REFLECTOR: Turbo concerns

Tue Aug 21 15:55:36 CDT 2012

The mixture would be screwed up as the servo is expecting a certain 
amount of air with the turbo but is not getting it.  I imagine its 
running really rich with or without the turbo.  You could verify that by 
checking a plug.

Scott

-------- Original Message --------
Subject: Re: REFLECTOR: Turbo concerns
From: Laurence Coen <lwcoen at hotmail.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Date: 08/21/2012 12:56 PM

> Chris,
>
> I think you do have a turbo problem but I think there is more too it
> than that.  The numbers that you supplied suggest that the computer
> controlling the spark advance and gas air ratio is getting different
> information with the turbo connected and disconnected.  If you look at
> the 2000 RPM data the engine gets the same RPM with two very different
> manifold pressures.  In both cases the engine load is the same (the
> prop).  The only way you could get the same RPM with an increase of 1.8"
> manifold pressure is to retard the ignition or screw up the mixture.
>
> Larry Coen
> N136LC
>
>
> --------------------------------------------------
> From: "Chris Barber" <cbarber at texasattorney.net>
> Sent: Tuesday, August 21, 2012 9:32 AM
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Subject: Re: REFLECTOR: Turbo concerns
>
>> Scott,
>>
>> Thanks, that gives me some specifics.
>>
>> Chris
>>
>> Sent from my iPhone 4
>>
>> On Aug 21, 2012, at 8:56 AM, "Scott Derrick" <scott at tnstaafl.net> wrote:
>>
>>> You definitely have something not working in your turbo setup. I'm
>>> assuming you measuring upper deck pressure?  Ala intake pressure
>>> after the intercooler and servo?
>>>
>>> problems.
>>>
>>> 1.) turbo is not spinning freely due to internal obstruction(I've
>>> seen rags), bad or incorrectly installed bearings, bent fan, etc.  It
>>> should spin very freely by hand, take a long time to come to a stop.
>>> Blow a vacuum cleaner through the turbo and see how she spins, with
>>> an open turbo(no back pressure) it should spin up very fast with a
>>> large canister style vacuum.
>>>
>>> 2.) waste-gate opening prematurely. In your case immediately. Can you
>>> see the waste-gate operation when the engine is running? Make bright
>>> marks on the moving parts to make this easier.  Note its position
>>> before start, then at idle, then a varying degrees of throttle
>>> position. It should be completely closed until close to mid throttle.
>>> At least the tio520 operated in that manner.
>>>
>>> 3.) pop-off opening too soon.  Tie a rag or something to the opening
>>> that will flutter around when it opens. Do this at the same time your
>>> observing the wastegate.
>>>
>>> 4.) If all the above are OK, its possible your intercooler is
>>> restricting flow. remove the intercooler and run without it.
>>>
>>> Scott
>>>
>>>
>>> -------- Original Message --------
>>> Subject: REFLECTOR: Turbo concerns
>>> From: Chris Barber <cbarber at texasattorney.net>
>>> To: REFLECTOR <reflector at tvbf.org>
>>> Date: 08/20/2012 07:18 PM
>>>
>>>>
>>>> As I have mentioned I have had what I think are incongruent readings
>>>> regarding my manifold pressure (mp)and engine rpm. It seems I am
>>>> getting quite low mp as I add power to higher rpm.
>>>>
>>>> I am not well versed in this area but my thought is that as I add
>>>> power, even with slight boost (currently using a 3 lb spring in my
>>>> wastegate) eventually my mp should raise a bit more.
>>>>
>>>> Today I did some static test. I recorded engine RPM with the  turbo
>>>> hooked up and recorded the mp at 1000 rpm increments. Then I removed
>>>> the turbo plumbing from my intake and recorded the same info My
>>>> results currently confuse me.
>>>>
>>>> With the turbo hooked up I am getting
>>>>
>>>> RPM.   MP inches
>>>> 2000 - 14.0
>>>> 3000 - 15.5
>>>> 4000 - 19.3
>>>> 5000 - 21.6
>>>> 5700 - 24.5 (topped out)
>>>>
>>>> With the turbo removed.
>>>>
>>>> 2000 - 15.8
>>>> 3000 - 15.3
>>>> 4000 - 19.7
>>>> 5000 - 24.8
>>>> 5833 - 29.8
>>>>
>>>> Is this indicative of restriction in my plumbing? Perhaps in the
>>>> inter cooler? A dirty air filter? A bad pop off valve or a leak not
>>>> allowing the air pressure getting to the intake. Or????
>>>>
>>>> I am uncertain what other permitters I need to check and provide. I
>>>> am just starting my diagnosis in my Phase One testing. I only have
>>>> 1.6 hours in the air so far. I value ya'll's direction and input.
>>>>
>>>> Heck, perhaps this is working properly but it just doesn't seem
>>>> right/comfortable.
>>>>
>>>> Thanks folks.
>>>>
>>>> Chris Barber
>>>> Houston
>>>> Velocity SE
>>>> Rotary 13b turbo (?) :-)
>>>>
>>>> Sent from my iPhone 4
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>>>
>>> --
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>>> revenge, aggression and retaliation. The foundation of such a method
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>>> Martin Luther King Jr.
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