i dont understand this table how you view it, can some one explain
how to look at it . like draw a line thru were your at at wot...

 

Oh yeah...been down this road a few times. My car is running an Open Loop SD tune, but yes, I guess my comment was a bit more directed to an open loop version, as the O2 sensors can correct as they see fit (or as was the case on my car, die a slow, agonizing death, nearly taking my engine with it).

As far as the charge temp bias vs. airflow table, I won't even begin to assume I understand what's going on there.

 

If you look at mine, WOT puts me in the 100 kPa region, and then you'd follow the RPMs as they rose (hence why my table maxes out at 4800 RPMs - peak torque).

 

So if you want your car to run a little richer you would increase the VE in that region..?

Or is there a different way to do that?

 

That's the general idea...the higher the VE value, the more fuel it adds.

My VE table is set up for 14.68:1 in the idle, part throttle, cruise areas, and I run about 12.2:1 up to 4800 RPMs and lean it out to 13.0:1 for the rest of WOT.

 

how long have you been doing this man. you sound like you no
what the f--k your talking about , train me man ............

 

I dont know.. it sounds kinda dumb becase your "tricking" the PCM to think your getting more air than you actually are.. if you want richer, opposite for leaner

So your VE is not actually your VE (thats whats confusing me). In this method, if you want a rich mixture you can potentialy get a 100%+ VE which is completely false in the definition of VE (unless you have built race engine)

 

your not tricking it. your giving it the correct values so that your o2's dont have to over or under compensate.

 

The idea is to get the ve table correct so you always have 14.7:1 in closed loop without relying on fuel trims. Or if you're running an open loop tune like Meents, to get the ve values correct so that the fuel/air multiplier values in your open loop table match the actual air/fuel ratio you see on your wideband. There is no tricking of the pcm into a different a/f ratio using the ve table, although you could do it that way in open loop if you wanted to for some reason.

Side note: I believe megasquirt works that way, by using the ve table to manipulate a/f ratio since it doesn't have a seperate desired a/f multiplier table. I think.

 

Another side note: some people inflate the ve tables in regions where they see "lean spikes" when they stab the throttle. The idea is that the overly high ve value offsets the lag in the maf reading so your pcm is tricked into the right a/f ratio. Think of an accelerator pump on a carb.

 

Im sorry to highjack this thread but is there a separate fuel trim multiplier?

It makes perfect sense to have the 14.7 table and then have a multiplier on top of that for individual trimming of each point. Is this how it is done?

Also, is there a table for acceleration enrichment?, i.e. rapid change in TPS reading and quick RPM increase... How much lag is there in the system? If you accelerate from 1000-6000rpm in 1 second as opposed to 5 seconds your going to need to almost predict the point ahead of where your at.

 

Fuel trim multiplier? No. There is an open loop fuel air multiplier table and a power enrichment table. If you're not in open loop (cold start, power enrichment, etc) the pcm will command 14.7. If you don't like that, maybe an open loop tune is for you.

As for acceleration enrichment, i don't think the stock programming does that, but i could be wrong there. There is an accel enrich tab in hptuners but I think that is only used with their speed density enhanced operating system, which their website says has a ve modifier based on tps.

 

Don't think of it as tricking, think of it as a table that was calibrated to give the proper fueling with the stock intake and exhaust system. If you have changed those, the calibration will be a bit out of whack. That's the beauty of a MAF sensor, as it actually "measures" the incoming air mass (but it still looks this value up from a table, but in a much different format than the VE table). This also brings up the shortcomings of SD tuning...anytime you make a modification that alters the airflow into or out of the engine, you have to retune your car.

Also, the VE table values aren't exactly a percentage as I understand them, as they can (and sometimes do) take on values greater than 100, even in N/A applications. If you'll look at my table, you'll see that my car peaks at 4800 RPMs with a value damn near 100, but the car is stock internals, so that right there should tell you that this isn't simply a percentage value.

 

And if what I said above confuses you, you should also know that the VE table is referenced to differing degrees during regular operation, even when you have a MAF. The MAF can't keep up with unsteady throttle transients, so the VE table is there as a sort of "crutch" so that it can look up fueling values for when it knows the MAF simply isn't accurate.

And as I stated a disadvantage to SD tuning, there is also a disadvantage to MAF tuning. MAF sensors have a flaw, and that is that they measure the airflow no matter which way the air is going through it. People that run big cams know this all to well as a rough idle (more commonly referred to as lope). This is a sign of reversion, as some of the exhaust is coming back through the intake tract during the normal operation of the engine (mainly only seen at low RPM operation).

That's why you'll see people with big cams running SD tunes, as you don't have to deal with the reversion of a big cam. Chad (Black02SS on here) runs a fairly sizeable cam (Futral F-13), and his idle is really quite nice. He also knows what he's doing when he's tuning his car (he runs an open loop SD tune, and is the reason I run one too).

If you want to see just how much exhaust reversion affects your car, check into the Harrop 8-TB intake setup. Since your plenum is essentially the atmosphere, there really is no reversion. There's a video clip floating around on here with a stock cube 346 LS1 running some ungodly cam (huge duration on a 106 lsa) that idles pretty nice.

Just some food for thought...

 

What im trying to learn is SD tuning, up and downs of open and closed loop.

Here is what im gathering so far..
Open loop = runs directly off VE table.. nothing else (for fuel that is)
Closed loop= runs off VE table and modifies VE table to achieve 14.7 at ALL times.

Im trying to find the value that commands or modifys the PCM from sending 14.7 afr to the desired AFR. Is the only place this can be modified the VE table? So you look at your AFR and adjust your VE table according to that? And thats all the control you have?

Yeah, for transients i would think Acceleration enrichment is a MUST! For pure drage racers its not as big of a deal.. but for those that modulate the throttle i think its invaluable.

And yes, the CAM change is the reason i would like to change to either Closed or Open loop SD

 

open loop uses the OLFA (open loop fuel adder) table to determine the a/f. you tell it and it uses it. im not 100% how the ve tables affect this because im not running in OL.

 

Yes and no...don't forget there is the Open Loop Fuel/Air table that is referenced as well, and you'll still have Power Enrichment as well. The OLFA table is very important, as that will now become your commanded A/F ratio at different MAP values (in open loop - closed loop always commands stoich regardless of the OLFA table). So you can make your cruise/idle/part throttle/WOT any A/F ratio you want (in open loop), and tune your VE table with a wideband to match. Since there isn't a great deal of resolution with the OLFA table (as in, it doesn't reference engine RPMs), it isn't as robust as it could be. That's where the PE table comes in, as you now have control over your WOT fueling vs. RPM (and you can set when it enters this mode so you can be completely safe).

The one thing you have to watch out for is that your VE table will vary based off of your commanded A/F ratio when tuning in open loop. i.e. If you tune your VE table to a 13.0 A/F ratio across the board, your VE table would look different than if you tuned it to stoich across the board. This has something to do with some back calculations that the PCM performs based on the commanded A/F ratio. That's why I'll always recommend that you tune your car like you drive it (as in don't disable PE mode, etc when you are tuning it).

As for closed loop operation, it doesn't really modify the VE table. It just uses the fuel trims as decided upon by the O2 sensors, which aren't terribly accurate with headers (and why I don't use them at all on my car).

Don't forget, there are also spark adjustments to be made, and they will affect your final A/F ratio as seen by the wideband O2 sensor downstream. So you basically have to get your fueling in order first, then mess around with spark, then readjust your fueling to match the new spark tables. For heavy throttle transients, you also have to deal with Burst KR, which can become quite confusing.

I think my head is gonna explode...

 

Thanks!

That helps. I know what i want its just a matter of learning how to use the program to achieve it.

Is there a write up that just has a few sentence explanation of each table.. I can figure it out from there..

Also, i am definately leaning towards Open Loop unless i can wire in a Wideband to accurately simulate a narrowband... and if that would help... If not, when tuning you connect the LC-1 to the HP module and just tune from there?

 

I really don't see a need to simulate a narrowband sensor with the wideband. What I do when open loop speed density tuning is try to make the wideband air fuel histogram values match the values in the open loop f/a table. I have my open loop f/a table so it's 14.7:1 at low map values and it smoothly transitions to 13:1 by 80 kpa. Using an excel spreadsheet i can calculate what percent my wideband a/f is off from the OLFA table in each cell. That percentage is applied directly to the ve table.

If you want a writeup of each table, the hptuners help menu is pretty good for that.

 

Why would you have it scale to 13:1 by 80kpa? Why not just make the entire table 14.7. If your worried about PE, just make it only enable at 80kpa.