First Tuning Project - help with power drop

[RPE-Tuning]

Dear fellows,

Calling in your experience on something I encountered on a car I tuned - my first XR6T (BA)

So I've gone through the usual stuff and nothing really increased power much. Something odd happened -I couldn't get consistent power runs - sometimes power would climb nicely and others there would be a big dip in the power curve - it seemed to improve when I leaned it a bit (0,83 - 0,85 lambda) - all this on stock 4,5 psi stock boost.

I then made a huge improvement copying BKT and MBT Timing tables and adding some timing and also some boost resulting in the dyno printouts in appendix.
Power jumped from 190 kw to 240 kw but with a huge drop after 5000 that happened everytime. Has anyone encountered anything similar?

Timing looked acceptable (not dropping), boost stable and fuel safe. Im wondering if it can be valve springs?

Please find dyno attached.XR6TPat.jpg

Regards and many thanks,
Paulo @ RPE Tuning

[RPE-Tuning]

Hi!

No one came accross nothing similar? Really lost as for the cause of this.

I will have the car back in a couple of weeks and it would be good to fix it if possible.

Thanks,
Paulo

[timwds]

So many factors...

Changing desired lambda can drastically alter the spark advance because of correction tables.
I also wouldn't be expecting to gain much if anything at stock boost levels.
Valve springs shouldn't be an issue at stock boost.

IAT or CH temps too high on the dyno?
Were you getting knock retard?

[RPE-Tuning]

Hey timwds,

Thanks for your answer.

I didn't change desired lambda. I leaned it a bit using the MAP per Airmass. I also zeroed the lambda spark correction table.

The fact is I was getting lower timing than Borderline Knock Table for some reason. Knock wasn't audible but could have happened.

IATs were below 40? and I did decrease the IAT spark compensation. Coolant was stable.

Knock retard I don't know if I can log it with hp tuners. I though we couldn't.

Regards,
Paulo

[timwds]

If your knock sensors are enabled you probably won't hear knock as they are pretty good at their job.

No, HPT can't log knock but you can generally see it if you log spark advance. The line goes really spiky and you see the timing drop from where it should be, crude but gives you the idea.

If you zero out the lambda spark table, you'll be up 3 degrees in the mid range and down 5 degrees up top so make sure you you've made those corrections to the BLK table. I've found it easier you leave the correction tables stock and use an excel spreadsheet to calculate the output. I used to zero it out but found you can lose power/driveability in the low boost/TPS areas because fueling vs spark is wrong, they are there for a reason.

[bugsy]

Using the map per airmass tables will also change the timing as it changes the calculated load.
Try putting the airmass back to ford standard and then change the desired lambda.
I found this only after I had retuned via the air mass tables.

[RPE-Tuning]

Thank you both. Great insights!

1 - Understood on the spark corrections, I do agree that they are there for a reason.

2 - Bugsy, I though that was the correct way to alter fueling, according to the Ford VE document (which is very good btw!). The only table I can find is the fuel base which is RPM vs TPS and only goes to 48,83%. Is this the value used for WOT as well?

I need to get the car back and play with it some more, I'm curious to try and enable the torque management as I've read about it doing weird things to the car.

Final question - Do you generally disable LTFT and tune to minimize STFT?

Regards,
Paulo

[timwds]

FUEL BASE vs. RPM vs. TPS is were you tell you adjust open loop fueling. There is no need to go higher than 48% since that is full boost anyway.
Air flow tables are ford's equivalent of a VE map which should only be changed if AFRs are not meeting the FUEL BASE target like if you changed plenums, turbo, porting, exhaust etc.
OPEN LOOP FUEL TPS THRESH vs. RPM is the TPS % that the PCM changes from closed to open loop fueling.

You can leave LTFT on and adjust Airflow tables until LTFT reaches near zero for light-mid throttle tuning. I'm not sure if fuel trims have an affect on open loop fueling???

[DarrylC]

RPE-Tuning, it has been posted before but the easiest way to tune is to leave the SD tables factory and get your injectors dialled in so that your delivered lambda is close to what is being commanded and your long term fuel trims are as close to zero as you can get them. Then adjust the Fuel Base table to get the desired lambda. So if you command 0.8 and see 0.82 then multiple 0.8 by 0.8/0.82 = 0.78. See:

http://www.hptuners.com/forum/showth...l=1#post383163

Keep reading until you hit my post. I encountered too little timing due to adding fuel to the SD tables and thus increasing load. So by doing the above have not altered the SD tables and you can then work on your other load based tables like the spark tables. If you alter the SD tables then you will need to alter the spark tables for the new load and I am not sure I have done this properly or if it is achievable on HP Tuners as there might be some tables not being shown.

Have a read of slack dog tune:

http://www.hptuners.com/forum/showth...Slack-dog-tune

Now the spark tables are a bit of an issue as to get the commanded spark versus delivered can be tricky. I flatten the table and zero the lambda corrections when on boost. There are some really good training tunes here:

http://www.hptuners.com/forum/showth...nado-ute-tunes

Hope this helps, Darryl.

[RPE-Tuning]

Many thanks everyone. I will surely implement your teachings as they make total sense. Lots to learn still!

I will report back with results with the new methods!

Paulo

[richardpalinkas]

Hey did you find the issue to the power drop? Having similar issues myself

[lukearmstrong1990]

in my experience most mild to medium build barras with factory camshafts roll over quite early anyway. I generally find the roll over in power to be either mechanical or a result of the parts bolted on