a few questions to answer...any help appreciated

[The Alchemist]

did my first customers car this week with EFIlive......quite an experience and I have a few questions as a result...and a few pearls of wisdom as well. We have a dyno dynamics dyno at work (for the record) and the car was a 2000 Holden SS with a bigbore, extractors, large t/B , large MAF and large intact pipe, engine standard.

One thing I noticed was that the engine AFR sat at 14.4:1 with the o2's "on" at idle and light throttle regardless of what I did to the VE table or the injector table or MAF table???? I can not find anywhere a "target AFR closed loop" table so I can modify it to 14.7:1.
I found the open loop table and sucessfully changed that which had the desired effect on AFR when in open loop mode but nothing for "closed loop" mode.
Can anyone help me here?
The weird thing was , that when I used the bidirectional controls and activated AFR control I could change it by 0.1 AFR and see the change on the dyno wide band, and when I had it set on 14.7:1 I got 14.7:1 on the dyno AFR, turn it off and back to 14.4:1 we go. Very strange.......

Secondly , when the car came in it had very lean mixtures when in open loop mode indicating that the physical changes made to the intake and exhaust had overrun the standard engine calibration. It took me a while but I found that the biggest effect on AFR is made by changing the MAF calibration!!!!

In fact before I adjusted the MAF table I tried the IFR table and VE table, both had hardly no effect on getting my AFR's back up to the" 14's" at all! (when in open loop) It was a very frustrating time......I was being very cautious as it was a customers car not my own

Turned out that the MAF needed around 5% increase at idle load , once off idle needed a 10% increase up to 2000rpm/light load say 45 KPA then a 15% increase up to 5000rpm full load 100kpa, then around 19% up to 6000rpm full load (Which interestingly enough only moved one calibration point on the MAF table) This adjustment to the MAF table gave me mixtures I could work with when using the VE table from there on.

I have another 2 customers next week thankfully both with standard MAF's, so the job should be much more straight foward!

I'm assuming that checking the AFR's while in open loop is a good starting point when using the EFILIVE system? Is this what other tuners do? To be honest I was surprised at how far out thing were to start with. Obviously the new larger MAF had a major effect and i thought that people here should know.

In the end the car made huge torque, infact it had 95% of its peak torque available at just 2000rpm !!!! It made 210KW at the wheels in 3rd gear shootout mode, which was down a bit and what I'd thought it would make as I have dynoed many "standard" ones making similar rwkw figures but no where near the torque this thing had

cheers Mike

[GMPX]

When you say the car had a 'larger' MAF, do you mean it was hogged out or was it a real 85mm MAF?.
If it was the 85mm MAF you would have needed to use the MAF Flow table from an 85mm MAF, with that table wrong things would have been hit and miss.

You will find the cars you get with std MAF's will be alot more straight forward. I am not a believer of changing the MAF or IFR table unless the engine has a different MAF or Injectors.
You will find the values in the PE table will match pretty close if none of that has been messed with.

Cheers,
Ross

[The Alchemist]

Hi Ross, thanks for your reply...It was a real 85mm MAF and man was it a challange as I had no 85mm MAF table.
Do you happen to know where I could get one ? I have designed my own as you can see by my post but to have the correct one would be great.
Any ideas on my other questions?
Mike

[GMPX]

Head on over to - http://stealthv.nitro-nights.com/tunes.htm
Download say a 6.0L truck file, I am pretty sure they all ran an 85mm MAF (Anyone confirm?).

Cheers,
Ross

[The Alchemist]

downloaded a truck 6l file and had a look at the MAF calibration....for a given HZ it runs a lower Grams/sec airflow figure.

I found I had to increase the airflow figure at a given HZ to get the mixtures right, verified that on the dyno. Increasing the airflow would increase the fuel delivery I'd have thought.......

cheers Mike

[The Alchemist]

Hi there, did a second customer car today...the whole process went much more smoothly. This car also had a larger MAF and T/Body etc etc ....

This time I tuned with the MAF until I got the mixtures I wanted then fine tuned the VE table, although it needed a little alteration. Noteworthy was that when you were at low RPM day 1800-2000rpm the airspeed would drop off at about 85-90 KPA leading to a rich mixture just at that point. This was almost tuned out my dropping the VE table away at that point to a very low effecientcy thus reducing the fuel delivered and correcting the rich mixture.

It turns out that a 5% MAF table increase for idle MAF levels say up to 8g/s then up to a 10% MAF increase for the rest of the table gave me the best mixtures to tune with.....
The car made 217rwkw on a dyno dymanics dyno.

Cheers Mike

[joecar]

Alchemist,
Good info, thanks.
Looks like you'll be writing the book on how to tune...
8)

[leres]

One thing I noticed was that the engine AFR sat at 14.4:1 with the o2's "on" at idle and light throttle regardless of what I did to the VE table or the injector table or MAF table????

Do you guys have oxygenated fuel in New Zealand?

I just happened to be reading Probst's Corvette Fuel Injection & Electronic Engine Management:

Under the Oxygen Sensor's control, oxygenated fuel is metered to deliver an air/fuel ratio to about 14.2:1 at the injectors. The resulting exhaust is about the same as the exhaust from buring gasoline formulated without oxygen, the traditional 14.7:1.

Otherwise, could there be a leak that allowed air to enter the engine without being measured by the MAF?

[Blacky]

One thing I noticed was that the engine AFR sat at 14.4:1 with the o2's "on" at idle and light throttle regardless of what I did to the VE table or the injector table or MAF table???? I can not find anywhere a "target AFR closed loop" table so I can modify it to 14.7:1.

Try looking at {B3601}, under
Engine Calibration->Fuel->Mixture->Parameters.

Regards
Paul

[The Alchemist]

yes Paul, I saw that "engine Calibration->Fuel->Mixture->Parameters." and it has a defined stoch figure of 14.63:1 that the pcm uses as a reference point. Changing this seemed to make little difference to the 14.4:1 I was getting.
However what I have discovered is that on later model pcm calibrations there is a "lean cruise" section where the AFR can be defined via a seperate map. The car I was originally working on was a 2000 year and had no such calibration in its PCM and is probably hard coded.