Is it possible to get a rock steady idle? idle was more stable prior to running the Aeromotive VAFPR. no surge under load. slowest speed with minimal load some bucking(manual trans). pulsates 825-900 rpms in rhythm and 35-50 MAP at idle. manual trans. Prior to VAFPR the "synch" P/W was considerably lower at idle as expected. 80 lbs injectors at 19 lbs fuel pressure not changed.
What I am seeing in logs is SA stable at 20deg as I leveled the tables all around idle. Running OL idle so using the coolant based A/F tables @ 13.6/1 around 60 VACand 68-80 C temp.
WB shows idle A/F moving around 14.0 to 14.7/1. Proportional gains tables reduced 10% from EBL.bin. IAC disabled and inlet plugged.
No vac leaks.
cam 224/230 @.05 114 LSA

this is what I have changed in .bin:
ronsbin EBL
INT 02 window for fast RL 100 130
airflow displace scaler 350 306
PRP for idle 3 5
PRP offset idle 9 20
INT mean RLand rich 02 and lean 02 i am 20% higher
PRP gain multipler i am 80% higher
PRP durations vs 02 error i am 8% higher
PRP offset for airflow i am 50% higher
IAC TF gain i am 50% less
IAC TF min step 1 4
IAC TF tps% req 1 2
IAC TF max 12 120
I thought I had IAC TF fueling disabled but cannot locate where I did that.

Shouldn't have any issues with idle quality while running a VRFPR. Instead of leveling the SA table around idle can set the option bit for the set idle SA value. Then set the idle SA parameter to 20 deg.

The idle should be moving around some as the stabilizer SA takes affect.

When you say the idle is pulsating, at what rate? Fast or a slow roll.

Can you post an analysis graph picture of it.

RBob.

Thanks. I will say slow roll. I cant post here at office but I will post tonight when I get home.

I do see the inj PW oscillating in WU following the WB report of changing A/F and the RPM as well.

I checked .bin. ID SA was set(checked). And Idle state SA was already set to 20 deg.

OK, with a slow roll with the change to a VRFPR, it may be not enough proportional gain. The fuel pressure is lower which lowers the injector flow rate. Now the prop gains have less affect. Check to see if the INT is now oscillating. If so, then need more prop gain.

Other thing to try is to set open loop idle (an option switch). Then see if the RPM still rolls. If so then bump the idle stablizer SA up until it goes away. Then switch back to closed loop and go from there.

My engine used to do a terrible RPM slow roll at idle. That is what caused me to add the idle SA stabilizer functionality to the code.

RBob.

fuel pressure is reduced to 14 lbs with the VAFPR functional. 19 lbs otherwidse. Idle is OL. Idle stabilizer bump up? In logs idle never budges off 20 SA. I will increase it and see how it reacts.

Sorry cant find idle stabilizer. constants or tables?

These four tables. Values shown as used on a semi-ratty cam'd engine. Idles at 850 RPM and about 60 KPa MAP.

IAC opening fuel pulse, single value: AE - IAC Opening Fuel

RBob.

test

Ron,

Stock prop gains are too much for a modded motor. And yes its very possible to get stable idle using VAFPR. In fact, its much easier than running 20psi and dealing with PW that's too short. Not to mention the throttle response.
And my cam was a lot more ratty than yours with a 108LSA/54d of duration.

Note the values I listed in original post:
Fisrt number was what was in my last .bin and second is stock EBL

INT 02 window for fast RL 100 130
airflow displace scaler 350 306
PRP for idle 3 5
PRP offset idle 9 20
INT mean RL and rich 02 and lean 02 i am 20% higher
PRP gain multipler i am 80% higher
PRP durations vs 02 error i am 8% higher
PRP offset for airflow i am 50% higher
IAC TF gain i am 50% less
IAC TF min step 1 4
IAC TF tps% req 1 2
IAC TF max 12 120

As far a prop gains I believe I am reduced cept for these:

PRP gain multipler i am 80% higher
PRP durations vs 02 error i am 8% higher
PRP offset for airflow i am 50% higher

Which should I consider changing?

I did change back to stock EBL on all the above and adopt the idle stabilizer values just RBob posted. That helped somewhat. I will reduce PRP for idle and offset idle to what I had previously and give that a try tomorrow. Please comment.

I tried to post my datalog with a zip but I recd "failure". I think I need to do a specific short idle log as the file may have been too large.

You mentioned that the ECM is running open loop idle. If so then the proportional gains are inactive. Same with the INT.

Is the vacuum to the VRFPR steady? It may be that where the vacuum is being picked up is causing the fuel pressure to fluctuate.

RBob.

I have a 1995-1996 7.4L TBI. The port I use is in front of TBI on the drivers side. At idle I believe the FP is constant at 14 lbs. 19 not connected to vac. With the MAP(log) changing how can the vacuum be considered steady?
Years back I used a nipple at the brake booster fitting. Might that be a better source?
So proportion gains do not apply at idle. But idle stabilization SA changes I did did help somewhat. I may move the vac source.

Bob,

I made the same observation on a similar thread a few months ago. Ron said he was running O/L and I commented then that Prop Gains wouldn't affect anything. As you know, I was running C/L for idle and PT.

It is when in open loop, there is no prop gain. If your idle is set for open loop then prop gains are turned off during idle. Prop gains are only active when the ECM is in closed loop.

How much does the MAP vary at idle? Then again it will be varying because the idle speed is varying. Did you set the IAC Opening fuel to 0? Should if the IAC is disconnected. Also check the AE PW in the data log. Maybe it is set to add fuel too easily. I've had it where the MAP AE was adding fuel on occasion. Made for a jumpy idle.

RBob.

Update. As I stated the idle stabilization was helpfull. Prior it was EBL.bin for IS values and now I adopted those values you posted. It is better but I still believe there is room for improvement. I was thinkling of raising those values a tad? I need to do a short log at idle and post it. Will do soon. This morn I did a long log(20 minutes). I upped idle speed slightly with a turn of TSS this morn. I have no IAC control. IAC inlet is totally plugged. IAC TF fueling is reduced to alomost nil. That is another issue as I have had no luck with the various combos of wiring suggested. I did not work on that yet this year. I believe I have a post by RBob with a suggestion that I will try. Idle speed commanded to 750 but controlled by TTS. . At end of log I have a fully heat sunk intake and I see idle MAP moving 35-57 and RPM 1000-550 and sPW 1.6-2.5 during event.

cold start same issues and WB shows reasonable enrichment as coolant based.

As far as monitoring vac should I place a "t" in vac line to VAFPR and monitor vac at idle and the move the vac source to brake boost vac and do same? I already have that fitting tapped for the nipple and currently plugged.

I checked again last night for vac leaks and cannot find any. When the TBI unit and manifold was installed it was done by a pro . I did spray carb cleaner arond base and I cannot see any rpm response. Gasket to TBI is GM and specific for 1995 TBI.

Well I came accross a thread that questions BPC- FILTER. I think it states EBL.bin is like 33%. Just for the heck of it I looked at mine .78%(<1.0%). EBL.bin was same??? I never thought much of it. Dom says his was 50% then bumped to like 60%+. Others commented theirs was 50% or so. Could this be the idle surge? Higher filter values reduce the response of the change in BPC. I will reread that post and look at RBobs graphs.

Looking at the data log it is a lean surge. There are some areas of the VE table that need to be increased. Check the area of 700 - 900 RPM, 45 - 35 KPa (the lower KPa at the higher RPM).

Then increase the values there. When the AFR moves from rich to lean the engine will first lose RPM. Then as the AFR furthers leans out the RPM will surge upward.

At this point the engine can either shut off (continues to go lean) or catches and recovers (gets additional fuel).

You mentioned the IAC fuel pulse. With the IAC disconnected set that value to 0. Otherwise it will contribute to the surging.

RBob.


{edit: looking at some calibrations, a BPC filter of .78% is way too low. I've been using about 40%. You may wan to change that first and see what happens with the surging. It may be from the BPC not changing in step with the fuel pressure.}

I have the BPC filter now at 60%. That has helped.
I will do as you state on the VE tables.

What you suggest might also help in another area. I drive same route home from work. As I exit X way at 50 mph I approcah the street and if light is go I make a turn and at that point the throttle is closed and I am in 2nd of 5 gear. RPM is 1000-1200 and MPH is 5-10. I then get a serious lean bog(WB 20.0/1) and car wont go. If I accelerate harder it bucks and eventually recovers. Or I must down shift to first at a crawl and hit gas. Do I need more fuel in VE tables at higher map as well?

Now will my Learn remove fuel from those areas I just enrichened when in CL or do you feel Learn will not see them? Should I set my CL qualifier for a higher MPH so as to run off those OL tables under 10 mph?

Thank you.

Another Q Please...

I am idleing OL. Those tables are already rich it my OL tables @ 13.8/1 all around surge areas. Is there a relationsship between OL tables and VE tables? I thought not. OL-AFR vs VAC. 60vac=40 kpa correct?
I have that table at 56C-104C; 70-60-40-30 VAC; all with 13.6/1 in table. I recall I already covered the lean condition possibility earlier this year.

WB shows 14.8-15.4/1 during idle. I believe WB to be accurrate but may be pulling in some fresh air as sensor 18 inch behind collector. So 15.4 may in fact not be that lean.

The PW equation includes both the comanded AFR and the VE%. So even though the commanded AFR is 13.6:1, the VE table needs to be adjusted to provide that AFR in the exhaust.

To convert the MAP KPa to vacuum in KPa, subtract the current MAP value from the barometric MAP KPa value. You can get this at key-on, engine-off (the MAP reading). Or from the Dump File as the BRO column.

RBob.

I made the mistake yesterday of changing 2 variables. I cranked the TSS a tad and enrichened the VE tables as you suggested around idle. Now it idles smooth at 900 rpms and the WB shows 14.0-14.3. So the enrichment of VE helped. I will drop idle speed with TSS a hair as I may have gone too far. The 7.4L TB is very sensitive there.

Also I added fuel in VE to cover that lean spike-bog-bucking on a low rpm(1200 pull in 2nd). That did not help. I amm using spark table from EBL. It may be engine has no TQ at that low RPM and air flow is minimal at that RPM. I may just need to keep rpms up by dropping to first gear. Is this an indicator that I should add MAP AE?. The slow change of TPS% may not add enough AE fuel as I accelerate in 2nd G. Would this trigger MAP AE as MAP surely changes as TPS% goes from 0-50 slowly?

Ron,

I think I had the BPC Filter set to 70% at the end of the day. It contributed to a much crisper throttle response.

I have it set at 65% now. Idle at 900 rpms is now smooth. If I try to set idle at 800 rpms with TSS it continues to move 600-900 rpms. Enrichening the VE did help but not totally. I will double check possible vac leak at TB unit. I did that many times now. I doubt the manifold is leaking. No IAC and inlet plugged. So next step is to move the vac line from TB unit to the brake booster(?) vac source at pass rear of manifold where I had my first GMVAFPR sourced. That I began last night. Point of interest pulled off the FPR gauge to move to diff location(cold air kit needs room!). While at it and found no leakage of gas at open port on reg. Just initial ounce or so. For reasons unk overnight it starts to leak-drip-drip at open port. WTF? My garage is epoxy floor so I have a puddle like you would not believe! I open door with GD opener from outside and lucky I did not blow the house. Garden hose to rescue. Now my vette and wifes new car smell like a refinery. She not happy.

Update. Again I changed two variables. Moved the vac line from TBI unit to brake booster with nipple installed. Has to move the FP gauge to make room for cold air so disturbed the FP. Previously when I added the vac assist I kept the FP at 19 and vac pulled it to 14. This time I did it backwards and set the vac pressure first. In doing so I find that car idles better at 16 lbs than 14 with vac line attached. So set to 15 and I will assume my WOT pressure is now 20 lbs which is max spring allows. Idle is much better. Was at 900 B4 with TSS and now dropped to 800 rpms as well. I did not change the TSS. WB shows enrichment at idle as expected with higher FP. Much better.