flak monkey
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| posted on 21/5/10 at 08:36 PM |
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Its 0.5% at 50deg then 1.1% at 60deg I think.
Running in closed loop is possible but it doesnt really help it still goes lean and rich every minute or so. The trouble is when it goes lean the
mixture jumps around so quickly the lamda cant keep up. When its running slighty rich it runs smoothly and the lamda correction works properly.
Sera
http://www.motosera.com
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sebastiaan
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| posted on 21/5/10 at 08:53 PM |
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If it does run in closed loop it should not go rich, unless the end of the control authority range is reached. Any idea what the range is in which the
closed loop can control the mixture? I'd whack it up and see what happens.
If it goes lean the AFR will indeed jump about quite a bit due to (partial) misfiring and improper combustion phasing.
Is is possible to post or send a datalog I could have a look at?
It's bound to be something simple, don't worry.
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flak monkey
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| posted on 21/5/10 at 09:05 PM |
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Yes it starts missing when it goes lean. Seems happiest running at around 12.5 at idle.
What I have done at the moment is richened the idle so that when rich its 11 and lean is about 13.5. At least like this it keeps running ok.
The lamda has loads of authority - 75% infact - and it only ever uses around 10% if it is enabled. Its set to come on under 1500rpm and 80kpa....
It still tries to go lean with EGO enabled. The regularity of it means I am sure theres something the ECU is doing every 60secs or so that causes it,
but I cant find anything anywhere.
I can post a datalog but I dont think it will tell you anything as I am running Omex now....
[Edited on 21/5/10 by flak monkey]
Sera
http://www.motosera.com
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sebastiaan
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| posted on 21/5/10 at 09:16 PM |
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So, does the engine "outrun" the ego correction (i.e. does it go lean quicker than it can correct for it) or does the ego correction clip
somehow? It should not go lean with EGO correction enabled.
If you can / want to post a full datalog (with all parameters enabled if possible) I'm sure I can make at least some sense of it. What type of
Omex are you running? 600?
If you can only select a few parameters, could you at least select:
RPM,
MAP (if you have this)
Ignition angle
MAT
EGO correction %
Vbattery
Injection pulse (total length)
Injector bias
Lambda
And I'll see if I can have a look later this weekend. If possible, could you also send / post the calibration?
Sebastiaan
ps. I've been a full-time engine calibration engineer for some 3 years in the past ;-)
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atspeed racing
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| posted on 24/5/10 at 09:13 AM |
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what does the fuel pressure do when this happens?
- colin.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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flak monkey
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| posted on 24/5/10 at 09:59 AM |
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EGO correction certainly doesnt seem to help very much. I would say there is a minor improvement, but when its running lean/rough the fluctuations are
so quick I dont think EGO can keep up.
Fuel pressure doesnt look to change at all - other than the normal minor fluctuations as the injectors open which dont noticeably change.
I think it does this when you are holding a constant road speed as well, although its very difficult to tell when driving along as you are always
varying the throttle. Obviously it's most easily noticed at idle, so if I can solve the problem there then thats a start... 
I have mailed Andy at Omex, I know he is back from holiday today, but no doubt is buried in emails....
David
Sera
http://www.motosera.com
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atspeed racing
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| posted on 24/5/10 at 12:20 PM |
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its certainly odd. let me know if andy finds anything within the map or omex.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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sebastiaan
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| posted on 24/5/10 at 12:40 PM |
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EGO should be quick eonough to not let it GET lean and run into misfiring trouble. Can you increase the EGO step speed somehow and see what happens?
I'd combine this with a rich idle (AFR~13) to create a bit of a buffer.
Basically, try playing around with the EGO settings to see if you can avoid the engine going lean. that SHOULD be possible. If you are running large
injectors, it is also paramount that the injector bias / dead time is calibrated correctly since the EGO can only work correctly when those are OK
(i.e. if the EGO correction "thinks" it is adding 10% of fuel, it should also really add 10% of fuel. If the bias correction is out, so
will all other corrections....)
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flak monkey
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| posted on 24/5/10 at 12:45 PM |
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Yes, I havent fiddled with the injector opening times at all yet. I thought I would leave it well alone as it would affect the fuelling throughout the
rev range wouldnt it?
I know the figures that are currently in the ECU are too long compared with what they should be. But the shape of the curve is the same, just slightly
offset.
I also havent played around much with the EGO settings. Theres a screenshot below of all the settings that are available. Those shown arent my
settings though, its just a shot frmo the Omex manual.
BTW the datalogs from Omex dont seem to have everything you would need in them. It logs a lot less channels than MS unless there is some way of adding
channels to a log?
 
Rescued attachment ego.JPG
Sera
http://www.motosera.com
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sebastiaan
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| posted on 24/5/10 at 02:41 PM |
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Decrease OX FB rate and increase OX FB gain with a factor of 2 each. That should make the EGO 4 times more agressive. This might cause a mildly
unstable idle, but at the mo, we're just looking for proof of concept (i.e. using the EGO to keep the idle AFR constant-ish)
[Edited on 24/5/10 by sebastiaan]
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flak monkey
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| posted on 24/5/10 at 03:15 PM |
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OK, I have figured out how to do the logging with Omex (i think) - it only logs the parameters you have displayed at the time. So I have made a
display screen showing the appropriate parameters and will do some logging tonight.
I will log from a cold start and record the times when the problems are seen.
I'll then have a play with EGO and see if that helps.
Thanks,
David
Sera
http://www.motosera.com
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MikeRJ
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| posted on 24/5/10 at 06:27 PM |
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I have to share your reluctance to enabling EGO to fix this, it just shouldn't happen in the first place so it feels like a crutch rather than a
fix for the underlying problem. Hopefully the logs will give a clue as to the problem.
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atspeed racing
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| posted on 24/5/10 at 06:48 PM |
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you shouldnt have to be enabling any additional corrections. that is not the problem. it shouldnt need any corrections at all. that will only add more
complications to the problem.
raise the idle speed to 2000rpm, see if the problem continues.
i think we should be looking at a problem within the car, not the ecu... back to basics... air leaks, manifold vacuum when running, fuel delivery,
fuel supply.
- colin.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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flak monkey
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| posted on 24/5/10 at 07:09 PM |
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Well, I think I have fixed the problem....i say think because only time will tell.
Started the process of elimination thing...
Whilst doing my datalog I sat there watching the differences between lean and rich and the only thing I could see (other than the obvious) was the
average TPS had increased by around 0.3%.
Colin, you will probably remember you saw some noise on the TPS and sensor outputs before you started working on the car with just the ignition turned
on and nothing running... So this got me thinking.
I disconnected the live and earth to the ECU and connected direct to the battery, no difference at all - same noise.
Then started to think what else was connected with the ignition on.
Flourescent backlight in the dash - no effect
Low pressure fuel pump - no effect.
At this point scratching my head to determine what else is always powered up when the ignition is on...
Only other thing was Lamda sensor (LC1). So I pulled the analog ground which goes to the ECU off and it seemed to stop the noise and also made the
water and oil temps read correctly on the dash.... Hmmm onto something there then I reckoned...
The analog ground is also connected to the ground of the dash - so I wonder if there was some sort of ground feedback loop going on?
Anyway with the analog ground disconnected it seems to maintain whatever mixture you set (actually on the leaner side rather than the richer) and the
dash temps now read correctly too.
I had the car ticking over for a good 15mins with no noticeable changes in the mixture (other than the normal fluctuations I would associate with the
huge injectors).
There is some noise on the TPS signal with the engine running, I would expect this is normal due to small voltage fluctuations etc? Not talking much,
maybe 0.3%?
So I will monitor the situation now and see how it goes from here on in.
I just have my fingers crossed that it still drives OK now the problems been fixed....
I do wonder why the 60 and 70sec swings though. Maybe this is the timing of the heater in the lamda probe or something?
Thanks for your patience!
Sera
http://www.motosera.com
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atspeed racing
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| posted on 25/5/10 at 08:32 AM |
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fingers crossed on that one.
99 times out of 100 its the car, not the ecu.
poor earths cause endless problems when we are working down in 0-5v, or 0 - 0.5v scales, a poor earth or slight change in voltage can cause all sorts
of dramas.
keep us informed
- colin.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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MikeR
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| posted on 25/5/10 at 11:35 AM |
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ironically i was reading this and wondering if there was a problem with your TPS - i didn't think it would be voltage but a dodgy switch sending
strange signals once in a while.
Guess i was almost (in a very oblique way) on the right track.
Good luck & do you think this could have been affecting your megasquirt?
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flak monkey
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| posted on 25/5/10 at 11:44 AM |
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There was a different issue with the megasquirt, which Phil at ExtraEfi has recreated on the bench so I am confident the issues I was having with that
are unrelated.
Sera
http://www.motosera.com
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