Not really a problem, but something i have been working on for many months now,
When starting from cold the engine fires ok BUT then the revs drop to near stalling then pick up again,
does not matter what temp the engine is when first started it does this, it is ok when been running, if you switch off after starting from cold and start straight away its also fine,
any ideas?????
What sort of pulsewidths do you see on the main screen?
You're probably looking to make a change in the Priming/Cranking/Afterstart settings, once the engine is in afterstart you are either going too rich or too lean. The Pulsewidth gauge and/or datalogs will tell you by how much.
Rob
i will do a datalog and check the PW gauge in the morning when i do another cold start mate,
ta very much.
Based on the fact that you've said a re-start is fine, then it will be lean in the afterstart. The reason it re-starts better is that the additional fuel from the first start is left hung-up in the ports, which then gets added to to the normal afterstart fuel which is applied during the re-start.
For what its worth, the way I think about fuelling is this. Crank fuelling sets up the initial wall film, and supplies enough fuel for the first round of combustion. Afterstart fuelling then maintains this wall film, and adds fuel for poor vapourisation, which quickly reduces as the combustion chamber warms up. However, at this point the ports are still cold as the coolant temp has not increased. The warmup fuelling deals with this aspect, and supplies the additional fuel required to maintain the long term wall film requirement.
If you plot a curve of the combined effect of the terms against time (or combustions) you get a dogleg shape, where the afterstart fuelling decreases very rapidly (since the chamber comes up to temp quickly) then a dogleg and the warmup fuelling decreases more slowly
Try experimenting with more afterstart fuel but over less combustions. Also preferably log the lambda during start with a wideband gauge, along with the pulse width, engine speed and MAP to see exactly where the problem lies.
Good luck.
Please find below the data file for my cold start along with recent .msq file, i changed the after start enrichment to 60 and it didnt die down to a near stall, not sure if that is a fluke or not, but take a look at the two files and see what you think please.
http://www.capriracing.co.uk/vems/vemsdata.zip
Using the Datalog viewer we get a good idea of what's going on, I've drawn the ASE start and stops points.
It looks as if the 13ms pulse of fuel spins the engine up nicely, then fades out as we'd expect it to.
You may get less of a peak in RPM if you lessen the fuel pulse, but then its working so you may not want to spend too much time messing around chasing perfection for an event that happens at best 7 times a week! ;)
(http://www.vems.co.uk/VEMSInstalls/TonyCooper/TonyC_ASEnrich.png)
be gentle im still learning mate ;)
does every thing look ok now that i have changed the ASE % to 60? was at 40.
or is there room for more improvement,
From my point of view thats looking pretty good, it pulls the engine up to its idling speed and everything is fine and dandy. I'd wait for Cliff's verdict as he knows far more about the fuelling requirements and what its supposed to look like :D
Rob
Hmmm, OK here we go then.
The run up is OK, but not perfect. There is a 'stumble' (i.e. the engine speed drops momentarily) which could be caused wither by too lean or too rich fuelling. For the moment, it looks like the crank fuelling is OK for your needs, but you could experiment with it a bit to see if you can get the run up perfect.
The flare is not as high as I would have expected. Not sure what your target idle speed is, but I'm assuming this is a start and idle, in which case I would normally aim for a flare peak of around 100 to 200rpm over target idle speed, which would seem to be about 1100rpm, so you should flare to about 1200. You can do this aither by increasing air (need to balance the cold requirement against the hot requirement bearing in mind the range of the bypass valve) or sometimes spark advance, and possibly adding a bit more fuel if you are currently on the lean side.
On the spark note, is that actual spark timing thats logged i.e. degrees BTDC? If so you seem to be running very retarded. I would expect to see between 10 and 15 deg BTDC at idle, and much more advanced then that when the throttle is pressed. However, that is not fixed in stome, and epends heavily on the idle air settings.
On to the bit we had concerns with, the area immediely after start. I'm a bit surprised by how active the pulsewidth is - its up and down all over the place! But looking closer thats because its following MAP. Whats going on here? Throttle press? Doesn't seem like idle speed bypass activity as that seems to be flat out until 510s. However, with the MAP unstable it's difficult to draw conclusions about the fuelling.
Lambda trace - not sure whats going on there. Why does it suddenly jump up from 0.6 to 0.8 at 500s?
So in summary, it would be good to see a log where lambda is working right from the beginning, the load is stable (should be atmospheric as start of cranking and drop quickly to the pressure for idle). However, from the log we have it looks like crank fuelling is OK, maybe a touch lean, afterstart fuelling has the right decay time, but not sure about the quantity, and warmup fuel is about right. However the spark and air side of things seems a bit screwy, and everything changes at around 500s for some reason, where lambda starts reading, IAC valve ramps down (to control the increase in speed that occurred at 492s) and spark strts to be advanced of 0deg again.
I aint a clue whats going on thus why i asked :D
im not using any ignition control yet mate,
still running on a dizzy,
Ahh, maybe I've presumed too much?
So, tell me:
Was this a simple start and idle (i.e. you didn't touch the throttle at any point)
Are you using an idle air valve (or similar) or just a fixed throttle stop?
Are you using closed loop wideband lambda control?
What is the normal idle speed cold and warm?
Anything else you think is worth mentioning?
I'd certainly advise going to 'proper' spark control as soon as possible. You'll find the gains in driveability and probably performance are well worth it :)
well went round to the car tonight, and it was the same as the other day, starts up runs for few seconds at around 1100-1000 rpm then dies down to around 300 then picks up again and then idles,
have changed a few things in the afterstart table, but im clutching at straws
The settings below is what i have changed tonight to try after work tomorrow.
changed primepulse[ms] from 2.0 to 3.0
changed Hot start temp scaling [%] from 9.0 to 14.5
changed crank cold PW from 7.5 to 9.0
changed Crank warm PW from 2.0 to 3.5
changed Cranking threshold from 300 to 400
Quote from: cliffb75 on February 19, 2007, 07:01:35 PM
Ahh, maybe I've presumed too much?
So, tell me:
Was this a simple start and idle (i.e. you didn't touch the throttle at any point)
yes, the only time i touched the throttle was at the end when i reved it to about 1900rpm
Are you using an idle air valve (or similar) or just a fixed throttle stop?
Yes using the rover idle control valve
Are you using closed loop wideband lambda control?
Yes closed loop with wideband lambda control
What is the normal idle speed cold and warm?
1100 cold 950-1000 when warm
Anything else you think is worth mentioning?
not off hand :-[
I'd certainly advise going to 'proper' spark control as soon as possible. You'll find the gains in driveability and probably performance are well worth it :)
this will be once all the fueling issues are sorted
Make sure you send us the log to look at :)
For the purposes of this testing, it would be useful to see lambda from the start, so make sure you don't have any delay set, and turn the ignition on and leave it for about 30 seconds for the lambda sensor to start reading so that we get a log of the whole start. Once you've got the starts sorted you can put the delay back in to protect the sensor.
Rob, am I looking at the right things on the log? Iac DC is the idle air valve duty cycle right? Have a look at the coldstart07 log Tony sent the other day. What do you think is happening at 492 to 510 secs? MAP doesn't seem to tally with the IacDC to me? Whats your experience with the Rover valve - could there be a problem with it?
I had this with the TVR - same parts. The rover valve is a stepper and it can be a pain to get working... It has a very large range so it's easy for it to mess around without obvious sign. It sounds like the valve is about right when cranking, but is too closed during after start so is starving the engine of air. If you press the throttle a bit (only 2% or so - enough to not be in idle mode in the ECU) does the problem persist?
i will try next time i can get round he garage Dave,
if i open up the stepper, wont i have a problem of idling to high while cold?????
Here is an example for you. Its from a now out of production 4 cylinder 2L 16v NA. Obviously the actual numbers will not be applicable to you, but the shape and trends of the curves are what you are after. This was at +10C ambient temp after an overnight soak.
(http://i36.photobucket.com/albums/e8/cliffb75/VEMS/10examplestartlog2lNA16v.jpg)
LA3 lambda is lambda ;D, ti is injection pulsewidth in ms, nmot is engine speed in rpm and ps is MAP in mbar
Important point to note is the shape of the ti curve. Notice how much fuel it is putting in for crank and afterstart, but how quickly it is removed. This also looks even more because of the load effect, but never the less you do need to add A LOT of fuel in the first few combustions compared to once the combustion chamber has some heat in it.
Compare that to your log with 13ms during cranking and then 6 ms when running, though you are running quite rich (0.8).
So as a guess, try upping the crank cold pulsewidth up to around the 30ms mark and see what happens. If it won't start you have definately gone too far! So take the fuel back out and get the car started, warmed through and tray agin next day with about 20ms. If it stumbles during the runup with 30ms but then is happy you know that is a little too much for the crank fuelling, but more is needed in the afterstart. Warm the engine through and leave it for another start next day with the revised numbers (less crank, more afterstart). If its starts and runs great, either leave it if you're happy, or try adding more until you go too far.
Its not rocket science or anything. Thats how we have to do it :D
well changed to 20ms of CPW and the same thing tonight when i went round to start her,
fired up ran then revs died to near stall then picked up again and idles as it should :'(
Also i know this is a bit off topic, is there any chance between us all we can get an istruction manual done for what each setting in megatune is for and does, i know many of us have work comitments, BUT i think this would help new vems users by far. ( including me )
Need to see the log - did you actually achieve 20ms at start?
Remember that pic - 90ms at 10C. You're still a long way off that.
Am starting to wonder if its something else though. Using a dizzy may not be helping if its timed on the retarded side at low load.
Send us the log of the last start.
:)
will have to do a log tomorrow mate as never had laptop on me..
how do you get the lambda to read from crank?
as went round today, left ignition on for at least a 1min, started car and the lambda was off, as if it had not warmed up. then after about a min of engine running as normal the red and green status bar started reading ??? ???
have i got to turn something off or on in the settings some where?????
once we can get the lambda to read from the start i will do another log mate,
Pity there is no one down this kneck of the woods that is clued up on the vems :'(
Where abouts are you again? (PM me if you don't want to write it in public) If it's within easy reach when I'm next on the mainland I could pay you a visit... Not sure when that'll be though.
There's a lambda warmup parameter lurking somewhere in megatune. VEMS ignores the readings until this time is up (measured from after cranking IIRC).
Im near Newbury in Berkshire Dave
Not too bad for me then... I need to visit Oxford in the next couple of weeks, so will be in the area.
im about 2 miles from the A34 Dave
6 miles north J13 A34/M4 interchange
i will still do a data log in the morning for every one to look over.
also any one give me a step by step guide on calibrating my WBo2 want to make sure this is correct also, i read somewhere something about a terminal program ??? ???
You can't calibrate with a used sensor. I'm pretty sure that we had the sensor calibrated by Richard?
ok Rob,
maybe im getting a bit paranoid ;D ;D
Hi,
have latest datalog and .msq file below .......
http://www.capriracing.co.uk/vems/vemsdata2.zip
Right then. Your data log
(http://i36.photobucket.com/albums/e8/cliffb75/VEMS/tonycstartfeb07.jpg)
So it looks like you are still too short on the crank and afterstart pulsewidth (max 13, but you're running 5 once the lamda sensor has kicked in, to get 0.85) I would try increasing it lots more - like double it again. Having said that the runup and flare are really nice
But the more interesting thing is what happens at about 85secs, same as your first log. What is happening? Why does engine speed increase? IAC then ramps down to control the idle speed, and everything looks good.
Before this point, you can see that the engine is not actually achieveing target speed, its ramping up to it. The first log you sent did the same thing (ramping up, then overspeed for a bit, IAC ramps down and idle speed under control)
Does the engine have some sort of additional device for opening the throttle stop (the CA18DET has a wax capsule thingy in addition to the idle valve)? If so, is it operating properly? is it sticking until temp get up a bit or something?
Or, Is the power to the IAC delayed for some reason? (so it thinks it is active but the valve remains closed)
Or, Does the idle valve do something wacky (like close) when the IAC duty reaches 66% (66 was the max value on your last log too), or is the signal inverted (66 means closed)?
I'm wondering if the near stall after start and the flare later are linked somehow? e.g. why does the IAC duty drop when the engine nearly stalls at 42.4 sec?
Anybody else got any suggestions?
???
im glad its got you baffled too :D :D
I have a similar starting behavior on an Audi 4.2l engine even without idle control. When the engine starts the plenum is filled with air at atmospheric pressure, this is enough to let the engine overshoot on startup. The high rpm then pull a strong vaccum which will not even out quickly when the rpm falls back down again. This will cause the pulsewidth to be all over the place as well.
First we have the PID parameters where I'm pretty lost, but the integrator limits seem a bit high. Try setting ingegral decrease limit to 32 and integral increase limit to 64 as a start but after that you should stick to the "One setting at a time" rule.. The normal problem is "integral windup" and the limits usually help a bit.
You can possibly use "Extras->idle settings->Idle afterstart RPM, added value (rpm)" to allow a larger overshoot on startup, while keeping the "one setting at a time" rule in mind you can set it to 300 or 400 and see what happens. But we also risk an even larger overshoot, it depends a bit on the flow and speed of the stepper.
I'm sure that we can get the starting behavior better.
Jorgen Karlsson
Gothenburg, Sweden.
VEMS hardware development
Jorgen I hear what you are saying, and agree with the principle. :)
In this case though the IAC isn't doing much after start. In the first log where the engine showed the same engine speed profile, it just stayed at 66, so while what you are saying is correct in principle, I'm not sure it applies here.
Either way, that still doesn't address the issue thats bugging me - what the hell is happening at 85 secs? Something must cause the engine revs to suddenly increase. For those few seconds the speed is high and the MAP low, and then it all comes back under control, to similar values (MAP and injector pulsewidth) that it had before the speed increased. The only difference is that the IAC duty has ramped down. It suggests there is extra air coming from somewhere, but what would suddenly allow extra air after 85 secs? Either that or the ignition suddenly advances, but if you're still using a dizzy, I don't see how (unless that has some weird afterstart retard function?)
You're right Tony, it has got me rather baffled. ???
;D ;D ;D ;D ;D
im glad my car is still being a bitch after 10yrs
Quote from: cliffb75 on February 26, 2007, 08:20:22 PM
Jorgen I hear what you are saying, and agree with the principle. :)
In this case though the IAC isn't doing much after start. In the first log where the engine showed the same engine speed profile, it just stayed at 66, so while what you are saying is correct in principle, I'm not sure it applies here.
I think that it does, my car does the same and it has no idle control. My theory is that the idle control seem to be too slow to handle the panic condition when it goes from start to run mode and find itself 5-600rpm to low. What it doesn't know is that the engine is allready shooting for 1500-2000rpm because of the high plenum pressure. If the idle control is quick enough to open up the valve a bit it will make the condition even worse.
The engine will shoot toward high rpm and will then run out of air as the plenum pressure has been equalized. This will make the engine rpm fall very quickly, my engines rpm will fall like a rock to 200-300rpm after the overshoot if there is no idle control. It doesn't help if the idle control has paniced and closed the idle air valve when it sees the overshoot.
We first need to try to set up the idle control to deal with this problem quickly to prevent the overshoot at the beginning as much as possible and then it need to quickly open up the idle air valve when the rpm start to fall after the overshoot. I don't know how to handle this as most of it is out of our control but increasing the afterstart rpm to 1400-1600rpm to let it try to stabilize at that rpm for 2-6 seconds before decreasing to the normal cold idle could be a workaround. Some idle PID tuning will most likely make it work better as well.
Can the rpm buildup at 85 second be reproduced? I ignored it as I assumed that the TPS calibration was out.
Jörgen
QuoteWe first need to try to set up the idle control to deal with this problem quickly to prevent the overshoot at the beginning as much as possible and then it need to quickly open up the idle air valve when the rpm start to fall after the overshoot. I don't know how to handle this as most of it is out of our control but increasing the afterstart rpm to 1400-1600rpm to let it try to stabilize at that rpm for 2-6 seconds before decreasing to the normal cold idle could be a workaround. Some idle PID tuning will most likely make it work better as well.
where do i set that ???
as every where i look there is afterstart this afterstart that :o
thanks for all your help guys.
There's a setting in the "general idle controls" thingy in megatune for setting an addition to the idle speed for afterstart. (I think - it's been some time since I used Megatune!)
As for PID tuning, I sent Rob a recipie for doing this that I used sucessfully on mine. I will see if I can dig it out.
I was going to post that this morning but I realised that its on my laptop at home rather than my PC at work :(
Plus its your work so you may as well take the credit/flak for it! ;D
LOL. I have the same problem working on at least 4 different computers in a day...
I'll dig the words out when I get home.
Are you talking about a ziegler nichols oscillation method? http://www.jashaw.com/znclosed.htm (http://www.jashaw.com/znclosed.htm)
Works as a starting point, but generally still needs fine tuning.
Also for idle speed control, the PID terms generally need checking at a range of temperatures as you find that the optimum terms when its warm tend to be too aggressive when cold, since the IAC is a volume device not a mass device, so the load varies more when the air is dense.
In modern systems we use modelled engine drag torque to predict the required air mass, hence avoiding overshooting the target. We also tend to use a variable target to improve the return to idle. For the start and afterstart there are also various conditions on what controller parts turn on when (i.e. hold out the air path integrator until a certain condition) to avoid the problems Jorgen is describing with integrator windup due to beeing a long way from target.
However, I still reckon looking at Tony's log data we are not getting the valve closing causing the problem.
If Tony was running spark control we could use the 'ski ramp' ignition timing I described somewhere else to help this situation. Buts thats a sticky plaster really, not a cure for the problem.
A very slight variation on strategy to get to the ultimate gain, but yes, it's the same old ziegler nichols method in the end :)
I did find that most of my starting issues went away if I cracked the throttle a little while starting. I always presumed this was down to the stepper being turned off, but I'm not so sure now. I need the engine back in the car to play some more!!
so what do i do at present?
not touch any thing and wait???
or adjust some settings??
Cheers
Quote from: Tony C on February 28, 2007, 07:02:05 PM
so what do i do at present?
not touch any thing and wait???
or adjust some settings??
Cheers
Play of course! ;D
For one thing, thats why you went for VEMS, so you could get stuck in and have a go.
And second, it ain't gonna fix itself. ;)
The important bit is to be meticulous with your record keeping. Last time I did start calibration work I made a simple sheet with date, ambient temp, coolant temp, calibration name and log name on it, and filled it in for each start I logged. Later on (end of the day normally), I looked through the logs and added time to fire, peak flare (this is delta above target), lowest lambda (rich dip) and any notes worth mentioning (speed dip, lambda went lean etc etc). This allows you to quickly go through and see what is good and what is bad, and pick the calibration settings accordingly. You can then steadily home in on a good calibration. As you build up this databse of info, you will also start to get a 'feel' for what the engine wants, so if you do find a poor start in the future you wil have an idea how to sort it.
Go for it!
BTW have you got the lambda working right from the start yet? This will really help you out with knowing which way to go on the fuelling.
As long as you save the changes and note what is good and what is bad, you can always step back.
no still not got the lambda working from the start yet mate.
I can't tell you what to do as I have very little experience with the idle control. But if I would start by lowering the integrator limits. (Settings->extras->idle settings advanced/PID.) Integrator increase limit is currently at 112 (or something like that) and integrator decrease limit is 64. Decrease these to 64 and 32 respectively and see if it changes anything.
I actually doubt that the above will make a big difference but I think that it's a change in the right direction and that it will work better together with future cold start tuning.
My next step would be to change the "Idle afterstart rpm added value" to 400 to make the target rpm 1400 or 1500rpm right after startup. This should allow the natural oscillation of the engine to stop before it drops the idle target to 1100rpm or so after 4 seconds. As I'm not a software guy I have no idea if the added rpm is just removed after 4 seconds or if it fades out over 4 seconds. But I guess that you can tell me in a few days :) If it's just removed after 4 seconds we will add this to the task list for the programmers.
Jörgen
QuoteI can't tell you what to do as I have very little experience with the idle control. But if I would start by lowering the integrator limits. (Settings->extras->idle settings advanced/PID.) Integrator increase limit is currently at 112 (or something like that) and integrator decrease limit is 64. Decrease these to 64 and 32 respectively and see if it changes anything.
QuoteMy next step would be to change the "Idle afterstart rpm added value" to 400 to make the target rpm 1400 or 1500rpm right after startup. This should allow the natural oscillation of the engine to stop before it drops the idle target to 1100rpm or so after 4 seconds. As I'm not a software guy I have no idea if the added rpm is just removed after 4 seconds or if it fades out over 4 seconds. But I guess that you can tell me in a few days If it's just removed after 4 seconds we will add this to the task list for the programmers.
Did both the above,
and yup still the same, if anything it felt worse, as if it tried to die twice,
did a datalog of the start up also
Well lets see the log then :)
will get the log up shortly
ta mate
just looking through MT,
would i benefit from setting in the injection settings Settings-> Injector Settings the fire all banks while cranking? its set to alternate at the moment.
Altenate is fine. It just means it fires the injectors as normal during start IIRC
Without ignition control you should disable the ignition timing base idle control as it can slow down the idle motor a bit. You find it under Extras->ignition settings advanced.
I was afraid that the dual stall behaviour could happen with the new settings. A log would help but I suspect that we can drop the "Idle afterstart RPM, value added" value down to 100 again. I we probably need some code tweaking before an high afterstart rpm will work properly, at the end of the period the rpm target seem to be lowered suddenly instead of fading out.
Under Extras-> Idle settings Advanced, we find "Assymetric PID conf", try setting that to enabled. IIRC this fairly undocumented feature will make the PID more responsive to low rpm then it is to high rpm.
Then there is a setting that I don't find any definition for in a stepper application. It's under Extras->idle settings general and is called "Idle actuator speed/PWM frequency". It should be set to 6 or 7, yours is currently set to 0.
Cheers Jorgen,
will try these settings the weekend,
thanks for every ones help so far...
just booted the laptop up,
and cannot find them settings you posted above on my Megatune Jorgen,
is there another version of MT i should be using????
just found the latest version of MT,
downloading this to laptop now, will i need to upload any other software to the ecu when using this latest version?????????
just loaded the latest version (i think) of MT, opened my stored .msq file and it came up with a box with errors,
it said something about values wrong, and not to upload to ecu :(
QuoteWithout ignition control you should disable the ignition timing base idle control as it can slow down the idle motor a bit. You find it under Extras->ignition settings advanced.
cannot find this mate, im now using MT 1.0.53
The MegaTune in 1.0.53 release will probably not work with your current firmware - if you check the version number on the top bar of the window it will tell you what firmware version you are running
Rob
Hi Rob,
i hope this is the right one:
on the old MT it says version 2.25 beta built on Oct 15 2005
on the 1.0.53 it says version 2.25 built on Feb 5 2006
Stick with the earlier megatune or upgrade the firmware to one of the the newer versions. Upgrading is not a trivial task though.
ooops been playing with the newer MT but with the old firmware :(
how do you update the firm ware mate???
mmm sounds like another post for you guys on firmware updating,
still having grief with cold start :(
it idles around 400-500 rpm then picks up to the set 900-1000 rpm at around 77C
Question is - is this a IACV or mixture issue?
right been playing again,
she fires up when cold then stalls after a few seconds and then on restart fires and idles around 800-1000 rpm,
which is better than before,
im heading the right way slowly :D
Increase the size of the afterstart parameters... They do seem to need to be large.
which bits Dave?
In MT in priming/cranking/afterstart in the settings menu there are 2 parameters called afterstart enrichment added value and and afterstart enrichment scaling. These need to be fairly big, otherwise you risk actually adding LESS fuel than when the car is warm!
I don't remember the actual values I use, but I will look at the car at lunchtime.
cheers Dave,
Didn't get out at lunchtime! Damned people wanting me to tell them what's wrong with their radars ;)
I use 70 for the scaling and 30 for the added value. It seems to work as I can start the car with no throttle now.
hi mate.
is that the afterstart enrichment scaling at 77c % you set to 70?
and afterstart enrichment added value % to 30?
That's it :)
will go try this now, ta mate.
well she started from cold (before changin the above)
and near died then picked up to 900,
its this near diying i need to cure now
i set the above settings as per yours dave, starts good when hot will see if its any better when cold in morning,
ta again mate.
I was wondering that did you get this problem cured?
IÃ,´m having same kind of problems.
nah i aint cured it as of yet,
i changed a few things but never made any difference :(
so left it as was,
at last we are getting somewhere.
dnb is a star. the car runs from cold now, not sure if dave has any more tweeks to do from the datalogs he asked for, but sucess