Initial drop in RP

SPEEDSHIFT

SPEEDSHIFT

New member
Looking at my logs in HP Tuners I am having a problem dropping rail pressure for a second as I launch from 25% to 100% throttle. I have been told to drill the feed port on the rail a little larger as my PPE dual pump kit just Ys into the stock feed location and is not a dual feed to the rail. I have also been told to adjust the FCA amperage I believe in my tuning, but I am unsure what to set it at... anyone have some suggestions?

I just have a hard time getting on top of my charger from under 20psi of boost, thought maybe getting some more pressure would help get it going as there is about 5000psi difference between my desired pressure and actual.

Fueling is:

125% over injectors
Drilled 6.7 feed tubes
PPE Dual pump kit. 10mm stroker on bottom, stock dmax pump up top.
Dual Airdog 165s
 
These are two different logs, where I changed the defueling limits for RPM, but if you look at the bottom row on both logs in green and blue lines you can see the initial drop in RP.

39985345e51abcda3a21e05678626e90.jpg
 
Last edited:
You have the regulator minimum duty cycle set close to zero? You could try setting the voltage graph to zero on the last data point (at max fuel flow).

Have you logged the duty cycle to see if it commands a low value off the hit? Could be something to adjust in the pid tables too but that can be easy to screw up. There should be slow and fast gain adjustments.
 
Yea Duty Cycle base map is where I would start. The FCA Amperage will help on the big end when pressure is starting to drop but on the tip in, base DC will help.
 
Okay, I have tried messing with the tuning and nothing has made a difference. Still has a 5-6000k psi drop when i first go to 100% throttle.

I am thinking about changing my dual pump kit to one that feeds the rail in two spots or using one of those flexible dual feed lines II sells.
 
Probs won’t make a difference where/how many holes you feed the rail with. Lots of huge hp are single feeding 6.7 rails with much success, including me, except for the huge hp part :)

fwiw the updated fleece dual pump kit for a 6.7 uses the gear driven pump as the distribution block instead of two extra lines and a sensor block like you usually see in the ATS and old fleece kits, and just feeds the rail at the single stock location
 
Poulina said:
Probs won’t make a difference where/how many holes you feed the rail with. Lots of huge hp are single feeding 6.7 rails with much success, including me, except for the huge hp part :)

fwiw the updated fleece dual pump kit for a 6.7 uses the gear driven pump as the distribution block instead of two extra lines and a sensor block like you usually see in the ATS and old fleece kits, and just feeds the rail at the single stock location
Click to expand...

Maybe the 6.7 rail is the way to go then, it looks a little larger and the added volume should help with my issue... I really need that extra pressure off the line to get this charger lit.
 
What does the FCA amps drop to when you have the drop in rail pressure? In the data log does the curve of the FCA amps match the drop in rail pressure?
 
SPEEDSHIFT said:
Ill take a look at it. Wouldnt it match the desired pressure?
Click to expand...

The ecm will continue to reduce the fca amps trying to maintain rail pressure. You would see this if you have a problem with your setup being able to have enough pressure/volume to met commanded rail pressure. If it can't maintain rail pressure the fca amps should end up very low.

If it's a tuning problem you will see the fca amps go to a set amount as the actual rail pressure continues to fall.

Posting a pic of the graphs like you did above including the fca amps would be best.

Paul
 
Just out of curiosity, do you know the pressure from the airdogs to the hp pumps? Possible the airdogs pressure cant react fast enough with the fuel demand?
 
paulb said:
The ecm will continue to reduce the fca amps trying to maintain rail pressure. You would see this if you have a problem with your setup being able to have enough pressure/volume to met commanded rail pressure. If it can't maintain rail pressure the fca amps should end up very low.

If it's a tuning problem you will see the fca amps go to a set amount as the actual rail pressure continues to fall.

Posting a pic of the graphs like you did above including the fca amps would be best.

Paul
Click to expand...

Gotcha, ill try that this weekend. Looking in my logger my options are:

FCA DC Actual
FCA DC Desired
FCA Current
FCA Volts

Which ones should I log?
 
skilletky said:
Just out of curiosity, do you know the pressure from the airdogs to the hp pumps? Possible the airdogs pressure cant react fast enough with the fuel demand?
Click to expand...

I havent checked, I just feel there is more than enough supply volume/pressure with dual lift pumps with 8AN lines from a sump, but I guess you never know. I will put a gauge on them to see.
 
You must log in or register to reply here.
Back
Top