Doc99SS

iTrader: (2)

I have tried the advice that I received concerning my bucking problem. None of it helped. I have come to believe that with the overlap that I have (244/248/112LSA), tuning out the bucking is impossible in closed loop mode with a MAF tune. This was confirmed by Dan at Livernois. I am thinking that I must run the PCM in OLSD to help reduce the bucking which occurs from 1,000 to 2,000 RPM. But I want CL above 2,000 RPM. Can I set the MAF failure frequency of the MAF, for example, at 3,500Hz and force OLSD below 3,500Hz and normal operation above 3,500Hz?

Frost

iTrader: (45)

You can run CLSD and delay CL operation until 16-1800 RPMs (not too high, you wanna cruise in CL) by setting up PE to stoich at idle (1.0) and enabling it down there through TPS...

Doc99SS

iTrader: (2)

Thanks for the reply, Frost. The problem is that I typically cruise around 1400 to 1800RPM, but that is where the bucking is. So I am forced to pick a gear that gets me above 2000 RPM. I am not sure I understand what you are saying. I thought that I needed to have no corrections going on (keep fueling, timing ,etc. the same0 to elimenate bucking. I thought that OL would be my ticket. What am I missing here?

Frost

iTrader: (45)

most, though not all, bucking seems to come from too much airflow at low-to-no-throttle.

I was saying you can set the car up in SD and set it up to run OL up to a certain RPM with PE and then move to CL.

Post your file the way it is now though.

Doc99SS

iTrader: (2)

Please recall that I am using LS1-Edit to tune the car. I can send you the .Ls1 file for LS1-Edit, if that will work for you. Otherwise, please help me identify the tables that need fixing. How do I do the following?

"I was saying you can set the car up in SD and set it up to run OL up to a certain RPM with PE and then move to CL."

Frost

iTrader: (45)

I don't have any idea how you'd tune OLSD with edit unless you had a LOT of free time...

Sorry, I replied to your PM with my email address, but I don't have edit.

Try setting your throttle cracker table to 0 above 1,000RPMs, drive the car and see if it helps. If it does (and it most likely will) then you know that you have an airflow problem, not fueling.

hellbents10

iTrader: (10)

agreed, there is too much running airflow at low engine speeds. You can make the drive ability much better with that cam but it still will not loaf around at 1k like a stock cam no matter what.

Doc99SS

iTrader: (2)

I have taken alot of timing out at the low end, it did not help. I have reduced the throotle cracker table as you suggest to 0, it did not help. Well, maybe Dan at Livernois is correct,,, being in CL, you can not elimenate the bucking with a cam with that much overlap.

SSpdDmon

iTrader: (10)

Where was your timing at? Not only where, but how much fluctuation were you seeing?

Doc99SS

iTrader: (2)

From 0.08 to 0.32 gms/cyl and from 1200 to 2000 RPM, I have the timing set at 30*; this is much reduced from my factory LS1 timing. The data logs show no change in the timing as I cruise and the car bucks severely.

SSpdDmon

iTrader: (10)

Did you try going as low as 18*? Then, gradually increase at an increasing rate after 1400rpms?

The other thing you can do to help identify the right timing is to take control of the timing. I know in EFI Live, we have bi-directional controls where we can command a certain timing figure or alter the looked-up timing figure by a delta. Using those bi-di controls in an empty parking lot was very helpful for me.

Doc99SS

iTrader: (2)

SSpdDmon: What you suggest is about 22* below the factory values for timing. Just a few minutes ago, I tried 22*; drove the car; it as a definate improvement; take another 2* out, so that I am at 20*: and a bit better yet. I am also including the 2200 RPM column. Also I need to determine how far up the gms/cyl need this ultra low timing. I am now including up to the 0.32 gms/cyl row.

Bird

iTrader: (25)

Doc - which table are you adjusting?


Bird

Doc99SS

iTrader: (2)

I am adjusting the high octane timing table (the main timing table). I am keeping up with the low octane table also, keeping both tables the same. Should I be working with some other table?

SSpdDmon

iTrader: (10)

Once you start hitting the 1800rpm row, you should be able to start increasing the timing back up. Glad I was able to point you in the right direction.

Other thing to keep in mind....decel will probably refer to the base timing tables. If it's surging on decel, you may need to make changes there too. The trick is, get your idle timing low enough to where it'll idle fine but not be too high to affect decel.