Hello/Beat that dead horse again! clarification

[Mark Romans]

Unless Caroll supercharging set the rev limiter to a different rpm, the
stock prom is set at 10,000 rpm's.  WIth batch fuel injection (165 ecm) you
can support more hp with smaller injectors than you can with sequential fuel
injection.
The idle variation is (In all likelyhood) due to how the spark map is
configured.  I had this problem at one time.  The engine load value (LV8) is
fluctuating which make the ecm read from different parts of the map with
different spark advance, so the ecm is constantly chasing the rpm as the
advance changes.  With a supercharger the stock intake system will spin more
rpm's than it will normally aspirated.

You can't just raise the idle speed.  It plays havoc with the ecm.  You also
have to adjust (At least I did) the following items.

1) RPM where higway spark kicks in.  (at a light load at 800 rpm's the ecm
puts in up to 8 deg more timing advance because it thinks it is driving down
the freeway, this is to enhance fuel econ. On my car I could just brush the
clutch out and the engine would stall because of the highway spark the iac
would retract to get the idle speed down.  The load would change, the ecm
would pull out the highway spark and the iac couldn't react fast enough,
this made driving in traffic REALY SUCK!)
2) DFCO, decell fuel cut off needs to be adjusted
3) Stall saver spark and fuel rpm's need to be adjusted.

It's all inter-related.  I am just now getting my driveability to where I am
happy with it with over 300 prom versions so far.

Mark
-----Original Message-----
From: BluVette <bluvette at scarcorvette.com>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Saturday, October 30, 1999 7:39 AM
Subject: Re: Hello/Beat that dead horse again! clarification


>OK guys, let me reword the original message and clear up a few points along
>the way.
>
>I designed and built and engine. I designed the cam. ACCORDING tot he CAM
>GRINDER and HIS computer, that cam is good for 600-650 HP, with all other
>factors taken into consideration such as heads and the rest of the
>modifications done. *I* limited the engine with 30# injectors, so if there
>was any possibility of the stock computer, with a chip in it that has
>already been modified for the supercharger.  I'm a mechanic, not an
>electronics engineer. Please, whenever possible, put your replies into
>laymens terms, and that would help a bunch!  :o) Thanks.
>Now, back to my original problem. When the engine hits 5400 rpms, it just
>stops. I was told on another list that the computer limits the rpm's at
5400
>on a stock L-98 enine in 1989. BEFORE the modifications, with only the
>supercharger, it did the same thing. I really need to spin this engine up
to
>at least 6000....so, does the computer limit the rpm's at 5400 or is
>something else doing it?  It did it with the old stock injectors, and i
>would have thought that the engine would lean out at a higher rpm with the
>new 30# injectors.
>Next problem is the idle. It is hunting between 500-700 rpms. The cam is on
>the radical side, along with custom made full roller 1.6:1 rockers. I HAVE
>to raise the idle up to about 800-850 rpms, as it dies right now when
coming
>to a stop about 1/2 the time, especially when the engine has been running
at
>WOT, and then letting off the gas, it dies almost immedatly.
>I am sure that there are other factors to take into consideration that I
may
>not be aware of as of yet. The engine is also equiped with water/alcohol
>injection, just ahead of the throttle body to help eliminate detonation,
and
>that combined with the lowered compression ratio has done a GREAT job, and
>no knock or detonation is apparent, even under full boost conditions, so I
>don't *think* that the advance curves need to be played with any more than
>they may have already been altered by the custom chip that is already in
>place.
>
>Someone on the list suggested swapping out the computer with one from a
>turbo GM car. Good idea, but, just HOW would I go about this, and is it
>compatable with an 89 Corvette onboard systems already in place?
>
>Inquiring minds want to know :o)
>
>Thanks to everyon that has been involved in this thread to this point,
>pleasae be patient and I will get up to speed.   TIA!
>-Barrett
>SCAR Corvette & Performance
>1010 W. Hwy 131, Clarksville, IN  47129
>(812) 941-0839
>bluvette at scarcorvette.com
>www.scarcorvette.com
>
>