Kitfox 4 Subaru Aircraft Engine Update NSI EA81

[@builditright4666]

Everybody seems to bash Subaru but it looks to me like its a good performer.

[@cramersclassics]

I have been very happy with it. Performance is excellent and it's economical and reliable. Weight is the only penalty. I enjoyed being the first test pilot for NSI back in 1993. Teaching my son to fly it now! Thanks, Kirb.

[@gypsymanjeff2184]

Just got an 83 subi gl wagon with ..that engine only 130g miles. Didn't realize the gold nugget I found til recently..wow lots of folks love these ..ultralites planes.n a whole host of others ..but the wagon is sweet 4x4 ..4 spd..shift on fly... man I only paid 65$ for the thing ..well just had to say ..good job on yours and best to you..

[@montgomeryavionics8721]

NSI PSRU drawings came with my plane. My son who is a cad draftsman is going to transfer the NSI drawings into CAD so we can make any of the worn parts. I also purchased a goodnused EA81 engine and will rebuild it to the NSI specifications. The Ellison throttle body is operating perfectly and so are my dual ignitions. The J3 tail spring raised the tail and lowered the nose, and also improved the Marco tailwheel geometry. Very positive handling compared to the original, turn left only geometry. The brakes were my last mechanical issue, due to the pedal to master cylinder arc. After a couple of iterations the brakes now will stop, not over brake, causing the tail over the top. At 3800 Rpm and full aft stick the brakes hold, at 4000 I get a creep.

[@cramersclassics]

Great news Doug. I have the contact for the current owner of the Ellison if you need it. I have wondered if a taller tail spring would work to improve forward visibility on the ground. Can you forward more info in the new tail spring? Also, I replaced my wheels, calipers and master cylinders with new Matco 6x6's in 2019. The techs there were very helpful and included a special master cylinder piston designed to work with low leverage brakes on the Kitfox 1-4 models. I can old my brakes up to 4600 RPM and they are not too strong for normal braking. Can send me your contact info via my son's business email and I will contact you directly: [e-mail] Cheers, Kirby

[@jerrymarsh5171]

Hi Kirby! I have always loved the ea81 engine. I had one in a Merlin GT.

[@cramersclassics]

I have removed the muffler blanket at the last condition inspection. I think it was causing small cracks in the muffler which had to be welded. Also, the tires/wheels are 6x6 not 5x5. Still flying well!

[@nateashton8282]

Awesome installation! Great work! Thanks for sharing!

[@amjm1414]

Hello,i have one here in Brazil,on kr2s.great.

[@cramersclassics]

Awesome! Can you share your cruise and top speed numbers with us?

[@cramersclassics]

I used to have the NSI CAP electric prop. When I did I would set takeoff to 5000-5500 RPM and it would climb at 12-1500 FPM! After takeoff I would add pitch and cruise at 3400 RPM at 100. The CAP Prop is amazing but 20 Lbs. heavier. Since my son was new to flying the Kitfox I installed a new WarpDrive prop seen in the video, ground adjustable to keep it simple. I pitch it at 22 degrees (measured 8" from tip). That setting yields about 4600 RPM on takeoff. I cruise solo at 4000 RPM indicates 95 MPH on GPS. 4200 gives about 100 MPH at 3000'. At 7500' 4200 RPM gives 105-109 MPH at about 4.5 GPH fuel burn. Send me your email if you wold like to connect directly.

[@bernardosilva4869]

[e-mail] // [e-mail] THANK YOU AGAIN!!

[@cramersclassics]

Empty weight is 725 with the BRS parachute behind the seat. Gross is 1200. I usually fly with the right tank as the main supply and the left tank with 3 gallons as reserve.

[@zachfisher9177]

Hi Kirby I am installing the same engine in my kitfox 4 is it necessary to run an electromotive ecu or can I just run it as is? Thanks in advance Zach

[@ParadiseHG]

Hi Kirby, I wonder if you still monitor comments and questions here. I have Kitfox 4 1200 with a EA81 by Formula Power (from back in the day) that has a toothed belt drive. Performance is good, the drive reduction as about 1.84/1. Max static rpm is 4300 and will go 4500 in flight. The only problem I am having is the oil temp climbs immediately when the aircraft climbs. What do you consider to be the max allowable oil temp. for this engine?

[@cramersclassics]

My average oil temp is 180-210 here in warm SoCal. I am not running an oil cooler. Never had oil temp problems with this motor. What are your coolant, and EGT's ? Does it cool down in level flight? If so its likely a cooling airflow problem. My static RPM is about 4600 and will go to 4800 in flight depending on how I set prop pitch. Currently at 21 degrees for my 70" Warp drive with tapered tips, measured 8" from tip. I think my reduction ratio is about 2.3/1

[@ParadiseHG]

@@cramersclassics my coolant runs 185 no matter if at climb, cruise, or idle. No EGT gauge. The oil stays at 190-210 in level flight, climbs rapidly to 250 when climbing, cools off pretty quickly in cruise. I am in south Florida, so pretty warm here too. I also have 70" Warp Drive tapered tip prop and round cowl. I am just wondering how hot is too hot for oil temp. My current gauge goes to 250, so I just ordered one which goes to 300. If it is maxing out at 250, I think that's tolerable, but if it is actually going to 275+, I think I should install an oil cooler.

[@cramersclassics]

@@ParadiseHG I run Mobile 1 synthetic 15w-50 which I think can tolerate up to 275 degrees. I would say you are running a bit hot on the climb, but if you stay below 250 you're probably ok once you cool down in cruise. I'm assuming you are full-rich in the climb? Oil cooler might be a good idea, but probably not required IMO. You can contact me via my website email if you want to chat.

[@cartersanche3852]

@@cramersclassics went through similar in our families glastar. Went through cowling and oil cooler mods only to discover a line had bit into a barb fitting and restricted flow enough to cause problems. Don’t rule out simple things!

[@funbunnyproductions9513]

May I ask what your empty weight is? Can you carry a passenger with yourself and fuel?

[@ivanpasichnyuk8848]

Hello Kirby. Do you know where can I buy parts for engine mount? I`m looking for a top and bottom engine vibration isolation.

[@cramersclassics]

Hi, I replaced the rubber engine mounts in 2018 with new ones from Aircraft Spruce. Lord J-3608-1 you need 8 of them.

[@ivanpasichnyuk8848]

Kirby Cramer Thanks

[@andrewnewman6451]

Hi There what MK of kitfox is this ? I have just bought a MK 1 and i am currently looking at engine options.

[@cramersclassics]

This is a Model 4 Kitfox. You model 1 kitfox has a lower gross weight so you will likely be looking at Rotax 503, 532 or 582 two stroke twins.

[@andrewnewman6451]

@@cramersclassics Thanks for the reply :-) My fox has the rare KFM 112 Engine which looks like a lovely little engine. Like the airframe the engine has on 517 hours but hasnt been run in four years...I am quietly hopeful that the engine will be ok...but checking out my options..I dont really want a 2 stroke :-(

[@craighuber6128]

Can you tell me more details about the ignition system?

[@cramersclassics]

The NSI ignition has two pickups on the flywheel. Two MSD racing ignitions that are adjustable for advance. Since there are only one set of spark plugs, the two ignitions feed into a diode that prevents feedback to either system. Then the spark goes to one NGK BR8ES plug on each cylinder. Each igntion has a separate power lead and circuit breaker direct from the battery. Some have used two batteries for complete redundancy.

[@craighuber6128]

@@cramersclassics Got it. Thanks.

[@bernardosilva4869]

Hi Kirby! how u doing? ....I'm from Brazil and I just have purchased an CH-701 Zenair with an SUBARU NSI EA81. Ive heard that after a while the reduction unit gives problem..... Have you ever heard something about it? ....Could you help me please?? THANKS!!

[@cramersclassics]

I have not had a problem with the NSI gearbox. I used Penzoil 30wt oil, 650cc and change annually. Set idle at 1400 RPM. Feel free to ask any questions!

[@bernardosilva4869]

@@cramersclassics thank you very much! ....what temperature does the oil operate? Do you have an oil cooler?

[@bernardosilva4869]

what maximum takeoff rpm do you reach? and cruise rpm regime have you been using?

[@glikar1]

Hey Cramer, I have a model 3/4, 1400lb gross on floats, with an EA81. How'd your wt. and balance work out? Did you need extra wt. in the tail? Thanks for publishing your video!

[@cramersclassics]

I have a 5 lb. boat rudder zinc bolted on the tail. I'm less than an inch from forward CG using a 1200 lb. gross. I usually wheel land to maintain forward visibility. Taping the elevator and rubber gaps with clear Gorilla tape improved the effectiveness of elevator on flare and helps the small, model 3 rudder a bit on crosswinds. Thanks for watching! -Kirb

[@glikar1]

@@cramersclassics Right, all sounds familiar. Mine feels nose heavy on wheels, but a totally different beast on floats. Take off is quick and flies, lands beautifully on floats.

[@cramersclassics]

@@glikar1 I rigged my Kitfox for Aerocet composite floats many years ago. Moved before I got a chance to test and sold the floats. Next to aerobatics, I think float flying is the most fun! What type of floats are your flying?

[@glikar1]

@@cramersclassics I use Aerocet floats too. Great floats, surprisingly tough. If I remember correctly Aerocets were rated for 1100lbs, but I've flown them at nearly 1400lbs gross. Plowed a little water while getting on the step for sure.

[@glikar1]

@@cramersclassics Aerobatics would be fun. Closest I got was a Hammerhead while on floats. The Kitfox did great.

[@MrLoveglov]

Wht engine oil u use ..

[@cramersclassics]

I use Mobil 1 15W-50 in the engine and Pennzoil 30W HD in the gearbox.

[@crispincurtis8585]

Is it a pushrod engine?

[@cramersclassics]

Hi Crispin, yes it is a pushrod, solid lifter, EA-81 engine. They were used in 1980's Subaru Brats and GL models in the U.S. Simple and reliable 1.8 litres. Good torque at low RPM. Water cooled for efficiency. The later EA-82's were OHV engines, more powerful, but too wide for the Kitfox.

[@crispincurtis8585]

Cool, I remember when the brat was first on the market, knew someone that owned 1😎👍

[@crispincurtis8585]

Is it less expensive than a Lycoming?

[@cramersclassics]

Lycomings were too large for the Kitfox 1-4. The Rotax 912 are popular and lighter weight. The NSI/Subaru has worked well for me, but NSI is out of business. Lycomings fit later models.

[@cramersclassics]

@@crispincurtis8585 And yes the Subaru is much less expensive due to automotive volume, but requires DIY.

[@TheRogerhill1234]

It being parked for 16 years, and the Subaru installation...well, they are probably related.

[@cramersclassics]

The Subaru has been trouble-free for almost 500 hours now. Divorce and sole custody of my kids grounded me for 16 years, not the engine. My son is flying it now so it was worth the wait!