Tip in bog, O2's read lean, lots of fuel added by pcm

[JasonS5555]

Hey GH,

Thanks, I'll try that change right now and see what occurs on the drive to lunch. I really appreciate the help with the injector variables. That's something that I've not used / tuned before.

Jason

[ElecTech]

Based on your LT1 32 file you posted, I would put the values you changed in the "Dynamic Airflow" sections back to stock and clean up your VE table and see if things get better. I rarely ever change the zones in the dynamic section, only the LT Fuel Trim sections. I would also try setting the "High RPM Disable" to 300 rpm and make it run on pure MAF to see if it gets better. That would, at least, point you in the direction of the VE table.

[ElecTech]

As for the SD OS, someone else can correct me on this, but I believe you can still use your maf. The OS just gives you a lot more to "play" with, as far as tuning capabilities goes.

The only custom OS that is designed to run MAF is the 1 Bar MAF - Enhanced and the only benefit to this is the RTT, I think. the 1 Bar MAP SD Enhanced is designed for SD only and gives you the Alpha-N table along with RTT and high octane timing tables.

[JasonS5555]

Hey Jamie,

Thanks, the VE tables are still a work in process. I've smoothed them out more in the latest few tunes. I'll try changing the dynamic airflow stuff back. It just seemed like those should be changed since I never see manifold pressures that low or rpm either since idle is at 900.

Thanks for the info on the custom OS's. What is RTT? I think I'll try to stick with the stock OS and see if I can make that work unless you see a reason that I should switch.

Thanks,
Jason

[GHuggins]

The only custom OS that is designed to run MAF is the 1 Bar MAF - Enhanced and the only benefit to this is the RTT, I think. the 1 Bar MAP SD Enhanced is designed for SD only and gives you the Alpha-N table along with RTT and high octane timing tables.

Awesome, that's what I thought. Just didn't want to lead Jason down the wrong road.

[JasonS5555]

Here is the latest tune. I haven't had a chance to log any data yet.

2001 LT1 037.hpt

Thanks a ton for the help guys. Its a lot better already than it was when I started this thread.

Jason

[mowton]

So as we are on the topic of injection boundary, my 2 cents is to make small changes and let the wideband readings after each change tell you if going in the right direction. As GH stated, the short circuiting or injecting while the exhaust valve is open will actually drive the wideband to a "false" lean. This is due to raw fuel being sent to the O2, instead of burnt exhaust. If you are going in the right direction, the wideband should begin to richen as you make changes to the EOI. Then you can begin pulling fuel out and this will move towards GH's lower IPW during idle.

Ed M

[JasonS5555]

Attached is a log with the LT1 037 tune posted above. The bog is essentially gone. If you drive like a goon who's never driven a stick, you can still stall it, but the driveability is way better. If I dial back the lower left corner of the VE table since it now appears that I'm a bit tip in rich, things should even be better.

032215 b.hpl

I also drilled an 1/8" hole in the TB IAC hole like the stock TB had. I'm pretty sure this means I need to re-run the idle air and reset the idle airflow table.

So how would I decrease the injector pulse width at idle? VE tables?

Thanks!
Jason

[ElecTech]

Attached is a log with the LT1 037 tune posted above. The bog is essentially gone. If you drive like a goon who's never driven a stick, you can still stall it, but the driveability is way better. If I dial back the lower left corner of the VE table since it now appears that I'm a bit tip in rich, things should even be better.



I also drilled an 1/8" hole in the TB IAC hole like the stock TB had. I'm pretty sure this means I need to re-run the idle air and reset the idle airflow table.

So how would I decrease the injector pulse width at idle? VE tables?

Thanks!
Jason

I wouldn't wrap yourself up in the idle injector pulse widths. It's going to take what it needs and most injectors are more consistent above 1.5ms anyway. Just get your fuel trims right and leave at that.

You will need to re-visit the base idle airflow since drilling the hole. The "Desired Airflow" the PCM uses is only a reference to IAC position anyway and doesn't directly reflect actual airflow of the MAF so you just have to get the Base Idle Airflow table to be close to the logged Desired Idle Airflow to keep things from chasing and flairing.

RTT stands for Real Time Tuning

[JasonS5555]

Hey Jamie,

Thanks. I figured as much on the idle airflow since the idle was hanging which it hadn't been doing.

I can see how RTT would be an advantage when tuning WOT with a WB. Are there any gottchas when going to the 1 Bar MAF - Enhanced OS?

Thanks again,

Jason

[GHuggins]

Jason I noticed where you were posting your corrections in an older 24x conversion post that you wound up at an eoi timing of 7.1? I was just curious as to where your pulse widths on your injectors were now and how much difference it had made on how it drives or acts?

I don't know if it was a member on here or on another forum, but anyway, he found that the most power and torque in the lower rpm's were achieved by injecting right before the intake valve was at max lift. This through his studies caused the most port turbulance for atomization and thus most power and torque to be produced and of course on top of that no fuel was being wasted out the exhaust valve. He was using an after market fuel system that allowed him to play with the injection timing while loading the motor on his dyno. Wish I remembered where I came across that... EVEN MORE SO, wished you could adjust injection timing with HP like that Any chance of this Bill?

Also with this being a manual trans car you could "power tune" your idle and almost completely get rid of any and all low rpm stumble or stall, if your interrested...

[JasonS5555]

Hey Greg,

That post just got updated. I moved up from 6.5 to 6.9 and then after that showed an improvement, and I read the whole EOIT thread and used the spread sheet, I moved it to 7.1 which moves EOIT to a little after the intake valve has been open for about 20 deg. The inj pulse widths got longer though. from 3.0/3.2 to about 3.5. Not sure why. The low RPM off the line driveability is as good as its been and the low RPM freeway cruise (1800 in 6th) is a lot smoother as well.

So it sounds like I may want to play with this further for power and driveability. I need to get my damn WB installed....

Power tune my idle? Very interested if it will help off idle driveability. How does that work?

Thanks!
Jason

[GHuggins]

Power tuning your idle is one of those things, like injection timing, that most people stray away from or won't even try because it goes against most peoples ways of thinking. However just like injection timing, as you have seen, you can see some pretty nice "driveability" enhancements and it's relatively simply to do... Right now your ecm is adding whatever timing it thinks it needs for "torque addition", which may or may not be helping it depending on airflow values and so on being spot on in the tune. However as we all know, these numbers are never "spot on"... Power tuning the idle is where you more or less take away a lot of the ecm's ability to add timing and dial it in yourself as close as possible while still leaving a reserve of about 10 degrees for any torque addition needed by the ecm.

For starters go to your idle advance table and take out 7 to 10 degrees of timing while still leaving around 6 to 10 degrees advance capabilities. Now go to your main spark table and add around 5 to 6 degrees to your idle areas up to whatever cylinder or map setting your engine idles at. Then blend the corresponding neighboring cells. You timing should now be withen a degree or two of your cruising 1400 to 1800 timing values. You can use whatever timing numbers best suits you, but it should be somewhere on the lines of that. I also like to multiply out the rpm correction timing tables to where the first numbers in them are around 2.4degrees. This further helps to "quickly" correspond to rpm dips. Don't be surprised if your now running pretty rich at idle and have to take out fuel in your VE and MAF tables. Remember fuel is also added if your unecessarily running too much timing...

Really think your tune is coming along nicely from what I read in your other conversion page.

[JasonS5555]

Thanks GH. I'll look all that over and tweak my tune some more. Yes, it has come a long way since I first started tweaking the 0411 tune after the 24x swap.

Thanks again,
Jason

[JasonS5555]

Just to update this thread. With 10 deg of overlap I've moved my EOIT so that at idle the injectors are not opening until the exh valve is closed (0.06" lobe lift). That made a huge difference and now the low RPM power and smoothness is vastly better. The values I'm using are boundary - 7.3 and normal 5.7. I also made the low ECT normal table the same as operating ECT. This seemed to really help the cold start off idle behavior.

Thanks again for all the help guys!
Jason

[GHuggins]

You know... You started this thread not knowing or to have never played with injection timing before. I honestly have to say, I think you know more about it than most on here including myself now Really glad to hear everything has worked out great for you.

I personally would love to sit down with the gm engineer that originally wrote the injector tables and see just how or why everything was done the way it was. Don't guess that will ever happen. But would be nice...

[JasonS5555]

Hey GH,

Very kind words. I doubt I know more than you do. I have figured out a few things standing on the shoulders of others on this forum. VERY glad I didn't have to figure it out on my own. I did add a cell to the EOIT spreadsheet that shows where injection starts. Just subtracted the cell showing injection time in degrees from the EOIT number. It helped me sort out the SOIT which may be more important for those with larger cams.

Jason

[capss9c1]

Thanks for all the great info as i am still dialing in my conversion, since i have a similar cam, would you mind if i tried your injector timing settings to see where it gets me? if u have any questions feel free to ask. maybe together we can perfect this conversion......

[JasonS5555]

What are your exact cam specs?

I've been using a modified version of sound engineers EOIT spreadsheet that has SOIT too. Then I look at the actual cam events.

I don't use any of the numbers in blue. I'll post another sheet that removes all comparison to the stock cams which for a big cam are really irrelevant. ONLY the numbers that I'm entering in pink at the top, and comparing the resulting numbers in green, SOIT and EOIT to the actual cam events which are shown below for 0.050 lift.

SOIT EOIT Worksheet.xls

Notice that the cam events shown are 0.050 lift events. My cam the exh valve isn't closed for another ~25 deg or so.

Also, I had been thinking that the normal table should be a flat value for a bigger cam. The stock normal table has the EOIT really early in the cold ECT cells because with NO overlap, they were dumping the fuel in early to give it more time to atomize. So again with a lot of overlap, this won't work.

Now I'm thinking that the cold normal cells should actually be a little larger since the PW will be longer. My setup as an example, boundary at 6.5, (950 cold idle, 900 hot) as an example, at cold idle I'm seeing PW around 3.3 ms and at hot idle its 2.7. So that would imply that cold cells should be 6.54 and hot cells should be 6.49.

Keep in mind all I've done so far is for idle and off idle clutch engagement. The above changes have worked wonders. I plan to get my WB installed within the next week and then WOT tuning may have some impact as well. It does feel from SOTP, that the above changes may have pulled some torque in the mid range....

HTH,
Jason

[anniversaryss]

What are your exact cam specs?

I've been using a modified version of sound engineers EOIT spreadsheet that has SOIT too. Then I look at the actual cam events.

I don't use any of the numbers in blue. I'll post another sheet that removes all comparison to the stock cams which for a big cam are really irrelevant. ONLY the numbers that I'm entering in pink at the top, and comparing the resulting numbers in green, SOIT and EOIT to the actual cam events which are shown below for 0.050 lift.

SOIT EOIT Worksheet.xls

Notice that the cam events shown are 0.050 lift events. My cam the exh valve isn't closed for another ~25 deg or so.

Also, I had been thinking that the normal table should be a flat value for a bigger cam. The stock normal table has the EOIT really early in the cold ECT cells because with NO overlap, they were dumping the fuel in early to give it more time to atomize. So again with a lot of overlap, this won't work.

Now I'm thinking that the cold normal cells should actually be a little larger since the PW will be longer. My setup as an example, boundary at 6.5, (950 cold idle, 900 hot) as an example, at cold idle I'm seeing PW around 3.3 ms and at hot idle its 2.7. So that would imply that cold cells should be 6.54 and hot cells should be 6.49.

Keep in mind all I've done so far is for idle and off idle clutch engagement. The above changes have worked wonders. I plan to get my WB installed within the next week and then WOT tuning may have some impact as well. It does feel from SOTP, that the above changes may have pulled some torque in the mid range....

HTH,
Jason

Reviving this

I am ecstatic i found this post. I AM fighting this same issue. I was was almost sure that injection timing was my issue here and this only makes me think so even more.

My 97 24x lt1 does ecactly as you explained.
So i dont believe Jason will respond but i kinda agree with his idea of setting the normal table for large cams at similar value across the the table so its not spraying so early.
If jason replys that would be great. But ill take any opinion.