0ski_dwn_it

Glock,
I was wondering if you could save them in .csv form so I can take a look too. I am going through almost the same problems and would like to follow your progress. Thanks. Also the above link asks for a password when I try ot access them. Thanks.

GlockLT4

Here ya go ski: (I have both .uni & .csv in the zips now).

http://www.gulicks.com/vette/programming/2-4-02.zip http://www.gulicks.com/vette/programming/2-6-02.zip http://www.gulicks.com/vette/programming/2-8-02.zip http://www.gulicks.com/vette/programming/2-8-02-2.zip http://www.gulicks.com/vette/programming/2-8-02-3.zip


[Modified by Glock'94, 12:49 PM 2/9/2002]

GlockLT4

Arg.. my webserver is messed up. Won't let me log in .. I'll try to get those updated ones on later today.

Edit: OK, all fixed.


[Modified by Glock'94, 2:12 PM 2/9/2002]

Hendej

Here's were it gets a little tricky.

There's maybe another tricky area here, at least for me. When in WOT the computer goes open loop - the O2 sensor is no longer consulted. So if all the BLM's are adding fuel up to this point, is that information somehow carried over to the open loop fueling? How accurate is it? Is there a way to relate closed loop BLM's to what's happening at WOT aside from plug reading or watching on a wide band O2 sensor?

I suppose if the KS is working properly there's little danger of engine damage, but WOT is where the action is, performance wise. If I spend time and effort getting all the long term's to 125, then sure, I'm maybe doing wonders for the environment and part throttle performance should be pretty good - but how does that relate to what's happening when I hammer it in the quarter mile?

ChrisB

Technially at WOT the computer is in closed loop (if it was beforehand - e.g., car is up to temp, etc.) it is just in PE (Power Enrichment mode). In this mode O2's are ignored. Effectively it is still similar to open loop, just conceptually it is different.

If your l-trims are consistently over 128 at part throttle, then the corrections can be carried over to WOT (to ensure you don't run lean at WOT). Since your l-trims can vary based on the last cell accessed, etc. this can lead to inconsistent fueling at WOT.

If you keep your l-trims under 128 then the computer will just lock them at 128 (no change) at wot - whether they are 108 or 127 - the computer will never pull out fuel based on these at WOT.

So you get more *consistent* tuning at WOT - you can then fine tune your a/f ratio with the pe vs. rpm table.

Does that make sense?

Hendej

ChrisB,
I thought the O2 sensor is what closed the loop. (I'm an ECM. I'm pulsing injectors. I need to know how I'm doing. I need feedback. I'll use the O2 sensor reading. Pulse, sense, loop, pulse, sense, loop, etc - I'm in closed loop) Anyway, that's how I understood it.

you can then fine tune your a/f ratio with the pe vs. rpm table

This is my burning question: How do you determine what values belong in that table? Not by looking at BLM's as they don't change in pe mode. Am I just supposed to assume something based on BLM of the cell which was active just before entering PE mode? Wouldn't adding a WBO2 sensor be a better way to not make any assumptions about fuel/air ratio at WOT? Then again, how about quarter mile time? For many of us, that IS the ultimate goal of using WOT. But that is time (and gas) consuming. So maybe WOT up to 5200 RPM, kill the ignition, then look at the plugs? What do you recommend to tweak the PE table?

BTW - It makes sense not to pull fuel at WOT.

ChrisB

Hendej - don't worry, you are not missing out on anything - the point comes up on a continual basis. It's the difference between a system process design and GM terminology.

Yep, if there were a system you were making, the O2 sensor closes the loop and allows for feedback. By that definition we are in open loop.

But open and closed loop also have other connotations with respect to the PCM operation (bit's that are set, tables that are referenced, etc.) and when we look at it from that perspective the computer is in closed loop mode, learning is just disabled.

It sounds like just a matter of semantics, but if you monitor the pcm and work with it that is the way it considers the event.




I always try and tune it close, but rich by hand - just drive the car and monitor the plugs, etc. When I think I have it reasonably close it gets put on a dyno with wideband O2 capability. This is really the only way to correctly monitor this.

I would recocmend a wideband O2 to everyone who can afford one - but unfortunately they are a bit pricey. Track times are also a good indication - but if you run a 12.01@115 that doesn't really tell you if you need to change the shape of the curve, etc. You are best setting the shape of the curve on the dyno, then changing the offset if you do tuning at the track (e.g. moving the whole curve up or down).

HighHopes85

Chris-In regards to your last response about tuning it on the dyno with a wide-band...

First off, my setup isn't ever going to get me into the 12s and it is going to be a while before all the loans get paid off and can start thinking about a new set of heads and intake. But I always wonder about how close to driving on the dyno equates to driving down the road. For my purposes plug checks and the usual data scans seem to be appropriate.

I have a buddy though who is ProCharging his 383 94 1LE and after he gets it set up (looks to be back on the road in about a month...the belt took over a month to get in), is going to take it to have it reprogrammed on the dyno. In a case like his, wideband tuning is a must, but how does the load of the rollers compare to the open road? Is there any kind of general trend that you usually see such as running on the road will cause a slight bit of a lean trend compared to sitting still on the rollers? I have very limited experience running an engine dyno during some thermo labs about the Otto Cycle but was wondering what is usually expected with the chassis dyno.

I didn't really ask the question I meant to ask mainly because I don't know how to word the darned question. I guess this is the short of it. What kind of varying load conditions can you get on the car when it is on a dyno? How many "points" do you get to fill up the lower and upper VE tables if you data log at the same time? Once you get these points, are they just as good as if you would have run em on an open road with a wideband hooked up? I realize the difference in airflow and in his case, the intercooler needs it. Just wondering mainly about the loading conditions that can be simulated. If you followed it ;) what's your take on it? -Matt-