Tuning Help

[macka'sxr6t]

Hi Guy's,

I've started to dable a little bit with building my own fuel and ignition maps for one of my projects in the shed.

What I would like to understand more about is Loud Points.

What is it that they actually do?

I believe I have a fair idea, but many forum members might not. So a clear explaination about them would be good.

From most fuel maps, that I have seen they seem to be at every 500 rpm.

Why?

To work out how much fuel is required I assume that the kpa pressure is another Load Point. and the O2 reading from the O2 sensor tell the ECU how long it is required to fire the injector to acheive it A/F target

The tuning tool that I have allows me to add more load points up to 40 or every 200rpm on an engine that will rev to 8000rpm and up to 21 or every 14 kpa vacum/boost pressure.

Is there any advantage if I, for example chose to have load points every 250 rpm and every 15 kpa pressure?

Would there be any advantage in doing this over load points @ 500 rpm & 25 kpa?

What would be the down side if any of having closer load points?

macka

[macka'sxr6t]

43 veiws on this topic and not one reply surely someone that knows how to tune could answer some of my questions

macka

[rboksic]

  macka said:

43 veiws on this topic and not one reply  surely someone that knows how to tune could answer some of my questions

macka

Macka,

I have talked to the guy from EMS ,

load point every 25 or 50 rpm ( 1 or the other ) if you want.

the more load points the finner state of tune you will achieve eg

lets say you have a dip in power/AFR's/torque at 2500 and 2700 you can do 8 load points to fix the dip if required.

So move the better .

Rob

[Robit28]

I will give you a quick overview.

A load point is a point on the map that relates to a matrix of fuel or ignition and cross references that with a load, throttle position or map. For example, at 2500rpm at 65% throttle your injectors are required to pulse at a certain rate per second to allow for correct AFR. The more points you have the smoother the curve will be.

Having said this, most load maps will 'interpolate'. This means that say you have load points every 500rpm then your ECU will average the points in between. This is like plotting a line on a graph and picking the points in between the actual figures you have.

I hope this kind of explains it a little better. I guess the reason people haven't replied is that this topic can get very in depth and would be difficult to explain.

Let me know if you have any specific questions.

Rob.

[bcl]

My Sti runs a Power FC with 400 map points for both fuel and ignition.

400 map points, with 20 points for rpm, and 20 for load.

That is more than sufficient to set up a good tune.

Most of the piggy backs run lot less than this.

I just opened up the old XEDE map than I was using in the 360rwkw tune 18 months ago.

That had 16 rpm points up to 6000 rpm, and 12 load points.

Load points for boost (as%) at 10,20,35,40,45,50,55,60,65,70, 80 & 100.

Brian

[macka'sxr6t]

Thanks for the replies guy's I was hoping to start a topic that both be in depth and informative.

Hopefully this will take some of the so called black art of tuning out.

Some of the info I've come across state that generally you should'nt run anymore than 24 degress maximum advance timing on multi valve engines.

Is this true? or does the max advance you can run have other variables.

Rob I'll certainly take you up on your offer the more info I can get the more confident I'll be.

The engine that I'll be having ago at tuning myself is a Nissan CA18DET.

cheers

macka

[blueboost]

how I use the exede, is I have the least number of load setting as I can get away with, the more consistent the car your tunning the less load points you should need. then if I have a lean spot , or rich, or detination in an area, I create a load point there, but if it is all smooth, I keep the least points, that way it is quick to adjust, but you would have to have atleast ten to start with I would say, so that you have 1 load point for each 10% throttle.

PS remember I am someone just playing like you.

David

[macka'sxr6t]

  macka said:

Some of the info I've come across state that generally you should'nt run anymore than 24 degress maximum advance timing on multi valve forced induction engines. 

Is this true? or does the max advance you can run have other variables.

macka

<{POST_SNAPBACK}>

Can anyone answer this

macka

[Jim]

  macka said:

Some of the info I've come across state that generally you should'nt run anymore than 24 degress maximum advance timing on multi valve forced induction engines. 

Is this true? or does the max advance you can run have other variables.

macka

<{POST_SNAPBACK}>

Ignition timing depends on a whole lot of things. The maximum amount depends on your engine and the conditions it is operating under.

Ideally for maximum performance you should always run the engine at 'Maximum Brake Torque' (MTB) timing. This also gives you the best fuel economy when you are cruising along not on boost and on the Turbo can easily be around 45° BTDC (again varying depending on the engine speed and load). However you cannot get the engine to run at MBT all the time because sometimes the borderline detonation limit timing (BDL) is lower than the MBT timing. BDL timing is that spark advance that gives you the onset of detonation.

(BTDC = before top dead centre)

So running away from MBT timing (either more or less advance) loses you power.

***Very Important*** If you are at MBT timing, more spark advance will lose you power!

MBT timing is essentially the same for a certain speed and load (eg if at 2000 rpm and 4 psi boost your MBT it 15° BTDC then it will pretty much always be 15° BTDC under those conditions). BDL varies depending on the intake and engine temperature as well as the fuel you are running. So taking our example again, at an intake temperature of 50°C the BDL timing at 2000 rpm/4 psi may be 5° BTDC. So you could only run the engine at 5° BTDC otherwise you would get detonation. If you cooled down the intake to say 20°C with a more efficient intercooler, then the BDL timing may move to 10° BTDC, and you could gain some power as the engine would be running closer to MBT. Similarly, if you put in a higher octane fuel, the MBT timing again would be very similar, but the BDL timing would be higher and you could run nearer or even at MBT timing.

Sorry for the Spark Timing 101, but someone might find it interesting.

Jim

[macka'sxr6t]

Thanks Jim,

Sounds like the trick is to find MTB timing through the entire RPM range. Am I right to assume that as the rpm increases the MTB timing advance would decrease.

Appreciate you imput, Jim

thanks

macka