So im thinking about running my car in SD mode (95 firehawk) to fine tune it for the most power.

Has anyone done this? Some things Im confused about:

The OBD1 computers dont use VE tables outside of SD mode right?

VEmaster wouldnt do much for my car because BLMs are completely confused due to alot of overlap (236/242 cam on H/C 383).

The car has a tune from Ion, so Ill prolly keep the spark tables alone, until I get the VE tables dead on. Then maybe a little more until it starts pulling timing.

Im getting a wideband, but what kinda AFR (at various RPMs) should I shoot for when tuning in part throttle with a 236/242 cam to adjust for valve overlap and should I just remove the O2s to keep them from screwing with BLMs.

Im assuming that VE tuning is more accurate than MAF tuning due to changing VE (not table, just true VE) of a 383 with decent heads and a rather big cam.

Any thoughts?

 

I believe MAF is considerably easier to tune.... less variables to deal with.

You still have BLM issues in SD mode. The only real difference between the 2 is that MAF uses the MAF sensor to read air flow where SD uses the combined data from several sensors to calculate air flow... in a perfect world you should end up with the same result using either method.

The only real way to tune SD mode is with VEmaster. I dont see any other way of accurately changing the VE table without VE master... anything else is more or less guess work in my opinion.

 

Well your car being an OBD2 car (unless you converted it) runs off both the VE and MAF tables.

I know the PCM uses BLMs in SD and MAF mode, but they would be confused at low RPM because of the overlap. A stock cam has virtually no overlap and can then shoot for perfect AFR completely off of O2 readings/BLMs. With a big cam, you have to tune it accordingly because when the cylinders are at perfect AFR, the O2s are still registering lean because of unburned oxygen leaving the cylinders before combustion.

So how does this sound?

Pull the MAF and run the car off SD mode until the BLMs get good and stable. Then run VEmaster until it gets the part throttle VE tables right. Repeat a couple times to fine tune it. Then strap the wideband up and do some finishing touches on the VE tables. Then tune for WOT on the wideband using VE and %AFR change @ WOT vs RPM.

Then: Strap the MAF back on and tune the MAF table to get it right with the wideband. Still unsure about what tables exactly effect MAF readings except the last ones about MAF readings hz vs g/min.

That way I would have SD for most days and when the weather goes south, I can put the MAF back on.

Any more thoughts?

 

well some people say that obd1 dont use ve tables (chris millard) so people say they do (joe overton). well i tried it. and it does work on obd1 cars with maf pluged in. and even with the maf pluged and in closed loop you can make you blms 12 8acroos the board using the ve tables.

there was a big disscusion on it one time and i tried it well scanned the car and found at what map i ran 70 mph at in sixth gear, so i went and changed the ve tables at that area and lower them 10 pionts (taking fuel out) and the blm soot up 7 piont from 126 to 133 and then i posted back and then they told me the blms would return to normal because the o2s. 2 weeks later they were still in the same spot and i drive 60 mile a day to work so i figured 600 mile and it should have made a coorection if it was giong to, and it never did. so as the car hit that spot the blms jump to 133 and all the other blms wer at 126 acrross the board.

so i changed them back to normal and added the 10 points back and then added another 10 to it so it should be 10 pioints less than where i started. well low and behold the blms droped in the same area by 7 and were reading 119. and stayed there for a week.

changed it back to where it was and its still at 126 where i started.

now will you benefit from i dont know but they do work hand in hand.

i dont know why people say its not for obd1 cars, its your main fueling table.

i took all my to a perfect 128 using the ve tables. and they have never moved back (corrected themselves)

try it for your self. but just make and copy of the bin file and make changes to it in case something goes wrong you can always go back and load the one you copied.

i spoke to joe overton about 2 weeks ago discusing tuning and he said that the ve tables are them main tables he uses when tuning customers cars.
good luck

 

maybe the computer uses VE tables to help calculate fuel in closed loop, but not in WOT PE mode.

 

Here's how it works w/ LS1 cars. At part throttle below 4000 rpm fueling is derived using a hybrid of sd/maf mix. Idle is almost entirely ve driven, but the higher the rpms are mostly maf with little ve influence. At 4000 rpm and up, the maf is the sole voice in fueling as long as its in a steady state position. On throttle transients, irregardless of rpm, the maf is disregarded and the ve table is referenced for fueling. GM designed it this way b/c the maf is "slow" to react to the sudden rush of incoming air that happens on throttle transients. So yes, the ve table plays a big part even with the maf hooked up. Tuning part throttle ve is pretty easy by running in sd mode and changing the ve to get proper fuel trims. After this, plug the maf back in and scale the maf to get the trims back to where they were in sd mode. You should find better throttle response and trims all -4 to 0. WOT fueling you'll still need a WB obviously.

 

there is alot of debate on what actually controlls fuel mixture, but Im thinking I might just run in SD mode and lock the idle mixtures using BLM controls and set BLM tables to start over 1500, because of the overlap in my cam causes confusion with the O2 sensors below that rpm. (Im running a 236/242 cam in my 383).

I am a little confused about open loop tuning. What maps does the computer access to control WOT mixtures with open loop. I believe it is just the VE and Open loop AFR tables w/o accessing the WOT tables, or am I mistaken? I know it makes it a little tougher to tune because WOT tables are so simple, but it would be more consistent right?

I also really dont trust O2 sensors and MAF sensors. They either mess up gas mileage or make the car surge when they start to foul, and mine never seem to work right.

Or I could ditch both the MAF and the O2s and run open loop SD. I will be getting a LM-1 soon to get the mixture right. I also have access to emmisions testing equiptment to get my spark right.

Are there any data logging programs that allow for wideband input as well as MAP sensor inputs?

 

Today I will scale my VE table down to "0" and see what happens. Then Ill scale them all to say "100" and see what affect that has. My guess is NOTHING will change. We shall see. I do know FOR A FACT if you mess with the MAF tables the affects are easily apparent looking at the BLM readings.

 

i was adjusting a buddys car last night and moved all the blms using ve tables.

 

Well I just did my experiment and found it made no difference.


However something worthy of noting I found is PE tables do not appear to be working in SD mode.... I have idle PE mode set and was running very rich in SD compared to MAF. To me that says some other table must be used but I could be wrong.

 

i know i dont have a freak pcm because thats three ive dont like that. i raised my friends blms 5 points last night

 

Well regardless if VE tables work in MAF mode...

Im interested in what controls WOT mixtures with SD open loop. ANybody know? Open loop AFR, PE, VE? I think its just VE and Open loop AFR tables, or maybe just VE... who knows?

Thanks

 

Again, I only know LS1 pcms.....but with them open loop SD WOT mixture is from ve and PE. Actually the pcm will use the richest of the two tables. Ex. If your open loop afr mulitplier is 1.12 and the PE is 1.15, the pcm will use the 1.15 setting from the PE table. The way to make sure your ve table is right is to check and see with if the commanded afr matches the wb reading and adjust as needed. With a perfect ve, your mixture will equal the commanded afr.