REFLECTOR: To Turbo or Not

Scott Derrick scott at tnstaafl.net
Sat May 9 07:44:14 CDT 2009


Chuck,

I agree that the industry will have to provide some kind of alternative
though it does look like its going to be a compromise solution and some
engines may require expensive modifications to run on the new fuel.  
The turbo charged engines being in that group.

The 1000LL fuel situation was really just the last straw in a series of
issues that brought the decision to a head.

The primary issue of the turbo'd engine weighing more than I thought. 
Quite a lot more.
Followed by the almost impossible task of fitting it into a reasonably
shaped cowling.

I have come to the conclusion I really don't need that much engine. The
io360 was definitely underpowered at a 6500 ft elevation airport.  I
think an IO520 will be plenty.  If not I have a turbo solution sitting
on the shelf that is 80% complete.

I will fly first sans turbo and see how that goes.  If its plenty, I
will be glad to not have all the stuff associated with a turbo system
hanging on the airframe requiring increased vigilance and maintenance.

Scott

Chuck Harbert wrote:
> Scott, I'm late in responding, but it wouldn't seem to make sense to
> take off the turbo on the possibility that there won't be 100LL or an
> alternative additive. I think there are just too many airplanes
> dependent on 100LL to eliminate it without an alternative available.
> When they got rid of 100 octane auto fuel, custom cars with high
> compression engines ended up adding octane boosters to prevent
> detonation, or they buy racing fuel (100-108 octane) which cost about
> the same as avgas. You're right that you can keep the boost down under
> 30" (turbonormalizing) if they go to lower octane fuel.
>
> The whole advantage of a turbo is that you carry sea level power to
> higher altitudes which allows you to significantly increase (200 kt
> cruise) your ground speed in the thin air. You've spent a lot of money
> to get this engine, so before you dismantle it on a unlikely
> possibility, I'd go forward with your original plan.
>
> That's just my opinion.
>
> Chuck H
>
>
> ------------------------------------------------------------------------------------------------------------
>
> 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
>
> --------------------------------------------------
> From: "Scott Derrick" <scott at tnstaafl.net>
> Sent: Friday, April 17, 2009 6:20 PM
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Subject: REFLECTOR: To Turbo or Not
>
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