Q1_Aircraft: Onan 22 HP modification info??

Anyone out there know what QAC did to bump up the Onan from 18 to
22? I know the heads were milled...don't know HOW much...does anyone??
Were there subsequent reliability issues???

Thanks for considering the above,

Nick L.

I dont know what they did, but I do know that the heads they were peddling had a
lot of problems, you can not really do too much compression on a flat head, and
they did.

Actually they didnt bump it rom 18 to 22, the Onan came out as a 20 HP already
so they bumped it up 2 and some figures says 2.5 hp, to 22.5 hp.

There are a lot of better ways to go for power, rather than overdoing the
compression ratio. That is not to say that you can NOT rise the compression
ratio, but you can not over do it.

So please raise it, but just be a bit moderate when you do it. You WILL
benefit from it, and it will get you a bit more performance, However, you will
get the real performance in another way, I will get to that later.

To know what you are doing, you need to have a pipette, a measuring glass, a
piece of flat plexiglass with a small hole in it.

The head have the 'dead volume' you need to know, and you turn the head upside
down, (cooling fins down) on the table, put the head gasket on it, and on top of
it all, you put the piece of plexiglass with the hole in it.

Measure how much liquid you can put into the hole, filling the head with
liquid with the pipette. (alternatively, you can fill the same space with
chidrens clay, and dip it into a measure glass, the difference in liquid the
clay is displacing, is your head volume)

Ok now you know the volume of the head, take that number and set it aside.

An engine that is marked as a 1600cc or a 48 cu inch or whatever, seldom is.
Usually that is the number that is closest, and is the 'work number'.and in this
case you need to know the exact swept volume of the engine.

Take a caliper, calculator, pen, and paper, and you are set to go.

Measure the exact bore (the Diameter).

Measure the stroke (Length of the cylinder) from TDC to BDC.

Ok now you take the Diameter, and take half of that, (Radius)

Work all your numbers into this equation:

Radius X Radius X 3.14 X Stroke, and you will have the cylinders swept volume.

You will not get 48 Cu Inch or close to it, because the designation 48 Cu inch
is for the whole engine ( that is two cylinders) , so just stick with the number
you have, it should be in the vicinity of 24 Cu inch if you did it right, but it
is important that you work with the exact number.

Ok now you are sitting on two pieces of information, the dead space you have
on top, and the cylinders swept volume.

Add the SWEPT VOLUME, together with the DEAD SPACE ON TOP, and you will have
the TOTAL Volume.

Take the DEAD SPACE ON TOP, and see how many times you mathematically can fit
it into the TOTAL VOLUME, and you will have your compression ratio.(Total
volume, Divided by dead space)

You should with a standard 20 HP be around 7 to 1.

Go up a bit, I would recommend to shave them to 7.25 to 1, and would start to
be a bit nervous around 7.5 to 1.

Buit as I said, there are better ways to make the Onan get a dragonbreath.

Make a 3 angle valve job, undercut the valves, and do a very good porting on
the engine, ( the ports are in the block, when you do the porting, just don't
run through with a sand paper, and call it a porting job, this is a time
consuming job, and may very well take you an hour or more with the right tool,
per port).

Install the heads, with a couple of bolts, and tighten snug, on top of the
valves put a bit of childrens clay, and rotate the engine. The valves will make
an imprint on the childrens clay. Handle the chidrens clay very delicately, cut
it up with a razorblade, and measure the closest distance the head have to the
top of the head.

Scribble that number down, and take out the camshaft.

You need to first see a machine shop, to take of some of the meat on the
camshaft in order to make it possible to regrind the cam.The shaft and the cam
have almost the same diameter on the camlobes lowest spot, so you need to slim
it down a bit the shaft itself, (not the lobes, the material between the lobes)
so another profile will be possible.

Ok, now you have the cam in your hand, and you are ready to go to the
camgrinder, let him know what lobe goes where (exhaust and intake lobes).

Show him your lifters, and give him the space available (that you measured
with your childrend clay on the valve action), and tell him that you want a cam
that has the same duration, same overlap , same intake and exhaust timeing, but
you want the most lift that will permit the lobes to swep the lifters without
falling off, and that the valves are not touching the top of the heads, and you
want the latest, more modern 'fast open, fast closing ' profile.

Many camgrinders are Gurus, and I have seen some that have a little bit
personality like a master chef, the world rotates around their knowledge, and
they are the only ones that can make this work. Don't sell yourself, insist on
having the same timeing, overlap, duration, but higher lift, and a fast open
fast close profile. Say it twice if he starts to preach cam gospel for you.

When he is done, you don't want to see a pointed profile, but a profile that
looks about the same as you came in with , rounded, but higher. The camgrinder
will nitrite harden the lobes for you.

In that way, you have stayed with a cam profile that will give the exact same
power curve, but you have transferred it upwards.

I bet ya, out of those modes, you will have 25 -27 HP out of that thing, and
still have very moderate compression, and still to this day, it is for me very
puzzling why the QAC had high compression heads only, as the only way of
increasing the power.

You asked about reliability issues, well yes they had some issues, with those
heads, quite a few was sent back, and many just went back to the original heads.
Again, you have to stay very conservative when it comes to flat head
compression ratio.

Had the QAC had a bit more moderate compression, and developed a very good cam
instead, it would have been another engine, most probaly a problem free engine,
as you are making it breath better with a cam, you are still not feeding the
engine more than the throttle will open up anyway, but you have more on the
throttle when you need it.













ohlson38 < Nical@... > wrote:
Anyone out there know what QAC did to bump up the Onan from 18 to
22? I know the heads were milled...don't know HOW much...does anyone??
Were there subsequent reliability issues???

Thanks for considering the above,

Nick L.





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Thank you very much for your informative and logical post on the Onan
mod stuff. Cam grinding, I agree, has to be the real key to achieving
the Onan's 'sweet spot'. Good advice on the Guru Factor as well...what a
hoot!

Whether the Onan is worth the work is of course another story. But the
basic concept of the Q-1 is, I think, lost when comparatively large HP
(read weight) conversions are done.
Again, thank you for the post!

Nick L.


> I dont know what they did, but I do know that the heads they were peddling
> had a lot of problems, you can not really do too much compression on a
> flat head, and they did.
>
>

Look at www.somender-singh.com His engine modification is worth looking at if
you want better performance. It can improve the efficiency up to up to 33%. All
it takes is a hack saw blade,3 cornered file ,a sheet of emery paper and a new
head gasket.The job should take you an hour and only costs you the price you
paid for your tools which you probably already have. Read his web site and any
questions he will answer. He is a home builder in India with over 1500 flying
hours in home built he built.

ohlson38 < Nical@... > wrote: Anyone out there
know what QAC did to bump up the Onan from 18 to
22? I know the heads were milled...don't know HOW much...does anyone??
Were there subsequent reliability issues???

Thanks for considering the above,

Nick L.






[Non-text portions of this message have been removed]

Read the article, Hmm...got to give this a thinker....

Intake shapes and combustion shapes have been experimented with since the
first day of the combustion engine, and any company that are designing engines
are doing it, especially high performance engines like motorcycle engines. Teams
are working daily in those factories to get to the best shapes and forms of the
intended engines internals.

I have a hard time to think that during the last hundred years the combustion
engine have been around, someone have been overlooked a simple thing that will
increase the efficiency by 30% or more.

The calories burned in an engine, will only transfrom about 30% of the burned
energy to motion.

If you increase the efficiency by 33 % or more, that means that you will have
an engine with a 60% or better efficiency. Something absolutely completely
unheard of.

The really really big engines like ship engines , with a very big displacement
have a very good thermal efficiency, and the record right now is a touch over
50%, in one of those super big engines.

Were we're talking engines that have catwalk inspection platforms inside the
engine case.

This guy claims he can do all this with some sand paper, and some sharp
objects...hm...

I am sorry but I have to stay a sceptic on this, and prefer to be a Missourian
and say....-'show me'.

If you are inclined to experiment with this, do it on a junk engine.

Roger


RICHARD GLIMES < lansair@... > wrote:
Look at www.somender-singh.com His engine modification is worth
looking at if you want better performance. It can improve the efficiency up to
up to 33%. All it takes is a hack saw blade,3 cornered file ,a sheet of emery
paper and a new head gasket.The job should take you an hour and only costs you
the price you paid for your tools which you probably already have. Read his web
site and any questions he will answer. He is a home builder in India with over
1500 flying hours in home built he built.

ohlson38 < Nical@... > wrote: Anyone out there know what QAC did to bump up
the Onan from 18 to
22? I know the heads were milled...don't know HOW much...does anyone??
Were there subsequent reliability issues???

Thanks for considering the above,

Nick L.





[Non-text portions of this message have been removed]





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I agree, the Q1 in it's original form is the winner, but it is also true that
the original 20 HP Onan was kind of on the low end when it comes to HP, even
though it was not too bad, and have the best flying record so far.

Reason is that most people that are building an aircraft will make mistakes,
and those mistakes are seldom benefited from, as the builder very seldom will
build another aircraft of exactly the same type.

So from the tables that I have seen, it seems like most aircrafts coming out
of the garages, are sharing rest of Americas obesity problem. On occasion, but
it is more an occasional thing, the aircraft weigh in as specified by the kit
manufacturer.(some even less) Majority have added weight.

The cure is HP. The pilot weight, 170 or 180 pounds, ...dont remember off
hand, think it was 180 pounds, is also another issue for HP, many are tall and
heavy, and even if you put a 180 pound guy in it, clothes, shoes, belt, glasses,
jacket, earphones and what nots, he might very well end up be a bit over 200
pounds. Guys that naked scales over 200 pounds could use some extra HP.

The two options that are within the window of stayng as close to the original
as possible is the 48Cu inch Onan and the 60 Cu Inch Onan.

The 60 Cu inch Onan have 24 HP, (Hard to find engine) but a lot of torque, and
a Hot Rod fix is maybe doable if you stay very conservative, but the 48 Cu Inch
Onan (Easy to find engine)could use a pretty decent cam job.

If the Onan is worth doing the job, well... a cam grind is (depending on where
you go) about 50 bucks, and I would say that it is well worth doing it first,
and find out if you are happy with the Onan after that. Chances are that you
will be, if not, then, at that time make another decision.

And yes, hanging a Merlin or a Griffon engine up there would completely ruin
the whole concept. (and of you are trying to fly it, it will probably ruin the
whole day)

Roger

Leonard Nick < Nical@... > wrote:

Thank you very much for your informative and logical post on the Onan
mod stuff. Cam grinding, I agree, has to be the real key to achieving
the Onan's 'sweet spot'. Good advice on the Guru Factor as well...what a
hoot!

Whether the Onan is worth the work is of course another story. But the
basic concept of the Q-1 is, I think, lost when comparatively large HP
(read weight) conversions are done.
Again, thank you for the post!

Nick L.

> I dont know what they did, but I do know that the heads they were peddling
> had a lot of problems, you can not really do too much compression on a
> flat head, and they did.
>
>





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