Difficult cold starts - What to change?

[petew]

Hi all, having an issue with cold starts. It takes 2-3 separate crankings to get the motor started. It fires each time but falls flat. The last time it sounds as if it's going to die and then the ECU catches it and it idles very low until it reaches about 50degC.

It was running too rich, but I've recently fixed that. However it's still not running right. I've got a log of the start and a file. I'll try and post them.

startupgraph.png

Specs, stockish 1600, small turbo/intercooler, MS3 on Microsquirt, bosch VP commodore injectors on CB manfold ends, Hyundai excel single TB/IAV, 36-1 wheel/gm crank sensor, Golf wasted spark coilpacks. One of Mario's head temp sensors. Beyond this the motor is generally running ok.

P.s. having issues uploading the log and MSQ.

[kangaboy]

What about your WUE and ASE tables? I just started messing with mine this week. At first I was a bit too aggressive with the curve, and it sounded like it was running on two cylinders. I flattened the curve out a bit and now it fires up and idles on the first key turn.

[andy198712]

i was reading this a while back,

if it starts with just the key, no throttle, then your cranking settings are good, if it needs a little throttle then your probably a bit rich on the cranking.

to keep it going without throttle is down the ASE and WUE, i need to tune mine too!

[Piledriver]

Oddly, afterstart and WUE are the hardest bits to tune, as everything is changing so rapidly, and it takes awhile between cold start tuning sessions.

The WUE "wizard" in tunerstudio works, to a point. Cranking and ASE need to be nailed down, first.

To get decent WBO2 readings, the key needs to be left on for at least 1 minute from cold to allow the sensor to heat up to its operational temperature.
Some 14point7.com WBO2 controllers can tell you the heater power and the latest ones can read back sensor temperature..

Depending on the WB, it may need to be temporarily directly battery powered, as some take awhile to produce reliable readings after power cycle.

Of course this is not a good thing for the sensor as a cold engine will spew fuel and liquid water spray around in the exhaust, as the water vapor condenses in the cold exhaust, and hot O2 sensors absolutely do not like water, the water can damage them esp if they get splashed hot.

I have always found that I usually start out with way too much fuel, and that an aircooled engine warms up very quickly.
Its best IME to begining with WUE and ASE flatlined, the defaults are for a SBC and far too much fuel, for too long.

You also need a lot more cranking and idle air with cold oil dragging things down, so some form of idle air is required, or you will have to help it with your foot on the gas pedal like Webers---30 seconds is usually sufficient.

An often misunderstood issue is an O2 sensor cannot "smell" unburned fuel like we can: It reads a rich misfire as dead lean.

[luftvagon]

and WUE, and ASE depend on Fuel table too.. so when your fuel table changes, there goes your nice setting that worked before, and now it doesnt

[Clonebug]

I just messed with my settings last night and I think I got a better warmup.
I completely reworked the % and temperature lines to see what difference it made.......after a "Save As" of course.
Having no IAC does make startup a little different but I can almost start mine with nop throttle input in the summer if I have my warm idle at about 1100 rpm. Having a low idle speed makes cold starts act more like a dual carb cold start.
As Pile says you need a little throttle blipping for about 30 seconds.

[petew]

Had my first go with the new laptop tuning the car last night. I just ran it through it's warmup. A couple of changes...

1. Firstly, I moved the ASE up from about 50% to 74%. Once I did that the car stopped dying just after firing. That happened on the third separate crank though. So there's more to fiddle with.
2. This might be wrong, but then I totally flattened out the ICD around 66%. Once I did that the RPM stopped hunting up and down.

[petew]

Ok, so back in the car tonight to try cold starts. Success! It started and ran first time. I fiddled with the ASE a little, but straight up it was a lot better. I think I can smooth things out still, but it's much improved. Thanks all!

I also got to sort out some other issues I had with programmed outputs. My intercooler pump now comes on when it should instead of just running the whole time.

BTW, in terms of warmed up idle, I'm getting low to mid 13AFRs. Is this right or should I shoot a touch leaner for 14?

[Clonebug]

I've tried a lot of settings at idle and I always come back to 12.8:1 idle afr.

I just went to 14.1:1 Saturday at idle after it was good and warm and now after a cold start it had some lean areas just off idle. Grrrr.....

[Piledriver]

Use the cold timing feature, helps afterstart and warm up idle speed from dropping too low.
ACVWs don't stay cold long.

[petew]

I've tried a lot of settings at idle and I always come back to 12.8:1 idle afr.

I just went to 14.1:1 Saturday at idle after it was good and warm and now after a cold start it had some lean areas just off idle. Grrrr.....

I found it easy to fix the idle AFRs just by messing with the fuel table where it idles.

Fuel table 9.8.16.png

You can see all the cells with 41 in them. They're all the idle area. By dropping them to 40, I got high 13s/low 14s AFRs. I just don't want the motor running too hot at idle.

[Volky]

Hi Petew,

You should revise your table.

I found this a few months back.

Take a look at it, it helps:

http://stinger-performance.proboards.co ... uning-tech

[Piledriver]

Use the idle VE and idle timing features, they work great.

MORE timing at idle will most likely run cooler from what I have seen.
Copying the factory timing at idle will cook the heads, longevity was not remotely VWs priority.

[petew]

Hi Petew,

You should revise your table.

I found this a few months back.

Take a look at it, it helps:

http://stinger-performance.proboards.co ... uning-tech

Thanks Volky, I read the post on WUE. What he describes is pretty much exactly what I did. My ASE taper could do with a look, but I think most of the rest of it is pretty close.

[Piledriver]

The most interesting thing reading that is that Stinger is selling Megasquirt based units now, rather than their own ECUs...
I suppose they are MS2/3 module based with custom carrier boards etc.