LT1 and Boost

[freshda9]

My friend recently purchased a 97 Camaro with mildly built lower end. HE is wanting to turbo the LT1 and have me tune it. I notice with TunerCats their is no extended boost tables for 2 or 3 bar so is SD tuning completely off the table? Could i install a 3 bar and set PE to trigger before building boost?

Another option, could we substitute to a new GM style maf such as the slot maf and re scale the table somehow? Sorry im not very knowledgeable of the older ecms.

[steveo]

i did one recently, obd-i with both a maf and sd tune. the maf tune worked better.

i was fairly happy with the results considering it was my first try tuning boost with that ecm, but there were still subtle driveability problems. probably due to pressure-related functions that haven't been mapped out yet in EE. but it is being driven daily right now and he's happy.

if you install a 2 bar map on an ecm designed to read a 1 bar map, it'll produce half the output.

first, you need to disable atmospheric pressure updating somehow, otherwise it'll think your car is falling from the sky. i really hope obd-ii tunercat you can do that, otherwise you're kinda screwed.

then, anything that deals with MAP KPA needs to be cut in half.

in logs, it'll read 50kpa at 100kpa.

if you specify a constant as 50kpa, it'll actually mean 100kpa. so if you're thinking 'engage power enrichment at 80kpa', set it to 40.

if you write a timing table, your 50kpa column will be 100kpa. 100kpa in that table will actually mean 2 bar pressure (just under 30 pounds of boost). you can totally map out VE and timing in boost if you do the conversion. off boost will be the first half of the table, on boost will be the second half

with a 3 bar map your tables are cut by 1/3rd, but on a 'mildly built lower end' i doubt he's pushing that much boost, the loss of resolution would be huge.

you can tune speed density but maf will probably be easier. it'll be a bit hacky but you can make it work. you should do a rough baseline in SD even if you run maf.

[steveo]

Another option, could we substitute to a new GM style maf such as the slot maf and re scale the table somehow? Sorry im not very knowledgeable of the older ecms.

sure you can but the stock maf (between the air filter and the turbo) seems to work just fine once you change the curve of the maf table a bit.

[mecanicman]

100kpa in that table will actually mean 2 bar pressure (just under 30 pounds of boost).

You mean just under 15 psi, 3 bar would be just under 30.

[roughneck427]

http://www.camaroz28.com/forums/computer-diagnostics-tuning-36/2-bar-stock-pcm-speed-density-tune-6psi-forced-induction-560089/

[freshda9]

i was fairly happy with the results considering it was my first try tuning boost with that ecm, but there were still subtle driveability problems. probably due to pressure-related functions that haven't been mapped out yet in EE. but it is being driven daily right now and he's happy.

if you install a 2 bar map on an ecm designed to read a 1 bar map, it'll produce half the output.

first, you need to disable atmospheric pressure updating somehow, otherwise it'll think your car is falling from the sky. i really hope obd-ii tunercat you can do that, otherwise you're kinda screwed.

then, anything that deals with MAP KPA needs to be cut in half.

in logs, it'll read 50kpa at 100kpa.

if you specify a constant as 50kpa, it'll actually mean 100kpa. so if you're thinking 'engage power enrichment at 80kpa', set it to 40.


Do i physically scale the the axis or do i assume when installing the map these kpa values are now cut in half? I completely understand that i will be using 1 VE and it is scaled to 100kpa as im veiwing and of course adding a 2 bar will now make 50kpa actually be atmospheric. It does suck this way since you lose the resolution.


sure you can but the stock maf (between the air filter and the turbo) seems to work just fine once you change the curve of the maf table a bit.
IS the stock Maf limited to say 10psi max? I knwo the early ls1 mafs peg very quickly and i would assume these would also?


You mean just under 15 psi, 3 bar would be just under 30.
3bar is = to 44psi absolute or 29.3psi gauge. He means the KPA is scalled to 2bar which 100kpa would now be 2 bar and 50kpa would be 1 bar or atmospheric. Also 3bar = 300kpa


http://www.camaroz28.com/forums/computer-diagnostics-tuning-36/2-bar-stock-pcm-speed-density-tune-6psi-forced-induction-560089/
Thank you i skimmed threw as its a long thread. found a converter to convert the file from .LT1 to .Bin but I need to convert it to a Cal file to open it.

[steveo]

IS the stock Maf limited to say 10psi max? I knwo the early ls1 mafs peg very quickly and i would assume these would also?

this maf doesn't really know what pressure is. it's only some wires, and only really measures airflow at near atmospheric pressure. that's why i'd pull through the maf and not push boost into it. the stock lt1 maf will max out or start behaving strangely somewhere just above 450afgs as far as i know, but i've never taken it that high. i dont think with a mild turbo build the MAF is going to be a limitation. the one i was tuning never exceeded 10 psi or so, and it certainly didn't have any problems.

Thank you i skimmed threw as its a long thread. found a converter to convert the file from .LT1 to .Bin but I need to convert it to a Cal file to open it. [/QUOTE]

i doubt that is going to happen for you, that file is likely for OBD-I (EE) ecm. it's different. either way you should do it manually, im sure there's nothing special in that file, you just have to find every table and constant that uses MAP, and there aren't even that many.

[Montecarlodrag]

My friend recently purchased a 97 Camaro with mildly built lower end. HE is wanting to turbo the LT1 and have me tune it. I notice with TunerCats their is no extended boost tables for 2 or 3 bar so is SD tuning completely off the table? Could i install a 3 bar and set PE to trigger before building boost?

Another option, could we substitute to a new GM style maf such as the slot maf and re scale the table somehow? Sorry im not very knowledgeable of the older ecms.
The easiest way is to get a 95 OBD-1 PCM and swap it, it's very straightforward.
Once the OBD1 pcm is installed, you need to buy Tunercats OBD-1 and the $EE definition. Ask for the 2 Bar EE definition, it comes free with the purchase of the standard $EE but you need to ask for it.
Buy a 2 Bar MAP sensor, plug it and start tuning.

If you need to keep the OBD2 computer, it can be done but it's a lot of work. You first need to scale the tune, you may need to double-scale (airflow/MAP/Fuel).
If the VE tables can go higher than 100 you only need to scale the MAP. If they don't, you need to also scale airflow (half the injector flowrate and half the entire VE table).
Once you have scaled VE tables fix the spark tables. Be very careful with the spark advance tables, if you don't fix them you'll get too much advance.

The third and fastest way to do it is by using only Power-Enrich for boost, no 2 Bar MAP. Tune the VE tables as usual, the use PE for enrichment. This is not very accurate and has to be adjusted every time you up the boost, however it works.

The MAF will need to be disabled with any method. It will peg very fast and the fueling will be difficult. Even if you change it for a slot MAF the frequency will still be limited to the same Hz. Unless you use a very big pipe to lower the readings, a slot MAF will not help.

[freshda9]

Thank you for the replies very informative. I would like to keep the car obd2 as i like the logging better with HP tuners vs using Datamaster for the obd1 GM ecms.


The third and fastest way to do it is by using only Power-Enrich for boost, no 2 Bar MAP. Tune the VE tables as usual, the use PE for enrichment. This is not very accurate and has to be adjusted every time you up the boost, however it works.

The MAF will need to be disabled with any method. It will peg very fast and the fueling will be difficult. Even if you change it for a slot MAF the frequency will still be limited to the same Hz. Unless you use a very big pipe to lower the readings, a slot MAF will not help.

Sounds Like keeping the resolution with the 1 bar and PE for boost would be the best solution then. I wasnt sure if i had to have a 2bar or if i could get a way with a 1 bar.

[lionelhutz]

HPTuners supports the 97 LT1 PCM/engine?

Tunerpro does a decent job logging the 95 LT1 PCM.

[Montecarlodrag]

Thank you for the replies very informative. I would like to keep the car obd2 as i like the logging better with HP tuners vs using Datamaster for the obd1 GM ecms.

Sounds Like keeping the resolution with the 1 bar and PE for boost would be the best solution then. I wasnt sure if i had to have a 2bar or if i could get a way with a 1 bar.
HPTuners is not going to help you much, I have tried and only SAE PIDS are available in the scanner. It can be done but doesn't offer any advantage over other scanners.

You can use a 2 Bar MAP with the OBD-2 computer. If you properly scale the tune you can have a very good fuel and spark control for up to 15 psi of boost. You can't have that kind of control with PE and 1 BAR MAP.
Scaling is a lot of work, but once you finish the car will behave very good.


HPTuners supports the 97 LT1 PCM/engine?

Tunerpro does a decent job logging the 95 LT1 PCM.
Only scanner, basic SAE PIDs.
I find datamaster better than Tunerpro