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HelicopterEngines Plugs Mufflers Fuel › YS 91 SR (long stroke)
09-12-2007 09:12 AM  10 years agoPost 1
steverobertsuk

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London, England

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Guys

Just managed to get a Long stoke YS 91 from Motors & Rotors with the new Hatori USA SB-19 muffler.

Has anyone been running one for any length in time to see any difference between the new long stroke and the ST4?

Steve

Team JR, Motors & Rotors, OptiPower

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09-12-2007 01:00 PM  10 years agoPost 2
bparro

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indianapolis,in

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there is a huge difference! Alot more power

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09-12-2007 01:51 PM  10 years agoPost 3
BJames111

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San Diego,​California

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just got one myself. Quite a bit more power.

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09-12-2007 03:08 PM  10 years agoPost 4
steverobertsuk

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London, England

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Sweet

Had a few tank through it now but cant wait for it to really start to howl!

Has anyone tried it with the SB16 & 19 to compair?

Steve

Team JR, Motors & Rotors, OptiPower

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09-12-2007 03:29 PM  10 years agoPost 5
bparro

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indianapolis,in

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I am using an MP5 on mine. The sb16 is not very good on it from what I have seen. SB-19 or MP5 are the only good choices really.

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09-12-2007 06:29 PM  10 years agoPost 6
Chuckie

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Crofton Maryland

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With the SB-16 the SR is smooth and has ok power, more power than the ST4. The SB-18 bumps the power and torque by quite a bit on both the ST4 and SR motors. The SB-19 adds a bunch of torque, a lot or torque for sure, night and day torque add, don't want to give up the 19 for nothing torque. Get the idea

I'd suggest running the SR motor at 15,300 to 15,700. Above that and you just shorten the life of the motor.

Charles

Please stand by for faster service!

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09-12-2007 06:36 PM  10 years agoPost 7
steverobertsuk

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London, England

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Cool thanks

Need to burn more fuel I'm thinking!

Steve

Team JR, Motors & Rotors, OptiPower

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09-13-2007 10:38 AM  10 years agoPost 8
Jim-bob

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Little Hocking OH​USA

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Would the SB-19 be a better option for the ST-4 as well??

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09-13-2007 12:16 PM  10 years agoPost 9
Chuckie

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Crofton Maryland

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Would the SB-19 be a better option for the ST-4 as well??
My comments in the previous post are from observations in flight tests. I have not tried the ST4 with the 19 but my guess is it would work, however, I don't know where the power band would be or what rpm is ideal/max. Also, the SB16 makes both motors run smooth and going to the 18 or 19 increases power and torque (in the SR) but the cost is loss of smoothness. The 19 tuning does push a lot of fresh fuel/air back into the motor (scavenge) and I think that is why the SR looses smoothness on the 19 but that is how it makes power/torque. The issue for the 19 on the ST4 would be heat build up at high rpms.

For scale and new flyers I don't think the power increase is worth the loss of smoothness or risk of heat build up.

My friend who is flying the ST4 has my old 18 so I'm sure I can try the 19. I don't know when I'll meet up him next, probably not this weekend.

Charles

Please stand by for faster service!

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09-13-2007 01:44 PM  10 years agoPost 10
BJames111

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San Diego,​California

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I got my 19 before I got the sr. I tried the 19 on my st4, and it seemed to work really well. Kinda raspy sounding, but the power was pretty good.

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