Where do I start tuning??

[ablackFormula]

I've posted here a few times and I'm still completely lost. I just finished installing the FAST unit on my stock LT1, and although I can get the car to run, it's very barely and spits and farts whenever you try to rev it up. Letting the car idle for even a few minutes makes my eyes water, and the O2 sensor was locked at 15.94 as a ratio, which is the exact opposite of making your eyes water. So I sent the unit and O2 sensor back, and they told me there was no problem with it.

I just reinstalled it, and the a/f ratio is still locked at 15.94 (I double checked the O2 harness, no shorts/opens/grounds,) I checked for the proper voltages and grounds at the ecu side of the harness, all checks out ok. However, if I rev it up, the a/f ratio will change when I let go of the gas and the engine decelerates back to idle. I have the close loop parameters set. I tried changing the a/f ratio at idle by changing the corresponding cells in the VE table, and when I set the cells to both 100% and 25% I got no change in the way the engine ran. And also, now since I got the ecu back, the gauge on the dash no longer coincides with what the ecu sees for water temp (they did before I sent the unit out.)

When you first finish installing a fast unit what are the first tables you adjust to get it running right? (I copied the spark timing and VE tables from tunercat, so they're the equivalent of stock tables from my original PCM.)

Please send me some helpful responses, I'm lost and don't like it ..

 

[berrelauto]

Try contacting the dealer you purchased the unit from. If you bought it from a private party, we offer a tuning service either at our shop (we are right outside Philly) or we can travel, for a fee. Either why way we can straighten you out.

 

[ablackFormula]

Thanks for the offer but I'm doing it for a school project and am not allowed to have someone "do it for me." I'm kinda just looking for a pointer as to which tables to start attacking first.

 

[ablackFormula]

I feel like what I need to do is get the engine warmed up to get rid of all cold enrichments, set the idle to the speed I want using the IAC tables (which is done already to an extent,) and then adjust the VE tables until I see some a/f's in the ratios of 14.5-14.7:1, which I do by lowering the #'s in the a/f ratio. Stock timing at idle is about 27*.

I'm gonna go out to the garage and try this again but does anything sound wrong with my attempts at tuning? I don't understand why I'm having so many problems w/ it.

 

[ablackFormula]

I feel like I'm having a conversation with myself here, but thats nothing out of the ordinary for me to do anyway ... Here's my update:

I got the car fully warmed up and started changing the VE tables. From 0%-150%, the engine did not change in the way it ran. And I changed the cells that had the green circle in them, indicating those are the cells the engine is currently running in. (This is at idle, too.) Then I went into the target A/F table, and changed the target from 14.7 to 12. And the actual A/F ratio came down. With a desired A/F of ~12.5:1, the actual comes out to ~14.8:1. But I couldn't get the VE tables to adjust anything in the way the engine ran. Does the FAST ecu not look at the VE table in open loop or something? The help file says it does, but this is contrary to my findings...

Has anybody else had this problem before or just me? I'm still not convinced the ecu isn't bad.

 

[berrelauto]

Are you allowed to have someone teach you? We can also train you so you would be the one actually tuning it.

 

[fast4d]

you might want to idle in open loop. Even after switching to a "mild" cam (18" vaccum @ idle) I found it easier to smooth out the idle using open loop. I don't go into close loop till 2k.

set idle speed using the screw at the throttle body. only use the IAC follower for fine tuning. once the car is warmed up now you can work on the cells that affect idle and go from there. good luck.

 

[ablackFormula]

Thanks for the idea of using the actual throttle blade to adjust idle speed and the IAC to fine-tune it. Idle is set to be at open loop, I don't have the program in front of me but I believe I set it to go into closed loop at 1200 RPM (it's a stock motor.)

When you adjust your VE tables for idle (low RPM, low MAP,) does it affect the way the car runs? I find it extremely weird that putting in 0% and then changing it to 150% VE does not change the way the car runs...

 

[fast4d]

yes but not right away. I rev it up a little so the "dot" will move out of the cell(s) I just changed. once it comes back then I'll see a change.

I could be wrong but the A/F table will still affect even if you are in open loop.

 

[mosk]

I'm sure you've looked at all the obvious stuff, but for the record, you did enter the proper values for injector size, engine displacement, and the other fuel parameters, right?

Do you want to post your configuration files so that others can look at them, or would that violate the spirit or letter of the rules?

-Jeff

 

[Ricky Trussell]

You should look to your A/F table first to see idle A/F ratio. Should be say 13.2, so make the two cells above and two cells below and to each side 13.2. That will gwt you started tuning.

Then look at your idle VS coolant temp set your idle speed where you want it, say 800 at 150 degrees and above.

Go to your throttle follower page and see if it is set at 10 at your idle tps. If it is set there then look where it is actually running. If it is above that then go to your throttle body and turn the throttle blade adjustment screw in like you are going to raise the idle on a carb. You should here your IAC closing and your idle going down. Then check you idle speed again.

If you have a mild cam I would use closed loop at idle to get you close tuning. Look at 02 correction and raise or lower the cells to get your 02 correction done to say +- 5%.

You have to remember that you have correction limits that will only let the 02 take or add so much.

Then post again.

 

[ablackFormula]

I didn't know you had to rev the engine out of the cells, then let it fall back in them, in order for the VE changes to take effect--that makes more than a ton of sense now I was wondering, why could I go from 0% VE to 150% and have no engine change?

I got the engine running relatively well now. Tomorrow I will bring it to work (Goodyear ) and see if I get some free time to throw it on the inspection dyno, where I can put it on cruise control at whatever mph and tune it there, without having to worry about the driving part.

And as for the obvious stuff, I triple checked and all the injector constants, engine displacement, number of cylinders, etc, was all good and ready to go. Nothing out of the ordinary was found there.

I'll post back tomorrow night for those who are interested, and I thank everybody who responded to me, this is definitely a huge learning curve for me n I'm lovin' it

I'm sure you guys know how it feels to have your cars not running for up to a month, then to find out the problem and get your baby back... this is me right now

 

[bobc455]

It sounds like you have a pretty decent understanding of the VE tables and their purpose- to make the actual A/F match the target A/F. This is where most of your tuning time will come in.

Besides that, I think the best way to figure it all out is to open up CalCom, and go through each table and try to figure it out. It might take an hour or so, but this way you'll have a look at every possible table in CalCom and become familiar with it. As you look at each table, you will also figure out what it's supposed to do and how it influences the car's operation.

Did you purchase the unit from a dealer? Typically they include enough profit margin cover their time to instruct you on tuning, etc. (since it is obviously impossible for Craig Smith to spend time with every single buyer to help with every single tuning problem).

What happens to the A/F ratio when you drive? Does it move from 15.94? Maybe there is some sort of anomoly that gives a funny O2 reading at idle. And don't forget that an exhaust gasket leak will give you funny readings...

-Bob Cunningham