boredracer408

Are you supposed to tune your car to try and get the most perfect a/f ratio throughout the RPM band?

Or are you supposed to tune with some rpms richer and leaner than others?

Im confused...

Mase

its not really rpms based, its more load based(meaning boost or vacuum)...

typically, at cruising speeds, you'll want 14.7-15.5 or so, slight vac, you'll want 14.0 or so, then in boost, you'll want to work your way down to 12:1 at full boost.

TraKtioN

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">its not really rpms based, its more load based(meaning boost or vacuum)...

typically, at cruising speeds, you'll want 14.7-15.5 or so, slight vac, you'll want 14.0 or so, then in boost, you'll want to work your way down to 12:1 at full boost.</TD></TR></TABLE>

I dont understand how A/F ratio has to do with load of the engine, because it doesnt change the mechanics of the engine?

fulldragcrx

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TraKtioN &raquo;</TD></TR><TR><TD CLASS="quote">

I dont understand how A/F ratio has to do with load of the engine, because it doesnt change the mechanics of the engine?</TD></TR></TABLE>
try to start your car with a " almost dead battery". it might crank a couple of times but it aint gonna start. as load on the battery increases so should its ( the battery) output amps aka cold cranking amps. an engine works the same way on a dyno you can see an engine make 2 totally different HP numbers at the same RPM point just cause its under a load. This is why tuning is very important.

IMPATIENT

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TraKtioN &raquo;</TD></TR><TR><TD CLASS="quote">

I dont understand how A/F ratio has to do with load of the engine, because it doesnt change the mechanics of the engine?</TD></TR></TABLE>

yes it does......try towing something and then youll understad what LOAD has to do with engine performance.......

boredracer408

more info please,

How can you tune under different load? Are dyno rollers adjustable or something?

Mase

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boredracer408 &raquo;</TD></TR><TR><TD CLASS="quote">more info please,

How can you tune under different load? Are dyno rollers adjustable or something?</TD></TR></TABLE>

ok, take all thoughts of a dyno out of the equation...

now take a look at this chart:



This is a screen shot of hondata's software.
Basically you have 3 axis. RPMs vs Load (pressure either vacuum or boost) vs Fuel Increments.

thats how you can tune vs different loads, hope that helps

Charbon Sty

is there some calculation on what you should be looking for?

TraKtioN

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IMPATIENT &raquo;</TD></TR><TR><TD CLASS="quote">

yes it does......try towing something and then youll understad what LOAD has to do with engine performance.......</TD></TR></TABLE>

ya I know what it does to the engine...theres a resistance against the motor but that doesnt change the mechanics of the engine itself, same amount of air going in, same amount of fuel, same compression, same everything. From my standpoint all I see is resistance fighting against the speed of the engine. Can someone give me a more technical answer?

Chillinit

Mase..can u explain those charts in further detail....what does the top colum represent(x axis)....and forthe psi(y axiz)..are the increments multiplied by 100??? 500 psi to start? I want to learn more about this...please help...

VTC_CiViC

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chillinit &raquo;</TD></TR><TR><TD CLASS="quote">Mase..can u explain those charts in further detail....what does the top colum represent(x axis)....and forthe psi(y axiz)..are the increments multiplied by 100??? 500 psi to start? I want to learn more about this...please help...</TD></TR></TABLE>

Top column = manifold pressure/vacuum. Mbar (millibar) is the scale Hondata uses to measure vacuum, positive pressure is read in psi. Notice all the way to the right where it goes from vacuum to .5psi, the lower column is the boost column (psi).

Y-axis is engine rpm.

Nfurno

Can you go into more detail on what we are looking at? I really would like to understand what theses graphs mean.
TIA

VTC_CiViC

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nfurno &raquo;</TD></TR><TR><TD CLASS="quote">Can you go into more detail on what we are looking at? I really would like to understand what theses graphs mean.
TIA</TD></TR></TABLE>

Like Mase said, those are Hondata screen shots of somebody's map. I was just answering that other guys question about the x/y axis.

Mase

here guys, take a look at this aem ems screen shot, you might be able to understand this better, but please dont hesitate to ask questions, thats what were here for

kpt4321

Load is simply how much "work" the engine is doing, or being asked to do. The bst way to represent this is in manifold pressure, although it is sometimes shown other ways.

As load increases, cylinder pressure increases, which necessitates the use of more fuel so that you have a safe mixture that doesn't make **** go boom.

As Mase said, A/F ratio is primarily based on load, which means that generally it's much less dependant on RPM. However, manifold pressure is not a perfect representation of load either, so A/F ratio shouldn't be kept exactly constant.

The best representation of load I can think of is cylinder pressure. Mase, any better ideas?

If you set up a sensor for that and used maps based on it instead of manifold pressure, tuning would be even simpler.

kpt4321

Since Mase is posting it up like a champ, he might beat me to this, but oh well.

The way fuel mapping works, it it's like a spreadsheet. The ECU finds the rpm (from a sensor) and uses a few sensors (map, temp, etc) and some math to find the mass airflow. Using the mass airflow, it can find out how much fuel, or how long of a pulsewidth, would be necessary for XX A/F ratio. If changes the XX air to fuel ratio, depending on what the maps tell it to do. But, say the boost is 5 psi, and rpm is 4000, it goes to the 4000 rpm column, the 5 psi rom, and in the box it can find the right A/F ratio.

Some systems display the target A/F ratio, some display arbitrary fuel numbers, some display enrichment percentages.... In the end though, they all do the same thing.

Mase

did a nice job explaining no need to comment yet

boredracer408

im still way confused. Looks like i got some homework to do about tuning.


BTW, how do you tune different loads on a dyno?

ndogg

this might help clarify:

lets say that the map was only 2 dimension, rpm and fuel. do you think your motor need the same amount of fuel when you are cruising on the freeway at 3500 rpm with almost no throttle VS. when you are passing 3500 rpm in a full throttle pull? NO! so there needs to be something else to determine how much LOAD in on the engine... manifold absolute pressure is a good way to determine this.

does that help?

ndogg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boredracer408 &raquo;</TD></TR><TR><TD CLASS="quote">BTW, how do you tune different loads on a dyno?</TD></TR></TABLE>

most people don't. they only tune for full throttle passes when using a dyno. to tune different loads, people usually do street tuning. there are different ways to do this... i have never done any of them so i can't be more specific. there is some good tuning info on hondata.com though.

kpt4321

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boredracer408 &raquo;</TD></TR><TR><TD CLASS="quote">im still way confused. Looks like i got some homework to do about tuning.</TD></TR></TABLE>


If you ask a specific question, we can answer it. Broad "how does it work" questions are VERY difficult to give a good response to.

VTC_CiViC

Mase, kpt.. talk to me about timing.

What do you use to determine a good amount of advance for idle/low load crusing/WOT?

I'm basically using some base maps and I only adit timing for the boost columns (.65 rt. per psi), but the vacuum portions of the map are non quite as clearly define in terms of what to look for in timing.

Chillinit

ok...after looking at the screen for about an hour..I think I'm beginning to understand what is going on here.

Questions:
1. what is the fuel measured in? on the table
2. Mase highlighted a section on the aem map....what do those represent? optimal air/fuel ratio?
3. kpt4321....I like ur thought of cylinder pressure being more accurate....make total sense..but how would u measure that....ie..there are no sensors...please correct me if I'm wrong.

Thks for the info guys....great stuff

ladysman

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mase &raquo;</TD></TR><TR><TD CLASS="quote">

ok, take all thoughts of a dyno out of the equation...

now take a look at this chart:



This is a screen shot of hondata's software.
Basically you have 3 axis. RPMs vs Load (pressure either vacuum or boost) vs Fuel Increments.

thats how you can tune vs different loads, hope that helps</TD></TR></TABLE>

Mase, curious to see what your timing in boost looks like in those maps. Can you post?
What motor is this for? (Sorry, didn't look at the whole thread).

Mase

that map is a stock GSR map, my timing maps differ for each motor (different compression, bore size, IC, etc) but general, i take out .75 degrees of timing per psi of boost