Do you have any plans for altitude compensation? This seems like an awesome project

 

Planning a 3500rpm cruise, 4800rpm takeoff with approximately 94" prop. In order to be reasonably effecient it has to be constant speed, but I'm told by the prop guys it can be done fairly easily.

 

No forced induction, but the engine starts out with enough power that it will still go higher than I need to before the power decreases to the point that it's not practical. The original prototype of this airplane flew with 200 hp for takeoff and I figure I'll still have at least that at 9000ft.

Whatever SD computer setup I end up with will take care of mixture and ignition changes needed at higher altitudes.

 

My website is: http://home.comcast.net/~ogoodwin/Mustang.html

Several pictures along with links.

 

I'm very interested in this project. I got my A&P about 3 years ago. How do you plan on creating a table based on altitude and barometric pressure vs. MAP and IAT.

This isn't being sarcastic at all. I'm just wondering

 

Also, my background is a C-130 Crew Chief. We have Compressor inlet pressure probe hooked to an altitude compensator. All this is controlled by the Temp Datum system ( PCM for turbo props)

 

Yes, when you look at a R2800 (or even 4360) or Merlin, 540ci seems pretty small:-)

I have a vid of a LS1 powered airplane like this doing it's first flight, I'll try to figure out a way to post a link.

More information about a very similar airplane and the LSx conversion:
www.legendaryaircraft.com

 

This is a cool project...

I am working on my A&P right now... definitely keep up updated!

 

Actually a SD tune as done on an auto engine already compensates for baro and temperature. There's nothing new needed. Altitude compensation IS baro. MAP is baro. IAT is temperature. Altitude is irrelevant, since the engine only cares about MAP and temperature (inside the manifold) and rpm. I have a 8.1L Silverado that I drive all around the country from Kansas to Montana, from 700ft elevation to 14000ft. While it's not SD, it illustrates that altitude is compensated for by the computer.

So to answer your question, nothing extra need be done to compensate for altitude.

Anyway, your question didn't seem sarcastic at all:-)

 

This is a simple valvetrain setup your asking for in terms of something that works, problem there is nobody with the EXPERIENCE designing camshafts on here for this odd set of circumstances. 2000-5000rpm, 14" exhaust stacks with no collector, you need the best BSFC numbers and TQ production in this RPM range, Plus you put into the fray the extra need of to be 100% durable.

It's easily doable but it's not going to come from rectal extraction.

I would use the smaller port cathedral heads and a LS6 intake. My reason for that over the L92 setup is due to better BSFC for better fuel economy. A large valve is not needed here with the RPM range and discharge coef is much better with the smaller valve the 317 heads offer. The 317 heads will also make MUCH better TQ thru the RPM range your running in with a LS6 intake and not to mention you have the ease of a throttle cable setup for redundancy, something your not going to have with a throttle by wire.

I haven't sat down to design this deal yet, but my first thought would be a VERY small camshaft, much smaller than the suggestions given here. You don't need a lot of lift due to the RPM range and that RPM range is also lower than what any of the OEM motors are designed to run in, even trucks shift at 5600rpm!

Bret

 

Interest piqued

*subscribing*

 

Awesome, didn't know there were so many a&ps(or a&ps in training) on here! Today was my last day at A&P school (MIAT) and hope to have my writtens and o&p's finished by the end of july.Sorry to get OT buy i'm excited.

Oh yeah, some pics of this project along the way would be pretty cool.

 

cool project!

 

I argee smaller ports with just a little clean up best valves and springs you can buy

 

Every Lancair kit with a LS motor has had problems, at least the ones I have seen. It was mostly cooling problems. They all swapped to a regular aircraft engine.

This is a big mistake. Just put a IO-550 in it and enjoy! You'll save money in the long run. Granted they aint cheap! 30k+ just for the motor.

Plus, whats your plans for the rad and cooling?

What do you think the TBO on the L92 will be running at those RPM's? Your RPM limitation will be the gear reduction and prop size. What size prop are you planing on running?

I am not trying to pee in your pool. These engines are designed as car engines and not designed for low RPM power and high (3500) RPM cruise.

Yes, race motors are built to run hard and high RPM's but how long do those motors last? One racing season or a few races.

Plus if you have a power failure or power loss (battery). The motor will shutoff and not run! An aircraft engine has mags and will run with a total power failure. I would consider a back up battery just for the L92 PCM.

 

Actually with the ring pack changes and some tweaks to the valvetrain they can be run at high RPM cruise.

Honestly I think with a DA of 9000ft he can still make 300+hp within his RPM range limits.

Only thing I would think that would help would be a dry sump, so you can have fun in the thing!

 

I think it will be more toward 200hp at that DA.

He said a 94'' prop. Is that a two blade constant speed? Man that seems like a big prop. Will the Mustang take that size, even a tail dragger?

Plus with no 02's you could run 110 low lead and up the compression ratios, or turbo the hell out of it!

 

ya I would think that what need to be a must! I have no idea on plane stuff, but is any of them wet with a pan on the bottem?

 

BO185, thanks for your thoughts. Unfortunately, since this is a scaled down inline powered aircraft, it's not wide enough for an IO550. A lot of effort has gone into makeing is look right, so I'm not ready to surrender the clean cowling I can get from a V8 (plus the sound).

Part of the cooling problems with some aircraft (I suspect with the Lancair too) come from trying to fit the radiator in the cowling with the engine, then routing the air through it (behind the HOT engine) in a way to cool. Sometimes it works, but sometimes it doesn't. All the replica fighters (Spitfires and Mustangs mostly) that use liquid cooled engines use the same design for cooling as the originals: in the case of the P-51 the belly scoop works great. It allows for clean, cool air to flow through the radiator and it allows for a large enough rad to do the job. There are a number of V8s and V6s flying from aluminum 215 Buicks to 4.3 Chevy, 2.7 Suzuki, 350 small blocks, 351 Fords, up to 502 Chevy big blocks, including several LS1s. They all work if attention is paid to cooling (water and oil) and fuel delivery. This list, by the way, is ONLY P-51 replicas of various types. So there are quite a few out there.

About the rpm issue; I don't think 3400 to even 4000rpm for extended times will hurt these engines if they are cooled and oiled. Think of the boat engines running wide open throttle at sea level and 4000+ rpm. These things are putting out way more power than my engine will at the same rpm but with the reduced manifold pressure at 8000+ feet; probably on the order of 100 hp more in fact. As for TBO, that's anybody's guess. The original Packard V1650 used in the P-51 is only good for 500 hours or so (if you're lucky) so I guess I won't be too disappointed if it's anything over that, so long as the TBO isn't announced by a catastrophic failure:-)

I do plan for a standby battery for the PCM and fuel pump. This is something AFAIK everybody uses. It's not that hard to set up and it's worth it.

Maybe I'm wrong, but the operating profile I'm proposing just doesn't seem that severe. In most cases, it seems the weak link is the reduction unit. That's why I bought a Geschwender chain drive unit. These things have been on aircraft since the late 1970's and have been mostly unchanged. They have the reputation of being pretty much bullet proof, like the LS engines.

Again, I appreciate your thoughts, but I think most of the negatives you brought up are either airframe specific or have been worked around.

 

I did think about dry sump, but I don't like negative Gs well enough to worry about it. Any upside down stuff will be positive G or very brief negative. I plan to install an Accusump for that.