LS1LT1 Forum banner

1 - 7 of 7 Posts

1,052 Posts
Discussion Starter · #1 ·
Does lt1 edit save files as binary .bin file named to the extension .lt1 or are .lt1 files proprietary to the Lt1 edi software? 20+ years ago used to calculate conversion from hex to decimal to binary but not going to this time. Is there a freeware conversion software that reads LT1 edit and converts to bin files or can you rename the filename.LT1 to filename.bin. I am trying to learn some tuning differences by going to progressively larger cams the changes to make.

Old school carbs timing lights and vacume guage used to set the intial timing to as much advance w/o making hard to start hot backed off a couple degrees then play with springs and weights along with the vacume canister to dial in the advance curve. Then larger the cam higher the idle speed to provide more vacume reduced by greater overlap(F{>duration,<lsa}) Then re dial in air fuel mixture screws with vacume guage then jet or metering rod primaries and fuel metering block, jets, metering rods, secondary springs (how soon to open 2ndarys), then tweak accelerator pump squirter nozzle sizes and accelerator pump cams. Now its all done on computer knew the job at New Mexico State University business computer lab would be useful someday.

Tuning for larger cams Slightly raise idle rpm then have to change idle air control and throttle position sensor. I have one tune in bin form I studied mainly the Advance v RPM v MAP tables as my 93 runs only ODB1 speed density with chip but able to datalog. Have 94-95 tunes to represent hotcam to CC503 to near CC306. Hotcam tune is in bin format others are LT1 edit.
93 interpolates air flow from MAP Kpa and Air intake temperature sensor no MAF. Also learned that at high altitude at WOT the 95 100 Kpa table are never reached to carry over the values to the 80 85 90 Kpa region while maintaining same values for 95 100 Kps should driving be done at lower altitudes.

Encountered a timing debate one theory says the LT1 makes the best power between 34-36deg advance and that mystery timing of additional 2-5deg somehow gets added in. Stock table runs 100Kpa 2krpm 30deg to 6krpm 38 deg. One of the best old school tuners runs from 29 to 35k advanced at 100 Kpa. Other say run until it pings and back off 4 deg. problem with this is load temp changes and variables can make this theory ping pulling timing or causing engine damage. With added compression I like the 1st theory and
want WOT 34deg 2800-3800 35 deg 3800-4800 and 36 deg 4800-5800 then 6000 6500 7000 back to 34 deg. Slightly adding timing advance due to faster rpm then decreasing after or near power band peak. All at a level detonation friendly with 87-91 octane and greater than stock compression. Each Kpa represents different load vacume levels during part throttle an idle the timing map must represent the altitude and camshaft vacume signal to the MAP. At part throttle where load and detonation not so prevalent more advance dialed in to say 40-41deg for better mpg and throttle response.

Timing tables advance map must meet altitude, idle, rpm cruise WOT, gear ratio and camshaft characteristics.

Fuel trims can be changed as % for each cylinder. What is the main table
that determines air fuel ratio for the engine vs Kpa and rpm ?

Is there a formula to calculate injector constants? how does that change when going to larger lbs/hr injectors?

Does someone have a good link to tuning Injectors for Dummies? 22 to 24 to 30lb hr injectors what changes?

1,052 Posts
Discussion Starter · #2 · (Edited)
Found one site with some information on Tunerpro

Great tutorial on using Tunerpro for Odb1 94-95 Z28!-New-users-this-is-a-must-read!-)

Basic concepts of tuning for a larger cam

Setting up a bin for modified engine.

93Z28 Camaro is the only year Camaro that uses a Chip for tune if you create your own tune you cannot flash it onto ECU. Must program a chip or have a tuner make a tune on a chip then you need the following adapter to run it with your stock memcal(gmECU Chip).

1,052 Posts
Discussion Starter · #3 ·
Found some of what I was looking for. Called TuneConv Changes LT1 edit to Tunercats and Datapro bin formats.


Found some tunes to play with comparing exported to text files. Jet Chip Stage 2 sucks.
compared to professional tune. Some people copy the timing tables from the Jet Stage 2 and tweak a few other items others add too much timing.

Using generic LT1 Edit tunes with Tuner CATS

Spreadsheats MS Excel to calculate open loop commanded air fuel ratio and
power enrichment air fuel ratio.


1,298 Posts
Viper , long post .... can't answer all, and may start a discussion.. will start with the easy one's first. Disclaimer I don not have '93 definitions, so I'm answering from '94-95 data, therefore tables may be different on not existent on the '93 ECM.
Q: Fuel trims can be changed as % for each cylinder. What is the main table
that determines air fuel ratio for the engine vs Kpa and rpm ?
A; Individual cyl trim multiplier tables are good for idle and off idle settings. And the off idle settings are determined by the constant setting 'Individual cyl trim disable TPS%' setting it's set at TPS=14.8% stock.
To change AFR across the board there is a pair of tables on the '94 that are used. First is 'CL mode Vs airflow', which your '93 can't have as it's based on air flow. Then the second table is called ' Fast O2 rich lean (Mv) threshold Vs CL mode" The values in the last table are O2 voltages that signal stoich (14.7 AFR using gasoline) to the PCM. Lowering the voltage leans out the AFR and upping the voltage does the opposite. An accurate reading WB s/b used when changing them as the voltage varies by model and setup. If you ever get into fine tuning discussion, relocation of O2's further or closer distance from heat source and amount of flow will change the voltages. Altering rich/lean tables s/b reserved for the skill tuner.
Q: Tuning for larger cams.
A: I started at idle observing MAP and tuned for the highest vacuum/ lowest KPA an smoothest running. . Jacked up closed loop timing 400-1200 ranges till going higher made no more of a difference and settled on 34*, then played with TB stop screw opening and closing to see if it effected BLM's / MAP/ running, no big difference so I set it to 0.65 Volts and IAC's ended up around 40. BLM's were equal but on rich side so I tweaked Individual cyl trims to get them close to 128 on each bank. Next I started crusing tuning foe the cam power curve.. including smoothing out the transition from TPS closed timing to entering the main timing table. A data log is a good tool. Print out the main and extended tables for your tune. Then start a log from sitting at idle (foot off throttle), then start accelerate normally to 55 MPH as you would during street driving. From that log go back and circle each cell of the main and extended tables as you pass through them in each gear. Connect circles with line to show the complete run. Then analyze your timing from entering the table to high gear. Check entering for and big jumps from closed throttle to first cell you hit in main is big gap alter to smooth the transition. With a cam you will see your operational curve has shifted towards the right of a stock setup as you Kpa is higher. The circled and surrounding cells are where you want to concentrate on timing alterations. Now go look at the BLM cells you used during the run to make sure you are utilizing as many cells as possible (gives ECM more granularity). With a cam yu are running higher Kpa and RPM so the lower 0-4 BLM cells may never be used with a stock tune. Tuning timing w/o a dyno is difficult as you really can't tell when increasing does not provide any additional power gains. The old school increase till it knocks, then back off will get you to highest timing you can run, but it's probably more than you need. If you run at the strip it can also tell you where timing increases are no longer helping.
Q: injector offsets
A: if you find something please post it up, my eyes are burning from reading some pretty complex posts. Would be nice to see a clear setup for 30# injectors for our cars.

1,052 Posts
Discussion Starter · #5 · (Edited)
I learned alot from looking at other tunes 94-95 odb1 my 93 is different but mostly the concepts are the same. I guess what I am doing to learn is reverse engineering professional tunes and commercial to the stock tune. I collected a range of tunes from stock to bolt-ons, hotcam, CC305, crower version of the CC503, heads and cam cc306, 2 tunes on 383's, one 396 tune, non knocking tune, emmissions tune etc. Had to convert some tunes from LT1 edit to bin's like Tunercat and Datapro. Then Loaded the 94-5 Mask and then the bins. Then I exported the tunes to text files so I could compare them easier.

The 93 interpolates MAP v speed v IAT instead of the MAF on the 94-95 so I concentrated on the following tables :

Kpa v RPM V Advance and Kpa V RPM v Volumetric Efficiency.

I've learned that most professional tunes start at the stock tables: some end there, others adjust a few values, some copied the Jet Stage 2 tables, Some copied LT4 tables and tweaked a few values,, only 2 or 3 of the tunes remapped the entire timing and volumetric efficiency tables the way I would from what I've read and seen. Each tuner has shortcuts to acheive a tune and some have deficiencies.


In all cases even the copycat tunes are better than commercial chips. Some even lose power with the commercial chips. The commercial tunes didn't even adjust cooling fans for tempuratures even though recommending 180 tstats.

In reading temps less than 180 make more power but the engine wears quicker, above 180 say 190-192 degrees water condensation burns off better gas mpg is better and emmisions are reduced.

There is a table similar to knock retard that reduces power in the engine due to excessively higher tempuratures.

The stock timing tables are already stout for 350 1-2 degrees from detonation or timing retard at WOT. Cruise speeds can use tweaking for better mileage and driveability.

Most cases detuning is needed when running higher compression this is more evident if knock sensors are detuned. 350 The LT4 is a good model for higher compression modded engines. Very few mod the 30Kpa stock idle tables to the 50-55Kpa tables used in idle with lower vacume due to overlap of larger cams. Very few pull the 95-100Kpa tables down to the 80-85Kpa values used at High altitudes and also tweak the 90-100Kpa values to run good if traveling to lower altitude areas or racetracks.

With mods the stock tune is too rich for good mpg in idle and cruise and too lean for best power and detonation resistance.

I found one tune that trouble shooting would drive ya up a wall the fuel cutoff was programed normal in 1st gear and 2-6 fuel cuttoff rev limiter rpm was 396 rpm.

Which ever road people take buy tune, buy a chip, or tune your own its a good idea to log the thing which is all I could do on the 93. To make a tune for the 93 you'd start with a good known tune that is mild and all around balanced MPG and Performance and tweak it slightly to a conservative tune as its on a performance chip. The VE and Timing tables interpolate values calculated by the map and maf on 94-95 so the tables must be right or very close to stock. Maybe not dyno optimal but safe and useable. Learned about tune it until it knocks then back a few. Detonation on higher compression with stock timing table invoke timing retard to less power levels than before the compression increase. So reducing the timing somewhat eg Lt1 100Kpa timing as high as 37-38 deg at higher rpm's the LT4 timing is at 35 deg at those rpm it has close to 11:1 larger cam and heads where the Lt1 has 10.4:1 can make for a safer smoother performing engine that runs better and doesn't pull timing. If on a dragstip tune for the track a must and with a 93 Z28 a Moates Ostrich is the only way to do this.

Read the following articles

This article states 34deg best idle temp (coolest, highest vacume) not the best for emmisions though hotter better with larger cams. The
LT4 has some wide open throttle WOT advance interestingly at 33.5 deg and some top tunners only dial in 34 35 36 Deg advance then say mystery timing is added (2-5deg) this theory with high compression makes sense as 40-44deg with 6-11 retard makes less power than 35 +3deg mystery advance.

Analysis of Idle Spark Advance Variation

LT1 PCM Tuning - Tips & Tricks for DIY Tuning!

Another thing to note some tuners effectively remove rev limiter Old school by setting it to 7500RPM.

Also they dial in max advance for power at an rpm that could guarantee and engine builder a new shortblock instead of the RPM where the cam is supposed to make peak power then slowly reduce 1-2 degrees to ward off grenade at above optimal RPM's.
I think this is why some dyno peaks are above cams peak power rpm's.

VE Maps for cams mine is mild like hotcam the stock VE tables are overly optimistic to begin with some just reduce efficiency at the lower end. Cam shifts power to higher RPM so lower RPM less efficient Upper RPM more efficient. I tweaked the VE tables in a experimental learning tune to reduce 1% all values at all Kpa 400-2000RPM at 30-55 Kpa new idle due to mild cam, then 2000-2800RPM resembles stock cam so I used the stock values, then 80-100Kpa 2800-4000RPM I added 1% to all values, 4500-6000RPM added 2% to the optimistic values.

Some other tunes changed the values to as high as 99% volumetric efficiency in normally aspirated engine I felt this too optimistic.

I am learning and will be able to work better with a tuner to make my tune.

One other question why do some change the injector settings to 24.9lbs for 24lb injectors?

Is the only thing changing injectors to change the constant lbs hr then the voltage offsets?

1,052 Posts
Discussion Starter · #6 · (Edited)
Answered some more of my own questions last night and your right this post is getting as long as a sinkhole is around in circumference.

This is backwards

Left side throttle closed right side throttle open

Rpm increasing downward on left side 2000-7000RPM Top Kpa rising from 20-100
Vacume for a stock lt1 is 30Kpa adding a mild cam increases idle Kpa to 50 or so due to less vacume
from more overlap (due to tighter lsa and >duration).

Full throttle low vacume associated with 95-100Kpa

Upper left Throttle closed High vacume low rpm low Kpa IDLE
Bottom Right Throttle open low vacume high Kpa high rpm WOT
Top right Throttle open low rpm low vacume high Kpa BOG
Bottom Left Throttle Closed High Rpm high Vacume Low Kpa COAST

launch off idle stock begins at 400rpm30Kpa Travels Down to the right in the advance table to destination Rpm 100KPA 6500RPM advance cell.
1 - 7 of 7 Posts