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  #11 (permalink)  
Old 08 Oct 2003, 01:32 pm
Cool Cruiser
 
Join Date: May 2003
Location: South Bend, IN.
Posts: 473
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Rosscoe,

I sell 100 unleaded and 110 leaded fuel ay my performance shop.
Many import racers around here blend my 100 octane and 90 or 93 octane pump gas. Many think race gas will make them faster. I hold a training class to teach them that without compression and camshaft profiles, they will go slower on race gas.
I proved my point last month. I took my PT with 87 octane and did my reliable 15.29 1/4 mile pass. I then switched to straight 100 octane and ran 3 tenths slower! I don't have the compression for 100 octane with my 2002 PT.
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  #12 (permalink)  
Old 08 Oct 2003, 01:43 pm
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Location: Lansing, Michigan, USA.
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Hi MX-5,
Do you have a way that I can contact you?
I don't see an e-mail address. Thanks.
Herschel
1 517 487-5308
My e-mail address is: jessiebell@voyager.net
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  #13 (permalink)  
Old 08 Oct 2003, 09:02 pm
Cool Cruiser
 
Join Date: May 2003
Location: South Bend, IN.
Posts: 473
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Mr. Irons,
I sent you an e-mail.

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  #14 (permalink)  
Old 08 Oct 2003, 11:25 pm
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Quote:
quote:Originally posted by MX-5



The PT knock sensor is not read any time the throttle is over 80%. At that point, the PCM goes open loop and follows the preprogrammed fuel/ignition strategy.

If you hear pinging, you are already 5 degrees too far advanced on the timing. Damage is being done before you ever hear it.
Actually, the knock sensor is active all the time - especially over 80% throttle. Turbo engines can't live without knock sensors.
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  #15 (permalink)  
Old 09 Oct 2003, 10:33 am
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Location: South Bend, IN.
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3bar,

Better check the service manual.

Here's page 8I-12 of the 2004 service manual:

KNOCK SENSOR
DESCRIPTION
The knock sensor is bolted to the cylinder block.
The knock sensor is designed to detect engine vibration
that is caused by detonation or preignition.

OPERATION
When the knock sensor detects a knock in one of
the cylinders, it sends an input signal to the PCM. In
response, the PCM retards ignition timing for all cylinders
by a scheduled amount.
Knock sensors contain a piezoelectric material
which constantly vibrates and sends an input voltage
(signal) to the PCM while the engine operates. As the
intensity of the crystalÂ’s vibration increases, the
knock sensor output voltage also increases.

The voltage signal produced by the knock sensor
increases with the amplitude of vibration. The PCM
receives as an input the knock sensor voltage signal.
If the signal rises above a predetermined level, the
PCM will store that value in memory and retard
ignition timing to reduce engine knock. If the knock
sensor voltage exceeds a preset value, the PCM
retards ignition timing for all cylinders. It is not a
selective cylinder retard.

The PCM ignores knock sensor input during engine
idle conditions. Once the engine speed exceeds a
specified value, knock retard is allowed.

Knock retard uses its own short term and long
term memory program.
Long term memory stores previous detonation
information in its battery-backed RAM. The maximum
authority that long term memory has over timing
retard can be calibrated.

Short term memory is allowed to retard timing up
to a preset amount under all operating conditions (as
long as rpm is above the minimum rpm) except WOT.


The PCM, using short term memory, can respond
quickly to retard timing when engine knock is
detected. Short term memory is lost any time the
ignition key is turned off.


The PCM considers anything over 80% throttle as WOT. The AC compressor clutch is disengaged and the PCM goes into open loop.
This info is directly from the PT service manuals.
I am a performance and driveability specialist. This is what I do.

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  #16 (permalink)  
Old 09 Oct 2003, 11:07 am
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Join Date: Mar 2003
Location: Renaissance Festival, TX.
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Quote:
quote:Originally posted by MX-5

3bar,

Better check the service manual.

Here's page 8I-12 of the 2004 service manual:

KNOCK SENSOR
DESCRIPTION
The knock sensor is bolted to the cylinder block...
If the knock sensor voltage exceeds a preset value, the PCM
retards ignition timing for all cylinders. It is not a
selective cylinder retard.

The PCM ignores knock sensor input during engine
idle conditions. Once the engine speed exceeds a
specified value, knock retard is allowed.

Knock retard uses its own short term and long
term memory program.
Long term memory stores previous detonation
information in its battery-backed RAM. The maximum
authority that long term memory has over timing
retard can be calibrated.

Short term memory is allowed to retard timing up
to a preset amount under all operating conditions (as
long as rpm is above the minimum rpm) except WOT.


The PCM, using short term memory, can respond
quickly to retard timing when engine knock is
detected. Short term memory is lost any time the
ignition key is turned off.


The PCM considers anything over 80% throttle as WOT. The AC compressor clutch is disengaged and the PCM goes into open loop.
This info is directly from the PT service manuals.
I am a performance and driveability specialist. This is what I do.
Is it possible the short term KR memory isn't allowed at WOT and that the long term KR memory is referenced by the PCM at WOT??? I agree with 3bar, KR is most important at WOT!!! I don't do this for a living, so forgive me if it appears I'm questioning you're professional abilities -- I'm not.
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  #17 (permalink)  
Old 09 Oct 2003, 11:24 am
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Join Date: Jun 2003
Location: Alvaton, GA, USA.
Posts: 1,162
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kidturbofan - Don't be so sure. They just started selling low-sulfur gas here in the Atlanta Metro Area, and in 45 counties in North GA.Here's an article in the AJC:

http://www.ajc.com/metro/content/metro/0903/16fuel.html

I live in South Metro, but luckily I am just across the line in a county that has neither emmisions inspections, nor low-sulfur gasoline.
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  #18 (permalink)  
Old 09 Oct 2003, 01:25 pm
Cool Cruiser
 
Join Date: May 2003
Location: South Bend, IN.
Posts: 473
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Quote:
quote:Originally posted by Steve03GT
Is it possible the short term KR memory isn't allowed at WOT and that the long term KR memory is referenced by the PCM at WOT???

Nothing is read at WOT in open-loop.
The PCM is preprogrammed with a very conservative fuel/ignition strategy. It's set so far rich that you will never get any pinging with the correct fuel octane and stock drivetrain.

I see up to 37 degrees total timing advance up to 80% throttle. As soon as it goes open loop, the most the PCM will allow is 24 degrees advance. (imagine turning your distributer back 13 degrees !!! )
The reduction in timing at high RPM is better for top-end power anyway.
The powertain diagnostic manual (not the general service manual) explains all of this in further detail.

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  #19 (permalink)  
Old 09 Oct 2003, 10:09 pm
Cool Cruiser
 
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Location: .
Posts: 347
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Strangely enough, I work for Chrysler as a turbo engine engineer - and that bold-faced portion of the manual is wrong. The short-term knock retard is always active (above a minimum rpm and MAP), and if it has to pull more than a pre-set amount of spark - it trips into long-term.

I will try to get that inaccuracy fixed for next year. Also, the only sensor not functional at WOT is the O2 sensor - which is to say the fuelling isn't closed-loop but charge air temp, ambient air temp, coolant temp, throttle inlet pressure, manifold absolute pressure, barometric pressure, vehicle speed all contribute to the spark and fuelling.
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  #20 (permalink)  
Old 09 Oct 2003, 10:36 pm
Cool Cruiser
 
Join Date: May 2003
Location: South Bend, IN.
Posts: 473
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Better get the editing pen ready....
I have all the service mand diagnostic manuals from 2001 through 2004 PT Cruisers.
That's 10,000 pages of info.
That WOT info is in both the genaral service manuals and the powertrain diagnostic manuals.
I find it very hard to beleive that they have mis-printed it for 4 years.

I submitted that the torque spec for the spark plugs was wrong in one section of the 2001 manual. They made the corrections the following year.
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