gpr

iTrader: (6)

Okay so i'm finally to the point of where i can start tuning on my car. I have played with efi live a bit different things here and there in different vehicles, and this will be my first gm vehicle to tune from scratch. I bought the car with headers, exhaust, lid and it has a cam. no idea how large of a cam but it has a little bit of a rough idle.

Anyway, I had my lc-1 plugged in yesterday and it was running slightly rich at cruise but o2's were adjusting properly. At wot it was around 12.8-12.4, is this what a naturally aspirated ls1 should be set to? Normally i tune motorcycle engines and on the dyno they make more power around 13:1-13.4:1

Also once the ve table is tuned in better, what should the ltft be? right now they are around 8%, i'd assume if the car is tuned properly it should be much closer to 0 but will always have a little bit. BTW, i always get this confused but - fuel trim means it is taking fuel away and + fuel trim means its adding fuel, correct?

How exactly do long term fuel trims work? As in I know it changes the fuel pased on the o2's if they read off for a while. Does the computer store these LTFT's? If so how do you reset them? When a LTFT is at 8% for a long period of time does it actually change the value in the VE table or where does it make the adjustment for the fuel?

Looking at the tune i see where they increased the MAF table values by about 8%. I was under the impression you really shouldn't change these, as the values for a stock maf should remain the same since it is flowing the same amount. Only should change them when the maf is changed. Is this a cheap and quick way to gain more fuel? I'm thinking i would like to put this back to stock values and tune the car properly with the VE table.

If i did start from a stock tune, where do you start at? Can i simply increase the entire VE table by a certain percent and then go from there and do the auto VE method? Cause if i put the stock tune in it the car, it will barely run.

Another random thing. I know this sounds crazy but i love the sound of a rough choppy idle from a big cam. is there anything you can do to enhance this? i want the car to run good but something to enhance the choppy lope would be awesome (as long as it runs and doesn't cause it to stall)

thanks for the help guys!

gpr

iTrader: (6)

Here is the tune that came on the vehicle. Looking threw it there is some stuff i would change in the torque limiting tables. But if anyone could look at it and make any recommendations i would appreciate the advice.

thanks

BLK02WS6

iTrader: (2)

There are quite a few things in that tune that I would do different...

To answer some of your questions...

The very first step to tuning the fueling is to get the injector tables right if you have other than stock injectors.

Then, tune the VE table first in speed density (MAF out of the equation). Once you get the VE dialed in, you tune the MAF table. I go over the MAF table no matter if the MAF is stock or not - that way the table is perfect...

As far as WOT AFR, I generally tune them between 12.5 in the torque band and 12.8 in the power band for an NA LS1 - fine tuning is done on the dyno, but I've found this to be the general range they end up in.

Timing is also fine tuned on the dyno to obtain the most torque/power throughout the range. The rest of the timing is best done on the street. After doing so many of them, most tuners have tables that are close for a given combination and just require some fine tuning...

LTFTs do not change the VE table - they add or subtract fuel based on feedback from the O2s. They add or subtract fuel when the PCM is in closed loop (part throttle), but will also add fuel in open loop (WOT) if the LTFTs were adding fuel when it entered open loop. This is why we tune to get slightly negative LTFTs through out the range... And yes, negative LTFTs mean they are pulling fuel (because it is rich) and posative mean they are adding fuel (because it is lean).

There are a lot more details to it than above, but hope that helps you out some...