truckdoug

iTrader: (25)

so this year's thrown together combo of a small duration, .600" lift cam, 6 liter SBE with cnc'd heads and the little 7875 turbo has some funny characteristics as I tune it.

aside from being capable of doing ***-puckering burnouts on drag radials at freeway speeds, probably my biggest issue is the turbo will spool before i'm in PE mode.

like cruising on the freeway 60mph in 4th (80e) just puttering along 15% throttle and I go to pass someone with like 40% throttle

this will spool the turbo to 1 or 2 psi, but i'm not in PE so it's only commanding stoich or thereabouts.

I have my PE enable set to 50% tps.

This is on a p59 Flex fuel computer with the abbreviated VE table. Running about 50% corn right now

All fuel trims and learns off, CL disabled.

this is not tip-in or burst knock. It has the very clear stair-step look of actual knock, but not a whole lot of retard...about 3*


so the million peso question...


So, should I lower my PE enable ? Or should I try the BE table?

I have never used the BE table before as I'm told it lags. But if I make my PE and BE the same values can the BE work for this low throttle angle enrichment?

Will I still get my fast acting PE at the strip or will I need to disable BE?


school me up

JoeNova

PE has to be enabled for BE to work. You can lower TPS or lower Kpa for PE enable. I usually set TPS % very low and set KpA a little higher.

truckdoug

iTrader: (25)

Joe do you use BE or put all your fuel in via PE?

the latter is currently that's how I do it.

what is "very low TPS" to you?

my KpA enable is very low like 30, so basically power enrichment for me is a function of throttle angle.

i'm reading right from the BE table description:

"the pcm will use the richer of this table (BE) and the PE table to determine fueling. its is useful to some supercharged and turbocharged engines where boost does not correlate to rpm"


damn if that doesn't sound exactly like what I need.

rpturbo

iTrader: (47)

Sounds like we are building almost the exact same engine combo setup. Your ahead of me a few months. I know I will be using these questions your posting to help with my tune in the near future.

truckdoug

iTrader: (25)

it's a beast, but the added grunt of the six liter and faster spool isnt gonna help my traction woes at the track any lol

brandon6.0

iTrader: (32)

I would set PE to 40% throttle and around 80kpa. This will allow PE to start before boost comes on. U can play with the PE enrichment ratio to lean or fatten the fueling in the lower rpm areas.

Just gotta play with it and see what it likes.

truckdoug

iTrader: (25)

yeah thats what I did today and the knock is gone. have to trim up the VE some of course now.

still very curious about those that use BE fueling. damn subeone is never here when you need him!

NicD

iTrader: (7)

Don't use BE, it's not reliable enough to depend on with multi second delays which means don't use it at all.

truckdoug

iTrader: (25)

well i did the unthinkable and turned the BE on. it's set leaner than PE but it appears to work plenty quick. i can roll into low boost without knock now.

on the freeway in 3rd gear the little 7875 will spool so fast on the 6 liter it's silly. you can go from 50kPa to 110kPa by going from 15% TPS to 30% TPS

i'll keep an eye on it but looking at the logs I really don't see the lag in fueling everyone talks about

NicD

iTrader: (7)

It's not consistent and it varies by OS, sometimes it's fast and sometimes it lags a couple of seconds. The first time I saw it back in 2008 I thought something else was going on, the 2nd time I saw it I asked the HP Tuners guys about it and they confirmed BE ran in a much slower ring of code outside of the main loop (like PE uses) so I stopped using it. They only ever really meant it to be somewhat of a safety mechanism anyways and from what I remember from my conversations with them many years ago about it the engineer who introduced the BE code wished he didn't. This is no secret to anybody who has been doing this since they introduced the custom operating systems way back when.

MY_2K_Z

iTrader: (1)

I run PE and BE and have no issues at all, I'm also a 6.0 with 7875 so spool is instantaneous lol. I have my PE set at 30% and I mirrored both tables so maybe BE is slow I just don't noticed because my PE comes in so early? Idk but it works for my ****.

truckdoug

iTrader: (25)

That is exactly what I was told when I started learning to tune. Maybe the bigger p59 computer runs those calculations faster? Only time will tell, and if I rattle a piston to dust it's not without many warnings from experienced guys such as yourself.

I'll probably turn it off at the track to be safe.

truckdoug

iTrader: (25)

so i'm just bumping this up to share some of the stuff I learned the last few days. I'm now using the BE table to fuel boost areas at low throttle angle/high load areas but i think this stuff can apply to those using only the PE table, either NA or boosted.

1) consider having your PE TPS enable table a slope rather than a single number across the board. this will allow smoother transition to PE in higher rpm and load ranges.

2) enrichment ramp in. I have seen this pegged out at 4 in some tunes that I copied as a new tuner. Or zeroed out completely! This creates a fuel dump. 1 is very close to most engines' change in fueling needs. between 1 and 1.5 is the safe zone.

I think it is some sort of timer, but the steps are not 1:1 ratio. I'm not sure on this. If anyone knows, please share!


3) enable torque. This is another delay/limiter for entering PE mode. if set at 100% your calculated desired torque must be higher to enable PE. I do not know where the desired torque number is taken from.

If you get actual knock at low throttle angles and high load like I was, try dropping this down to like 50%


please lay me out if my understanding is wrong on any of this. I just want to learn the correct use of all the tables and move away from my rudimentary band-aid tuning practices