smchale

My Feedback: (67)

*** UPDATED IN POST #42 ***

Been crunching some numbers to get a good feel for the more common turbines in the 80-100N class. I'm looking to power an airframe that is in the 16lb range without turbine, fuel, and turbine/fuel support gear. The reason for the comparison is that I want to watch the weight, while still having a decent flight time and good performance. It's easy to go up in power, but that comes with the price of weight and more fuel consumption, and with more fuel consumption comes more weight...etc etc.

The goal wasn't to drill in on numbers, rather make it more of a comparison of models based on some simple PUBLISHED values.

So, selected the following 10 canidates (feel free to offer additional options) listed by brand:

BF Turbines B100F
Evojet Booster 90
Jet Central Rabbit
Jet Central Falcon
Jetcat P100
Jetcat P80
Jets Munt Merlin 100
Jets Munt VT80
Kingtech K80
Wren 100

The first sort I did on the data was for THRUST (in lbs) per WEIGHT (in lbs). Basically what puts out the most thrust per lb of it's own weight, and it yeilded:

Jets Munt Merlin 100 10.42
Jet Central Rabbit 10.18
Wren 100 10.00
BF TurbinesB100F 9.74
Jetcat P100 9.54
Evojet Booster 90 9.05
Jets Munt VT80 8.57
Jetcat P80 7.59
Jet Central Falcon 7.33
Kingtech K80 6.10

The next sort I did was to look at what turbine used the least amount of fuel per lb of thrust. The Jet Central numbers are low here because they report an 'average' consumption, not a 'max consumption' like the other brands do, so they are shown in itallics. This resulted in:

Jet Central Rabbit 7.90
Jetcat P80 12.09
Jets Munt VT80 12.22
Jet Central Falcon 12.27
BF TurbinesB100F 14.81
Kingtech K80 14.86
Jetcat P100 15.49
Evojet Booster 90 15.53
Wren 100 15.91
Jets Munt Merlin 100 16.00

The last sort I did was for cost. Using US known sourcing, and website published prices, I sorted for COST ($) per pound of thrust. The result:

Jetcat P80 $95.23
BF TurbinesB100F $95.96
Kingtech K80 $98.57
Jets Munt VT80 $105.28
Jets Munt Merlin 100 $106.44
Jetcat P100 $110.40
Jet Central Rabbit $120.31
Jet Central Falcon $122.50
Wren 100 $124.77
Evojet Booster 90 $136.84


I still need to evaluate what it all means, but I guess it means you can't have your cake and eat it to.
For example, the M100 has the best thrust to weight ratio, but the worst fuel economy to generate that thrust.
Also shows that the P80 is still a good bang for your buck and has good fuel economy, it's just a bit heavier for the thrust vs more modern designs.

Anyways, I find this stuff interesting....

madmodelman

As a matter of interest are you talking about the P80 or the SE?

Gary.

siclick33

With regards to the validity of the fuel consumption figures, you need to compare like with like. For instance, if the M100's fuel consumption is less than the P80 when it is running at the P80's max rated thrust then surely it is more efficient? It just happens to also be able to put out more power at the expense of more fuel.

I would also be wary of some of the figures as I would be very surprised if, in real world use, the P80 uses less fuel than the VT80.

luv2flyrc

My Feedback: (6)

Unfortunately, you can not rely on the manufacturers weight, fuel consumption or even thrust figures to make comparisons. There are sometimes huge discrepancies even between manufacturer and dealer websites on the same engine!

I know for a fact the P-80se does not use the listed 9oz per min at full throttle, it's more like 12-13oz.

Mike

Aussie Bart

Why would you include a Kingtech 80, VT 80 and original P80 in a 100 Newton comparison? doesn’t take much grey matter to realize that it is an unfair comparison

luv2flyrc

My Feedback: (6)

some actual weights off engines that I have here.

Rabbit 100= 2lbs 7oz
Cheetah= 3lbs
P-80SE= 3lbs 4oz
P-120 SX - 3lbs 6oz

The Jetcentral #'s include the mount, the Jetcat #'s don't. Never had the P-80se and Rabbit 100 in the same airframes so, can't really compare the thrust between them. Have had Cheetah and P-120sx in same airframe and Cheetah makes way more power even though it is listed as 31lbs vs 30lbs respectively. This is what I mean when I say you can't trust the manufactures #'s. If you look at the test in RCJ mag, it shows P-120sx testing at 27lbs. That makes sense to me as I noticed a significant power diff between it and cheetah

Mike

joeflyer

My Feedback: (48)

The Jet Central Falcon and Evojet 90 are no longer in production. As others have stated the advertised numbers are not always accutate. It's been my experience that the Jet Central and JetCat numbers are not necessarily accurate. Wren and Jets Mint numbers are pretty accurate.

The best source is the "Gas Turbine Performance Comparisons" chart published in RCJI. You have to be careful because some of the evaluations are rather old and not representative of the latest production version of a particular engine.

I may be biased but I feel that the best bang for the buck in a latest technology engine is the VT80 or Merlin 100.

Joe

kimhey

Sorry, but I have them both, and from my experience I would have to disagree. My experience is just the opposite...



Kim

kimhey

An other thing I would take strongly into consideration, is "daily" use..

Last weekend I flew a couple of flights with my Carf Mig-15 / Jetcat P80se. Temperature was 23 degrees Celsius, and the P80se did not like transition from idle to full power. It sputtered and hesitated before normal spool up. While it felt scale like for an old russian fighter, I did not like the turbine´s behaviour. Yes, I know I can reprogram the ECU via the terminal, but I like to fly when I am at the field, not fideling with menus...

My next two flights were my F86 / VT80. It ran as smooth as usual, with the same conditions as my P80se. Either The VT80 is not that sensitive to outer temp variations, or it does the
compensation itself. I don´t know...and I don´t need to know. It works!


Numbers are great, but how a turbine runs and operates is more important in my world


Kim

Jgwright

The only source of consistently accurately tested engines is RCJI. More engine tests are due. The only accurate way to compare engines is the way that RCJI do, i.e. thrust specific fuel consumption.

John

smchale

My Feedback: (67)

Thanks for the feedback guys, and reminder about the testing in RCJI.
Interesting stuff.

Pepperpete

Can someone post the real weight of the VT80 including the mount? I am leaning in that direction for my 1/8th scale Tams F16

joeflyer

My Feedback: (48)

According to the RCJI article it weighs 1010 gm. (2.22 pounds). Keep in mind that also includes the integrated ECU and valves.

Joe

PaulD

My Feedback: (39)

The specs for the Behotec B100F sure are impressive. 120n/27lbs from a 100 size turbine.

Also makes full thrust @ 125,000 rpm not 155,000 like some others producing less thrust in this package size.

Here's the specs fom Altecarerc:

http://www.altecare.com/behotec100gold.htm

PaulD

marc s

Please note that the B100F turbine is NOT from Behotec - its made by BF Turbines in Germany and is superb.

RCJI will be releasing the latest test report this month I believe in a special and the B100F and others will be covered.

marcs

Dave Wilshere

There is a turbine special coming from Traplet/RCJi that features loads of engine tests and reports. It will be out before JetPower 2012.

You also need to understand that we don't fly full power for the whole flight and part throttle efficiency is never noted! Also the way a turbine produces power will have an affect on how long you need full power to get things rocking again. Tail pipe design affects this too, airframe weight (some people can add LOADS of weight to an airframe on tarty installs and internal finishes)
Go with your gut feeling, previous knowledge etc...like cars and partners

D

smchale

My Feedback: (67)

Paul the BF Turbines B100F is a pretty impressive unit. According to the test report that came with my particular engine it did 127.6N at 125.7K RPM. See attached.

smchale

My Feedback: (67)

Well said! [8D]
As always, looking fwd to RCJI's publication.

Robrow

Bit of a minefield this, engine sizes vary widely, these days there is no such thing as a "100 size" engine, only engines that are designed to produce 100N. The Merlin and Rabbit 100 are designed to produce 100N+ from a case size of 90mm.

It should also be noted that the rated thrust should be ISO corrected to 15deg C as per the RCJI tests, they have the only truely independent unbiased apples vs apples figures.

If a larger engine such as the BF100 produces 120N+ then it is a 120N thrust engine that has a 100mm casing. The Merlin 140 and Jet Central Cheetah are both also 100mm casing engines that produce 140N+ but I would not class them as a "100" engine.

RPM at rated thrust should also not be too much of a concern, turbine and compressor wheel tip speeds together with bearing nitrile ball speed are all very similar for most engines irrespective of rpm.

But does any of this really matter, in real world use the experienced turbine flyers will tell you that although performance is important what really counts is reliability, dealer/factory support and of increasing importance these days....value for money.

Just my 2p worth.

Rob.

PaulD

My Feedback: (39)

Oh. My bad. Just assumed since they LOOK so much like a Behotec. Sure didn't do anything to create brand identity. As ugly as Kingtech gold is, at least u know it's a Kingtech.

PaulD

marc s

I guess there are only so many colours you can use for anodising - I've been told if you can invent a dye to make white anodising you will be an instant millionaire! (anodisied white aluminium windows springs to mind ££££££££)

marcs

essyou35

My Feedback: (11)

I have both a kingtech K80 and the rabbit 100. If you are looking at powering an aircraft in the 20-22 lb wet range which it sounds like you are, look no further than the k80. If you call kingtech they will come down on the price. You will have a 1:1 ratio, and your only concern will be ripping the wings off your aircraft.

If you get up there in the 25 lb range your best best is a rabbit 100.

The rabbit is much smaller than the K80. The quality is far better too.

P80s are OLD technology, they are huge. Something you failed to compare was physical size (diameter). The rabbit is about the size of a P60, the K80 is noticibly small than the P80s. I've heard good things about the Merlin too, but it has less thrust than the rabbit. You could opt for that over the k80 but you can get a K80 several hundred dollard cheaper than the merlin.

So it comes down to cost and power. I think you only need to compare the rabbit, k80, and merlin. As I said, if you are under 22 lbs get the K80. You wont regret it. Buy anything else else and you might as well tape 100 dollar bills to your model.

The K80 is a fuel hog though! I am having a discussion with a guy about his VT80 and he claims he can get 8 mins on the same tanks I think I can get 5 out of before reallky risking flameout. But it all comes down to how you fly which we cant compare being so far away from eachother.

One other thing to consider, is service cost!

Jetmunts have to be sent to Germany, good luck with that.
Wrens are EXPENSIVE to service.
Jet Central charges 250, cna be serviced in the US or mexico
Kingtech charges 300, can be serviced in the US.
Jet cats are also decent to service but I hear the customer service is falling aprt too.

I have never owned a jet cat, but I have seen plenty. They are good turbines but are falling behind on the times. I do like the the New P100, but it is basically the same as the rabbit, so might as well get that.

I've heard a rumor the P100 and rabbit 100 are the same turbine....

Vincent

My Feedback: (61)

I am flying a 24lb dry F-86 on a P-100rx and it has been a perfect combo. The onboard fuel capacity is 90oz and i get 7-8mins easily with ample reserve. I dont know what jet you have in mind but the weight you quoted would fly on anything from 14lbs thrust on up. The smaller the motor the higher throttle setting you will have for "cruise". A more powerful motor like the P-100rx would have you way down on the throttle making better use of the fuel. The weight on the P-100 is around 2lbs and the install is simple, it is night and day in performance and simplicity compared to the older P-80se size motors.
Vin...

siclick33

Really?? I am fortunate to live not far from Wren but I have found their servicing to be amongst the cheapest I have come across. Maybe the US is different.

grbaker

My Feedback: (29)

Dreamworks is a JetsMunt service center. There is no service center in Germany as they are built in Spain.

That is a true statement if you are talking about the VT80. Not true if you are comparing the Merlin 100 which has more thrust than the Rabbit