Thanks for the props guys. Actually, it was only by blind luck and some spare time messing around with some .bin files that I discovered there was an early version of chip programming used in the 94-95 3.4 DOHC systems that was compatible with tuning software already available on the market. (whereas the more common code mask used ($2E) isn't yet widely supported).
The 94 3.4 DOHC "early" code mask has a table defined in the programming for "IAC command air flow vs. RPM vs. current gear". On this table, the stock values had the IAC shutting off (commanding no airflow) during periods of mid-to-high RPM. This was a problem because the IAC can't move as fast as the RPM's can drop and stall out the engine when you push the clutch in during a decel. On the latest "test" chip I did for Mike, I told the PCM to keep the IAC opened at all RPM levels to see if we could prevent the stalling, and it appears this has "fixed" the problem.
Anyone running an earlier version of my 94-95 MAF-based 3.4 DOHC chip is more than welcome to send back their chip for a free upgrade to try this different code mask programming and see if it fixes any stalling issues they might have..
| | | quote | Originally posted by ltlfrari:
Dang, knew I shouldn't have sold the MAF from my engine
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Sorry you sold off your MAF, Dave. However, don't despair; the earlier speed-density based system is still capable of allowing your engine to perform to it's maximum potential; assuming the chip settings are correct for the configuration of the engine... Which brings me to my next point:
MAF vs. Speed Density Concerning the 91-95 3.4 DOHC engines
MAF-based systems have the advantage of being able to self-compensate for small/moderate mods performed to the engine. However, this only applies to the fuel delivery calculations; timing advance is still based on engine load and cannot be changed without reprogramming. The MAF-based systems for this engine also have a misfire detection capability which can help in diagnosis and are Sequential-Injector-Fire which helps slightly with efficiency.
Speed-density based systems have the advantage of not needing to use a "restrictive" MAF sensor (the ones the 94-95 engines use are not that restrictive; but they still do obstruct airflow to a degree). However, speed-density systems cannot compensate for mods done to the engine that increase it's need for more fuel; thus you will need a custom chip any time you mod the engine significantly.
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Just to be clear, there is only ONE system for the 3.4 DOHC platform that is 100% compatible with a manual trans, and that is the 91-93 3.4 DOHC 16149396 speed-density system. However, with these new discoveries concerning the 94-95 MAF systems, it looks like a lot of the issues that people were experiencing when trying to use a manual trans may be a thing of the past.
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power corrupts. absolute power corrupts absolutely.
Custom Computer Tuning | Engine Conversions | Turbocharging | www.gmtuners.com
[This message has been edited by Darth Fiero (edited 02-25-2006).]
