Now here is more thoughts on Scotts theory:
I don't buy it, Here's why. I am 95% sure the 87-89 injectors are the same.
In most cases of a modified ECU or even an 87 to 89 ecu conversion the
Injectors are not changed (correct Rob?). The changed ECU software always
drives the injectors harder therefore they would fail sooner. The only way
I could see it be an injector failure is if:
The ECU conversions or 87-89 upgrade not only changed the fuel curve, but,
the way the injectors were fired. If I understood Scott correct, The 87
uses a 50/50 on/off pulse, with increasing frequency to drive them Harder.
Could the 88-89 change now drive them by increasing Pulse width duration?
Which in my mind, would definitely allow them to be driven harder before
failure.
Regards,
John
The 87-89 Starquest uses a 2 injector wet intake, throttle body system.
There is a Primary and Secondary of Mitsubishi manufacture with a possible
bosch housing. There sizes are 550cc and 1000cc Respectively.
John
-----Original Message-----
From: Jim Lill [mailto:jpl@vectorbd.com]
Sent: Wednesday, August 26, 1998 3:20 PM
To: John Goodyear
Subject: Re: Peugeot geniuses Help A StarQuester.
who makes the ECU and injection?
-Jim Lill http://www.vectorbd.com/users/jpl
On Wed, 26 Aug 1998, John Goodyear wrote:
> Fuel Injection Gurus,
>
> The Hot topic of the 87 Starquest fuel cut has surfaced again with, a new
> twist. Scott Lambson posted this asking for comments. I ask you to
> consider it as a possibility and comment. Please also take a look at my
> other message on fuel cut that went unmentioned.
>
>
> SCOTT:
>
> Clark posted a question as to why he was not experiencing the proverbial
> fuel cut in his 87. I have conversed with him about this before to which I
> had no idea why
> he has not been experiencing fuel cut. But, it got me thinking. I have
never
> had it in my 87 either.
>
> Now, I have been on these Starquest BBS about 4 years now and have had my
87
> for longer than that. I had never heard about a fuel cut until I got
Topends
> catalog and I bought it about the ECU needing upgraded but I could not
> afford to have my car down for 2 weeks. So I waited and asked some
> questions. Everyone
> on the boards kept telling me that the 87's had a fuel cut somewhere
around
> 14.5psi and the 88-89's was set somewhere around 18psi. I believed them.
> And, I
> proliferated that information.
>
> I have been searching the manuals for anything concerning something about
> the fuel cuts. I have found NOTHING. I have manuals for the 84's and 87's.
> (If you
> know of something please direct me to the page.)
>
> Which got me thinking even further. How would the ECU know when 14.5psi is
> met?(retorical) Anyone who still believes the stock boost guages is actual
> pressure
> or is even accurate, I can produce the schematics to prove them wrong. The
> boost guage is based on two sensors. Mainly the counts coming from the Air
> Flow
> Sensor(AFS). Secondary is the engine speed sensor. So as more air flows
> through the measurement tube more boost is shown. In stock configuration
> this can be
> fairly accurate. Unfortunately most of us modify these cars.
>
> You can get around the fuel cut by modifing the AFS but you also make the
> car run leaner. According to what I understand of the ECU operation, fuel
> cut is actually
> determined by pulses coming from the AFS or more specifically frequency of
> the pulses. At some set frequency the ECU initiates the fuel cut. Fuel cut
> should occur
> like this. Timing starts retarding, fuel trim stays the same and boost is
> cut back. Unfortunately, the ECU has no control over boost pressure other
> than to adjust the
> timing. The DSM's use a boost control solenoid the drop the boost when
> excessive knock or fuel cut is reached.
>
> Everyone that claims to have reached fuel cut explains it as a sudden
surge
> of non-acceleration which quickly corrects itself. In order for this to
> happen fuel would
> have to be cut. Most likely done by the ECU by not opening the injectors
or
> cutting the frequency driving them. This seems like a really bad thing to
> design into an
> ECU. But it is possible.
>
> The other thing that I would like to propose is that there is no fuel cut.
> O.K. this may be a shocker but I am starting to think we have all been
feed
> a line of bull. My
> hypothesis is this. Somewhere around 80% duty cycle, most injectors reach
> saturation or they will not cycle accurately anymore. This is due to the
> fact that there
> simply is not enough time left to open and close. Our injectors are a
> slightly different breed. My understanding is that they are run on a
50%duty
> cycle continuously
> but the actual frequency that they are driven at changes.
> _________ ________
> _| |_| |_ normal injector @ 80%
> _ _ _ _ _ _ _
> _| |_| |_| |_| |_| |_| |_| |_ Our injectors at saturation
>
> Our injectors reach saturation when the frequency gets high enough that
the
> time on and off does not allow the injector to open and close. So, what I
am
> proposing
> is that 'fuel cut' people are experiencing is not actually fuel cut but
> rather injector failure. Contrary to popular belief the stock injectors
will
> not get you over 250
> horsepower at stock fuel pressures.
> According to everything I have gotten from the experts the combined total
of
> the stock injectors will flow around 1250cc/min of fuel. Go to
>
> www.rceng.com
>
> There is some good explainations of fuel injector theory. And even though
> their site still says they sell injectors for the StarQuests they should
> tell you they won't.
> Maybe, a good pestering will bring them back.
> Anyways, the formulas there will tell you the stock injectors are a little
> weak even for the 250 horse range.
>
> I personally am running two things to correct the fuel problem. 1. A BCFPR
> which raises the stock fuel pressure at boost. This gives you some
expanded
> fuel
> capacity when you need it. 2. Larger injectors from RC Engineering.
> According to my calculations this should get me close to 275.
>
> I have talked to Topend about their 87 ECU and have not been able to get
any
> concise information. My assumption is that what they are doing is to add
the
> 88-89
> fuel maps and ingition curves. What they do physically is to add a
> daughterboard. If anyone has any proven info. let me know.
>
> Maybe I am way off base here but I figured I might as well post my
concerns
> as I would like to see a disertation as the the reality of an actual ECU
> fuel cut. I
> welcome any corrections.
>
> New Message:
>
> : Sorry about the ASCII stuff. It did not come across to well. Just
assume
> the top of the pulses are line up with the next line. The nomal injector
> should have big spaces on the on pulses and small spaces the off pulses.
>
> : On Off
> : _|-------------------------|_|------------------------|_
>
> : _|--|_|--|_|--|_|--|_ Ours
>
> : Heres another site at greddy.
>
> New Message:
>
> : At saturation
>
> : : off.........on...........off
> : : _|-------------------------|_|------------------------|_
>
> : : _|--|_|--|_|--|_|--|_ Ours
>
> : : Heres another site at greddy.
>
> : http://www.greddy.com/injectionsizer.html
>
>
>
> What Do you guys think? Is he way off base or could it happen?
>
> Below is A Question I posed back:
>
> : Scott,
> : A quick thought, Lets say topend was putting in the 88/89 fuel map in
the
> 87 ECU conversion. If your theory was correct, wouldn't the richer 88-89
> fuel map driving the unchanged 87 injectors cause them to fail even
sooner?
>
>
> Thanks All,
> John
>