My BLMs go down from 126 to 118 when I let off the gas.

Should I tune these VEs?

For instance, I am cruising at 2000 rpms, and I have BLMs at 126, I go from 18% throttle to 9% throttle and my BLMs go down to 118. Should I change these VEs at from this KPA and RPM?

 

In my opinion and actual tuning, the closer the BLM is to 128 the better the system operates in all states of driving.

 

It strange, to me, because the BLMs are around 128 on moderate AE and when holding... then on DECEL, in gear, (no gas, 0% TPS), I get BLMs that go down to 120 sometimes down to 116.

Hence, my question.

These BLMs hold 120 even on Acceleration and upper rpms. Then if I am in neutral, and slowly stop, the BLMs go back to around 128.
Then the 128 holds on moderate AE until the cylce is repeated.

I feel like I am missing something simple like setting the code to Manual Trans instead of Automatic.

Anything else I should check?

 

Might try adjusting IAC to respond faster and get more air on decell, or reset idle with your mechanical screw holding the throttle open a little more and using less IAC.
If everything as far ad cruising is doing ok (like it sounds) it seems to me that you are just getting rich when slowing while rolling. A little more air may make the O2 happy.
Also maybe DFCO sooner? I'm not real sure on the DFCO settings though.
That's my thoughts anyway.
Jp

 

Maybe change the VE there at those kPa and RPM points, or if you have canister purge operating, it could be adding some fuel.

DFCO should only be used at TPS% less than about 3%, and with low MAP thresholds - like 23 kPA or so.

BLM is not a single value for all load and RPMs, rather the MAP and RPM table is broken up into different blocks and can have a different BLM at light load vs high load, and at different RPMs. The goal is to get the VE calibrated in each cell such that BLM does not have to stray far from 128 to achieve 14.7 closed loop operation. Your wording is a leading me to write this, so if you already know this, it's not meant to be condescending or anything, just for clarification.

Do you mean at 2000 RPMs at 18% throttle the BLM is 126, and at 9% it's 118? If so, then yes, look at the kPa for 18% throttle and the kPa for 9% throttle, and leave the VE alone where it's at 18% throttle, and reduce the VE where it's at 9%. Do so in smooth increments of course.

 

I dunno, I've had some problems with this as well. The same points that are rich as heck under decel are a perfect 128 under accel or steady state cruise. It even does this in open loop when I'm watching with my WB. Somthin funky there, and I don't think it's entirly ecm related.

 

That's what I'm saying, there's no such thing as "the same points" under decel and accel. They are all independant points.

 

That's what I am pursuing the different MAP vs. RPMs.

During AE or Cruise at 1500 rpms with 30 KPA my BLMs are 128.

Then if I cruise at 2500 rpms at 30 kpa my BLMS are 128, if I let off the gas, (maybe even below 3% so DFCO kicks in, not sure though) my BLMs go down to 120 back at 1500 RPMs at 30 KPA even though they were just at 128 BLMs when I was cruising.

Thanks.

 

Increase the amount of decel enleanment.

RBob.

 

Thank you!

 

And they are independent BECAUSE during acceleration, the acoustics in the intake manifold are determined by the intake_manifold+throttle+air_filter and 1 atmosphere pressure, while during decceleration (when the throttle is closed), the acoustics are determined by the intake manifold only and the air pressure is much lower than 1 atm. Anything that alters the induction acoustics will alter the VE, from closed throttle to open throttle and everywhere in between.

The effect would be more pronounced on an engine using acoustic tuning with equal-length runners (e.q. LB9, L98).

 

right, but, in this case, he's talking about 1500 RPM at 30 kPa, which is the same point on the VE table. TBI systems are very difficult to calibrate low MAPs and transients (including decel enlean (not DFCO - which is fuel cutoff, which shuts down closed loop)). Closed loop will often chase its tail. I'm not sure of the capabilities of the 730s decel enlean in a TBI application, but if you increase decel enlean (too much), you may find that it causes a slight to severe buck if you go from, say, 3000 RPM 40% throttle to 3000 RPM 10% throttle, if it's excessive enleanment. The buck would be caused by a leanout of course.
The main cause of the difficulty is the huge surface area of the manifold that'll soak up fuel at low RPM, high MAP, thus leaning out the mix temporarily until it stabilizes. That wetness also dries out during low MAP, which will richen the mix until it stabilizes. AE and DE are used to combat this, but TBI is sooo difficult to get perfect with simple algorithms, so I recommend getting it good enough, and reduce the main problems first (surging, bucking), then worry about BLM if it causes its own surge as it chases its tail.

 

Indeed, tuning a TBI with the 7730 is a PITA.

I get inconsistent BLMs depending on my driving style within five minutes of run time. If I drive it easily, I get BLMs at 120. If I take the EXACT same rout and drive somewhat aggressively, my BLMS will be at 126 - 128.

I would run the 7747, if I could find or make it run 4 injectors.

I found a driver setup for the 165 (I THINK). I don't have a clue what circuits they were talking about, other than it being MOSFETs... which makes me think of audio amplifiers...

 

You may need to work on the intake air temperature corrections. May also need to work on manifold & intake-air heating/cooling. What you describe is most likey caused by the manifold temperature varying. More throttle cools the manifold more which brings the BLMs up.

But then again, is the tune already good-enough?

RBob.

 

Interesting you talk about the IAT sensor. Howell, originally had the IAT next to the computer inisde the cabin!

My BLMs are fairly close (closer than Howell had it).

My AE is closer, but not enough. I tried changing the Delta TPS vs TPS, this solved A LOT of my tip-in issues. Now I seem to have issues with AE AFTER the TPS moves. So I looked at my DELTA MAP vs. MAP. This seems to flood the engine too easily.

I am thinking I should either change my TPS Scale factor constant, or my MAP VS. TPS Delta.

Then again, perhaps there is something easier to use to overcome all of this using the table REF INjector ASYNCHRONOUS Pulses (there is eight in this table). Thinking like a TPI, I could see where only the first injector reference pulse should have a large number and the other 7 should be .50 (I think that' how it is in AXCN).

But thinking as a TBI, perhaps 4 of these REF ASYNCHRONOUS pulses should be used for a larger multiplier???

 

I'm having similar richness issues in my 6E mask L98.
There are 6 decel terms in the mask. Can anyone tell me which applies?

 

When I tried to tune my low rpm low kpa areas to 128 blm, I got a low speed stumble going from idle to low TPS. I hade to richen those areas up. Thats what my engine whanted..

 

It's lonely in a MAF world