How lean is it safeto in this table without getting in trouble with the engine?

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ZaphodB a.k.a Carl Andersson - zaphodb@faxancruisers.org
'89 Camaro IROC-Z 5.7L TPI - Mods under construction :-)
Custom ARAP Chip Under Development/180 t-stat, Edelbrock TES Headers,
SLP Airfoil, K&N Filters, Accel 8mm wires, Relocated MAT, AFPR @ 45 PSI

 

Depends on your exact combo..
You'll have to do plug checks.
FWIW, rarely can you run a V8 leaner then 15.8 at cruise. But even at that you can melt the motor.

 

That is what I thought..... I am going to do some more testing with the highway mode, but I am going to be careful with the A/F ratio, because I don't wanna ruin a perfectly good 350....

Have a chip with the Highway mode A/F table now varying between 15.3 and 16, and it seems to run stable with that (16:1 that is for the lowest load level in the A/F table), and I estimated the fuel consumtion to about 1 litre / 10 kilometres with the speed varying between 30-60 mph, highway mode enable set at 50 mph...

So my conclusion is that the highway mode is something good, but should be tuned with caution.... Now that there is a new version of the Winbin .ecu file maybe some more people will be interested in looking at this too!



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ZaphodB a.k.a Carl Andersson - zaphodb@faxancruisers.org
'89 Camaro IROC-Z 5.7L TPI - Mods under construction :-)
Custom ARAP Chip Under Development/180 t-stat, Edelbrock TES Headers,
SLP Airfoil, K&N Filters, Accel 8mm wires, Relocated MAT, AFPR @ 45 PSI

 

I have been runing 17.6-17.2 for a few months now with no problems. I DO have a functioning EGR which dilutes the mixture and makes the mixture less volatile than you would expect. The only thing I've noticed so far is burning less gas.

Give me another year of running this combo and I will give you a long term result. I do agree that the general condition of your motor is a major factor, especially your injectors and the EGR.

I have tried as lean as 18:1, but it was too lean for the O2 sensor to properly monitor and I noticed that my injector pulse widths on a "known piece of road" actually increased when I went this lean. I obtained the lowest injector pulse widths with 17.6-17.2 (at various KPAs).

 

I thought that Highway Mode was an open loop operation and that the O2 sensor was not used. Therefore, your VE or MAF tables and block learns had to be "right on" for highway mode to work properly. I have highway mode disabled right now for that very reason. In cell 15 (where I cruise on the highway) my block learn is around 122. The other cells are close to 128. Where did I get off track?



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'87 IROC 5.7l TPI - original owner!

 

PJ, you're not off track. Like you stated the ECM does not control the air/fuel mixture based on the output of the oxygen sensor in Highway mode. The sensor is still outputting a voltage, though, that corresponds to a lean mixture. Glenn is monitoring this output to get another window into the operating condition of the engine. After tweaking the MAF scalars I now see BLMs ranging from 124 to 130 across the board so I'm just starting to play with Highway mode fuel.