VE Table fall off at 100 kpa

[INSANEREINDEER]

Can someone explain to me the cause of the dip at 0 psi manifold pressure (1 atm or 14.7psi) in the tables? I've playing with HP tuners for around 3 years on and off tuning my own turbo car. My car is almost tuned and runs very well for the most part up to 12.5 psi. It still need tweaking but it's something I work on for a bit, get bored and come back to later after I've read a little more. I've read countless articles and post on details. I've read some thing like "you'll definitely flow more air at 100 kpa @ 3000 rpm then 90" but for me this isn't the case. I've smoothed out my VE table to have a constant upward tread (with small dips) but after doing that multiple times, my VE table constantly comes back to this major fall off at 100kpa or so. Whats the reason behind this?

5.3L truck engine with only LS6 valve springs, 76 mm turbo.

Tune 1 is my current tune.
Tune 2 is one that was given to me from a buddy who had a tuner do his car when I first got HP tuners.

They both have a dip around 0 psi manifold pressure. Is this something to do with the net 0 pressure between vacuum/boost causing neither a suction, nor pressure that leads to the fall off of the VE? Am I doing something wrong? I have a histo filter to only log with TPS is above 5% and even then I selectively pull out data from the log to input in the VE, then hand smooth the match around it. No copying and paste histograms very much. Learned very earlier on that I get a bunch of garbage.

tune 1.hpt
tune 2.hpt

I think it's the increase of fuel pressure from my hobbs switch a 4 psi. I assume this isn't normal and I assume the regulator just can't deal with the instant pressure.

[lukearmstrong1990]

someone paid for tune 2??? wow.

tune 1 has BE as soon as its at 100kpa. try delay it until 110kpa and make sure the injectors are scaled to the correct style of fuel system.

the BE and PE values are also all over the place, it looks lke someone is trying to tune WOT with them instead of VE

[kingtal0n]

You can get a $20 0-5v transducer from ebay (pressure -15 to 15psi or 0 to 30psi) and use that 5v analog signal the same way you use a wideband sensor input (through the EGR or similar) to import the data into scanner,

in other words. You can log fuel pressure (or oil pressure, or crankcase pressure, etc...) for $20 a pop


Also. I cant see the tune on this computer. But i have a feeling the answer lies in the transition between PE and BE or VE and PE. basically what I did to my VE map was tune it to increase in richness slightly(63-84KPA), so I can delay PE first. That way it doesn't need PE to get extra fuel 'suddenly'. Then as I approach 85KPA I pull the VE fuel out so PE does it's job. Then, the same for BE, give a slight bump in the VE line between 95-105KPA then let BE do the work from 105+

Theres a delay and you get to set the delay. The thing is, if you ask for "NO DELAY" then when you step down gradually at low RPM it could flood easily and quickly (hurts throttle response) if the VE map isn't perfect. So intsead I use a longer PE delay so the fuel creeps in a bit more slowly and make sure the VE map carries the transition. Sometimes you just want a little fuel for part throttle and on a turbo engine that happens at very low throttle percentages, you can get 85KPA with 37% TPS for example on my engine. So I keep it out of PE from say 65-85KPA and use an VE map a/f ratio of around 13:1 or 12.8:1 and let PE bring that down to 12.4-12.0 as it crosses threshold of 86-100KPA

[INSANEREINDEER]

someone paid for tune 2??? wow.

tune 1 has BE as soon as its at 100kpa. try delay it until 110kpa and make sure the injectors are scaled to the correct style of fuel system.

the BE and PE values are also all over the place, it looks lke someone is trying to tune WOT with them instead of VE

Yes, $700. I realize now that this was a very BAD tune to try to learn on from methods and changes. Surprisingly, tune 2 last 4 yeas making 800+ HP on a stock 6.0 before the ECU was changed to Holly.
What changes do you recommend for the PE/BE tables? I just picked a set of AFRs I thought was safe for boost while learning and left them. I tune using ARF error on the VE table. PE/BE should start at +12 and fall down to 11.3+. I haven't made it far enough with my VE table yet to really get into fine tuning these. The dip has been throwing me off for a good while making me think I've been doing something completely wrong.

You can get a $20 0-5v transducer from ebay (pressure -15 to 15psi or 0 to 30psi) and use that 5v analog signal the same way you use a wideband sensor input (through the EGR or similar) to import the data into scanner,

in other words. You can log fuel pressure (or oil pressure, or crankcase pressure, etc...) for $20 a pop


Also. I cant see the tune on this computer. But i have a feeling the answer lies in the transition between PE and BE or VE and PE. basically what I did to my VE map was tune it to increase in richness slightly(63-84KPA), so I can delay PE first. That way it doesn't need PE to get extra fuel 'suddenly'. Then as I approach 85KPA I pull the VE fuel out so PE does it's job. Then, the same for BE, give a slight bump in the VE line between 95-105KPA then let BE do the work from 105+

Theres a delay and you get to set the delay. The thing is, if you ask for "NO DELAY" then when you step down gradually at low RPM it could flood easily and quickly (hurts throttle response) if the VE map isn't perfect. So intsead I use a longer PE delay so the fuel creeps in a bit more slowly and make sure the VE map carries the transition. Sometimes you just want a little fuel for part throttle and on a turbo engine that happens at very low throttle percentages, you can get 85KPA with 37% TPS for example on my engine. So I keep it out of PE from say 65-85KPA and use an VE map a/f ratio of around 13:1 or 12.8:1 and let PE bring that down to 12.4-12.0 as it crosses threshold of 86-100KPA

I did buy a fuel pressure sending unit the moment I found out and started logging it. I get an increase in pressure from 58-72ish with 5 lbs of boost which is more than it should be. I guess my fuel pumps are flowing two much through my automotive regulator that it can't keep up? Stock NA 300zx fuel pump (~max HP 400) and Walbro 255 on 4PSI hobbs switch.

Not sure how you're going to use a 30 psi sensor you recommended on a 58psi base fuel system though. I purchased a 100psi off amazon with harness for $18.

Thanks for the other info. I will look into that more and give it a shot.