Idle in open loop or closed?

[v8zcar]

Hello, I'm a real newbie at this and I've read as many threads as possible on the subject of installing, tuning, and using the FAST system.

I will soon attempt to fire up my engine and I have read here that it is better to have idle in open loop. If I do so, how do I know that when first cranking the motor, I am too rich or lean (aside from pulling the plugs each time)?

If I could crank and watch the 02 readings, make some adjustments, and crank and watch the 02 readings, wouldn't that be easier?

Also, is there a danger or damaging the 02 sensor during this phase when I'll be basically using the hit and miss method to get my engine to fire and then idle?

Does everyone normally play with the VE table first? or the cranking tables, etc?

Short list of specs
383SBC
FAST B2B WB02
TPIS Miniram 2
#36 lb injectors
MSD 6AL, SS Blaster coil

A sample .gct file would greatly be appreciated.
Thanks in advance,
Owen

 

[bobc455]

Owen-

Idling in open/closed loop is something to worry about after you get the car running right.

Generally speaking, the cars usually crank over and start the first time you try, I would just have a timing light handy to make sure the timing on the car matches what the computer thinks it is. If the car doesn't start, you can listen and judge by feel- if the motor spins really freely, chances are you are too lean. If the motor cranks slowly and you smell gas, it is too rich. You'll be able to tell when you try it.

The oxygen sensor won't be useful during cranking- raw fuel doesn't show up well, and the sensor isn't up to temperature yet anyhow. The O2 sensor needs more of a steady-state running condition before it will be useful.

Before you try to start the car, make sure the timing table is somewhat reasonable (initial timing around 10 degrees or whatever). Then make sure your A/F ratio table seems reasonable- somewhere around 14-14.5 :1 is a good starting point for your idling. As long as these are close, go ahead and try to fire the motor.

Once the motor is running, play with the VE table for a minute to get the car to run right. Once it is stabilized to the point where it will idle by itself, wait for the O2 sensor to warm up, then use it to make the actual A/F match the target A/F ratio (by reading the dashboard and adjusting the VE numbers).

That should be enough to get you going- I think you'll find it pretty easy to do.

Once it's been running for a while, you can decide whether you want to idle in closed loop or open loop- I've done both, and am now back to an open loop idle. But I could run in closed loop too. Once you get the VE tables close, I think you'll find it doesn't make much difference.

-Bob Cunningham
bobc@gnttype.org

 

[v8zcar]

Thanks Bob,
Now all I need is the TIME to do it!

I received my system with a demo file but it is for a GN V6 turbo, mine is a small block chevy. If I just change the firing order, displacement, etc, I should be able to get it to fire or close to firing?

I was wondering about how people proceed with this system on a new engine.
Crank and get it running using methods above, then play with VE tables to get close to 0% O2 correction, then...? How do I know I need to adjust the cranking-coolant sensor table, after start tables, etc? I guess it's all experience?

Thanks again!
Owen

 

[bobc455]

Owen,

For getting up and running, you only need to change the critical stuff (firing order, # of cylinders, etc.). The VE tables, A/F ratio tables, and timing tables are probably close enough to get you running okay.

If you have never run your motor before and will be breaking in the cam, etc., then there is the possibility that you will have difficulties and might cause the engine to run poorly, which you don't want to do while breaking in a cam. If you have a known combination that you can borrow to break in the cam (such as a factory intake with a 2-bbl carb or something) then you won't risk ruining your cam while trying to figure out your FI. 80% chance that you'll be just fine with the FI, but 20% is a big risk of ruining a cam IMO. But then again changing the intake and distributor is a pain also.

One other question- do you have HEI? If so, write to me off-list.

If you are just tuning this setup for the first time, then once you are running your long-term project will be to adjust the VE tables so the O2 correction is as low as possible- 5% or better is pretty much as good as you'll need, 3% is "perfect". The rest of the parameters (cranking fuel, ATS correction, etc.) are probably close enough for now, but you'll keep playing with them for a while as you keep driving. But that's really just playing around, your VE, timing and A/F are the three biggest things to worry about. Most people have probably never even looked at their after-start values!

-Bob Cunningham
bobc@gnttype.org

 

[v8zcar]

Thanks Bob,
I'll try out the demo file with a few changes this weekend.
To answer your question, I do not have HEI.

Thanks for your help! I'll let you know what happens.
Owen