Ski,
I don't profess to have a fraction of your knowledge about this but I have been following the 3rd gen board for a couple years now and have read a few of Chevy fuel injection books out there and I have my own rotten experience with my set up.

It has been my understanding that when you are in PE mode, the ECM is adjusting fuel delivery relative to the BLM level. This kind of supports what I see on my Ease scanner when I have done some datalogs. The parameter that says closed loop stays in close loop but the learn control is off. Unlike when you first start the car and it says open loop and learn control off.

I also believe this based on my own experience with my set up which has been a disappointment. With 30lb injectors, my FP set at 43 and(approx factory, vac. disconnected) my BLM's are all showing lean. From the 150's at idle to around 140-145 in cell 15. Yet, I believe I am running too rich at WOT. I can't remebr the O2 sensor reading at the time, but when I mentioned it to Corky one day at the track, he said it was way to rich. I had a custom chip burned by Bob Ida @ http://www.idaautomotive.com on his dynojet dyno. (he's located about 5 mins from Raceway Park). I know he logged at least 20 dyno pulls and claimed that at the end he was able to get 327 rwhp and 409 rwtq. When I ran at the racetrack, my best et's were 12.85 (little relevance due to street tire) but my best MPH has been 109. I believe I am conservatively losing about 6 mph based on my set up.

I had it dyno'd again at last years vette mag day and it pulled around 295 rwhp ( my memory is a little foggy) with an AF ratio of about 13.1 or 13.2 on their wideband. (thru the tailpipe). I've given up on any further tweaking until I can replace my heads with better flowing units.

Just my .02


[Modified by GlennS87, 10:18 AM 6/12/2003]

 

Nano & Glenn,

There are some good points you fellas make.

The problem is that the *way* the ECM is understood to work, I know is not right pertaining to WOT. The *way* it was understood to work, is the way Ralph expressed in his one relpy. Which basically is:

With no other tuning changes except for FP, the injectors PW should have stayed exactly the same.

Yes I would be running richer than before, but just because of the pressure increase. And the fact that with the increase in pressure, the fuel delivery is increased during the same PW time.

Think of a garden hose. If you measure the quantity delivered in 1 minute with 10psi line pressure it say 2 gals. If you increase the pressure to 30psi, and open the hose up to exactly the same point again for the same timeframe, you will then get 4 gals. Just because of the increase in pressure. Those numbers I used were just examples, in case there are any garden hose experts there :D

But in the case of my car, yes it got richer as expected, but somhow the ecm knew to cut the pw back some. How did it know to do this? That is the troubling question.

I obviously need to do more testing, but first priority is going to be get it tuned for part throttle, so I can race this weekend. If it runs like a dog, because its too rich, as I suspect it will, Iwill turn the pressure back down to 43 adn put the old chip back in. Hopefully it will turn a 10 this Sunday :smash:

 

Jesse, what do the guys you trust on thirdgen say about the PW being reduced in your example? I know very little about these ECMs, but it seems like the open loop tables (including WOT) are setup as the reference and the long term integrator shifts the table based on what it has learned in closed loop. Like i said above, even at idle, my car will run like crap in open loop on a reset ECM, but will idle perfectly in open loop after driving the car a bit. Good luck on your research....................

BTW, don't be too surprised if after you get the fuel right, that air flow doesn't quickly become the next obstacle. I know of very few SR cars that have run in the tens....regardless of cubes/cam/whatever., and 125mph seems to be about it. new92racer has dipped into the tens on the few occasions he hasn't blown his rear, and Julio form Cartek was well into the 10s with a very similar combo to yours. The biggest difference i see was his 4-link assisted 1.40 shorts. As i told you in my email, julio was running 32 or 36 lbs injectors at 60 psi!!!!!!!!! You've just about got the 125 mph covered, now you just need to figure out how to get 1.40 shorts..........good luck.


[Modified by ralph, 11:35 AM 6/12/2003]

 

Ski, I have no idea what I'm talking about but it looks like you're going into uncharted territory - maybe, since you're past the RPM limits the car was originally designed to run at by GM, systems that aren't required to simply keep the car running are dropping out of the equation? Could have been a "back door" of some sort installed by GM with the thought some people may over-rev their car (but not keep it there). Once the RPM's come back down everyting joins the equation again. Maybe you will only get the thing to run so good and you've reached the limit? Does that make sense? I think this is kinda what some guys are saying... :confused: :skep:

 

Ski,
Are you getting the PW changes at WOT even if you reset the ecm and due a WOT blast immediately after? If you are, then my thought on the ECM using the BLM as the "starting point"(not the best description) before using the programmed PE parameters would be invalid. Otherwise it would seem to me that if you're BLM's have moved down into 1teens that would defacto tell the ECM that you're "starting point" is on the rich side of stoich. and that is somehow used in the code to affect PE tables. I'm obviously making way to many assumptions but it is clear that you need to find somebody who has really hacked the code ofthe 165 ecm.

I have followed many of your posts on 3rd gen so realistically you're not going to ge much help from old timers there but it seems to me tha Funstick has excellent knowledge of the code.

 

I have read about this before on a Buick GN site. It has to do with the ecm looking at the last BLM cell prior to enrichment mode and will make adjustments accordingly. If the ecm is pulling fuel out at that point it will pull fuel out during power enrichment. Likewise if its adding then it will also add during enrichment. I will see if I can find this site and will post it tonight. It was very good info.
It does explain what you are seeing. I have also experienced the same.
John

 

Guys,

Sorry I did not see your posts sooner.

Yes you all have very good points.

But I think John89 has it right. I was going to research someof the turbo GN sites to see what they have to say about it.

From my intuition, which is a scarey thought, John89 said it exactly the way I was going to explain to you how I thought it was working. But that is just my opinion...I have no evidence of that yet. Unless when I look or John posts a link to the page it become evident that its common knowledge over there.

You see many of the Gn guys have pushed MAF to its limits long ago. With the Turbos etc. And also much of this tuning stuff came about from there group. I fund a few sites I am going to have to start frequenting more often than the TGO, as said before, they are in their little groups and don't like outsiders, especially ones like myself that speak freely and with this setup defy everything they thought they know about MAF. Many of the people there believed that MAF could not support 450 flywheel horsepower, let alone almost that much to the rear wheels. You can clearly see that TheToy, Corvette1, and I are easily putting that to shame....I'm sure there are many others too. So what I am getting at is, the information comes pretty hard sometimes and I have to fight and scrap for every ounce I get. But I did have a GN guy email and and he said he would explain it in detail. So that sounds pretty hopeful, unfortunately I emailed him back and he hasn't returned my email yet,

I haven't fogotten you guys, just reading and researching!

Jesse :cheers:

 

Never mind, John already said it.
Basically an interpolation method. Once the MAF rails, you could look at the RPM and a few fuel points to calc beyond this point. (I really don't think the software in the 165 is that smart though. This also leaves you open to other problems.)
It is known that OBDII can and does adjust the WOT fuel numbers.

Thanks for posting your findings.


[Modified by ZylaRace, 2:09 PM 6/16/2003]

 

Guys,

Gnjones is helping me understand the inner working of the ECM. It appears and we have just touched on the surface of what I expect he knows and will hopefully share with me. That the ECM does us a routine based on BLMs to correct for WOT PWs.

I did find this formula on the GN turbo BB. Not sure if its valid, but it looks like it uses the routing that I described. Here it is.

Maybe its something to this tune mathmatically:

Injector PW = [MAF(g/sec)]*[Injector Constant (sec/gram)] * [BLM/128] * [INT/128] / [RPM] * [PE F/A vs coolant temp] * [PE correction vs. RPM] * [PE correction vs. TPS] * [PE correction vs. time in PE] * [Some conversions to make the answer be in msec's]
[found on the GNs page]

If Frank (Mojo) would permit me to, once I have aquired enough information from Gnjones, to put into my own word a sticky post that would stay on the top of the scan/tune board that would spell out the entire working of the 165 ECM. I think it would be a great help to the tuners of the board, and also to the clear up any confusion that might have been around. Like this subject for instance.

Frank maybe you can comment on that if you like. And the rest of you, if you think it would help. Thanks.

I will keep the information coming as it becomes available.

Jesse :cheers:

 

A sticky might be nice if the information can be verified by a couple people.

 

Yeah I agree. But finding people that know the inner lyings of these systems are like trying to date a super model. You can wish and wish, but to ever even cross ones path is a different story :D

The article would have to be written and read with the understanding that its to the best of our knowledge type scenerio.

Obviously there is already a bunch of confusion surrounding the systems. And I don't want to add to the confusion any more, so information would have to be backed with some hard data, like what I showed here. There is obviosly some type of correction factor happening. Lets see how the information unfolds. It may have quite a bit of validity once its all laid out on the table. It surely can't be any worse than the MAF stigmatism that already exists. A year ago, or even sooner, people claimed that MAF sensor could not support 450 FWHP. That is kinda a laugh now. And the people that started that rumor are the same ones that particularly don't care for my posting on the TGO. Oh well, information changes and we either learn from our mistakes or live in the past with our eyes shut.

I will keep you all posted.

:cheers:

 

Try this site. Calibration Secrets & tuning Hints. http://www.thrasher-ep.com/chips htm/cal hints.shtm

It absolutely amazes me that I'm still learning how mid 80's technology works!
Hope this helps you in your quest!
John
:crazy:

 

Damn the site is gone.
Here is the address of the folks that wrote the 16 page article that I have.

Thrasher Engineered Performance
1317-1319 Michigan Rd.
Burlington, In 46915-9998
765-457-8729
thrasher@thrasher-ep.com

Maybe this will get you closer?
John

 

On your comment of Open/Closed loop indicator @ WOT:
I believe what you are seeing is a loose interpretation of what is said about loop status @ WOT. I have seen what you describe many times. I don't read too much into it as I use this "closed loop" indicator as warm/cold engine status. This appears to be what GM reports it as. Once the O2 is warm enough to go closed, this bit is set, and remains so as long as the O2 cross-counts support it.
W/ a warm engine & WOT, the ECM goes into a Power Enrichment (PE) mode. This is loosly understood as "WOT Open Loop mode". Open loop, as the O2 feedback is not used to set the PW. (GM does support a PE flag w/ OBD2.)
I'm not aware there is a PE mode bit in the 165. You have to more of less recognize it (PE mode), by looking at the TPS & BLM numbers.
Correct me if I'm wrong, but that is how I look at it.

BTW, I agree w/ the GN calculation, I'm just not sure of all the ratio's used by it. i.e. I have seen other equations for other models. I'm not sure how much of it applies to the 165.


[Modified by ZylaRace, 8:52 AM 6/17/2003]

 

Zyla,

I hope to learn some more about it tonight. I will be sure to post it as soon as I find the answer for sure. It has to do with the upper blm learning and corrections to the WOT PW.