WOT aft and timing

[maudyZ28]

OK,

after a run at the strip I reverted back to my stock PE vs rpm of 11.7 all over, previously I commanded 12.6 but it started to knock a bit at the top end of the revs so it was leaning out or timing was too advanced.

Im going to do more logging and a VE after my headers but wanted to get a bit of theory straight, which would be best vs stock timing and fuel at PE

1: PE vs RPM to richen from 12.6 to 12.2 and leave stock timing (still rich)
2: PE vs RPM to be 12.6 across the board and reduce timing from 4000 rpm by 2 deg
3: PE vs RPM to go like 13.2 to 12.8 and run 2-3 deg less timing everywhere or similar to a LS6 Z06 spark table

Basically from what I understand, the idea mix is 12.8-12.6 afr, and then you advance timing to suite (if i had a dyno). But the stock trim runs 11.7 and like 27.5-28 deg at WOT @ 4000 rpm (ish) is this just to make the over rich mixture burn more completely as there is more time for it to burn, but actually doesn't yield any power due to it been overly rich. SO I would get more power from a leaner mix closer to 12.6 with less than stock timing?

[WeathermanShawn]

MaudyZ28:

You being a scientist..This is pretty good reading.

http:///www.innovatemotorsports.com/resources/rich.php

http:///www.innovatemotorsports.com/resources/myths.php

I like their approach. I use a flat 12.7 AFR (easier to hit Commanded with one EQ number..1.152 ) and work on spark to eliminate KR. Every car is different, but 99% of the time I eliminate any KR with spark retard and not more fuel.

Just an opinion, but Innovate really digs into the application of it.

Cheers..

[maudyZ28]

thanks Shawn (ok to call you sean?? im Luke btw)

Thats essentially what I wanted to know, reduce timing and fuel from stock = more power. I might just use the LS6 Z06 spark table and see how it goes. Need to dial in a better VE though.

I assumed stock timing was high to help burn more fuel as it was a super rich mix

I do some bedtime reading, I need to concentrate at work now but keep reading tuning stuff :(

[WeathermanShawn]

Hi Luke:

You can call me Shawn (my Mother liked it) or Weatherman..or WeathermanShawn.. True, we may not be very popular after the Icelandic Volcano, but Weather is still my main passion and occupation (I am very lucky).

As long as you don't call me any names, you can call me whatever you like. I do prefer the Shawn spelling though..

Are there that many F-bodies in your area, or is yours 'one of a kind'?
Have fun tuning!

[maudyZ28]

cool, sorry i put Shawn and then Sean too, but it will be Shawn from now lol

Well in the UK there are not that many f-bodies, its unusual to see more than about 4 more at an event. Then there are even less who modify there cars. Plus im from the north of UK and there is literally about 2-3 american specialist up here and the majority of the money and cars are in the south, London area etc

I like to think my camaro is one of a kind, got a few good comments this weekend at the races so that was nice

It good your weather is you job and passion, im currently in a phd studying massive star formation but just getting into it but find myself not being bothered sometime, which is bad. I'll keep at it and see how it goes

[5.7ute]

OK,

after a run at the strip I reverted back to my stock PE vs rpm of 11.7 all over, previously I commanded 12.6 but it started to knock a bit at the top end of the revs so it was leaning out or timing was too advanced.

Im going to do more logging and a VE after my headers but wanted to get a bit of theory straight, which would be best vs stock timing and fuel at PE

1: PE vs RPM to richen from 12.6 to 12.2 and leave stock timing (still rich)
2: PE vs RPM to be 12.6 across the board and reduce timing from 4000 rpm by 2 deg
3: PE vs RPM to go like 13.2 to 12.8 and run 2-3 deg less timing everywhere or similar to a LS6 Z06 spark table

Basically from what I understand, the idea mix is 12.8-12.6 afr, and then you advance timing to suite (if i had a dyno). But the stock trim runs 11.7 and like 27.5-28 deg at WOT @ 4000 rpm (ish) is this just to make the over rich mixture burn more completely as there is more time for it to burn, but actually doesn't yield any power due to it been overly rich. SO I would get more power from a leaner mix closer to 12.6 with less than stock timing?

maudyZ28 how is your commanded versus actual AFR from a wideband on the track?
The general rule is timing is lower around peak torque & then ramped back up in the higher RPM band. Running a leaner AFR will only result in a few extra HP & IMO is not worth the risk in an everyday driver.(unless you can verify that you are not on the knock threshold with a dyno, knock phones etc)

[maudyZ28]

hi 5.7ute,

I dont have a wide band, hence just changed one thing at a time, did a run and see the out come. There were like 4 points in the log file where the car knocked, upto a max of 5 deg was timing was pulled in 3rd gear at 4000rpm (worst) just as the MAF takes over right? Or is the MAF fully incharge on WOT.

I understand how the timing ramps, goes from like 24-28 deg on stock tune from about 3500-6000 rpm. My issue was that the commanded AFR is 11.7 which is clearly far from optimum. Essentially I reduced this to 12.6 commanded to see if I got knock, which I did but only 2 deg in 3rd, again at 4000rpm. So I richened it to 12.45 and the knock was WORSE, so it appears that this is actually burning faster (i really want to know how it relates to real AFR) for the same timing and knock was 5 deg as above. Basically I am now going to reduce the timing with AFR at 12.45. The innovate links Shawn posted are really useful, basically less fuel and timing gets similar or more power (a few hp like you say) than rich and more timing. And I would prefer to run less fuel and timing to achieve the same goal as super rich more timing

One question again (not at WOT just driving normal), say when running MAF only (enable at 400 rpm so that is the only thing controlling fueling right?) if I command 14.63 and a WB says it is leaner or richer, even though everything else is the stock tune does this point to incorrect MAF calibration OR incorrect injector rates OR the O2 switch point being off so adjusting trims??? I assume the latter with the O2s so I would change these such that I get a roughly stable 14.63 as I would assume the MAF and IFR are correct, or are the O2 best at 450mv as was mentioned before??

[WeathermanShawn]

Maudy..Luke:

I will let 5.7ute explain all the intricacies of the airflow contribution from MAF/VE and resulting injector flow. With the airflow calculation of MAF set at 400 Rpm and in closed-loop you will be adjusting the MAF frequencies vs airflow (g/s) to correctly model the airflow.

If you adjust the Injector Flow Rate (frowned upon) your MAF airflow (CYLAIR) and DYNCYLAIR (SD) will never match. You will erratic fueling upon transient and widely swinging Trims.

It is best to achieve a harmonious MAF and VE Table airflow. If you do it open-loop try the AUTOVE method. If you prefer closed-loop with the narrowbands trimming and you are keeping your MAF, you might try WeathermanShawn's Tutorial method to calibrate MAF, VE, and Trims simultaneously. I have linked a short but precise link that Joecar wrote that really explains the difference..http://forum.efilive.com/showpost.ph...0&postcount=21..

The wideband becomes essential to tuning both for closed-loop and for verifying Commanded AFR vs actual during PE Mode and WOT. It only takes a about 4-6 seconds to detonate an engine..there is no other reliable method to verify your fueling under load.

The instructions on O2 switch-points is more of a suggestion to make closed-loop tuning a little more precise. For your purposes I would keep the O2 switchpoints stock. It has a minimal effect on your actual AFR's. It is a Tutorial method only.

Hope that clears it up a little. I have simplified the process. 5.7ute and others can tell you all the precise contributions..but that is the 'cliff-note' version..

[maudyZ28]

thanks again Shawn, im at the stage where I understand it but need more info on what car is doing, IE WB !!!!

Think I'll just do your calcVE again and leave the rest till I get the WB, kinda spent a lot on EFI live £600 and WB is another £150 , I could have just bought a stall converter and cam and let the car run crap hahah. plus its really hard to do the VE tuning on the street with an A4 with 2.73 highway gears!! Have to run about in 2nd gear between 0-160km/h

How do you think headers will affect the response of the O2 sensors, or will they be ok still at stock value?

[WeathermanShawn]

Luke:

Some people still run stock setting O2 switchpoint setting with headers. I experimented with a range of 400-550 mv and tried to align up a mv reading to my B3601 of 14.63 AFR. I settled on 550mv across the board. I do not necessarily recommend that setting to everyone..but thats where I ended up.

You will have to experiment...

Regards..