I'm wondering what is a normal/safe afr under part throttle if the engine is boosting? Not that I'm doing this but if a person were to eliminate the boost bypass valve, the engine could build boost at low throttle and not be into power enrichment because the tps is low. I don't have a 3800sc so I may be way off base but would it be safe running 14.7afr under boost if the throttle was low?
I don't like seeing 14.7:1 or anything leaner than 11.8:1 AFR with even a small amount of boost. There are qualifiers in the OBD2 L67 PCM tune that can be set to make the system go into PE mode with low TPS based on cylinder load - if you want to set it up that way.
In any case, whenever boost pressure is present, I like seeing nothing leaner than 11.8:1 AFR. I know people say "12.0" AFR is the magic number, but that's the knife's edge absolute leanest you ever want to run with boost which will give you absolutely NO margin for error.
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That's what I was expecting, this is a custom installation so I'm thinking about adjusting the bypass valve to open later and help assure I'm into PE when in boost. It isn't running yet, I'm just thinking things over for when I'm ready to fire it up.
1998 s10. I had pcmforless do the tune and ordered a maf translator gen 2 for some at home adjustment and wideband tracking. That's what got me thinking about this because I'll need to set up the tracking but if I command 11.8 and the PCM is still commanding 14.7 I don't think that battle will end well. I am hoping after I get it running well I can send It in for a final tune and just use the gen2 for the wideband.
the BBV does nothing to change your boost curve. PE will be enabled around 40% throttle which will start to command 12.0 ish AFR.. 60%ish + throttle will command in the 11s depending on RPM and "time in PE".
1998 s10. I had pcmforless do the tune and ordered a maf translator gen 2 for some at home adjustment and wideband tracking. That's what got me thinking about this because I'll need to set up the tracking but if I command 11.8 and the PCM is still commanding 14.7 I don't think that battle will end well. I am hoping after I get it running well I can send It in for a final tune and just use the gen2 for the wideband.
Ok, I guess I should have asked these questions earlier:
1) What engine are you using in this 98 S10? 2) What transmission? 3) What SERV NO is on the PCM that is running it all?
Ok well that complicates things. I thought you had a 3800 SC.
The 98 4.3 PCM is not boost friendly at all. Spark timing tables in that OS are governed by 1-bar MAP sensor values, period, and I don't think there is any way you can change that (ie: I don't think there is a 2-bar MAP code patch available for these PCMs).
Fueling, on the other hand, is MAF based and you have more wiggle room there. But in the 98 4.3 PCM tune, there is a PE table that gives you adjustability based on throttle % - so that may be useful. That having been said, it doesn't look like there are any cylinder load or MAP qualifiers for PE mode (only TPS %) so you are probably going to have to play it safe and set the min TPS qualifier for PE mode really low. Also, make sure the PE delay is turned to 0. You don't want any delay going into PE mode with a boosted engine.
IF you could run an 01-02 4.3 Vortec 0411 PCM in this 98 truck, you would be better off since that PCM can be set up to use MAF only for all spark and fuel calculations. Or, you can spend the extra money with HP Tuners and get one of their 2 or 3 bar speed density OS patches for the 0411 PCM (running the 4.3 engine). The only thing I don't know is if the 0411 PCM will work with the BCM and IPC in the 98 S10 (if it has these computer modules).
It is a common upgrade to switch to the 411 PCM. I didn't realize the 3800 went into PE so early. I'll have to look into that. Thanks for the help guys. I'll probably have to post in the other cars section but I'll let you know how it goes, hopefully in a week or two.
Thanks for that, it seems obvious I'll be back in for some adjustments. I may even bring it to you Ryan. I just don't trust the local guys here. I did see that zzp sets PE to 35% on their supercharger conversion kit. Looks like 50% will be way too high. Especially if I ever hook up a trailer, the truck is already heavy. The PE vs baro table looks interesting but with those numbers it must not engage PE but simply allow it.
[This message has been edited by joshua riedl (edited 05-09-2014).]
