So my cam idles at 68-70 kPA. And I want to make sure PE ramps in as cleanly as possible from lean cruise. I am setup for OLSD at idle and CLSD at cruise.

Right now, I have PE enrichment enable MAP setting to come on above 50 kPa, my Enrichment Ramp In set to 4 and TPS cold threshold as follows (stock hot table copied to cold with nothing in the 0-1600 cells):

0.0 0.0 0.0 0.0 64.0 64.0 64.0 64.0 55.0 45.0 36.0 26.0 26.0 26.0 26.0 26.0 26.0 26.0 26.0

I figure the TPS threshold is okay, but I'm wondering if I should bump my enable MAP setting to something closer to 70 kPa and whether I should just leave the enrichment ramp in to 1?

1 is how it was stock, and I'd like PE to engage as fast as possible. In older posts I saw, it was said that 1 was near instantaneous. If that's true, how can you speed it up to be faster? Also, I saw in those older threads that stock was 0.2 and that's not true in the later versions of HPT. So, I don't know if something changed along the way?

Any thoughts?

 

With 0 in the 0-1600 cells, doesn't that mean to enable at TPS 0 (closed)? I thought you are supposed to set it to 100 to keep from PE commanded at too low RPM. I've tried different settings of ramp between 1 and 4, currently set at 4. Only difference I see is one or two cells of too rich or too lean (depending) turning the transition to PE being enabled while going to WOT. But that's all.

 

Whenever the TPS is at zero, PE will be triggered, and by default, PE is open loop. I also have PE commanded to 1 which is stoich. I had to take counts out my VE table pretty good tho. I could take it down to .9 I suppose. Same for my OLEQ table as it picks between the richer of the two. That means I could then add values back to the VE table so it doesn't look like a cliff falling off to help with off-idle transitions.

 

That's an interesting approach. You're forcing OL at idle by using PE at low throttle input? That's to keep the o2 sensors in closed loop from messing with idle because of long-tubes, big cam, etc, correct? Then you're running closed loop above 1600rpm while cruising and back to PE (OL) for WOT?

 

That's the idea. High overlap cams and longtubes play hell with O2s at idle. But they are very good at stoich, especially at elevated engine speeds where the cam and headers become more efficient. So, I want to be able to use them for lean cruise. But then under WOT conditions, the MAP and IAT is all I need to keep fueling in check since the VE table has been tuned with a wideband. I've disabled longterm fuel trims so it doesn't screw with the enrichment.

At this point, I'm just trying to tweak how PE comes back on for smooth transitions and instantaneous throttle.

 

Are you trying to do lean cruise or are you calling stoich lean cruise? The only way I know how to do a true lean cruise on a f body is with a custom OS is why I am asking.

 

I have the 1-Bar Speed Density OS. Don't know if it allows it? Haven't seen anything.

And I mean slightly lean. Like 15:1-15.5:1.

What's the best way to accomplish this? Playing with the commanded A/F in the OL EQ table, which obviously, while in OL this works well, but once it switches to CL...O2 switchpoints?

Here is how I set the car up:

1. set PE to 1.0 up till 1200RPM
2. set TPS enable PE to 0 up till 1200RPM
3. set open loop EQ to 1.0
4. disable LTFTs
5. set PE MAP enable to 50kpa
6. set PE enable delay RPM to 0 and Ramp In Rate to 4
7. disable the P0131 and P0151 DTC codes
8. disable STFT open loop enable
9. Set MAF fail frequency to 0 Hz
10. Set P0101, 102, 103 to No MIL Light and unchecked the SES light
11. Enable Closed Loop IAT at stock 93 F
12. Set O2s for Rich/Lean switch points at 300mV for leaner readings (albeit a bit of a workaround - and more for getting decent readings with the longtubes)
13. Set Stoich at 14.14 for E10 gas

This essentially commands something around ~15:1 at cruise/light throttle and my PE enrichment takes the commanded to 12.1:1 at peak torque (1.165 EQ) and 12.4:1 at peak power (1.140). However, the switching points are more for the longtubes that trying to command leaner cruising.

If I kept in OL, I just command the OL EQ to whatever I want. And I'd probably do a .95 multiplier in the OL EQ table at low MAP readings and watch the wideband for any adjustments to the VE table for changes in commanded A/F and actuals. However, if I'm in CL, which I fear I would be at say 2000 RPM cruise at 80, then the fuel trims would be corrected and fuel would be added to get me back to stoich, correct? This is where the O2s and the 300 mV switch point come in to "trick" the PCM. Albeit unreliably.

I suppose, this is where the custom OS would come in handy? And now that I think about it, the 1-Bar SD OS doesn't seem to have anything for this in HPT. I know EFI Live has this feature...

 

That's why I just run OLSD all the time and make adjustments as needed. I can never get the o2s to work well at idle, and at cruise I like to command .9 OL EQ for a lean cruise in the low MAP area in my 'cruise rpm zone'. So I leave the STFT disabled in OL as well. I'm actually going to just remove the o2s and run without them now. 2,000 of OLSD miles later and a change from summer to fall and it's still doing exactly what I want. Really wish HP Tuners would let us enable lean cruise on all computers and vins...I mean, it's right there!

 

It's an EPA thing from what I understand. It doesn't make any sense. If car manufacturers could command a lean cruise, you'd get better mileage. The downside as I understand it? Emissions. But using more fuel with less emissions is a net gain of zilch. It just costs us more at the pump.

In my Trans Am, I don't care about fuel economy. But I'd like to reduce the amount of needlessly burned fuel in it. In my daily driver, I do care, and it's dumb that I can't get better mileage from the factory. Europe, Asian, and Australia all allow it and the General makes use of it there.

 

Can't you just start with an os from one of those cars then? Or does hp not support it?

 

I don't know. HPT in the past has said they won't do it because it is a direct violation of EPA rules. But as far as I know, the entire tuning suite is a direction violation of EPA law...

My entire car is a rolling middle finger to the EPA.

 

I have messed with lean cruise with the custom os in efi live on a few of my vehicles. Its very time consuming to setup, you have to use a wideband, its a small window of what helps vs hurts a/f wise and every vehicle is different.
I made a custom PID to log fuel mileage in 5mph increments. I would then adjust the a/f by .1 and set the cruise control at 60, 65, 70, and 75. I did this from 14.7-15.7 and them looked what netted the best mpg. Then had to adjust the lean cruise to turn off when the engine got into in load over just normal cruise. After all this it netted me 1mpg over my normal tune. I tried the same setting in my brothers truck and it lost mpg. IMO the amount of time it takes to do lean cruise the gain isnt worth it. There are a ton of variables of course but where I live it just doesn't help enough. If you dial your timing and your ve table in where your fuel trims are +-3 % your going to get about as good as fuel mileage as your going to get IMO.

 

Shouldn't you be pushing it up closer to 16.4 to net the most efficient lean burn? I'm using lambda 1.12 right now with great results (16.4 AFR with E0, 15.8 with E10).

 

When I went leaner the mileage dropped even more.

 

How much timing did you add when you went leaner? I found that I had to add 6-8 degrees in order to get my TPS back to a normal level. Any more than that and I started to surge and have knock.