| Hi Finn
I have similar setup to you. Renesis 4 port.
I moved to all 4 Blue (secondary size) injectors as the red primaries 290cc were saturating (ON all the time) by just before staging at 20 inches of manifold. So the engine was going lean just before staging, making tuning the mixture table difficult.
I’m not sure you should trust your pressure readings without first checking them against a reliable source.
I went with the 4 Blue 540cc injectors only as I had spares, however would prefer the 6 port yellows 425cc as they would be a better size and I read that they apparently have a better spray pattern.
Also, I had wondered about the pulsation damper. I don’t have one and all seems OK with no problem with reading pressure on the Dynon from a basic VDO pressure sender.
I must get around to reprogramming the EC3 and switch out the EC2 and calibrate the EM3 fuel flow. I’m getting my fuel flow info from the Dynon and Fuel Flow transducer. I dead ended my fuel rail after the regulator so as to be able to use the one fuel flow transducer.
Cheers
Steve Izett
Ah...I thought you were saying that the
pressure *increased*. If it's fluctuating randomly, and you're
sampling once/sec with no damper, it could be all over the map
(pardon the pun).
Same symptom with digital MAP gauges; I was seeing swings of
several inches in MAP on my Lyc's engine monitor until I put a
restrictor in the feed to the MAP sensor (creates a damper).
Unfortunately, I don't thing that would work with a fuel line. ;-)
Charlie
On 5/4/2021 2:49 PM, Finn Lassen finn.lassen@verizon.net wrote:
Does the pressure increase have a
solid 'step' at the exact staging point, or is it just rising
in that area?
Yes, solid steps.
One second sampling intervals.
How much increase on the gauge?
Where is the reference for fuel pressure measurement?
18 to 64 psi, about 36 average.
At end of secondary fuel rail.
The pressure *regulator* should be referenced to MAP (manifold
pressure), and will raise absolute fuel pressure as manifold
pressure rises. If the gauge is referenced to atmosphere (or
absolute), it would indicate a rise in pressure as the
throttle is opened.
The regulator does respond to MAP changes. Originally I thought it
was too sensitive and the source of the wild swings in fuel
pressure. But there is a high-pressure fuel filter between the
regulator and the fuel rails. Figured that would dampen any pulses
before they reach the regulator but probably not true.
Actually I don't have a dampener in the MAP line to the regulator.
Should probably try that. Since it wasn't an issue when tuning the
engine I forgot about it. The EC3 probably averages MAP samples.
The more I think about it, if there are pressure pulses caused by
injectors opening and closing, the one-second sampling of the fuel
pressure sender could be randomly be hitting highs and lows. I
really should hook up an O'scope to the pressure sensor to see
what the signal from it looks like.
Finn
Finn
No rx-8 injector experience, but if at the staging
point, if the EC-2-3 shuts off the primary injectors, and
the secondaries haven't opened, fuel out of the manifold
decreases, so the pumps would raise the pressure. Are you
confident that the controller is reducing the primaries
and starting the secondaries at the same time?
Bill
Is
the fuel pressure really increasing or is it the
EM2/3 reading? Steve B. has posted good advice
for tuning around the staging point with different
size injectors.
Bobby
From:
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Tuesday, May 04, 2021 11:46 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Renesis secondary
injectors
I noticed that my indicated fuel consumption
appeared to be about 50% higher than actual. So I decided to start calibrating engine monitor
fuel flow. The first step is to check/adjust fuel flow around
the staging point (20"Hg) where the secondary
injectors open (secondary injectors are larger than
primary injectors on the 4-port Renesis). I thought I had previously tuned the engine for a
smooth transition around the staging point, at least
to the point when I didn't notice anything when
dvancing throttle through the staging point. However, now doing stationary run ups around the
staging point (especially when engine is getting
hot) I get the weird phenomenon of it going very
lean when secondary injectors (supposedly) open.
Another odd thing is that fuel pressure increases
markedly. On the HomebuiltAirplanes.com forum a guy that
raced RV-8s for a couple of seasons mentioned
troubles with the stock Renesis injectors. Now I'm wondering if I have (intermittently) bad
secondary injectors -- not opening when they should. However, I'm confused by the rise in fuel pressure.
Is there a injector failure mode where pressure in
intake runners could push back through the injector
into the fuel line? Note that these are factory-new, maybe 10 to 20
hours of total engine run (or attempted run) time. Another possibility is heated secondary fuel rail.
But if there were boiling fuel there the fuel
pressure should still drop when secondary injectors
open... I tried to look but didn't find a chart of 87
octane 10% ethanol boiling point vs temperature. Anybody here had any trouble with stock Renesis
injectors? Symptoms? Other ideas? Finn RX-8 4-port:
Primary: Denso 195500-4430 33.3 lb/hr @ 43.5 psi
(350cc/min) 13.8 ohm
Secondary: Denso 195500-4460 51.4 lb/hr @ 43.5
psi (540cc/min) 13.8 ohm
Disclaimer The
information contained in this communication from the
sender is confidential. It is intended solely for use
by the recipient and others authorized to receive it.
If you are not the recipient, you are hereby notified
that any disclosure, copying, distribution or taking
action in relation of the contents of this information
is strictly prohibited and may be unlawful.
This email has been scanned for viruses and malware,
and may have been automatically archived by Mimecast
Ltd, an innovator in Software as a Service
(SaaS) for business. Providing a safer and more
useful place for your human generated data.
Specializing in; Security, archiving and compliance.
To find out more Click Here.
|