Good info. Please keep us posted. I am on the road currently, but if needed I will post my advanced start options screen so we can compare notes when I get home in a couple of days.
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Video of cold start problem in our CTSC'd NSX...
- Thread starter GhettoRacer
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the "Start Extra vs Temp" will have no effect on cranking either when cold or hot. This table is only in use after the car has reached the "Crank Exit RPM" this is typically set to 400rpm.
The table to play with to get the start fuel correct is the "Crank Injector Time Table" it is in the "Engine Start" template. The best thing I can tell you to get this right is when the engine is cold and you crank it, if it does not start like it does when it is hot try cracking the throttle a little bit (maybe 2-3%) if it starts then you have to much fuel and not enough air. So you need to reduce the "Crank Injector Table" untill it will start without the use of the throttle. If you do not have enough fuel it will not start when cold. So increase the Crank Injector value by 10% at 0% throttle and try to start again. repeat untill it starts everytime. You may have to revisit this table in the winter if the temps drop. It is hard to put in too much fuel on startup, if you do flood the engine it is recommended that in the "Crank Injector Time Table" that you have the 80% throttle and higher part of your table set to zero. This way if you do flood the engine at startup you can simply hold the throttle to the floor and crank the engine to clear out the fuel without adding any more.
The "Initial Crank Pulse Table" will rarely be adjusted and is a one time shot of fuel that is injected as soon as the engine starts to crank but before the Cam or Crank Sync has been established. This is sort of like the OEM ECU's batch fire of all injectors but the amount of fuel injected for this is based off of coolant temperature. I have not had to adjust this to get a car to start correctly but could be of use for cars that sit for a long time or for really large temperature changes but most of these issues can and should be addressed in the "Crank Injector Time Table"
The "Start Extra Decay Table" and the "Start Extra vs Temp Table" are used after the car has started and has reached the "Crank Exit RPM". They work together to add additional fuel over time to help stabilize the Idle durring cold weather, but do not confuse this with cold start. If the car fires but then dies when cold you use these two table along with the "Warm Up Enrichment Table" to help it stay in idle untill the engine has warmed to normal operating temps.
As far as timing goes start with the "Crank Adv" set to 10-15 degrees, most cars will start in that range and you will never have to change it. Once the engine first fires the ECU will move to the "Ignition Map" and get the timing from there and add in the ignition modifiers. One of the Ignition Modifiers you can use to help keep an engine running right after startup if you are sure you have the fuel correct and the motor still wants to die or stumbles after startup is the "Ign vs Start Time Table". You can advance or retard the timing in the "Ignition Table" for a given period of time to help the idle stabilize. Again this is something that rarely has to be played with but on a big cam car it is something that may help to get the idle stable right after start.
Once you get it to start then you have to move onto tuning the idle. There are about 20 different things you can but should not play with to get the car to idle. There are fuel and ignition modifiers based on coolant temp, time, RPM, AC, and other sensors.
With these stand-a-lone ECU's just because you can change something does not always mean it is a good idea to change something. You make the minimal number of changes to get the desired effect. Make only one change at a time and measure the results. It takes time to understand what the ECU is doing and in many cases one change in a given table can negate or amplify a change you made in another table. Read the AEM documentation in the HELP files, most things are documented as to what they do but not how much to adjust and what the effect will likely be when adjusted.
Dave
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Dave, I was going from what the new AEMTuner v2.9 Function Explanation was saying. With this program, the "Start Extra vs Temp" is a coolant-temperature dependent multiplier to the "Crank Injector Time" table while in cranking mode.
Maybe the new AEMTuner functions have changed somewhat and I should probably shut up to avoid the confusion. Just like the AEMTuner discrepancy for the fuel pump priming time.
I really appreciate your explanations and am learning a lot from your posts. I hope you consider doing some classes for us as I would try to fly in and attend.
Dave
Your fine, the confusion comes from AEM changing the meaning for the same term in the new version of the software. Moving into the series2 units a lot changed and a lot did not. I just wish that if they made a change to a function they would rename the function so there would be less confusion. Still this is nothing compared to the differences between the domestic tuning software, the terms and effects change from year to year and model to model so you really only kind of know what to change to get the desired effect. The Chrysler tuning is by far the worst, just be glad you do not have a HEMI in there.
Dave
Thanks to some great input from DDozier I have my car's cold start completely dialed in. The Crank Injector Time Table had to be adjusted in small increments...three times. The initial setting was set to 44. At 48 the engine started better, but not perfectly. I inched the setting to 50, and once again it was improved, but not as good as I had hoped for. At 52 it starts perfectly. This is a stock engine with a low boost turbo setup running the 1st gen AEM EMS and 750cc Injectors. Thanks also to Cody and Devin for their help on the side.
Open sourcing these adjustments has been great. I look forward to more collaborative efforts as my skills improve. Thanks for the contributions from the highly skilled guys!
Open sourcing these adjustments has been great. I look forward to more collaborative efforts as my skills improve. Thanks for the contributions from the highly skilled guys!
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Manual says: "Crank Injector Time table
Units: Fuel vs Throttle %
Description: Fuel (bit value x MicroSec/bit) injected upon cam/crank sensor
synchronization when in the crank condition. If the engine cranks excessively and throttle input does not help, this typically means there is not enough fuel. Note: It is a good idea to take out fuel at high throttle conditions to clear extra fuel in the event the engine becomes flooded."
When does the cam/crank sensor sync occur? I imagine it is with in one engine revolution? What is the value exactly?! Is it possible to translate it to something more relate-able like millisecond?
Logically it makes more sense to me to play with this value since cam/crank sync occurs very fast... I know on our NSX it makes a very notable difference in cold cranking start.
Wow, our NSX is on AEM EMS 1 with 550 injectors. Current value is at mere 11 for closed throttle! I really didn't want to make huge increase of that number until I know exactly what it is doing but after asking this on my facebook (i have several very experienced tuner friends heh):
AEM EMS Manual says: "Crank Injector Time table
Units: Fuel vs Throttle %
Description: Fuel (bit value x MicroSec/bit) injected upon cam/crank sensor synchronization when in the crank condition. If the engine cranks excessively and throttle input does not help, this typically means there is not enough fuel. " How do you translate this into something easier to relate to? Such as milliseconds? Also does it take less than 1 revolution for the cam/crank sensors to sync up? As soon as it does it goes to the "initial crank pulse width table" right? — with Cody Guldstrand, Joseph Davis, Jeffrey Evans, Sean Burgess and John Nguyen.
Sean Burgess: Are you running a series 1 or series 2 ems.
Sean Burgess: Image appears to be series 1. This table Injects fuel only during cranking. This event doe not happen until stat synced is triggered. Data log the parameter stat synced. Typically series 1 ems does not sync until one full timing event is complete. Even if you have sync early checked.
Cody Guldstrand: My typical values range from 80-130.
Sean Burgess: before editing your own map, pull up some other maps from different cars from the aem files. This will give you an idea of what the table should look like. "My typical values range from 80-130." Cody gave you a good starting point. Also notice how the values go to zero @ 78% throttle. That means when you are cranking the car during starting and you have the throttle @ 78% or more there will be no fuel being injected. Good luck with the tuning.
Joseph Davis: There is no functional difference between v1 and v2. There was a processor swap to get CAN and USB, but its the same hardware through and through. So's the code on the background - same glitchy sync strategy, and IAT compensation is still broken.
Frank, that is a dummy table that turns up/down raw crank fuel (expressed in usec in another table) based on TPS. Typically set up to flood clear at WOT, you can hammer on the closed throttle end of the table instead of actual inj time to fiddle crank fuel.
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We just got some colder temps last night. Colder temps here in Santa Barbara imply 50 degrees...so not all that cold obviously. Car cranked longer then the previous morning at 60 degrees so I inched my Crank Injector Time Table values up to 55 and it lit right off. In colder temps I could see needing even more fuel then my current value can provide.
latest cold start values. just tested it with ~55F coolent and IAT temp. cranks right up especially with a little crack on the throttle!!! thanks for all the help everybody.
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If you have to crack the throttle to get it to fire over then you most likely have too much crank fuel. You should not have to touch the throttle to start any fuel injected car. If you try less fuel and still are having this problem you still have a few other things you can try but you should be able to get there with just changing the crank fuel.
Dave
I believe the AEM ECU needs to see the crank sensor twice before crank sync but this is going from memory and it has been a long weekend at the track I may not be thinking to clearly. So depending on where the engine stopped it will take at least one full rotation plus to see the crank pulse again. I think the reason the OEM ECU lights off so fast is it uses the cam sensors as well as the crank sensor to sync so it has two only see each sensor then it fires.
Dave
I forgot to update this. The NSX has since sold (in late 2012) between my good friend and his business partner so it is still with in the family. I had the car for many months while I continued to tweak the cold start and it was working very well by summer time. I just wanted to thank everybody for the help and tips. 
Cheers.
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