Turbocharging

[patrickh99]

Is anyone running a turbocharger on their Bearhawk? I'm debating TIO-360 vs O-540 (or IO-540).
I fly mostly in the midwest, but frequently go to 10k for winds & weather. I also plan to take 1-2 trips into the Rockies annually.

Turbo causes more heat issues and possibly shorter engine life, but is somewhat lighter and less expensive than a 540.

Decisions, decisions....

[Chris In Milwaukee]

I guess some would say that it's "just one more thing", but I bet it would be great. With all the room you have under the hood with a 360, I have to imagine there's plenty of room for a turbo, intercooler, and enough airflow to keep everything cool. But this coming from someone who's never been there. :-)

[Battson]

I would think there would be less weight advantage than one might think, once you've looked at intercooling.

The TIO-360-A can weigh up to 407 lbs dry. I wonder if that includes the intercooler? That gets you 200hp.

Comparison, IO-540-D weighs in at 410 lbs dry. That is the 260hp I have been enjoying, so I am biased

[patrickh99]

Agreed, and at 12K' when trying to cross a mountain ridge, you will be about 55%, or 143HP. The TIO-360 should around 75%, or 150HP. Not a lot of advantage there either.

Sounds like I may have just talked myself out of a turbo.

[EricP]

Patrick, I had thought about the same thing too. The Continental IO-360 with the turbo seems like it could be a perfect engine for the Bearhawk. However, as in everything with homebuilt aircraft there are a lot of details. Since Bob has already got the IO-540 working I think in the long run it would take less to make it work and make it work right. The IO-360 tends to need help with making power at altitude with intercoolers (well, pretty much every turbo needs this!) and the Merlyn wastegate (not the standard fixed waste gate).

I used to fly a Seneca II (for charter) with the IO-360 and it had one engine that couldn't make the rated 75% power at 7500 ft because the turbo or wastegate or something was out of adjustment or broken. The other engine did better but still wasn't that impressive. The point being it can get very complex and hard to fix when it comes to turbos. Simple is better than complex with homebuilts.

We ended up going with the Lycoming IO-360 200 hp engine (normal aspirated) but I think for your purposes the IO-540 would be a great and wise choice.

[Battson]

It's kinda disappointing, because I love the "idea" of a fire-breathing turbocharged Bearhawk. But in reality the numbers just don't seem to stack up right. Oh well.
I guess that's why nobody has gone and done it, yet. (AFAIK)

[patrickh99]

The turbo does add some complexity, expense, and potential pilot workload.

Maybe I should extend the cabin to make it a 6 seater, make the wing longer, and put in a TSIO-540 or a Walter M601 and call it an Expedition. Wait, this sounds familiar... :-)

...Just some creative suggestions for Chris...

[patrickh99]

Another alternative that I had been considering and was just reminded of by someone else, is the Mazda rotary, A 3-rotor peripheral port turbo'd rotary can fairly easily create 1000HP in racing applications. Yep, you read that right, 3 zeros. Build it for something less than that and de-rate it; the engine is almost bullet-proof.

You almost are required to use a turbo since the engine tends to destroy exhaust systems, especially mufflers, very quickly, due to the super-sonic exhaust pulses. And it is extremely noisy without one or the other. The factory exhaust actually has a fair amount of cast-iron; a little heavy for an airplane.

My thought process follows pretty close to some others I have talked to: I decided against the "alternative engine" option (at least for the initial engine) because I don't want to spend the extra year or two engineering and tweaking, plus resale on "alternative-engined planes" is fairly abysmal, if I ever do decide to sell. The other issues: the only maker of PSRUs specifically designed for rotaries has retired, and that PSRU did not have a constant speed prop option, unless you go with an electric prop, which presents other issues.

Maybe for my second engine...

[EricP]

The turbo does add some complexity, expense, and potential pilot workload.

Maybe I should extend the cabin to make it a 6 seater, make the wing longer, and put in a TSIO-540 or a Walter M601 and call it an Expedition. Wait, this sounds familiar... :-)

...Just some creative suggestions for Chris...

Wait, my friend has a WWII V-12 Allison laying around....

[Bdflies]

I vote for a Bearhawk with an Allison 250.

Bill

[lsa140]

I wonder how a 4 place Bearhawk, kept light, would do with a 215hp XP-400 from Superior.

[Chris In Milwaukee]

I have to imagine an XP-400 would be an outstanding engine for a Bearhawk. I seem to recall there are a couple of them being built with a 390 as well.

[JimParker256]

I've been travelling, and didn't have access to a keyboard, so waited to get home to post this... May be a moot point by now, but my biggest concern with using a TO engine would be the availability of 100LL or a suitable replacement a few years down the road, assuming the EPA gets their way (and they usually do). Swift Fuels is already distributing their 94UL to some airports (replacing MoGas, not 100LL from what I've seen), and high-compression engines cannot use it because of detonation / pre-ignition issues (well documented).

The FAA's 100LL program is now down to two competitors (Swift and Shell, both producing a 100LL replacement that is totally lead-free). There is one additional potential source - GAMI (Ada, OK) has also developed a 100LL replacement fuel, but chose not to take part in the FAA program, electing to pursue the STC route instead. All that sounds good, but I suspect that both 100LL and the replacement fuels will become significantly more expensive down the road. (Frankly, it was one of the things that caused me to sell my Turbo-Normalized Rockwell Commander 114 and accelerate the Bearhawk Patrol build...)

[patrickh99]

So the important questions then are: Will an Allison V12 run on 94UL? And is it for sale? :-)

If you are interested in the Superior XP series, see the attachments. You can buy and overhaul a run-out 540 for the same or lower price than the XP-400

[EricP]

I wonder how a 4 place Bearhawk, kept light, would do with a 215hp XP-400 from Superior.

I think this engine or the Lycoming IO-390 would be the best "bang for the buck" and give a better weight carrying capability. However, since the purchase price is high on these new engines we got a used Lyc IO-360 and are pretty happy with that choice. Now to get it flying!