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BigAl
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Joined: 06 May 2003
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Location: U.K Surrey
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 Posted: Sat Jan 10, 2009 12:07 pm Post subject: motronics ML 4.1 question |
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Hey guys, i have kinda asked this question in one of my other threads but thought i'd start a new one so it doesnt get missed.
does anyone know at what temperature the motronics ML 4.1 system in my 16v 33 running with no lambda correction, switches away from engine cold fueling?
I ask as i have a stuck open thermostat and after ordering one and them getting the wrong part and then asking another place to put one aside for me and then selling it, i am not having much luck in finding one, i am waiting for a new order to come in now.
The engine temp sits at around 60 ish on long runs due to the cold weather and my MPG has shot down because of this, hence my question.
Will the same cold fueling be used if i were to run with lambda correction? I need to buy a new lambda but dont want to fit it if it would be damaged from constant over fueling.
What resistor value do i need to replace the CTS, after i have got the engine warm a little?
Hope that makes sence, thanks
Alan
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bobbber
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Joined: 14 May 2003
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Location: The Greatest Town on Earth - Swadlincote, UK
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| Posted: Sat Jan 10, 2009 2:01 pm Post subject: |
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Al,
As long as the engine is running, be it rich or lean or perfect mixture, it should run at 90 degrees or whatever the standard running temperature is. You cannot AFAIK, adjust the fueling to change the running temperature greatly.
You ALWAYS get low mpg on a cold running engine, due to higher friction.
You DEFINATELY need a new thermostat - one of the problems of using a "stuck open" one is the additional engine wear.
Bob
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BigAl
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| Posted: Sat Jan 10, 2009 2:45 pm Post subject: |
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Hey bobbber, yer I know I need a new thermostat  I have been trying to get one  but until then I cant do anything about the engine temp.
AFAIK there are maps stored in the ECU and according to the CTS the ECU either ups the fuelling, acting as the choke, or uses different maps with more feeling. Once the engine gets to a certain temp the CTS tells the ECU to either use a warm/hot engine map or a warm engine fuelling.
What I don’t know is if when running a lambda sensor if anything changes. Does the cold fuelling, acting as a choke, get overridden by the lambda sensor? If not I didn’t want to risk damaging a new lambda sensor if I can’t correct the fuelling, with a resistor telling the ECU that the engine is warm.
When I eventually get my thermostat then no problem.
There is a thing you can get that changes the CTS/AT telling the ECU that the engine/air is cooler and so ups the fuelling, i want to do the oposite
Multimeter set to 20 kOhm, should get
-10C = 9 kOhm
0C = 6 kOhm
+10C = 3.8 kOhm
+15C = 3 kOhm
+20C = 2.5 kOhm
+25C = 2.1 kOhm
+30C = 1.7 kOhm
+40C = 1.2 KOhm
+60C = 600 Ohm
+80C = 330 Ohm
i guess i could just use the normal running temp value for 80C, 330 Ohm, but thought it would be better to run at a temp where it just switches over from cold running to normal running
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paulhide
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Admin
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Joined: 19 Feb 2003
Posts: 1223
Location: Stafford, UK
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| Posted: Sun Jan 11, 2009 10:33 pm Post subject: |
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Hi
Would expect it to base running on the lambda sensor when its feedback starts to make sense (when it warms up) rather than just base it on engine temp.
All the best
Keith
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BigAl
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Joined: 06 May 2003
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| Posted: Mon Jan 12, 2009 12:46 am Post subject: |
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hey keith, wouldn't that then cancle out the "choke" effect of cold fuelling and cause stalling, or would that be done by the idle valve?
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Admin
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| Posted: Tue Jan 13, 2009 2:01 pm Post subject: |
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Hi
Good point, although it might want a richer mixture feedback from the lambda probe until the engine is up to temp.
Many cars use heated lambda probes to get them up to temp quickly. Seems pointless if they are going to be ignored for 10 minutes because the engine is cold.
All the best
Keith
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BigAl
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| Posted: Wed Jan 14, 2009 1:57 am Post subject: |
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keith
thats what i thought, i picked up my new lambda sensor today and asked if i should put it in now or wait until i have my new thermostat fitted and they said wait until you fit the thermostat and have i checked my CTS, "yes"
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