2 bar tune for Turbo LT1 F-body possible with '93 ECM? DA3

[Skinny Pedal]

Map and baro come from the MAP.

Is your fuel pressure reg boost referenced? This will have a huge effect on VE table in boost. Scaling the VE for a 2 bar is not hard to start. Copy your 100 kpa to 50 kpa..... and so on. Leave 55 and up flat from the 100 column and bump it if you like, that depends on regulator.

[hotrodf1]

1 bar vs 2 bar MAP.jpg

Map and baro come from the MAP.

Is your fuel pressure reg boost referenced? This will have a huge effect on VE table in boost. Scaling the VE for a 2 bar is not hard to start. Copy your 100 kpa to 50 kpa..... and so on. Leave 55 and up flat from the 100 column and bump it if you like, that depends on regulator.

Yes, the FPR is the stock unit, and will be boost referenced, I believe, 1:1. I run in open loop, so I can use the open loop % fuel adder vs. MAP signal to add fuel "across the board" in addition to the VE tables. I have a wideband so tuning in boost area should be OK, just gotta sneak up on it.

I think I have the scaling figured out for the most part. Made a chart that tells the old vs . new MAP reading. It isn't actually 1:2 ratio which is interesting. But like you said 55 (2 bar) ends up being 100 (1 bar). 40 (1 bar) is 70 (2 bar). Attached a pic that shows my conversion table.

The thing that's the biggest question for me: what does the ECM do with the baro reading when you turn the key on? If it used to be 100 or so with the 1 bar sensor, now it's going to be 55 ish kPa with the 2 bar sensor. What's that going to do to the tune? Do I just need to find another table to scale somehow so that the computer still calculates the same results for fueling or what?

I don't have $EE so I don't have quite the same parameters list as that. The $DA3 isn't as well researched and pulled apart I think.

[Skinny Pedal]

The open loop fuel adder, IIRC, is the commanded open loop AFR. Can you post up the file you will be starting with?

[hotrodf1]

Yeah no prob. Modded bin, XDF, and stock bin JIC

The table I'm talking about isn't commanded AFR I don't believe. I think it just adds fuel on top of the VE table, of course only when in open loop. Sort of a PE mode, without going into PE mode. I have that disabled too. Maybe I shouldn't?

The 2 bar MAP came in today. Guess I'm going to see if she'll run NA with the 2 bar MAP.

Still not sure what to do about the Baro update deal. Maybe it won't even matter.BDLD 93 Z28 M6 R34 2 BAR MAP.binDA3.xdf

[hotrodf1]

Hmm, didn't attache like I thought

[Xnke]

Hope you don't have a 4L60E in there.

The reason you can't do this with the 2-bar map isn't fueling. It's that EVERYTHING in the trans code relies and absolutely needs that 1 bar map sensor, or you're gonna have to re-code all the transmission line pressure and shift timing sections. On top of that, you have to overcome the barometric update issue-I have the same issue with the P66 code in the 94/95 V6 computers. I have to run with the barometric update completely disabled, and had to create a new MAP sensor conversion to report accurate pressure, and then create an emulated 1 bar MAP value to pass off to the transmission code. I'm still (two years later) working out the last few bugs of JUST the emulated 1bar MAP sensor, and the small group that started the project had to work in an extremely tight code limit.

The 2-bar sensor does use the same 0-5v range, but it uses a different linear equation to convert from a 0-255 value to the 8-200kpA value. You'll need to find the ADC sample code, hijack the ADC code's output and run it through your new equation, fork if greater than 100kpA so you can set a flag that tells the PCM you're in boost, use the boost tables, and then unset the flag when you drop under 100kpA. At the same time, create an emulated MAP value to send to the T-side of the pcm to allow transmission controls to function, and keep some of the other stuff (air conditioning) working properly. Then, you'll need to create a second set of VE and Spark timing tables to use when the 100kpA flag is set. Then, you'll need to deal with things like the EGR, purge solenoid, baro update, MAP sensor fail mode, etc all still work...even if you are not using them, the PCM code is there and it WILL try to use them. This can cause MAJOR issues, especially the EGR and Baro update problems. EGR will change your spark timing and targeted AFR, and if you were to get a baro update (which will happen immediately upon hitting 100kpA) it would reset the baro pressure to 100kpA, altering your base fuel and your boosted fuel maps.

There is a lot more than just halving/shifting tables around.

[Skinny Pedal]

First post shows LT1/T56 swapped. If purge, egr and other things never run how would they cause issues? This is also the early LT1 ecm.

On the flip side to all this, all the other ones that have been done were all manual trans and have been going strong for years now.