The Basics of Mapping.
Turbo Mini Forums

Since Im learning all over again with the Fuel Injection system (and its quite a steep learning curve), can somebody please explain the basics of mapping?
I understand there is no real crash course and its a fairly wide ranginig topic but hopefully somebody can show me where to start and what to look out for.

Im happy that I finally have the ECU set up correctley, thats, correct static timing, which is set and verified by the strobe light to be 8 deg BTDC.

Now there are a few things that are happening, which I think are related to the base maps, and as a result I would like to change them, but since I dont know where to begin or what changes to look out for (and I dont want to start messing with something I dont know as my lovely new engine will go boom), Im asking here.

Heres a few Questions I have.

The car backfires when it starts, Is this a Ignition issue? Im presuming it is as it hasnt done it before.

The car misfires and spits back out through the throttle bodies when I put it under load at take off, or if Im pushing just past about 15% throttle. It then clears up around 40% throttle. whats causing this?

Injection timing, how do I know when to time the injection sequence for a 286 cam? the maps in the ECU are for a 266.

Injection, Do these work linear? for exmple my injectors are quite large, 500cc/min I think , can I work out using the size of injectors the Base map was designed for, how much to reduce the opening time on my injectors?

I understand to get the car spot on I need it on a Rolling Road, which is exactley where its is going as soon as I get paid, but I just was to be able to tinker with it until then to get rid of the misfires and generally understand whats going on.

A pop back trough the throttle body is lean burn back fire,

The back fire on starting sounds like you might have two much fuel on cranking.

I'm sure some of the more knowledgeable folks will clear the rest for you CIaran,

P.s. Why don't you save the map you have on a key fob and then you can mess away with tuning and have no fear of doing damage

cheers paul, Ill do that tomorrow, explainations cleared alot up!

Schrödinger's cat - so which one am I ???

Great advice, I richened the mixture on acceleration and reduced the amount of fuel injected on the priming pulse and after start enrichment. I dont think Its quite there yet but the engine has gotten much more rev happy and its reaching the limiter very quick ( Ive it limited to 4K RPM)

I assume you have a lambda sensor wired in somewhere? Have you had a look at the readings whilst the engine is running? This can give you some insight into what is happening (it can also show you some red herrings).

What ECu are you running? I know my ecu takes into consideration, injector size/ engine size to give you a required fuel setting.

Back fire on over run could be lean backfire (if running wasted sark), overfuelling, cam timing, ignintion timing.

The lambda gauge will be your best friend in the early stages of maping.

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1/4mile in 13.2sec @ 111 terminal on 15psi

Backfire in the exhaust on over run is a rich condition. The lowest lines on the map in over run areas are just as important. You may have an over run fuel cut setting which makes this area of the map much easier to tune, since you can ignore everything in the area where fuel cut is active, leaving the low rpm area for manual tuning.

I'd be tempted to put a line at the very bottom of the map and have that set for 0kpa and all the VE values zero, with the next line up 20 or 30kpa as normally tuned. This will reduce proportionally the fuel to zero as the MAP drops below 20kpa. while it might not be perfect, it will be far better than the lowest line of 20kpa and ve values, since if over run MAP is lower than 20kpa, it will overfuel.