Re: LT5 Info.., and 1228331 stuff in general.

[Swayze <kswayze@bellsouth.net>]

i even read in car craft that the knock
sensor can be switched out essentially
with a 100 ohm resistor( for harder
launches on race gas).
byE
Mike S.

Mark Romans wrote:
> 
> John:  I seriously doubt the code was re-written.  It's much easier to just
> flag an error code off or on.  Or set the enable temp or mph too high so in
> effect turn it off.
> If you compare your bin to a 90 all the changes should be in the first 1000
> bytes if no code changes were made.  If there are more changes, then further
> research will be needed.
> Mark
> -----Original Message-----
> From: Team ZR1 <teamzr1@teamzr1.com>
> To: gmecm@efi332.eng.ohio-state.edu <gmecm@efi332.eng.ohio-state.edu>
> Date: Wednesday, January 19, 2000 12:11 PM
> Subject: Re: LT5 Info.., and 1228331 stuff in general.
> 
> >The secondaries are a On or Off function, at about 2,200 RPMs ( if the
> Valet
> >key is turned off ) it kicks in .
> >The Diacom shows a on or off, no percentage.
> >
> >Question is, since the S.S has no secondary vaccum pump, no valet key, did
> they
> >re-work this solely by ECM coding or
> >modifiy the ECM,  or both ?
> >Also to protect the LT-5 certain hard or soft ECM error codes on a stock
> ZR-1
> >will shut down the secondaries, thus since the S.S
> >is hacked, did they also chop code out to ignore this ?
> >for as an example as I have been told my header/sidepipe exhaust system is
> the
> >loudest many have heard, thus
> >the knock sensor has to be going nuts ( as I say in Diacom trace last
> night )
> >but is being ignored by some code since the knock counter is
> >ramping from 0 to 255.
> >
> >Thanks,   John
> >
> >Marc Randolph wrote:
> >
> >> On Tue, Jan 18, 2000 at 06:02:32PM -0500, Bruce Plecan wrote:
> >> >
> >> > | They are operated through vacuum solenoid, but assuming the system is
> >> > | operating properly, they open all the way up in one motion - there
> >> > | aren't various stages of being open as far as the ECM cares, it
> >> > | is either open or not.
> >> >
> >> > Have you used a PWM meter on it under load to actually observe it's
> >> > operation?.  Just asking since I have seen things mistated before.  Or
> is
> >> > this a quote from somewhere, and you have no direct info?.
> >>
> >> I have not measured it with a PWM while it was on a dyno
> >> (or driving down the road!).  It would be difficult, but
> >> not impossible.
> >>
> >> I base my statement on a multitude of different sources, all which
> >> agree (or point to) that the ECM considers the port throttle either
> >> open or closed.  I'll outline only a few below :-)
> >>
> >> 1. Tim Holland, a lead engineer for the LT5 project on the Lotus side,
> >> said the following, "... the ECM will signal the ports to open, and
> >> wait .5 seconds before turning on the secondary injectors.  As
> >> the secondary injectors share the same drivers as that of the
> >> primaries, the pulse width signals are halved when the secondaries
> >> operate."    So, there is no mention here of partial opening, and
> >> in fact, the stated operation is that the ECM must wait for the
> >> port throttles to open before it turns on the injectors,
> >> .5 seconds later, at which point the pulse width is halved.
> >> This also makes sense from a fuel and flow stand point -
> >> the port throttles are below the fuel injectors, so if they
> >> were not opened all the way, the fuel would hit the port
> >> throttles and drip onto the back of the valve.  That doesn't
> >> sound like a good idea to me...
> >>
> >> 2. A Diacom capture of the LT5 running on a dyno or driving down the
> >> road reflects that the port throttles are either open or closed.
> >> There is no % open reading.
> >>
> >> 3. The wiring diagram of the LT5 confirms that the primary
> >> and secondary injectors are controlled by the same driver in
> >> the ECM.  Considering the left and right side port throttles
> >> do not necessarily open the exact same amount for a given vacuum
> >> (I have observed this), and given there is no sensor to indicate
> >> to the ECM what % the port throttles are open, the ECM would
> >> have to guess as to what pulse width to use if partially
> >> open port throttles were to be supported, and it would almost
> >> certainly not be correct for at least half the engine.
> >>
> >> 4. The wiring diagram of the LT5 confirms that the port throttle
> >> solenoid is controlled by a single switch in the ECM to ground.
> >> The other side of the solenoid is tied to the main fuse block.
> >>
> >> 5. The description of an error codes confirms it, by saying
> >> "When the driver has the engine power switch in the FULL power
> >> position, and pushes down the accelerator pedal far enough, and
> >> if various input sensor parameters are within an acceptable range,
> >> the ECM turns `ON' the secondary port throttle valve solenoid
> >> allowing vacuum to open the valves."  The diagram for this function
> >> also shows the solenoid being controlled by a switch to ground.
> >>
> >> 6. And lastly, a logical reason: A variable pulse width, variable
> >> opening solenoid would be too complex and wouldn't provide any
> >> benefit.  The main reason for the port throttles is to increase
> >> low end torque.  As the rpm and air flow rises, the torque curve
> >> of the engine with the port throttles open quickly approaches
> >> the torque curve for when the port throttles are closed.  Why
> >> involve a TON of complexity when you could just open the port
> >> throttles all the way and be done with it?
> >>
> >> In summary, I'm quite sure they don't partially open. :-)
> >>
> >> Have fun,
> >>
> >>    Marc
> >>
> >> --
> >>   Marc Randolph     -    mrand@pobox.com    -     PGP keyID: 0x4C95994D
> >>      If you have any info on the mid-60's car called the Bill Thomas
> >>        Cheetah, or know anyone that might, please contact me.
> >