BoostedSi

My 780cc delphi are at 68% duty cycle at only 250whp. This keeps my a/f in the 12s. Am I reading the aem pro right?....on the fuel map/view duty cycle my tuner put in 68. Am i right, does that mean 68%duty cycle? because you can type in up to 130 on the charts. Thanks.

btw...if i am correct, could it mean that my fuel pump could be bad?

google

go to the aem site forum thell know

Pelican

((OK I have no dyno/tuning experience))

but that sounds ok to me. 780 is kinda big and it supports kinda big HP, so if its only having to put out ~290hp worth of fuel, then why wouldn't 68% be right?

BoostedSi

780s support up to 450-500whp.

I'm at 68% duty cycle at only 250whp

BlueSi2k

You have the right concept but 68% does seem kind of high. I think 440's hit 100% at around 300hp depending on setup so for 780cc's to hit 68 at only 250 does seem kind of weird. What I want to know is where the ems is calculating the duty cycle numbers from since I dont think it knows the size of your injectors. Try the AEM forum and if you find out post back as I am curious. HTH

Tinker219

Im thinking that fuel delivery might be exponential in respects to HP. Maybe once you hit around 80%d.c. you will be close to the 400 hp mark? How do you know you are at 250hp?

tony1

What is your fuel pressure and is it remaining constant? Don't forget, fuel injectors are usually rated at 45psi or so. If your fuel pressure is falling to 30psi under boost then it'll take alot more injector pulse for the same amount of fuel.

lugnuts

Am i right, does that mean 68%duty cycle? because you can type in up to 130 on the charts. Thanks. >>>

Sounds like what you are referring to is the fuel trim number in the AEM software. Generally speaking, this is just a number. Most engine management systems do this in their own different ways. Some go from 0-200or 0-256,some go from -50 to +50, and if yours does go to 130 then it is impossible for that to be duty cycle, 100 is the maximum duty cycle possible

BlueSi2k

Correct me if im wrong but i think the duty cycle in the AEM software can go over 100 to work with staged injectors. When the number goes over a certain percentage, say 80%, the rest will be taken care of by the secondary injectors. If the duty cycle is 120% and the limit for primaries is 80%, the primaries will be at 80% and the secondaries will be at the equivalent of the other 40%. If you are not running staged injectors there is no reason for your duty cycle to ever go above 100.

BoostedSi

i was on the dyno...tuning

BoostedSi

My idle fuel pressure is at 52psi. How do i know if it falls when in boost?

1fstevo

if I view my fuel map in duty cycle form, my last cell at very top right hand corner is at 101.
This is on a -14.7psi to 21.75psi load scaling. I have never reached max set boost of 21.75@9000. I have only hit max of 18psi@8500 rpm. That particular cell is reading at 83.9. I am using 720cc RC and fuel pressure at 45psi. I honestly think I should ignore viewing the fuel map in duty cycle. AEM has alot more to figure out themselves and they havn't address the fuel map viewing in duty cycle form. Havn't you notice that the duty cycle fuel map looks as it's preset? Nothing is preset on ems, so there must be a option to set your own duty cycle curve and I havn't found that setting yet. So, in the conclusion, I think you are okay.


[Modified by [Evo]Hybrid, 4:27 AM 2/24/2003]

BoostedSi

THanks...

BoostedSi

HOw do you know when your injectors are maxed out?


[Modified by BoostedSi, 4:29 AM 2/24/2003]

BlueSi2k

AEM gets its duty cycle values from the pulsewidth values. It figures out what percent of the time the injector is open. The pulsewidth values are the raw values multiplied by the microsec/bit option. So duty cycle is not preset, it comes from your raw values.

BoostedSi

what pulse width is max for 780s?

BlueSi2k

Not sure of exact pulse width but at 100% duty cycle, they would be considered "maxed out"

1fstevo

Only way to find out is ask Aem engineers!!!

I suspect the duty cycle values is not a direct caluation from the pulse width since my raw graphical and pulse width graphical is identical but duty cycle is another set of curves. Have your tried changing the values in duty cycle form? change some values and then switch back to raw mode and view the result.

1fstevo

microsec/bit is currently set at 75. Change that value is same as rescale fuel map. But that is only one variable. how can one variable change the whole set of graph curve between duty cycle, pulse width, and raw?

boostedsol

Sam, talk to JP over at the AEM EMS forum.

BlueSi2k

The reason why the raw and p.w. curves look similar is becuse the pulsewidth is derived by multiplying the raw value by a single number makin the change linear. I'm sure dutycycle is dependent on a bunch of other factors.

tony1

Put a gauge on it and watch it on the dyno. As for the duty cycle, 85% is generally considered to be the max safely. You can do more, and many people do, but 85% is safe...

BlueSi2k

Changing the microsec/bit changes only changes pulsewidth not raw. The change in p.w. in turn creates a change in duty cycle. Yes, rescaling does change this number. This is because rescaling makes the highest raw number close to 240 to give better resolution. It then changes the value of microsec/bit in order to negate the actual fueling affects of changing the raw values. So in other words you are getting the same actual fuel but differen't raw values are displayed.

1fstevo

There you go, I want to know what the other factors are. If the other factor are set differently then duty cycle curve will change and then raw and pulse width will change with it. That means everyone's fuel curves will have their own way setting it. So, no supra guys will ever trade maps or compare to each other as everyone has different setting. LOL.

1fstevo

Can't be said better .

So who can explain why duty cycle value is a smooth climb from low to high regardless of what the raw values are and where it is derived from?