LT5 Info.., and 1228331 stuff in general.

[Bruce Plecan]

Not in any gm I know of.
Grumpy
   EE, ME, CS, CE, and spelling challenged


| 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 at teamzr1.com>
| > To: gmecm at efi332.eng.ohio-state.edu <gmecm at 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 at 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.
| > >
|