Start fuel map help

[DiscoPotatoes]

Hi all,
I am having a bit of bother with getting the car to start cleanly from cold
It's a bit hit and miss and I sometimes have to dab the throttle.
I have gone through loads of plugs due to flooding them ( i have reduced the fuel and it seem to crank for longer with out catching) set it back to where it would fire up, around 300% at 0 deg and now I can't get it to catch at all.
I will be replacing the plugs again but can someone explain what sort of % I should be aiming for from 0 deg onward, and why the map won't allow negative numbers in the columns? Ie -5 degs?
As I understand it these % are added to column 1 row 1 of the main fuel map and I should have the start pulse set as low as poss( I have it on 1).
It's a 4.8 twin turbo, 7.5:1 compression, 650cc injectors, fuel map cell 1 is set at 4.7 ms.
Should also add its a rover v8 and a p8 pro
I hope my rant makes sense to someone
Cheers

[stevieturbo]

4.7ms is a HUGE fuel value unless there are some MAP compensations applied ( please tune MAP vs RPM, and not TPS vs RPM with compensations )

I assume you can get the engine to run, and start when warm ? Drop all compensations to zero, with just some cranking enrichment.
Tune fuelling to sensible levels when warm around idle etc, and only then can you wait until it is cold and start adding cold start numbers to increase to assist cold starts.

[Roverdose]

4.7ms and 300% is a lot of fuel on a 650cc injector.

do you have an idle valve? or are you running the ignition idle table?

Drew

[Rob Stevens]

4.7ms at idle with pressure compensation sounds about right. You don't get the ignition idle table with the P8, sounds like it might not have an idle valve at all, it will always be hard to start without a little throttle.

post some of the other settings, like firing tooth on start up and are you using water temp compensations or just cranking enrichment?

You need a bomb proof hot idle with around 5 degrees ignition before even looking at cold starting.

Why would you want a -ve timing value, are you trying to run the anti lag 2nd map?

but can someone explain what sort of % I should be aiming for from 0 deg onward, and why the map won't allow negative numbers in the columns? Ie -5 degs?

I don't understand what you are asking here.
The ecu doesn't use the ignition map for cranking, just the firing tooth on start up.

[Roverdose]

my map is iro 2ms at idle with pressure comps. 380cc injectors, 2.5ltr v6 supercharged.

Drew

[stevieturbo]

Mine is around 2ms at idle with 600cc injectors. Even though it displays as 2.6ms or so due to the dead time.

P8 doesnt have this, so I guess 2.6ms would be on the main display, which may then be subject to compensations. Although mine's a 6.3, so I'd expect it to be a little higher than his 4.8
Cant remember back far enough what my RV8/P8 was like

By -ve values, I'm assuming he is referring to no values below 0degC, this is user definable though, so he should be able to enter values for freezing conditions.

And of course dont forget, all engines also need air to start.

[DiscoPotatoes]

Cheers guys!
Got it started in the end but had a few other problems that caused me to second guess myself, I reduced the first cell to 2 ms left the cranking fuel at 300 at 0 degs, which got it started with a bit of fettling It running well albeit a bit rich.
It's going in for mapping next week so ill get it mapped for MAP vs RPM and finally get some numbers at last!
Thanks again for your help

Disco.