Difference Between Frictional Airflow & Startup Airflow

[Prowan]

Hey everyone. I'm trying to get my new cam dialed in on idle and it seems to idle fine when warmed up. Although, the starting is rough. Can anyone explain what is the difference between the 'Frictional Airflow Initial' table and the 'Startup Airflow Initial' table. I have seen some chatter that I need to add around 2 - 3 gm/sec airflow in one of these tables, but they look the same. If you have time, would you mind giving me some pointers on startup tuning for my new cam. THANKS!! LS1 2001 Camaro 225/229 patriot performance CAM

[Prowan]

any help with this one??

[LSxpwrdZ]

They both do the same thing from what I understand, just one is for frictional airflow (cold engine causing more friction and needing more air to stay running) and startup for just that startup airflow. Go ahead and add some airflow to that initial table and on the startup delay enter 100 cam revolutions so that it will keep that initial airflow added to the running airflow for about 10-15 seconds then it will start decaying away and then STIT will take over.

[bluebyu8484]

Should these tables need to have similiar data?

[jimmyblue]

They appear to be additive, on my car only one was nonzero.
If you make them identical you probably will end up with twice
as much air added, as either says.

[bluebyu8484]

I have my initial start up flow pretty high starting @ 15 @ 68 deg and reduced to 4 @ 140 deg then 0 from their out. Seems quite abit higher than I have seen with other tunes and I still have to throttle a bit for the first 15 secs and then with the throttle off it slightly surges until the ECT starts to rise. From there out it finds the target idle speed. I have the off idle scaler set to 1 and the decay set to .8. Is this the right way to go or should I be looking at friction airflow also? Fyi, my STIT & LTIT's are pretty much zero from initial start to warmup. Sorry to jack this thread, but is on topic.

[LSxpwrdZ]

bluebyu, this table doesnt seem to be the one you need to adjust. If you are having idle issues at colder temps then you may need more RAF tuning. Also what does your AFR mixture look like when cold? Sometimes the OL F/A table needs some adjusting for cooler temps to help adjust fueling.

[macca_779]

RAF tuning should be the main area you look at. It is ECT scaled and has a large effect on everything else. So get your STIT and LTIT's near zero at all temps first then look elsewhere

[GoatCheese]

Both of these tables add additional air to the car at startup. So the actual amount of air is the base idle airflow table + friction + startup air together to get the total amount of startup air or how much the IAC opens on startup. The difference between the two is how they subtract. The friction air has a initial amount of air a delay and a decay value. The initial is the start amount of air it adds, the delay is the amount of camshaft revolutions until it starts to lessen. The lessen amount is determined by the decay values that subtract from the intial once the delay has expired. A larger number means a faster decay.

The startup air has a initial and a delay that work just like the friction but no decay. So the main difference is the friction air will lessen until it zeros out and the startup air will just stop adding at once.

[morepowerjoe]

So how would you get the start up airflow to last longer?

[SiriusC1024]

Increase delay or decrease decay.