Colonel Klink

Hey,

A rebuilt L98 is going to replace the L69 in my 91 WS6 5-speed. (I'm going with an L98 because I'm hoping it will be simple to get the tune in good order.) I have been reading the archives and I'm planning on starting with AXXD with some SAUJP tables, and also with AXCN with reduced timing. I'll see what runs better and go from there.

Then I found the bin 90L98MAN8D.BIN on the diy-efi site:
ftp://ftp.diy-efi.org/pub/gmecm/bin_...%205.0%205.7s/

Does anyone know what the story on this bin is? Has anyone used it?

Thanks a lot for any help!

JPrevost

Looks like something somebody came up with... so who knows. Obviously the L98 never came with a manual trans but you can find out what the starting bin was by doing a compare within TunerPro. Using compare you can see if the code is different or similar. The compare bin with the least amount of differences is usually the original.
Then again, the person that made it might not have changed the prom id.... that would be really easy.

kdrolt

FWIW, C4 Corvettes (1985-1991) with L98 had either a manual trans or an automatic. Try the Vette sites, C4 specific, for more info. HTH.

91L98Z28

Getting an L98 up and running in front of a manual is not that bad, I've done it, and it was my first diversion from a "stock" setup.

My opinion would be to start with a 305 5spd bin (AXXD is what I used). Change the injector constant and cylinder size, and you're 50% of the way there. With just those two changes, the car will be drivable, and safe to drive (you won't be hurting the motor or anything). On the flip side, it won't be "right" - you'll need to tweak on a few areas such as AE and IAC follower to get everything nice. I also found that playing with the idle speed error timing tables helped to give a smoother light throttle launch (bring in timing a bit more agressively on low RPM error) and brining up the idle RPM's a bit (I believe I"m using 800 right now).

But assuming you have a basically stock L98 + T5, just running AXXD with the correct injector constant and cylinder size will get you plenty close enough to start doing fine tuning.

Grumpy

That's how I labeled some .bins *years* ago. 10 years ago, .bin files were alot harder to come by, and at times when someone donated a .bin, the full/complete history of it was just unknown.

JPrevost

91L98Z28, I don't agree with starting with a manual 305 bin and massaging it into a manual 350 bin. The VE and the spark tables are slightly different between auto and manual versions of the same motor but are drastically different when the motors don't match. I always consider the motor the number one influence for a starting bin. The VE tables will much closer and the spark will require minimal changes.
Look at the differences for yourself. I speak from experience. I've tuned enough 350 TPI manuals and all have had better experience starting with an auto 350 TPI bin. With a little bit of work it's setup for a manual trans and the VE is a lot closer. The 305 TPI VE looks nothing like that of the 350.
BUT... to each his own. Whatever works better for you because it really comes down to what you've got experience with. Then comes the comfort level. I wasn't at all comfortable with MAF and the 165 until I started helping tune some. The $8D was a breeze coming from the TBI speed density tunes but the MAF was a little fuzzy. Still to this day I like tuning speed density more but there are people that like the MAF and it's simplicity, both can be made to work similarly.
I'm suprised you got the AXXD to work on a 350 TPI without touching the VE and spark tables! Engine damage can occure since both the ve and spark are different in different area's of the tune. Granted if your knock sensor is working very little damage would actually occure but if you're using a 305 memcal on a 350 even that could be damaging the engine (knock filters on memcal are tuned to the engines cyclinder bore more than anything else).

JPrevost

Yeah, isn't information and history useful (note, no testy attitude implied). I started a history of the 8746 TBI bins and I'm now starting to do the same for the 165 and 730 ecm's. I think it would helpful to those looking to start DIY tuning.

91L98Z28

I suppose I could add some additional information and clarify what I've done.

I'm using an AUJP memcal with the 350, so all the knock filter stuff etc. is still "correct" for my 350.

When I mentioned that running AXXD with a corrected injector constant and cyl size, would get you 50% there, that's based on two things - my personal experience, and the fact that many folks drop 350's in their 305 bodies with even less changes than that and drive it for years or even decades with NO problems (this seems quite common, for example, on the 305 monte carlo SS's from the 80's). On the other hand - that only gets you 50% of the way there! Practically no table in my calibration is left "stock" - and certainly not VE or timing. That's the remaining tweaking I referred to. I certainly do not advocate taking ANY mask, resetting the cyl size and inj constant and calling it "done". It's good enough to get the car home, and get ya to work for a week if need be (assuming an otherwise stock setup), but it's certainly not done. There is still 50% drivability improvements to be had to make it drive and feel "right". I'll readily admit that. The first chip I burned was rather a pain to drive because the AE was all off. A manual trans with a 2.66 1st gear definitely responds differently than an auto with 3.0x 1st gear and a loose converter in the mix.

When I burnt the first chip or two for my T56 swap, I actually did use almost all the AUJP tables into an AXXD. It ran reasonably well, but the timing was no more correct than the AXXD tables (I'll admit that my pre-tuned AUJP VE tables were closer). I found that reverting to several of the AXXD tables (primarily AE related stuff) made drivability a bit better, because they were more geared for manual trans driving, but still not correct. Then, I compared 305/A4 to 305/M5 cals, to see what differences a "same" engine would need between slushbox and stick, and that gave me a few ideas as well and I was able to make a few more changes that worked.

In the end, I gave up on trying to make it look something like GM had already released, and started tuning by feel and what the car responded to (where have we heard this before?) and I was met with the best success. In the end, my timing/VE/other tables do not directly resemble any existing GM cal, but they work on my car. I can spend an hour driving up in the hills of the bay area with perfect finesse and manners (you dare not upset the owners of these expensive homes, lol) as smooth as can be, then hit the freeway onramp, stomp the pedal and the power is <i>right there, right now</I>. You just aren't going to get that kind of drivability by swapping the injector constant and the cyl size. that's the other 50% of drivability still left on the table that you have to tune to find.

One example: I have 3.23 gears, and with a 2.66 1st in the t56, I don't have a great deal of torque multiplication for light throttle acceleration (I'd be better off with 3.42 or 3.73). I found that the 4* timing jump between 600 and 800rpm in the stock AUJP table was difficult to deal with - if you rev'd up to about 900, let the clutch out, and the engine fell back to about 600-650, you'd lose about 5* of timing, have to give it some more throttle, then the RPM would climb back up a few hundred AND you'd gain some timing, so you'd have to let off the gas a bit, and well... it made for un-smooth drivability. I started revving to 1400-1800 or so and slipping the clutch just to avoid it when in town/light throttle acceleration. To solve it, I ended up massaging the SA 600-1000 range to flatten out most of this range a bit, and drivability was much better. I also changed the idle speed error SA tables so that I'd gain SA a bit more aggressively due to low idle speed error, which further made it easier to regulate engine rpm in light throttle starts. I probably went through 5-10 chips just to get this narrow window of operating range to a point that I was happy with and resulted in truly "nice" drivability.

So I guess the point being - my opinion is that the VE/spark/everything else tables from AXXD, AUJP, whatever - will not be "correct" for a 350/manual setup. I think that they are all close enough to make the car drivable so you can start fine tuning, but in the end the "final" tune (there is no such thing, but lets call the "final" tune as the point where you're generally happy with overall drivability) will not resemble the cal you started with because neither one is right.

My reason for going with AXXD is because there was generally confusion (from my perspective, at that time - a few years ago) on whether or not AUJP could be made into a manual bin correctly and successfully. Knowing that the art of tuning was much better understood, I went with AXXD to get a BIN set up for a manual car and all the manual specific stuff would be right, and figured I could tune for the rest. Which is what I've done. I figured it was no different than a 305/5spd guy who rebuild the motor and dropped in a 350.

hope that clears a few things up.

Colonel Klink

I used both AXXD and AXCN, each with their own AE values, and both with AUJP VE and SA, and mostly SAUJP other info. I disabled EGR so I took 3 deg timing out of the AUJP SA table everywhere, just to be on the safe side.

I'm doing this remotely, now, as I'm at school and the car is home with my family. I was told that the AXXD-based chip is running the car all right, while the AXCN-based chip had the car idling incredibly rich and running rough. (I did initially change all of the O2 voltage switch points in AXCN to the AXXD/AUJP values.)

It looks like the AXXD/AUJP chip is the starting point, then. However, I was told that at WOT, the motor starts to fall off by 3500 rpm. To the best of my knowledge, it is a rebuilt stock L98, with the exception that it has my old intake with siamesed plenum, upper runners (smooth transitions ground out of the flange for the runners).

I'll put the 3 deg back in and see what that does. However, I'm thinking about just going to SAUJP SA and making initial changes that make sense for a manual, such as what 91L98Z28 discussed.

Not sure whether to put more fuel into VE or PE, though.


Good info above--thanks.

91L98Z28

Several comments:

1) Given a basically stock L98, there is no real good reason (in my opinion) to disable EGR. EGR is just going to let you keep the combusion chamber cooler and maybe a bit better economy and let you deal with todays crappy gas. As long as all the EGR equipment is hooked up and in good working order, I suggest re-enabling it, unless you plan to remove it anyways and want to tune without it.

2) It sounds as if you've siamesed the lower intake, and from what I remember reading about this, it improves upper RPM airflow fairly significantly. i would advise no more WOT runs until you get things figured out - you could be running lean up top. What injectors are in it? If you're using SAUJP injector constants, I believe they are 22# for stock L98. But if you're running the same injectors in that intake as your old 305, then they are 19# injectors. And then if on top of that you're running a modified/siamesed intake that gives you more air higher up, but the VE table is not accomodating that, you could be running into a lean situation and thats' why it's falling off. Lean situations at WOT = BAD.

You need to start with the basics and see where you're at. What's the BLM with the car idling? Fuel pressure? Is the injector constant properly set for whatever injectors you're using?

Please note that, as I described above, I consider the injector constant/cylinder size a 50% fix - it would get you to work and back and move an otherwise stock car, but I am absolutely not advocating WOT runs with such a setup, especially since you are modified. You've got to do some data logging and see where you're at first. Tell the folks back home to take it easy on the car until you get this sorted out.

Get some data logs, post them, along with what settings you're using in the chip and what injectors you have etc.

Colonel Klink

No--no siamesed lower intake. I did that on the 305 a little while ago, but switched back to the stock lower. No, I siamesed the openings in the plenum. What I meant about the runners was just that I then cut into the flange, where the runners connect to the plenum, so that that area was smooth. (i.e., the siamesed plenum openings don't just see a flat flange wall in between runners.)
I have increased the VE values at high MAPs at RPM's above the stock AUJP peak. Apparently, I need to increase them more.

I disabled EGR because Traxion advised diabling EGR while doing VE changes.

The injectors are FRPP/SVO 24#; the injector constant is set to 26, based on someone-on-here's formula (maybe Glenn's).

No joke about the WOT stuff--I've already advised against it for now.

91L98Z28

Sounds like you have it under control!

let us know what you find.