Finally starting to make some good progress now too. Its quite a big thing when you look into it.

I thought some of you might find it interesting to read some of my opinions based on my findings from doing abit of learning, asking a few questions here and there, and trying different settings over and over til i decide what really suits best.

When i first got my 94 it was running on a stock factory tune, wayyy too rich at idle, it would quite regularly peg out at 108 and run rough as guts. The last few days ive gotten back into it and in just the last 2 or 3 days ive managed to get it to idle quite well, which was the hardest part of it all really.

The engine being as moddified as it is, it shouldve been tuned properly at the time.

Here is a list of what i know is in there: (and some of these i wouldnt really bother with if i was doing all this myself, most of this was done for me before i bought the car, however some of it quite poorly and i had to fix alot of it)
*EGR and AIR are present, but decomissioned (and EGR was setting a DTC every few months)
*After market cam, specs unknown, idle vacuum is around 52 KPa and power comes on real strong abit after 3,000rpm, (doesnt drop off one bit all the way to 6,000rpm where i have set rev limiter)
*Crane Gold 1.6:1 roller rockers
*Crane double springs
*Ported heads
*Stock throttle body bored over
*MAF bored over
*Tri-Y long tube headers
*High flow cats
*Straight through mufflers
*Etc etc etc etc....

Ive had the PCM in speed density mode the last couple weeks so i can make the VE tables as good as i can get them, they are pretty tidy now after abit of work. Will put it back to MAF when im totally happy with the VE tables and do some work on the MAF tables....

Running on a stock tune it was still more powerful than a stock engine, but it was nothing compared to what it is now. It was picking up alot of knock with the stock spark tables at higher MAP levels,

There is far more involved then just adjusting the timing and the VE/MAF tables though.

Ive managed to reduce a serious split BLM issue at idle and part throttle from as much as 10 different all the way down to 1 and ocationally 2, although mostly even, by adjusting the squential injection correction tables (which is what was causing the split BLMs in the first place) It seems as though the bigger cam and other mods has made the idle air distribution abit more even, probably due to the reduced intake velocity at idle and lower rpm.

Ive also made some changes to the DFCO, cause with the bigger cam and reduction in vacuum, the stock DFCO settings are not as easily reached, so is harder to activate.

Transmission shift points play a bigger part with a modded engine too, the stock shift points on the 4L60-Es are set so that if almost requires full throttle to shift it back a gear, and at lower speeds this is rediculous, cause most of the time coming from 3rd gear id end up in first, and on the highway, putting the boot into it wouldnt kick it back to 3rd cause of the factory settings, yet abit more throttle and youre back to 2nd at 75mph...

With all that i found the shifting up was happening too early for the modded engine, and was an extremely abrupt surge of power when it did shift back until i lowered so numbers to better suit my engine power range and my driving style.

Someday I hope to understand what you just said!

You gotta love it when you figure out stuff like that and make forward progress. Good on ya! :thumbright:

There is a great book out there, called "Corvette Fuel Injection and Electronic Ignition: 1982-2001," by Charles Probst. It's a great primer on how this works.

My only thought... if you can make the EGR work, it will help... it does one thing via another thing (follow that logic :thumbright: ).

The EGR helps lower NOx emissions. That's what it does... but it does it by introducing a touch of exhaust back into the combustion chamber. This, in effect, cools the charge. The other thing it does is lowers the chance of detonation.

The transmission is turned for MPG (which, by extention means emissions). Mess with it too much and your economy will go right out the window!!! I know gas is pricy in Oz, so you might want to go easy there... but I see your point.

Very interesting stuff! Have you found a dyno to test it on?

Happy to hear you are getting good at this Case, any idea what it takes to burn a chip for my 93? Perhaps I'll buy you the toys mate if I can get a free tune.......

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I agree - almost everything I know about my L98 is from reading and re-reading this book.

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I havent seen that book over here anywhere, but ive heard its reasonably good

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Not possible, cause most of the stuff is missing. I wouldnt hook it back up even if i could though, the cam has more than enough overlap to take care of EGR.

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But the tuning is totally unsuitable for a modded engine, and it will actually use more fuel due to labouring in a higher gear. I have the shift points set low enough at lower TPS%s, but ive smoothed out the tables alot (which from the factory, look like a dog's breakfast) Trying to push a higher gear takes more effort, which takes more throttle, and more fuel. Ive managed to improve the "around town" fuel economy by setting the trans up to select the right gear for the given situation, and based on my engine's characteristics. When cruising slowly, i have it setup to select the highest gear it can push without labouring.

As an example, if im cruising along at 60kph and want to accelerate to 75kph, factory settings would hold it in forth until my foot was near the floor, and it would labour its arse off and accelerate like a slug, and if i pushed my foot down far enough to make it shift down, i would get such a sudden rush of power and the car would take off like a rocket when i didnt want it to do so.

I will dig up some pictures of shift tables and post them up for ya to look at so you can see what ive done with them, i have a stock .bin file here and i think it has it's stock shift points on it (although i know they are scaled down for a ratio change)

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No mate i havent been able to yet, i know of a few around, but havent had a chance. Ive been running Data Master most days lately though and i take notice of everything that is going on there, especially in relation to what effects my changes have made. Fuel isnt cheap over here, not much more then there, but its not a real big deal, the car is quite economical really considering the power its got. I certainly want to enjoy the car my way though, and sometimes ecomomy just has to take a number and stand in line!!

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Im not sure what is required for doing the new chip on your 93, ive never looked into that, but the available settings and adjustables are all pretty simular. I have TunerCat allready, all i need for your car is the ECM definition file.

You need to get an ALDL cable for that car!! Ill have to see if i have enough bits here to make you one up, i think i remember you telling me you have a spare desktop computer there, even though you cant take that with you out on the road to do some logging (unless you start it all up and run it from a big UPS!! ), youll be able to set that up out in your shed and try the cable out until you get a suitable laptop.

ok...

Cam is good for over lap, check.

The tranny is a strange bird on those things, I will agree. The thing is, tho, that if throttle position could be a little more independant of fuel needs, the more open throttle would equate to lower pumping losses. Theoretically, that would equate to better MPG. But that's in theory.

I fully appreciate the need for better tractibility, especially with a modifed car. No question at all.

You don't need a gas pedal that acts like a light switch... the usually means WRECK!!

Oh, and the 1993 PROM is not updatable like the 1994 and later models. You have to literally burn the chip with a new tune.

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Indeed mate, its got loads of it there
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Fueling doesnt work that way though, its on a table of RPM Vs MAP KPa, throttle position sensor has nothing really to do with it until it reaches the preset level for Power Enrichment. As soon as you put your foot down abit more, with little or no increase in RPM, the MAP will rise straight away
Quote:And mate you shouldve seen just how right you are about the light switch bit, cause it was just like that with the stock settings!! You could push the pedal down 70% and it would labour along in 4th, not being able to do anything serious cause it doesnt have any power down that low in the revs, but then you get to 80% and you instantly go back to 2nd and all hell breaks loose. Even worse at lower speeds when it could get into first gear.

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Yep, we know that

Ok here are some pics:

First up ill show some shift tables from various .bin files ive got here:
The first ones i have are from a 3.07:1 car, not 100% certain if they are stock settings or not, but they are not far off if they have been changed]http://i11.photobucket.com/albums/a185/Casethecorvetteman/Tuning/shifts.jpg[/img]

This is more what it looked like after id done some changes, all numbers in [color=red]red[/color:a8728d4bc2] are the ones i changed]http://i11.photobucket.com/albums/a185/Casethecorvetteman/Tuning/raysshiftchange1-1.jpg[/img]

These were my shift points from a while back (3.33:1 rear end):


Youll notice by looking at the graphs in the last 2 that the shift points are far more consistant and make alot better use of the PCM's ability, and i can say from experience the car is alot better/more efficient/smoother/quicker/easier and more exciting to drive.

Here is the settings for rear end ratio and rear tire size changes:

Here is a few fan temp settings as well as a couple other items,



The Coolant thresh for TPS for WOT (HIGH TEMP) relates to power enrichment mode, there are 2 tables for that, 1 table for all coolant temps up to the setting in the constant, and another table for any coolant temp over the setting.

Here is where it activates WOT, once it reaches those TPS%s, it is in power enrichment:

Here is all the items that can be set:



ECM Switch and ECM Constants have loads more adjustables

Here is the Volumetric Efficiency tables:


And the Sequential injection individual cylinder adjustments:


There is a setting in ECM Constants that controls what TPS% the off idle table is no longer used, factory setting is 12.9%, once the TPS exceeds that, all cylinders are considered equal, with the exception of left and right banks still being controlled by their respective BLM corrections.