Mounting 618 and 670 to KF-IV

[rdooley79]

I cruise at 6000, redline is set at 6350. Cruise at 6000 is about 83mph indicated but that's at 7500msl so at sea level you'll get better performance.
You could get more power out of this engine but it's tuned for reliability and longevity.
Spinning the engine faster means the prop spins faster so that introduces gearing considerations. The RPM that the 670 likes to run is right at 5900-6000.
It just humms right along at that power setting. Fuel burn is averaging right around 4.5-5gph. That's about the same as a 582.

I didn't do any port timing changes but it did come freshly built with an hour on Rotax Rick's test stand, ready to go. The exhaust timing is done with the exhaust which is critical for these engines to make power with a nice flat power curve, consistent power throughout the rpm band. The exhaust Rick has available is the "breakthrough" for the 670 to be used on aircraft. Dual Ducati electronic ignition is a must to be even considered as a serious aircraft engine to me.

Mounting the exhaust is the trick with the 670. It's a larger exhaust and takes up more space.

The prop pitch tends to work best if you pitch it a little course. I'm running a 3 blade Warp Drive, 72" 3:1 gearbox. The 670 has more torque and can swing a loaded prop better than a 582 and provides good thrust as well.

Jetting needs to be watched, especially at a mile high field elevation. Rick likes to run these engines rich, 40:1 and big main jets. I've had to go down in jet sizes because of my altitude. I'm running 162's with both needles dropped to the top notch. This makes the plugs look nice rich brown without being too rich. Rick sets them up at sea level with 180's, needles set to the middle notch. This made my engine cough and stutter but once I jetted it like a rich 582, it ran GREAT! I might go down to 160's but I'm watching the plugs as the true indicator, NOT egt's. They're showing 900 at WOT, 1150 at 5700. It's weird but talking with Rick about it he says that's about right and is typical. Also he confirmed the prop pitch being a bit on the course side working better also. I can say that it's running great now.

Swapping out the 582 for the 670 is a fantastic upgrade. Made my plane fly so much better. If only I could fly as well as the plane! Working on that.

[Aker]

Any videos yet?

How much weight was gained with the 670? Is it approaching the weight of 912?

[Aker]

What is the weight of the plane with the 670 installed?

[rdooley79]

Weight with the 670 is 640lbs, in my bird. NOT every Kitfox is the same.

The 670 with tuned exhaust is 20lbs more than a 582 with exhaust.
20lbs for 25+hp gain AND way more torque. 670 puts out 90+hp. Rick says it's 92hp with the purple 670 head and tuned exhaust. It'd be cool to dyno it but that's not going to happen. I want to fly and enjoy the fruits of my labor.

Please don't turn this in to a 912 vs. thread. That's been beat to death.
This is for those of you who have a 503/582 bird and want more power WITHOUT changing everything firewall forward. Yes engine mount and most of your instruments would change with a 912. It's going to cost 3x more to get in to a 912, that's 80hp. Too many points to argue but not appropriate to this thread.

Thing's to keep in mind with my plane vs. yours;

Grove gear, master cylinders for dual controls and brakes are much heavier than stock.
Larger radiator + Coolant = more weight
Warp Drive Prop = Tank, heavier than IVO or Powerfin, more resilient to dings.
Paint is thick and heavy fabric used all over my KF.
Desser 22" Tundra tires vs 650x6's that were on it before.
Heavy transponder and ELT.

BEFORE the Grove Gear and 670, tires and prop, the previous owners W&B said 590lbs. So 50lbs gain with the upgrades but offset with 25+hp.

My W&B now is perfect. 2x 225lb guys, Full tanks(17g) and 40lbs of baggage. It puts me .1 in front of the max aft CG of 16".

The 670 it's self is only about 10lbs heavier than a 582. The exhaust is where the extra weight over the 582 comes in to play. The exhaust is about 10lbs heavier than the 582 exhaust. 20lbs total.

You "can" use the 582 exhaust on the 670 but it de-tunes it to about 70hp. The 20+hp gain with the 670 tuned exhaust is where all the torque and fuel savings come in to play.

Seriously, for anyone with a 503/582 powered Kitfox/Avid/RidgeRunner get the 670. It's AWESOME!

Contact Rotax Rick (239) 572-0021 -or- faircopters@aol.com

By the way, don't believe the BS about Rick. I've seen it and read everything. What a load of manure.
Most everything is related to proper engine set-up and tuning. Most of it is common sense, not everyone has that unfortunately.
-but they sure can complain about it on the internet-

Video will be done when it gets warmer. I just want more time with the engine and give you all a really good report and enjoyable video to watch.
20 flight hours on the 670 and adding more as weather and work allows. More updates coming. PM me with any questions. I'm happy to talk to anyone about the 670 or Rotax Rick.

[Grogen]

I've got a model II with a 670 with over 300 hrs. I love it and it made a good mountain plane out of the fox. Here are the specifics: pre 1991 670, newer models have different crank case casting, the older version is a direct bolt on to the 582 mount. C box 3:1, 38mm mikuni carbs with green sky altitude comp system, 72" power fin prop, tuned exhaust by CPI racing in Morgan, UT.

I am getting 98 hp out of it with 4.5-5 gal/hr. Great performance. I only wish I bored it out to 740 to start with. You can get up to 150 hp doing that. I have over 300 hrs on mine and hasn't skipped a beat. You do need to know how to run a two stroke and to keep it in perameters. I have an EIS to track all of the engine perameters, a must in my book. It alerts you immediately if anything is out of limits.

Let me know if you need more info. I would never go back to a 582 and I can buy several replacement engines for the cost of one 912. Not to mention the 912 is much heavier. Kitfox and 670 is a great combo.

[Grogen]

Orignial Cowling

[Grogen]

This is the current configuration. Cooling is much better, gained 4 mph, and no radiator (speed break) handing under the fuselage.

[Grogen]

I used my original top cowl and made my own bottom cowl. The front cowl is a piper hose you can get for $120 from Aircraft Spruce. I built my own brackets for the radiators mounted up front in the cooling holes in the front cowl.

[Grogen]

This is the other side. A tuned exhaust is important to get the HP out of this engine.

[Grogen]

This shows the old top cowl glassed into the new top and the aft portion of the bottom old cowl glassed into the new. Turned out great.