FAST question about WOT

[foxspy]

Hey guys,

I've been tuning my truck and started to mess w/ the data logging. And after looking over the recorded runs, I am WAY rich at WOT. I have wide band O2 and it's showing that I'm down to 9.56 A/F ratio and 99% duty cycle on my 40 lb/hr injectors. This is in a 1990 Chevy 454ss truck w/ a 502" motor, w/ roughly 600hp.

Here's my question. What is a good rule of thumb for adding pulse width vs. MAP rate of change or TPS rate of change. I don't know if I need to subtract some fuel from the base VE table, or take out some pulse width on the accerleration enrichment tables.

Thanks for the help.

 

[bobc455]

Sounds like you don't understand the AE tables. They have nothing to do with when you accelerate, they just prevent a bog when you stab the gas. Don't touch them for this situation.

At first, I would guess that you need to reduce your VE numbers at WOT. But I would double-check the operational parameters (like engine size, injector size, injector opening time, etc.) because 99% DC is too high. Are you sure those injectors are big enough? You should only be at about 80-85% duty cycle max (although once you straighten out your VE tables, you might be okay).

Is your WB O2 operational? It should be making some correction to bring your A/F closer to your target.

-Bob Cunningham

 

[Chuck Leeper]

Jector size??

Doing the math indicates that IF you are making 600FWHP, then the 99% DC is close to correct.[w/ the A/F at 9, you obviously are not] The calcs show that:
600FWHP at a BSFC of .5 and a DC of .99 requires a 38# inj.
As Bob said, you may need different injs.
Doing the math w/ a reasonable DC of .85, indicates 44# inj. The next stop on the "way up" on injs is 50. I'd look at a set of them to be safe. [This assumes you have the VE correct]
Follow Bob's advice and get the O2 correction working, and see if it's pulling fuel like it should be. Once you get the % of fuel removal, you can then reduce the WOT VE values in a comparable amt.
What do you have in the setup for add/remove limits??

As I remember, 9.6 A/F is as low as the system will go. Bob??

 

[foxspy]

Yes, the wide band is working properly, but I only have -5% correction at WOT.

At the same RPM and same MAP the a/f ratio was at 11.5:1, then when I shifted, the MAP dropped and as RPMs came back up that's when it went down to 9.6:1, so I was maybe thinking I have too much pulse width added vs. MAP rate of change. I'm going to reduce the accerleration enrichment tables and adjust the VE table and see what I get.

Another question, what injector opening time should I be running?

Thanks everyone,

 

[bobc455]

Are you running a blower or turbo(s)?

-Bob Cunningham

 

[foxspy]

No blower, no turbo, not yet anyways.

 

[Chuck Leeper]

Injector time??

I'd start at 1MS.
Do you have the closed loop and the speed density activated??

 

[bobc455]

Unless you are going 1/2 throttle down the dragstrip and stepping on the gas then letting off, the AE vs. MAP will be irrelevant for you. My first guess is the VE table, but I also think your injectors may be too small and maybe you have other problems like incorrect settings in the "operational parameters".

After you double check your operational parameters, I would overlay the log onto your VE table and reduce the values. It will take some trial and error before you get the VE table dialed in.

If you only have -5% correction, you might also want to temporarily give the O2 sensor some more leeway to make correction (look for O2 correction limit table).

-Bob Cunningham

 

[foxspy]

Yes, both closed loop and speed density are activated.

Thanks everyone, I'll start playing w/ it.

 

[norbs]

you must look at the a/f ratio on a constant load ie all of 3rd gear, don't look at the a/f during shifts, and deacceleration, it wil go full rich or full lean depending on the situation, and it is quite common. All my logs show erratic readings during a shift for a few frames, just concentrate on the most constant load area's.