I've been meaning to write a guide of how I setup my fuel tables when I first start the car. A lot of information I found over the internet which worked well for me. Many will disagree on using "base" numbers. But in my opinion it is much easier to get a car started using ball park figure that will get you 80% there. Fine tuning will be much easier once the car runs.
The first thing I do is set up my Lambda table:
Lambda=1 at P/T is good for emissions and makes tuning easier. Lambda=0.8 will provide the necessary cooling once in boost.
Then I setup my VE table to look like this:
You can use the built in VE table builder. But since it is so inaccurate as it largely depends on the injectors I just build it from scratch.
Coolant bins need to be setup as follows for most installations:
I found that the following warmup enrichment settings work surprisingly well. I haven't had to tweak these yet. Colder fuel has more difficulty vaporizing, so more fuel needs to be injected to compensate.
Acceleration enrichments and cranking PW depend on the req_fuel parameter. So it is best to give an example. My engine has req_fuel of 5.1ms.
For cranking, I found that 50% of req_fuel for warm engine and 150% of req_fuel cold engine always gets the engine started:
These values are actually from a running car. As you can see, the base numbers are very close to the final cranking parameters. IC engines have a relatively narrow window of operation as far as AFRs are concerned. You don't want to be too lean or too rich. But richer is always easier, and smoother. Tuning cranking PWs is easy. First warm the car up and tune the warm parameter, then tune the cold parameter with engine cold.
I usually don't bother with priming the fuel injectors. Priming is unnecessary and just wastes fuel.
Acceleration enrichment is usually turned off during the tuning stage. Unfortunately if you do not have access to a dyno, the car will be undrivable with AE off. Use the following base numbers:
dV %ofReq_fuel
2 0%
5 10%
10 20%
40 40%
To accurately inject the proper amount of fuel the ECU needs to have an accurate model of the fuel injector. Unfortunately, VEMs carried over a linear battery voltage correction model over from MS. Here is approximately how VEMS deals with battery correction and how other ECU.
Batt_fac is the main variable the determines how much the injector opening time varies with battery voltage. This value must be determined empirically. It is easiest to tune this variable at idle by increasing the battery load and watching the AFR.
Image coming soon...
Ideally you would send send injectors in to a vendor and the vendor would test them and provide you with calibrations. It seems that VEMS does not have provisions for this. This makes tuning fuel more difficult than it should be.
