LT5 Info.., and 1228331 stuff in general.

[Mark Romans]

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.
>