Doesn't run with MAP Hooked up

[Olds442FI]

Here is the problem I am finding so far.  I got the VEMS hooked up (with the fuel pump on its own switch) and tried to start the car for the first time. It started up using the throttle a little, and ran really rich and choppy. I expected this as the timing isnt set and i am not realy sure how to adjust anything quite yet. (i think ill learn faster if the car could run . Anyway, I realized i haven't hooked the vacume line to the internal MAP Sensor so i connected it. After that i cranked it over once again and it started for a split second, ten shut off. I tried agian, paying attention to my megatune gauges and noticed that the pulse width gauge drops to zero the second it starts now. I then pulled the vacume line from the ECU again and tried once more. I again was able to keep it running by peddling it but it was still very rich. I am even able to get some decent rev out of it but it runs a little or actually alot crappy. Im not quite certain how to calibrate the Map sensor and i assume this may be part of the problem. Could anyone provide some insight? Mind you i am not up to par with alot of the termonology so it is certainly  prefered if things were explained to me as if i knew nothing. I can build an engine but programming one is a whole new ball field for me. I am Keeping things as simple as possible, I use an Edelbrock Pro Flo on a naturally asperated Chevy 350, with a single cam trigger and single coil. Its a basic FI setup with a Mallory Hall effect distributor. I am using firmware version 1.0.73. at least thats what it says at he top of my magatune.

[rob@vems.co.uk]

The vacuum is pulling the ecu into a different part of the fuel map.
You shouldnt be putting fuel into the engine until the timing is 100% spot on.
Set your cranking advance to 10degrees or 0 and use your timing light to see where the thing is actually firing.
Adjust the TDC before trigger value to set the timing correctly, then setup your timing map - you should be able to simulate a known good timing map for the Chevy 350 - last time I looked at the MSD catalog it showed the timing curves.

Then you need to start tuning the fuel, once the fuel is done go back to the ignition map and improve that.

You are trying to rush a complicated proceedure, take your time and you will have a better experience and results.

[Olds442FI]

Im not so much rushing, Just reverting to what i do know. In my old carburetor state of mind, Crank it over and twist the distributor until it runs . I always knew what the fuel was at. Anyway, to save me some time, how does one go about mapping the ignition curve? The only timing adjustment i have seen was in the advance in degrees at crank. i have a good idea of the timing curve i need but i dont know how to input into the VEMS. Anyway, ill go ahead disconnect my injector fuse and get my timing in place for now. Thanks, at least i know where to start now

[Olds442FI]

one other question, Should my trigger be considered rising or falling? Mine is currently set to rising. How do i know which setting to use?

[rob@vems.co.uk]

There is an ignition table along with the VE and lambda tables.
If it runs with rising, stick with it, its for hall triggers anyway.

Now we're running with .25 degree accuracy in ignition and 0.1 accuracy with lambda things are a little more refined than the traditional twist and crank methods.  You need to calibrate everything (voltage, temperature sensors, TPS etc, spark position) to as close to spot on as you can get it, in order to start from a decent baseline.

[Olds442FI]

Alright, this table makes some sense to me. I am assuming that i should correct the RPM range across the bottom of the table so that it maxes out at about 7500 RPM instead of 10000 right? I chose this because in the most extreme case i would rev it to 7000RPM and leave a little extra on the table? I figure The kPa side of the table is Vacume from the map. The more it drops the more load on the engine. WOT being the lowest at 20kPa. So assuming that set my distributor so i read 0degrees at he timing mark. I would want that top left box at highest kPa and Lowest rpm to be my baseline spark advance at idle and the max Spark advance at the exact opposite corner of the table. Now do i have to go over every value in each box individually or is there a super special secret to this. for example, if i correct the idle and WOT at max rpm will the rest of the table follow my lead?

Secondly, Adjusting the map sensor is a little foggy to me as well. I took a crack at it last night but went home scratching my head. I am using the internal sensor. Now the user guide says to check my local weather to get current air pressure. I have 250 as the range but it says to adjust my offset until my map reading reflects the current air pressure(i am assuming that i base this off reading from the MAP gauge in the main megatune screen).  the part that confuses me a bit are the values used in the user guide. it says Consult your local weather for the current air pressure, this tends to range from 995 to 1028 or there abouts. Adjust the Map sensor offset value until the MAP reading reflects the current air pressure (typically between 99kpa and 103kpa). I figure the 995 to 1028 is in millibars? do i have to calculate my current air pressure from Mb to kPa? the funny thing is now that i typed it, this seems like a silly question. if i am spot on with that, don't try to explain it further and re-confuse me again.

[gunni]

No the Kpa scale is an absolute scale.

100kpa = atmospheric or so.
20kpa = maximum vacuum

99kpa = 99000pa = 990mbar

So if you know your atmospheric pressure is 1013mbar then that is 101.3kpa

[Olds442FI]

gotcha, i was thinking in reverse. that's actually what i meant but had it in my mind that that the line for my MAP sensor was below the throttle plate hence my reverse thinking on the pressure reading. still wondering though. do i have to change every figure on that table or is there and easier way?

[gunni]

It´s not that many takes less then a minute to do.

[Olds442FI]

hmmmm, sorry for the multiple posts as i get my thoughts. I decided last night to save my current settings and see if i can figure out a way to look at the when im not near the car and i just did! Yay Me! Anyway, it looks like the settings that i have are not all that bad. I know Jason the VEMS guy here in the states configured this ECU for the previous owner. The previous owner also had a Chevy small block with with about 50 more CI but was a boosted engine. It looks like he configured a decent base line already..the Only area i would like to really change is the front half around idle. Its currently set at 4 degrees and i would probably want about 10 degrees at idle, maybe 12. the rest of the power band seems notsobad. this leads me to two more questions. What is VE and Lamda. I am assuming that if my spark table is somewhat configured this will also be somewhat close. I'd probably understand it better if i knew what they were. As far as configuring all the sensors, i think i can figure that out on my own.and now i think i have a better understanding on configuring the MAP sensor as well. once again, i would like to thank you all for the assist. I can feel the knowledge growing, but i still have a long way to go.

[rob@vems.co.uk]

VE is the volumetric efficiency of the engine.  The lambda table is the target fuelling for the engine typically 1 for idle and part throttle (for emissions and economy) and 0.9 to 0.85 for WOT maximum power and torque...

The tables are used in conjunction with each other - the VE is designed to model the fuel requirements for the engine, and the Lambda scales the fuel for the target fuelling.
Have a look here.
http://195.159.109.134/vemsuk/forum/index.php/topic,351.msg3474.html#msg3474


From http://195.159.109.134/vemsuk/forum/index.php/topic,97.0.html

So now we have managed to cram the greatest amount of air into the cylinders, we need it to go bang. Combustion comes by mixing oxygen (air) and fuel with each other, and then igniting the mixture. You can achieve combustion under a wide range of conditions, but the best combustion will occur when you have a well mixed quantity at the correct ratio of fuel and air. As we will see later in the fuelling section, the definition of best can vary depending on other requirements (power, economy, engine life). This mixture ratio is known as the Air Fuel Ratio (AFR). The condition when all the fuel and all the oxygen are consumed during combustion is called the stoichiometric AFR, and is around 14.7 parts of air to 1 part fuel for a gasoline engine. Note that we measure the parts in units of mass. To normalise this AFR we can convert it to a value called Lambda. This is simply the current AFR / stoichiometric AFR – so at stoic, we are at 14.7:1, which is Lambda = 1.