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Mapping / Start Up Tuning


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10 replies to this topic

#1
B1ack_Mi16

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Ok, I'm having some problems with mapping the start conditions on my T16 running on MS3 Pro.

 

With cold engine I'm running stepper opening of about 75 steps (306 Gti inlet with stepper).

 

But to get it to start hot I need to up the steps to about 85-90 and it revs to 2500-3000rpm before it settles down.

 

I'm suspecting there might be too much fuel though added during hot start and that's why I need so much air?

Can anyone confirm that en additional air-supply for a hot engine should be less than for a cold engine during startup?

 

I was thinking maybe the opposite was correct earlier due to heat-soak etc, meaning more air would be needed as it ain't as dense, but after fiddling around with the settings for a while now I can't seem to get it right.

 

Any tips? Others running MS with stepper motor, if so I would be interested in seeing the tables for the stepper motor but also additional fuel etc.

 

 



#2
wicked

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Can't check my map right now, but do you have the over run ignition cut enabled during idle? It switches the ignition off if the throttle is closed and the engine runs more than 1500rpm for instance.

#3
B1ack_Mi16

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No haven't activated that as far as I know. 

 

Basicly haven't done much apart from dialling in the Fuel and ign main maps, and fiddling with the starting. But basicly it gotta have too much air anyway as the revs are too high.

So I have to work from that I believe.

 

But any nice afterstart enritchment tables, and cranking pulse tables would be nice if for a 2.0 16v engine.



#4
Thijs_Rallye

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Normally you don't have a closed loop during cranking/starting so I don't see why the revs should shoot up to 2500 / 3000 during hot starts because of the excess fuel.

 

A lean mixture or fuel starvation will up the revs normally. (learned from my 2 stroke era)

 

Does the MS3 inject immediately when you start cranking? Or does the engine have to turn over 2 times first to sync the ECU to the crank/cam trigger? (in other words, are you running sequential injection?) Does the MS3 have a separate hot-start map (i.e. ignition timing)? 

 

I think with the "standard-operating temp" idle injection time and stepper position the engine should be able to start, but I guess you've tried that before.



#5
B1ack_Mi16

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Yes hot stepper position idle is 0 steps, i.e. fully closed, and it runs of the throttlebody opening alone at 850rpm ish.

 

I think it might be getting far too much fuel as if I just blip the throttle it starts straight away.

 

Not sure if the MS3 has separate hot-start map regards to ignition timing, but at least as you say, it seem to be shooting a priming pulse of fuel when ignition is turned on, but before cranking starts.

 

I have to investigate this more during friday and saturday, I have test run plates for those two days now :)



#6
Thijs_Rallye

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https://www.diyautot...startup-tuning/

 

 

 

When the key is on, the MegaSquirt will turn the fuel pump on for 2 seconds and fire one priming pulse to clear air for the lines. (You can disable this feature by setting the priming pulse to zero in most firmware versions.)

 

;)

 

Another useful one:

https://www.diyautot...ing-megasquirt/


Edited by Thijs_Rallye, 23 August 2017 - 08:01 AM.


#7
B1ack_Mi16

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Yes, I've read it. But now I think I've found something that might be related to my problems.

The FlexFuel sensor seem to go into "safe" mode just after I start cranking, adding 1.63 times extra fuel! That might well just drown the whole thing I suppose.



#8
Thijs_Rallye

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Do you have the prime pulse enabled or disabled?

And as for the flex-fuel sensor, I can imagine this won't help either. How is the sensor fed, from the ECU or a seperate 12V supply? For the sake of the experiment you could try to disable the flex-fuel compensation but I don't know how easy that can be achieved with a MS.



#9
B1ack_Mi16

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I can turn off both, and I will try that tomorrow indeed. Both the priming pulse and the flex fuel sensor, at least I'll set the flex fuel fallback value to 100% instead of 163% as it is as standard.

That should possibly make things more logical :D



#10
B1ack_Mi16

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Btw. just to update on this one. 

 

Once I got the 163% fallback failure additon from the flex fuel sensor set to 100% it now acts as it should and startup mapping is again acting logical :D



#11
Thijs_Rallye

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Nice to hear you've got it sorted!