Power Enrichment, when does it actually kick in?

[zimbobway]

***Tuning Noob Alert***

Just trying to work through the tuning learning curve so I was working through the numbers for my 2010 Camaro LS3 in the PE vs RPM table and it seems that GM has these cars set to command about 11.5-11.7 once enrichment kicks in, the key being once enrichment actually kicks in. Looking at the default PE Delay RPM of 5000 and the Enrichment Rate of 0.0200, does it EVER actually kick in. Seems to me it only kicks in once you get past 5000 and does it ever have enough time between 5000 and 6000 to ever get to the commanded AFR because of the 0.02 rate? I am also seeing there is a MAP Value of 15kPa that must be exceeded which seems easy enough to do, as well as 30% TPS as another threshold.

So I guess the real question is, when does PE actually kick in at partial throttle and at WOT?

I did my first HPTuners scanning earlier this week just to start "observing" things to see how the car behaves from the factory. I noticed during one of my 2nd gear WOT runs there was a good amount of knock and a bunch of timing pulled. I do not have my Wideband operational yet so I cannot speak to my actual AFR just yet. Being the noob I am I just want to figure out why the car is behaving the way it is from the factory before I start getting involved with tuning it myself. So why the knock during the WOT run.

As an aside I am running E10 93 octane, or I should say "up to" E10 based on the sticker at the pump and I also have a Roto-Fab CAI on the car.

[Trailblazin']

log your commanded afr, when it goes to ur commanded and the O2s ad Fuel trims get locked your in PE... u can vary the time it gets to kick in via the TPS%. 0 out all the other delays except for MAP if your FI.

[Racecar]

There is a setting for PE mode that is a % of throttle position. Mine is set at 50%.
The numbers in the factory PE are usually set pretty rich. When you start tuning your PE to lean it out, you also need to set the OLFA. Open loop fuel air. It also controls open loop WOT fuel.
I set my OLFA to all 1.00, then the PE controls all extra fuel for open loop.
If the LT trims are rich, it will carry that trim over to WOT/PE. If the trim is lean, it will not carry over. Good luck, then fun is just beginning. Don't lean out the PE too much at one time, you don't want the motor to run lean. Tune it and Scan before you run it too hard.
I could not get the file to open but it you have a lot of spark knock, get some better gas, or lower the timing tables by 1 degree at a time until you get rid of it.

[zimbobway]

OK, tolerate me as I walk through these scenarios and let me know if my assumptions are correct;

1. I am crusing along in 6th with MAP over the default 15kPa PE threshold but TPS at 18%, I give it a little more throttle to maintain speed on a slight uphill and TPS only goes to 28%. Here I would not go into PE Mode and would operate in Closed Loop.

2. I am crusing along with MAP over the default 15kPa PE threshold but TPS at 18%, I want to pass a car quickly, drop it down into 5th and give it a lot of throttle putting TPS at 50% (over the 30% TPS PE threshold default). The car would go into PE mode and start to works towars the AFR in the PE EQ Ratio table at a PE Rate of 0.02 (the LS3 default), it does all this while in closed loop.

3. I am cruising along above 15kPa and about 18% TPS and decide to drop it into 3rd and go to WOT. The car immediatley goes into PE Mode and Open Loop and works towards the Commanded AFR from the PE EQ Ration table.

4. Finally, trying to figure out the Delay RPM, I am in first gear on a slight downhill and for whatever idiotic reason I slowly work into the accelerator, never get the TPS past 29% but my rpms go above 5000 (the default PE Delay RPM), the car will go into PE Mode I am assuming to help protect the engine and do so in Closed Loop.

Thanks in advance for confirming or denying what is going on in any of these scenarios, it will really help me understand how the car is fueling under different conditions.

[DSteck]

To the OP, please see the reply I posted to your thread on Camaro5.com.

[zimbobway]

Thanks DSteck, saw it, I tried posting around to cover my bases

[BBA]

I always change those stock PE settings. The TPS setting is good, but the MAP setting can be changed to about 10-15 Kpa above normal steady cruise value (probably will want it set to between 65-75 kpa); set the PE enable and delay RPM to something closer to 0 (I set mine to 200 RPM), set enrichment rate to 2.0. These settings will give you good cruise mileage and PE instantly when you lean on it or stomp it and makes a huge difference.

Also, set your transient delay to 15 pulses and transient max mass to about 1/2 the present value. This will give better throttle response and reduce the black smoke when you stab it from low RPM/idle. (These transient settings will also reduce the AFR undershoot and subsequent overshoot).

BTW: Get rid of ALL negative timing values in High octane, low octane and base timing tables. This will decrease the response delay when you stab it from idle under load, as the sudden opening of throttle introduces a rush of air into the intake manifold volume which will throw the MAF to a high enough value to effeectively kill off the line timing advance. I actually ended up going with +15º in all the cells that were negative for the best response (will also lead you to easily smoking the tires from a stop light).

[SoCal]

Last week, I experimented with Enrichment Rate and Delay RPM. I have a G8 GT. My stock Enrichment Rate is 0.01. All of the tuning references talk about numbers up around 1.0+ I think the latest calibrations may have that setting scaled differently. 0.01 is a long way from 1.0!

With 0.0100, "Air Fuel Ratio Commanded" consistently took 0.850 seconds to ramp down from stoich to my PE target.

With 1.0000, it took no time at all. You couldn't even call it a ramp. It was stoich one frame and at my PE target the very next.

With 0.0550, it took about 0.151 seconds.

With 0.0325, it took about 0.250 seconds.

I don't know how quickly that really needs to ramp down. But I am pretty confident the 1.0+ rule of thumb does not apply to all engines/PCMs.

I also tried to see the Delay RPM setting in action. I set it to 3000. Picked a gear and went from cruise to WOT starting below 3000 and then again starting above 3000. I thought I might see the point where "Air Fuel Ratio Commanded" started ramping down change. I couldn't really tell a difference. But I also struggled to make sense of all of the PE enable conditions. It looked to me like the ramping down always started well after all the enable conditions where met. Definitely well after exceeding my TPS threshold of 48%.

Which TPS are you supposed to watch anyway? There are at least three TPS related PIDs given in %. And a similar number of pedal position PIDs. And if I remember right, none of them match the TPS shown in engineering mode on the dash. If I think to do it, I'll have to log all of them together. Maybe they are all the same.

I'm also interested in any further explanation of the Delay RPM. The easy answer is probably to just follow everyone's advice and drop it way down. I'm still curious what exactly it does though.

[blownsub]

There is a setting for PE mode that is a % of throttle position. Mine is set at 50%.
The numbers in the factory PE are usually set pretty rich. When you start tuning your PE to lean it out, you also need to set the OLFA. Open loop fuel air. It also controls open loop WOT fuel.
I set my OLFA to all 1.00, then the PE controls all extra fuel for open loop.
If the LT trims are rich, it will carry that trim over to WOT/PE. If the trim is lean, it will not carry over. Good luck, then fun is just beginning. Don't lean out the PE too much at one time, you don't want the motor to run lean. Tune it and Scan before you run it too hard.
I could not get the file to open but it you have a lot of spark knock, get some better gas, or lower the timing tables by 1 degree at a time until you get rid of it.

Dumb question here. Where is the OLFA table? I have a Magnusson tune in my Camaro that is pig rich. found most of the problem. Pe enabled at 5% tps. Anyone want to chime in on forced induction. Don't want lean it out too much, it makes wonderful power at the top, but my in-town mileage is 10 and below. Factory pe enable was 30% tps which i may go back to. Just bought a dyno I'm learning how to use so I can roll it and make changes.

[BBA]

Dumb question here. Where is the OLFA table? I have a Magnusson tune in my Camaro that is pig rich. found most of the problem. Pe enabled at 5% tps. Anyone want to chime in on forced induction. Don't want lean it out too much, it makes wonderful power at the top, but my in-town mileage is 10 and below. Factory pe enable was 30% tps which i may go back to. Just bought a dyno I'm learning how to use so I can roll it and make changes.

5% means PE is controlled either by RPM enable or MAP kPa setting. I like to find the cruise vacuum/kPa and set PE to come in at about 10-15 kPa above that value. This way you have PE when you need it and stoich when cruising.

[blownsub]

5% means PE is controlled either by RPM enable or MAP kPa setting. I like to find the cruise vacuum/kPa and set PE to come in at about 10-15 kPa above that value. This way you have PE when you need it and stoich when cruising.

Not trying to hijack this thread, I want to keep it on topic, I have same questions as the OP. So if tps is set this low (5%) then the pcm looks to map and rpm to enable? My map enable is 101kpa which I woul consider pretty good and the rpm is set to 800 rpm. Factory tune was 30% tps, 15 kpa and 5000 rpm. I gather from what you are saying the priority changes when tps is dropped that low so you can use kpa or rpm? which one of these becomes priority now? I know the tuner did the right things for California (50 states) compatibility with 91 octane, but we have 93 in Texas. I've retuned alot of trucks with maggies but this is my first car with a stick. I have alot to learn evidently! Thanks for your knowledge, it's greatly appreciated!

[BBA]

I never thought of it as priority but it makes sense the way you put it. PE comes in when all the conditions are met, and in your case is would make sense that TPS and RPM enable are already being met from the start, so once MAP is reached it will come on so you are being controlled mostly by MAP level.

[madvette08]

That scan reminds me of my car when it was stock lol. Timing from the Factory is set way to high on these cars.

PE enables when you have exceeded the delays. Above 5% TPS your in PE.

Ian

[blownsub]

That scan reminds me of my car when it was stock lol. Timing from the Factory is set way to high on these cars.

PE enables when you have exceeded the delays. Above 5% TPS your in PE.

Ian

Thanks Ian and BBA. Thats' kinda hwat I thought, but hte newer pcm's and operating system have/are evolving, who knows what they will add, change or delete. but this why I experiment on my own cars first (UGH!) so I don't blow up a customer's car. I'll try raising my tps enable a little at a time and see what happens. Thanks again!