REFLECTOR: To Turbo or Not

Sat Apr 18 09:10:44 CDT 2009

Kurt,

    I am close, but I'm also at a point where it is relatively easy to
go either way, but changing after this point will get progressively
harder and harder. 
    I think a dual system may happen at first, where 100LL is available
along side a lower octane alternative, but 100LL will get very expensive
very fast. We are such a minuscule portion of he fuel industry,  it
wouldn't take much to push the few refineries that mix av gas to change
over to a no lead product.  I think this is right around the corner.
    I am getting more and more concerned with weight.  Maybe I should
slap the wings back on and do a quick weigh to let me know where I
stand. Much easier to make a decision on facts than fears.
    I'm also concerned about the longevity of this tsio520.   I've been
flying behind two of these engines for about 3 years now.  They are
solid and reliable, but,  pushing them with high MAPs  seems to find any
flaw and exacerbate it rapidly.  I've seen some cylinders go 1800-2000
hours and still be performing well, and I've seen others not make 200
hours...

    I do hear your voice concerning the pitfall of changing course in
midstream.....
   
Scott

nmflyer1 at aol.com wrote:
> Scott,
>
> If it was me, I wouldn't be too hasty about changing my plans at this
> point. You are awfull close right now, and there is no way that they
> are going to get rid of 100LL very soon without some way to address
> higher compression engines.
>
> If they go with the 94UL that they have been working with, you are
> still pretty close to a reasonable octane for your setup. They might
> keep 100LL around as they try and address higher performance engines,
> or they might come up with an additive that gets the octane to the
> point where turbo'd engines can be happy.
>
> Regardless, I think that you have time to finish and enjoy your
> project, then try and hedge against the future. Blending your own fuel
> (Like I do), ising additives, or knowing they won't render a large
> chunk of the GA fleet worthless gives you piece of mind & time.
>
> Of course, if you are just looking to change weight, heat, complexity,
> fuel concerns, etc.. that is a different matter.
>
> I would press on. Then start covering your bases with research. You
> might purchase a stand alone Knock sensor like I did just for
> insurance & piece of mind.
>
> Kurt.
>
>
> -----Original Message-----
> From: Scott Derrick <scott at tnstaafl.net>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Sent: Fri, 17 Apr 2009 7:20 pm
> Subject: REFLECTOR: To Turbo or Not
>
> After reading another article about  100LL  going away  sooner than we
> think I started thinking about the  tsio520 I'm installing...  Wise for
> the long term? 
>
> One solution to running TCM's new 97 no-lead(or some other low octane
> alternative) would be to limit the boost to 30 inches, which would allow
> running a lower octane fuel.  A reasonable solution except for that fact
> that then I would be carrying all that weight of the turbo system, not
> to mention the extra maintenance costs and not getting all the
> benefits.  Most of the lost benefit would be take off, initial climb and
> emergency power since cruise MAP's would be in the 25-30 range.
>
> So I decided to add up the benefits of no turbo, assuming my 520 could 
> be made to run sans turbo with  minimal cost.
>
> 1.)  I think the turbo system with, large heavy turbo, support brackets,
> wastegate, wastegate controller, extra exhaust pipe, 4 long oil lines,
> intercooler, extra induction tubing, oil reservoir, upper deck pressure
> lines, large external scoop for intercooler & turbo,  all weigh up to 80
> lbs.  Maybe more. Thats a lot of weight. 
>
> 2.) Less maintenance just because there is less there of high
> maintenance items plus not running the engine at such high MAPs.
>
> 3.) The compression ratio on this engine is 7.5 to 1 which would allow
> the use of auto gas.
>
> 4.)  No large scoop and large bulge that would have increased drag quite
> a bit.
>
>
> Possible down sides..
>
> 1.)  I have put quite a bit of $$ into getting the turbo system to
> work,  I could recoup some of this by selling the parts.
>
> 2.)  I'm not sure how much horse power I could expect.  Typically about
> 285 at sea level, but with the 7.5 to 1 pistons instead of 8.5 to 1 that
> would be reduced.  Anybody know by how much?
>
> 3.) Getting the current injection system to work  without  the turbo 
> charger.  I'm not sure  if thats possible , which means  the added cost
> and  work of getting  a  standard TCM injection system for a  io520. 
> Its possible I would need just a different  controller.
>
> 4.) Loosing the benefit of high altitude turbo charging which can be a
> huge speed  increase.
>
> 5.) Odd ball engine install.. 
>
> I'd appreciate any comments one way or the other...
>
> Scott
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