jchevy

When you tune the timing you use a map pressure and rpm. If you know you have 100 kpa at 3000 rpm set for 25* and datamaster is showing 28*.


Technically should be comanding 25*

LT1-TA

Yeah. In my tune i was commanding 24* and datamaster shown as much as 27* with 5* pulled from knock. I set it to 15* commanded and now am gettin 16* (on logs).

There must be another table (hidden?) somewhere that is adding this extra timing.

dookie454

I finally made a few WOT runs. Mine does not appear to lock at 26 degrees like some others. I've heard timing is usually off a few from request and datamaster reported.. dont know if it's something demanding the timing increase or if it's the way Datamaster reports it.

To test, my file is set for 20 degrees total timing and 100%TPS at 4400rpm timing is at 23degrees and climbes to 24degrees at 5200rpm and stays at 24 all the way to 6100rpm where I have rev limit set.

There is a hystresis somehere (hidden likely) because my RPM is a bit flucuating around 5200rpm so the first timing step from 23-24 does show up around 5250 at first then the rpm drops back to 5100rpm for a second but timing stays at 24degrees..

Im sure there's a bunch of hidden tables we dont know about so wondering if they vary from year or manual/auto flash. Mine is an original 1995 6 speed flash.

Hope this helps!

jchevy

I noticed that same hiccup in the rpm. Ill have to go back and look, but I think it happened at 5100. Dont think I looked at the timing though, its when i was trying to get the fuel straightened out.

dookie454

Ok, I'm starting to think timing may be linked to MAP.. increasing MAP means increasing Timing?

Can you guys with this timing problem confirm your running a 2 bar MAP and tune? ACtually it wouldnt matter because a 1bar tune would max at 100kpa which (if it's linked to MAP) then could be what is giving you 26 degrees... makes sense.

I'm only at 70-72kpa /5225rpm when I get the jump... could even be MAP+RPM, or MAP or RPM connected. Right now it seems people with higher boost are seeing higher timing, or people with a 1bar which maxes at 100kpa quick. You could pull off your intake tube and go WOT and see what happens to timing with 0 boost.

If there is a connection and we described it very good we could get TUnercats or LT1 Edit to search the code and come up with a new table!

jchevy

Next time my tuning laptop is booted up i will look at some of my old logs.

Im pretty sure I have my timing set to 25* but I am actually seeing 29* on datamaster by 6000 rpm.

I still havent bought my 2 bar map. I am 1 bar, speed density, open loop for now.

dookie454

yea, I see higher than requested timing as well but it does go lower than 26.

dookie454

I ran another WOT run with even lower timing than in the first table.

First run I set timing to 20 in ALL wot tables, and results:
4400rpm at 23 degrees,
5200rpm at 24 degrees
6100rpm at 24 degrees where I have rev limit set.

Second run I set timing to 15 in ALL wot tables, and results:
4400-5000rpm at 18 degrees,
5000-5800rpm at 20-22 degrees
5700-5900 22-23 degrees where I have rev limit set.

So, still.. it is lower but seems to be increasing.. need to change or remove boost to determine if it's MAP related.

EDIT -
I just realized my min spark advance in this test above was stock at 15@4800, 17@5200, 18@5600, 19@6000+... to this explains the reason why 15 and 20 timing settings end up close to the same timing above...

dookie454

1982z28with18s, you should be able to tell us if it's MAP related since you run variable psi depending what gear your in. Run your 2 bar tune @ WOT through the gears, let us know if each gear gives the same timing retard at say 4000, 4500, 5000, 5500, and 6000 rpm. If it does give the same timing in all gears regardless of pressure then the MAP theory is out the door and it could be linked to RPM.

BTW you might want to enter 15 degrees in all the WOT tables just to make it easier to see what's happening.

1982z28with18s

I've had it set at 8 degrees before, still got 26 degrees at all rpm's anywhere from 4lbs up to 14lbs, always the same 26 degrees of timing.

I did put the 1 bar tune back in it yesterday and got exactly 16 degrees like it is supposed to be.

dookie454

In previous posts you mentioned trying the stock 1 bar and timing was still not right. You must have a corrupt LT1 file.

I had a file suddenly stop reporting speed... did everything.. finally reverted back to an old file and everything worked normal.

I suggest take that working 1 bar and transfer tables.. there's no reason timing should report differently unless the file is corrupt.

dookie454

Can you post a datamaster file for download? Id like to compare to mine. I can post mine if your interested. Your happenings are indeed strange.

What if I send you my lt1 file? is it anywhere near the same setup?


BTW, I went all the way down to 15 for timing and was getting 18-23 reported in datamaster. Far from what you are seeing (constant 26 degrees all the time in WOT).

Something is definately wrong with your file.

cause4panic

Could the iat vs timing tables be throwing you guys off? for some reason i remember that these tables were only avaliable in lt1edit and not tunercat. This could be that "hidden table" you guys were speaking of.

P.s. i started my turbo build this weekend. Im running 60 lb mototrons could anyone suggest a good constant to start with? i was thinking 20-25lb for my 2 bar sd. has anyone wired in their wideband analog output to both inputs for 02 sensors? vemaster needs o2 feedback to work am i correct? my thinking was why not use the wideband for both o2's and assume the motor should be fueled the same for each bank.

1982z28with18s

I was wondering if lt1edit had a iat timing table as I don't believe tunercats does. Can anybody confirm this?

cause4panic

A friend of mine has lt1edit he said the table was there. So im gonna open my tune in lt1edit. Zero the table out, then proceed using tunercat.

but this wont happen for a few weeks. So could someone else confirm? Anyone wanna talk to tunercat to see if he can enable the table? I will shoot him an email anyway.

If this solves the problem of not getting exactly what is commanded in the timing tables can i get a cookie?