #: 314

RE: GAS Saito - 7/25/2008 11:09:40 PM