disable PE on turbo ls3(E38) tuning to have same condition on different load

[HAWAIIZUKA]

Hi HPTuners. I have researched a lot of time for how PE works. but still yet, It is not completely clear...

I'm not sure How PE table calculate how much fuel that motor needs and how PE actually add fuel by using values in PE table. VE tables supposed to make stoichiometric AFR and I think PE is just fuel adder and never leans out. and it's works in OL, so E38 doesn't do any fuel trim at those area that I set as PE

Okay, so I'm still running with PE on my car on street with no problem, but I think It does have rich spike problem if it's on high load condition such as on dyno.

I spend so much time to get solid stable AFR as I commanded partial throttle to WOT. I think I did great job for the street.

but if Im going on the dyno, I get rich spike and looks like it is related with high fuel pressure spike right after PE kicks in. and takes about 2mins of running to be nomal AFR even at idle(around 2 afr richer).

Might have something with the my fuel pump which is Lingenfelter twin fuel pump or with turbo and BOV to air. and I don't think that fuel pump module doesn't like vacuume to change so sudden like having boost spike and BOV to blow to the air.

So now I have thinking after dyno, what If I just control and get desired AFR by just VE table without PE with wideband??

I know this is not the right way to deal with E38. but I think I run out of idea other than change fuel system.
or I get right answer as long as car runs as I wanted, no matter how??

any opinions??

[10_SS]

I did this method (no pe) on my older LT1 ECU in boost... using a scaled back pure Speed Density tune... 100kpa = 200kpa in real world. It was open loop. It ran great but was rich in normal driving since it was open loop.

When I ran pure SD mode with my 2010 Camaro E38... it ran like crap. Lean throttle transitions... from what I read the E38 kinda runs in limp home mode without a MAF... allot of the normal features like burst knock don't work right... have to disable them completely without a MAF.

Not sure why your running rich for so long after returning to idle? If it's really due to high residual fuel pressure for some reason, you should fix that.

I don't see why your method of pure SD table fueling wouldn't work though... but I didn't like the way it ran when I used it this way.

[HAWAIIZUKA]

10_SS Thanks for your information!! I thought nobody wants to do that, so at least I can try pure SD.

I think everything using pressure stuffs act really slow in E38. such as boost enrichment.
fuel pressure was only raised up to almost 80psi when BOV open right after had boost spikes.

fuel pressure is usually going back in 5 secs of 1000rpm run, if it getting those problem on the dyno.
but I've never experienced when I'm driving on the street.

the reason why I'm trying to tune without PE is I was testing on the dyno, that I tried to change EQ value to set as 12.7 AFR. and actually car runs okay without any problem. (I put race gas mix n set timing as 9 as a insurance)
So I think as long as I don't use PE It is not happening even on heavy load dyno
I guess PE spray more gas on high load....

Can I ask you 10_SS
Why did you tune without PE?? did you have any problem with PE??

[10_SS]

Are you running a returnless fuel system?

Well PE only has one column... RPM... if it had LOAD also, then it might be ok, but if it did then it would basically be a VE table. Some OEM boosted OS's have another column.. .IAT... which helps, but our cars only have the PE with RPM only.

I came to the same conclusion as you, why use PE fuel when your running a pure SD tune, which runs off of RPM/Load axis unless you dont have tables above 100kpa... much more resolution than a simple RPM axis by using the full VE table.. there will never be a point you will be in light load, at any RPM, if your showing 150kpa... just makes sense to 0 the PE tables.

Now I wonder how fast the fueling will react in the SD VE tables.... if they react faster than the PE fueling then I may be also interested as I am also having problems related to fuel pressure loss at WOT... and with using a MAF only, I cannot adjust lighter load vs Heavy Load at different RPMs since my tune is setup for WOT only... when I run say 50% throttle under the same RPM, I run rich since my fuel pressure is higher than it is when at WOT.

BTW, if you choose this route and run Closed Loop, make sure you still enable PE mode... just 0 the PE enrich tables. This way it comes out of closed loop fuel correction above say 90kpa or whatever you choose.

[HAWAIIZUKA]

Thanks 10_SS for shareing opinions!!

Well PE only has one column... RPM... if it had LOAD also, then it might be ok, but if it did then it would basically be a VE table.

Well I just confirmed about that... I've never think VE actually read different cell when It has different load physically.... and PE is strictly follow RPM and act quicker. as far as I see on my data.

but still yet, I've never run without fuel trim neither adder, It'll be some challenging stuff but I think I can get new experience and knowing about my car. I'm making tune for pure SD and thank you for the advice about enable PE and set "0" stuffs. I was disabled PE…

Are you having fuel pressure problem on rail or on tank pressure sensor? and do you see any AFR spike with those pressure change??

And now I have another idea to use PE.
We set PE value as commanded AFR, and ECU calculate and add some fuel, but then we still have to take a time for tune it to make it as commanded AFR by VE table.

If “we”(not car does automatically) have to adjust to make commanded AFR by changing value in the VE table, I would make quick change by using PE and BE combination to less or more fuel to spray.with universal fit smooth VE table all around 2bar.
this sounds stupid but actually make sense than car trying to archiving commanded AFR without wide band to me.

after I finish make pure SD tune, I’ll try make with PE and set PE value as 1.15 but of course not to make 12.7AFR and make VE table to make desired AFR once. that is going to be street tune.
and I'll put that on dyno and make change by PE and BE to make desired AFR.

This is sounds so wrongfor E38 . but It'll be no problem as long as I'll try on my car.

[10_SS]

Yea I have no idea how the E38 will react as I've never tried it.. but this worked great on my 1995 LT1... pure SD tune all the way to 170kpa... others are using it all the way to 200kpa. This of course was a scaled tune (loss of 1/2 of the VE resolution)... but it worked really good. It was kinda hard to target certain cells in the RPM bands needed since there were so many cells, but it was worth the effort. And with the Histograms, you could just copy/paste the percents needed rather than try to remember what cells needed adjustments each time.

My Fuel pressure problem is related to the Whipple supercharger kit using the MSD boost a pump to band aid fix the massive loss of fuel pressure that would occur by leaving the system stock... it uses the stock fuel pump and larger injectors... but fuel pressure still drops about 20psi at the rail at full power... SO when I run 1/2 throttle and hit airflow cells tuned for higher fuel pressure... I run rich. The fix would be a better fuel pump (ZL1 would be just good enough for me).

The E38 adjusts for fuel pressure loss... however I hear it only does this up to 100kpa... not beyond

[HAWAIIZUKA]

for the fuel pressure drop, it is something like me, fuel pressure regulator control by vacuum and injector infos has something to do.
I'm pretty sure those MSD BAP works great and I've seen raised voltage, but the problem is how they change fuel pressure for PE commanded fuel.

but I'm actually trying to find the solutions so, here is something interesting regarding fuel pressures(you might already read those)

http://forums.corvetteforum.com/c6-f...eding-maf.html
I would agree with injector settings can make some stupid moves.

http://www.injectordynamics.com/Stec...reArticle.html

I made perfect match Histograms and I don't use those auto function... for WOT I always change number by looking at charts and if I see wrong AFR then I check which cell in the histrams needs to be adjust and change the value, and make it smooth around there. This takes time... but my AFR is super stable at WOT so I'm happy to spend time with it.

I'll make some different version tune, and post again with screenshot of my VCM scanner