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| iCorvette | How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
 
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At what voltage? is there a load criteria?
or does it just stays in closed loop.... |
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Posted on: 2009/8/8 5:55
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| vetteoz | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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It goes into Power Enrichment(PE ) mode which is not OL
Read http://www.thirdgen.org/techboard/diy ... -p730-target-afr-how.html |
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Posted on: 2009/8/8 8:30
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| TommyT-Bone | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Chair-man of the bored
 
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That certainaly clears things up a bit.
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Posted on: 2009/8/8 12:34
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| vetteoz | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Quote:
The short version; at WOT the ECM engages PE mode; where it calculates fuel from a set "chart " for want of a better word ,instead of using the O2 sensors as in normal closed loop operation.It does not drop back to open loop as in cold startup. Quote from above link "In PE Mode the Base Pulse Width ( amount of fuel ) is calculated from a theoretical Air/Fuel Ratio (AFR). This AFR is independent from the O2 sensor. It is simply a theoretical target value that the ECM is going to make an attempt to achieve without any feedback ( from the O2). |
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Posted on: 2009/8/8 12:48
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| iCorvette | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Quote:
 Thanks.... |
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Posted on: 2009/8/8 16:26
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| 383tpimachine | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Master Guru
 
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OK so since my tune is ALL out of wack Im losing alot of power when going WOT?
this is probably why it bogs so bad at WOT |
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Posted on: 2009/8/8 20:25
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| iCorvette | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Quote:
supposedly it goes to power enrichment not open loop, learn something new everyday |
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Posted on: 2009/8/8 21:33
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| bogus | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Grand Imperial Pooh-Bah
 
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for sure. especially if the PE tables are set for stock. |
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Posted on: 2009/8/8 22:22
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| mseven | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Quote:
383tpimachine wrote:OK so since my tune is ALL out of wack Im losing alot of power when going WOT? There are several inputs/look up tables that play a role in calculating PE, and or the performance in WOT. While timing is a factor ("bogging" description}, the calculated PE AFR also includes the last BLM used/seen (along with other tables) to formulate AFR at WOT. If entering PE lean, the overal PE/WOT AFR will be affected (likewise if entering PE rich). Depending on when you enter PE (RPM vs load), this can change the afr when entering PE. This is why developing the closed loop area of the tune should be done first before tuning for WOT. |
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Posted on: 2009/8/9 16:19
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| iCorvette | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Quote:
wonderful insight.... would it not that the maximum airflow vs. rpm must be adjusted for an engine with greater ability to move air. and I should max it out to a 255 default providing it with a greater range sensitivity. And conversely with stock ceilings per rpm assigned, this can fool the maf into thinking X amount of air is moved vs. the correct albeit more volume of air is actually moved, henceforth creating a lean condition, and when the throttle depending on where I trigger PE can result in the concomitant lean condition as you metioned above. is this correct? |
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Posted on: 2009/8/9 18:55
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| mseven | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Quote:
wonderful insight.... would it not that the maximum airflow vs. rpm must be adjusted for an engine with greater ability to move air. and I should max it out to a 255 default providing it with a greater range sensitivity. And conversely with stock ceilings per rpm assigned, this can fool the maf into thinking X amount of air is moved vs. the correct albeit more volume of air is actually moved, henceforth creating a lean condition, I have used this table primarily for c.l. tuning below 4000. Raisng the air flow in any particular RPM in this table will have the effect of richening. Typically I look at everything above 4000-4500 being pe., therfor from 4k and up I set to 255. For PE if I can't add enough(or subtract)using the 'PE vs RPM' table, I will use add on tables such as : 'PE vs.temp' add-on (which when adding fuel percentage will also reduce inj.dc) and also 'ae factor vs change in load', as part of a base tune. TPS postion, is a part of it but I look at were it actually entered (specific rpm vs.load), and go from there. First I tune C.L. with pe disengaged which allows me to tune higher rpm and deeper into the load range. Once I have the blm/afr locked (not moving and very little int. change)across the board I begin tuning PE (using a afr meter). This has given me pretty consistant results entering pe at various rpm, load ranges. I have found there to be no problem attaining a good cl tune as well as a solid wot tune in typical 383 and 350 set-ups. I believe the need for additional AF grams above 255 would become needed if using a FI/blown set-up or possibly a high rpm real fire breather. Pat (tequilla boy) has been using a ford maf which I believe provides 300+ grams. |
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Posted on: 2009/8/9 21:54
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| anesthes | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Master Guru
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Quote:
Pat really went to town changing code, as well as the airflow calc. The stock code reads up to 1792 counts, and translates that to up to 255 grams. (which happens to be the limit to an 8 bit signed integer). Pat changed the way the code worked in a manor that I believe still reads from 0-255, but is no longer relational to grams. He also reworked it to read the ford MAF, to translate whatever crazy voltage it is into counts. So in Pat's setup (I believe, it's been a while since I discussed this with him) 100 grams on the tale might really be 150, and 255 might be 382. I believe he's also reading IAT from the ford sensor as well. Pat is a smart cookie. A lot of guys on thirdgen.org are switching to vortec/ls1 ECM's because the ability to read higher airflow with those MAFs. On a conbination with a crazy camshaft (something with like 80 degrees of overlap) that could work a lot better than MAP. Big cams pass almost no air at idle, which makes MAP calibrations a pain in the ass because of lack of manifold vac looks similar to WOT on the table. Plus it makes AE transitions a nightmare. -- Joe |
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Posted on: 2009/8/10 2:37
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| vetted | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Guru Newb
 
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First came the IOTA then RSGB had their VHF shindig then this weekend it was the MDC QSO party...dam can't anyone spell out these big long words?
WOT...Wide Open Throttle? I'm guessing. But the more I read these posts the more ignorant I feel cause I know not waht you speak of, I just own and occasionally get to drive a car that matches the dream of my youth. Is there a translation guide somewhere? More lost now than I was in the 60s. |
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Posted on: 2009/8/10 6:44
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| BrianCunningham | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Who did your tune?
That's one area where it pays to find someone that can do it for you. |
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Posted on: 2009/8/10 13:26
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Polo Green 95 LT1 6-spd http://mysite.verizon.net/vzevcp74/ 383 LT1/Vortech Supercharger/AFR heads/Rod end suspension/Penske-Hardbar dual rate coilovers/Wilwood 6pot brakes NCCC Governor: http://BayStateCorvetteClub.com |
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| anesthes | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Master Guru
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Quote:
Isn't that the truth. Any monkey can bolt parts on, but tuning a car takes talent. -- Joe |
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Posted on: 2009/8/10 13:56
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| tequilaboy | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Guru Newb
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With the HPX sensor, I'm simply doubling the range to 510 gm/sec now. With my own car, I'm seeing airflow peaks around 430-440 gm/sec and targetting 11.8 AFR in PE.
An example Vortech Si-trim with a 3" pulley on an otherwise stock L98 is flowing around 370 gm/sec at 5,400 rpm with the same sensor with a 260F discharge temperature. Here's a pic: [IMG]http://i15.photobucket.com/albums/a372/tequilaboy/07-18-09_1804.jpg[/IMG] |
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Posted on: 2009/8/10 15:58
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| iCorvette | Re: How true is it when they say at WOT the Corvette goes into Open Loop? | ||
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Senior Guru
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Quote:
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Posted on: 2009/8/11 1:24
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