Can't take it anymore! Help with startup

[jrd]

Hi all,

 

My 240Z is driving me nuts, but I won't waste your time venting on all the things that are going wrong, but let me concentrate on one first....my inability to start the car without putting the pedal to the floor. I am running Megasquirt fuel only (thankfully) and here is what happens...

 

If you don't touch the pedal at all and try and start the car it floods badly. I have set the TPS value for flood clear to 200. So the only way to start it is to put the pedal to the floor and crank. When it does finally fire up a cloud of unburnt fuel comes out of the tail pipe....this reallly, really sucks when I try and valet park - the guys always flood the car and then come looking for me. I couldn't even get the thing through a car wash this week. It is idling badly after start-up as well....and I occasionally get a backfire through the airfilter if I step on it too soon after startup...

 

Here are my cranking settings

Prime pump when : Prime pulse >0^

Fire priming pulse: after 2 sec

Priming PW source: standard prime

Standard Priming PW (ms): 0.0

Cranking Pulse WIdth temsp: CLT only

 

OK, why the heck is this thing flooding - I am not even using a priming pulse???? And why am I getting a lean backfire when cold? Specially after the stupid thing just flooded???

 

ARRRGGGGGG.

 

Couple of other settings

Cold Accel enrichment is 8.0

COld accel multiplier is 140%

 

I swear if I can't get this thing running right soon it is back to SUs for me!!!!! I have had it! The ironic thing is that I am supposed to be writing an article for Nissan Sport Magazine about the conversion and right now it is a very short article - "Don't do it!!!!"

 

Thanks for any help, sorry for the vent

 

Joe

[mobythevan]

You should not be messing with the gas pedal at all just to get the car started. You have three things to mess with to get it to start and idle.

 

Fuel (either adjust VE table at idle or adjust required fuel)

TB butterfly (adjust with idle screw)

Ignition Timing (check during cranking with injectors unplugged)

 

You need airflow to start and idle, so open up the butterfly with the idle screw. Go ahead and open it a bunch you can always adjust idle back down when it starts.

 

Now are you still flooding? Then take away fuel during cranking/idle area of VE.

 

It is very common for the engine to run lean after it starts up because it is cold and needs warmup enrichment. You need to adjust that to fix your lean problem and you need to adjust the TB butterfly to fix your flooding startup.

 

Those are two of the most basic tuning issues and are covered in the tuning manual. If you had a wideband on the car you would be able to see how it is leaning out after it starts.

 

 

I swear if I can't get this thing running right soon it is back to SUs for me!!!!! I have had it! The ironic thing is that I am supposed to be writing an article for Nissan Sport Magazine about the conversion and right now it is a very short article - "Don't do it!!!!"

 

I think you should add to the article: "Don't do it, its too hard"

[mpcapps]

What are your cranking pulse widths, both at -40 and 170? those are the main parameters i tweaked to get the car to start. yours might be set Way too high.

 

The priming pulse is not meant to deliver the fuel for starting, only to get the air out of the end of the injectors. I wouldn't set it at zero; in the manual a few parameters are said not to set to zero because they'll will yield unpredictable results. i'd set it to 2.0 like the manual suggests.

 

as far as the lean backfire on cold accel, you may not have enough warmup enrichment set, or enough normal accel enrichment set. during cold accel, the fuel delivered depends on all these factors: req_fuel, ve table, warmup enrich, accel enrich, cold accel enrich, cold accel multiplier.

 

the manual suggests tuning startup first, then the ve table and warmup, accel later.

[olie05]

I read the same thing in the megamanual and decided to set my prime pulswidth to .1, standard prime on power up, and the cranking pulsewidth at 80 degrees is 4.6ms.

 

This gets my car started with very slight push on the throttle, and it will idle from a cold start after that.

 

I would start by checking cranking pulswidths, and moving on to the ve table from there.

 

What code ya running? what's your set up?

[mobythevan]

This gets my car started with very slight push on the throttle, and it will idle from a cold start after that.

 

I guess whatever works for everybody, but ASE is what should be tuned to get the car to idle after cold starts. Then you don't have to push the pedal to start it. I can't say much because I have never tuned ASE on my talon so it does the old start and die routine.

[jrd]

HI everyone, thanks for all of your suggestions. THe main problem with start has been the idle adjustment on the throttle body - I had it set too low. I opened it up and now it will start with a slight decrease of the pedal. My fast idle bypass doesn't seem to be working so I am going

to look into that before upping the idle anymore.

 

After I get it idling properly I will post some VE tables and accel constants and see if I can fix the lean back fire and the surging on mild acceleration.....

 

 

Thanks all,

 

Joe

 

 

[WizardBlack]

HI everyone, thanks for all of your suggestions. THe main problem with start has been the idle adjustment on the throttle body - I had it set too low. I opened it up and now it will start with a slight decrease of the pedal. My fast idle bypass doesn't seem to be working so I am going

to look into that before upping the idle anymore.

 

After I get it idling properly I will post some VE tables and accel constants and see if I can fix the lean back fire and the surging on mild acceleration.....

 

 

Thanks all,

 

Joe

 

 

 

Are you trying to tune this without a wideband? I would think you could solve a lot with a wideband hooked directly to battery power and tune it as it warms up. A Few iterations of that should get your pretty darn close. Cars like it pretty rich when cold; 12:1 or so and tapering to about 13.5:1 until you get within 20 degrees of full temp when closed loop can be turned on. They also need a pretty big initial fuel pulse, but then not a lot when cranking. It sounds like you have too much for the initial pulse or cranking and when running it runs too lean (not enough coolant enrichment) and/or your accel enrichment isn't quite high enough.

[jrd]

Cars like it pretty rich when cold; 12:1 or so and tapering to about 13.5:1 until you get within 20 degrees of full temp when closed loop can be turned on.

 

OK, this is the first time that I have heard about being able to run these closed loop. Is this because I am not running a wideband O2 sensor?

 

Thanks,

 

Joe

[mobythevan]

sure, that is what the target AFR tables are for. Run closed loop with wideband once you are warmed up enough.

[X64v]

This gets my car started with very slight push on the throttle, and it will idle from a cold start after that.

 

I'm in the same boat as olie. It starts with just a slight push of the throttle, hot or cold, and idles just fine cold, but I cannot get it to start without touching the throttle, hot or cold.

[jrd]

That is where I am as well....slight push of the throttle. I am much happier though! Now I need to address the surging problem that I am having. I will probably post the tables and settings to try and address that one.

 

Joe

[twoeightythreez]

My experience with it was to get you engine to operating temperature. Now, starting the lowest cranking pulse value, adjust it until the engine won't start, then go about .2ms above that.

ASE is only to keep the engine running after starting, but you have to set that when the engine is at operating temp also. The ASE will automatically tailor itself according to engine temp so you want to set that when it's warm.

Once you get all those set you can then do a baseline for cold start, about 4x your warm value (remember you want the car to just kick over when it's hot with the cranking enrichment, the ASE will keep it running.)

After that , it's a matter of tuning it over several cold starts, just like you used to do with automatic choke rods back in the day. (MS really is just as simple, people just nuke it apparently) The only difference is instead of bending a rod and starting it you enter some keystrokes and start it.....

Btw..you can also run closed loop with a narrow band sensor, it'll keep it near stoich during cruise conditions, just like the 90's factory EFI cars.