Webra 15cc P5/Speed-P5/ Performance  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Tachometer Readings >> Webra 15cc P5/Speed-P5/ Performance
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Webra 15cc P5/Speed-P5/ Performance - 4/28/2007 4:59:04 PM   
NikolayTT


 

Posts: 575
Joined: 9/29/2002
From: Tampere, FINLAND
Status: offline 		Hi Fellows,

My search over RCU on RPM-readings of WEBRA-15cc did not produce much.
I am especially interested in the latest models of Speed-P5 and plain-P5.

Could you please post your experience, mentioning at least the most
important of the things in the list below:

1) Propeller: Maker, Type, Material, Diameter, Pitch, ...

2) Pipe: Tuned, Wide-barrel, Pits, Standard, or Open exhaust, ...

3) Fueling: Pumping by Perry-pump, Direct Pressure from Crank-case,
Pressure from the Exhaust barrel, ... any Special Regulator on Carb ...

4) Fuel: Oil% and type(s), Blend-proportion%, Nitro%, ...

5) Environment: Temperature, Altitude/AthmPressure, ...

6) How New/Old/Used the Engine is.
7) Did you "tune/improve" the engine and how ?

Thanks,
Nick
       Post #: 1

RE: Webra 15cc P5/Speed-P5/ Performance - 4/30/2007 1:55:42 PM   
Hobbsy



Posts: 10691
Joined: 12/2/2001
From: Colonial Beach, VA, USA
Status: offline 		Webra P5 .91
Fuel==Fox 5% nitro with 20% castor oil
Plug==Fox Miracle plug
Prop==APC 14x12
RPM==8,400
Stock muffler

< Message edited by Hobbsy -- 4/30/2007 2:00:34 PM >

_____________________________

"I have gone faster backwards, upside down and on fire than most people have gone at all" Don Garlits

(in reply to NikolayTT)
       Post #: 2

RE: Webra 15cc P5/Speed-P5/ Performance - 4/30/2007 3:49:28 PM   
NikolayTT


 

Posts: 575
Joined: 9/29/2002
From: Tampere, FINLAND
Status: offline 		Thanks Hobbsy,

It looks that propeller is a bit too "heavy" for this engine,
which seems to be mich higher-rpm-engine, isn't it ?
If I use the calculator of Pe, it gives that this propeller
have only 1.68 bhp, while the engine is advertised to
be able to deliver even more than 3bhp. It seems
I'm missing some point here; please clarify further.

Regards,
Nick

(in reply to Hobbsy)
       Post #: 3

RE: Webra 15cc P5/Speed-P5/ Performance - 4/30/2007 4:57:28 PM   
Hobbsy



Posts: 10691
Joined: 12/2/2001
From: Colonial Beach, VA, USA
Status: offline 		Nik, here is a link to the P5, the 14x12 is the smallest recommended prop, the engine is designed to run in the 8,000 rpm range for quietness and to meet European noise rules. I like quiet so I use it the way they intended. Others have tried 14x6 props and were disappointed. http://www.webra-austria.at/motor.php?search=1067&folder=AERO&lang=EN

_____________________________

"I have gone faster backwards, upside down and on fire than most people have gone at all" Don Garlits

(in reply to NikolayTT)
       Post #: 4

RE: Webra 15cc P5/Speed-P5/ Performance - 4/30/2007 8:01:14 PM   
NikolayTT


 

Posts: 575
Joined: 9/29/2002
From: Tampere, FINLAND
Status: offline 		Thanks Hobbsy,
Then I just wander why Webra is telling on that www-page those figures for Power and RPM. Here is my way of thinking and
I wander what is wrong: - Using the Calculator of Pe and assuming APC propeller, and power aim 3bhp (out of 3.25) and
the RPM to be 13500 (out of 16000), and iteractively chaning the DxP of the propeller, in few iteractions I come to the
cases like those:
APC 13x7 @ 13500 gives 3.11 bhp, and speed of 144 km/h, thurst = 7.19kg,
APC 12.5 x 8 @ 13500 gives 3.00 bhp and speed 165 km/h, thurst = 6.84kg,
that is what I exactly would like to have, but it seems Webra is the wrong
engine for this speedy performance, is it so ?
BR,
Nick

(in reply to Hobbsy)
       Post #: 5

RE: Webra 15cc P5/Speed-P5/ Performance - 1/12/2008 11:26:10 PM   
RVman


 

Posts: 548
Joined: 6/2/2003
From: Guelph, ON,
Status: offline 		Got my 91P5 recently. After three 16oz tanks i am turning 9300 with a Masteraircsrew K series 15-8 and Omega 15. I expect to get about 9500 when it is more broken in. I will likely run a 15-8 three blade for flying. This thing is a brute.

_____________________________

Tom G.

(in reply to NikolayTT)
       Post #: 6

RE: Webra 15cc P5/Speed-P5/ Performance - 1/13/2008 7:46:34 PM   
NikolayTT


 

Posts: 575
Joined: 9/29/2002
From: Tampere, FINLAND
Status: offline 		Thanks Tom ! It looks still far from what Webra page is telling,
especially the rpm up to 16000 ??? With this propeller you
have got (calculated) power of about 2 bhp and 6kg thrust.
The company tells the engine has more than 3 bhp and if
calculate the propeller and rmp back that would give
for example on APC 14x6 thurst of 7.2kg at 12500 rm
which is about 2.9 bhp; that is about 30% more than
what you have got. Also I wander why Webra is advicing
propellers like 14x12 and 16x8, they seems too heavy
for this engine...

(in reply to RVman)
       Post #: 7

RE: Webra 15cc P5/Speed-P5/ Performance - 1/13/2008 9:51:36 PM   
RVman


 

Posts: 548
Joined: 6/2/2003
From: Guelph, ON,
Status: offline 		The 14-6 is way too small for this engine, it is designed to run large props. The carb is the same one as the 55, a 9mm throat so it won't do 16K very well. The engine could easily handle larger props than the 15-8 i used. It is hard to compare to a 'normal' 91. It definitely has way more power than a supertigre 90 I also run.

_____________________________

Tom G.

(in reply to NikolayTT)
       Post #: 8

RE: Webra 15cc P5/Speed-P5/ Performance - 1/19/2008 9:31:30 PM   
Hobbsy



Posts: 10691
Joined: 12/2/2001
From: Colonial Beach, VA, USA
Status: offline 		Tom, I tried the 14x12 on my SuperTigre .90 and MVVS .91. THe SuperTigre .90 only managed 7,000 rpm and quickly got hot, the MVVS .91 turned the 14x12 at 8,200 and ran just fine. I don't understand people having such a problem believing instructions. As you say the 14x6 is a complete waste of the Webras abilities. As with all engines the HP ratings are a joke.

_____________________________

"I have gone faster backwards, upside down and on fire than most people have gone at all" Don Garlits

(in reply to RVman)
       Post #: 9

RE: Webra 15cc P5/Speed-P5/ Performance - 3/26/2008 8:29:14 AM   
CustomPC


 

Posts: 349
Joined: 4/19/2004
From: SydneyNSW, AUSTRALIA
Status: offline 		Can someone tell me what the exchaust bolt spacing is for the 91-p5.

Thanks

(in reply to Hobbsy)
       Post #: 10

RE: Webra 15cc P5/Speed-P5/ Performance - 3/26/2008 7:42:23 PM   
RVman


 

Posts: 548
Joined: 6/2/2003
From: Guelph, ON,
Status: offline 		its the same as the OS 91 but the port size is totally different. A muffler from an OS 91 may still work ok even though it blocks a lot of the port. Otherwise you will need to ask Bisson or someone else to custom make one or buy the webra muffler.

_____________________________

Tom G.

(in reply to CustomPC)
       Post #: 11

RE: Webra 15cc P5/Speed-P5/ Performance - 4/27/2008 4:12:08 AM   
RVman


 

Posts: 548
Joined: 6/2/2003
From: Guelph, ON,
Status: offline 		Graupner 15-8 3 blade, bisson inverted pitts muffler, i am taching ~7300 rpm.

< Message edited by RVman -- 4/27/2008 10:09:44 PM >

_____________________________

Tom G.

(in reply to RVman)
       Post #: 12

RE: Webra 15cc P5/Speed-P5/ Performance - 5/1/2008 1:44:21 PM   
speedster 1919



Posts: 1467
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline 		NIK Your assuming that the computer prop calculator is 100% accurate- which it is not, and no engine manufacturer max RPM was ever hit by the recommended prop. In case you were to put a very light load or overly small prop on that engine it is warning you to limit RPM to 16,000 so it won't break a con rod or loose a bearing. More and more prop recommendations are done for noise levels and not the most power or speed.

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to NikolayTT)
       Post #: 13

RE: Webra 15cc P5/Speed-P5/ Performance - 5/12/2008 8:02:07 PM   
särpet


 

Posts: 9
Joined: 2/26/2007
From: joutseno, FINLAND
Status: online 		pipe lenght from exhaust flange to reflector plate 450mm
fuel 15% mobil glycoule30 3% castor and NO nitro
apc 13x6 13600
apc 13x8 12300
apc 12x10 11600
apc 13.5x12.5 9600
apc 13.5x13.3 9400

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(in reply to speedster 1919)
       Post #: 14

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Tachometer Readings >> Webra 15cc P5/Speed-P5/ Performance
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