REFLECTOR: FW: Brian's Turbo

Sat Jan 15 12:53:03 CST 2011

Chuck,

You're right about the good way to do it but mistaken about what is normal for aircraft engines.  Unless it is a FADEC, certified aircraft injected engines don't reference MAP.  Even normally aspirated engines would benefit from referencing MAP instead of going richer with increasing altitude.  There is a technique for leaning during climb that involves keeping the EGT the same as it was at sea level.  This means that the gas air ratio remains the same from takeoff to cruse altitude (12% rich of peak power).  I have used this trick and had no increase in CHT or oil temperature. The benefit is less fuel burn and faster climb.

Larry Coen,
N136LC

From: Chuck Harbert 
Sent: Friday, January 14, 2011 7:42 PM
To: Laurence Coen 
Cc: Bob-velo turbo Jackson 
Subject: Re: REFLECTOR: FW: Brian's Turbo

Doesn’t sound right that fuel flow would remain high if the compressor hose came off.  There are really only 2 good ways to TC-electronic or mechanical fuel injection, both of which normally reference MP (actually our drag boat engine was supercharged and the fuel flow was only mechanically controlled w/o MP reference). A mass airflow sensor can be used, but are more complicated than a MAP (manifold absolute pressure). I used a locking pin arrangement for all my intake hoses and exhaust pipes, just so that nothing could come off. I also have a low pressure vacuum breaker installed just ahead of the servo, which will open automatically if the turbo is blocked. I check it regularly, by blocking the intake scoop. It won’t handle high rpms, but is good for up to 2,300 rpm which is enough for me to get down safely.

Don Rivera at Airflow Performance designed and built my fuel system to flow enough for 35” MP. Because my HIO-360 was from a helicopter, it had a MP sensing servo which could handle a slightly higher flow due to 35” MP. My intent was to use it for t/o, especially at high altitude airports. It’s a mechanical system with slightly larger turbo jets. 

I’ll take your advice and send Brian a note. Thanks.

Chuck

From: Laurence Coen 
Sent: Friday, January 14, 2011 10:56 AM
To: Chuck Harbert 
Subject: Re: REFLECTOR: FW: Brian's Turbo

Chuck,

Brian tends to over engineer things if anything.  I don't think he would feel you'd be "butting in" by passing along your experience with turbo charging.  I'm not a turbo guy but here's something that should interest you.  One of the online aviation publications carried story about a Cirrus driver that had the compressor hose come off in hard IFR.  The fuel flow remained unchanged but the air volume dropped and flooded the engine causing a total loss of power.  Even after leaning,  only two cylinders would fire.  He made a successful emergency landing.  He re-attaching the hose and tightened the clamp that an AP forgot plus cleaning the plugs and he was back on his way.  It occurred to me that if fuel flow was regulated by manifold pressure instead mechanically, when he lost boost his engine would have gone to normally aspirated and continued to make useful power.

Just the thoughts of a mad scientist. 

Larry Coen
N136LC

From: Chuck Harbert 
Sent: Thursday, January 13, 2011 6:06 PM
To: Laurence Coen 
Subject: Re: REFLECTOR: FW: Brian's Turbo

Thanks, Larry.

I’ve never really worked on a Franklin, except Hiroo’s plane a little, and some advice on fuel injecting one a few years ago. My goal with the email was just to impress the importance of getting all the information you can by talking with people who are experienced with doing this. I basically was turbo normalizing my HIO-360, but ran into some unexpected problems, and I’ve done several turbocharging applications. Air cooled airplane engines are not as easy to TG or as strong as most automotive engines, so you’ve got to be very conservative. I was using a manual wastegate, and a PRV set to a max MP of 34.5” which I would use primarily for takeoff, since I have a Catto cruise prop. I thought I had a big enough wastegate at 2.75” which showed no boost at 2,300 rpm during taxi testing, but when it got above 2,400, it rapidly started making boost even with the wastegate open. I’m using a TO-4 which doesn’t pass as much exhaust gas through the turbine as a TO-6, but it is smaller and lighter. I’ll have it back in the air by summer. 

The HIO-360 is a 2,900 rpm max engine with heavy duty components to stand the higher rpms, plus I’ve had it blueprinted. With the fixed prop, at 2,900 it would truing at over 200 kts, which was the plan. 

I was concerned that Brian may not be aware of some of the things that are likely to occur with a turbo setup, such as:

1. Much higher heat inside the cowls. I coated the inside with fire proof paint which blistered, so I added fiberfrax with aluminum tape over it-worked well. 

2. Higher oil temps which necessitated a second oil cooler which was placed on the top of the engine cowl with a 3” factory scoop which allowed TG heat to escape while taxiing or shutdown.

3. I assume the 3” Bosch throttle body is for an electronic fuel injection system. My original engine was a Mazda 20B (3 rotor) TC which used a aftermarket fuel control which referenced both MAP and incoming air temp at the throttle body. It was too heavy (450#) and fuel burn was horrendous as it could make 400hp, plus it was also a big heat maker. The ignition also referenced these 2 critical functions. 

4. You need to monitor not only the intake manifold pressure, but also the exhaust manifold pressure, to be sure they are roughly the same, as you could blow the seal between the turbine and compressor allowing bearing oil into the engine resulting in immediate detonation and engine failure. I have a dual (twin) engine MP gauge that shows both of of these which is easy to see.

5. All the incoming air comes through the compressor which could be blocked a number of ways. He should have a alternate air valve downstream to allow air into the engine if this were to happen. 

I would send this to Brian, but I don’t want to “butt-in”, but I’m concerned that it could go badly for him if he hasn’t taken steps to address these items. Do you know him and what level of knowledge he has on TC’s? 

Chuck Harbert
206-499-5990

From: Laurence Coen 
Sent: Thursday, January 13, 2011 12:39 PM
To: Chuck Harbert ; Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: FW: Brian's Turbo

Chuck,

The point that I was making was that the 10.5:1 CR was not a modification but a standard Franklin engine.  Your point that turbo normalization is not simple or should be taken lightly is well taken.  Normally aspirated or turbo the engine specified limits may not be exceeded.  While the Lycoming CR is 8.5-8.7 the CHT limit is 460F to 500F, the 10.:1 CR Franklin CHT limit is 392F.  Both are within limits. You don't need a turbo to wreak your engine.  I have a normally aspirated, carbureted Franklin and if I leaned for peak power and pulled on carb heat for takeoff I'd never get out of sight of the airport with out the engine self destructing. 

Your statement about what happens at 15000' is correct if you choose to climb at max power but if it was me, once there, I would likely reduce manifold pressure to 20" and go lean of peak.  Now were talking 5" boost not 15".  The turbo gives you a different way to destroy your engine but doesn't mean you have to.  

I think you did an excellent job of educating the group as to the complexities of turbo normalizing and the increase in the operational aspect asN136LC

From: Chuck Harbert 
Sent: Wednesday, January 12, 2011 3:36 PM
To: Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: FW: Brian's Turbo

Actually, it does slightly increase the detonation risk, unless you can cool (intercooler) the incoming charge from the compression heating at higher altitudes. Roughly, for every lb of pressure increase, you add 11 degF temperature increase (or about 6 degF for 1” of manifold pressure). Since the lapse rate is about –3-4 degF per 1,000’, you get a net temp increase of 2-3 degF/1,000’. At 15,000’, you’ve lost about half of sea level pressure (or -1” of mp/1,000’), so to normalize you need to compress the incoming (cold) air about 15”, or a net temp increase of 30-45 degF, which the intercooler should handle. 

Turbocharged engines use extra fuel to cool the incoming charge and to keep the CHT’s down, especially in climb. Lycoming and Continental also call for reduced ignition advance (25deg  BTDC to 20 max) on a much lower compression ratio engine (7.0-7.5 vs normal 8.5-8.7). The 10.5 CR engine is a high performance version that can detonate much more easily than a lower CR engine, especially we boosted. Detonation is a very bad thing which can quickly destroy an engine.

Also, the thinner air at higher altitude does not cool the engine (nor the incoming heated charge through the intercooler) as well as sea level air. Finally, for aftermarket installations, you must be careful to avoid high CHT’s from inadequate waste gate sizing. If you are using a TO-6, it will produce a lot of air volume which is controlled by the waste gate. Too small, and you will back up (pressurize) the hot exhaust gases in the exhaust manifold, plus you could overboost (over turbo normalized) at higher rpms. The spec on TC’s is no more that 1-2” pressure differential on the turbine side vs. the compressor side, and just using a blow off valve (aka PRV) to control pressure on the intake side is not a viable solution. You need to make sure that the waste gate is large enough to not make any boost at full throttle sea level rpm (for turbo normalization).

I recently found this out on my turbo installation when the pressure in the exhaust manifold was 45” and the CHT’s were in the high 400’s above 2,500 rpm. I am signicantly increasing the size of my waste gate. Another problem I had was a fuel flow restriction through my aftermarket Fram racing fuel filter which I subsequently found out was rated for 12-14 GPH when I needed over 20 GPH. I don’t know what you’re running for an ignition, but make sure it is designed for referencing MAP (manifold absolute pressure), so it will not over advance the engine. The same is true for the fuel delivery system. 

I raced supercharged drag boats in my early days, but I found out turbocharging is much more complicated. When done right, it’s awesome, but if not, it can be very dangerous. Good luck.

Chuck H

From: Laurence Coen 
Sent: Wednesday, January 12, 2011 12:17 PM off valve 
To: bobj at jaxtechllc.com ; Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: FW: Brian's Turbo

Bob,

10.5:1 compression is standard for a Franklin so turbo normalized does not increase the detonation risk.

Larry Coen
N136LC

From: Bob Jackson (Jax Tech) 
Sent: Wednesday, January 12, 2011 8:24 AM
To: 'Velocity Aircraft Owners and Builders list' 
Subject: REFLECTOR: FW: Brian's Turbo

Looks like a very nice layout, Brian -- I like the compact, minimal induction plumbing design achieved with the way you've located the intercoolers on the bottom of the cowling near their cooling inlet airflow.  Are you concerned about having the turbo sort of 'trapped' in the relatively dead airflow space between the engine and firewall and with transferring it's heat out of the engine compartment efficiently?

I assume that since it's a single turbo, then there's a single wastegate bypass type arrangement near where the exhaust from each side funnels into the turbo, correct?  Any photos handy of the inside layout?  Are you concerned about increased detonation risk with the high compression cylinders?  How will you manage that risk?

Thanks for the info and photos,

Bob Jackson

N2XF

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From: Brian Michalk [mailto:michalk at awpi.com] 
Sent: Monday, January 10, 2011 12:22 AM
To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Brian's Turbo

There's lots of information to address your questions.  I'll start on them, and send them out as I get time.

  1.. Basic engine design you started from 
    1.. It's a stock Franklin.  6A-350-C1R, 10.5:1 compression.  I had the idea that someday 100LL would go away, so with the turbo in there, I could convert to low compression pistons and perhaps reprofile the cam to better suit turbo operation. 
  2.. Performance and functionality objectives for your improvements 
    1.. Turbo normalize only.  I'm not looking to exceed TBO horsepower. 
  3.. Single or dual turbo?  Piping layout for the turbo(s), wastegate and exhaust pipes 
    1.. Single turbo.  From memory, I believe it's a T06, Airresearch. 
    2.. Intake air 
      1.. armpit scoop from the pilot side 
      2.. Bosch 3" throttle body 
      3.. turbo situated slightly to the right side such that axle is pointing right at the armpit scoop, and the compressed air exits center of the firewall, pointing down 
      4.. Intercoolers.  Two RJR (I think) motorcycle intercoolers welded to a center plenum that goes to the turbo.  Air makes a right angle turn out each side of the intercoolers towards the outside. 
      5.. intake manifolds that pick up from the intercoolers near the firewall an go the all of the cylinders aft.
      The intercoolers get a fairing so it's all smoothed out.  Not shown in the pics below.

On 01/07/2011 08:05 PM, Bob Jackson (Jax Tech) wrote: 

Brian,

Maybe during the break while you're waiting for parts you could take a little time and post some info (and photos?) on your turbo work.  Unless of course it's something you'd rather not share for business reasons, etc.  Here are some facets that at least I would like to know more about:

  1.. Basic engine design you started from 
  2.. Performance and functionality objectives for your improvements 
  3.. Single or dual turbo?  Piping layout for the turbo(s), wastegate and exhaust pipes 
  4.. Inclusion of any induction over-pressure, or alternate air valves?  Do the intercoolers have special cooling air inputs? 
  5.. Automated wastegate/throttle controller design concept and some implementation details (the version you want to end up with), i.e., the 'linear stages', 'embedded controller', etc..  Does the design also involve mixture control? 
  6.. Primary electronic fuel injection system -- part of the starting point, or something you designed?  More design detail? 
  7.. Any details on the electronic ignition system, if other than standard magneto 
  8.. Overall engine cooling airflow concept and unique layout details 

As someone (Jim Agnew?) used to always say on the Reflector -- 'curious minds need to know'!

Bob Jackson

N2XF

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From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Brian Michalk
Sent: Friday, January 07, 2011 5:54 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fixes for Stick Slop

Great questions.

I installed the turbo, and ran the engine with wastegate wide open.  The performance was 50RPM static better than a carbureted/magneto Franklin with identical propeller.  I am very happy with the performance.  First flight I calculated a 20 degree climbout angle.  I was at 900 feet when the engine failed, about 2500 feet from where I took off.  I don't know what that is in FPM, but I got there stinking fast.  I kept pulling back on the stick to keep from overspeeding the engine.  The plan was to increase prop once I reached 1000 feet.

The initial configuration was a bit complex, so this second time I am removing complexity and will add back those features later.
To control the wastegate and throttle, I built some linear stages, actuated via an embedded controller.  This could be overriden by the pilot by using the friction lock on the knobs.  These stages have been removed, and I'm waiting on a new set of throttle/turbo cables from AS&S.

Since the primary fuel system is electronic injection, I fabricated from scratch a completely redundant injection system.  It actually performed quite well, but tuning on the ground is difficult.  I am removing the automated actuating part of it, and am instead installing a needle valve that is manually operated from the pilots position.
The original backup EFI is nice, because in an emergency, it monitored for a power failure and engaged on that event, or a pushbutton.

At this time, I am gated on several things.  The cable install really needs to happen before I mount the intercoolers, which prevents induction or cowl work.
Wings are ready to mount, but we are waiting on primer.

I think three weeks after the parts are in that we'll be ready for an engine start.  Optimistically, I'm saying March for another flight, but reasonably would me more like June/July.

I checked the runout on the crank, and was very pleased to measure .0005" TIR.  The manual says I'm allowed .008" so that's pretty good.

On 1/7/2011 4:17 PM, Bob Jackson wrote: 

Sorry, Brian!

I forgot about your first flight adventure.  Don't feel bad, almost all of us have done something.  I had engine problems (turned out to be my own engine control mis-management) and ran off the end of the runway when doing simulated power off landings.  And my A/C partner collapsed the nose gear (poor technique and a suspect weld) and slid down the runway a 1000 feet grinding away the bottom of the nose!

I'm sure your fix would do the job, I'm just concerned about the small-area steel-to-aluminum contact space.  But probably for no reason.

I remember you also had a pretty fancy turbo design.  How is that working out?  When do you think you might get back into the air?  We fiddle-farted around for ten years to complete, then another half-year off repair the hole in the nose after the NG collapse.  Nobody likes the 'when are you going to fly' question!

Thanks for all you do operating and maintaining the Reflector,

Bob

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From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Brian Michalk
Sent: Friday, January 07, 2011 4:20 PM
To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fixes for Stick Slop

I think it's safe to say I have about .05 hours of airtime on it.

That would be the first flight, and subsequent off field.  However, over years of airplane work, it's been tight.

On 1/7/2011 12:35 PM, Bob Jackson (Jax Tech) wrote: 

Nice design and approach!  How many hours do you have on it?  

Don't you still have concerns about the effect on the softer aluminum of the hard steel bolt?

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From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Brian Michalk
Sent: Friday, January 07, 2011 1:02 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Fixes for Stick Slop

There has been little discussion on a fix.  My solution involves making a saddle, I'm not sure if it's what the factory does or not.

I think the tubes are 1/2", so I bought some 1/2"ID, .25" wall aluminum tube.
With about 2" of stock, I first machined a flat on opposing side, leaving about 1/8" thickness.
Next, cut the tube in half along a plane parallel with the two flats.
Take the two halves, and place them flat to flat, drilling a hole for the bolt.  The tubes can now be cradled in the saddle.

The flats help support the torque transmitted to the two tubes at right angles.  For extra smoothness, use a thin teflon washer(or sheet) between the flats.

On 1/7/2011 11:13 AM, Bob Jackson wrote: 

We've been flying for a couple of years and now have 300+ hours on the plane.  When we started doing some formation flying recently I began to be aware that we're developing stick slop -- it's not what you want flying close formation, or when landing or anytime you need small corrections and fine attitude control.

When we built the plane we were leery of the standard steel AN3 bolt that joins the bottom of the aluminum stick stub and the aileron/elevator torque tubes) -- even when improved with the U-shaped steel reinforcing collar that the factory started shipping.

In our case, we know that nearly all of our stick slop comes from this mechanical connection between the stick's torque tube and the aileron and elevator torque tubes.  We've been on the Reflector for 12 years, but haven't heard much, if any talk about this problem and improvements that builders have made.

The question is:  do any of you have good fixes for this connection that eliminates stick slop?

Thanks,

Bob Jackson

N2XF

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