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-   -   new Wren 75 (http://www.rcuniverse.com/forum/rc-jets-120/11243630-new-wren-75-a.html)

alasdair 09-28-2012 03:24 AM

new Wren 75
1 Attachment(s)
I have been running my new Wren 75, the kero-start "Jubilee" version (everything is "Jubilee" in the UK this year)

I removed the Wren 54 mk3 (63 N rated) and fitted the new 75N engine (identical size) with its new smaller valves and new smaller ECU. On my new engine the fuel supply splits after the ball valve, one pipe to the start valve, the other to the run valve. Both pipes go into the front of the engine. The ignitor lead and temp sensor are still external.

I tried a couple of starts at home. The first try didn't start as I had not primed the fuel lines. The second didn't work as I had left the fuel tap turned off.

When I got my act together however, it started very well. It is a bit slower than a gas start. It seems to pause at the initial warmup phase for a while and then ramp up very gently. I tried shielding the intake a bit in case the strong wind was causing it a problem, but both starts at home, and all starts at Machrihanish, went very well. Throttle response seems better than the Mk3, but I didn't time it.
I have the two side tanks feeding in parallel to the centre tank, and a felt clunk in the centre tank feeds directly to the pump. Fuel consumption is probably greater, but<font face="Arial"> I still set my timer for 7 minutes, and after it goes off I land. I have never had less than 1/2 left in the centre tank, and sometimes it is nearly full. I probably use full power less than before.</font>

I can't say that it is noticably faster-the Gripenwent jolly well on the old Mark 3 - but the vertical climbs are more sustained

By the way, I have just one battery, a 2S Lipo, in the Gripen (but it's a 6400 mAh as I needed the weight). It feeds the engine directly, and the Rx through a Powerbox digiswitch that regulates it down to 5.5 volts

Dr Honda 09-28-2012 03:32 AM

RE: new Wren 75
Thanks for the report.

Looks like they are using the little valves from the 44... but what's the "New Smaller ECU" that they are using? Is it just Gasper's V10??

alasdair 09-28-2012 03:46 AM

RE: new Wren 75
The ECU supplied with my Wren 75 is in a rectangular box, like the later Mk3 ECU that I replaced, but it was smaller so I cut a new foam rubber mount. I don't know if it is Gasper's V10.

stuart_80 09-28-2012 03:51 AM

RE: new Wren 75
The turbine ran well Alasdair :-)

Model went nicely too, you've certainly got the landings down to a fine art. Look forward to seeing it at macrahanish next time

Stuart<br type="_moz" />

Bob_B 09-28-2012 04:59 AM

RE: new Wren 75
yes they use the new xicoy ecu about the size of a mini servo

Wren Turbines USA 09-28-2012 06:59 AM

RE: new Wren 75
Thrust figures are listed in the Wren turbine clinic!

alasdair 09-30-2012 01:37 AM

RE: new Wren 75


ORIGINAL: Wren Turbines USA
Thrust figures are listed in the Wren turbine clinic!
Thank you. Could be handy to know some day.
Do you happen to have any figures for acceleration times? Somebody asked me and all I could say was 'seems quicker than a Mark 3' but I didn't time it.
I like my 75 and it is great value.

Also BTW, I noticed on your Clinic page a "coming soon" leaflet about a 140 and 180 plus. Are they upgrades of the 120 and 160 in the same case size?

Dr Honda 09-30-2012 04:22 AM

RE: new Wren 75


ORIGINAL: R_Belluomini

yes they use the new xicoy ecu about the size of a mini servo

Thanks for that.

I was at a jet rally on Friday, and Saturday... and I got to see one of the new ECU's. And dang.... it is small !! It's even smaller than the old Green case ECU's the the MW44 and Kolibri's got.

Wren Turbines USA 10-01-2012 02:45 AM

RE: new Wren 75
1 Attachment(s)
140 drawing

siclick33 10-01-2012 02:58 AM

RE: new Wren 75
I can't help but think that our US friends are getting a bit of a raw deal with this engine. The nearest comparison that I can find is the Jets Munt VT80. In the UK, the Wren75 is £1200 and the VT80 is £1450. This makes the Wren exceptional value and would be perfect for someone who is starting out in turbines or anyone who needs a high quality engine at a bargain price.

In the US, the 2 engines are about the same price so I don't understand why anyone would buy the Wren 75 over the VT80 which has more power and, arguably, a cleaner install.

Don't get me wrong, I'm not knocking the engine (I own 2 Wrens myself) but I can't quite understand the pricing philosophy.

Bob_B 10-01-2012 03:32 AM

RE: new Wren 75
The dollar is trading at $1 to £.6197 which converts to $1936.00 us dollars seems the Wren USA pricing is in line

siclick33 10-01-2012 04:29 AM

RE: new Wren 75
But you shouldn't be paying UK tax at 20% so that factors down to 1613$

I'm not sure how much tax/import duty you have to pay in the US but it doesn't change the fact that, in the UK, the Wren 75 is about 85% of the price of the VT80 and in the US they are the same price. With both the VT80 and Wren 75 coming from Europe (albeit I accept in countries with different currencies) I can't understand the differential.

There may well be a valid reason for it but, at first glance, it looks odd to me.

SJN 10-01-2012 04:39 AM

RE: new Wren 75
The VT80 is 1650 euro, and is 1300£

The wren is 1510 euro , and is 1200£

The difference is not that great, but you get more when you but the VT 80
more thrust, and a more modern turbine withe the accesories under the front cover.

Dr Honda 10-01-2012 04:52 AM

RE: new Wren 75
That is strange.

ACTUALLY........ In the USA, the new Wren is MORE expensive. They both retail for $1999 (USD) witch is a good price, and I'm assuming the prices are coming down in general, because of Kingtech. But, if you buy a VT-80 from Dreamworks... you get either $150 store credit... or $100 cash discount. SO... the VT-80 is only $1899 in the USA.

Like you guys said... who knows what kind of duties are put on these... but I don't think there are any tariffs on model engines coming into the USA. (especially from Europe)


Sorry... I was a little wrong. The new 75 is $1950 here. But, with DreamWorks discount... the VT-80 is still $50 cheaper.

thunderchief 10-01-2012 08:30 AM

RE: new Wren 75
Just my two cents....both turbines are probably excellent but the Wren I believe has one advantage in the US . The advantage is Ron Ballard. Unbelievable service. And if you live in Ohio its with in driving distance.

siddus74 10-01-2012 10:24 AM

RE: new Wren 75
I am fortuante to know Paul from Wren Turbines in the UK, they are only 40 minutes up the road from me and I attend there open days twice a year ... I've called Paul on his mobile phone over the weekend on occasion and he has talked me through ecu changes and setups - his passion is amazing.

Also recently (after stuffing my starfighter) whilst running up my Wren SS on the test bed I called him to discuss my temps and his advice and support was second to none ... just based on his knowledge and the support I have got from Wren here in the UK I would buy the Jubilee without question (if I needed it and had some money [:o])

Im lucky that my SS was virtually undamaged so will live to see another airframe .... Also here in the UK at the Wren open day's we have the option to take our turbines up and get them serviced and checked over (and a bearing changed at a reduced cost, they get us to take them apart and reassmble them on site) ... My SS is still on the test bed so I shall take it up for an inspection anyway ... as much as I love Jetcats and AMTs etc, you dont have that option with any other makes do you?


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