Pulse Width / Duty Cycle table inside

[John_D.]

Pulse Widths and duty cycle at various rpms:

[Magnus]

Very nice table. I'll add this to the engine tech when I get a chance. [img]smile.gif[/img]

To add.. many say not to push the injectors past 80% duty, at 100% the injectors never close.

Most of your cars shift at or below 5800 anyway, and when they DO rev to 6K it's only for a BRIEF moment.

[John_D.]

Thanks for the feedback. [img]smile.gif[/img]

I had run across the "code" ubb keyword a few days ago, and then got into this whole duty cycle thing too. So I realized it would be a good test to see if the formatting would hold up or not, using the code keyword. Looks like it did alright.

Yeah we talk about pulse widths on here from time to time, but without knowing duty cycle at a given rpm, it's hard to make any sense of them, so I think this will help.

Note - the last column is not 6500 rpms, but only 6300. I usually stop at 6000, but I noticed several people lately saying they were running up to 6200 or 6300, so I added one more column for them.

I have heard 85% as the target limit. Even without the whole injector lock / going static / erratic flow problems, I would think that still holding the injector open so late into the exhaust cycle does not give the best atomization of fuel in the intake, with no air moving through the runner at the time. So 80% is probably even a better number to shoot for.

[ March 31, 2003: Message edited by: John_D. ]</p>

[malloynx#2]

could this be why i'm having trouble at 6100+ rpms

[John_D.]

<blockquote>quote:</font><hr>Originally posted by malloynx#2:
could this be why i'm having trouble at 6100+ rpms<hr></blockquote>

If your pulse width is above 18, yep, it sure could. I was having some cutting out on top end with a big dry shot that needed more fuel than the injectors could flow, so I had to pull the shot back down some.

[malloynx#2]

well i ahve a wet shot, and i have seen 23ms pulse width before at 5300rpm

[John_D.]

<blockquote>quote:</font><hr>Originally posted by malloynx#2:
well i ahve a wet shot, and i have seen 23ms pulse width before at 5300rpm<hr></blockquote>

Yeah, I think when the pcm starts holding all 6 injectors open constantly, they don't flow properly, so you are probably missing out on some fuel on the top end from your injectors, even with the wet kit's fuel jet.

What are your o2's as you get up into that range?

[malloynx#2]

i'm seeing between .890's and .910's.. the faster i go the higher my 02's get

[John_D.]

The o2's sound good. I was just fishing around, to see if the pcm was seeing too much air, and trying to flow too much fuel, which can cause high pulse widths that are easy to fix.

So... Sounds like you need more injector [img]smile.gif[/img] , or less shot... :( If you are going to be getting into those high rpms.

[Magnus]

stay tuned...

[Magnus]

John, thank you very much. [img]smile.gif[/img]

http://engine.firebirdv6.com

I just put up your table but it might be nicer to have it in 250 RPM increments up to say 6500 starting from 4K

I can do that later, but for now it's up. [img]smile.gif[/img]

[Magnus]

I gave you a plug on the bottom of that page John, if you want me to put in your full name or anything, just let me know what it is an I will..

I'm all for giving credit where credit is due.

Thanks again man.

[ April 04, 2003: Message edited by: Magnus ]</p>

[John_D.]

Hey thanks for the notoriety! I feel like somebody now!! [img]smile.gif[/img] (which is a good contrast to fooling with this dratted bottle heater for the past three hours...)

Here is the table up to 6500, by 250's...

(I can email you the Excel file if that's better for you.)

[ April 05, 2003: Message edited by: John_D. ]</p>

[Magnus]

Updated..

Thanks once again for your contribution! [img]smile.gif[/img]