Got an almost stock 92 Roadmsater (TBI 350CI LO5) with freed exhaust.
To improve things and possibly get better mileage I installed an ECM with EBL Flasher.
Mileage with OEM ECM was between 20 and 16 MPG (Highway - Daily Drive).
Last tank made only 13 MPG after VE learn (and new fuel pump at 12 PSI)

Only remark, I drive with EGR disconnected and disabled from teh BIN file.

Is the low MPG due to no EGR ??? would have expected better mileage in any case !!

 

The EGR can affect mileage. The low mileage can also be caused by low spark timing. IIRC, a lot of timing was pulled out of the tables trying to get rid of false knock. Try the original L05 tables, the more aggressive ones first.

If the old fuel pump was bad enough that can create better mileage from the engine running so lean all of the time.

Check for excess AE, that will kill mileage.

Lean cruise mode will also help. Make sure DFCO is operational.

Of course, with it running so much better with the EBL, the foot tends to get heavier...

RBob.

 

I agree all the points you raised.
Thought about lean condition due to bad fuel pump but forgot about going back to aggressive timing of previous LO5 BIN files.
Will flash it back ASAP

during VE learn I drove without 4th range gear sometimes and also forcing it in 1st and 2nd gears ranges so that all type of speeds are tested. But I was soft and then I am a bit surprised to do 229 miles on a tanks instead of the usual 300 miles on daily drive (360 on highway). The worst I ever did was 270 miles up to now with no use at all of 4th speed range (was testing mpg in all conditions)

229 is bad

 

I flashed the previous BIN for 92 Caprice (file 2020)
Did VE learn but already I could not esome knocking.

With the BIN file BATJ (2020a) I never saw knocking.

with the 2020 the knocking appears when you accelerate.
The SA moves from 18-20 deg down to almost zero and some knocks are counted each time you give throttle.
In cruise it is OK.

Do I have to lower the SA Vs MAP / RPM ??

 

Sounds like it is knocking when you pull out from a stop? If so then look at the launch mode SA table. This one:

SA - Launch Mode

With the heavy car and tight converter may want to zero out that table.

If the knocking is at all speeds when accelerating, then reducing the SA in the main table(s) is the way to go. Look at the Areas of Spark Knock display, and click the Peak radio button.

Subtract half the peak values from the SA table(s) where the knocking occurs. Smooth it into the surrounding cells.

RBob.

 

Well it is more into speed when you put it in load.

For example today at steady 50 MPH in final gear range and TCC locked I was at around 1400 RPM. giving some light throttle would produce knocking (SA going from 21 deg to 14 deg on the WUD ...)

Got to see in detail what is different between files 2020 and 2020a ...

 

It would be all around helpful for you to re-connect & re-enable your EGR, both for knock and mileage concerns. I don't understand why you are not using it.

 

I have disconnected it because it is required for doing VE learns.

I will re-enable it when I have modified my Spark Advance tables for no knock and when VE learns will be donne on all type of driving (DD, highway, city, etc ...)

To come back to the SA I have lowered a bit the SA values in teh table as per RBob advise () and this morning I had very little to not knock.
At many points I have only 1 or 2 knocks counted during a 30 minutes drive. But yet the Peak SA is at least 1 for those points. As I understand thi is the minimal value do I have to lower the SA at those points where knock is very minimal or is it acceptable to leave it as it is ?

 

I would leave it as is. With only 1 - 2 counts and peak retard of 1*, no need to reduce the timing any further. Mainly two reasons for this. The first is that by removing additional spark timing mileage and performance is hurt.

Second, it may not even be real knock. The knock filter will sometimes report knock when there isn't any.

RBob.

 

Ahh this I understand.

It would only be fair that mileage evaluations wait till you have it tuned in and EGR reconnected.

 

I can understand that but in my idea the EGR is just a stupid thing which adds burnt gases to the intake to lower T° and pollution - thus decreasing the quantity of gas required in the engine and then reducing power (even if reducing slightly MPG too). I wouldn't expect the EGR disabled to cause so bad MPG. And I was counting on the EBL to improve this same MPG.
To summarize I did not consider the EGR was the problem but more the setting of my BIN file ... why this post and why RBob is involved !!!

Will keep the SA where it is with little knock, will only move it down at some high values !

Do I have to understand that the best is to be at very very little knock at most points of the table ?? ... for power and efficiency ? or can it be harmful for the engine ?

 

Heavy knock under load is what causes trouble. A few light knocks here and there are not an issue.

RBob.

 

keep in mind fuel will cause quite some change as well, summer fuel runs great in the wife's GP, i average above ~32MPG, but the same route with winter blend? a little above 25...

 

Cold here now ... Winter blend !? never thought about that before.

I have adjusted the Spark Advance table a couple of times to get something high enough with no to little knock thanks to Rbob method.
Now I use the TRIP data from the EBL software during my drives to se what is going on.
I realy feel the acceleration is more crispy with the EBL ECM.
So I accelerate the car faster on short dstance to get into cruise and lean mode sooner (but without getting into Power Enrichment mode ).
Makes a big difference in the MPG with this heavy car on my drives where it is a lot of stop and go with random traffic.

I will do that during one full tank to see the difference but I already managed to get 19 MPG average on my way to work ...

Fact is that I could accelerate without thinking with OEM ECM bacause it was not sending so much gas to the engine I believe (less power too of course).
Now car drives better but it requires to be used with wisdom unless you can afford gas.
(Gas is 1.38 EUR per Liter today ) = 7 USD for 1 US Gallon ...

Will continue to refine the SA and other settings related to economy !!!
But still thinking about improved aluminum head, headers and 9C1 camshaft
Still think that in cruise I can get even better with those parts. No ??

 

Any significant drop in air temperature can have the same effect on combustion and its result(in this case spark knock) as too much timing. I would re-evaluate your IAT timing tables. The advantage to the egr is to add an inert gas to the combustion cycle. This means that essentially a leaner AFR and an increase of spark timing can yield higher cylinder pressure(more torque) without an increase in combustion temperature which is normally associated with non egr assisted increased timing settings.

So, in a nutshell, yes the economy drop and knock increase is a result of disabled egr and cold air temperatures.
Chris

 

Still on same tank ... 220 mile done, tank has got some reserve good !

had an issue with lower radiator hose (NEW now, I love it when I have the parts "on the shelf")

When I finish this tank I will re-activate the EGR to see the change.