REFLECTOR: low end idle speed

Douglas Holub douglas.holub at gmail.com
Thu Jan 15 12:19:15 CST 2009


Mystery solved. The sniffle valve in the cold air induction plenum did not 
get installed when the engine was assembled, and so the engine has been 
getting too much air. I could have saved a couple of days of trying to 
adjust the fuel injection system to compensate if I had only known, but at 
least I understand the fuel injection system very well now!

Thanks for all the input anyway...

Doug

----- Original Message ----- 
From: "Brian Michalk" <michalk at awpi.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Thursday, January 15, 2009 11:37 AM
Subject: Re: REFLECTOR: low end idle speed


> Maybe I don't understand what you mean by "won't idle".
> Pulling out on the throttle won't go below 950 RPM's?  Is that what you
> mean by mechanically?  I assume your idle stop on the throttle body is
> as far out as it will go.  There may be idle ports there you could play
> with.
>
> I understood you meant that the engine would die below 950 RPMs, and
> that's what my post was about.
>
> Douglas Holub wrote:
>> I set the unmetered fuel injection pressure at 11 psi at 950 RPMs per the
>> manual and conversations with the ECI test cell technician. There is no
>> rough idle. Pull the throttle out, smooth 950 RPMs. Slam the throttle in,
>> solid 100% power without a hiccup. Pretty cool.
>>
>> No magnetos, either. The Plasma III manual says that one can expect the 
>> idle
>> speed to increase up to 150 RPMs with electronic ignition, but I just
>> figured there would be a way to knock it back down to 800.
>>
>> Doug
>> ----- Original Message ----- 
>> From: "Brian Michalk" <michalk at awpi.com>
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Sent: Thursday, January 15, 2009 9:29 AM
>> Subject: Re: REFLECTOR: low end idle speed
>>
>>
>>
>>> Your magneto timing may be too aggressive for a hot cam at low RPM.
>>> It could also be a fueling issue.  What's the ECI fuel injection
>>> pressure at this RPM?  I would think related to poor atomization.  Do
>>> your EGT's go up appreciably from smooth idle to rough idle?  If this is
>>> it, I would think you would see a 30 to 50F change.
>>>
>>> No real adjustments for either of these problems.  But you can fiddle
>>> around with timing and fueling to diagnose which one is the problem.
>>> It's just that you wouldn't want to fly that way, especially retarded
>>> magneto timing would result in lower power in your power band.
>>>
>>> Douglas Holub wrote:
>>>
>>>> My ECI IOX-360 with dual Plasma IIIs won't idle less than 950 RPMs,
>>>> and I was expecting to get it down to 800. It runs smooth and strong
>>>> at all speeds. With full throttle I get 2320 static RPMs at 28.7 MAP
>>>> with the fixed pitch Prince 68/78 prop. I've calibrated the ECI fuel
>>>> injection using ECI's calibration kit. There's just no where to go
>>>> mechanically less than 950 RPMs.
>>>>
>>>> I remember from transition training that if I didn't pull the power
>>>> all the way back while landing, the Velocity would float forever down
>>>> the runway, but I don't remember what the low end idle speed was on
>>>> the factory trainer, and anyway, it had a constant speed prop. Am I
>>>> going to have any trouble landing at 950 RPMs?
>>>>
>>>> Doug Holub
>>>> ------------------------------------------------------------------------
>>>>
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>>
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>
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>
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