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-   -   .91 Four Stroke Readings (http://www.rcuniverse.com/forum/tachometer-readings-173/1970102-91-four-stroke-readings.html)

ptarp 07-07-2004 09:03 PM

.91 Four Stroke Readings
 
Post your .91 four stroke tach engine readings, any brand...

ASP .91
%10 Wildcat %18 oil

MA 14x6 8900
Zinger 14x5 10500

kris_762 07-11-2004 11:41 PM

RE: .91 Four Stroke Readings
 
Engine: Saito FA91
Fuel: Powermaster Heli, 15% Nitro, 20% Synthetic/Castor oil
Prop: APC 14 x 6
Max RPM: 10200
Flight RPM: 9700

hgiles 07-12-2004 08:00 AM

RE: .91 Four Stroke Readings
 
HOMEBREWER reports a THUNDER TIGER .91 FS was reported to turn an APC 14x6 at 10500 on 10%... don't know the other details. The only reason I remembered the numbers was because I wanted to buy one and researched it here first. BTW, I did buy the TT FS 91, but haven't run it yet. I am going to put it in a CMPRO/GSP Spitfire.

Killer_Matt 07-12-2004 11:43 AM

RE: .91 Four Stroke Readings
 
os .91 fs pumped
10% byrons
10..25 lb topflite 65" mustang

15 x 6 8200rpm apc "kinda slow"
14 x 6-10 7450rpm zinger this prop really loads it down on the ground but once in the air it realy picks up speed

Sport_Pilot 07-12-2004 12:04 PM

RE: .91 Four Stroke Readings
 
Thuunder Tiger .91 FS

Fuel Wildcat 15%
Prop MA 14-6 10,200
APC 14-6 10,300
With Coolpower 25% 10,600.

ptarp 07-12-2004 01:21 PM

RE: .91 Four Stroke Readings
 
Some more readings...

Engine: ASP .91
Fuel: 10% Wildcat

Prop/Tach #s:
APC 14x10 7,600 While it has a low static rpm, it gives pretty good performance in the air
Zinger 14x8 7,900
Zinger 13x10 7,900

My engine is still pretty new(about 1/2 gal.) but I'm not really impressed with my numbers yet. The only prop that will get sufficient RPM is a Zinger 14x5 @ 10,500. Anything with much pitch really loads the engine down.

ptarp 07-13-2004 03:09 PM

RE: .91 Four Stroke Readings
 
All of mine to date...

Engine : ASP .91
Fuel : Wildcat %10
Glow Plug: OS #F

APC 14x10 = 7,600
APC 12x12 = 9250*
APC 12x10 = 9500*
APC 11x12 = 9600*
Zinger 14x8 = 7,900
Zinger 14x5 = 10500
Zinger 13x10 = 7,900
MA 14x6 = 8900

Again, my engine is still breaking in, so I'm hoping my numbers will improve:)
* = New for this post

ptarp 07-13-2004 03:27 PM

RE: .91 Four Stroke Readings
 
Quote:

ORIGINAL: Sport_Pilot

Thuunder Tiger .91 FS
...
APC 14-6 10,300

This works out to be 1.8hp. The TT .91 is rated at 1.6hp. I've never known manufacturers to under-rate their products, do they? I'm just trying to figure out if my enigne is under performing, or if people are inflating their numbers a bit.[:-] Not trying to pizz anyone off, I was just curious.

futaba1024 07-13-2004 03:40 PM

RE: .91 Four Stroke Readings
 
Saito 91. Fuel 5% Nitro 10% oil (8%syn 2% castor)

13x8 APC=10200
12.5x8 bolly= 10700
Which calculates to around 1.7hp.

Sport_Pilot 07-14-2004 09:31 AM

RE: .91 Four Stroke Readings
 
How do you know the HP? From a propeller HP thrust caluclator? Seems .2 HP off is a pretty good estimate to me. Also an honest manufacture would have ratings of the AVERAGE engine, not the best or most pampered engine. But IMO TT made some changes without updating the specs. Their marketing seems off, or maybe their marketing people are just as lazy as their service people.

ptarp 07-16-2004 06:51 PM

RE: .91 Four Stroke Readings
 
Quote:

ORIGINAL: Sport_Pilot
Also an honest manufacture would have ratings of the AVERAGE engine, not the best or most pampered engine.
Well, most don't. They try anything they can to get their HP number up because so many people look at that when buying an engine.

I did use the Thrust HP program to find the HP. Again, I wasn't trying to make anyone mad, I was just curious. It doesn't seem far off at all now, because I tried an APC 14x6 Sport on my .91 and I got 9700. After my engine breaks in fully I'm hoping to get about 300rpm which would put it close to your number. No offense! :)

TT Does need to up their marketing. If their service/marketing was as good as their engines they'd be in good shape

More #s...

Engine: ASP .91
Fuel: Wildcat %10 Nitro
OS #F Plug

APC 14x6 - 9700
APC 13x8 - 9650
Zinger Pro 14x6 - 8900

Homebrewer 07-16-2004 11:52 PM

RE: .91 Four Stroke Readings
 
Yes, I was routinely getting 10,500 -10,600 k on my TT .91s but if I said it was with 10% fuel, I was mistaken. I use only 15% or 20/20 in my engines.

The point is that the TT .91 will smoke most engines in its class other than YS. Yes, its a little heavier but most airplanes I built needed the extra weight in the nose anyway.

krayzc-RCU 07-19-2004 10:35 AM

RE: .91 Four Stroke Readings
 
i am running 2-OS-91 on 15 x 4 APC i will have to tach as i have forgotten the deal[8D]

stelios 07-19-2004 10:57 AM

RE: .91 Four Stroke Readings
 
My OS FS-91 II with pump turns MA 14x6 at 9650 rpms.

Fuel is Model Technics Dynaglo 10% nitro with 14% (enriched) oil (12% synthetic + 2% castor).

Stelios

Richard L. 07-21-2004 12:03 PM

RE: .91 Four Stroke Readings
 
My OS FS-91 Surpass II with pump swings a Graupner 13.5x8 at 9.6K rpm on Powermaster 15% nitro:

http://www.whitetyphoon.com/rc/os91fs/reading1.jpg

AnthonyH 09-01-2004 05:50 PM

RE: .91 Four Stroke Readings
 
TT F91S running 10% Wildcat 18% syn/castor blend
Zinger 15x6 = 8200 rpm
Zinger Pro 14x5 = 9700 rpm

OS .91 Surpass II running 10% Wildcat 18% syn/castor blend
Zinger 15x6 = 8400 rpm
Zinger Pro 14x5 = 9500 rpm

Both engines are still breaking in and running rich. Each has about a half gallon through them.
The OS seems to like the 15" prop better than the TT.
The TT turns the 14" prop better than the OS.

I will get an APC 14x6 or maybe a 15x4W and see what I get.

windsheer 09-01-2004 07:59 PM

RE: .91 Four Stroke Readings
 
Saito 91S, Wildcat 15% 2/4 stoke fuel, Apc 14X6 prop
peek 10,500K

Sport_Pilot 09-02-2004 08:24 AM

RE: .91 Four Stroke Readings
 
Give the TT another gallon or so, its potential is not as apparent till then. If you are not getting over 10,000 with the 14-5, then something is wrong.

AnthonyH 09-03-2004 01:56 PM

RE: .91 Four Stroke Readings
 
I got an APC 14x6 and ran it yesterday. It was hot and humid and started raining while I was running them. I need a cool dry day to see what they will really peak at. Both are really still getting broken in so I am not too worried about the performance.

TT F91S running 10% Wildcat 18% syn/castor blend
APC 14x6 = 9400
idle was 1800


OS .91 Surpass II running 10% Wildcat 18% syn/castor blend
APC 14x6 = 9700
idle was 1700

Harry Lagman 09-05-2004 07:02 PM

RE: .91 Four Stroke Readings
 
AnthonyH - nice comparo work - keep it coming!

For the record, my OS .91 S2 Pump spins a 13x10 APC at 9200 rpm with a stock exhaust and 9400 rpm with an OS EX-502 header.

Sport_Pilot 09-07-2004 04:01 PM

RE: .91 Four Stroke Readings
 
Anthony H,
Wat altitude were you at? Have you checked the valve gap since breaking them in? The TT seems to be getting weaker instead of stronger.

AnthonyH 09-07-2004 05:17 PM

RE: .91 Four Stroke Readings
 
Sport_Pilot,
I checked the valves on both the day I ran them. I was giving them both a final go-over before mounting on their planes. My first post was a cooler and dry day. My second post was a hot rainy day. I am at 605 ft. ASL. I think both are still not broken in good and will get better once I get them in the air for about a gallon. I have ran them enough to get stable needle setting and a reliable, low idle.

I think that .91 four-strokes should be swinging a bigger prop at lower rpm anyway. A four-stroke turning above 10k seems a bit much. A 15x6 gets it in the 8k range which should be more in the power-band on a four-stroke since they make their power more with torque than high rpm. With both engines I cannot tell a difference in the throttle response between the 15x6 and 14x6 so I would say the 15x6 is not too much prop for a .91. What do you guys think? Am I crazy or missing something that is the reason most people use 14x6 on .91 FS?

Sport_Pilot 09-08-2004 07:38 AM

RE: .91 Four Stroke Readings
 
Quote:

I think that .91 four-strokes should be swinging a bigger prop at lower rpm anyway. A four-stroke turning above 10k seems a bit much. A 15x6 gets it in the 8k range which should be more in the power-band on a four-stroke since they make their power more with torque than high rpm.
Modern four strokes make more power at hight RPM than they used to. Many now make their best power above 10K My old OS .91 did best just under 10K my TT was happier in the low 10's. As I recall the OS .91 would turn a 14-6 at about 9,800 and the TT would turn it at about 10,200 or so. This was on 10 or 15% nitro. With a larger prop like a 14-8 or 15-6 they were almost the same, but I never compared them side to side with a larger prop. Your manual will tell you the maximum RPM, stay well below that and you will be OK.

Cheech 09-10-2004 08:31 PM

RE: .91 Four Stroke Readings
 
Engine : OS .91 Surpass
(loooow time, 8-10 tanks)
Fuel : 15% Omega
Glow Plug: OS #F


Prop: 14x6 Zinger
RPM: 10,200

Prop: 14x6 Master Airscrew
RPM: 10,000

Prop: 14x7 Graupner Nylon
RPM: 8,900

Prop: 13x6x10 Zinger
RPM: 9,900

Why all the props? Because the darn thing wasn't running right out of the box - only turning in the mid sixes. Re-plumbed fuel tank and lines AND loosened a way-too-tight intake valve. Tried all the props and am running the master airscrew for now. The 14x6 Zinger was best, but it's a loaner. A 14x6 APC is probably the best.

The engine has easy duty just dragging our big [link=http://aeroplano.home.comcast.net/hangar/telemaster.jpg]senior telemaster[/link] around the patch.

DTB 09-14-2004 12:10 PM

RE: .91 Four Stroke Readings
 
I can't believe nobody has posted this yet.

Engine:
YS .91FZ
APC 15x6 @ 9600
15% nitro
2.0 HP rating


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