couple of questions about fuel pressure TB's IAC and more

[stevieturbo]

Regardless of FPR, you should always size the injectors to suit your power requirements.

Your fuel rails will have no problems.

As already said more than once, the engine will be mapped to meet its fuelling requirements. You could run static pressure, or more common with vac pipe connected. Makes no real difference.

Decide your ultimate power goal, and size the injectors for approx 80% duty cycle at that power level.
Emissions with small injectors will be no problem. The camshaft will be more of an issue. Just depends what criteria you have to meet ( ie cats or no cats )

[DaveEFI]

I'm not an expert, but the consensus on the MS forum is although you can tune round most things it's better to start off with a normal reg delivering the actual pressure you use in the initial calcs. Why give yourself more problems - there will likely be enough anyway.

[stevieturbo]

Again, the ecu doesnt know, or care about fuel pressure, at least the majority dont, there may be some oddball ones that might care ?? Ive never come across one that requires fuel pressure to be input to the ecu for any of its calcs. The only thing that would throw things off, is if fuel pressure was not consistent.

Even though its rising rate, it is still consistent in what it does.

[DaveEFI]

Again, the ecu doesnt know, or care about fuel pressure, at least the majority dont, there may be some oddball ones that might care ?? Ive never come across one that requires fuel pressure to be input to the ecu for any of its calcs. The only thing that would throw things off, is if fuel pressure was not consistent.

Even though its rising rate, it is still consistent in what it does.

Don't you need to know the injector flow rate for initial calcs? And that is dependant on fuel pressure.

[stevieturbo]

Again, the ecu doesnt know, or care about fuel pressure, at least the majority dont, there may be some oddball ones that might care ?? Ive never come across one that requires fuel pressure to be input to the ecu for any of its calcs. The only thing that would throw things off, is if fuel pressure was not consistent.

Even though its rising rate, it is still consistent in what it does.

Don't you need to know the injector flow rate for initial calcs? And that is dependant on fuel pressure.

Nope.

Many systems operate where you simply input injector pulsewidth into the map. You can scale this up or down as required.

Motec uses a different system where the map is just numbers. larger is more fuel, smaller is less.
There are 2 scaling factors that you adjust to gain more resolution, or if the numbers just get too silly. But again these are just numbers. increase or decrease as required so the map numbers are within a sensible range. So whilst they obviously do relate to actual pulsewidth, they arent displayed that way on the main fuel map.

ie, you can maintain numbers in the range say 0-100 if you like. Or scale up if they ended up using only 0-40 for example, or down if they ended up 0-200
One excellent feature with the motec. Any time you make changes to that figure, or even the range of load sites on the map itself. Motec automatically re-calibrates the entire map to suit.
I havent seen too many others that do that.

Ultimately it really doesnt matter though. bigger number is more fuel, smaller is less.

Ive even seem some people tune on the graph display taking no reference whatsoever to the numbers involved.
The engine simply doesnt care what the numbers are. It just cares that it needs more fuel, or less at any particular load site.

The only reason an ecu could require to know actual fuel flow. Is for calculating fuel used...ie miles per gallon etc. Other than that it is totally unimportant