The 700r4 in my 5.7L 91 Z28 is getting near it's last few legs. I'm considering a T56 swap, and the answer to this question will be immensely helpful...

I've read/heard about the issues with idle after the torque convertor and auto tranny dissapear.

I'm wondering if this could be solved as simply as putting in a 91 Vette chip, since they did have the L98 backed by a 6spd?

Or is it more difficult than this, can someone point me in the right direction if so? oh - the 5.7L in my z28 is bone stock...

thanks,
nick

 

That's what I did, I'm currently using ARFP software downloaded from diy-efi.org with some tuning to accomodate my engine mods.

The idle snaps right down to the preset speed (750rpm) when I let off the gas and coast, whereas it was kinda "floaty" with the AUJP binary I originally tried. Kept staying at 1200rpm until I came to a complete stop.

I'm using a Dakota Digital VSS translator also. The ECM absolutely has to see a reasonably-accurate VSS signal to function correctly.

 

So then, since I have a stock L98 in my '91 Z, is it safe to say that the vette chip would work just fine without any alterations - just plug it in and drive?? or am i still looking at tuning issues.

I ask this because I am not equipped to do the work necessary to get a custom prom/memcal right. I've been reading the DIY EFI and GM ECM lists for months now, and I have a pretty good idea of what is required.. and I'm just not equipped or ready to do this yet. So if the vette chip is not something I can just plug in and drive (with no issues), then the t56 is out of my league for now.

Thanks!!

nick

 

You're probably gonna have to tweak a few things. The F-body L98 was "tuned down" from the 'vette's L98, not to mention the tuning differences for the exhaust, transmission, aluminum heads, etc. that the 'vettes had and f-bods didn't.

 

If you run an SD Vette Bin, you will need to address the oil temp SES code as the 7730 does not support an oil temp sensor.

 

Here are the mods I made to the stock ARFP.bin to make it work in my Z28:

With a hex editor, I changed location L0824C from E6 to 60. This masks off the bits that manage the high/low oil temp errors.

Then, using TunerCat, I changed the following:

Cylinder volume: 727.412 (it's a 355ci)
Inital spark advance: 10 (I run 10deg BTDC initial)
Min temp for highway fuel: 154degF
Min temp for highway spark: 154degF
Min VSS for highway mode: 55mph
Min RPM for highway mode: 1500rpm
Hot O2 closed loop delay timer: 60sec (I'm running an un-heated O2 sensor, need more time to get hot)
EGR duty cycle: 0 in all cells (I have no EGR valve or exhaust passages)
Fan 1 on temp: 180degF
Fan 2 on temp: 185degF
Fan 1 off temp: 175degF
Fan 2 off temp: 180degF
Fan disable mph 35
Closed loop enable temp: 140degF (again accomodating the unheated O2 sensor)
VATS off
VATS diag off
EGR diag off
Fuel cutoff rpm: 6500 (rev limiter)
Fuel enable rpm: 6400 (rev limiter)
Idle rpm vs. coolant temp: curved higher to accomodate the LT4-HOT cam, ending at 750rpm at op temp.
VE tables: lotsa tweaking
PE spark advance: lotsa tweaking
PE fuel table: lotsa tweaking

My tuning setup consists of a used laptop, Andrew Mattei ALDL cable, Craig Moates' ALDL software ($20 donation), MS Excel for ALDL capture display and sorting, TunerCat, Atmel 29C256 EEPROMs, and an Intronics pocket programmer. Total cost is about what you'd spend buying a TPIS Stage 20 or whatever chip...under $400 if you shop around on the laptop.

 

So, trying to understand here....

the AUJP had idle problems, whereas ARFP had none? I assume that's because the ARFP was already a stick BIN, from a vette? and that's why you had to do lotsa tweaking to the tables?

Would the BIN from a 5.0 camaro 5spd....Would they have the same "mask" (I think that's the proper term) as my stock BIN, so that I could theoretically dump my stock tables into a 5.0 5spd BIN, and thus have a "sticK" version of my BIN?

I already have a notebook (ok, ok, it's a 386sx20) but it runs diacom plus just fine (which i also have already). I am guessing at some point I will have to take the plunge, I already know that I want to change the fan turn on points to something a little more reasonable... i don't understand yet what I have to do with the memcal (?) so that i can swap chips out of it.... still learning.

nick

 

I described AUJP's kinda annoying idle weirdness in my earlier post. ARFP was a manual trans bin and I found the idle behavior was much better, also described above.

I had to tune the spark and VE tables because my engine has had a lot of modifications. Specs are in the link in my sig.

Don't have any info on Speed Density 305 bins, I never had need to dig into them. At a minimum you'll have to change cylinder volume and injector flow rate to make a 305 bin drive a 350...so don't let fear of PROM burning drive you in that direction.

Dig around in the tech boards here and find the PROM burning article, your questions about how to swap chips and whatnot are covered there.

 

Well, After doing a bit more research and edumacation, I have a few more questions.

I've looked more closely at the ARFP bin and the AUJP bin. It seems they are quite similiar - same $8D mask, same (essentially) ECM, etc. That's all good...

The ARFP uses the oil temp sensor thingy, which can be masked (at least from what I can tell in WinBIN). that's good...

the ARFP has different calibrations for the differences in the vette, but since all the data is of the same layout (same mask), ... what would I end up with if I took the ARFP bin, copied over all of the spark/fuel/misc calibrations from AUJP into the ARFP? Would it be a reasonably complete conversion from auto to stick? Or is there more stuff going on in the prom than what i can hack with winbin (or tunercat, if need be...)?

I've already resigned myself to the fact that at some point I'll be burning chips (don't like the absurdly high turn on point for the fan). No big deal, I burned chips in college for 8051 eval boards, but that was for code that *I* wrote. If I can get to the point that I feel confident that I can make a t56 conversion work, and work right, I'm going to convert. otherwise, a pro-built 700r4 is in my future because my auto is worn out and slipping under WOT. Basically I'm trying not to make a $2000 conversion mistake.

thanks!
nick