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ECM programmers -- look inside please. by ryan.hess
Started on: 02-24-2004 11:45 AM
Replies: 8
Last post by: ryan.hess on 02-25-2004 12:43 PM
ryan.hess
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Report this Post02-24-2004 11:45 AM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
Here's the deal. I need to find out how to change the pulse width of the injectors, i.e. add more fuel. GM issued a TSB for my car to replace the injectors with ones that "flow richer at a low pulse width".. and they cost $700. I am looking to just up the fuel flow at "low pulse widths"... I realize I could perhaps change the VE table at low rpm/low map, but wouldnt the computer over time realize that, and change it back to a 14.6 A/F ratio? How can I do it without the computer compensating?
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Maetrix66
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Report this Post02-24-2004 01:27 PM Click Here to See the Profile for Maetrix66Click Here to visit Maetrix66's HomePageClick Here to Email Maetrix66Send a Private Message to Maetrix66Direct Link to This Post
I haven't gotten my AutoProm yet, so I haven't had a chance to play with this. I do know where you can find the answer. Go to www.60degreev6.com, and post in the computer tuning section, put the name "Mechanic" in the subject so he sees it. He may be in here, since he has a tuboed 3100 in his 88 fiero, but I don't know his handle here. He wrote (or co-wrote) GMPCM, so I am sure he could answer your question.
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Cooter
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Report this Post02-24-2004 04:48 PM Click Here to See the Profile for CooterSend a Private Message to CooterDirect Link to This Post
Do you have access to a scan tool?
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Pyrthian
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Report this Post02-24-2004 04:57 PM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianDirect Link to This Post
why do have to do this in the ECM? most people get more fuel by either raising the fuel pressure, or using higher flow injectors. both of which are much cheaper than $700. Is this a Fiero or some other car?
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ryan.hess
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Report this Post02-24-2004 05:58 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
 
quote
Originally posted by Pyrthian:

why do have to do this in the ECM? most people get more fuel by either raising the fuel pressure, or using higher flow injectors. both of which are much cheaper than $700. Is this a Fiero or some other car?

As far as I know, doing either of these will work until the ECM "relearns" the engine... Also, raising the FP and/or using high flow injectors makes it rich across the whole board. I was looking for specifically raising 500rpm - 1500rpm *only*. Edit: 3.4 DOHC engine... also, I may have found the problem. Fixing the symptoms would have helped, but fixing the root of it all is better long term. Keep you posted.

[This message has been edited by ryan.hess (edited 02-24-2004).]

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Raydar
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Report this Post02-24-2004 08:39 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarDirect Link to This Post
 
quote
Originally posted by ryan.hess:

Here's the deal. I need to find out how to change the pulse width of the injectors, i.e. add more fuel. GM issued a TSB for my car to replace the injectors with ones that "flow richer at a low pulse width".. and they cost $700. I am looking to just up the fuel flow at "low pulse widths"...

Not sure if this will be useful or not...
I have heard that, in Fieros, disc type injectors, even with the same lb/hr rating, will tend to flow more than pintle type injectors at low pulse widths; i.e., at idle. This was because the disc type injectors respond much more quickly to the pulse than the pintle type, resulting in a longer effective "on" time.
This was actually given as a drawback to using disc type injectors in Fieros. Was supposed to cause a hunting idle because of the increased flow.


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Raydar
88 3.4 coupe.

Coming soon...
88 Formula, presently under the knife.

[This message has been edited by Raydar (edited 02-24-2004).]

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stevegibbs
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Report this Post02-24-2004 10:43 PM Click Here to See the Profile for stevegibbsSend a Private Message to stevegibbsDirect Link to This Post
Get an SAFC and you can tune many rpms not just low ones. It will work on your car. ebay price aruond $200 for them and have many different parameters to adjust to change injector pulsewidth

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Pyrthian
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Report this Post02-25-2004 08:47 AM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianDirect Link to This Post
the "pulse width" is not a set number that applies to all RPM's. the ECM learns the fuel requirements for different RPM's, I think at 200 rpm steps, and constantly adjusts by O2 readings. Are you saying you want the motor running rich at idle? Is this to keep a turbo spooled up more?
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ryan.hess
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Report this Post02-25-2004 12:43 PM Click Here to See the Profile for ryan.hessClick Here to Email ryan.hessSend a Private Message to ryan.hessDirect Link to This Post
 
quote
Originally posted by Pyrthian:

the "pulse width" is not a set number that applies to all RPM's. the ECM learns the fuel requirements for different RPM's, I think at 200 rpm steps, and constantly adjusts by O2 readings. Are you saying you want the motor running rich at idle? Is this to keep a turbo spooled up more?

No, it's to prevent it from stalling. GM determined that under low RPM/ high load conditions, that the 3.4 DOHC needs more fuel to keep from stalling. Hence, they put out some $120 injectors (x6) in a service bulletin. I'm trying to figure out how I can bypass that expense... Tuning the ECM seemed the logical choice, but I'm open to other options, including keeping it in open loop if necessary (it never stalls in OL)....

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