Bones232

When the engine is cold I have to lean out the OL table to keep from drowning the motor. When the engine goes to CL (120*F) the INT/BLM take over and pull lots of fuel (~115). Once the motor reaches operating temperature (187*F) INT/BLM are now adding fuel (~145).

I've been working with the IAT/CTS blend factor in attempt to soften the effect of temp on the PW without much success. The problem with shifting the blend bias from iat to cts, or vise versa, is that if either of them move too much I end up with the same problem.

In my old 8746 there was a inverse temp look up table that appeared to define the amount of change in PW related to the temp term. Does this exist in EBL? Or am I going in the wrong direction here?

RBob

iTrader: (1)

There is an inverse Temperature term table in the EBL. It isn't in the definition files as I felt that it shouldn't be changed. Maybe? Should be changed? I don't know.

As to why you are having such a wide varience in fueling over temperature I'm not sure. What do you have for intake manifold heating, air intake location, and IAT location? From your description it almost sounds like there is not enough CTS in the blend. Try making the IAT/CTS blend all CTS and see what happens.

RBob.

Bones232

I'm running an open element, a non air gap intake and the IAT is located in a near stock position.

I usually run the I/C blend factor around 98% cts bias at low rpm and drop a couple of % as rpm increases.

Yesterday I set the blend factor to 0% to see what would happen. Through out the drive I purposely kept the car moving in an attempt to maintain a constant I/C (iat) value. The fueling didn't seem to change much during warm up. The cts went from 84-190*F as normal while the iat only changed from 84-90*F. BLM stayed in the 115 range through out.

Just before shuting the car down after my drive, I sat in the garage to allow the iat temp to rise. Fueling (int/blm) did increase as expected. However, I'll have to spend some more time with the blend factor favoring the iat to determine if this is an improvement or not. One data logging session, IMO, is not sufficient to identify a trend.

Bones232

Update, I've been tuning with the blend factor heavily favoring the IAT. I still experience the lean out when everything gets hot (190cts/100iat).

So, I went a little further. I disconnected the IAT and left the blend filter favoring the IAT. the temp comp in the BPW calculation should not change as the IAT defaults to 104*F when disconnected. As a result the motor still leans out when it gets hot.

The sPW does increase as the engine temp and BLM/INT rises. It would appear that this phenomenon is pointing to a mechanical issue of some sort. Could it be possible the gas in the fuel line is boiling (the fuel lines are near stock routing)? I've not experienced any vapor lock issues.

EDIT: I've already checked the fuel pump, lines, tank vents, ccp, etc.

alvanwie

Bones,

Been chasing a similar problem with the 8746 ecm. I kept thinking it was temperature related also. I am now conviced it is not.

What I believe is happening is the Baro is being calculated incorrectly during running. At start up Baro is read from the map sensor before the motor cranks. Then once running. when over 50% tps calculates corection to the Baro using map and tps. There is a table "Baro - Correction Vs. TPS" that is used to correct the map reading based on tps position. I believe the values in this table are set for the small bore tbi and need to be changed for the 2" tbi. If you look at the ecm for the 454 engine a completely different set of values are used.

Anyway, just thought there may be a similar issue with your EBL system.

Bones232

Did changing the baro calibrations help your situation?

EBL happens to spit out the BARO in the datalog. It seems to remain constant throughout the datalogging session.

I'm still leaning towards something mechanical. The pulse width in a given area actually increases during the logging session.

With all else equal you would think if the PW increases more fuel should be delivered. I would also expect that as an engine warms up the demand for fuel for a given afr/map/rpm would decrease. The opposite appears to be occuring

example:
Engine cold (150*Fcts), CL, 38-42Map, 1300rpm = ~1.3-1.5msec sPW
Engine warm (190*Fcts), CL, 38-42Map, 1300rpm = ~1.7-1.9msec sPW

I've also been chasing a fuel pressure flucuation issue when the engine is warm. Related????? Not sure...

appreciate the input...

by the way, what cam are you running?

alvanwie

I do not have definite results on the Baro yet. I disabled it from making any running corrections. Need time to do more logging.

In my case it is not IAT related. I have seen the BLM suddenly increase at idle with no changes in IAT.

It may be CTS related, thru the changes in spark advance causing a change in fuel requirements. Just another theory at this point that I need to verify. However, in my case when the BLM suddenly begin increasing I do not see a corresponding increase in pw or dc.

See my sig below for cam info.

alvanwie

Looking back through some log files I see times where at idle, suddenly the BLM begins to increase and will increase by about 10 in about 10-15 sec. During this time I see no corresponding change in pulse width and all the engine parameters remain constant IAC, IAT, CTS, SA, MAP, RPM, TPS.
So, why does the BLM need to change to keep the PW constant and the engine running the same???

Bones232

A couple of questions come to mind;
Does the blm return to its previous value after the 10-15 sec?

What is the INT doing during the event? Usually when the INT reads lean the BLM is sure to follow. If INT does not change, you may be crossing over to another BLM cell with a slightly higher value.

Do you have a WB? Curious if you notice a slight enleanment during this event. If so, it may be an indication that something is definately changing.

If the PW is not changing as you indicate, something must be dropping to make up the difference in the PW calc. Process of elimination may point you in the right direction. I believe the generalized formula for PW is;
BPW = BPC * MAP * ~T * AFR * VE * BVcor * BLM * DFCO * DE +-CLT


Do you have any idea what your setup puts out? How does it behave on the street? I'm lookin' at a similar cam but am worried about loosin too much low end torque (only 9.1 compression). Do your heads have screw in studs?

alvanwie

No, the BLMs seem to stay at the new value, at least as long as I continued to log.

The INT goes up a count or two and then as the BLM goes up it goes back to 128 and then starts again until it finally settles with the BLM up about 9-10 counts from where it started. And no it is not changing BLM cells when this happens.

Do not have a wideband. Just can not pin down what is causing this since it appears that the fueling requirement (PW) remains constant.

Dyno2000 says a little over 400hp and 450ftlb torque. No track or dyno numbers at this point. Low end torque is good, again Dyno2000 say over 400ftlb already at 2000rpm. With your compression ratio Dyno 2000 says you will be down about 20hp and 20 ftlb from my numbers. Also you may find the cam effects driveability a little more with the lower compression. If you keep your foot out of it it feels very mild on the street, but that is hard to do. Tuning for idle was initially tough and AE is a problem to get consistent results. Still running the stock pressed in studs. Only have a little over 1000mi on it at this point.