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Whats the limitations with boost an 98' PCMs again?

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Old Nov 29, 2010 | 06:51 PM
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Default Whats the limitations with boost an 98' PCMs again?

Did a search and surprisingly came up dry! I remember back when I was more in the FI game that tuning a 98 PCM for boost in 2-3 bar had limitations. What is the deal exactly when working with a 1998? Thanks!
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Old Nov 29, 2010 | 08:15 PM
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Only custom OS available is HPTuner's 2bar OS; good to 15-ish PSI before it's blind.
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Old Nov 29, 2010 | 09:07 PM
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Okay so I am good to go with 2 bar on the 98 pcm.... past 15 psi and I need to swap to 99+ or an aftermarket unit?
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Old Nov 30, 2010 | 10:59 AM
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Originally Posted by Superman09
Okay so I am good to go with 2 bar on the 98 pcm.... past 15 psi and I need to swap to 99+ or an aftermarket unit?
Yes its either that or scale everything down (PITA)
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Old Nov 30, 2010 | 01:28 PM
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HP Tuners offers the custom 2 bar operating software.
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Old Nov 30, 2010 | 01:36 PM
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It's 14.7 psi... Same difference I guess..
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Old Dec 2, 2010 | 01:33 PM
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Can someone clearify this for me.. does this mean if I go above 15psi I will need to use HP tuners custom OS but if I stay below I'm ok with factory PCM?
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Old Dec 2, 2010 | 01:39 PM
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There is a custom operating system that HP Tuners flashes in the stock/Factory PCM that allows the VE (maing fueling table) to see up to 210KPA~.

You can exceed that KPA reading, but youll need to be creative with tuning. Ive been 20psi with the stock 98 pcm, and had to get creative with fueling, but its possible.

The PCM physically cannot see more than 15 psi boost, so like frost said, its blind past that.
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Old Dec 2, 2010 | 01:49 PM
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Originally Posted by FrankieD
Can someone clearify this for me.. does this mean if I go above 15psi I will need to use HP tuners custom OS but if I stay below I'm ok with factory PCM?
You need HP Tuners custom OS to tune it.
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Old Dec 2, 2010 | 02:39 PM
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I just re-pin the harness and go to a 99+ pcm and use efi live cos#3 on bigger 98 turbo cars. Its makes life so much easier.
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Old Dec 2, 2010 | 02:53 PM
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Originally Posted by FrankieD
Can someone clearify this for me.. does this mean if I go above 15psi I will need to use HP tuners custom OS but if I stay below I'm ok with factory PCM?
Close... With the custom HPT OS (2bar = atmosphere/NA + 14.7 "boost) is when you max it out at 15psi.... NOT with the factory OS.
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Old Dec 2, 2010 | 04:57 PM
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Originally Posted by Superman09
Did a search and surprisingly came up dry! I remember back when I was more in the FI game that tuning a 98 PCM for boost in 2-3 bar had limitations. What is the deal exactly when working with a 1998? Thanks!
Not sure where you got your info but as far as i am concerned there isn't one, 98 PCM 18 pounds 915 at the rears with out any problems.
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Old Dec 2, 2010 | 05:38 PM
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You can go PE vs RPM if youre on a big blower setup, with the MAF. Max the MAF out, and carry the PE line up the fueling curve. Not the best way to do it, but it gets the job done.

Anything more than that, and its probably a pretty tricky deal.
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Old Dec 3, 2010 | 03:33 AM
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whats it take to re-pin for the newer pcm?
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Old Dec 3, 2010 | 04:09 PM
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You basically have to move almost every wire from the blue connector to the red connector on the two plugs for the pcm. Its a lot of wires to move but its not that hard if you take your time. You will then need a 99+ PCM and also need to do a segment swap in order for your fuel gauge to work right. If you have efi live you can do it your self, if you have hp tuners you have to get them to do it for you.
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Old Dec 5, 2010 | 11:13 AM
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Does anyone here have the info on the pinout information to do this themselves? Also does anyone know a good shop to send the harness to so it can be done for me?
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Old Dec 5, 2010 | 08:23 PM
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Originally Posted by minytrker
You basically have to move almost every wire from the blue connector to the red connector on the two plugs for the pcm. Its a lot of wires to move but its not that hard if you take your time. You will then need a 99+ PCM and also need to do a segment swap in order for your fuel gauge to work right. If you have efi live you can do it your self, if you have hp tuners you have to get them to do it for you.
1. where can I find the diagram to re-pin the wires?
2. Im using HPTuners, can you elaborate on "having them do it for me"?

thanks for the help, ive always heard about this but nobody ever seems to know how to actually do it.
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Old Dec 5, 2010 | 09:21 PM
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Originally Posted by CarsandWomen
1. where can I find the diagram to re-pin the wires?
2. Im using HPTuners, can you elaborate on "having them do it for me"?

thanks for the help, ive always heard about this but nobody ever seems to know how to actually do it.
1. I am not sure where the diagram is online or if it is. I have my own diagram that I made using a 98 and a 99 wiring diagram.

2. I am not sure 100%, just know you have to email and have them do it. I have both efi and hpt so I just use efi and do it myself.
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Old Dec 5, 2010 | 11:07 PM
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Originally Posted by CarsandWomen
1. where can I find the diagram to re-pin the wires?

thanks for the help, ive always heard about this but nobody ever seems to know how to actually do it.
https://ls1tech.com/forums/11049165-post6.html
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Old Dec 6, 2010 | 12:24 AM
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Nice! thanks to you both!
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