1STGEN68-2000SS

Ok I am running a 99 Formula heads and cam with a 100 shot . I checked the timing values with the engine running at 6700 rpm in park with a Snap On scanner and it was dead on 38 degrees. Does this mean that the wide open throttle timing is 38 degrees or does it have to have a load on it to read correctly. We have run this car for about 2 years at the track like this and this is the first time that I have checked this. I know the timing will flash to a higher setting during acceleration but it never moved from 38 no mater how long I held it at 6,700 rpm.
Alan

ringram

Take a look at the high octane table in the tune some time, you will see where it needs to be loaded to for the various timing points. It varies across the RPM range as well as g/cyl load points.

SSpdDmon

iTrader: (10)

Without a load, the timing will read higher.

Here's the timing for a stock 98 A4 car. Typically, H/C cars will be tuned to ~27* of timing for WOT from about 2400rpm on up for .60grams/cyl and higher.

1STGEN68-2000SS

Thank's for the reply's
I think we need to see the timing values on the dyno or capture them on a run.
Alan

Gh0st

iTrader: (3)

What exactly does the ".60grams/cyl" stand for? I know RPM...but what is the grams/cyl?

ringram

Its the weight of air in the cylinder.
Calculated from airflow, rpm and charge temp etc.

Gh0st

iTrader: (3)

So as the grams/cyl goes up, you want to lower timing. I would assume the higher the grams/cyl the higher the intake charge(hotter air). What is the calculation to determine grams/cyl because I would like to know how air flow comes in to the equation.

SSpdDmon

iTrader: (10)

It's simply airmass in the cylinder. It represents load. As airmass increases, you'll need less timing. N/A cam'd cars will typically see .68~.88 grams/cylinder and run ~27* timing down near sea level. Boosted cars with 5~7psi will tend to see .90~1.10 grams/cyl. at WOT and typically run 16~21* of timing @ WOT. The older cars (with a distributor) usually referenced load based on vacuum. While this works, it's not optimal because vacuum doesn't always represent load. A perfect example is what you did - holding the rev's at 6K+ rpm. There's not much of a load without the drivetrain engaged, so you probably were around .20~.24 grams/cyl., which is why you saw the timing you did. Compare that to manifold vacuum and your MAP kPa was probably in the 90's (low manifold vacuum). Had it been a distributor type setup, that would have been enough to reveal WOT timing.

Essentially, it's load. You'll usually see the highest grams/cyl. numbers at peak torque.

Gh0st

iTrader: (3)

So if I understand this correctly, if at 400rpm, I slam on the gas, the engine will get -4 degrees of timing? And if I slowly hit the gas it will get around 19 to 9 degrees of timing?

Like wise, at 6800rpm, if I hit the gas slowly, there is not much load on the engine until I start flooring it and then the grams/cyl start building up and then the timing is reduced to save the engine.

I would assume the lesser timing in the 4000-5200pm range is because that's where peak torque exists and you want to lessen timing to prevent detonation?

SSpdDmon

iTrader: (10)

The stock table does reduce timing for peak torque. But, most cam'd LS1s don't need this. Setting the timing at 27* from 2400rpm on up is usually where a lot of tuners start.

zmonsterjb

iTrader: (16)

is that everything from 2400 and up?

2xLS1

iTrader: (25)

So you just hold it at 6700 rpm in park for an extended time? Interesting.

1STGEN68-2000SS

no mater how long I held it at 6,700 rpm.
Well I was only talking about 5 seconds not all day
Alan