PCM Options for Supercharged 454 / 4L80E

[EagleMark]

So if you tweak the adx for datalogging... you could tune it correctly! No changes needed in xdf or 2 bar conversion. Then the vehicle could be scan tooled anywhere as stock! Scan tool would not notice VE or spark tables were changed. Unless they drove and recorded/compared data to compare spark curve may be differant. But the owner should have told them by then it is differant. But he is safe on road to get repairs at any shop if a code light comes on or sensor goes bad etc...

So in adx 100kpa (usually 4.5 to 4.8 volts) get's changed to 140 and then work down however you choose. Like 70 becomes the old 100. Only you and your adx would know what goes in cells on bin by useing the adx table. Bin and xdf look stock but are tuned correctly to 140kpa

No that won't work because everthing from 100kpa to 140kpa would still be in last column, 5 volt..., but it could still work with 2 bar becaue it works with vacuum and positive pressure and changing adx ! Last couple rows of that chart you take out of equation because my suburban MAP is 4.45 volt at 94.14 key on engine off, may be because I'm at 2000 feet elevation. But slipping in a 2 bar and a reworked adx would give you data you need at boost. Split the other cells down to 20 map or where your bin goes down to. So that takes out first few rows of chart. Now if you look at chart with out first 2 rows and last 2 rows it's pretty close to same amount of cells to tune in bin. If the ADX is like many in increments kpa by 5 at lower load then by 10 at higher load and your only loosing a couple readings as far as how many cells Only you would know what cell to tune in bin from adx chart!

[gregs78cam]

I actually thought about trying this out a year or so ago. And aside from losing a little bit of resolution in the timing, and VE tables I think it should work.

[dave w]

Mark,
I think your getting the idea of how a .bin could be re-calibrated for 2 BAR MAP with a range of 20 Kpa ~ 140 Kpa. The 2 BAR MAP will more than likely produce voltages from about 0.02 ~ 3.50 Volts. Positive PSI (Boost) voltages will start at about 2.50 Volts. The Timing and VE Tables are going to be divided by Voltage vs. RPM. The data logs I have now, will be used to construct a baseline / comparision for the 2 BAR MAP Voltages vs. RPM.

What I really dislike about this PCM is with a Supercharger, the Vacuum Tune will be based on voltages from 0.02 ~ 2.5 volts which is half the voltage range (0 ~ 5 volts) that is currently used for 0 ~ 100 Kpa. The Boost Tune will be voltages from 2.50 ~ 3.50 volts starting at 100 Kpa ending at 140 Kpa.

For VE the '7060 has 12 cells, so the 2 BAR MAP would split the 3.50 volts by 12 cells. For Timing the ' 7060 has 15 cells, so the 2 BAR MAP would split the 3.50 volts by 15 cells.

If anyone is interested, the Excel spreadsheet I posted earlier has the data sorted by KPA / RPM with 0 ~ 5 volt readings; so it would be possible to make a 2 BAR MAP baseline of their own.

dave w

[dave w]

So I was thinking about GM vehicles with superchargers and maybe some of the supercharged vehicles used a MAP? What I'm wondering is if the MAP sensor for OEM superchargers are calibrated 0 ~ 5 volts / 0 ~ 150 Kpa instead of 0 ~ 208 Kpa? I can't find any tech info on GM part # 12580698, 12580698, or 12615136. It would be nice to get some better resolution for a 2 BAR MAP Conversion.

dave w

[Six_Shooter]

ALL GM MAP sensors that I have seen work on a 0-5V range.

1 BAR - 0 to 100 KPA
2 BAR - 0 to 200 KPA
3 BAR - 0 to 300 KPA
(high figures are rounded)

You would have to use a non GM MAP sensor to get other ranges, like 1.5 BAR or 2.5 BAR MAP sensors to get more resolution, but being able to see that little bit of positive intake pressure. You would have to investigate the transfer function of each to make sure they will read correctly.

My concern with using a 2 BAR MAP in place of a 1 BAR MAP is the key on BARO settings, this is where I wish I knew more about the actual programming language to account for that, I have a few codes that I'd like to add 2 BAR support to.

[1project2many]

Today's constant technology improvements make it seem like you need more/faster/better to get any job done. It's very easy to lose perspective. A 10,000 lb+ truck using an engine with a fairly mild configuration is not demanding high resolution tables, extremely fast processor speeds, or a large amount of concern over the ecm's inability to be a new, modern controller. Here are some considerations:

1) All GM vehicles using a Delco 2 BAR sensor at least until the introduction of the Ecotec 2.0 S/C engine used a 5V signal. This signal is sent to an 8 bit A/D converter and even some of the the newer, faster processors used an 8 bit a/d converter. It is the converter, not the sensor voltage range, which ultimately determines the resolution available from the sensor.

2) The turbo Sunbird, GMC Syclone, and Turbo Grand Prix all used less than the full range of the MAP sensor from the OEM. All can all be tuned extremely well using this sensor given enough time. One individual I know rewrote the code in his TGP to accurately calculate air usage and fuel requirements within 1% using the OEM MAP.

3) The 6.5 turbo diesel engine commonly used in trucks in the 90's and up to 2002 in vans typically runs less than 8 psi with the 2 BAR MAP. This 68HC11 equipped pcm controls transmission, boost, injection pump timing, and fuel volume in GM's first big "drive by wire" application.

4) My 2.2 powered Cavalier turbo was the worst combination of parts, just to prove a point. Too small turbo, non-intercooled, over 9:1 compression, 87 octane fueled, manual transmission, massive injectors. My wife (who drives like a granny) used that car daily for several years without troubles. From the driver's seat it seemed 100% like an OEM vehicle except that it had a bunch of extra power. It even got better than stock mileage as long as you stayed out of boost.

5) My Sunbird is running 17 psi using a 3 BAR sensor, same 8 bit resolution A/D, same OE spark and fuel tables (re-scaled of course) and a manual transmission. That car is so driveable that no one I've loaned it to wants to give it back. This despite the naysayers who claim switching from 2 BAR to 3 BAR will cause driveabliity due to lost resolution.

6) My friend's Sunbird is over 24 psi now using the same 3 BAR sensor. I was able to tune it to be mild in town and extremely driveable even though the entire combination started as an untamed ride that would break tires free at the smallest throttle increases. It's so driveable in fact that the owner has asked me if I can but some of the agressiveness back so it's like the cars he had in the '70s. What a challenge... build a tune to mimic "Snotrod."

6) The _only_ times that I've had a need for more than OE ability was in vehicles with rapid engine response and cams having large overlap. And this is when trying to make them extremely mild and driveable around town then behave like monsters if asked. OE calibrations don't do well with rapid decel / rapid accel transitions, especially in the AE area. Time and again that's become a hurdle I've had to work around, generally de-tuning the car slightly to make up for lack of capability to get AE right. If there were anywhere I'd ask for a bunch of resolution, it's AE.

[gregs78cam]

I agree, the loss of resolution should not make much of a difference because the RPM will change faster than the Kpa, in the lower gears and the PCMs ability to interpolate between cells chould make up for a lot. Also AE and PE should be able to cover up a lot of the left over inaccuracy.

[1project2many]

BARO readings are taken at key on, engine off. Many cals will update BARO when in WOT for a period of time when temp and other conditions are right. Skipping BARO update at WOT is generally a fairly easy matter.

FWIW $58 / $59 turbo code has poor support for BARO. GM decided there is no appropriate time to read BARO from the MAP when the engine is running so they used a calculated BARO update based on the stock engine / vehicle configuration and the KOEO BARO reading. If the base vehicle configuration is altered in any way the BARO updates are no longer correct. Additionally, the BARO readings at KOEO are not updated if crank voltage is not within a specific window leading to a default BARO reading being used. One method I've thought of to provide BARO updates with a turbo calibration is to use TPS, boost, rpm and rate of change, and the filtered vs current MAP values. For a given turbo engine, turbo contribution will be minimum below a specific rpm. If WOT exists for a certain time, engine rpm is below the threshold, rpm is increasing less than a specific amount, and filtered MAP matches current MAP, then use the current MAP to update BARO. Correctly implemented this limits BARO to occuring when turbo contribution is zero. Of course the easier way from a code standpoint is to simply poll a dedicated BARO sensor if you have a spare 5V input.

Hmm.... maybe a binary output used to briefly switch the MAP signal line to a BARO sensor is a practical solution. Instead of waiting until WOT simply watch for TPS below max value and TPS change to be near zero for a set time. Switch signal to BARO, get reading, switch back. If any TPS is detected immediately switch signal to MAP and exit routine.

[gregs78cam]

I was going to add the part about wiring in a second MAP for Baro, and then write the code to check that sensor when in DFCO, because there would be real need for the MAP reading at that time.

[dave w]

The vehicle owner has accepted delivery of his vehicle after a very comprehensive test drive. The vehicle owner is very satisfied with the tune. The vehicle owner declined all upgrade options that were exchanged in this tread.

I'd like to thank everyone for the input provided on the options to better tune this vehicle. I hope that the knowledge shared within this tread is a benefit to all.

dave w

[EagleMark]

Glad he's happy!

I thought this was a very interesting topic and learned a lot!

[1project2many]

To turn a phrase,

If it drives good, it is good.

Maybe the next guy will spring for the whole shebang.

[TravisMartin]

I'm always willing to share the information from a tune, unless otherwise requested not to.

dave w

How did this turn out? I'm brand new here, and to EFI mods, and have a project underway that would benefit from your experience. I'm putting a '95 TBI 454/4L80E into my '78 C10 shorty. I'm confident I can handle the hardware and wiring end, but not so much on tuning. I'll start with the stock '95 tune to sort out the conversion, but I have a Whipple kit waiting in the wings that I'd like to add to the mix, so I could sure use some pointers. How did the customer's dually turn out?

Thanks!

Travis

[dave w]

How did this turn out? I'm brand new here, and to EFI mods, and have a project underway that would benefit from your experience. I'm putting a '95 TBI 454/4L80E into my '78 C10 shorty. I'm confident I can handle the hardware and wiring end, but not so much on tuning. I'll start with the stock '95 tune to sort out the conversion, but I have a Whipple kit waiting in the wings that I'd like to add to the mix, so I could sure use some pointers. How did the customer's dually turn out?

Thanks!

Travis

The Dually owner only contacted me once after accepting delivery, he was selling the Dually without the supercharger and wanted a stock chip.

Hindsight being 20/20, I would recommend using a Dynamic EFI system for boost: http://www.dynamicefi.com/EBL_Choice.php

dave w