Auto Engine to Air Craft

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pictsidhe

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Jul 15, 2014
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Superchargers are nice in cars as they work from zero rpm.
My dad bought a small turbo car in the early 80s. It was decidedly lukewarm till about 2000rpm then all hell broke loose as the torque tripled over a few hundred rpm. T3 turbo on a 1.3litre ohv, no wonder it was laggy. An aircraft doesn't mind the peaky characteristic of a turbo as prop loading torque varies with the square of revs. Add in automatic altitude compensation and higher efficiency and the choice should be clear.
 

AdrianS

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Jul 5, 2014
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Australia
Or you could just use a turbo which make that all so easy and is more efficient to boot.
Yes, but where's the fun in that ;). Playing mechanical what-if is one of my hobbies.

Having said that, I would be happy to drive around behind a home-made CVT driven supercharger, but I don't know about flying behind one ( until someone invents a way of parking on a cloud).
 

rv6ejguy

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Jun 26, 2012
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Calgary, Alberta, Canada
Superchargers are nice in cars as they work from zero rpm.
My dad bought a small turbo car in the early 80s. It was decidedly lukewarm till about 2000rpm then all hell broke loose as the torque tripled over a few hundred rpm. T3 turbo on a 1.3litre ohv, no wonder it was laggy. An aircraft doesn't mind the peaky characteristic of a turbo as prop loading torque varies with the square of revs. Add in automatic altitude compensation and higher efficiency and the choice should be clear.
Today, with variable geometry turbos you can have peak torque down around 1400rpm and keep that figure to near redline. It just feels like a much bigger engine.
 

blainepga

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May 20, 2011
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69
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Queen Creek, AZ 85142
Hey Guys,

I will show you what I am putting in my grocery getter this week. I have a '97 Mitsubishi Mirage with 280 k miles on it and still gets 30 plus mph. I am not a turbophobic. I have customized a new 1.8L motor going from the stock 114 hp to 400 hp. Also a completely new drive train. It is internally adjustable from 8 psi to 30 psi. It has a new Crower cam, new aluminum adjustable rocker arms, and I am finishing modifying the intake system. The stock injectors are 214 cc's and the new injectors are 650 cc's. There is a new fuel rail for these injectors and a new fuel pump at 105 psi with a new regulator and auto fuel return. This regulator is connected to the intake manifold with a stock setting of 43.5 psi that will go up accordingly with boost pressure. The stock throttle body was a 53 mm and the new one is 80 mm and (It wouldn't let me use the word I wanted so here is the substitution) really neat, ha ha! This is just for fun. You know how it is when you are getting on the freeway and the guy behind you decides he is going to go around you and cut you off. Well, all I want him to see are my tail lights, and then ask him how he likes his 80 k BMW or whatever.

Anyway, I will post some pictures this week. This doesn't have anything to do with my airplane, just thought I would let you know.

I do have the software to modify the ecm for this application. The ecm and tcm are in the same module.
 

blane.c

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Jun 27, 2015
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capital district NY
An opinion...

Superchargers are what's known as positive air displacement devices, they turn at a given speed and each revolution displace 'X' amount of air. That's fine when at sea level but when you go up into thinner air then the volume that is displaced is reduced accordingly (because the air's thinner) so you might have say 8psi of boost at sea level but that might be reduced to 2 psi of boost at 5000 feet (whatever). Also note under load a supercharger can not produce more psi than the driven speed allows.

A Turbocharger relies on exhaust pressure that is usually in excess of what's needed to spin the turbines so if you have 8psi at sea level, the exhaust has enough excess energy to continue to speed up the turbo's turbine to continue to maintain that 8psi at 5000 feet (whatever).

Also under load and even at low rpm, the exhaust pressure is still increased by greater cylinder pressures to provide high levels of boost that a supercharger can not as it's limited by the driven rpm.

Just a suggestion but for these reasons you might consider changing to a turbocharged version that is far more suited for flying, possibly the supercharged's internals are the same.

If at all possible could you weigh and display?
I flew behind P&W supercharged engines and the superchargers work just fine. They also had "pressure carburetors" which were in many respects early throttle body injectors.
 

cheapracer

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Sep 8, 2013
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Australian
I flew behind P&W supercharged engines and the superchargers work just fine.
They flew terribly and you were lucky to get out alive! ... I never said.

If there is something technically incorrect with what I wrote, your submission is most welcome.
 

blane.c

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capital district NY
Well on the P&W's it was easily possible to over boost the engines at takeoff unless you had a very high density altitude. In fact if you didn't know what you were doing over boost could be virtually guaranteed. Generally you had to worry about over boosting until somewhere around 13,000ft. Of course with a waste gate that concern goes away. As far as inefficiently wasting power driving the compressor just to vent the air, that would be true certainly at takeoff but after reducing power for climb could at worst be mitigated and with some thought about the power actually needed, most likely for normal circumstances eliminated. Keeping essentially a stock setup except for the pulley and waste gate at the expense of having to do a little thinking seems like a prudent approach. The normal power needed for climb could be worked out in advance for several density altitude scenarios and printed on a chart. Since you have a waste gate in an ab-normal or emergency situation just let it vent the excess pressure and drive.
 

blainepga

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May 20, 2011
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69
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Queen Creek, AZ 85142
The responses I have received on this post have generated more conversations than I anticipated. Please keep sending your opinions because the more information we have leads to better execution of a project like mine.

Thank you,
Blaine
 

cheapracer

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Sep 8, 2013
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Australian
The responses I have received on this post have generated more conversations than I anticipated. Please keep sending your opinions because the more information we have leads to better execution of a project like mine.

Thank you,
Blaine
Exactly Blaine, that's what forums should be about.


Definition of forum
plural forums also foraplay \ˈfȯr-ə\

1
a : a public meeting place for open discussion The club provides a forum for people interested in local history.c : a medium (as a newspaper or online service) of open discussion or expression of ideas


3
a : a public meeting or lecture involving audience discussion The town has scheduled a public forum to discuss the proposal.b : a program (as on radio or television) involving discussion of a problem usually by several authorities
 
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