F.A.S.T.: Tuning question. VE vs. O2. What's more important?

[MadPSI]

Alright, I've been chugging along on the Syclone for a few hours now and it's now up and running, and time to start putting some boost to it. I used a trusted person's configuration file and I have been tweaking the VE table to get the correction % close to 0 in all the cells. I left all the other tables alone. After talking to the engine builder today, he says that tuning it to minimize VE correction percentage is not as important as tuning it to a good O2 reading.

So...what comes first in this case? Or will tuning the VE table cause the O2 to become "honed in" anyways? What's a good reading with a WB O2 for FAST anyways?

Secondly, what comes next after I get the VE table down?

 

[foxspy]

You can have your O2 correction numbers at zero and the truck will still run like crap. You have to make sure that your air/fuel ratio table is setup correctly. The O2 correction is just letting you know if the VE numbers correspond to match the air fuel ratio in the air/fuel ratio table.

I had my O2 correction at zero and I was still getting slight pops, then I had to go into the air/fuel table and change the cells from 14.7 to 14.2, then you have to go back to the base fuel map and add fuel again and since I did that it runs much smoother.

 

[bobc455]

Originally posted by MadPSI
Alright, I've been chugging along on the Syclone for a few hours now and it's now up and running, and time to start putting some boost to it. I used a trusted person's configuration file and I have been tweaking the VE table to get the correction % close to 0 in all the cells. I left all the other tables alone. After talking to the engine builder today, he says that tuning it to minimize VE correction percentage is not as important as tuning it to a good O2 reading.

So...what comes first in this case? Or will tuning the VE table cause the O2 to become "honed in" anyways? What's a good reading with a WB O2 for FAST anyways?

Secondly, what comes next after I get the VE table down?

Sounds like you understand that the VE table is only to get the actual A/F (what the O2 sensor reads) to be the same as the target A/F table. That's a good first step! If you can get the whole table so you have 0% correction, then you win! However you'll never get 0%, try for 5% or less everywhere, 3% if you have more persistance.

As far as the A/F table goes, that's pretty much trial and error. If you get a surge at idle, try going richer, from 14.7 to 14.2 or 13.8 (depending on how radical your setup is). (Note: surging could also be too much timing!) Highway cruising is probably great at 14.7. WOT should be pretty rich, about 11.5 - 12:1- some time at the track will give you the best A/F ratio for WOT.

-Bob Cunningham

 

[V6 Beast]

I think you have to have the A/F ratio table set up with the correct target AF ratio first then edit the Base VE table until you get minimal correction.

The o2 correction is trying to correct to the target AF ratio in the AF table. For cars running boost I think it is usually in the 11.2-11.5 range

HTH

Sully

 

[Reggie West]

Brandon you are definitely on the right track in tuning.

I would say that once the fuel tables are dialed in, look at your timing tables and keep an eye on the EGTs as you make changes.

There are no absolutes with EGTs and tuning. No 2 motors like quite the same tune.

I try to keep the WOT runs at an A/F ratio of 11.3 or 11.5. My EGTs are in the 1650 range and stay around there.

Hope that helps

 

[MadPSI]

Thanks a lot for the advice guys...

We put about 10# of boost to the truck today and it was acting very well. No popping, missing, anything! No knock either. The VE table was almost dead-nuts as well, with the most correction being 2-3%. The setup was for a truck identical to ours, only with 72# injectors, as opposed to our 83#ers.

It's good to hear that everything seems to be going as expected. I did however notice that for a second or two the O2 readings were dipping into the high 9.xx range. It wasn't anywhere near WOT though, I guess I'll have to address that. Is a lower number richer or leaner?

I'm sure I'll have more questions as I go through the whole tuning process, it's good to know that I'm in good hands.

 

[foxspy]

THe lower the O2 reading, the richer it is.

14.0(parts air):1(part fuel), so if there's less air IE 9:1, then it's rich.