Hi Guys We got some further fault finding done today towards
isolating the cause of the massive missing problem with our Renesis 4
port. The troubling symptom / major problem is as we approach
23-24â MAP at various prop pitch and rpmâs (both A and B
computers), with very little warning begins to miss and then pretty
much go immediately into massive missing and popping in the exhaust.
Just before the bad stuff begins the EGTâs read 1540 and 1440. I
have only done mode #3 programming and adjust the mixture with the
manual mixture control while watching the narrowband. It stages at
19âHg as per Tracyâs recommendation for Red and Blue Injectors.
So order of events today:
I wondered previously what the seals where like so having received a
new $22 pressure transducer I took out trailing plugs and grabbed
some pressure data while cranking. See plots in WORD file attached -
Rotor #2 has one pulse down by max of 6 psi compared to the highest
pulse. Does this mean that side seal is leaking?
We then went after 3 key possible problems: 1st being Engine monitors
holding Injector #1 open so:- A. Disconnected Dynon engine monitor to
isolate it as a cause of disturbing Injector #1. No change. B.
Disconnected EM3 to isolate the same as above. No Change.
2nd being Pulses in the intake manifold messing with EC2 fueling. We
inserted a 0.6mm restriction in MAP sense line. (This line then
âtâsâ of too A and B Computer MAPâs. No Change.
3rd Renesis CAS generating to higher input voltage. Tracy recommends
1K across CASâs. I think this mod may have been done. See photo of
EC2 PCB below pin 4 & 23 both tied back to pin 22 via something
inside the heat shrink.
So Iâm stumped for the moment. At least we know more of what the
problem isnât, Which is helpful.
Also the EM3 does at times fail to read RPM etc and display reads
NOP.
Appreciated any input.
Cheers
Steve Izett
Good work on the pressure recorder Steve. I guess you used a
Micromite.
What brand of pressure sensor did you use?
Could be a side seal leaking as only one chamber seems to be
affected.
Try changing your spark plug gaps to .020".
Check the gap on the inductive sensor on the e-shaft. The closer the
better. Make sure the bracket is stiff. You don't want it resonating
at some RPM.
Are you still using the Chevy coils?
What most people do in road racing is put a container in the MAF
plumbing to average out the MAF. One has no idea exactly when this is
sampled by Tracy's computer. It tends to vary cyclically with RPM.
Putting it another way it damps the manifold pressure variations.
Here is a picture of it on a road race car.
Paul Lamar
Hi Paul
The pressure sender was a cheapy of eBay but claimed a 1mSec rise
time, and I know the sample rate was something greater than that.
Appears to read OK.
We have two separate CAS sensors and switching from A to B has the
tiniest miss at high rpm but otherwise no difference. The renesis
has a non adjustable gap. (you could enlarge it with awash I
suppose)
The coils are the heavy duty Chev variety but probably a cheap
version. Tracy recommends and has been running these coils I believe
with good results. Wonder how I might check the coil output?
Plugs are the flat (sorry don’t know the technical name) type and
where clean. I’ll swap them out fir some others.
Cheers Steve
Tracy was not running those coils at high RPM. Never the less they
where overheating to the point of failures. Tracy went to the trouble
enclosing them in a box with a blast tube. What is your gear box
ratio. I think Tracy never ran higher than 2.85:1.
Again those coils are for a piston engine that fires them half as
often. If used for an engine that fires once per rev the maximum RPM
for those coils is 4000. Tracy was not infallible. Just stubborn at
times :-)
Here are some old messages on the subject.
----------------------------------------------------------------------
I think I noticed one of the D581 type have weak spark shortly before
complete failure. I am still using three of the D581's just to proove
to myself that it was a heat problem that caused several failures before
I put a cooling plenum around them.
I have heard no reports of the D580 type failing (even without a
cooling plenum) but I still recommend an enclosure with a supply of
cool air to them. We are pushing them pretty hard in aircraft use.
Tracy
Hi Al,
I have not seen degraded spark from a LS1 coil, since I have only
used the LS1 coils on my 20B. I can say that I have seen degraded
performance (output voltage/current) on a single coil ignition system
on a GM engine. I would imaging that in addition to failure of solid
state components the primary or secondary winding could have a defect
(intermittent open, short or high resistance) that would affect the
output voltage.
Joe
On 10/21/07, Al Gietzen wrote:
Has anyone noticed a "degradation" of spark strength as a failure
mode of the LS1 coils? I've assumed that a coil failure would most
likely occur due to failure of a solid state component in the coils
circuitry; resulting in no spark.
Al
------------------------------------------------------------------------------------------
Please get a late set of RX8 coils or switch to a capacitor system.
The best plugs are iridium. The RX8 uses iridium. Try a smaller gap.
Paul Lamar
Thanks Paul
I had trouble with one of my plugs so I’ll try some new ones and see
if this is the source of the problems.
Steve Izett
The reason for checking the small gap is::: air is an electrical insulator.
When the manifold pressure goes up it is harder to fire the plugs.
The voltage required to do this MUST increase. The voltage you
get out of a coil is proportional to the dwell. Unfortunately so is
the heat of the coil. If the dwell is too short the plug will fail
to fire.
Back in the old days when we had mechanical points
if you left the ignition on with out the engine running and the points
happened to be closed the oil filled coil would get so hot it would
burn your fingers.
These coils have been around since 1922. The only difference is the
points are replaced by a transistor and oil is no longer used. There is
one transistor in each coil.
I jest read a book called P47 Thunderbolt Combat Missions.
ISBN 978-1-4351-5895-5
The first chapter describes the development. The P47 was one
of the first fighter planes that used a turbo. It was designed to fly
up to 40,000 feet. The engineers had trouble with the ignition.
The spark would jump everywhere except the spark plug gap
because the boost pressure was so high. The magnetos had
problems with the altitude as well. They wound up using pressure
out of the turbo to pressurize the magneto to insulate it.
BTW the last versions (P47M) to see combat where the fastest
WW II American fighter planes at 480 MPH. They shot down several
ME 262 German jets although not quite as fast.
Here is the output of my new coil design. Patent still Pending.
This is 5 sparks 5 degrees apart at 8000 RPM.
Paul Lamar
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