Dixit

iTrader: (1)

So Im having this problem where say if Im in 6th gear in my Z06 doing about 40mph (which puts me around 1000rpm) the car jerks back and forth a little bit, if I shift into 5th its fine. This jerking only happens when the throttle is closed. When logging I noticed that it was about 22* timing during the closed throttle at 1000rpm in 6th and when it was in 5th it was about 26* timing.

So I increased the timing in those tables to 26* for the 0, 400, 800, 1200 rpm columns for the .08, .12, .16 g/cyl rows in both tables. That seems to have resolved the problem but now the problem is if Im coming to a complete stop say at a light, my timing will be now 26* instead of 22*.

Is there a way to keep it at 26* when closed throttle when moving and 22* when closed throttle at idle when at a complete stop?

Is that simply done by putting the 26* in the IN DRIVE tables for those values above and put 22* in those values for the IN PARK tables?

Just wondering because the IN DRIVE and IN PARK tables always confuse me when working on a 6spd where there really is no IN PARK setup. Unless the VCM knows the clutch has been pressed or the gear is in N.

Dixit

RedHardSupra

iTrader: (1)

that cam is not made to operate at that rpm with that load. stop driving like a wussy you wanted a racecar, drive it like one

Dixit

iTrader: (1)

Hahahaha........ Low blow.

I know that cam is not meant to be driven at that level, but was just wondering since Phil97SVT mentioned he had some large cams as well doing 40mph in 6th with no issues.

Dixit

RedHardSupra

iTrader: (1)

oh you can get it dialed in, but it takes forever, as the margin of error is near zero with cams that big on really low rpm. you can probably lug it in 5th at 1500rpm and have none of these issues. or put in shorter gears and have more fun with it at a minimal mpg loss.

if you got the time, just play with the live spark control. just start changing it 2-3 degs at a time using the 'relative' control (do NOT use absolute while driving). even if you get the bucking out, you still might have knock. 6th gear and low rpms on large cams just don't mix. the easiest fix comes from the driver.

Dixit

iTrader: (1)

Yea Ive been wanting to put like 373s or 390 gears on it, but I drive this everyday, I mean every day since its my only car right now. I drive it long distances like ATL to DC (700miles) and enjoy that I get 28mpg at times. Not sure how much I will lose in the mileage dept. with like a 373 or 390.

I agree though I shouldnt really be driving it in 6th at that low of an RPM, but sometimes Im lazy and just granny ****, I barely take it past 2000-2500rpm just on my drive to and from work. Other times I will get on it, but normal work driving I really dont bother unless someone wants to "play"

I was just wondering if the PARK table will hold my 22* timing and the Drive hold the 26* timing or will it be always 26* or 22*.

Dixit

Dixit

iTrader: (1)

Well just played with it and seems like the IN PARK table doesnt work on M6/M12 trannys. My IN GEAR tables is what I saw the values come from.

Now just wanted to know if I live the base Idle spark at 26* will that be an issue or none at all?

Dixit

RedHardSupra

iTrader: (1)

try upping it in 2-3 deg increments in the map/rpm areas where you're having the stumbling issues. i'll bet you the car will be much happier with about 32-33 if not higher (head flow, compression, etc dependent)

Dixit

iTrader: (1)

Yea I increased it to 26* on only the cells I have problems with which I mentioned above. Which was about 12 cells.

So you are saying run the base idle at almost 32-33* ? Really? I always through run it around 22-26* tops for base idle spark table. If you can put 32-33* thats a hell of a lot, is there any drawback to running that much or no drawback except it running better?

Dixit

RedHardSupra

iTrader: (1)

the way i figure this (and it might be a complete horsepoop, please point out errors):
at these lower rpms, the cam is way less efficient, thus makes less power than normal. so, it makes barely any power to turn over, that's why it's 'choppy'. if we don't have VE to make up the power, and we dont' have rpms (because we're at low rpms), you gotta give it some spark, hit it sooner, so it's got some extra power, so it behaves closer to stock. you still need the same power to turn it over, but you just get the power from a different source.

ok, laugh on, i'm totally not sure on this, but it feels right

Dixit

iTrader: (1)

Makes somewhat sense, but just wondering if 32-33* sounds too much and if there is any drawbacks to it. I cant seem to think of any. This evening when I had it at 26* for my 12 problematic cells, it seemed to run great. At idle (at a stop) it almost purrs like stock with a tad bit of lope, but nothing like when I originally had it at 18* and I could get the car to shake back and forth.

Dixit

RedHardSupra

iTrader: (1)

try it, you're at light load anyway (well, as long as you don't floor it at 1000rpm in 6th) so nothign bad should happen. i've had few different cars set up this way, and works fine.

Dixit

iTrader: (1)

What happens if I floor it at 1000rpm in 6th? I mean as long as my spark tables are in good order where Im not knocking I should be fine right, thats the only main thing to look at.

Dixit

RedHardSupra

iTrader: (1)

you're gonna knock in 6th at low rpm floored. i don't care how tweaked you are. just the nature of the beast, huge load will knock. to go back to the beginning of conversation: cam not made for this, don't drive it like a grandma.

Dixit

iTrader: (1)

Yea I know I know.... But good to know all this info and get the car running a bit better on closed throttle at low rpms. Good information and hope it helps others as well. Thanks.

Nick Williams

iTrader: (2)

26 degrees at idle is just fine. You could run more if you wanted.

Dixit

iTrader: (1)

Thanks Nick, thats all I needed to know, Ive run it at 33 and 26-27 and it feels fairly good.

Dixit