VEMS Community Forum
VEMS => Configuration => Topic started by: [email protected] on June 21, 2007, 10:13:24 pm
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I've drawn this up as an attempt to describe the states that VEMS goes through from start-up to idle.
(http://www.vems.co.uk/VEMSUserManual/PrimingCrankingAfterstart.png)
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Just a couple of observations about Afterstart
I presume the warmup enrichment table isn't applied at all in afterstart since it isn't mentioned.
How is the afterstart enrichment scaling applied?
As (VE_calc + Afterstart_added)*afterstart_scale or as VE_calc + (Afterstart_added*afterstart_scale)?
(Syntactically unnecessary brackets added for clarity ;) )
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I've just been looking at the afterstart thing again - there's not enough information to work out the scaling. What temperature is the afterstart_added parameter scaled to 1? (I suspect at -40c) If this is the case, then if the afterstart_scale parameter is too small (ie less than 22%), then it'll result in reducing the base pulsewidths from the map table. I suspect this isn't desirable as it would be easy to get to zero pulsewidth above 77C!
Anyone care to comment about my interpretation?
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Can you look at this config:
http://www.sendspace.com/file/n0v2vg (http://www.sendspace.com/file/n0v2vg)
I can't cope with the normal starting of the engine. Whether the engine is warm or cold I have a very long spining time and move the throttle to start the engine. Sometimes, when the engine for a long time will not catch, after start it able to show a trigger error.
Injectors are LowZ 750cc/min@3bar with series resistors.
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Does someone have any idea?
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Do you have a datalog to go with that?
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No, but i try to do that.
Here it is:
http://www.sendspace.com/file/9aa1ne
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More details about the engine?
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Stock Audi 2.2 20vTurbo (5cyl)
Holset HX35/K26 hybride, series triggers (135 tooth on flywheel, 1 pin on flywheel and Hall on cam), Injectors, as I wrote 750cc/min LowZ with 7,8ohm series resistors, 5 coils. Flywheel is a series audi dual-mass.
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Have you tried to lower the pulsewidth?
It looks a bit high for 750cc injectors.
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Have you tried to lower the pulsewidth?
It looks a bit high for 750cc injectors.
I'm trying many different configs. Starting from 19ms on crank cold and 5.2ms on crank warm to 7/3 and engine still won't start. Maybe crank advance is wrong?
And what is the "cranking threshold"?
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I don´t know what that means,
19deg advance for starting it a little high, try 10.
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You really need to check the cranking advance with a gun - then you need to look at the amount of fuel you're putting in at cranking - what PWs are you seeing? I always start with a rule of thumb of cold cranking = 3 x Req Fuel, warm cranking of 0.75 x Req Fuel.
You may have flooded the cylinders - pull out the plugs let the cylinders breathe and give the plugs a clean.
Check that you have a good spark - I always do a visual check to see that the spark plugs are sparking - make sure that the fuel pump isnt powered.
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what PWs are you seeing?
During the cranking, PW is about 8-8.7 (outside is -3.5 degrees).
You may have flooded the cylinders - pull out the plugs let the cylinders breathe and give the plugs a clean.
Done
I always start with a rule of thumb of cold cranking = 3 x Req Fuel, warm cranking of 0.75 x Req Fuel.
I try this tomorrow.
You really need to check the cranking advance with a gun
In this engine is 5 coils, all under one, common cover, which also attaches it to the head. Maybe I can run the gun directly from VEMS?
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You really need to check the cranking advance with a gun
In this engine is 5 coils, all under one, common cover, which also attaches it to the head. Maybe I can run the gun directly from VEMS?
I have used a regular spark plug lead between the #1 cyl coil and spark plug, must be done on all Coil-on-Plug engines basically - unless you can trigger from something else (not likely).
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I always start with a rule of thumb of cold cranking = 3 x Req Fuel, warm cranking of 0.75 x Req Fuel.
I try this setup, and something about this values.
Yesterday, when I'm trying to start up the engine I set:
cranking Treshold at 700rpm and
crank advance to 22deg
and the engine start up. Then it was starting for each turning of the key.
Today, again, does not want to start, I change the settings and it does not respond. Only shoots in the exhaust from time to time.
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crank threshold of 700 seems very high to me. Try something like 200 (there is a small issue in the firmware that means it will really be 300 - which is good for normal car engines)
Also, 22 degrees advance seems way too much. 10 to 15 would be more reasonable.
Most engines will start well if they have been running no matter what the start settings are - there's plenty of warm fuel in the cylinders. I would suggest slightly more fuel than Rob suggests to start with, then reduce it when it runs. You also need to look at the afterstart enrichment to make sure the engine continues to run.
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crank threshold of 700 seems very high to me. Try something like 200 (there is a small issue in the firmware that means it will really be 300 - which is good for normal car engines)
Also, 22 degrees advance seems way too much. 10 to 15 would be more reasonable.
Most engines will start well if they have been running no matter what the start settings are - there's plenty of warm fuel in the cylinders. I would suggest slightly more fuel than Rob suggests to start with, then reduce it when it runs. You also need to look at the afterstart enrichment to make sure the engine continues to run.
Today I made another tests. Engine starts up on settings as previously, but with crank treshold set to 300rpm. But when I turn off the engine, it won't start any more. I discharge 2 batteries for cranking, I changed the settings each time and engine makes itself heard, but can't start.
PS. Maybe someone would like to share with his own settings of priming cranking & afterstart for Audi 5cyl engine?
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What firmware? And are you using VEMStune or Megatune?
I ask because I think there might be an issue with scaling for some VEMStune starting parameters - I am investigating it because my car wouldn't start today when I tried to make what I thought was a very minor change.
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After you get it started and it idles,
What is the AFR and the injector pw?
If it´s 14.7:1 then you should be trying to use just about 50% pw then what it takes to idle.
like 2ms at idle, that would be about 3ms cranking.
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What firmware?
Everyday 1.1.27, yesterday I tired 1.1.63
And are you using VEMStune or Megatune?
I tested Cranking on both.
After you get it started and it idles,
What is the AFR and the injector pw?
On cold engine AFR is something about 13. PW is 1.5-1.6ms.
I try setup with 2.5ms on crankings. Engine still won't start...
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another thing that is not good is the low impedence injectors you are using. Audi does not seem to like them very much and more settings need to be made for them to work properly.
for your setup i can tell you that the siemens deka 630cc should be more than enough and lots of audi users have them already and they work very nice.
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another thing that is not good is the low impedence injectors you are using. Audi does not seem to like them very much and more settings need to be made for them to work properly.
for your setup i can tell you that the siemens deka 630cc should be more than enough and lots of audi users have them already and they work very nice
And on what injectors you runnig?
Tomorrow I will be started and tuned another car on vems, but with listed by You, 630cc/min siemens injectors. Maybe it will be starting up better then this.
PS. My friend has 1000cc/min injectors in 2.0 16v engine. The car rides on megasqiurt and have no problems with cranking
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OK. Other car, running on 630cc/min injectors starts up. In next week, i try tu run car with series injectors.
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Hi,
Check if "fire banks while cranking" under Basic Settings->injector settings is set to "all banks" or "alternate". I usually have it set to "Alternate" as it's the only option for cars with many lowZ injectors. Cars with highZ injectors can use any setting, but there is no benefit in using "all banks".
If it's set to alternate you should try around 8ms hot and 12ms cold on the Audi I5 with 630cc injectors, it's better to have a bit to much fuel then to not have enough.
Also, when starting the car. Try holding full throttle for a second or two at first, then release the throttle when you want the car to start. Full throttle while cranking turns off all cranking fuel to clear the cylinders. The feature is called "Flood clear". If you always need to do this when the car is hot it is likely that you inject a bit too much fuel while cranking.
Jörgen Karlsson
Gothenburg
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Car with original, HighZ 320cc/min injectors starts up very good. With 750cc LowZ won't start (I tried every config from the planet and the engine begins to speak as some cycles, but may not enter into afterstart and warmup).
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Can anyone pls clarify the following:
- Cranking Advance is the actual total advance and not a value added to ignition table value. i.e. Set to 18deg, I should see 18deg BTDC with my timing light? True or False?
- Cranking Threshold is the threshold where cranking becomes afterstart? True or False?
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1. absolute
2. It is the margin where cranking fuel calculations/strategy oversteps to running fuel calculations/strategy. Yes, it is also start of afterstart if it persists at given temperature.