I'm working with 8F code mask for a 3.1L that has been upgraded to a 60 deg with a little more displacement and boost.

The stockers for the 3.1L turbo found in the Grand Prix were ~24 lb/hr. I have Deka 60s in my motor which runs and idles fine in openloop but I want to maximize fuel efficiency by running closedloop.

The searches have had me all over the place and I'm a little tired and frustrated and could use some guidance from those with experience.

What I know so far is to: adjust BPC relative to the stock injectors as if the 60s were in the stock motor, then compensate from there based on displacement increase over the stocker.

I also understand that larger injectors may open a little slower so the battery vs. inj offset table will likely need adjustments.

There's also a common problem with surging during cruise which I've run into that I would like to clear up unless the battery offset is the key.

I'd appreciate any organized guidance offered toward my efforts. I'll probably start with a base stock tune and move from there since my current tune is so different from OE it may be part of the problem at the moment.

 

What is the fuel pressure with the engine running and vacuum line off?

Zero out the short PW compensation table. Those injectors flow more at low PW's and you can't put negative values in the that table.

RBob.

 

Static fuel pressure is about 52 psi without vacuum.
Do you have the specific name of the table you are referring to above as it does not appear as such in the XDF under that title.

Thanks

 

Try this one:

At this address: $9B2

I just have to ask, why so much fuel pressure?

RBob.

 

Stock pressure for the later model 60 deg motors is about 56 psi, so about 50ish with a vacuum isn't all that bad, although I understand your curiosity about it. I have a custom offset ground crank in a 3900 to increase stroke so my displacement is about 4.2L and shouldn't be a problem.

Found the table and will give it a try tomorrow hopefully. Thanks for your help.

 

OK, yes, GM started to raise the fuel pressure with the LT1 engines. I was thinking that it also increased the delivery a lot. Here is the table data for the long/skinny Mototron/Deka 60's at 52 psi:

Injector Data Sheet: FI114961, 60 #/hr Deka Mototron 006

Fuel Pressure: 52 psi

Minimum PW @ 52 psi: 1.546

Offset Compensation versus Battery Voltage:
6.4 Volts: 2543 usec
8.0 Volts: 1602 usec
9.6 Volts: 1106 usec
11.2 Volts: 815 usec
12.8 Volts: 601 usec
14.4 Volts: 410 usec
15.0 Volts: 347 usec*

Flow rate: 69.3 #/hr

Short PW Compensation versus Pulse Width:
0.015 msec: -77 usec
0.244 msec: -68 usec
0.488 msec: -58 usec
0.732 msec: -48 usec
0.976 msec: -38 usec
1.220 msec: -28 usec
1.460 msec: -18 usec
1.708 msec: -8 usec
1.950 msec: 0 usec
2.197 msec: 0 usec
2.440 msec: 0 usec
2.685 msec: 0 usec
2.929 msec: 0 usec
3.170 msec: 0 usec
3.410 msec: 0 usec
3.660 msec: 0 usec
3.900 msec: 0 usec

The * value at 15 volts needs to be extrapolated into the GM table. Use the graph feature and blend it in to the actual values.

The surging is likely due to proportional gains. The AE is also likely PW based (I didn't look, but it is typical). Along the same lines is the BPC table values.

Change all of the stock values by the ratio of stock injector flow to the new injector flow. Then adjust again for the ratio of difference in the displacements.

That will rough in the tune rather well. Will need to fine tune from there.

RBob.

 

Wow! in all my years of school I never had anyone do my homework for me, I sure do appreciate that demonstration at a frustrating time such as the one I've been having. I really appreciate it.

 

So far following those guidelines helped tremendously for a good start. The BPW offset vs injector zeroing yielded negative results and the motor idled much better with values near the same as the OE settings.

I scaled:
BPC
VE
Idle VE
AE delta TPS
Bat Volt offset
Inj BPW offset

I discovered a dilemma that kind of explains why I have been unsuccessful at increasing openloop idle AFR. It seems no matter what I do the Idle AFR will not increase in openloop and hoovers around 11.9-12.5.

While in closed loop I made some drastic changes to the idle table and they did not appear to have any effect at all. I changed the same area in the main VE table and still no effect as expected while idling.

I wonder if I need to connect a signal wire from the clutch switch to the P/N pin address although TPS, Speed and Map values should tell the ECM when the car is idling.

It seems idle in openloop is controlled by something other than the idle VE table. In closedloop idle AFR hoovers around the commanded 14.7:1.

I'm certain I'm due for a plug change given what the current cheapies have been through, perhaps that will help smooth things out even more.