Turbo 4cyl build thoughts

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Bradsopex

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Hey all I have been mulling this over for a while and want to see what kind of thoughts many of you have. But first, some thoughts of mine. Correct me where applicable.

I'm an engineer, GA pilot, and part time race car/engine builder. I have built engines for time attack and endurance racing. As an engineer, I have worked with certifying components to meet FAA and military standards for EMI and environmental effects (temp/altitude effects, vibe, etc). I also worked designing systems for military aircraft.

I have been interested in auto conversions for quite some time. As a GA pilot, I am constantly astounded at the cost of a lot of the items associated with the plane. However, I do understand it. The GA industry is in a vicious cycle where the low volume (and high certification costs) mean they need to charge a premium for their parts. However, the cost keeps people from getting into aviation, therefor keeping the volume low. Given the capability of so many things you can obtain cheaply today thanks to advancements in manufacturing and other technologies, there is no reason for it to cost a small fortune to keep flying.

That being said, after lurking around the forum for a bit I think some are confused as to what the auto conversion should be. Many seem to get into looking into it thinking that the initial cost would be much cheaper than a certified engine. In some cases that can be true, but in many others you can find a used certified engine for the same price as modifying an auto engine. For me, the trust allure to it is the cost savings when it comes to overhauls, maintenance, and operating costs. I'm planning on doing a lot of back country flying, and being able to get an emergency part from an auto parts store and gas up at any gas station is just so tempting.

That being said, I have an engine laying around that I have quite a bit of experience building up. My HP goal for flying is 120-180, and this will be going on a Kit-Fox style fuselage. The engine from the factory makes around 115 @ 5800 RPM. That just wont do.

I have built one of these engines in the past that would get me to 200hp and 140 ft/lb of torque at 3500 by throwing a turbo at it (and a few more modifications). I can get even more if I wanted.

I am thinking of building it for higher power, but only for the purpose of getting respectable numbers at a more manageable RPM so I'm not revving the crap out of it at cruise.

My biggest question at the moment, is where can I find a decent reduction drive? I COULD make my own as I have the equipment, but the money I would sink into building, testing, and breaking units just to end up pulling out my hair doesn't seem worth it.
 

Vigilant1

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For a PSRU to work at 120-180 HP, I think I would look at the units available from Aeromomentum and from Airtrikes. Take a look at their web pages, see if they meet your requirements.
 

dino

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Skytrax psru on a yamaha RX1 or Apex sled engine
 

Chris Matheny

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Where are you located? I am in the process of just what you are talking about and have the redrive all machined and should be ground testing this spring/early summer. With this package, i'm aiming for 150hp and 250# FWF (or less) weight running.
 

xwing

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have no idea about suitability but i think there is some pentastar activity that has been going on here & from that, followed a link to
https://www.motorreviewer.com/engine.php?engine_id=168

https://www.homebuiltairplanes.com/forums/threads/2016-pentastar-engine-worth-considering.32918/

https://www.homebuiltairplanes.com/forums/threads/2016-pentastar-engine-worth-considering.32918/page-2#post-517917

lotsa autoconversion history here
https://www.homebuiltairplanes.com/forums/#auto-conversions.16

Prob be good to have a dedicated turbo forum but easy enuff for someone to start that thread.

My 2c is start with an engine designed for a turbo from the outset.
 
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Bradsopex

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I just realized I have an old Toyota 1UZ-FE in my shop. That motor was twin turbo'd and then certified by the FAA as the FV2400-2TC. I don't have many specifics, but if I want to go with something larger than the bush plane I am planning, then that could be an option.

As for starting with a turbo engine, I am thinking about using a Toyota 4AG-E. Toyota supercharged these from the factory as a 4AG-ZE. The major differences were oil squirters for the pistons, and I believe extra ribbing in the casting of the block for strength. Either way, having built 600hp motors that were not turbo from the factory, I'm not terribly concerned. Engines are something I know well, I'm mostly trying to figure out the variables of taking those engines and putting them in a completely different application.
 

Chris Matheny

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The thing most non performance EFI people don't realize is you can make 600hp reliable in an application or you can hurt the same engine and parts with a 300hp tune up. There can be a safe, soft tune and there can be an aggressive parts wrecking tune and both can look the same on a dyno graph.
 

pictsidhe

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I would stick to stock power and torque if you want it to be reliable. Modern car engines are built to take full power for hundreds of hours. Just what we need. Yes, you can boost the hp way up, but you are very unlikely to have an engine that will take sustained high power for hundreds of hours as stock car engines will. Cars are very, very rarely run at high power for long unlike aircraft. Hence being able to have sizeable hp gains and still be reliable. Germany has some nice autobahns, but even they are of a finite length, when you are driving at 150mph+... Pick an engine that already has the requisite parts and engineering done. You could swap a supercharger for a turbo, but stay inside the stock torque and power to keep longevity.

You are right to be intimidated by the redrive. FWIW, people have had good results with Tracy Crook and Marcotte redrives. But, you may still need to tweak them to deal with TV issues. Ross, aka rv6ejguy, runs a Marcotte on his Subaru.
 

cheapracer

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I am thinking about using a Toyota 4AG-E.
Too heavy, if Toyota fan, start with a common 1ZZ, larger 1.8 and lighter.

Another lightweight is a 2.0 Ford Duratec/Mazda L (Ford Fiesta,Mondeo - Mazda 3/6). lighter than a 4AG-E, and they can be found commonly in Ford turbo form, i.e. the Ecoboost.
 

Bradsopex

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I would stick to stock power and torque if you want it to be reliable. Modern car engines are built to take full power for hundreds of hours. Just what we need. Yes, you can boost the hp way up, but you are very unlikely to have an engine that will take sustained high power for hundreds of hours as stock car engines will. Cars are very, very rarely run at high power for long unlike aircraft. Hence being able to have sizeable hp gains and still be reliable. Germany has some nice autobahns, but even they are of a finite length, when you are driving at 150mph+... Pick an engine that already has the requisite parts and engineering done. You could swap a supercharger for a turbo, but stay inside the stock torque and power to keep longevity.
The point of upping the horsepower is so I can run the engine at lower RPMs for the desired HP. A 300-ish HP motor at 5800 RPM is a 150 HP motor at about half that. The engines I built endure numerous 14-24 hour races plus test sessions in between tear downs, and so far those have been preventative. The longest I have gone between tear downs is 500 hours, and the only items I had to replace were due to me tearing into the motor, not any organic failure. Most people's performance engines aren't built for that, but mine were endurance focused.

My engine builds HAVE to be focused on power and longevity, otherwise they wont survive 24 hours straight of near redline performance. That being said, I am essentially over-building to keep the reliability and shift the power/torque curve lower in the band to make it usable for this application. For this build, I'm aiming for a target RPM of mid-3K that's where most engines are designed to "cruise". Upping the HP means I am increasing the heat load at any given RPM. Properly managing heat is the key to building a long lasting, high-HP engine. Sure, there are other forces at play, but those are mitigated during the build process. If I can manage the heat, the engine will last. Now I have to balance cooling, which to me is the trickiest part of these auto conversions. I have to provide adequate cooling without risking temperature shock induced fatigue. I can manage this by utilizing cowl flaps and a few other things. I can make a system similar to others I have made in the past to allow airflow over the heat exchangers based on coolant temp, and allow air flow around the engine based on ambient temp around it. This will automate it and prevent pilot task saturation, which will lead to pilot error and cause an engine failure.

I understand a lot of the thought process many have concerning auto conversions and useful power, but in my experience I find most of it a bit misguided. Could I end up being wrong? Absolutely. Has anyone done it this way? Maybe, but finding that documentation isn't proving easy. I have been looking at this for years, and just decided to bite the bullet and try it. Either it succeeds, or it fails. As long as I am smart, I can test this safely.
 

Bradsopex

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Too heavy, if Toyota fan, start with a common 1ZZ, larger 1.8 and lighter.

Another lightweight is a 2.0 Ford Duratec/Mazda L (Ford Fiesta,Mondeo - Mazda 3/6). lighter than a 4AG-E, and they can be found commonly in Ford turbo form, i.e. the Ecoboost.
Yeah, weight is a concern but as it sits now, it is 7 pounds lighter than an O-360. I will be using a carbon fiber air intake which will shave some weight, and a few other things will be composite where able. I chose that motor because of the cast iron block. Cast iron has some neat vibration dampening characteristics you wont find in aluminum, and that helps with the longevity issue. This does add to the complication of cooling, as cast iron isn't too fond of thermal shock, but in my response above I mentioned some methods I'm considering for cooling management. The reason I picked the 4AG is because, well, I have 3 at the shop. I have experience building them, and getting one to 300-330 hp, reliably, is pretty trivial with my experience. There are lighter engines, and the Duratec would be a solid pick (tons of aftermarket support), but for this first go around I want to stick with something I know. Really I'm just wanting to test out how reliable I can make it at that power to prove the concept.

Mike Patey is doing some fun stuff with a Carbon Cub right now that is similar in thought process, but he is using a 500hp aircraft race engine.
 

pictsidhe

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What races hold an engine at the redline? Every one that I am familiar with involves acceleration, then braking throughout the race. That makes a big difference to thermal stresses.
 

Bradsopex

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What races hold an engine at the redline? Every one that I am familiar with involves acceleration, then braking throughout the race. That makes a big difference to thermal stresses.
True, the time at redline really depends on the track. When racing, the engine is constantly accelerating or decelerating, each time you shift a gear (up or down), you are at redline. On the longer straights, depending on how we adjust the gearing, it spends a good amount of that at redline. It can be argued that heat cycling the engine is more damaging than holding it at a steady state in high RPM, but then you open some other can of worms.

Either way, the purpose of my design is to not have to redline the engine to get good performance, but be able to have it around 5500 for climb out, then settle it in around mid-3K for cruise. People are so used to the idea that if you run an auto engine you need to redline the crap out of it because that's where the power is. However, running an engine with more power stock isn't always feasible due to weight. So to me, the logical answer is to give the smaller engine more power.

The most common failures of race engines (really any engine) comes down to failure of cooling or lubrication. I mentioned some of the cooling considerations, and for lubrication the engine internals get WPC treated and the wet sump system is being replaced by a dry sump. Next you have head gasket, and I will be running a multi-layer steel gasket to mitigate any failure there. It will fail, eventually, but I'm hoping to get plenty of hours out of it and make replacing that part of the regular overhaul. Another issue of running hot constantly are valve springs, especially with higher RPMs. Depending on the material, prolonged exposure to high RPMs can cause them to heat to the point where they soften slightly. This can lead to valve float, which will destroy an engine. That can be addressed with stiffer valve springs and titanium retainers. Everything else in the engine fails due to poor lubrication. Bearings, rings, etc.

I do want to say I don't recommend anyone grab a 100hp auto engine and run the piss out of it, because it WILL fail fairly quick. I am suggesting the thought process of using an engine that is more than you need so you don't have to redline it. You don't have to consider that with aviation engines because they rate the power at the lower, more usable RPM so there really isn't any guesswork associated. With this, I will essentially need to build the engine, dyno it, and see what it makes at the RPMs I want to operate at, and then adjust from there. It's an iterative design process, but I am hopeful. I won't know exactly what power I need until I build the airframe and weigh it, and that will drive a lot of the build decisions with the engine.
 

pictsidhe

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Power is not the problem, reliability is. You need to build your engine, then leave it run at 75% for several weeks then strip to see how it fared. If you just do a few quick pulls, you are probably going to have problems in the air. Running at 75% for hours is very different to car racing and a lot more punishing.
 

cheapracer

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Running at 75% for hours is very different to car racing and a lot more punishing.
Yeah, nah.

The belief that bespoke plane engines have magical pistons, conrods and crankshafts, and are the only type that can run all day at "75%", is , as the word "magical" suggests already, is just fairy tales.

The auto-conversion issues are commonly with PSRU failure, PSRU causation, or poor ancillary adaption by amateurs, but nothing to do with the core engine itself.

You can not offer evidence of multiple and consistent failure of major core auto engine components because they just don't exist.

I still don't understand why aviation people want to continually damage their own hobby by shunning rather than encouraging viable, economical options.

This, from the 1950s ....
 
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