REFLECTOR: Turbo concerns

Tue Aug 21 13:56:17 CDT 2012

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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>>
>> -- 
>> Man must evolve for all human conflict a method which rejects revenge, 
>> aggression and retaliation. The foundation of such a method is love.
>> Martin Luther King Jr.
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