KF7 Apex

[flipfloplife]

Am considering an Apex for my KF7 build. This is based on the bang/buck ratio. I am not really a gearhead, this is my first build. Seems like the best source of info here is the Yamaha Aircraft Conversions Page on Facebook (awkward but a TON of great info). Two goals of this post. 1) clear up any misconceptions that I may have and make sure I understand the big questions and answers about doing this. 2) give folks an opportunity to legit talk me out of this course. What would be really cool is if Bryan could finish this out and write instructions with pictures using no words longer than two syllables...

Apex mounts avail from Steve Henry for KF7
Teal makes a SkyTrax PRSU that is well thought of and gaining hours
BD makes an ECU/EMS for an Apex
Apex is already EFI (and altitude compensating? need for a turbo?)
Apex makes 150 HP out of the "box"
It SEEMS like exhausts are already being made for KF, but not sure about KF7 (couple guys putting apex on KF4's)
Edge Performance is happy to sell you EPEX boxed engine that seems epically amazing .... (AND you just spent like a Rotax 914)
Weight seems comparable to a 912is install (average of many opinions, have to account for engine accessories, ?); weight/bal close to fine?

What prop would I run?
Would it be constant speed?
How am I tying all this into either Garmin or GRT avionics?
Do I want/need a turbo? (don't know much about that altitude adjusting fuel control...)
Sled guys and Steve Henry are over 300hp on the norm on these, so perhaps running around at 200 hp is just fine. Are guys achieving this through engine tune/timing or is this a turbo situation?

seems to me that unless you go full gold plated Edge Perf there are significant cost savings here. apples to apples (?) a 912is is mid 30's with all the trimmings. the "same" apex puts out 150 hp to start and cost is ... under 15k?

Also to account for is that I'm not very bright. I don't have an engine/machine shop based shop. I've done a fair amount of outboard work, I'm comfortable with avionics. I can read (slowly). Thoughts appreciated.

[patrick.hvac]

I'll try to help with a few of the questions.


Weight - Steve Henrys build shows 178lbs. Around the 200 mark seems right. Little less than an 0-200 I guess.
Prop - BD is running NR SR118, 81" 2 blade.
Avionics tie - Engine mgmt would be standalone. If you want data on an PFD you would need to put in additional sensors. (why though). BD is using AEM which has a canbus add-on but I don't think its been ported to a GEA24 or similar yet.
http://bdturnkeyengines.com/yamaha-apex
Turbo - BD would need to comment on altitude comp (it is open loop fuel pressure compensated) but he is currently not supporting a turbo tune. You're on your own. Turbo is great but comes with another set of problems. A 100hp KF is awesome. A 150HP NA apex would also be awesome. You don't "need" a turbo. Want is another story.
Horsepower - 3-400+HP builds are happening atm. The apex has been beat up for a long time. But like anything else it has limits. Reliability depends on maintenance and integrity of internal components for HP level. Case and point, 912 big bore. Predictive maintenance, oil sampling, etc will be important.
Savings - Perhaps not what you think. Steve has a FWF list here https://www.wildwestaircraft.com/wp-content/uploads/2019/03/FWF-Pricing-1.pdf You will be into it for 20k especially if you're not a fabricator. Also remember that the 912 has redundancies the apex doesn't.


The Apex is still very much an experimental engine for any aircraft. There are a few that have been running them for a long while in various configurations. It shouldn't be discarded but don't look at it as the 'cheap' alternative. You could put an overhauled 912uls in for cost of an apex install. If you like wrenching and fabricating it might be a good option. Consider resale value as well. Rotax will undeniably fetch more in the resale market.

I've tried to be objective here. Hopefully that helps. I am a mechanic/fabricator myself and have been debating this very install. I don't have an opinion for or against but each has pros/cons that must be weighed for your situation and mission profile.





Am considering an Apex for my KF7 build. This is based on the bang/buck ratio. I am not really a gearhead, this is my first build. Seems like the best source of info here is the Yamaha Aircraft Conversions Page on Facebook (awkward but a TON of great info). Two goals of this post. 1) clear up any misconceptions that I may have and make sure I understand the big questions and answers about doing this. 2) give folks an opportunity to legit talk me out of this course. What would be really cool is if Bryan could finish this out and write instructions with pictures using no words longer than two syllables...

Apex mounts avail from Steve Henry for KF7
Teal makes a SkyTrax PRSU that is well thought of and gaining hours
BD makes an ECU/EMS for an Apex
Apex is already EFI (and altitude compensating? need for a turbo?)
Apex makes 150 HP out of the "box"
It SEEMS like exhausts are already being made for KF, but not sure about KF7 (couple guys putting apex on KF4's)
Edge Performance is happy to sell you EPEX boxed engine that seems epically amazing .... (AND you just spent like a Rotax 914)
Weight seems comparable to a 912is install (average of many opinions, have to account for engine accessories, ?); weight/bal close to fine?

What prop would I run?
Would it be constant speed?
How am I tying all this into either Garmin or GRT avionics?
Do I want/need a turbo? (don't know much about that altitude adjusting fuel control...)
Sled guys and Steve Henry are over 300hp on the norm on these, so perhaps running around at 200 hp is just fine. Are guys achieving this through engine tune/timing or is this a turbo situation?

seems to me that unless you go full gold plated Edge Perf there are significant cost savings here. apples to apples (?) a 912is is mid 30's with all the trimmings. the "same" apex puts out 150 hp to start and cost is ... under 15k?

Also to account for is that I'm not very bright. I don't have an engine/machine shop based shop. I've done a fair amount of outboard work, I'm comfortable with avionics. I can read (slowly). Thoughts appreciated.

[Jcard]

Really wanted the edge performance 300 epex.
Wrote the check for a rotax 912sti for 5k more with half the horsepower.
Mostly concerned about the engine mount and the high rpm noise.

[flipfloplife]

Excellent points all --

"Rotax has redundancies built in that the apex does not" --- can you potentially unpack this a little? I do not have a lot of piston time. I want to make sure i'm comparing apples to apples and this makes me think that I might not be.

Still in for 20k + ---- yep, totally agree, but to get to 150hp NA (which is where i think i'd land on the Apex combo, no turbo) you would have to compare that with a R914 or R915, which is gonna end up almost double that? I have talked to Hal, seems like a 912 ULS w/ a big bore gets you to a "good" place, but if you're going at "dollars for horsepower" it seems like the Apex gets it done.

tie to other avionics -- dunno on this one, BD seems to have this nailed (and a super nice guy).

insurance is something i didn't consider. re-sale value -- totally true.

JCard -- is there a history of engine mount problems? I thought that SH was running that HP range in his highlander and I'm pretty sure he sells a KF mount? As to the noise, I'm half deaf and pretty much require the fancy headphones or an in-ear solution, it cannot possibly be worse than a C-337 ... can it?

There is tremendous value in the hours behind the rotax/KF combo --- totally get that part. And the final contest for me is likely going to be between an apex and whatever hopped up 912ULS Hal and Jay can put together for me I think.

I just can't help myself thinking that 150HP NA for 20k seems like a ripping good bang/buck ratio...

[Denalifox]

I went down the APEX road to the point I started setting up my STi for one. Bought an engine as well. I did a TON of research and already started lining up the parts and pieces for purchase. I then completely pulled the plug. Living up here I just wouldn't have a total "warm and fuzzy" with as many points of failure as this Engine/gear box/fuel pumps/ECM could potentially have. Now I am in no way knocking the setup lets be clear. Its just too new and unproven for my comfort. If i lived down there Id for sure go with it. I don't want to be in the Wrangell's or Alaska range and have my ECM dump a tune, or hell even a dead battery. With all this being said, I decided to go back to my original engine choice. A hot rod O-200. Why not a rotax? I simply cannot afford one. Alaska just isn't a place to be pioneering a newer powerplant. Just my two cents.

[FlynLow]

Have you considered Aeromomentum’s AM15, looks like the higher HP version will give you close to what you’re looking for.
http://aeromomentum.com/am15.html

[flipfloplife]

Because until you mentioned it I had never heard of them. Seems pretty viable. That is also a lot of bang for the buck -- who's done one?

[alexM]

Pretty sure there's a guy at my home airport with one but I haven't seen it yet. I'll ask around.

[Eric Page]

I'll be interested to see if you find anything, Alex. I've been considering the AeroMomentum for awhile but it doesn't appear to have many installations, at least few that I've been able to find. I'd like to hear from anyone who flies behind one, as they look like a pretty solid value if they're reliable.

[FlynLow]

Nate Ashton put an AM15 (117hp) on his SS7. Search for “aeromomentum” In the above search window and look for his thread. He also has a few videos on YouTube on the engine installation.

[alexM]

Thanks! That is the guy at my home airport.

[FlynLow]

That’s cool Alex, hope you can connect with him. My Kitfox 7 is scheduled for delivery/pickup in November and at this point, the AM15 (higher HP) is the engine I plan on putting in mine.

[Kitfoxfly5521]

Great Thread! What was your final engine choice? I am considering the Apex as well seems like there have been many improvements and support. Talk to BD the other day. Supper helpful and knowledgeable! The sidewinder motor may be the way of the future with the APEX no longer being built. And support seems to be close behind!