Once I put in the XE 230/236, ported heads, Hooker LT's, 3200 stall vigilante converter, 3.73's, 36# injectors and the other goodies on my engine, what settings should I tweak with LT1_edit? I haven't seen anything online that says "check these settings then put in this number and tweak it until this other sensor reads so-and-so." It goes without saying that LT1_edit can help you tune your car... but the question is how do you know what settings need to be tuned? If someone could point me toward some stuff to look on the tuning process itself it would really help me out.

--Trax

 

You wont see much of that, because its expected you know how cars work, so it takes some time reading and learning to figure how much timing to add here, remove there, AF balancing, etc

http://www.bfranker.badz28.com/fbody/links.htm#PCM
http://para.noid.org/~lj/PCM%20Tutorial/PCMtutorial.htm

 

Doc - thanks for the links.

 

Once you have changed your injector size to 36# with the LT-1 editor, drive it around for a bit to let the computer learn your new injectors.

After a day or 2 of learning, then I suggest a trip to the wide band dyno. Where you can base line the car and then start to "tweak" the PE table. You can monitor the O2s on the wide band O2 sensors and cross reference that to the HP you are making. I think you shoot for 13:1 air fuel ratio, but readings from the wide band will help guide you. The stock LT-1 PE table is very rich around 4,800 rpm to 5,400 rpm and also has room for leaning out on the very top as well.

Around that time you may even want to add a couple of degrees of timing and see what that does.

The important thing is to have it on the dyno with the wide band O2 sensors in place ... that way you know absolutely what the changes you are making are doing to the exhaust gases and the HP generated. How lean you go is up to you and your comfort level.

That said, it doesn't take all that long to tune your car, around 2 hours and 7 pulls on the dyno should get you 90% of the way there. As always, it's that last 10% that costs the $

Hope this helps

LWM

 

Well you did help me some, But I can't help but ask.. I have lt1 edit, and a d-1 charger.. My car stays in closed loop.. And why does it take two days to learn the injectors.. Why would mine stay closed? I dynoed at 385 rwhp and 440 rwt, with no tuneing what-so-ever.. I would like to improve these numbers, but the closed loop, And the question of needing to change settings for the increased air do to the addition of the charger are kicking my dawg.. Any good pointers?

 

May not take 2 days for the computer to "learn" the new injectors, but it does take some time. The new, larger injectors will have different opening lag times ... I think the term that best describes it is "injector offset". Different, ie larger injectors respond to the CPU's instruction to "open", differently over the same time frame than do the stock injectors. The net effect is that an SVO 36# injector does not respond in a 36/24 type ratio. Thus the need for the computer to "learn".

For the tuning part, when you exceed 66% throttle, you go open loop, and the computer takes its last reading closed loop and then goes from there into open loop, so closed loop does affect open loop ... make sense??

You do need to be on a dyno with a wide band O2 sensor to do any real tuning. And most if not all the tuning will be via finagiling the PE table so as to approach the widely accepted optimum 12.5 A/F ratio.
Note, if you are running an FMU, then just adjusting the FMU will do the same thing as adjusting the PE table.

The only real message here is ... wide band dyno tune

Hope this helps

LWM

 

It did, but mine never leaves closed loop... ????

 

Let me correct some of this. First, the only learning the computer does is thru the blm's and int's - and these will respond fairly quickly - maybe about 10 minutes of drive time in closed loop. Now in regard to the injector offsets - different styles of injectors take different amounts of time to open and close. There is a table in tunercat/lt1-edit for this that you would need to update with the proper injector offsets. They are an additive factor in the fueling equation, so at low pulsewidths (idle) they will have a relatively large effect. If you leave them at stock, the computer will attempt to compensate and you will see your blm's at idle far away from the nominal value of 128. You can find some injector offset listings at www.carprogrammer.com

The other issue of going wot - the pcm looks at the blm's of the cell you were last in before going wot - this is typically cell 15. If the blm's were 130 or lower (rich mixture) then the pcm uses 128 (neutral) for wot. However, if the blm's were over 130 (lean mixture) the pcm will use that blm for wot, thus richening it up. There is a program to lock the blm's at 128 no matter what, it might be had at the site above.

I agree about going to the dyno with the wb o2. Otherwise you will really have no idea what your afr is at wot.

Joe

 

OK then, what software are you using to log your runs, I use the PCMcomm.exe that comes as part of the LT-1 editor package, on the front page there is a spot for seeing if you are Power Enriched or not. If you blip the throttle even at an idle, you can enter Power Enrichment mode, I'm pretty sure you enter PE mode at 66% throttle. If you are Power Enriched, then you are in open loop.

You can also sort of see it on a logged run, at around 60% throttle, the O2mvs go from being all over the place (100 to 800mv) to being consistently over 900mv.


As for the learning time mentioned by jgeorger, I was always under the impression that it took at least a day for the short term fuel corrections to make it into the long term fuel correction memory, but, what ever, just make sure you give it time.

If you don't find what your looking for at www.carprogrammer.com, e-mail me, I have some injector off set tables as well, probably the same ones though.

Hope this helps

LWM

 

There is a table in Tunercat/LT1-Edit for what tps make the car go into pe mode depending upon rpm..... It's 66% at lower rpm, but as rpm rises, it comes down to around 28% iirc.

Depending on your logging software, and what people call open loop or closed loop:

In datamaster once the car heats up and enters closed loop that flag is always displayed, even if you go wot. Some might call this open loop since the O2's are no longer providing feedback. Just to avoid confusion I always call it wot or PE mode.

I have direct experience seeing how fast the blm's and int's react to changes. Just go put the wrong injector size in there and see how fast they settle down.....

Joe