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

[Team ZR1 <teamzr1@teamzr1.com>]

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.